diff --git a/src-tauri/Cargo.lock b/src-tauri/Cargo.lock
index 08cffd4..903ab8c 100644
--- a/src-tauri/Cargo.lock
+++ b/src-tauri/Cargo.lock
@@ -761,6 +761,27 @@ dependencies = [
  "syn 2.0.117",
 ]
 
+[[package]]
+name = "dbus"
+version = "0.9.11"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b942602992bb7acfd1f51c49811c58a610ef9181b6e66f3e519d79b540a3bf73"
+dependencies = [
+ "libc",
+ "libdbus-sys",
+ "windows-sys 0.61.2",
+]
+
+[[package]]
+name = "dbus-secret-service"
+version = "4.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "708b509edf7889e53d7efb0ffadd994cc6c2345ccb62f55cfd6b0682165e4fa6"
+dependencies = [
+ "dbus",
+ "zeroize",
+]
+
 [[package]]
 name = "deranged"
 version = "0.5.8"
@@ -1215,6 +1236,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "07bbe89c50d7a535e539b8c17bc0b49bdb77747034daa8087407d655f3f7cc1d"
 dependencies = [
  "futures-core",
+ "futures-sink",
 ]
 
 [[package]]
@@ -1428,8 +1450,10 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "ff2abc00be7fca6ebc474524697ae276ad847ad0a6b3faa4bcb027e9a4614ad0"
 dependencies = [
  "cfg-if",
+ "js-sys",
  "libc",
  "wasi 0.11.1+wasi-snapshot-preview1",
+ "wasm-bindgen",
 ]
 
 [[package]]
@@ -1439,9 +1463,11 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "899def5c37c4fd7b2664648c28120ecec138e4d395b459e5ca34f9cce2dd77fd"
 dependencies = [
  "cfg-if",
+ "js-sys",
  "libc",
  "r-efi 5.3.0",
  "wasip2",
+ "wasm-bindgen",
 ]
 
 [[package]]
@@ -1771,6 +1797,7 @@ dependencies = [
  "tokio",
  "tokio-rustls",
  "tower-service",
+ "webpki-roots",
 ]
 
 [[package]]
@@ -2130,6 +2157,21 @@ dependencies = [
  "unicode-segmentation",
 ]
 
+[[package]]
+name = "keyring"
+version = "3.6.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "eebcc3aff044e5944a8fbaf69eb277d11986064cba30c468730e8b9909fb551c"
+dependencies = [
+ "byteorder",
+ "dbus-secret-service",
+ "log",
+ "security-framework 2.11.1",
+ "security-framework 3.7.0",
+ "windows-sys 0.60.2",
+ "zeroize",
+]
+
 [[package]]
 name = "kuchikiki"
 version = "0.8.8-speedreader"
@@ -2178,6 +2220,15 @@ version = "0.2.184"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "48f5d2a454e16a5ea0f4ced81bd44e4cfc7bd3a507b61887c99fd3538b28e4af"
 
+[[package]]
+name = "libdbus-sys"
+version = "0.2.7"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "328c4789d42200f1eeec05bd86c9c13c7f091d2ba9a6ea35acdf51f31bc0f043"
+dependencies = [
+ "pkg-config",
+]
+
 [[package]]
 name = "libloading"
 version = "0.7.4"
@@ -2261,6 +2312,12 @@ version = "0.4.29"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "5e5032e24019045c762d3c0f28f5b6b8bbf38563a65908389bf7978758920897"
 
+[[package]]
+name = "lru-slab"
+version = "0.1.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "112b39cec0b298b6c1999fee3e31427f74f676e4cb9879ed1a121b43661a4154"
+
 [[package]]
 name = "mac"
 version = "0.1.1"
@@ -3151,6 +3208,61 @@ dependencies = [
  "memchr",
 ]
 
+[[package]]
+name = "quinn"
+version = "0.11.9"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b9e20a958963c291dc322d98411f541009df2ced7b5a4f2bd52337638cfccf20"
+dependencies = [
+ "bytes",
+ "cfg_aliases",
+ "pin-project-lite",
+ "quinn-proto",
+ "quinn-udp",
+ "rustc-hash",
+ "rustls",
+ "socket2",
+ "thiserror 2.0.18",
+ "tokio",
+ "tracing",
+ "web-time",
+]
+
+[[package]]
+name = "quinn-proto"
+version = "0.11.14"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "434b42fec591c96ef50e21e886936e66d3cc3f737104fdb9b737c40ffb94c098"
+dependencies = [
+ "bytes",
+ "getrandom 0.3.4",
+ "lru-slab",
+ "rand 0.9.4",
+ "ring",
+ "rustc-hash",
+ "rustls",
+ "rustls-pki-types",
+ "slab",
+ "thiserror 2.0.18",
+ "tinyvec",
+ "tracing",
+ "web-time",
+]
+
+[[package]]
+name = "quinn-udp"
+version = "0.5.14"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "addec6a0dcad8a8d96a771f815f0eaf55f9d1805756410b39f5fa81332574cbd"
+dependencies = [
+ "cfg_aliases",
+ "libc",
+ "once_cell",
+ "socket2",
+ "tracing",
+ "windows-sys 0.60.2",
+]
+
 [[package]]
 name = "quote"
 version = "1.0.45"
@@ -3197,6 +3309,16 @@ dependencies = [
  "rand_core 0.6.4",
 ]
 
+[[package]]
+name = "rand"
+version = "0.9.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "44c5af06bb1b7d3216d91932aed5265164bf384dc89cd6ba05cf59a35f5f76ea"
+dependencies = [
+ "rand_chacha 0.9.0",
+ "rand_core 0.9.5",
+]
+
 [[package]]
 name = "rand_chacha"
 version = "0.2.2"
@@ -3217,6 +3339,16 @@ dependencies = [
  "rand_core 0.6.4",
 ]
 
+[[package]]
+name = "rand_chacha"
+version = "0.9.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d3022b5f1df60f26e1ffddd6c66e8aa15de382ae63b3a0c1bfc0e4d3e3f325cb"
+dependencies = [
+ "ppv-lite86",
+ "rand_core 0.9.5",
+]
+
 [[package]]
 name = "rand_core"
 version = "0.5.1"
@@ -3235,6 +3367,15 @@ dependencies = [
  "getrandom 0.2.17",
 ]
 
+[[package]]
+name = "rand_core"
+version = "0.9.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "76afc826de14238e6e8c374ddcc1fa19e374fd8dd986b0d2af0d02377261d83c"
+dependencies = [
+ "getrandom 0.3.4",
+]
+
 [[package]]
 name = "rand_hc"
 version = "0.2.0"
@@ -3337,6 +3478,46 @@ version = "0.8.10"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "dc897dd8d9e8bd1ed8cdad82b5966c3e0ecae09fb1907d58efaa013543185d0a"
 
+[[package]]
+name = "reqwest"
+version = "0.12.28"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "eddd3ca559203180a307f12d114c268abf583f59b03cb906fd0b3ff8646c1147"
+dependencies = [
+ "base64 0.22.1",
+ "bytes",
+ "futures-channel",
+ "futures-core",
+ "futures-util",
+ "http",
+ "http-body",
+ "http-body-util",
+ "hyper",
+ "hyper-rustls",
+ "hyper-util",
+ "js-sys",
+ "log",
+ "percent-encoding",
+ "pin-project-lite",
+ "quinn",
+ "rustls",
+ "rustls-pki-types",
+ "serde",
+ "serde_json",
+ "serde_urlencoded",
+ "sync_wrapper",
+ "tokio",
+ "tokio-rustls",
+ "tower",
+ "tower-http",
+ "tower-service",
+ "url",
+ "wasm-bindgen",
+ "wasm-bindgen-futures",
+ "web-sys",
+ "webpki-roots",
+]
+
 [[package]]
 name = "reqwest"
 version = "0.13.2"
@@ -3392,8 +3573,10 @@ dependencies = [
 
 [[package]]
 name = "rudu"
-version = "0.1.6"
+version = "0.1.7"
 dependencies = [
+ "keyring",
+ "reqwest 0.12.28",
  "rusqlite",
  "serde",
  "serde_json",
@@ -3480,7 +3663,7 @@ dependencies = [
  "openssl-probe",
  "rustls-pki-types",
  "schannel",
- "security-framework",
+ "security-framework 3.7.0",
 ]
 
 [[package]]
@@ -3489,6 +3672,7 @@ version = "1.14.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "be040f8b0a225e40375822a563fa9524378b9d63112f53e19ffff34df5d33fdd"
 dependencies = [
+ "web-time",
  "zeroize",
 ]
 
@@ -3507,7 +3691,7 @@ dependencies = [
  "rustls-native-certs",
  "rustls-platform-verifier-android",
  "rustls-webpki",
- "security-framework",
+ "security-framework 3.7.0",
  "security-framework-sys",
  "webpki-root-certs",
  "windows-sys 0.61.2",
@@ -3536,6 +3720,12 @@ version = "1.0.22"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "b39cdef0fa800fc44525c84ccb54a029961a8215f9619753635a9c0d2538d46d"
 
+[[package]]
+name = "ryu"
+version = "1.0.23"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "9774ba4a74de5f7b1c1451ed6cd5285a32eddb5cccb8cc655a4e50009e06477f"
+
 [[package]]
 name = "same-file"
 version = "1.0.6"
@@ -3611,6 +3801,19 @@ version = "1.2.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "94143f37725109f92c262ed2cf5e59bce7498c01bcc1502d7b9afe439a4e9f49"
 
+[[package]]
+name = "security-framework"
+version = "2.11.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "897b2245f0b511c87893af39b033e5ca9cce68824c4d7e7630b5a1d339658d02"
+dependencies = [
+ "bitflags 2.11.0",
+ "core-foundation 0.9.4",
+ "core-foundation-sys",
+ "libc",
+ "security-framework-sys",
+]
+
 [[package]]
 name = "security-framework"
 version = "3.7.0"
@@ -3776,6 +3979,18 @@ dependencies = [
  "serde_core",
 ]
 
+[[package]]
+name = "serde_urlencoded"
+version = "0.7.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d3491c14715ca2294c4d6a88f15e84739788c1d030eed8c110436aafdaa2f3fd"
+dependencies = [
+ "form_urlencoded",
+ "itoa",
+ "ryu",
+ "serde",
+]
+
 [[package]]
 name = "serde_with"
 version = "3.18.0"
@@ -4192,7 +4407,7 @@ dependencies = [
  "percent-encoding",
  "plist",
  "raw-window-handle",
- "reqwest",
+ "reqwest 0.13.2",
  "serde",
  "serde_json",
  "serde_repr",
@@ -4357,7 +4572,7 @@ dependencies = [
  "minisign-verify",
  "osakit",
  "percent-encoding",
- "reqwest",
+ "reqwest 0.13.2",
  "rustls",
  "semver",
  "serde",
@@ -4589,6 +4804,21 @@ dependencies = [
  "zerovec",
 ]
 
+[[package]]
+name = "tinyvec"
+version = "1.11.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "3e61e67053d25a4e82c844e8424039d9745781b3fc4f32b8d55ed50f5f667ef3"
+dependencies = [
+ "tinyvec_macros",
+]
+
+[[package]]
+name = "tinyvec_macros"
+version = "0.1.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "1f3ccbac311fea05f86f61904b462b55fb3df8837a366dfc601a0161d0532f20"
+
 [[package]]
 name = "tokio"
 version = "1.51.1"
@@ -5171,6 +5401,16 @@ dependencies = [
  "wasm-bindgen",
 ]
 
+[[package]]
+name = "web-time"
+version = "1.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5a6580f308b1fad9207618087a65c04e7a10bc77e02c8e84e9b00dd4b12fa0bb"
+dependencies = [
+ "js-sys",
+ "wasm-bindgen",
+]
+
 [[package]]
 name = "web_atoms"
 version = "0.2.3"
@@ -5236,6 +5476,15 @@ dependencies = [
  "rustls-pki-types",
 ]
 
+[[package]]
+name = "webpki-roots"
+version = "1.0.7"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "52f5ee44c96cf55f1b349600768e3ece3a8f26010c05265ab73f945bb1a2eb9d"
+dependencies = [
+ "rustls-pki-types",
+]
+
 [[package]]
 name = "webview2-com"
 version = "0.38.2"
@@ -6118,6 +6367,20 @@ name = "zeroize"
 version = "1.8.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "b97154e67e32c85465826e8bcc1c59429aaaf107c1e4a9e53c8d8ccd5eff88d0"
+dependencies = [
+ "zeroize_derive",
+]
+
+[[package]]
+name = "zeroize_derive"
+version = "1.4.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "85a5b4158499876c763cb03bc4e49185d3cccbabb15b33c627f7884f43db852e"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "syn 2.0.117",
+]
 
 [[package]]
 name = "zerotrie"
diff --git a/src-tauri/Cargo.toml b/src-tauri/Cargo.toml
index 1c394ad..53703c0 100644
--- a/src-tauri/Cargo.toml
+++ b/src-tauri/Cargo.toml
@@ -24,6 +24,8 @@ tauri-plugin-decorum = { git = "https://github.com/clearlysid/tauri-plugin-decor
 serde = { version = "1", features = ["derive"] }
 serde_json = "1"
 rusqlite = { version = "0.31", features = ["bundled"] }
+keyring = { version = "3", features = ["apple-native", "windows-native", "sync-secret-service"] }
+reqwest = { version = "0.12", default-features = false, features = ["blocking", "json", "rustls-tls"] }
 
 [target.'cfg(any(target_os = "macos", windows, target_os = "linux"))'.dependencies]
 tauri-plugin-process = "2.3.1"
diff --git a/src-tauri/src/cache/mod.rs b/src-tauri/src/cache/mod.rs
index 7d5432c..aef01c3 100644
--- a/src-tauri/src/cache/mod.rs
+++ b/src-tauri/src/cache/mod.rs
@@ -4,7 +4,9 @@ use std::sync::OnceLock;
 
 use rusqlite::{params, Connection, OptionalExtension};
 
-use crate::models::{PullRequestCore, PullRequestSummary, RepoSummary};
+use crate::models::{
+    LlmSettings, PullRequestChapters, PullRequestCore, PullRequestSummary, RepoSummary,
+};
 use crate::support::{bool_to_sql, now_unix_timestamp, sql_to_bool};
 
 static CACHE_DB_PATH: OnceLock<PathBuf> = OnceLock::new();
@@ -200,6 +202,27 @@ pub fn initialize_cache_database(path: &Path) -> Result<(), String> {
             PRIMARY KEY (repo_name_with_owner, pr_number, head_sha)
         );
 
+        CREATE TABLE IF NOT EXISTS pr_chapters_cache (
+            repo_name_with_owner TEXT NOT NULL,
+            pr_number INTEGER NOT NULL,
+            head_sha TEXT NOT NULL,
+            prompt_version TEXT NOT NULL,
+            provider TEXT NOT NULL,
+            model TEXT NOT NULL,
+            chapters_json TEXT NOT NULL,
+            cached_at INTEGER NOT NULL,
+            last_accessed_at INTEGER NOT NULL,
+            PRIMARY KEY (repo_name_with_owner, pr_number, head_sha, prompt_version)
+        );
+
+        CREATE TABLE IF NOT EXISTS llm_settings (
+            id INTEGER PRIMARY KEY CHECK (id = 1),
+            provider TEXT NOT NULL,
+            model TEXT NOT NULL,
+            base_url TEXT,
+            updated_at INTEGER NOT NULL
+        );
+
         CREATE TABLE IF NOT EXISTS tracked_pull_requests (
             repo_name_with_owner TEXT NOT NULL,
             pr_number INTEGER NOT NULL,
@@ -511,6 +534,152 @@ pub fn store_changed_files(
     Ok(())
 }
 
+pub fn read_cached_pull_request_chapters(
+    repo: &str,
+    number: u32,
+    head_sha: &str,
+    prompt_version: &str,
+) -> Result<Option<PullRequestChapters>, String> {
+    let conn = open_cache_connection()?;
+    let chapters_json = conn
+        .query_row(
+            "
+            SELECT chapters_json
+            FROM pr_chapters_cache
+            WHERE repo_name_with_owner = ?1
+              AND pr_number = ?2
+              AND head_sha = ?3
+              AND prompt_version = ?4
+            ",
+            params![repo, number, head_sha, prompt_version],
+            |row| row.get::<_, String>(0),
+        )
+        .optional()
+        .map_err(|error| format!("Failed to query cached PR chapters: {error}"))?;
+
+    let Some(chapters_json) = chapters_json else {
+        return Ok(None);
+    };
+
+    conn.execute(
+        "
+        UPDATE pr_chapters_cache
+        SET last_accessed_at = ?5
+        WHERE repo_name_with_owner = ?1
+          AND pr_number = ?2
+          AND head_sha = ?3
+          AND prompt_version = ?4
+        ",
+        params![repo, number, head_sha, prompt_version, now_unix_timestamp()],
+    )
+    .map_err(|error| format!("Failed to update PR chapters cache access time: {error}"))?;
+
+    let chapters = serde_json::from_str::<PullRequestChapters>(&chapters_json)
+        .map_err(|error| format!("Failed to parse cached PR chapters: {error}"))?;
+
+    Ok(Some(chapters))
+}
+
+pub fn store_pull_request_chapters(chapters: &PullRequestChapters) -> Result<(), String> {
+    let conn = open_cache_connection()?;
+    let chapters_json = serde_json::to_string(chapters)
+        .map_err(|error| format!("Failed to serialize PR chapters for cache: {error}"))?;
+    let timestamp = now_unix_timestamp();
+
+    conn.execute(
+        "
+        INSERT INTO pr_chapters_cache (
+            repo_name_with_owner,
+            pr_number,
+            head_sha,
+            prompt_version,
+            provider,
+            model,
+            chapters_json,
+            cached_at,
+            last_accessed_at
+        )
+        VALUES (?1, ?2, ?3, ?4, ?5, ?6, ?7, ?8, ?8)
+        ON CONFLICT(repo_name_with_owner, pr_number, head_sha, prompt_version)
+        DO UPDATE SET
+            provider = excluded.provider,
+            model = excluded.model,
+            chapters_json = excluded.chapters_json,
+            cached_at = excluded.cached_at,
+            last_accessed_at = excluded.last_accessed_at
+        ",
+        params![
+            &chapters.repo,
+            chapters.number,
+            &chapters.head_sha,
+            &chapters.prompt_version,
+            &chapters.provider,
+            &chapters.model,
+            chapters_json,
+            timestamp,
+        ],
+    )
+    .map_err(|error| format!("Failed to persist PR chapters cache: {error}"))?;
+
+    Ok(())
+}
+
+pub fn read_llm_settings() -> Result<Option<LlmSettings>, String> {
+    let conn = open_cache_connection()?;
+    let settings = conn
+        .query_row(
+            "
+            SELECT provider, model, base_url
+            FROM llm_settings
+            WHERE id = 1
+            ",
+            [],
+            |row| {
+                Ok(LlmSettings {
+                    provider: row.get(0)?,
+                    model: row.get(1)?,
+                    base_url: row.get(2)?,
+                    has_api_key: false,
+                })
+            },
+        )
+        .optional()
+        .map_err(|error| format!("Failed to read LLM settings: {error}"))?;
+
+    Ok(settings)
+}
+
+pub fn write_llm_settings(settings: &LlmSettings) -> Result<(), String> {
+    let conn = open_cache_connection()?;
+    conn.execute(
+        "
+        INSERT INTO llm_settings (
+            id,
+            provider,
+            model,
+            base_url,
+            updated_at
+        )
+        VALUES (1, ?1, ?2, ?3, ?4)
+        ON CONFLICT(id)
+        DO UPDATE SET
+            provider = excluded.provider,
+            model = excluded.model,
+            base_url = excluded.base_url,
+            updated_at = excluded.updated_at
+        ",
+        params![
+            &settings.provider,
+            &settings.model,
+            &settings.base_url,
+            now_unix_timestamp(),
+        ],
+    )
+    .map_err(|error| format!("Failed to persist LLM settings: {error}"))?;
+
+    Ok(())
+}
+
 pub fn update_repo_access_timestamp(repo: &str) -> Result<(), String> {
     let conn = open_cache_connection()?;
     conn.execute(
diff --git a/src-tauri/src/commands/chapters.rs b/src-tauri/src/commands/chapters.rs
new file mode 100644
index 0000000..1055fff
--- /dev/null
+++ b/src-tauri/src/commands/chapters.rs
@@ -0,0 +1,72 @@
+use crate::models::{LlmProviderInfo, LlmSettings, PullRequestChapters, SaveLlmSettingsInput};
+use crate::services::{chapters, llm};
+
+async fn run_blocking_task<T, F>(task: F) -> Result<T, String>
+where
+    T: Send + 'static,
+    F: FnOnce() -> Result<T, String> + Send + 'static,
+{
+    tauri::async_runtime::spawn_blocking(task)
+        .await
+        .map_err(|error| format!("Blocking task failed: {error}"))?
+}
+
+#[tauri::command]
+pub fn list_llm_providers() -> Vec<LlmProviderInfo> {
+    llm::list_provider_infos()
+}
+
+#[tauri::command]
+pub async fn get_llm_settings() -> Result<LlmSettings, String> {
+    run_blocking_task(llm::load_llm_settings).await
+}
+
+#[tauri::command]
+pub async fn save_llm_settings(settings: SaveLlmSettingsInput) -> Result<LlmSettings, String> {
+    run_blocking_task(move || llm::save_llm_settings(settings)).await
+}
+
+#[tauri::command]
+pub async fn set_llm_api_key(provider: String, api_key: String) -> Result<LlmSettings, String> {
+    run_blocking_task(move || {
+        llm::save_api_key(&provider, &api_key)?;
+        llm::load_llm_settings()
+    })
+    .await
+}
+
+#[tauri::command]
+pub async fn delete_llm_api_key(provider: String) -> Result<LlmSettings, String> {
+    run_blocking_task(move || {
+        llm::delete_api_key(&provider)?;
+        llm::load_llm_settings()
+    })
+    .await
+}
+
+#[tauri::command]
+pub async fn test_llm_provider() -> Result<(), String> {
+    run_blocking_task(|| {
+        let settings = llm::load_llm_settings()?;
+        llm::test_llm_provider(&settings)
+    })
+    .await
+}
+
+#[tauri::command]
+pub async fn get_pull_request_chapters(
+    repo: String,
+    number: u32,
+    head_sha: String,
+) -> Result<Option<PullRequestChapters>, String> {
+    run_blocking_task(move || chapters::read_cached_chapters(repo, number, head_sha)).await
+}
+
+#[tauri::command]
+pub async fn regenerate_pull_request_chapters(
+    repo: String,
+    number: u32,
+    head_sha: String,
+) -> Result<PullRequestChapters, String> {
+    run_blocking_task(move || chapters::generate_chapters(repo, number, head_sha)).await
+}
diff --git a/src-tauri/src/commands/mod.rs b/src-tauri/src/commands/mod.rs
index e4e67f7..2869092 100644
--- a/src-tauri/src/commands/mod.rs
+++ b/src-tauri/src/commands/mod.rs
@@ -1,5 +1,6 @@
-pub mod pull_requests;
+pub mod chapters;
 pub mod preflight;
+pub mod pull_requests;
 pub mod repos;
 pub mod review_comments;
 pub mod tracked_pull_requests;
diff --git a/src-tauri/src/lib.rs b/src-tauri/src/lib.rs
index 6599c22..61431c9 100644
--- a/src-tauri/src/lib.rs
+++ b/src-tauri/src/lib.rs
@@ -26,6 +26,14 @@ pub fn run() {
             commands::repos::validate_repo,
             commands::repos::list_saved_repos,
             commands::repos::save_repo,
+            commands::chapters::list_llm_providers,
+            commands::chapters::get_llm_settings,
+            commands::chapters::save_llm_settings,
+            commands::chapters::set_llm_api_key,
+            commands::chapters::delete_llm_api_key,
+            commands::chapters::test_llm_provider,
+            commands::chapters::get_pull_request_chapters,
+            commands::chapters::regenerate_pull_request_chapters,
             commands::preflight::get_gh_cli_status,
             commands::pull_requests::list_cached_pull_requests,
             commands::pull_requests::list_pull_requests,
diff --git a/src-tauri/src/models/mod.rs b/src-tauri/src/models/mod.rs
index f03065e..b645620 100644
--- a/src-tauri/src/models/mod.rs
+++ b/src-tauri/src/models/mod.rs
@@ -82,6 +82,102 @@ pub struct PrPatch {
     pub patch: String,
 }
 
+#[derive(Debug, Serialize, Deserialize, Clone)]
+#[serde(rename_all = "camelCase")]
+pub struct LlmProviderInfo {
+    pub id: String,
+    pub name: String,
+    pub adapter: String,
+    pub default_model: String,
+    pub default_base_url: Option<String>,
+    pub base_url_required: bool,
+}
+
+#[derive(Debug, Serialize, Deserialize, Clone)]
+#[serde(rename_all = "camelCase")]
+pub struct LlmSettings {
+    pub provider: String,
+    pub model: String,
+    pub base_url: Option<String>,
+    pub has_api_key: bool,
+}
+
+#[derive(Debug, Deserialize, Clone)]
+#[serde(rename_all = "camelCase")]
+pub struct SaveLlmSettingsInput {
+    pub provider: String,
+    pub model: String,
+    pub base_url: Option<String>,
+}
+
+#[derive(Debug, Serialize, Deserialize, Clone)]
+#[serde(rename_all = "camelCase")]
+pub struct ChapterKeyChange {
+    pub title: String,
+    pub detail: String,
+}
+
+#[derive(Debug, Serialize, Deserialize, Clone)]
+#[serde(rename_all = "camelCase")]
+pub struct ChapterReviewFocus {
+    pub title: String,
+    pub detail: String,
+    pub path: Option<String>,
+    pub severity: Option<String>,
+}
+
+#[derive(Debug, Serialize, Deserialize, Clone)]
+#[serde(rename_all = "camelCase")]
+pub struct ChapterPrologue {
+    pub summary: String,
+    pub key_changes: Vec<ChapterKeyChange>,
+    pub review_focus: Vec<ChapterReviewFocus>,
+}
+
+#[derive(Debug, Serialize, Deserialize, Clone)]
+#[serde(rename_all = "camelCase")]
+pub struct PullRequestChapterFile {
+    pub path: String,
+    pub reason: String,
+    pub additions: u32,
+    pub deletions: u32,
+}
+
+#[derive(Debug, Serialize, Deserialize, Clone)]
+#[serde(rename_all = "camelCase")]
+pub struct ChapterReviewStep {
+    pub title: String,
+    pub detail: String,
+    pub files: Vec<String>,
+}
+
+#[derive(Debug, Serialize, Deserialize, Clone)]
+#[serde(rename_all = "camelCase")]
+pub struct PullRequestChapter {
+    pub id: String,
+    pub title: String,
+    pub summary: String,
+    pub files: Vec<PullRequestChapterFile>,
+    pub review_steps: Vec<ChapterReviewStep>,
+    pub risks: Vec<ChapterReviewFocus>,
+    pub additions: u32,
+    pub deletions: u32,
+}
+
+#[derive(Debug, Serialize, Deserialize, Clone)]
+#[serde(rename_all = "camelCase")]
+pub struct PullRequestChapters {
+    pub repo: String,
+    pub number: u32,
+    pub head_sha: String,
+    pub provider: String,
+    pub model: String,
+    pub prompt_version: String,
+    pub generated_at: i64,
+    pub prologue: ChapterPrologue,
+    pub chapters: Vec<PullRequestChapter>,
+}
+
 #[derive(Debug, Serialize)]
 #[serde(rename_all = "camelCase")]
 pub struct ReviewComment {
diff --git a/src-tauri/src/services/chapters.rs b/src-tauri/src/services/chapters.rs
new file mode 100644
index 0000000..7c037a8
--- /dev/null
+++ b/src-tauri/src/services/chapters.rs
@@ -0,0 +1,705 @@
+use std::collections::{HashMap, HashSet};
+
+use serde::Deserialize;
+
+use crate::cache::{read_cached_pull_request_chapters, store_pull_request_chapters};
+use crate::models::{
+    ChapterKeyChange, ChapterPrologue, ChapterReviewFocus, ChapterReviewStep, LlmSettings,
+    PullRequestChapter, PullRequestChapterFile, PullRequestChapters,
+};
+use crate::services::diff_data::{DiffDataRequest, DiffDataService, GhDiffSource, SqliteDiffCache};
+use crate::services::llm::{complete_json, load_llm_settings, parse_json_response};
+use crate::support::now_unix_timestamp;
+
+pub const CHAPTER_PROMPT_VERSION: &str = "chapters-v1";
+
+const MAX_PATCH_CHARS: usize = 120_000;
+const MAX_CHAPTERS: usize = 8;
+
+#[derive(Debug, Clone)]
+struct FileStat {
+    path: String,
+    additions: u32,
+    deletions: u32,
+}
+
+#[derive(Debug, Deserialize)]
+#[serde(rename_all = "camelCase")]
+struct RawChapterResponse {
+    prologue: Option<RawPrologue>,
+    chapters: Option<Vec<RawChapter>>,
+}
+
+#[derive(Debug, Deserialize)]
+#[serde(untagged)]
+enum RawPrologue {
+    Object(RawPrologueObject),
+    Summary(String),
+}
+
+#[derive(Debug, Deserialize)]
+#[serde(rename_all = "camelCase")]
+struct RawPrologueObject {
+    summary: Option<String>,
+    #[serde(alias = "key_changes")]
+    key_changes: Option<Vec<RawTextItem>>,
+    #[serde(alias = "review_focus")]
+    review_focus: Option<Vec<RawFocusItem>>,
+}
+
+#[derive(Debug, Deserialize)]
+#[serde(untagged)]
+enum RawTextItem {
+    Object(RawTextItemObject),
+    Text(String),
+}
+
+#[derive(Debug, Deserialize)]
+#[serde(rename_all = "camelCase")]
+struct RawTextItemObject {
+    title: Option<String>,
+    #[serde(alias = "description")]
+    detail: Option<String>,
+}
+
+#[derive(Debug, Deserialize)]
+#[serde(untagged)]
+enum RawFocusItem {
+    Object(RawFocusItemObject),
+    Text(String),
+}
+
+#[derive(Debug, Deserialize)]
+#[serde(rename_all = "camelCase")]
+struct RawFocusItemObject {
+    title: Option<String>,
+    #[serde(alias = "description")]
+    detail: Option<String>,
+    path: Option<String>,
+    severity: Option<String>,
+}
+
+#[derive(Debug, Deserialize)]
+#[serde(rename_all = "camelCase")]
+struct RawChapter {
+    title: Option<String>,
+    summary: Option<String>,
+    files: Option<Vec<RawChapterFile>>,
+    #[serde(alias = "review_steps")]
+    review_steps: Option<Vec<RawReviewStep>>,
+    risks: Option<Vec<RawFocusItem>>,
+}
+
+#[derive(Debug, Deserialize)]
+#[serde(untagged)]
+enum RawChapterFile {
+    Object(RawChapterFileObject),
+    Path(String),
+}
+
+#[derive(Debug, Deserialize)]
+#[serde(rename_all = "camelCase")]
+struct RawChapterFileObject {
+    path: Option<String>,
+    #[serde(alias = "detail")]
+    reason: Option<String>,
+}
+
+#[derive(Debug, Deserialize)]
+#[serde(untagged)]
+enum RawReviewStep {
+    Object(RawReviewStepObject),
+    Text(String),
+}
+
+#[derive(Debug, Deserialize)]
+#[serde(rename_all = "camelCase")]
+struct RawReviewStepObject {
+    title: Option<String>,
+    #[serde(alias = "description")]
+    detail: Option<String>,
+    files: Option<Vec<String>>,
+}
+
+fn normalize_path(path: &str) -> String {
+    path.trim()
+        .trim_start_matches("a/")
+        .trim_start_matches("b/")
+        .to_string()
+}
+
+fn trim_text(value: Option<String>) -> String {
+    value.unwrap_or_default().trim().to_string()
+}
+
+fn parse_diff_path(line: &str) -> Option<String> {
+    if !line.starts_with("diff --git ") {
+        return None;
+    }
+
+    let mut parts = line.split_whitespace();
+    parts.next()?;
+    parts.next()?;
+    let _left = parts.next()?;
+    let right = parts.next()?;
+
+    Some(normalize_path(right))
+}
+
+fn build_file_stats(changed_files: &[String], patch: &str) -> HashMap<String, FileStat> {
+    let mut stats = HashMap::new();
+    for path in changed_files {
+        let normalized = normalize_path(path);
+        stats.insert(
+            normalized.clone(),
+            FileStat {
+                path: normalized,
+                additions: 0,
+                deletions: 0,
+            },
+        );
+    }
+
+    let mut current_path: Option<String> = None;
+    for line in patch.lines() {
+        if let Some(path) = parse_diff_path(line) {
+            current_path = Some(path);
+            continue;
+        }
+
+        let Some(path) = current_path.as_ref() else {
+            continue;
+        };
+        let Some(stat) = stats.get_mut(path) else {
+            continue;
+        };
+
+        if line.starts_with('+') && !line.starts_with("+++") {
+            stat.additions = stat.additions.saturating_add(1);
+        } else if line.starts_with('-') && !line.starts_with("---") {
+            stat.deletions = stat.deletions.saturating_add(1);
+        }
+    }
+
+    stats
+}
+
+fn clipped_patch(patch: &str) -> (String, bool) {
+    if patch.len() <= MAX_PATCH_CHARS {
+        return (patch.to_string(), false);
+    }
+
+    let mut end = MAX_PATCH_CHARS;
+    while !patch.is_char_boundary(end) {
+        end -= 1;
+    }
+
+    (patch[..end].to_string(), true)
+}
+
+fn system_prompt() -> &'static str {
+    r#"You generate pull request review chapters for experienced engineers.
+Return only strict JSON. Do not use markdown fences.
+Group related files into reviewable chapters that reduce noise.
+Every cited file path must come from the changed file list supplied by the user.
+Prefer concrete review steps over generic advice.
+
+Required JSON shape:
+{
+  "prologue": {
+    "summary": "One concise paragraph explaining the story of the PR.",
+    "keyChanges": [
+      { "title": "Short change title", "detail": "Specific natural-language explanation." }
+    ],
+    "reviewFocus": [
+      { "title": "Risk or review focus", "detail": "Why it matters.", "path": "optional/file/path", "severity": "low|medium|high" }
+    ]
+  },
+  "chapters": [
+    {
+      "title": "Chapter title",
+      "summary": "What changed and why this chapter should be reviewed together.",
+      "files": [
+        { "path": "changed/file/path", "reason": "Why this file belongs here." }
+      ],
+      "reviewSteps": [
+        { "title": "Review step", "detail": "Specific action for the reviewer.", "files": ["changed/file/path"] }
+      ],
+      "risks": [
+        { "title": "Risk", "detail": "What could break.", "path": "optional/file/path", "severity": "low|medium|high" }
+      ]
+    }
+  ]
+}"#
+}
+
+fn user_prompt(
+    repo: &str,
+    number: u32,
+    head_sha: &str,
+    file_stats: &HashMap<String, FileStat>,
+    patch: &str,
+) -> Result<String, String> {
+    let mut files = file_stats.values().collect::<Vec<_>>();
+    files.sort_by(|a, b| a.path.cmp(&b.path));
+
+    let files_json = serde_json::to_string_pretty(
+        &files
+            .iter()
+            .map(|stat| {
+                serde_json::json!({
+                    "path": &stat.path,
+                    "additions": stat.additions,
+                    "deletions": stat.deletions,
+                })
+            })
+            .collect::<Vec<_>>(),
+    )
+    .map_err(|error| format!("Failed to serialize changed files for prompt: {error}"))?;
+
+    let (patch, was_clipped) = clipped_patch(patch);
+    let clipping_note = if was_clipped {
+        "The patch was clipped for model context. Prefer chapter grouping from the changed file list when later hunks are absent."
+    } else {
+        "The full patch is included."
+    };
+
+    Ok(format!(
+        r#"Repository: {repo}
+Pull request: #{number}
+Head SHA: {head_sha}
+Prompt version: {CHAPTER_PROMPT_VERSION}
+Patch note: {clipping_note}
+
+Changed files with line stats:
+{files_json}
+
+Unified diff:
+```diff
+{patch}
+```"#
+    ))
+}
+
+fn known_path<'a>(
+    path: Option<String>,
+    file_stats: &'a HashMap<String, FileStat>,
+) -> Option<&'a FileStat> {
+    let path = path?;
+    let path = normalize_path(&path);
+    file_stats.get(&path)
+}
+
+fn known_path_string(path: String, known_paths: &HashSet<String>) -> Option<String> {
+    let path = normalize_path(&path);
+    if known_paths.contains(&path) {
+        Some(path)
+    } else {
+        None
+    }
+}
+
+fn normalize_focus_items(
+    items: Option<Vec<RawFocusItem>>,
+    file_stats: &HashMap<String, FileStat>,
+) -> Vec<ChapterReviewFocus> {
+    let known_paths = file_stats.keys().cloned().collect::<HashSet<_>>();
+
+    items
+        .unwrap_or_default()
+        .into_iter()
+        .filter_map(|item| {
+            let (title, detail, path, severity) = match item {
+                RawFocusItem::Object(item) => (
+                    trim_text(item.title),
+                    trim_text(item.detail),
+                    item.path,
+                    item.severity,
+                ),
+                RawFocusItem::Text(detail) => {
+                    (String::new(), detail.trim().to_string(), None, None)
+                }
+            };
+            if title.is_empty() && detail.is_empty() {
+                return None;
+            }
+
+            Some(ChapterReviewFocus {
+                title: if title.is_empty() {
+                    "Review focus".into()
+                } else {
+                    title
+                },
+                detail,
+                path: path.and_then(|path| known_path_string(path, &known_paths)),
+                severity: severity
+                    .map(|severity| severity.trim().to_ascii_lowercase())
+                    .filter(|severity| matches!(severity.as_str(), "low" | "medium" | "high")),
+            })
+        })
+        .take(6)
+        .collect()
+}
+
+fn normalize_key_changes(items: Option<Vec<RawTextItem>>) -> Vec<ChapterKeyChange> {
+    items
+        .unwrap_or_default()
+        .into_iter()
+        .filter_map(|item| {
+            let (title, detail) = match item {
+                RawTextItem::Object(item) => (trim_text(item.title), trim_text(item.detail)),
+                RawTextItem::Text(detail) => (String::new(), detail.trim().to_string()),
+            };
+            if title.is_empty() && detail.is_empty() {
+                return None;
+            }
+
+            Some(ChapterKeyChange {
+                title: if title.is_empty() {
+                    "Change".into()
+                } else {
+                    title
+                },
+                detail,
+            })
+        })
+        .take(6)
+        .collect()
+}
+
+fn normalize_review_steps(
+    steps: Option<Vec<RawReviewStep>>,
+    known_paths: &HashSet<String>,
+) -> Vec<ChapterReviewStep> {
+    steps
+        .unwrap_or_default()
+        .into_iter()
+        .filter_map(|step| {
+            let (title, detail, files) = match step {
+                RawReviewStep::Object(step) => (
+                    trim_text(step.title),
+                    trim_text(step.detail),
+                    step.files.unwrap_or_default(),
+                ),
+                RawReviewStep::Text(detail) => {
+                    (String::new(), detail.trim().to_string(), Vec::new())
+                }
+            };
+            if title.is_empty() && detail.is_empty() {
+                return None;
+            }
+
+            let files = files
+                .into_iter()
+                .filter_map(|path| known_path_string(path, known_paths))
+                .collect::<Vec<_>>();
+
+            Some(ChapterReviewStep {
+                title: if title.is_empty() {
+                    "Review step".into()
+                } else {
+                    title
+                },
+                detail,
+                files,
+            })
+        })
+        .take(6)
+        .collect()
+}
+
+fn fallback_prologue(file_stats: &HashMap<String, FileStat>) -> ChapterPrologue {
+    let additions = file_stats.values().map(|stat| stat.additions).sum::<u32>();
+    let deletions = file_stats.values().map(|stat| stat.deletions).sum::<u32>();
+
+    ChapterPrologue {
+        summary: format!(
+            "This pull request changes {} files with +{} / -{} lines. Generate chapters to group the diff into a review sequence.",
+            file_stats.len(),
+            additions,
+            deletions
+        ),
+        key_changes: vec![ChapterKeyChange {
+            title: "Changed files collected".into(),
+            detail: "Rudu loaded the PR patch and file list; no model-authored grouping was available.".into(),
+        }],
+        review_focus: Vec::new(),
+    }
+}
+
+fn fallback_chapter(id: String, title: String, files: Vec<FileStat>) -> PullRequestChapter {
+    let additions = files.iter().map(|stat| stat.additions).sum::<u32>();
+    let deletions = files.iter().map(|stat| stat.deletions).sum::<u32>();
+
+    PullRequestChapter {
+        id,
+        title,
+        summary: "Review these changed files together because they were not assigned to a more specific chapter.".into(),
+        files: files
+            .into_iter()
+            .map(|stat| PullRequestChapterFile {
+                path: stat.path,
+                reason: "Unassigned changed file.".into(),
+                additions: stat.additions,
+                deletions: stat.deletions,
+            })
+            .collect(),
+        review_steps: vec![ChapterReviewStep {
+            title: "Scan changed files".into(),
+            detail: "Check the diff for intent, missing tests, and interactions with the rest of the PR.".into(),
+            files: Vec::new(),
+        }],
+        risks: Vec::new(),
+        additions,
+        deletions,
+    }
+}
+
+fn normalize_prologue(
+    raw: Option<RawPrologue>,
+    file_stats: &HashMap<String, FileStat>,
+) -> ChapterPrologue {
+    raw.map(|prologue| match prologue {
+        RawPrologue::Object(prologue) => ChapterPrologue {
+            summary: trim_text(prologue.summary),
+            key_changes: normalize_key_changes(prologue.key_changes),
+            review_focus: normalize_focus_items(prologue.review_focus, file_stats),
+        },
+        RawPrologue::Summary(summary) => ChapterPrologue {
+            summary: summary.trim().to_string(),
+            key_changes: Vec::new(),
+            review_focus: Vec::new(),
+        },
+    })
+    .filter(|prologue| {
+        !prologue.summary.is_empty()
+            || !prologue.key_changes.is_empty()
+            || !prologue.review_focus.is_empty()
+    })
+    .unwrap_or_else(|| fallback_prologue(file_stats))
+}
+
+fn normalize_chapters(
+    raw: RawChapterResponse,
+    file_stats: &HashMap<String, FileStat>,
+    repo: String,
+    number: u32,
+    head_sha: String,
+    settings: &LlmSettings,
+) -> PullRequestChapters {
+    let prologue = normalize_prologue(raw.prologue, file_stats);
+
+    let known_paths = file_stats.keys().cloned().collect::<HashSet<_>>();
+    let mut assigned_paths = HashSet::new();
+    let mut chapters = Vec::new();
+
+    for raw_chapter in raw
+        .chapters
+        .unwrap_or_default()
+        .into_iter()
+        .take(MAX_CHAPTERS)
+    {
+        let mut chapter_files = Vec::new();
+        let mut chapter_file_paths = HashSet::new();
+
+        for raw_file in raw_chapter.files.unwrap_or_default() {
+            let (path, reason) = match raw_file {
+                RawChapterFile::Object(file) => (file.path, trim_text(file.reason)),
+                RawChapterFile::Path(path) => (Some(path), String::new()),
+            };
+
+            let Some(stat) = known_path(path, file_stats) else {
+                continue;
+            };
+            if !chapter_file_paths.insert(stat.path.clone()) {
+                continue;
+            }
+
+            assigned_paths.insert(stat.path.clone());
+            chapter_files.push(PullRequestChapterFile {
+                path: stat.path.clone(),
+                reason,
+                additions: stat.additions,
+                deletions: stat.deletions,
+            });
+        }
+
+        if chapter_files.is_empty() {
+            continue;
+        }
+
+        let additions = chapter_files.iter().map(|file| file.additions).sum::<u32>();
+        let deletions = chapter_files.iter().map(|file| file.deletions).sum::<u32>();
+        let title = trim_text(raw_chapter.title);
+        let chapter_id = format!("chapter-{}", chapters.len() + 1);
+
+        chapters.push(PullRequestChapter {
+            id: chapter_id,
+            title: if title.is_empty() {
+                format!("Chapter {}", chapters.len() + 1)
+            } else {
+                title
+            },
+            summary: trim_text(raw_chapter.summary),
+            files: chapter_files,
+            review_steps: normalize_review_steps(raw_chapter.review_steps, &known_paths),
+            risks: normalize_focus_items(raw_chapter.risks, file_stats),
+            additions,
+            deletions,
+        });
+    }
+
+    let unassigned = file_stats
+        .values()
+        .filter(|stat| !assigned_paths.contains(&stat.path))
+        .cloned()
+        .collect::<Vec<_>>();
+
+    if !unassigned.is_empty() {
+        chapters.push(fallback_chapter(
+            format!("chapter-{}", chapters.len() + 1),
+            if chapters.is_empty() {
+                "Review changed files".into()
+            } else {
+                "Other changes".into()
+            },
+            unassigned,
+        ));
+    }
+
+    PullRequestChapters {
+        repo,
+        number,
+        head_sha,
+        provider: settings.provider.clone(),
+        model: settings.model.clone(),
+        prompt_version: CHAPTER_PROMPT_VERSION.into(),
+        generated_at: now_unix_timestamp(),
+        prologue,
+        chapters,
+    }
+}
+
+pub fn read_cached_chapters(
+    repo: String,
+    number: u32,
+    head_sha: String,
+) -> Result<Option<PullRequestChapters>, String> {
+    let req = DiffDataRequest::new(repo, number, head_sha)?;
+    read_cached_pull_request_chapters(&req.repo, req.number, &req.head_sha, CHAPTER_PROMPT_VERSION)
+}
+
+pub fn generate_chapters(
+    repo: String,
+    number: u32,
+    head_sha: String,
+) -> Result<PullRequestChapters, String> {
+    let req = DiffDataRequest::new(repo, number, head_sha)?;
+    let diff_service = DiffDataService::new(&GhDiffSource, &SqliteDiffCache);
+    let patch = diff_service.get_patch(&req)?;
+    let changed_files = diff_service.get_changed_files(&req)?;
+
+    if changed_files.is_empty() {
+        return Err("This pull request has no changed files to chapter.".into());
+    }
+
+    let file_stats = build_file_stats(&changed_files, &patch.patch);
+    let settings = load_llm_settings()?;
+    if !settings.has_api_key {
+        return Err("Configure an LLM provider API key before summarizing with AI.".into());
+    }
+
+    let prompt = user_prompt(
+        &req.repo,
+        req.number,
+        &req.head_sha,
+        &file_stats,
+        &patch.patch,
+    )?;
+    let response = complete_json(&settings, system_prompt(), &prompt, 5000)?;
+    let value = parse_json_response(&response)?;
+    let raw = serde_json::from_value::<RawChapterResponse>(value).map_err(|error| {
+        format!("LLM chapter response did not match the expected shape: {error}")
+    })?;
+
+    let chapters = normalize_chapters(
+        raw,
+        &file_stats,
+        req.repo,
+        req.number,
+        req.head_sha,
+        &settings,
+    );
+    store_pull_request_chapters(&chapters)?;
+
+    Ok(chapters)
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use serde_json::json;
+
+    fn test_settings() -> LlmSettings {
+        LlmSettings {
+            provider: "openai".into(),
+            model: "test-model".into(),
+            base_url: None,
+            has_api_key: true,
+        }
+    }
+
+    fn test_file_stats() -> HashMap<String, FileStat> {
+        let mut stats = HashMap::new();
+        stats.insert(
+            "src/lib.rs".into(),
+            FileStat {
+                path: "src/lib.rs".into(),
+                additions: 12,
+                deletions: 3,
+            },
+        );
+        stats
+    }
+
+    #[test]
+    fn normalizes_string_prologue_response() {
+        let raw = serde_json::from_value::<RawChapterResponse>(json!({
+            "prologue": "This PR introduces a multi-agent orchestration skill.",
+            "chapters": [
+                {
+                    "title": "Review orchestration",
+                    "summary": "Adds a workflow for reviewing large PRs.",
+                    "files": ["src/lib.rs"],
+                    "reviewSteps": ["Confirm generated review plans cite changed files."],
+                    "risks": ["The workflow could group unrelated changes together."]
+                }
+            ]
+        }))
+        .expect("string prologue responses should parse");
+
+        let chapters = normalize_chapters(
+            raw,
+            &test_file_stats(),
+            "owner/repo".into(),
+            42,
+            "abc123".into(),
+            &test_settings(),
+        );
+
+        assert_eq!(
+            chapters.prologue.summary,
+            "This PR introduces a multi-agent orchestration skill."
+        );
+        assert_eq!(chapters.chapters.len(), 1);
+        assert_eq!(chapters.chapters[0].files[0].path, "src/lib.rs");
+        assert_eq!(
+            chapters.chapters[0].review_steps[0].detail,
+            "Confirm generated review plans cite changed files."
+        );
+        assert_eq!(
+            chapters.chapters[0].risks[0].detail,
+            "The workflow could group unrelated changes together."
+        );
+    }
+}
diff --git a/src-tauri/src/services/llm.rs b/src-tauri/src/services/llm.rs
new file mode 100644
index 0000000..63eda15
--- /dev/null
+++ b/src-tauri/src/services/llm.rs
@@ -0,0 +1,525 @@
+use keyring::{Entry, Error as KeyringError};
+use reqwest::blocking::Client;
+use serde::Deserialize;
+use serde_json::{json, Value};
+use std::time::Duration;
+
+use crate::cache::{read_llm_settings, write_llm_settings};
+use crate::models::{LlmProviderInfo, LlmSettings, SaveLlmSettingsInput};
+
+const KEYCHAIN_SERVICE: &str = "rudu.llm";
+
+#[derive(Clone, Copy)]
+enum LlmAdapter {
+    OpenAiCompatible,
+    Anthropic,
+    Google,
+}
+
+struct ProviderSpec {
+    id: &'static str,
+    name: &'static str,
+    adapter: LlmAdapter,
+    default_model: &'static str,
+    default_base_url: Option<&'static str>,
+    base_url_required: bool,
+}
+
+struct LlmRuntimeSettings {
+    provider: String,
+    adapter: LlmAdapter,
+    model: String,
+    base_url: Option<String>,
+    api_key: String,
+}
+
+const PROVIDERS: &[ProviderSpec] = &[
+    ProviderSpec {
+        id: "openai",
+        name: "OpenAI",
+        adapter: LlmAdapter::OpenAiCompatible,
+        default_model: "gpt-4.1-mini",
+        default_base_url: Some("https://api.openai.com/v1"),
+        base_url_required: false,
+    },
+    ProviderSpec {
+        id: "anthropic",
+        name: "Anthropic",
+        adapter: LlmAdapter::Anthropic,
+        default_model: "claude-sonnet-4-5",
+        default_base_url: Some("https://api.anthropic.com"),
+        base_url_required: false,
+    },
+    ProviderSpec {
+        id: "google",
+        name: "Google",
+        adapter: LlmAdapter::Google,
+        default_model: "gemini-2.5-flash",
+        default_base_url: Some("https://generativelanguage.googleapis.com/v1beta"),
+        base_url_required: false,
+    },
+    ProviderSpec {
+        id: "openrouter",
+        name: "OpenRouter",
+        adapter: LlmAdapter::OpenAiCompatible,
+        default_model: "openai/gpt-4.1-mini",
+        default_base_url: Some("https://openrouter.ai/api/v1"),
+        base_url_required: false,
+    },
+    ProviderSpec {
+        id: "zai",
+        name: "Z.ai",
+        adapter: LlmAdapter::OpenAiCompatible,
+        default_model: "glm-4.5",
+        default_base_url: Some("https://open.bigmodel.cn/api/paas/v4"),
+        base_url_required: false,
+    },
+    ProviderSpec {
+        id: "minimax",
+        name: "Minimax",
+        adapter: LlmAdapter::OpenAiCompatible,
+        default_model: "MiniMax-M1",
+        default_base_url: None,
+        base_url_required: true,
+    },
+    ProviderSpec {
+        id: "opencode",
+        name: "Opencode",
+        adapter: LlmAdapter::OpenAiCompatible,
+        default_model: "opencode",
+        default_base_url: Some("http://localhost:4096/v1"),
+        base_url_required: false,
+    },
+    ProviderSpec {
+        id: "openai_compatible",
+        name: "OpenAI-compatible",
+        adapter: LlmAdapter::OpenAiCompatible,
+        default_model: "",
+        default_base_url: None,
+        base_url_required: true,
+    },
+];
+
+pub fn list_provider_infos() -> Vec<LlmProviderInfo> {
+    PROVIDERS
+        .iter()
+        .map(|provider| LlmProviderInfo {
+            id: provider.id.to_string(),
+            name: provider.name.to_string(),
+            adapter: match provider.adapter {
+                LlmAdapter::OpenAiCompatible => "openai_compatible",
+                LlmAdapter::Anthropic => "anthropic",
+                LlmAdapter::Google => "google",
+            }
+            .to_string(),
+            default_model: provider.default_model.to_string(),
+            default_base_url: provider.default_base_url.map(str::to_string),
+            base_url_required: provider.base_url_required,
+        })
+        .collect()
+}
+
+fn provider_spec(provider_id: &str) -> Result<&'static ProviderSpec, String> {
+    let provider_id = provider_id.trim();
+    PROVIDERS
+        .iter()
+        .find(|provider| provider.id == provider_id)
+        .ok_or_else(|| format!("Unsupported LLM provider: {provider_id}"))
+}
+
+fn trim_optional(value: Option<String>) -> Option<String> {
+    value
+        .map(|value| value.trim().trim_end_matches('/').to_string())
+        .filter(|value| !value.is_empty())
+}
+
+fn default_settings() -> LlmSettings {
+    let provider = provider_spec("openai").expect("default provider exists");
+    LlmSettings {
+        provider: provider.id.to_string(),
+        model: provider.default_model.to_string(),
+        base_url: provider.default_base_url.map(str::to_string),
+        has_api_key: has_api_key(provider.id),
+    }
+}
+
+fn key_entry(provider: &str) -> Result<Entry, String> {
+    Entry::new(KEYCHAIN_SERVICE, provider)
+        .map_err(|error| format!("Failed to open secure credential store: {error}"))
+}
+
+fn has_api_key(provider: &str) -> bool {
+    read_api_key(provider).is_ok()
+}
+
+pub fn read_api_key(provider: &str) -> Result<String, String> {
+    key_entry(provider)?
+        .get_password()
+        .map_err(|error| match error {
+            KeyringError::NoEntry => format!("No API key saved for {provider}."),
+            _ => format!("Failed to read API key for {provider}: {error}"),
+        })
+}
+
+pub fn save_api_key(provider: &str, api_key: &str) -> Result<(), String> {
+    let provider = provider_spec(provider)?.id;
+    let api_key = api_key.trim();
+    if api_key.is_empty() {
+        return Err("API key is required.".into());
+    }
+
+    key_entry(provider)?
+        .set_password(api_key)
+        .map_err(|error| format!("Failed to save API key for {provider}: {error}"))
+}
+
+pub fn delete_api_key(provider: &str) -> Result<(), String> {
+    let provider = provider_spec(provider)?.id;
+    match key_entry(provider)?.delete_credential() {
+        Ok(()) | Err(KeyringError::NoEntry) => Ok(()),
+        Err(error) => Err(format!("Failed to delete API key for {provider}: {error}")),
+    }
+}
+
+pub fn load_llm_settings() -> Result<LlmSettings, String> {
+    let Some(mut settings) = read_llm_settings()? else {
+        return Ok(default_settings());
+    };
+
+    let provider = provider_spec(&settings.provider)?;
+    if settings.model.trim().is_empty() {
+        settings.model = provider.default_model.to_string();
+    }
+    settings.base_url = trim_optional(settings.base_url).or_else(|| {
+        provider
+            .default_base_url
+            .filter(|_| !provider.base_url_required)
+            .map(str::to_string)
+    });
+    settings.has_api_key = has_api_key(&settings.provider);
+
+    Ok(settings)
+}
+
+pub fn save_llm_settings(input: SaveLlmSettingsInput) -> Result<LlmSettings, String> {
+    let provider = provider_spec(&input.provider)?;
+    let model = input.model.trim();
+    let model = if model.is_empty() {
+        provider.default_model
+    } else {
+        model
+    };
+
+    if model.is_empty() {
+        return Err("Model is required for this provider.".into());
+    }
+
+    let base_url = trim_optional(input.base_url).or_else(|| {
+        provider
+            .default_base_url
+            .filter(|_| !provider.base_url_required)
+            .map(str::to_string)
+    });
+
+    if provider.base_url_required && base_url.is_none() {
+        return Err("Base URL is required for this provider.".into());
+    }
+
+    let settings = LlmSettings {
+        provider: provider.id.to_string(),
+        model: model.to_string(),
+        base_url,
+        has_api_key: has_api_key(provider.id),
+    };
+    write_llm_settings(&settings)?;
+
+    Ok(settings)
+}
+
+fn runtime_settings(settings: &LlmSettings) -> Result<LlmRuntimeSettings, String> {
+    let provider = provider_spec(&settings.provider)?;
+    let model = settings.model.trim();
+    if model.is_empty() {
+        return Err("Model is required.".into());
+    }
+
+    let base_url = trim_optional(settings.base_url.clone()).or_else(|| {
+        provider
+            .default_base_url
+            .filter(|_| !provider.base_url_required)
+            .map(str::to_string)
+    });
+
+    if provider.base_url_required && base_url.is_none() {
+        return Err("Base URL is required for this provider.".into());
+    }
+
+    Ok(LlmRuntimeSettings {
+        provider: provider.id.to_string(),
+        adapter: provider.adapter,
+        model: model.to_string(),
+        base_url,
+        api_key: read_api_key(provider.id)?,
+    })
+}
+
+pub fn test_llm_provider(settings: &LlmSettings) -> Result<(), String> {
+    let response = complete_json(
+        settings,
+        "Return only strict JSON.",
+        "Return exactly this JSON object: {\"ok\":true}",
+        200,
+    )?;
+    let value = parse_json_response(&response)?;
+
+    if value.get("ok").and_then(Value::as_bool) == Some(true) {
+        return Ok(());
+    }
+
+    Err("Provider responded, but did not return the expected JSON.".into())
+}
+
+pub fn complete_json(
+    settings: &LlmSettings,
+    system_prompt: &str,
+    user_prompt: &str,
+    max_tokens: u32,
+) -> Result<String, String> {
+    let runtime = runtime_settings(settings)?;
+    let client = Client::builder()
+        .timeout(Duration::from_secs(120))
+        .build()
+        .map_err(|error| format!("Failed to create LLM HTTP client: {error}"))?;
+
+    match runtime.adapter {
+        LlmAdapter::OpenAiCompatible => {
+            complete_openai_compatible(&client, &runtime, system_prompt, user_prompt, max_tokens)
+        }
+        LlmAdapter::Anthropic => {
+            complete_anthropic(&client, &runtime, system_prompt, user_prompt, max_tokens)
+        }
+        LlmAdapter::Google => {
+            complete_google(&client, &runtime, system_prompt, user_prompt, max_tokens)
+        }
+    }
+}
+
+pub fn parse_json_response(text: &str) -> Result<Value, String> {
+    let trimmed = text.trim();
+    let without_fence = if trimmed.starts_with("```") {
+        let after_first_line = trimmed
+            .find('\n')
+            .map(|index| &trimmed[index + 1..])
+            .unwrap_or(trimmed);
+        after_first_line
+            .rfind("```")
+            .map(|index| &after_first_line[..index])
+            .unwrap_or(after_first_line)
+            .trim()
+    } else {
+        trimmed
+    };
+
+    parse_first_json_object(without_fence)
+}
+
+fn parse_first_json_object(text: &str) -> Result<Value, String> {
+    let trimmed = text.trim_start();
+    if trimmed.starts_with('{') {
+        return parse_json_object_at(trimmed);
+    }
+
+    let mut parse_error = None;
+
+    for (start, _) in text.match_indices('{') {
+        match parse_json_object_at(&text[start..]) {
+            Ok(value) => return Ok(value),
+            Err(error) => parse_error = Some(error),
+        }
+    }
+
+    match parse_error {
+        Some(error) => Err(error),
+        None => Err("LLM response did not contain a JSON object.".into()),
+    }
+}
+
+fn parse_json_object_at(text: &str) -> Result<Value, String> {
+    let mut deserializer = serde_json::Deserializer::from_str(text);
+    let value = Value::deserialize(&mut deserializer)
+        .map_err(|error| format!("Failed to parse LLM JSON response: {error}"))?;
+
+    if value.is_object() {
+        Ok(value)
+    } else {
+        Err("LLM response JSON was not an object.".into())
+    }
+}
+
+fn response_text(response: reqwest::blocking::Response) -> Result<String, String> {
+    let status = response.status();
+    let body = response
+        .text()
+        .map_err(|error| format!("Failed to read LLM response: {error}"))?;
+
+    if status.is_success() {
+        Ok(body)
+    } else {
+        Err(format!("LLM provider returned {status}: {body}"))
+    }
+}
+
+fn complete_openai_compatible(
+    client: &Client,
+    settings: &LlmRuntimeSettings,
+    system_prompt: &str,
+    user_prompt: &str,
+    max_tokens: u32,
+) -> Result<String, String> {
+    let base_url = settings
+        .base_url
+        .as_deref()
+        .ok_or_else(|| "Base URL is required for this provider.".to_string())?;
+    let url = format!("{base_url}/chat/completions");
+    let body = json!({
+        "model": &settings.model,
+        "messages": [
+            { "role": "system", "content": system_prompt },
+            { "role": "user", "content": user_prompt }
+        ],
+        "temperature": 0.2,
+        "max_tokens": max_tokens
+    });
+
+    let response = client
+        .post(url)
+        .bearer_auth(&settings.api_key)
+        .json(&body)
+        .send()
+        .map_err(|error| format!("Failed to call {}: {error}", settings.provider))?;
+    let body = response_text(response)?;
+    let value = serde_json::from_str::<Value>(&body)
+        .map_err(|error| format!("Failed to parse provider response: {error}"))?;
+
+    value
+        .pointer("/choices/0/message/content")
+        .and_then(Value::as_str)
+        .map(str::to_string)
+        .ok_or_else(|| "Provider response did not include message content.".into())
+}
+
+fn complete_anthropic(
+    client: &Client,
+    settings: &LlmRuntimeSettings,
+    system_prompt: &str,
+    user_prompt: &str,
+    max_tokens: u32,
+) -> Result<String, String> {
+    let base_url = settings
+        .base_url
+        .as_deref()
+        .unwrap_or("https://api.anthropic.com");
+    let url = format!("{base_url}/v1/messages");
+    let body = json!({
+        "model": &settings.model,
+        "system": system_prompt,
+        "messages": [
+            { "role": "user", "content": user_prompt }
+        ],
+        "temperature": 0.2,
+        "max_tokens": max_tokens
+    });
+
+    let response = client
+        .post(url)
+        .header("x-api-key", &settings.api_key)
+        .header("anthropic-version", "2023-06-01")
+        .json(&body)
+        .send()
+        .map_err(|error| format!("Failed to call Anthropic: {error}"))?;
+    let body = response_text(response)?;
+    let value = serde_json::from_str::<Value>(&body)
+        .map_err(|error| format!("Failed to parse Anthropic response: {error}"))?;
+
+    value
+        .pointer("/content/0/text")
+        .and_then(Value::as_str)
+        .map(str::to_string)
+        .ok_or_else(|| "Anthropic response did not include text content.".into())
+}
+
+fn complete_google(
+    client: &Client,
+    settings: &LlmRuntimeSettings,
+    system_prompt: &str,
+    user_prompt: &str,
+    max_tokens: u32,
+) -> Result<String, String> {
+    let base_url = settings
+        .base_url
+        .as_deref()
+        .unwrap_or("https://generativelanguage.googleapis.com/v1beta");
+    let url = format!(
+        "{base_url}/models/{}:generateContent?key={}",
+        settings.model, settings.api_key
+    );
+    let body = json!({
+        "contents": [
+            {
+                "role": "user",
+                "parts": [
+                    { "text": format!("{system_prompt}\n\n{user_prompt}") }
+                ]
+            }
+        ],
+        "generationConfig": {
+            "temperature": 0.2,
+            "maxOutputTokens": max_tokens,
+            "responseMimeType": "application/json"
+        }
+    });
+
+    let response = client
+        .post(url)
+        .json(&body)
+        .send()
+        .map_err(|error| format!("Failed to call Google: {error}"))?;
+    let body = response_text(response)?;
+    let value = serde_json::from_str::<Value>(&body)
+        .map_err(|error| format!("Failed to parse Google response: {error}"))?;
+
+    value
+        .pointer("/candidates/0/content/parts/0/text")
+        .and_then(Value::as_str)
+        .map(str::to_string)
+        .ok_or_else(|| "Google response did not include text content.".into())
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn parses_json_with_trailing_text() {
+        let value =
+            parse_json_response("{\"ok\":true}\nDone.").expect("valid leading JSON should parse");
+
+        assert_eq!(value.get("ok").and_then(Value::as_bool), Some(true));
+    }
+
+    #[test]
+    fn parses_json_inside_fenced_response_with_trailing_text() {
+        let value = parse_json_response("```json\n{\"ok\":true}\n```\nDone.")
+            .expect("fenced JSON should parse");
+
+        assert_eq!(value.get("ok").and_then(Value::as_bool), Some(true));
+    }
+
+    #[test]
+    fn parses_first_json_object_after_preamble() {
+        let value = parse_json_response("Here is the result:\n{\"ok\":true}\nThanks.")
+            .expect("embedded JSON should parse");
+
+        assert_eq!(value.get("ok").and_then(Value::as_bool), Some(true));
+    }
+}
diff --git a/src-tauri/src/services/mod.rs b/src-tauri/src/services/mod.rs
index ab7ba81..9a7f6c8 100644
--- a/src-tauri/src/services/mod.rs
+++ b/src-tauri/src/services/mod.rs
@@ -1,2 +1,4 @@
+pub mod chapters;
 pub mod diff_data;
+pub mod llm;
 pub mod pull_request_sync;
diff --git a/src/App.tsx b/src/App.tsx
index 28a74e5..bdde9ce 100644
--- a/src/App.tsx
+++ b/src/App.tsx
@@ -8,6 +8,8 @@ import { RepoSidebar } from "./components/ui/repo-sidebar";
 import { TrackPullRequestModal } from "./components/ui/track-pull-request-modal";
 import { PatchViewerMain } from "./components/ui/patch-viewer-main";
 import { AppToastViewport } from "./components/ui/app-toast-viewport";
+import { ResizableHandle } from "./components/ui/resizable-handle";
+import { WindowDragRegion } from "./components/ui/window-drag-region";
 import {
   useRepoPickerRepos,
   useSavedRepos,
@@ -20,6 +22,7 @@ import { usePullRequestPicker } from "./hooks/usePullRequestPicker";
 import { useRepoPrSelectionState } from "./hooks/useRepoPrSelectionState";
 import { useTheme } from "./hooks/use-theme";
 import { appToastManager } from "./lib/toasts";
+import { useResizablePanelGroup } from "./hooks/use-resizable-panel-group";
 import { buildReviewThreadsByFile } from "./lib/review-threads";
 import { githubKeys, savedReposQueryOptions } from "./queries/github";
 import type { FileStatsEntry, PullRequestSummary, RepoSummary } from "./types/github";
@@ -31,6 +34,14 @@ function MainApp() {
   const [isSavingRepo, setIsSavingRepo] = useState(false);
   const [isTrackingPullRequest, setIsTrackingPullRequest] = useState(false);
   const refreshedReposRef = useRef<Set<string>>(new Set());
+  const appPanelLayout = useResizablePanelGroup({
+    id: "app-sidebar",
+    orientation: "horizontal",
+    controlledPanel: "first",
+    defaultSize: 25,
+    minSize: 18,
+    maxSize: 42,
+  });
 
   const { repos = [] } = useSavedRepos();
   const {
@@ -53,7 +64,10 @@ function MainApp() {
 
   const {
     changedFiles,
+    chapters,
+    chaptersError,
     changedFilesError,
+    isChaptersLoading,
     isChangedFilesLoading,
     isPatchLoading,
     isReviewThreadsLoading,
@@ -243,8 +257,11 @@ function MainApp() {
 
   return (
     <div className="flex h-screen flex-col overflow-hidden bg-canvas text-ink-900">
-      <div className="flex min-h-0 flex-1">
-        <div className="min-h-0 w-1/4 min-w-[15%] shrink-0">
+      <div ref={appPanelLayout.containerRef} className="flex min-h-0 flex-1">
+        <div
+          className="min-h-0 min-w-[220px] shrink-0"
+          style={appPanelLayout.panelStyle}
+        >
           <RepoSidebar
             repos={repos}
             prsByRepo={prsByRepo}
@@ -264,24 +281,35 @@ function MainApp() {
             }
           />
         </div>
-        <div className="min-h-0 min-w-[30%] flex-1">
-          <PatchViewerMain
-            selectedPrKey={selectedPrKey}
-            selectedPatch={selectedPatch}
-            isPatchLoading={isPatchPreparing}
-            isDark={isDark}
-            patchError={patchError}
-            changedFiles={changedFiles}
-            isChangedFilesLoading={isChangedFilesLoading}
-            changedFilesError={changedFilesError}
-            reviewThreadsByFile={reviewThreadsByFile}
-            reviewThreads={reviewThreads}
-            isReviewThreadsLoading={isReviewThreadsLoading}
-            reviewThreadsError={reviewThreadsError}
-            parsedPatch={parsedPatch}
-            fileStats={fileStats}
-            gitStatus={gitStatus}
-          />
+        <ResizableHandle
+          {...appPanelLayout.handleProps}
+          label="Resize repository sidebar"
+          orientation="horizontal"
+        />
+        <div className="flex min-h-0 min-w-[30%] flex-1 flex-col">
+          <WindowDragRegion className="bg-surface" />
+          <div className="min-h-0 flex-1">
+            <PatchViewerMain
+              selectedPrKey={selectedPrKey}
+              selectedPatch={selectedPatch}
+              isPatchLoading={isPatchPreparing}
+              isDark={isDark}
+              patchError={patchError}
+              changedFiles={changedFiles}
+              isChangedFilesLoading={isChangedFilesLoading}
+              changedFilesError={changedFilesError}
+              chapters={chapters}
+              isChaptersLoading={isChaptersLoading}
+              chaptersError={chaptersError}
+              reviewThreadsByFile={reviewThreadsByFile}
+              reviewThreads={reviewThreads}
+              isReviewThreadsLoading={isReviewThreadsLoading}
+              reviewThreadsError={reviewThreadsError}
+              parsedPatch={parsedPatch}
+              fileStats={fileStats}
+              gitStatus={gitStatus}
+            />
+          </div>
         </div>
       </div>
 
diff --git a/src/components/ui/changed-files-tree.tsx b/src/components/ui/changed-files-tree.tsx
index 6b6d02f..f76566e 100644
--- a/src/components/ui/changed-files-tree.tsx
+++ b/src/components/ui/changed-files-tree.tsx
@@ -1,6 +1,7 @@
 import { useCallback, useEffect, useMemo, useRef } from "react";
 import type { GitStatusEntry } from "@pierre/trees";
 import { FileTree } from "@pierre/trees/react";
+import { normalizePath } from "../../lib/review-threads";
 import type { FileStatsEntry } from "../../types/github";
 
 type ChangedFilesTreeProps = {
@@ -13,6 +14,10 @@ type ChangedFilesTreeProps = {
   selectedFilePath?: string | null;
   fileStats: Map<string, FileStatsEntry> | null;
   gitStatus: GitStatusEntry[] | undefined;
+  chapterContext?: {
+    title: string;
+    detail: string;
+  } | null;
   isDark: boolean;
 };
 
@@ -31,6 +36,7 @@ function ChangedFilesTree({
   selectedFilePath,
   fileStats,
   gitStatus,
+  chapterContext,
   isDark,
 }: ChangedFilesTreeProps) {
   const initialExpandedItems = useMemo(() => {
@@ -47,17 +53,32 @@ function ChangedFilesTree({
   }, [files]);
 
   const fileSet = useMemo(() => new Set(files), [files]);
+  const selectedTreeFilePath = useMemo(() => {
+    if (!selectedFilePath) return null;
+    if (fileSet.has(selectedFilePath)) return selectedFilePath;
+
+    const normalizedSelectedPath = normalizePath(selectedFilePath);
+    return (
+      files.find((file) => normalizePath(file) === normalizedSelectedPath) ??
+      null
+    );
+  }, [fileSet, files, selectedFilePath]);
 
   const totals = useMemo(() => {
     if (!fileStats) return null;
+    const visibleFileSet = new Set(files.map((file) => normalizePath(file)));
     let additions = 0;
     let deletions = 0;
-    for (const entry of fileStats.values()) {
+    for (const [path, entry] of fileStats) {
+      if (!visibleFileSet.has(normalizePath(path))) {
+        continue;
+      }
+
       additions += entry.additions;
       deletions += entry.deletions;
     }
     return { additions, deletions };
-  }, [fileStats]);
+  }, [fileStats, files]);
 
   const onSelectFileRef = useRef(onSelectFile);
   const selectedFilePathRef = useRef(selectedFilePath);
@@ -118,10 +139,17 @@ function ChangedFilesTree({
       }
     >
       <div className="sticky top-0 z-10 shrink-0 border-b border-ink-200 bg-surface px-3 py-2 text-xs text-ink-500 flex justify-between">
-        <p className="text-sm text-ink-900">
-          Changed files{" "}
-          <span className="ml-2 text-ink-500">{files.length}</span>
-        </p>
+        <div className="min-w-0">
+          <p className="truncate text-sm text-ink-900">
+            {chapterContext?.title ?? "Changed files"}{" "}
+            <span className="ml-2 text-ink-500">{files.length}</span>
+          </p>
+          {chapterContext?.detail ? (
+            <p className="mt-0.5 line-clamp-2 text-xs leading-4 text-ink-500">
+              {chapterContext.detail}
+            </p>
+          ) : null}
+        </div>
         <div className="flex items-center gap-2 font-mono font-bold">
           {totals ? (
             <span className="inline-flex items-center gap-1.5">
@@ -129,7 +157,7 @@ function ChangedFilesTree({
                 +{formatCount(totals.additions)}
               </span>
               <span className="text-red-500 dark:text-red-300">
-                −{formatCount(totals.deletions)}
+                -{formatCount(totals.deletions)}
               </span>
             </span>
           ) : null}
@@ -166,11 +194,7 @@ function ChangedFilesTree({
             className="h-full min-h-[220px]"
             files={files}
             initialExpandedItems={initialExpandedItems}
-            selectedItems={
-              selectedFilePath && fileSet.has(selectedFilePath)
-                ? [selectedFilePath]
-                : []
-            }
+            selectedItems={selectedTreeFilePath ? [selectedTreeFilePath] : []}
             onSelectedItemsChange={handleSelectionChange}
             style={fileTreeStyle}
             options={treeOptions}
diff --git a/src/components/ui/chapter-overview.tsx b/src/components/ui/chapter-overview.tsx
new file mode 100644
index 0000000..f0059a3
--- /dev/null
+++ b/src/components/ui/chapter-overview.tsx
@@ -0,0 +1,1024 @@
+import {
+  ArrowLeftIcon,
+  ArrowPathIcon,
+  CheckIcon,
+  ChevronDownIcon,
+  Cog6ToothIcon,
+  SparklesIcon,
+} from "@heroicons/react/20/solid";
+import { useState } from "react";
+import {
+  getFileReviewThreadsForPath,
+  normalizePath,
+  type FileReviewThreads,
+} from "../../lib/review-threads";
+import type {
+  ChapterReviewFocus,
+  ChapterReviewStep,
+  LlmSettings,
+  PullRequestChapter,
+  PullRequestChapterFile,
+  PullRequestChapters,
+} from "../../types/github";
+
+type ChapterOverviewProps = {
+  chapters: PullRequestChapters | null;
+  isLoading: boolean;
+  error: string;
+  settings: LlmSettings | null;
+  settingsError: string;
+  isGenerating: boolean;
+  generationError: string;
+  selectedChapterId: string | null;
+  selectedReviewStepIndex: number | null;
+  completedChapterIds: Set<string>;
+  reviewThreadsByFile: Map<string, FileReviewThreads>;
+  onGenerate: () => void;
+  onSelectChapter: (chapterId: string | null) => void;
+  onSelectReviewFocus: (focus: ChapterReviewFocus) => void;
+  onSelectReviewStep: (stepIndex: number | null) => void;
+  onToggleChapterComplete: (chapterId: string) => void;
+  onOpenSettings: () => void;
+};
+
+type RelatedFile = PullRequestChapterFile & {
+  isMatchedChapterFile: boolean;
+};
+
+function cx(...classes: Array<string | false | undefined>) {
+  return classes.filter(Boolean).join(" ");
+}
+
+function formatSignedCount(value: number) {
+  if (value >= 1000) return `${(value / 1000).toFixed(1).replace(/\.0$/, "")}k`;
+  return String(value);
+}
+
+function formatFileCount(count: number) {
+  return `${count} ${count === 1 ? "file" : "files"}`;
+}
+
+function formatRelativeGeneratedAt(generatedAt: number) {
+  const generatedAtMs = generatedAt * 1000;
+  const elapsedSeconds = Math.max(
+    0,
+    Math.floor((Date.now() - generatedAtMs) / 1000),
+  );
+
+  if (elapsedSeconds < 60) return `${elapsedSeconds}s ago`;
+
+  const elapsedMinutes = Math.floor(elapsedSeconds / 60);
+  if (elapsedMinutes < 60) return `${elapsedMinutes} min ago`;
+
+  const elapsedHours = Math.floor(elapsedMinutes / 60);
+  if (elapsedHours < 24) return `${elapsedHours} hr ago`;
+
+  const elapsedDays = Math.floor(elapsedHours / 24);
+  return `${elapsedDays}d ago`;
+}
+
+function getUniqueChapterFileCount(chapters: PullRequestChapters) {
+  const fileSet = new Set<string>();
+  for (const chapter of chapters.chapters) {
+    for (const file of chapter.files) {
+      fileSet.add(normalizePath(file.path));
+    }
+  }
+  return fileSet.size;
+}
+
+function getChapterTotals(chapters: PullRequestChapters) {
+  return chapters.chapters.reduce(
+    (totals, chapter) => ({
+      additions: totals.additions + chapter.additions,
+      deletions: totals.deletions + chapter.deletions,
+    }),
+    { additions: 0, deletions: 0 },
+  );
+}
+
+function getSeverityRank(severity: string | null) {
+  switch (severity) {
+    case "high":
+      return 3;
+    case "medium":
+      return 2;
+    case "low":
+      return 1;
+    default:
+      return 0;
+  }
+}
+
+function getSeverityLabel(severity: string | null) {
+  if (!severity) return "Low";
+  return severity.charAt(0).toUpperCase() + severity.slice(1);
+}
+
+function getChapterSeverity(chapter: PullRequestChapter) {
+  let highestSeverity: string | null = null;
+  for (const risk of chapter.risks) {
+    if (getSeverityRank(risk.severity) > getSeverityRank(highestSeverity)) {
+      highestSeverity = risk.severity;
+    }
+  }
+  return highestSeverity ?? "low";
+}
+
+function getChapterThreadCount(
+  chapter: PullRequestChapter,
+  reviewThreadsByFile: Map<string, FileReviewThreads>,
+) {
+  return chapter.files.reduce(
+    (total, file) =>
+      total + getFileReviewThreadsForPath(reviewThreadsByFile, file.path).totalCount,
+    0,
+  );
+}
+
+function getSeverityClass(severity: string | null) {
+  switch (severity) {
+    case "high":
+      return "text-red-600 dark:text-red-300";
+    case "medium":
+      return "text-amber-600 dark:text-amber-300";
+    default:
+      return "text-ink-500";
+  }
+}
+
+function getSeverityBadgeClass(severity: string | null) {
+  switch (severity) {
+    case "high":
+      return "border-red-200 bg-red-50 text-red-700 dark:border-red-900/50 dark:bg-red-950/30 dark:text-red-300";
+    case "medium":
+      return "border-amber-200 bg-amber-50 text-amber-700 dark:border-amber-900/50 dark:bg-amber-950/30 dark:text-amber-300";
+    default:
+      return "border-ink-200 bg-surface text-ink-600";
+  }
+}
+
+function getFocusKey(item: ChapterReviewFocus, index: number) {
+  return `${item.title}-${item.path ?? "all"}-${index}`;
+}
+
+function getReviewStepFileCount(
+  chapter: PullRequestChapter,
+  step: ChapterReviewStep,
+) {
+  return step.files.length > 0 ? step.files.length : chapter.files.length;
+}
+
+function getRelatedFiles(
+  chapter: PullRequestChapter,
+  step: ChapterReviewStep,
+): RelatedFile[] {
+  if (step.files.length === 0) {
+    return chapter.files.map((file) => ({
+      ...file,
+      isMatchedChapterFile: true,
+    }));
+  }
+
+  const chapterFilesByPath = new Map(
+    chapter.files.map((file) => [normalizePath(file.path), file]),
+  );
+
+  return step.files.map((path) => {
+    const chapterFile = chapterFilesByPath.get(normalizePath(path));
+    if (chapterFile) {
+      return {
+        ...chapterFile,
+        isMatchedChapterFile: true,
+      };
+    }
+
+    return {
+      path,
+      reason: "",
+      additions: 0,
+      deletions: 0,
+      isMatchedChapterFile: false,
+    };
+  });
+}
+
+function getRelatedRisks(
+  chapter: PullRequestChapter,
+  step: ChapterReviewStep,
+): ChapterReviewFocus[] {
+  if (step.files.length === 0) {
+    return chapter.risks;
+  }
+
+  const fileSet = new Set(step.files.map((file) => normalizePath(file)));
+  const matchingRisks = chapter.risks.filter(
+    (risk) => !risk.path || fileSet.has(normalizePath(risk.path)),
+  );
+
+  return matchingRisks.length > 0 ? matchingRisks : chapter.risks;
+}
+
+type ChapterTodoDetailProps = {
+  chapter: PullRequestChapter;
+  reviewThreadsByFile: Map<string, FileReviewThreads>;
+  selectedStepIndex: number;
+  step: ChapterReviewStep;
+  onBack: () => void;
+  onSelectReviewStep: (stepIndex: number | null) => void;
+};
+
+function ChapterTodoDetail({
+  chapter,
+  reviewThreadsByFile,
+  selectedStepIndex,
+  step,
+  onBack,
+  onSelectReviewStep,
+}: ChapterTodoDetailProps) {
+  const relatedFiles = getRelatedFiles(chapter, step);
+  const relatedRisks = getRelatedRisks(chapter, step);
+  const totalThreads = relatedFiles.reduce(
+    (total, file) =>
+      total + getFileReviewThreadsForPath(reviewThreadsByFile, file.path).totalCount,
+    0,
+  );
+
+  return (
+    <div className="grid min-h-0 gap-3 lg:grid-cols-[minmax(0,1fr)_minmax(240px,34%)]">
+      <div className="min-w-0 rounded-lg border border-ink-200 bg-canvas">
+        <div className="border-b border-ink-200 px-3 py-2.5">
+          <button
+            className="mb-2 inline-flex items-center gap-1.5 rounded-md px-1.5 py-1 text-xs font-medium text-ink-500 transition hover:bg-surface hover:text-ink-900"
+            onClick={onBack}
+            type="button"
+          >
+            <ArrowLeftIcon className="size-3.5" />
+            Back
+          </button>
+          <div className="flex items-start justify-between gap-3">
+            <div className="min-w-0">
+              <p className="text-xs font-medium uppercase tracking-wide text-ink-500">
+                To-do {selectedStepIndex + 1}
+              </p>
+              <h3 className="mt-1 text-base font-semibold leading-6 text-ink-900">
+                {step.title}
+              </h3>
+            </div>
+            <div className="shrink-0 rounded-md bg-surface px-2 py-1 text-right font-mono text-xs font-semibold">
+              <span className="text-emerald-600 dark:text-emerald-300">
+                +{formatSignedCount(chapter.additions)}
+              </span>{" "}
+              <span className="text-red-600 dark:text-red-300">
+                -{formatSignedCount(chapter.deletions)}
+              </span>
+            </div>
+          </div>
+          {step.detail ? (
+            <p className="mt-2 text-sm leading-6 text-ink-700">
+              {step.detail}
+            </p>
+          ) : null}
+        </div>
+
+        <div className="px-3 py-3">
+          <div className="mb-2 flex items-center justify-between gap-3">
+            <p className="text-xs font-medium uppercase tracking-wide text-ink-500">
+              Review checklist
+            </p>
+            <p className="text-xs text-ink-500">
+              {chapter.reviewSteps.length} items
+            </p>
+          </div>
+          <div className="divide-y divide-ink-200 overflow-hidden rounded-md border border-ink-200">
+            {chapter.reviewSteps.map((candidateStep, index) => {
+              const isSelected = index === selectedStepIndex;
+              return (
+                <button
+                  className={cx(
+                    "grid w-full grid-cols-[1.25rem_minmax(0,1fr)_auto] items-start gap-2 px-2.5 py-2 text-left transition",
+                    isSelected
+                      ? "bg-surface"
+                      : "bg-canvas hover:bg-surface/80",
+                  )}
+                  key={`${candidateStep.title}-${index}`}
+                  onClick={() => onSelectReviewStep(index)}
+                  type="button"
+                >
+                  <span
+                    className={cx(
+                      "mt-0.5 flex size-4 items-center justify-center rounded border text-[10px] font-semibold",
+                      isSelected
+                        ? "border-ink-900 bg-ink-900 text-white dark:border-ink-200 dark:bg-ink-200 dark:text-ink-900"
+                        : "border-ink-300 text-ink-500",
+                    )}
+                  >
+                    {index + 1}
+                  </span>
+                  <span className="min-w-0">
+                    <span className="block truncate text-sm font-medium text-ink-900">
+                      {candidateStep.title}
+                    </span>
+                    {candidateStep.detail ? (
+                      <span className="line-clamp-2 text-xs leading-5 text-ink-600">
+                        {candidateStep.detail}
+                      </span>
+                    ) : null}
+                  </span>
+                  <span className="shrink-0 rounded bg-surface px-1.5 py-0.5 font-mono text-[11px] text-ink-500">
+                    {getReviewStepFileCount(chapter, candidateStep)}
+                  </span>
+                </button>
+              );
+            })}
+          </div>
+        </div>
+      </div>
+
+      <div className="grid min-w-0 content-start gap-3">
+        <section className="rounded-lg border border-ink-200 bg-canvas">
+          <div className="flex items-center justify-between gap-3 border-b border-ink-200 px-3 py-2.5">
+            <p className="text-xs font-medium uppercase tracking-wide text-ink-500">
+              Related files
+            </p>
+            <div className="flex items-center gap-2 text-xs text-ink-500">
+              <span>{relatedFiles.length}</span>
+              {totalThreads > 0 ? <span>{totalThreads} threads</span> : null}
+            </div>
+          </div>
+          {relatedFiles.length > 0 ? (
+            <div className="max-h-56 divide-y divide-ink-200 overflow-y-auto scrollbar-hidden">
+              {relatedFiles.map((file) => (
+                <div className="px-3 py-2" key={file.path}>
+                  <div className="flex items-center justify-between gap-2">
+                    <p className="min-w-0 truncate font-mono text-xs text-ink-900">
+                      {file.path}
+                    </p>
+                    {file.isMatchedChapterFile ? (
+                      <span className="shrink-0 whitespace-nowrap font-mono text-[11px] font-semibold">
+                        <span className="text-emerald-600 dark:text-emerald-300">
+                          +{formatSignedCount(file.additions)}
+                        </span>{" "}
+                        <span className="text-red-600 dark:text-red-300">
+                          -{formatSignedCount(file.deletions)}
+                        </span>
+                      </span>
+                    ) : null}
+                  </div>
+                  {file.reason ? (
+                    <p className="mt-1 line-clamp-2 text-xs leading-5 text-ink-600">
+                      {file.reason}
+                    </p>
+                  ) : null}
+                </div>
+              ))}
+            </div>
+          ) : (
+            <div className="px-3 py-4 text-sm text-ink-500">
+              No files attached to this to-do.
+            </div>
+          )}
+        </section>
+
+        <section className="rounded-lg border border-ink-200 bg-canvas">
+          <div className="border-b border-ink-200 px-3 py-2.5">
+            <p className="text-xs font-medium uppercase tracking-wide text-ink-500">
+              Risks
+            </p>
+          </div>
+          {relatedRisks.length > 0 ? (
+            <div className="max-h-44 divide-y divide-ink-200 overflow-y-auto scrollbar-hidden">
+              {relatedRisks.map((risk, index) => (
+                <div className="px-3 py-2" key={`${risk.title}-${index}`}>
+                  <div className="flex items-start justify-between gap-3">
+                    <p
+                      className={cx(
+                        "min-w-0 text-sm font-medium",
+                        getSeverityClass(risk.severity),
+                      )}
+                    >
+                      {risk.title}
+                    </p>
+                    {risk.path ? (
+                      <span className="max-w-[45%] shrink-0 truncate font-mono text-[11px] text-ink-500">
+                        {risk.path}
+                      </span>
+                    ) : null}
+                  </div>
+                  {risk.detail ? (
+                    <p className="mt-1 text-xs leading-5 text-ink-600">
+                      {risk.detail}
+                    </p>
+                  ) : null}
+                </div>
+              ))}
+            </div>
+          ) : (
+            <div className="px-3 py-4 text-sm text-ink-500">
+              No risks called out for this to-do.
+            </div>
+          )}
+        </section>
+      </div>
+    </div>
+  );
+}
+
+type ChapterOverviewContentProps = {
+  chapters: PullRequestChapters;
+  selectedChapter: PullRequestChapter | undefined;
+  selectedChapterId: string | null;
+  selectedReviewStep: ChapterReviewStep | null;
+  activeReviewFocusKey: string | null;
+  completedChapterIds: Set<string>;
+  reviewThreadsByFile: Map<string, FileReviewThreads>;
+  onSelectChapter: (chapterId: string | null) => void;
+  onSelectReviewFocus: (focus: ChapterReviewFocus, focusKey: string) => void;
+  onSelectReviewStep: (stepIndex: number | null) => void;
+  onToggleChapterComplete: (chapterId: string) => void;
+};
+
+function ChapterOverviewContent({
+  chapters,
+  selectedChapter,
+  selectedChapterId,
+  selectedReviewStep,
+  activeReviewFocusKey,
+  completedChapterIds,
+  reviewThreadsByFile,
+  onSelectChapter,
+  onSelectReviewFocus,
+  onSelectReviewStep,
+  onToggleChapterComplete,
+}: ChapterOverviewContentProps) {
+  const completedCount = chapters.chapters.filter((chapter) =>
+    completedChapterIds.has(chapter.id),
+  ).length;
+  const uniqueFileCount = getUniqueChapterFileCount(chapters);
+  const totals = getChapterTotals(chapters);
+  const leadingRisks = chapters.prologue.reviewFocus.slice(0, 4);
+  const recommendedStart = chapters.chapters.slice(0, 4);
+  const currentReviewLabel =
+    selectedReviewStep?.title ?? selectedChapter?.title ?? null;
+
+  return (
+    <div className="grid gap-3">
+      <section className="rounded-xl border border-ink-200 bg-canvas p-3 shadow-sm">
+        <div className="flex flex-wrap items-start justify-between gap-3">
+          <div className="min-w-0 flex-1">
+            <p className="text-xs font-medium uppercase tracking-wide text-ink-500">
+              AI Review Brief
+            </p>
+            {chapters.prologue.summary ? (
+              <p className="mt-1 line-clamp-1 max-w-5xl text-sm leading-6 text-ink-900">
+                {chapters.prologue.summary}
+              </p>
+            ) : (
+              <p className="mt-1 text-sm leading-6 text-ink-700">
+                AI grouped this PR into reviewable chapters.
+              </p>
+            )}
+          </div>
+          <button
+            className={cx(
+              "rounded-md px-2 py-1 text-xs font-medium transition",
+              selectedChapterId === null
+                ? "bg-ink-900 text-white dark:bg-ink-200 dark:text-ink-900"
+                : "text-ink-600 hover:bg-surface hover:text-ink-900",
+            )}
+            onClick={() => onSelectChapter(null)}
+            type="button"
+          >
+            All files
+          </button>
+        </div>
+
+        {leadingRisks.length > 0 ? (
+          <div className="mt-3 flex flex-wrap gap-1.5">
+            {leadingRisks.map((risk, index) => (
+              <button
+                className={cx(
+                  "rounded-full border px-2 py-1 text-xs font-medium transition hover:border-ink-400",
+                  getSeverityBadgeClass(risk.severity),
+                )}
+                key={getFocusKey(risk, index)}
+                onClick={() =>
+                  onSelectReviewFocus(risk, getFocusKey(risk, index))
+                }
+                type="button"
+              >
+                {risk.title}
+              </button>
+            ))}
+          </div>
+        ) : null}
+
+        <div className="mt-3 flex flex-wrap items-center gap-x-4 gap-y-1.5 text-xs leading-5 text-ink-600">
+          <span className="font-medium text-ink-900">
+            {currentReviewLabel
+              ? `Reviewing: ${currentReviewLabel}`
+              : "Reviewing: all files"}
+          </span>
+          <span>
+            Start:{" "}
+            {recommendedStart.map((chapter, index) => (
+              <button
+                className="font-medium text-ink-800 transition hover:text-ink-900"
+                key={chapter.id}
+                onClick={() => onSelectChapter(chapter.id)}
+                type="button"
+              >
+                {index > 0 ? ", " : ""}
+                {index + 1}. {chapter.title}
+              </button>
+            ))}
+          </span>
+          <span>
+            Generated from {uniqueFileCount} files -{" "}
+            {formatRelativeGeneratedAt(chapters.generatedAt)}
+          </span>
+          <span className="font-mono font-semibold">
+            +{formatSignedCount(totals.additions)} / -
+            {formatSignedCount(totals.deletions)}
+          </span>
+        </div>
+      </section>
+
+      <details className="group rounded-lg border border-ink-200 bg-canvas">
+        <summary className="flex cursor-pointer list-none items-center justify-between gap-3 px-3 py-2.5 text-sm font-medium text-ink-900 [&::-webkit-details-marker]:hidden">
+          <span>Show full AI summary</span>
+          <ChevronDownIcon className="size-4 text-ink-500 transition group-open:rotate-180" />
+        </summary>
+        <div className="border-t border-ink-200 px-3 py-3">
+          <p className="text-xs font-medium uppercase tracking-wide text-ink-500">
+            What changed
+          </p>
+          {chapters.prologue.summary ? (
+            <p className="mt-1 text-sm leading-6 text-ink-800">
+              {chapters.prologue.summary}
+            </p>
+          ) : null}
+
+          {chapters.prologue.keyChanges.length > 0 ? (
+            <div className="mt-3">
+              <p className="mb-1.5 text-xs font-medium uppercase tracking-wide text-ink-500">
+                Key changes
+              </p>
+              <div className="grid gap-2">
+                {chapters.prologue.keyChanges.map((item, index) => (
+                  <div
+                    className="grid grid-cols-[8px_minmax(0,1fr)] gap-2"
+                    key={`${item.title}-${index}`}
+                  >
+                    <span className="mt-2 size-1.5 rounded-full bg-ink-400" />
+                    <div className="min-w-0">
+                      <p className="text-sm font-medium text-ink-900">
+                        {item.title}
+                      </p>
+                      {item.detail ? (
+                        <p className="text-xs leading-5 text-ink-600">
+                          {item.detail}
+                        </p>
+                      ) : null}
+                    </div>
+                  </div>
+                ))}
+              </div>
+            </div>
+          ) : null}
+        </div>
+      </details>
+
+      {chapters.prologue.reviewFocus.length > 0 ? (
+        <section className="rounded-lg border border-ink-200 bg-canvas p-3">
+          <div className="mb-2 flex items-center justify-between gap-3">
+            <p className="text-xs font-medium uppercase tracking-wide text-ink-500">
+              What to review carefully
+            </p>
+            <p className="text-xs text-ink-500">
+              {chapters.prologue.reviewFocus.length} focus areas
+            </p>
+          </div>
+          <div className="grid gap-2 md:grid-cols-2">
+            {chapters.prologue.reviewFocus.map((item, index) => {
+              const focusKey = getFocusKey(item, index);
+              const isActive = activeReviewFocusKey === focusKey;
+
+              return (
+                <button
+                  className={cx(
+                    "grid min-w-0 gap-2 rounded-lg border px-3 py-2.5 text-left transition",
+                    isActive
+                      ? "border-ink-500 bg-canvasDark"
+                      : "border-ink-200 bg-surface hover:border-ink-300 hover:bg-canvasDark",
+                  )}
+                  key={focusKey}
+                  onClick={() => onSelectReviewFocus(item, focusKey)}
+                  type="button"
+                >
+                  <span className="flex min-w-0 items-start justify-between gap-3">
+                    <span className="min-w-0">
+                      <span
+                        className={cx(
+                          "block text-xs font-semibold uppercase tracking-wide",
+                          getSeverityClass(item.severity),
+                        )}
+                      >
+                        {getSeverityLabel(item.severity)}
+                      </span>
+                      <span className="mt-0.5 block truncate text-sm font-semibold text-ink-900">
+                        {item.title}
+                      </span>
+                    </span>
+                    <span className="shrink-0 rounded-md border border-ink-200 bg-canvas px-2 py-1 text-xs font-medium text-ink-700">
+                      Review now
+                    </span>
+                  </span>
+
+                  {item.path ? (
+                    <span className="truncate font-mono text-xs text-ink-500">
+                      {item.path}
+                    </span>
+                  ) : null}
+
+                  {isActive && item.detail ? (
+                    <span className="rounded-md border border-ink-200 bg-canvas px-2.5 py-2 text-xs leading-5 text-ink-700">
+                      AI reason: {item.detail}
+                    </span>
+                  ) : null}
+                </button>
+              );
+            })}
+          </div>
+        </section>
+      ) : null}
+
+      <section className="rounded-lg border border-ink-200 bg-canvas p-3">
+        <div className="mb-2 flex items-center justify-between">
+          <p className="text-xs font-medium uppercase tracking-wide text-ink-500">
+            AI Review Plan - {chapters.chapters.length} chapters
+          </p>
+          <p className="text-xs text-ink-500">
+            {completedCount} / {chapters.chapters.length} complete
+          </p>
+        </div>
+        <div className="grid gap-2">
+          {chapters.chapters.map((chapter, index) => {
+            const isSelected = selectedChapterId === chapter.id;
+            const isComplete = completedChapterIds.has(chapter.id);
+            const commentCount = getChapterThreadCount(
+              chapter,
+              reviewThreadsByFile,
+            );
+            const severity = getChapterSeverity(chapter);
+
+            return (
+              <div
+                className={cx(
+                  "grid grid-cols-[auto_minmax(0,1fr)] gap-3 rounded-lg border px-3 py-2.5 transition",
+                  isSelected
+                    ? "border-ink-400 bg-canvasDark"
+                    : "border-ink-200 bg-surface hover:border-ink-300 hover:bg-canvasDark",
+                )}
+                key={chapter.id}
+              >
+                <button
+                  aria-label={
+                    isComplete
+                      ? `Mark ${chapter.title} incomplete`
+                      : `Mark ${chapter.title} reviewed`
+                  }
+                  className={cx(
+                    "mt-0.5 flex size-5 shrink-0 items-center justify-center rounded-full border transition",
+                    isComplete
+                      ? "border-emerald-600 bg-emerald-600 text-white dark:border-emerald-400 dark:bg-emerald-400 dark:text-ink-900"
+                      : "border-ink-400 text-transparent hover:border-ink-700",
+                  )}
+                  onClick={() => onToggleChapterComplete(chapter.id)}
+                  type="button"
+                >
+                  <CheckIcon className="size-3.5" />
+                </button>
+
+                <button
+                  className="grid min-w-0 gap-1 text-left"
+                  onClick={() => onSelectChapter(chapter.id)}
+                  type="button"
+                >
+                  <span className="flex min-w-0 items-start justify-between gap-3">
+                    <span className="min-w-0">
+                      <span
+                        className={cx(
+                          "block truncate text-sm font-semibold text-ink-900",
+                          isComplete && "text-ink-500 line-through",
+                        )}
+                      >
+                        {index + 1}. {chapter.title}
+                      </span>
+                      <span className="mt-0.5 block truncate text-xs text-ink-500">
+                        {formatFileCount(chapter.files.length)} -{" "}
+                        {getSeverityLabel(severity)} risk
+                        {commentCount > 0 ? ` - ${commentCount} comments` : ""}
+                      </span>
+                    </span>
+                    <span className="shrink-0 whitespace-nowrap font-mono text-xs font-semibold">
+                      <span className="text-emerald-600 dark:text-emerald-300">
+                        +{formatSignedCount(chapter.additions)}
+                      </span>{" "}
+                      <span className="text-red-600 dark:text-red-300">
+                        -{formatSignedCount(chapter.deletions)}
+                      </span>
+                    </span>
+                  </span>
+                  <span className="line-clamp-2 text-xs leading-5 text-ink-600">
+                    {chapter.reviewSteps[0]?.detail ||
+                      chapter.summary ||
+                      "Review this chapter's files together."}
+                  </span>
+                </button>
+              </div>
+            );
+          })}
+        </div>
+      </section>
+
+      {selectedChapter ? (
+        <section className="rounded-lg border border-ink-200 bg-canvas p-3">
+          <div className="mb-2 flex items-center justify-between gap-3">
+            <p className="min-w-0 truncate text-sm font-semibold text-ink-900">
+              {selectedChapter.title}
+            </p>
+            <span className="shrink-0 whitespace-nowrap font-mono text-xs font-semibold">
+              <span className="text-emerald-600 dark:text-emerald-300">
+                +{formatSignedCount(selectedChapter.additions)}
+              </span>{" "}
+              <span className="text-red-600 dark:text-red-300">
+                -{formatSignedCount(selectedChapter.deletions)}
+              </span>
+            </span>
+          </div>
+
+          {selectedChapter.summary ? (
+            <p className="text-sm leading-6 text-ink-800">
+              {selectedChapter.summary}
+            </p>
+          ) : null}
+
+          <div className="mt-3">
+            <div className="mb-1.5 flex items-center justify-between gap-3">
+              <p className="text-xs font-medium uppercase tracking-wide text-ink-500">
+                Recommended review order
+              </p>
+              <p className="text-xs text-ink-500">
+                {selectedChapter.reviewSteps.length}
+              </p>
+            </div>
+
+            {selectedChapter.reviewSteps.length > 0 ? (
+              <div className="grid gap-1.5">
+                {selectedChapter.reviewSteps.map((step, index) => (
+                  <button
+                    className="grid w-full grid-cols-[1.25rem_minmax(0,1fr)_auto] gap-2 rounded-md border border-ink-200 bg-surface px-2.5 py-2 text-left transition hover:border-ink-300 hover:bg-canvasDark"
+                    key={`${step.title}-${index}`}
+                    onClick={() => onSelectReviewStep(index)}
+                    type="button"
+                  >
+                    <span className="mt-0.5 flex size-5 items-center justify-center rounded-full bg-canvas text-[11px] font-semibold text-ink-600">
+                      {index + 1}
+                    </span>
+                    <span className="min-w-0">
+                      <span className="block truncate text-sm font-medium text-ink-900">
+                        {step.title}
+                      </span>
+                      {step.detail ? (
+                        <span className="line-clamp-2 text-xs leading-5 text-ink-600">
+                          {step.detail}
+                        </span>
+                      ) : null}
+                    </span>
+                    <span className="shrink-0 rounded bg-canvas px-1.5 py-0.5 font-mono text-[11px] text-ink-500">
+                      {getReviewStepFileCount(selectedChapter, step)}
+                    </span>
+                  </button>
+                ))}
+              </div>
+            ) : (
+              <div className="rounded-md border border-ink-200 bg-surface px-3 py-3 text-sm text-ink-500">
+                No review steps for this chapter.
+              </div>
+            )}
+          </div>
+
+          {selectedChapter.risks.length > 0 ? (
+            <div className="mt-3">
+              <p className="mb-1.5 text-xs font-medium uppercase tracking-wide text-ink-500">
+                What to review carefully
+              </p>
+              <div className="grid gap-2">
+                {selectedChapter.risks.map((risk, index) => (
+                  <div
+                    className="flex items-start justify-between gap-3"
+                    key={`${risk.title}-${index}`}
+                  >
+                    <div className="min-w-0">
+                      <p
+                        className={cx(
+                          "text-sm font-medium",
+                          getSeverityClass(risk.severity),
+                        )}
+                      >
+                        {risk.title}
+                      </p>
+                      {risk.detail ? (
+                        <p className="text-xs leading-5 text-ink-600">
+                          {risk.detail}
+                        </p>
+                      ) : null}
+                    </div>
+                    {risk.path ? (
+                      <span className="max-w-[36%] shrink-0 truncate font-mono text-xs text-ink-500">
+                        {risk.path}
+                      </span>
+                    ) : null}
+                  </div>
+                ))}
+              </div>
+            </div>
+          ) : null}
+        </section>
+      ) : null}
+    </div>
+  );
+}
+
+function ChapterOverview({
+  chapters,
+  isLoading,
+  error,
+  settings,
+  settingsError,
+  isGenerating,
+  generationError,
+  selectedChapterId,
+  selectedReviewStepIndex,
+  completedChapterIds,
+  reviewThreadsByFile,
+  onGenerate,
+  onSelectChapter,
+  onSelectReviewFocus,
+  onSelectReviewStep,
+  onToggleChapterComplete,
+  onOpenSettings,
+}: ChapterOverviewProps) {
+  const [activeReviewFocusKey, setActiveReviewFocusKey] = useState<string | null>(
+    null,
+  );
+  const hasApiKey = Boolean(settings?.hasApiKey);
+  const canGenerate = hasApiKey && !isGenerating;
+  const selectedChapter = chapters?.chapters.find(
+    (chapter) => chapter.id === selectedChapterId,
+  );
+  const selectedReviewStep =
+    selectedChapter && selectedReviewStepIndex !== null
+      ? selectedChapter.reviewSteps[selectedReviewStepIndex]
+      : null;
+
+  function handleSelectChapter(chapterId: string | null) {
+    setActiveReviewFocusKey(null);
+    onSelectChapter(chapterId);
+  }
+
+  function handleSelectReviewStep(stepIndex: number | null) {
+    setActiveReviewFocusKey(null);
+    onSelectReviewStep(stepIndex);
+  }
+
+  return (
+    <section className="flex h-full min-h-0 flex-col border-b border-ink-200 bg-surface">
+      <div className="flex shrink-0 items-center gap-2 border-b border-ink-200 px-4 py-2.5">
+        <div className="flex min-w-0 flex-1 items-center gap-2">
+          <SparklesIcon className="size-4 shrink-0 text-ink-500" />
+          <p className="truncate text-sm font-medium text-ink-900">
+            {chapters
+              ? `AI Review Plan - ${chapters.chapters.length} chapters`
+              : "Summarize with AI"}
+            {chapters ? (
+              <span className="ml-2 text-xs font-normal text-ink-500">
+                {chapters.provider} / {chapters.model}
+              </span>
+            ) : null}
+          </p>
+          {selectedReviewStep ? (
+            <span className="hidden min-w-0 truncate text-xs text-ink-500 md:inline">
+              Reviewing: {selectedReviewStep.title}
+            </span>
+          ) : selectedChapter ? (
+            <span className="hidden min-w-0 truncate text-xs text-ink-500 md:inline">
+              Reviewing: {selectedChapter.title}
+            </span>
+          ) : null}
+        </div>
+
+        <button
+          aria-label="AI provider settings"
+          className="inline-flex size-7 items-center justify-center rounded-md text-ink-500 transition hover:bg-canvasDark hover:text-ink-900"
+          onClick={onOpenSettings}
+          type="button"
+        >
+          <Cog6ToothIcon className="size-4" />
+        </button>
+        <button
+          className="inline-flex items-center gap-1.5 rounded-md bg-ink-900 px-2.5 py-1.5 text-xs font-medium text-white transition hover:bg-ink-700 disabled:cursor-default disabled:opacity-60 dark:bg-ink-200 dark:text-ink-900 dark:hover:bg-ink-300"
+          disabled={!canGenerate}
+          onClick={onGenerate}
+          type="button"
+        >
+          <ArrowPathIcon
+            className={cx("size-3.5", isGenerating && "animate-spin")}
+          />
+          {isGenerating
+            ? chapters
+              ? "Regenerating"
+              : "Summarizing"
+            : chapters
+              ? "Regenerate summary"
+              : "Summarize with AI"}
+        </button>
+      </div>
+
+      <div className="min-h-0 flex-1 overflow-y-auto px-4 py-3 scrollbar-hidden">
+        {isLoading ? (
+          <div className="py-3 text-sm text-ink-500">
+            Loading cached AI summary...
+          </div>
+        ) : null}
+
+        {settingsError ? (
+          <div className="mb-3 rounded-lg border border-red-200 bg-red-50 px-3 py-2 text-sm text-danger-600 dark:border-red-900/40 dark:bg-red-950/30 dark:text-red-300">
+            {settingsError}
+          </div>
+        ) : null}
+
+        {error ? (
+          <div className="mb-3 rounded-lg border border-red-200 bg-red-50 px-3 py-2 text-sm text-danger-600 dark:border-red-900/40 dark:bg-red-950/30 dark:text-red-300">
+            {error}
+          </div>
+        ) : null}
+
+        {generationError ? (
+          <div className="mb-3 rounded-lg border border-red-200 bg-red-50 px-3 py-2 text-sm text-danger-600 dark:border-red-900/40 dark:bg-red-950/30 dark:text-red-300">
+            {generationError}
+          </div>
+        ) : null}
+
+        {!isLoading && !chapters ? (
+          <div className="rounded-lg border border-ink-200 bg-canvas px-3 py-3">
+            <p className="text-sm font-medium text-ink-900">
+              {hasApiKey
+                ? "No AI summary yet."
+                : "Configure a provider to summarize with AI."}
+            </p>
+            <p className="mt-1 text-xs leading-5 text-ink-600">
+              {hasApiKey
+                ? "Generate a cached review story for this PR."
+                : "API keys are saved in your system keychain and will not be shown again."}
+            </p>
+          </div>
+        ) : null}
+
+        {chapters && selectedChapter && selectedReviewStep ? (
+          <ChapterTodoDetail
+            chapter={selectedChapter}
+            reviewThreadsByFile={reviewThreadsByFile}
+            selectedStepIndex={selectedReviewStepIndex ?? 0}
+            step={selectedReviewStep}
+            onBack={() => handleSelectReviewStep(null)}
+            onSelectReviewStep={handleSelectReviewStep}
+          />
+        ) : null}
+
+        {chapters && !selectedReviewStep ? (
+          <ChapterOverviewContent
+            chapters={chapters}
+            reviewThreadsByFile={reviewThreadsByFile}
+            selectedChapter={selectedChapter}
+            selectedChapterId={selectedChapterId}
+            selectedReviewStep={selectedReviewStep}
+            activeReviewFocusKey={activeReviewFocusKey}
+            completedChapterIds={completedChapterIds}
+            onSelectChapter={handleSelectChapter}
+            onSelectReviewFocus={(focus, focusKey) => {
+              setActiveReviewFocusKey(focusKey);
+              onSelectReviewFocus(focus);
+            }}
+            onSelectReviewStep={handleSelectReviewStep}
+            onToggleChapterComplete={onToggleChapterComplete}
+          />
+        ) : null}
+      </div>
+    </section>
+  );
+}
+
+export { ChapterOverview };
+export type { ChapterOverviewProps };
diff --git a/src/components/ui/comment-markdown.tsx b/src/components/ui/comment-markdown.tsx
index cfb12c0..b44dd2e 100644
--- a/src/components/ui/comment-markdown.tsx
+++ b/src/components/ui/comment-markdown.tsx
@@ -1,42 +1,21 @@
 import { useEffect, useState, type ComponentProps } from "react";
 import Markdown, { RuleType } from "markdown-to-jsx";
-import { codeToHtml, type BundledLanguage } from "shiki";
-import type { ThemeRegistrationResolved } from "@shikijs/types";
-import pierreDarkTheme from "@pierre/theme/pierre-dark";
-import pierreLightTheme from "@pierre/theme/pierre-light";
+import {
+  getHighlighterOptions,
+  getSharedHighlighter,
+  type DiffsThemeNames,
+  type SupportedLanguages,
+} from "@pierre/diffs";
 import { useDocumentDarkMode } from "../../hooks/use-document-dark-mode";
 
 const CODE_THEME = {
-  dark: { id: "pierre-dark", theme: toShikiTheme(pierreDarkTheme) },
-  light: { id: "pierre-light", theme: toShikiTheme(pierreLightTheme) },
-} as const;
+  dark: "pierre-dark",
+  light: "pierre-light",
+} as const satisfies Record<"dark" | "light", DiffsThemeNames>;
 
 const codeHtmlCache = new Map<string, Promise<string>>();
 
-function toShikiTheme(theme: typeof pierreDarkTheme): ThemeRegistrationResolved {
-  const semanticTokenColors = Object.fromEntries(
-    Object.entries(theme.semanticTokenColors).filter(
-      (entry): entry is [string, string] => typeof entry[1] === "string",
-    ),
-  );
-
-  return {
-    ...theme,
-    settings: theme.tokenColors.map((token) => ({
-      ...token,
-      settings: { ...token.settings },
-    })),
-    tokenColors: theme.tokenColors.map((token) => ({
-      ...token,
-      settings: { ...token.settings },
-    })),
-    semanticTokenColors,
-    fg: theme.colors["editor.foreground"] ?? theme.colors.foreground ?? "#000000",
-    bg: theme.colors["editor.background"] ?? "#ffffff",
-  };
-}
-
-function normalizeLanguage(language: string | undefined) {
+function normalizeLanguage(language: string | undefined): SupportedLanguages {
   if (!language) return "text";
 
   switch (language.toLowerCase()) {
@@ -54,7 +33,7 @@ function normalizeLanguage(language: string | undefined) {
   }
 }
 
-function getThemeEntry(isDark: boolean) {
+function getThemeName(isDark: boolean): DiffsThemeNames {
   return isDark ? CODE_THEME.dark : CODE_THEME.light;
 }
 
@@ -82,15 +61,19 @@ function MarkdownCodeBlock({
   useEffect(() => {
     let cancelled = false;
     const normalizedLanguage = normalizeLanguage(lang);
-    const themeEntry = getThemeEntry(isDark);
-    const cacheKey = `${themeEntry.id}:${normalizedLanguage}:${text}`;
+    const themeName = getThemeName(isDark);
+    const cacheKey = `${themeName}:${normalizedLanguage}:${text}`;
 
     let promise = codeHtmlCache.get(cacheKey);
     if (!promise) {
-      promise = codeToHtml(text, {
-        lang: normalizedLanguage as BundledLanguage,
-        theme: themeEntry.theme,
-      });
+      promise = getSharedHighlighter(
+        getHighlighterOptions(normalizedLanguage, { theme: themeName }),
+      ).then((highlighter) =>
+        highlighter.codeToHtml(text, {
+          lang: normalizedLanguage,
+          theme: themeName,
+        }),
+      );
       codeHtmlCache.set(cacheKey, promise);
     }
 
diff --git a/src/components/ui/llm-settings-modal.tsx b/src/components/ui/llm-settings-modal.tsx
new file mode 100644
index 0000000..3e06ab9
--- /dev/null
+++ b/src/components/ui/llm-settings-modal.tsx
@@ -0,0 +1,321 @@
+import { useEffect, useMemo, useState } from "react";
+import { useMutation, useQuery, useQueryClient } from "@tanstack/react-query";
+import {
+  AlertDialog,
+  AlertDialogAction,
+  AlertDialogCancel,
+  AlertDialogContent,
+  AlertDialogDescription,
+  AlertDialogFooter,
+  AlertDialogHeader,
+  AlertDialogTitle,
+} from "./alert-dialog";
+import {
+  deleteLlmApiKey,
+  llmKeys,
+  llmProvidersQueryOptions,
+  llmSettingsQueryOptions,
+  saveLlmSettings,
+  setLlmApiKey,
+  testLlmProvider,
+} from "../../queries/llm";
+
+type LlmSettingsModalProps = {
+  open: boolean;
+  onOpenChange: (open: boolean) => void;
+};
+
+function normalizeBaseUrl(value: string) {
+  const trimmed = value.trim().replace(/\/+$/, "");
+  return trimmed.length > 0 ? trimmed : null;
+}
+
+function formatDuration(ms: number) {
+  return `${(ms / 1000).toFixed(1)}s`;
+}
+
+function cx(...classes: Array<string | false | undefined>) {
+  return classes.filter(Boolean).join(" ");
+}
+
+function LlmSettingsModal({ open, onOpenChange }: LlmSettingsModalProps) {
+  const queryClient = useQueryClient();
+  const providersQuery = useQuery(llmProvidersQueryOptions());
+  const settingsQuery = useQuery(llmSettingsQueryOptions());
+  const providers = providersQuery.data ?? [];
+  const settings = settingsQuery.data ?? null;
+  const [provider, setProvider] = useState("openai");
+  const [model, setModel] = useState("");
+  const [baseUrl, setBaseUrl] = useState("");
+  const [apiKey, setApiKey] = useState("");
+  const [feedback, setFeedback] = useState("");
+  const [error, setError] = useState("");
+
+  const selectedProvider = useMemo(
+    () => providers.find((item) => item.id === provider) ?? providers[0],
+    [provider, providers],
+  );
+
+  useEffect(() => {
+    if (!open || !settings) return;
+
+    setProvider(settings.provider);
+    setModel(settings.model);
+    setBaseUrl(settings.baseUrl ?? "");
+    setApiKey("");
+    setFeedback("");
+    setError("");
+  }, [open, settings]);
+
+  const saveMutation = useMutation({
+    mutationFn: () =>
+      saveLlmSettings({
+        provider,
+        model,
+        baseUrl: normalizeBaseUrl(baseUrl),
+      }),
+    onSuccess: (nextSettings) => {
+      queryClient.setQueryData(llmKeys.settings(), nextSettings);
+    },
+  });
+
+  const keyMutation = useMutation({
+    mutationFn: (key: string) => setLlmApiKey(provider, key),
+    onSuccess: (nextSettings) => {
+      queryClient.setQueryData(llmKeys.settings(), nextSettings);
+    },
+  });
+
+  const deleteKeyMutation = useMutation({
+    mutationFn: () => deleteLlmApiKey(provider),
+    onSuccess: (nextSettings) => {
+      queryClient.setQueryData(llmKeys.settings(), nextSettings);
+      setApiKey("");
+      setFeedback("API key removed.");
+    },
+  });
+
+  const testMutation = useMutation({
+    mutationFn: testLlmProvider,
+  });
+
+  const isPending =
+    saveMutation.isPending ||
+    keyMutation.isPending ||
+    deleteKeyMutation.isPending ||
+    testMutation.isPending;
+
+  function applyProviderDefaults(nextProviderId: string) {
+    const nextProvider = providers.find((item) => item.id === nextProviderId);
+    setProvider(nextProviderId);
+    setModel(nextProvider?.defaultModel ?? "");
+    setBaseUrl(nextProvider?.defaultBaseUrl ?? "");
+    setFeedback("");
+    setError("");
+  }
+
+  async function saveCurrentSettings() {
+    setError("");
+    setFeedback("");
+    const nextSettings = await saveMutation.mutateAsync();
+
+    if (apiKey.trim()) {
+      const settingsWithKey = await keyMutation.mutateAsync(apiKey);
+      setApiKey("");
+      return settingsWithKey;
+    }
+
+    return nextSettings;
+  }
+
+  async function handleSave() {
+    try {
+      await saveCurrentSettings();
+      setFeedback("Provider saved.");
+      onOpenChange(false);
+    } catch (caught) {
+      setError(caught instanceof Error ? caught.message : String(caught));
+    }
+  }
+
+  async function handleTest() {
+    try {
+      setError("");
+      setFeedback("");
+      await saveCurrentSettings();
+      const startedAt = performance.now();
+      await testMutation.mutateAsync();
+      setFeedback(
+        `Connection successful. Model responded in ${formatDuration(
+          performance.now() - startedAt,
+        )}.`,
+      );
+    } catch (caught) {
+      const detail = caught instanceof Error ? caught.message : String(caught);
+      setError(
+        `Connection failed. Check the base URL, model name, or API key. ${detail}`,
+      );
+    }
+  }
+
+  async function handleDeleteKey() {
+    try {
+      setError("");
+      await deleteKeyMutation.mutateAsync();
+    } catch (caught) {
+      setError(caught instanceof Error ? caught.message : String(caught));
+    }
+  }
+
+  const hasSavedKey =
+    settings?.provider === provider ? settings.hasApiKey : false;
+  const canSave =
+    !isPending &&
+    provider.trim().length > 0 &&
+    model.trim().length > 0 &&
+    (!selectedProvider?.baseUrlRequired || normalizeBaseUrl(baseUrl) !== null);
+
+  return (
+    <AlertDialog onOpenChange={onOpenChange} open={open}>
+      <AlertDialogContent className="max-w-[620px] overflow-hidden border border-ink-200">
+        <div className="border-b border-ink-200 px-5 py-4">
+          <AlertDialogHeader>
+            <AlertDialogTitle>AI Provider</AlertDialogTitle>
+            <AlertDialogDescription>
+              Bring your own model key for PR summaries, review chapters, and AI
+              diff guidance.
+            </AlertDialogDescription>
+          </AlertDialogHeader>
+        </div>
+
+        <div className="min-h-0 overflow-y-auto px-5 py-4">
+          <div className="grid gap-4">
+            <label className="grid gap-1.5 text-sm">
+              <span className="text-xs font-medium uppercase tracking-wide text-ink-500">
+                Provider
+              </span>
+              <select
+                className="h-10 rounded-lg border border-ink-200 bg-canvas px-3 text-sm text-ink-900 outline-none transition focus:border-ink-400"
+                disabled={isPending || providersQuery.isLoading}
+                onChange={(event) => applyProviderDefaults(event.currentTarget.value)}
+                value={provider}
+              >
+                {providers.map((item) => (
+                  <option key={item.id} value={item.id}>
+                    {item.name}
+                  </option>
+                ))}
+              </select>
+            </label>
+
+            <div className="grid grid-cols-1 gap-4 md:grid-cols-2">
+              <label className="grid gap-1.5 text-sm">
+                <span className="text-xs font-medium uppercase tracking-wide text-ink-500">
+                  Model
+                </span>
+                <input
+                  className="h-10 rounded-lg border border-ink-200 bg-canvas px-3 text-sm text-ink-900 outline-none transition placeholder:text-ink-500 focus:border-ink-400"
+                  disabled={isPending}
+                  onChange={(event) => setModel(event.currentTarget.value)}
+                  placeholder={selectedProvider?.defaultModel || "model"}
+                  value={model}
+                />
+              </label>
+
+              <label className="grid gap-1.5 text-sm">
+                <span className="text-xs font-medium uppercase tracking-wide text-ink-500">
+                  Base URL
+                </span>
+                <input
+                  className="h-10 rounded-lg border border-ink-200 bg-canvas px-3 text-sm text-ink-900 outline-none transition placeholder:text-ink-500 focus:border-ink-400"
+                  disabled={isPending}
+                  onChange={(event) => setBaseUrl(event.currentTarget.value)}
+                  placeholder={
+                    selectedProvider?.defaultBaseUrl ??
+                    "https://provider.example/v1"
+                  }
+                  value={baseUrl}
+                />
+              </label>
+            </div>
+
+            <label className="grid gap-1.5 text-sm">
+              <span className="text-xs font-medium uppercase tracking-wide text-ink-500">
+                API key
+              </span>
+              <input
+                className="h-10 rounded-lg border border-ink-200 bg-canvas px-3 text-sm text-ink-900 outline-none transition placeholder:text-ink-500 focus:border-ink-400"
+                disabled={isPending}
+                onChange={(event) => setApiKey(event.currentTarget.value)}
+                placeholder={hasSavedKey ? "Saved in system keychain" : "Paste key"}
+                type="password"
+                value={apiKey}
+              />
+            </label>
+
+            {hasSavedKey ? (
+              <div className="flex items-center justify-between rounded-lg border border-ink-200 bg-canvas px-3 py-2 text-sm">
+                <span className="text-ink-600">
+                  API key saved in your system keychain. It will not be shown
+                  again.
+                </span>
+                <button
+                  className="rounded-md px-2 py-1 text-xs font-medium text-danger-600 transition hover:bg-surface"
+                  disabled={isPending}
+                  onClick={() => void handleDeleteKey()}
+                  type="button"
+                >
+                  Remove
+                </button>
+              </div>
+            ) : null}
+
+            {error ? (
+              <div className="rounded-lg border border-red-200 bg-red-50 px-3 py-2 text-sm text-danger-600 dark:border-red-900/40 dark:bg-red-950/30 dark:text-red-300">
+                {error}
+              </div>
+            ) : null}
+
+            {feedback ? (
+              <div className="rounded-lg border border-emerald-200 bg-emerald-50 px-3 py-2 text-sm text-emerald-700 dark:border-emerald-900/40 dark:bg-emerald-950/30 dark:text-emerald-300">
+                {feedback}
+              </div>
+            ) : null}
+
+            <p className="text-xs leading-5 text-ink-500">
+              This provider will be used to generate PR summaries, review
+              chapters, and AI diff guidance.
+            </p>
+          </div>
+        </div>
+
+        <AlertDialogFooter className="border-t border-ink-200 px-5 py-4">
+          <button
+            className={cx(
+              "rounded-lg px-3.5 py-2.5 text-sm font-medium text-ink-700 transition hover:bg-canvasDark hover:text-ink-900",
+              isPending && "cursor-default opacity-60",
+            )}
+            disabled={!canSave}
+            onClick={() => void handleTest()}
+            type="button"
+          >
+            {testMutation.isPending ? "Testing..." : "Test connection"}
+          </button>
+          <AlertDialogCancel disabled={isPending} type="button">
+            Cancel
+          </AlertDialogCancel>
+          <AlertDialogAction
+            disabled={!canSave}
+            onClick={() => void handleSave()}
+            type="button"
+          >
+            {saveMutation.isPending || keyMutation.isPending ? "Saving..." : "Save"}
+          </AlertDialogAction>
+        </AlertDialogFooter>
+      </AlertDialogContent>
+    </AlertDialog>
+  );
+}
+
+export { LlmSettingsModal };
+export type { LlmSettingsModalProps };
diff --git a/src/components/ui/patch-viewer-main.tsx b/src/components/ui/patch-viewer-main.tsx
index 8db2f6c..4484e1b 100644
--- a/src/components/ui/patch-viewer-main.tsx
+++ b/src/components/ui/patch-viewer-main.tsx
@@ -1,5 +1,6 @@
-import { useEffect, useState } from "react";
+import { startTransition, useEffect, useMemo, useState } from "react";
 import type { CSSProperties } from "react";
+import { useQuery } from "@tanstack/react-query";
 import type {
   DiffLineAnnotation,
   FileDiffMetadata,
@@ -10,11 +11,18 @@ import type {
 import type { GitStatusEntry } from "@pierre/trees";
 import { FileDiff, Virtualizer } from "@pierre/diffs/react";
 import { ChangedFilesTree } from "./changed-files-tree";
+import { ChapterOverview } from "./chapter-overview";
+import { LlmSettingsModal } from "./llm-settings-modal";
+import { ResizableHandle } from "./resizable-handle";
 import { ReviewCommentEditor } from "./review-comment-editor";
 import { ReviewThreadCard } from "./review-thread-card";
 import { OuterworldAttribution } from "./outerworld-attribution";
-import { usePullRequestReviewCommentMutations } from "../../hooks/use-github-queries";
+import {
+  usePullRequestChaptersMutation,
+  usePullRequestReviewCommentMutations,
+} from "../../hooks/use-github-queries";
 import { useDiffNavigator } from "../../hooks/use-diff-navigator";
+import { useResizablePanelGroup } from "../../hooks/use-resizable-panel-group";
 import {
   getFileReviewThreadsForPath,
   isActiveReviewThread,
@@ -24,7 +32,16 @@ import {
   type ReviewThread,
   type ReviewThreadAnnotation,
 } from "../../lib/review-threads";
-import type { FileStatsEntry, ReviewCommentSide } from "../../types/github";
+import { llmSettingsQueryOptions } from "../../queries/llm";
+import type {
+  ChapterReviewFocus,
+  ChapterReviewStep,
+  FileStatsEntry,
+  PullRequestChapter,
+  PullRequestChapterFile,
+  PullRequestChapters,
+  ReviewCommentSide,
+} from "../../types/github";
 
 const VIRTUALIZER_CONFIG: Partial<VirtualizerConfig> = {
   overscrollSize: 1200,
@@ -71,9 +88,16 @@ type DraftReviewCommentAnnotation = {
   kind: "draft";
 };
 
+type AiHunkNoteAnnotation = {
+  kind: "ai-note";
+  title: string;
+  detail: string;
+};
+
 type PatchLineAnnotation =
   | ReviewThreadAnnotation
-  | DraftReviewCommentAnnotation;
+  | DraftReviewCommentAnnotation
+  | AiHunkNoteAnnotation;
 
 type PatchViewerMainProps = {
   selectedPrKey: string | null;
@@ -87,6 +111,9 @@ type PatchViewerMainProps = {
   reviewThreads: ReviewThread[];
   isReviewThreadsLoading: boolean;
   reviewThreadsError: string;
+  chapters: PullRequestChapters | null;
+  isChaptersLoading: boolean;
+  chaptersError: string;
   parsedPatch: {
     fileDiffs: FileDiffMetadata[];
     parseError: string;
@@ -123,6 +150,138 @@ function getSelectedLineLabel(target: DraftReviewCommentTarget | null) {
   return `Lines ${startLine}-${endLine}`;
 }
 
+function formatCompactCount(value: number) {
+  if (value >= 1000) return `${(value / 1000).toFixed(1).replace(/\.0$/, "")}k`;
+  return String(value);
+}
+
+function findChapterFile(
+  chapter: PullRequestChapter | null,
+  path: string,
+): PullRequestChapterFile | null {
+  if (!chapter) return null;
+
+  const normalizedPath = normalizePath(path);
+  return (
+    chapter.files.find((file) => normalizePath(file.path) === normalizedPath) ??
+    null
+  );
+}
+
+function getFirstChapterPath(
+  chapter: PullRequestChapter | null,
+  step: ChapterReviewStep | null = null,
+) {
+  if (!chapter) return null;
+  return step?.files[0] ?? chapter.files[0]?.path ?? null;
+}
+
+function findChapterForFocus(
+  chapters: PullRequestChapters | null,
+  focus: ChapterReviewFocus,
+) {
+  if (!chapters) return null;
+
+  if (focus.path) {
+    const normalizedFocusPath = normalizePath(focus.path);
+    const fileMatch = chapters.chapters.find((chapter) =>
+      chapter.files.some(
+        (file) => normalizePath(file.path) === normalizedFocusPath,
+      ),
+    );
+    if (fileMatch) return fileMatch;
+
+    const riskPathMatch = chapters.chapters.find((chapter) =>
+      chapter.risks.some(
+        (risk) =>
+          risk.path !== null && normalizePath(risk.path) === normalizedFocusPath,
+      ),
+    );
+    if (riskPathMatch) return riskPathMatch;
+  }
+
+  const normalizedFocusTitle = focus.title.trim().toLowerCase();
+  return (
+    chapters.chapters.find((chapter) =>
+      chapter.risks.some(
+        (risk) => risk.title.trim().toLowerCase() === normalizedFocusTitle,
+      ),
+    ) ??
+    chapters.chapters.find((chapter) =>
+      chapter.title.toLowerCase().includes(normalizedFocusTitle),
+    ) ??
+    chapters.chapters[0] ??
+    null
+  );
+}
+
+function getFirstChangedAnnotationTarget(fileDiff: FileDiffMetadata) {
+  for (const hunk of fileDiff.hunks) {
+    for (const content of hunk.hunkContent) {
+      if (content.type !== "change") continue;
+
+      if (content.additions > 0) {
+        return {
+          side: "additions" as const,
+          lineNumber:
+            hunk.additionStart +
+            Math.max(0, content.additionLineIndex - hunk.additionLineIndex),
+        };
+      }
+
+      if (content.deletions > 0) {
+        return {
+          side: "deletions" as const,
+          lineNumber:
+            hunk.deletionStart +
+            Math.max(0, content.deletionLineIndex - hunk.deletionLineIndex),
+        };
+      }
+    }
+  }
+
+  return null;
+}
+
+function getRiskForPath(chapter: PullRequestChapter, path: string) {
+  const normalizedPath = normalizePath(path);
+  return (
+    chapter.risks.find(
+      (risk) =>
+        risk.path !== null && normalizePath(risk.path) === normalizedPath,
+    ) ??
+    chapter.risks[0] ??
+    null
+  );
+}
+
+function buildAiHunkNoteAnnotation(
+  fileDiff: FileDiffMetadata,
+  chapter: PullRequestChapter | null,
+): DiffLineAnnotation<AiHunkNoteAnnotation> | null {
+  if (!chapter) return null;
+
+  const target = getFirstChangedAnnotationTarget(fileDiff);
+  if (!target) return null;
+
+  const chapterFile = findChapterFile(chapter, fileDiff.name);
+  const risk = getRiskForPath(chapter, fileDiff.name);
+  const detail =
+    chapterFile?.reason ||
+    risk?.detail ||
+    chapter.summary ||
+    "AI grouped this hunk into the selected review chapter.";
+
+  return {
+    ...target,
+    metadata: {
+      kind: "ai-note",
+      title: risk?.title ?? chapter.title,
+      detail,
+    },
+  };
+}
+
 type ReviewThreadsPanelProps = {
   threads: ReviewThread[];
   isLoading: boolean;
@@ -243,6 +402,9 @@ function PatchViewerMain({
   reviewThreads,
   isReviewThreadsLoading,
   reviewThreadsError,
+  chapters,
+  isChaptersLoading,
+  chaptersError,
   parsedPatch,
   fileStats,
   gitStatus,
@@ -250,6 +412,40 @@ function PatchViewerMain({
   const [draftCommentTarget, setDraftCommentTarget] =
     useState<DraftReviewCommentTarget | null>(null);
   const [draftCommentError, setDraftCommentError] = useState("");
+  const [isLlmSettingsOpen, setIsLlmSettingsOpen] = useState(false);
+  const [selectedChapterId, setSelectedChapterId] = useState<string | null>(
+    null,
+  );
+  const [selectedReviewStepIndex, setSelectedReviewStepIndex] = useState<
+    number | null
+  >(null);
+  const [completedChapterIds, setCompletedChapterIds] = useState<Set<string>>(
+    () => new Set(),
+  );
+  const chapterPanelLayout = useResizablePanelGroup({
+    id: "chapter-overview",
+    orientation: "vertical",
+    controlledPanel: "first",
+    defaultSize: 28,
+    minSize: 14,
+    maxSize: 44,
+  });
+  const reviewSidePanelLayout = useResizablePanelGroup({
+    id: "review-side-panel",
+    orientation: "horizontal",
+    controlledPanel: "second",
+    defaultSize: 33,
+    minSize: 22,
+    maxSize: 50,
+  });
+  const fileCommentsPanelLayout = useResizablePanelGroup({
+    id: "file-comments",
+    orientation: "vertical",
+    controlledPanel: "first",
+    defaultSize: 60,
+    minSize: 35,
+    maxSize: 78,
+  });
   const hasSelection = selectedPrKey !== null;
   const shouldShowCommentsPanel =
     hasSelection &&
@@ -275,15 +471,180 @@ function PatchViewerMain({
         }
       : null,
   );
+  const chapterMutation = usePullRequestChaptersMutation(
+    selectedPatch
+      ? {
+          repo: selectedPatch.repo,
+          number: selectedPatch.number,
+          headSha: selectedPatch.headSha,
+        }
+      : null,
+  );
+  const llmSettingsQuery = useQuery({
+    ...llmSettingsQueryOptions(),
+    enabled: hasSelection,
+  });
+  const llmSettings = llmSettingsQuery.data ?? null;
+
+  const selectedChapter = useMemo(
+    () =>
+      chapters?.chapters.find((chapter) => chapter.id === selectedChapterId) ??
+      null,
+    [chapters, selectedChapterId],
+  );
+  const selectedReviewStep = useMemo(() => {
+    if (!selectedChapter || selectedReviewStepIndex === null) {
+      return null;
+    }
+
+    return selectedChapter.reviewSteps[selectedReviewStepIndex] ?? null;
+  }, [selectedChapter, selectedReviewStepIndex]);
+  const selectedChapterFileSet = useMemo(() => {
+    if (!selectedChapter) return null;
+    const reviewStepFiles = selectedReviewStep?.files ?? [];
+    const visibleFiles =
+      reviewStepFiles.length > 0
+        ? reviewStepFiles
+        : selectedChapter.files.map((file) => file.path);
+
+    return new Set(visibleFiles.map((file) => normalizePath(file)));
+  }, [selectedChapter, selectedReviewStep]);
+  const visibleChangedFiles = useMemo(() => {
+    if (!selectedChapterFileSet) return changedFiles;
+    return changedFiles.filter((path) =>
+      selectedChapterFileSet.has(normalizePath(path)),
+    );
+  }, [changedFiles, selectedChapterFileSet]);
+  const visibleFileDiffs = useMemo(() => {
+    if (!selectedChapterFileSet) return parsedPatch.fileDiffs;
+    return parsedPatch.fileDiffs.filter((fileDiff) =>
+      selectedChapterFileSet.has(normalizePath(fileDiff.name)),
+    );
+  }, [parsedPatch.fileDiffs, selectedChapterFileSet]);
+  const aiNoteFilePaths = useMemo(() => {
+    if (!selectedChapter) return new Set<string>();
+
+    const notePaths = new Set<string>();
+    for (const fileDiff of visibleFileDiffs) {
+      if (!buildAiHunkNoteAnnotation(fileDiff, selectedChapter)) {
+        continue;
+      }
+
+      notePaths.add(normalizePath(fileDiff.name));
+      if (notePaths.size >= 2) break;
+    }
+
+    return notePaths;
+  }, [selectedChapter, visibleFileDiffs]);
+  const selectedReviewLabel =
+    selectedReviewStep?.title ?? selectedChapter?.title ?? null;
+  const changedFilesContext = selectedChapter
+    ? {
+        title: selectedReviewStep
+          ? `Chapter files: ${selectedReviewStep.title}`
+          : `Chapter files: ${selectedChapter.title}`,
+        detail:
+          selectedReviewStep?.detail ||
+          selectedChapter.summary ||
+          "Showing only files matched to the selected AI chapter.",
+      }
+    : null;
 
   useEffect(() => {
     setDraftCommentTarget(null);
     setDraftCommentError("");
+    setSelectedChapterId(null);
+    setSelectedReviewStepIndex(null);
+    setCompletedChapterIds(new Set());
   }, [selectedPrKey]);
 
+  useEffect(() => {
+    if (!selectedChapterId) return;
+    if (chapters?.chapters.some((chapter) => chapter.id === selectedChapterId)) {
+      return;
+    }
+
+    setSelectedChapterId(null);
+    setSelectedReviewStepIndex(null);
+  }, [chapters, selectedChapterId]);
+
+  useEffect(() => {
+    if (selectedReviewStepIndex === null) return;
+    if (
+      selectedChapter &&
+      selectedReviewStepIndex < selectedChapter.reviewSteps.length
+    ) {
+      return;
+    }
+
+    setSelectedReviewStepIndex(null);
+  }, [selectedChapter, selectedReviewStepIndex]);
+
   useEffect(() => {
     navigator.actions.notifyDiffContentChanged();
-  }, [navigator.actions, parsedPatch.fileDiffs, reviewThreadsByFile]);
+  }, [
+    navigator.actions,
+    parsedPatch.fileDiffs,
+    reviewThreadsByFile,
+    selectedChapterFileSet,
+  ]);
+
+  function handleSelectChapter(chapterId: string | null) {
+    const nextChapter =
+      chapters?.chapters.find((chapter) => chapter.id === chapterId) ?? null;
+
+    startTransition(() => {
+      setSelectedChapterId(chapterId);
+      setSelectedReviewStepIndex(null);
+    });
+
+    const firstPath = getFirstChapterPath(nextChapter);
+    if (firstPath) {
+      navigator.tree.onSelectFile(firstPath);
+    }
+  }
+
+  function handleSelectReviewStep(stepIndex: number | null) {
+    const nextStep =
+      selectedChapter && stepIndex !== null
+        ? selectedChapter.reviewSteps[stepIndex] ?? null
+        : null;
+
+    startTransition(() => {
+      setSelectedReviewStepIndex(stepIndex);
+    });
+
+    const firstPath = getFirstChapterPath(selectedChapter, nextStep);
+    if (firstPath) {
+      navigator.tree.onSelectFile(firstPath);
+    }
+  }
+
+  function handleSelectReviewFocus(focus: ChapterReviewFocus) {
+    const chapter = findChapterForFocus(chapters, focus);
+    const firstPath = focus.path ?? getFirstChapterPath(chapter);
+
+    startTransition(() => {
+      setSelectedChapterId(chapter?.id ?? null);
+      setSelectedReviewStepIndex(null);
+    });
+
+    if (firstPath) {
+      navigator.tree.onSelectFile(firstPath);
+    }
+  }
+
+  function handleToggleChapterComplete(chapterId: string) {
+    setCompletedChapterIds((current) => {
+      const next = new Set(current);
+      if (next.has(chapterId)) {
+        next.delete(chapterId);
+      } else {
+        next.add(chapterId);
+      }
+      return next;
+    });
+  }
 
   function openLineCommentDraft(path: string, range: SelectedLineRange) {
     const startSide = range.side ?? range.endSide;
@@ -432,6 +793,25 @@ function PatchViewerMain({
       );
     }
 
+    if (
+      "kind" in annotation.metadata &&
+      annotation.metadata.kind === "ai-note"
+    ) {
+      return (
+        <div className="w-full max-w-full min-w-0 overflow-hidden rounded-xl border border-amber-200 bg-amber-50 px-3 py-2 text-sm text-amber-900 shadow-sm dark:border-amber-900/50 dark:bg-amber-950/30 dark:text-amber-200">
+          <div className="mb-1 flex min-w-0 flex-wrap items-center gap-2 text-xs font-semibold uppercase tracking-wide">
+            <span>AI note</span>
+            <span className="min-w-0 break-words text-amber-700 dark:text-amber-300">
+              {annotation.metadata.title}
+            </span>
+          </div>
+          <p className="whitespace-normal break-words leading-5 [overflow-wrap:anywhere]">
+            {annotation.metadata.detail}
+          </p>
+        </div>
+      );
+    }
+
     const threadAnnotation = annotation.metadata as ReviewThreadAnnotation;
 
     return (
@@ -462,15 +842,63 @@ function PatchViewerMain({
   }
 
   return (
-    <main className="h-full min-h-0 min-w-0 pl-0">
-      <section className="flex h-full min-h-0 min-w-0 flex-col overflow-hidden bg-surface">
-        <div className="flex min-h-0 min-w-0 flex-1">
-          <div className="min-h-0 min-w-[30%] flex-1">
-            <Virtualizer
-              className="relative h-full min-h-0 min-w-0 overflow-y-auto scrollbar-hidden"
-              config={VIRTUALIZER_CONFIG}
-              contentClassName="flex min-h-full flex-col bg-white dark:bg-surface"
-            >
+    <>
+      <main className="h-full min-h-0 min-w-0 pl-0">
+        <div
+          ref={chapterPanelLayout.containerRef}
+          className="flex h-full min-h-0 min-w-0 flex-col overflow-hidden bg-surface"
+        >
+          <div
+            className="min-h-[128px] shrink-0 overflow-hidden"
+            style={chapterPanelLayout.panelStyle}
+          >
+            <ChapterOverview
+              chapters={chapters}
+              error={chaptersError}
+              generationError={
+                chapterMutation.error instanceof Error
+                  ? chapterMutation.error.message
+                  : chapterMutation.error
+                    ? String(chapterMutation.error)
+                    : ""
+              }
+              isGenerating={chapterMutation.isPending}
+              isLoading={isChaptersLoading}
+              completedChapterIds={completedChapterIds}
+              onGenerate={() => void chapterMutation.mutate()}
+              onOpenSettings={() => setIsLlmSettingsOpen(true)}
+              onSelectChapter={handleSelectChapter}
+              onSelectReviewFocus={handleSelectReviewFocus}
+              onSelectReviewStep={handleSelectReviewStep}
+              onToggleChapterComplete={handleToggleChapterComplete}
+              reviewThreadsByFile={reviewThreadsByFile}
+              selectedChapterId={selectedChapterId}
+              selectedReviewStepIndex={selectedReviewStepIndex}
+              settings={llmSettings}
+              settingsError={
+                llmSettingsQuery.error instanceof Error
+                  ? llmSettingsQuery.error.message
+                  : llmSettingsQuery.error
+                    ? String(llmSettingsQuery.error)
+                    : ""
+              }
+            />
+          </div>
+          <ResizableHandle
+            {...chapterPanelLayout.handleProps}
+            label="Resize AI summary panel"
+            orientation="vertical"
+          />
+          <div
+            ref={reviewSidePanelLayout.containerRef}
+            className="flex min-h-0 min-w-0 flex-1"
+          >
+            <div className="min-h-0 min-w-[30%] flex-1">
+              <Virtualizer
+                className="relative h-full min-h-0 min-w-0 overflow-y-auto scrollbar-hidden"
+                config={VIRTUALIZER_CONFIG}
+                contentClassName="flex min-h-full flex-col bg-white dark:bg-surface"
+              >
               {!selectedPrKey && !isPatchLoading ? (
                 <div className="flex min-h-[50vh] flex-col items-center justify-center gap-2 px-6 py-10 text-center md:min-h-full">
                   <strong>Select a pull request.</strong>
@@ -506,6 +934,28 @@ function PatchViewerMain({
 
               {!isPatchLoading && !patchError && selectedPatch ? (
                 <div className="flex min-h-[50vh] flex-col md:min-h-full h-full">
+                  {selectedChapter ? (
+                    <div className="sticky top-0 z-20 border-b border-ink-200 bg-surface/95 px-4 py-2 backdrop-blur">
+                      <div className="flex flex-wrap items-center justify-between gap-2 text-sm">
+                        <p className="min-w-0 truncate font-medium text-ink-900">
+                          Reviewing: {selectedReviewLabel}
+                        </p>
+                        <p className="shrink-0 font-mono text-xs font-semibold">
+                          <span className="text-emerald-600 dark:text-emerald-300">
+                            +{formatCompactCount(selectedChapter.additions)}
+                          </span>{" "}
+                          <span className="text-red-600 dark:text-red-300">
+                            -{formatCompactCount(selectedChapter.deletions)}
+                          </span>
+                        </p>
+                      </div>
+                      <p className="mt-0.5 truncate text-xs text-ink-500">
+                        {visibleChangedFiles.length} matched files - AI notes are
+                        limited to the highest-signal hunks.
+                      </p>
+                    </div>
+                  ) : null}
+
                   {parsedPatch.parseError ? (
                     <div className="flex min-h-[50vh] items-center justify-center px-6 py-10 text-center text-danger-600 md:min-h-full">
                       {parsedPatch.parseError}
@@ -514,9 +964,13 @@ function PatchViewerMain({
                     <pre className="m-0 overflow-auto scrollbar-hidden whitespace-pre-wrap break-words p-5">
                       {selectedPatch.patch}
                     </pre>
+                  ) : visibleFileDiffs.length === 0 ? (
+                    <div className="flex min-h-[50vh] items-center justify-center px-6 py-10 text-center text-sm text-ink-500 md:min-h-full">
+                      No parsed diffs matched this AI summary.
+                    </div>
                   ) : (
                     <div className="flex flex-col bg-white dark:bg-surface">
-                      {parsedPatch.fileDiffs.map((fileDiff) => {
+                      {visibleFileDiffs.map((fileDiff) => {
                         const fileReviewThreads = getFileReviewThreadsForPath(
                           reviewThreadsByFile,
                           fileDiff.name,
@@ -547,17 +1001,32 @@ function PatchViewerMain({
                           fileDraft = draftCommentTarget;
                         }
 
+                        const aiHunkNote =
+                          selectedChapter &&
+                          aiNoteFilePaths.has(normalizedFilePath)
+                            ? buildAiHunkNoteAnnotation(
+                                fileDiff,
+                                selectedChapter,
+                              )
+                            : null;
+                        const baseLineAnnotations: DiffLineAnnotation<PatchLineAnnotation>[] =
+                          aiHunkNote
+                            ? [
+                                ...fileReviewThreads.lineAnnotations,
+                                aiHunkNote,
+                              ]
+                            : fileReviewThreads.lineAnnotations;
                         const lineAnnotations: DiffLineAnnotation<PatchLineAnnotation>[] =
                           lineDraft
                             ? [
-                                ...fileReviewThreads.lineAnnotations,
+                                ...baseLineAnnotations,
                                 {
                                   side: toSelectionSide(lineDraft.side),
                                   lineNumber: lineDraft.line,
                                   metadata: { kind: "draft" },
                                 },
                               ]
-                            : fileReviewThreads.lineAnnotations;
+                            : baseLineAnnotations;
                         const selectedLines: SelectedLineRange | null =
                           lineDraft
                             ? {
@@ -672,50 +1141,79 @@ function PatchViewerMain({
                   )}
                 </div>
               ) : null}
-            </Virtualizer>
-          </div>
-          <div className="min-h-0 w-1/3 min-w-[15%] shrink-0">
+              </Virtualizer>
+            </div>
+            <ResizableHandle
+              {...reviewSidePanelLayout.handleProps}
+              label="Resize file tree and comments"
+              orientation="horizontal"
+            />
             <div
-              className={cx(
-                "flex h-full min-h-0 min-w-0 flex-col",
-                shouldShowCommentsPanel && "divide-y divide-ink-200",
-              )}
+              className="min-h-0 min-w-[260px] shrink-0"
+              style={reviewSidePanelLayout.panelStyle}
             >
               <div
+                ref={fileCommentsPanelLayout.containerRef}
                 className={cx(
-                  "min-h-0 overflow-hidden",
-                  shouldShowCommentsPanel ? "flex-[3]" : "flex-1",
+                  "flex h-full min-h-0 min-w-0 flex-col",
+                  shouldShowCommentsPanel && "bg-surface",
                 )}
               >
-                <ChangedFilesTree
-                  error={changedFilesError}
-                  files={changedFiles}
-                  hasSelection={hasSelection}
-                  isDark={isDark}
-                  isLoading={isChangedFilesLoading}
-                  onSelectFile={navigator.tree.onSelectFile}
-                  selectedFilePath={navigator.tree.selectedFilePath}
-                  showContainer={false}
-                  fileStats={fileStats}
-                  gitStatus={gitStatus}
-                />
-              </div>
-
-              {shouldShowCommentsPanel ? (
-                <div className="min-h-0 flex-[2] overflow-y-auto scrollbar-hidden bg-surface">
-                  <ReviewThreadsPanel
-                    threads={reviewThreads}
-                    isLoading={isReviewThreadsLoading}
-                    error={reviewThreadsError}
+                <div
+                  style={
+                    shouldShowCommentsPanel
+                      ? fileCommentsPanelLayout.panelStyle
+                      : undefined
+                  }
+                  className={cx(
+                    "min-h-0 overflow-hidden",
+                    shouldShowCommentsPanel
+                      ? "min-h-[180px] shrink-0"
+                      : "flex-1",
+                  )}
+                >
+                  <ChangedFilesTree
+                    error={changedFilesError}
+                    files={visibleChangedFiles}
                     hasSelection={hasSelection}
+                    isDark={isDark}
+                    isLoading={isChangedFilesLoading}
+                    onSelectFile={navigator.tree.onSelectFile}
+                    selectedFilePath={navigator.tree.selectedFilePath}
+                    showContainer={false}
+                    fileStats={fileStats}
+                    gitStatus={gitStatus}
+                    chapterContext={changedFilesContext}
                   />
                 </div>
-              ) : null}
+
+                {shouldShowCommentsPanel ? (
+                  <>
+                    <ResizableHandle
+                      {...fileCommentsPanelLayout.handleProps}
+                      label="Resize files and comments"
+                      orientation="vertical"
+                    />
+                    <div className="min-h-[140px] flex-1 overflow-y-auto scrollbar-hidden bg-surface">
+                      <ReviewThreadsPanel
+                        threads={reviewThreads}
+                        isLoading={isReviewThreadsLoading}
+                        error={reviewThreadsError}
+                        hasSelection={hasSelection}
+                      />
+                    </div>
+                  </>
+                ) : null}
+              </div>
             </div>
           </div>
         </div>
-      </section>
-    </main>
+      </main>
+      <LlmSettingsModal
+        onOpenChange={setIsLlmSettingsOpen}
+        open={isLlmSettingsOpen}
+      />
+    </>
   );
 }
 
diff --git a/src/components/ui/repo-sidebar.tsx b/src/components/ui/repo-sidebar.tsx
index c9b6b73..9cdb8a0 100644
--- a/src/components/ui/repo-sidebar.tsx
+++ b/src/components/ui/repo-sidebar.tsx
@@ -1,8 +1,8 @@
 import { MoonIcon, PlusIcon, SunIcon } from "@heroicons/react/20/solid";
-import { getCurrentWindow } from "@tauri-apps/api/window";
 import { Accordion } from "./accordion";
 import { AppUpdater } from "./app-updater";
 import { RepoSidebarItem, type PullRequestSummary } from "./repo-sidebar-item";
+import { WindowDragRegion } from "./window-drag-region";
 import type { RepoSummary } from "../../types/github";
 
 type RepoSidebarProps = {
@@ -34,23 +34,9 @@ function RepoSidebar({
   onRemovePr,
   onRepoOpenChange,
 }: RepoSidebarProps) {
-  const appWindow = getCurrentWindow();
-
   return (
     <aside className="flex h-full min-h-0 min-w-0 flex-col overflow-hidden border-ink-300 bg-canvas md:border-b-0">
-      <div
-        aria-hidden="true"
-        className="h-8 shrink-0 cursor-grab bg-canvas active:cursor-grabbing"
-        data-tauri-drag-region
-        onMouseDown={(event) => {
-          if (event.button !== 0) return;
-          if (event.detail === 2) {
-            void appWindow.toggleMaximize();
-            return;
-          }
-          void appWindow.startDragging();
-        }}
-      />
+      <WindowDragRegion className="bg-canvas" />
       <div className="sticky top-0 z-10 flex w-full items-center gap-2.5 border-b border-neutral-300 dark:border-neutral-700 bg-canvas px-3 py-2.5 text-sm font-medium">
         Repositories
         <div className="ml-auto flex items-center gap-1.5">
diff --git a/src/components/ui/resizable-handle.tsx b/src/components/ui/resizable-handle.tsx
new file mode 100644
index 0000000..217a2d3
--- /dev/null
+++ b/src/components/ui/resizable-handle.tsx
@@ -0,0 +1,49 @@
+import type {
+  ResizableHandleInteractionProps,
+  ResizeOrientation,
+} from "../../hooks/use-resizable-panel-group";
+
+type ResizableHandleProps = ResizableHandleInteractionProps & {
+  orientation: ResizeOrientation;
+  label: string;
+  className?: string;
+};
+
+function cx(...classes: Array<string | undefined | false>) {
+  return classes.filter(Boolean).join(" ");
+}
+
+function ResizableHandle({
+  orientation,
+  label,
+  className,
+  ...handleProps
+}: ResizableHandleProps) {
+  return (
+    <div
+      {...handleProps}
+      aria-label={label}
+      className={cx(
+        "group relative z-20 shrink-0 touch-none outline-none",
+        "focus-visible:ring-2 focus-visible:ring-ink-400 focus-visible:ring-offset-0",
+        orientation === "horizontal"
+          ? "w-2 cursor-col-resize"
+          : "h-2 cursor-row-resize",
+        className,
+      )}
+    >
+      <span
+        aria-hidden="true"
+        className={cx(
+          "absolute rounded-full bg-ink-300 opacity-70 transition group-hover:bg-ink-500 group-hover:opacity-100 group-focus-visible:bg-ink-500 group-active:bg-ink-600",
+          orientation === "horizontal"
+            ? "inset-y-2 left-1/2 w-px -translate-x-1/2"
+            : "inset-x-2 top-1/2 h-px -translate-y-1/2",
+        )}
+      />
+    </div>
+  );
+}
+
+export { ResizableHandle };
+export type { ResizableHandleProps };
diff --git a/src/components/ui/window-drag-region.tsx b/src/components/ui/window-drag-region.tsx
new file mode 100644
index 0000000..bbbfe30
--- /dev/null
+++ b/src/components/ui/window-drag-region.tsx
@@ -0,0 +1,35 @@
+import { getCurrentWindow } from "@tauri-apps/api/window";
+
+type WindowDragRegionProps = {
+  className?: string;
+};
+
+function cx(...classes: Array<string | undefined | false>) {
+  return classes.filter(Boolean).join(" ");
+}
+
+function WindowDragRegion({ className }: WindowDragRegionProps) {
+  const appWindow = getCurrentWindow();
+
+  return (
+    <div
+      aria-hidden="true"
+      className={cx(
+        "h-8 shrink-0 cursor-grab active:cursor-grabbing",
+        className,
+      )}
+      data-tauri-drag-region
+      onMouseDown={(event) => {
+        if (event.button !== 0) return;
+        if (event.detail === 2) {
+          void appWindow.toggleMaximize();
+          return;
+        }
+        void appWindow.startDragging();
+      }}
+    />
+  );
+}
+
+export { WindowDragRegion };
+export type { WindowDragRegionProps };
diff --git a/src/hooks/use-github-queries.ts b/src/hooks/use-github-queries.ts
index e2b949f..76b73b1 100644
--- a/src/hooks/use-github-queries.ts
+++ b/src/hooks/use-github-queries.ts
@@ -19,6 +19,7 @@ import {
   githubKeys,
   initialReposQueryOptions,
   replyToPullRequestReviewComment,
+  regeneratePullRequestChapters,
   savedReposQueryOptions,
   searchReposQueryOptions,
   trackedPullRequestListQueryOptions,
@@ -28,6 +29,7 @@ import {
 import type {
   CreatePullRequestReviewCommentInput,
   PrPatch,
+  PullRequestChapters,
   PullRequestSummary,
   ReplyToPullRequestReviewCommentInput,
   RepoSummary,
@@ -304,10 +306,30 @@ function useSelectedPullRequestData(selectedPr: SelectedPullRequest | null) {
     enabled: selectedPr !== null,
   });
 
+  const chaptersQuery = useQuery({
+    queryKey: selectedPr
+      ? githubKeys.pullRequestChapters(selectedPr)
+      : githubKeys.pullRequestChaptersIdle(),
+    queryFn: () => {
+      if (!selectedPr) {
+        throw new Error("No pull request selected");
+      }
+
+      return invoke<PullRequestChapters | null>("get_pull_request_chapters", {
+        repo: selectedPr.repo,
+        number: selectedPr.number,
+        headSha: selectedPr.headSha,
+      });
+    },
+    enabled: selectedPr !== null,
+  });
+
   const selectedPatch = (selectedPatchQuery.data as PrPatch | undefined) ?? null;
   const changedFiles = (changedFilesQuery.data as string[] | undefined) ?? [];
   const reviewThreads =
     (reviewThreadsQuery.data as ReviewThread[] | undefined) ?? [];
+  const chapters =
+    (chaptersQuery.data as PullRequestChapters | null | undefined) ?? null;
 
   const isPatchLoading =
     selectedPr !== null &&
@@ -321,10 +343,17 @@ function useSelectedPullRequestData(selectedPr: SelectedPullRequest | null) {
     selectedPr !== null &&
     (reviewThreadsQuery.isPending ||
       (reviewThreadsQuery.isFetching && !reviewThreadsQuery.data));
+  const isChaptersLoading =
+    selectedPr !== null &&
+    (chaptersQuery.isPending ||
+      (chaptersQuery.isFetching && chaptersQuery.data === undefined));
 
   return {
+    chapters,
+    chaptersError: getErrorMessage(chaptersQuery.error),
     changedFiles,
     changedFilesError: getErrorMessage(changedFilesQuery.error),
+    isChaptersLoading,
     isChangedFilesLoading,
     isPatchLoading,
     isReviewThreadsLoading,
@@ -335,6 +364,29 @@ function useSelectedPullRequestData(selectedPr: SelectedPullRequest | null) {
   };
 }
 
+function usePullRequestChaptersMutation(
+  selectedPr: SelectedPullRequest | null,
+) {
+  const queryClient = useQueryClient();
+
+  return useMutation({
+    mutationFn: () => {
+      if (!selectedPr) {
+        throw new Error("No pull request selected");
+      }
+
+      return regeneratePullRequestChapters(selectedPr);
+    },
+    onSuccess: (chapters) => {
+      if (!selectedPr) return;
+      queryClient.setQueryData(
+        githubKeys.pullRequestChapters(selectedPr),
+        chapters,
+      );
+    },
+  });
+}
+
 function usePullRequestReviewCommentMutations(
   selectedPr: SelectedPullRequest | null,
 ) {
@@ -505,6 +557,7 @@ function usePullRequestReviewCommentMutations(
 
 export {
   getErrorMessage,
+  usePullRequestChaptersMutation,
   usePullRequestReviewCommentMutations,
   useRepoPickerRepos,
   useSavedRepos,
diff --git a/src/hooks/use-resizable-panel-group.ts b/src/hooks/use-resizable-panel-group.ts
new file mode 100644
index 0000000..4625daf
--- /dev/null
+++ b/src/hooks/use-resizable-panel-group.ts
@@ -0,0 +1,323 @@
+import {
+  useCallback,
+  useEffect,
+  useMemo,
+  useRef,
+  useState,
+  type CSSProperties,
+  type KeyboardEventHandler,
+  type PointerEventHandler,
+  type RefObject,
+} from "react";
+
+type ResizeOrientation = "horizontal" | "vertical";
+type ResizablePanel = "first" | "second";
+
+type UseResizablePanelGroupOptions = {
+  id: string;
+  orientation: ResizeOrientation;
+  controlledPanel?: ResizablePanel;
+  defaultSize: number;
+  minSize: number;
+  maxSize: number;
+  step?: number;
+};
+
+type ResizableHandleInteractionProps = {
+  role: "separator";
+  tabIndex: number;
+  "aria-orientation": "horizontal" | "vertical";
+  "aria-valuemin": number;
+  "aria-valuemax": number;
+  "aria-valuenow": number;
+  "aria-valuetext": string;
+  onDoubleClick: () => void;
+  onKeyDown: KeyboardEventHandler<HTMLDivElement>;
+  onPointerDown: PointerEventHandler<HTMLDivElement>;
+};
+
+type UseResizablePanelGroupResult = {
+  containerRef: RefObject<HTMLDivElement | null>;
+  size: number;
+  panelStyle: CSSProperties;
+  handleProps: ResizableHandleInteractionProps;
+  reset: () => void;
+};
+
+const PANEL_LAYOUT_STORAGE_KEY = "rudu.panel-layout.v1";
+
+function clamp(value: number, min: number, max: number) {
+  return Math.min(max, Math.max(min, value));
+}
+
+function isPlainRecord(value: unknown): value is Record<string, unknown> {
+  return typeof value === "object" && value !== null && !Array.isArray(value);
+}
+
+function readStoredSizes() {
+  if (typeof window === "undefined") {
+    return {};
+  }
+
+  try {
+    const rawValue = window.localStorage.getItem(PANEL_LAYOUT_STORAGE_KEY);
+    if (!rawValue) {
+      return {};
+    }
+
+    const parsedValue: unknown = JSON.parse(rawValue);
+    if (!isPlainRecord(parsedValue)) {
+      return {};
+    }
+
+    const sizes: Record<string, number> = {};
+    for (const [key, value] of Object.entries(parsedValue)) {
+      if (typeof value === "number" && Number.isFinite(value)) {
+        sizes[key] = value;
+      }
+    }
+
+    return sizes;
+  } catch {
+    return {};
+  }
+}
+
+function writeStoredSize(id: string, size: number) {
+  if (typeof window === "undefined") {
+    return;
+  }
+
+  try {
+    const nextSizes = {
+      ...readStoredSizes(),
+      [id]: size,
+    };
+    window.localStorage.setItem(
+      PANEL_LAYOUT_STORAGE_KEY,
+      JSON.stringify(nextSizes),
+    );
+  } catch {
+    // Storage can be unavailable in restricted contexts; resizing still works.
+  }
+}
+
+function getInitialSize({
+  id,
+  defaultSize,
+  minSize,
+  maxSize,
+}: Pick<
+  UseResizablePanelGroupOptions,
+  "id" | "defaultSize" | "minSize" | "maxSize"
+>) {
+  const storedSize = readStoredSizes()[id];
+
+  if (
+    typeof storedSize === "number" &&
+    storedSize >= minSize &&
+    storedSize <= maxSize
+  ) {
+    return storedSize;
+  }
+
+  return clamp(defaultSize, minSize, maxSize);
+}
+
+function useResizablePanelGroup({
+  id,
+  orientation,
+  controlledPanel = "first",
+  defaultSize,
+  minSize,
+  maxSize,
+  step = 2,
+}: UseResizablePanelGroupOptions): UseResizablePanelGroupResult {
+  const containerRef = useRef<HTMLDivElement | null>(null);
+  const [size, setSize] = useState(() =>
+    getInitialSize({ id, defaultSize, minSize, maxSize }),
+  );
+
+  const dragCleanupRef = useRef<(() => void) | null>(null);
+
+  const setClampedSize = useCallback(
+    (nextSize: number) => {
+      setSize(clamp(nextSize, minSize, maxSize));
+    },
+    [maxSize, minSize],
+  );
+
+  const reset = useCallback(() => {
+    setClampedSize(defaultSize);
+  }, [defaultSize, setClampedSize]);
+
+  const getSizeFromPointer = useCallback(
+    (clientX: number, clientY: number) => {
+      const container = containerRef.current;
+      if (!container) {
+        return size;
+      }
+
+      const rect = container.getBoundingClientRect();
+      const totalSize =
+        orientation === "horizontal" ? rect.width : rect.height;
+
+      if (totalSize <= 0) {
+        return size;
+      }
+
+      const pointerOffset =
+        orientation === "horizontal"
+          ? clientX - rect.left
+          : clientY - rect.top;
+      const panelPixels =
+        controlledPanel === "first" ? pointerOffset : totalSize - pointerOffset;
+
+      return (panelPixels / totalSize) * 100;
+    },
+    [controlledPanel, orientation, size],
+  );
+
+  const onPointerDown = useCallback<PointerEventHandler<HTMLDivElement>>(
+    (event) => {
+      if (event.button !== 0) {
+        return;
+      }
+
+      event.preventDefault();
+      event.currentTarget.setPointerCapture(event.pointerId);
+      setClampedSize(getSizeFromPointer(event.clientX, event.clientY));
+
+      const root = document.documentElement;
+      const previousCursor = root.style.cursor;
+      const previousUserSelect = root.style.userSelect;
+      root.style.cursor =
+        orientation === "horizontal" ? "col-resize" : "row-resize";
+      root.style.userSelect = "none";
+
+      const handlePointerMove = (pointerEvent: PointerEvent) => {
+        setClampedSize(
+          getSizeFromPointer(pointerEvent.clientX, pointerEvent.clientY),
+        );
+      };
+
+      const cleanup = () => {
+        window.removeEventListener("pointermove", handlePointerMove);
+        window.removeEventListener("pointerup", cleanup);
+        window.removeEventListener("pointercancel", cleanup);
+        root.style.cursor = previousCursor;
+        root.style.userSelect = previousUserSelect;
+        dragCleanupRef.current = null;
+      };
+
+      dragCleanupRef.current?.();
+      dragCleanupRef.current = cleanup;
+
+      window.addEventListener("pointermove", handlePointerMove);
+      window.addEventListener("pointerup", cleanup);
+      window.addEventListener("pointercancel", cleanup);
+    },
+    [getSizeFromPointer, orientation, setClampedSize],
+  );
+
+  const onKeyDown = useCallback<KeyboardEventHandler<HTMLDivElement>>(
+    (event) => {
+      const direction =
+        orientation === "horizontal"
+          ? event.key === "ArrowLeft"
+            ? -1
+            : event.key === "ArrowRight"
+              ? 1
+              : 0
+          : event.key === "ArrowUp"
+            ? -1
+            : event.key === "ArrowDown"
+              ? 1
+              : 0;
+
+      if (direction !== 0) {
+        event.preventDefault();
+        const panelDirection = controlledPanel === "first" ? direction : -direction;
+        setClampedSize(size + panelDirection * step);
+        return;
+      }
+
+      if (event.key === "Home") {
+        event.preventDefault();
+        setClampedSize(controlledPanel === "first" ? minSize : maxSize);
+        return;
+      }
+
+      if (event.key === "End") {
+        event.preventDefault();
+        setClampedSize(controlledPanel === "first" ? maxSize : minSize);
+      }
+    },
+    [
+      controlledPanel,
+      maxSize,
+      minSize,
+      orientation,
+      setClampedSize,
+      size,
+      step,
+    ],
+  );
+
+  useEffect(() => {
+    writeStoredSize(id, size);
+  }, [id, size]);
+
+  useEffect(() => {
+    return () => {
+      dragCleanupRef.current?.();
+    };
+  }, []);
+
+  const panelStyle = useMemo<CSSProperties>(
+    () => ({ flexBasis: `${size}%` }),
+    [size],
+  );
+
+  const separatorOrientation =
+    orientation === "horizontal" ? "vertical" : "horizontal";
+
+  const handleProps = useMemo<ResizableHandleInteractionProps>(
+    () => ({
+      role: "separator",
+      tabIndex: 0,
+      "aria-orientation": separatorOrientation,
+      "aria-valuemin": minSize,
+      "aria-valuemax": maxSize,
+      "aria-valuenow": Math.round(size),
+      "aria-valuetext": `${Math.round(size)} percent`,
+      onDoubleClick: reset,
+      onKeyDown,
+      onPointerDown,
+    }),
+    [
+      maxSize,
+      minSize,
+      onKeyDown,
+      onPointerDown,
+      reset,
+      separatorOrientation,
+      size,
+    ],
+  );
+
+  return {
+    containerRef,
+    size,
+    panelStyle,
+    handleProps,
+    reset,
+  };
+}
+
+export { PANEL_LAYOUT_STORAGE_KEY, useResizablePanelGroup };
+export type {
+  ResizableHandleInteractionProps,
+  ResizeOrientation,
+  UseResizablePanelGroupOptions,
+};
diff --git a/src/queries/github.ts b/src/queries/github.ts
index 3a95cfe..f6df3b4 100644
--- a/src/queries/github.ts
+++ b/src/queries/github.ts
@@ -5,6 +5,7 @@ import type {
   CreatePullRequestReviewCommentInput,
   GhCliStatus,
   PrPatch,
+  PullRequestChapters,
   PullRequestSummary,
   ReplyToPullRequestReviewCommentInput,
   RepoSummary,
@@ -37,10 +38,14 @@ const githubKeys = {
     [...githubKeys.pullRequests(), "files", pr.repo, pr.number, pr.headSha] as const,
   pullRequestReviewThreads: (pr: SelectedPullRequest) =>
     [...githubKeys.pullRequests(), "review-threads", pr.repo, pr.number, pr.headSha] as const,
+  pullRequestChapters: (pr: SelectedPullRequest) =>
+    [...githubKeys.pullRequests(), "chapters", pr.repo, pr.number, pr.headSha] as const,
   pullRequestPatchIdle: () => [...githubKeys.pullRequests(), "patch", "idle"] as const,
   pullRequestFilesIdle: () => [...githubKeys.pullRequests(), "files", "idle"] as const,
   pullRequestReviewThreadsIdle: () =>
     [...githubKeys.pullRequests(), "review-threads", "idle"] as const,
+  pullRequestChaptersIdle: () =>
+    [...githubKeys.pullRequests(), "chapters", "idle"] as const,
 };
 
 function savedReposQueryOptions() {
@@ -147,6 +152,26 @@ function pullRequestReviewThreadsQueryOptions(pr: SelectedPullRequest) {
   });
 }
 
+function pullRequestChaptersQueryOptions(pr: SelectedPullRequest) {
+  return queryOptions({
+    queryKey: githubKeys.pullRequestChapters(pr),
+    queryFn: () =>
+      invoke<PullRequestChapters | null>("get_pull_request_chapters", {
+        repo: pr.repo,
+        number: pr.number,
+        headSha: pr.headSha,
+      }),
+  });
+}
+
+async function regeneratePullRequestChapters(pr: SelectedPullRequest) {
+  return invoke<PullRequestChapters>("regenerate_pull_request_chapters", {
+    repo: pr.repo,
+    number: pr.number,
+    headSha: pr.headSha,
+  });
+}
+
 async function createPullRequestReviewComment(
   input: CreatePullRequestReviewCommentInput,
 ) {
@@ -186,11 +211,13 @@ export {
   ghCliStatusQueryOptions,
   githubKeys,
   initialReposQueryOptions,
+  pullRequestChaptersQueryOptions,
   pullRequestCachedListQueryOptions,
   pullRequestFilesQueryOptions,
   pullRequestListQueryOptions,
   pullRequestPatchQueryOptions,
   pullRequestReviewThreadsQueryOptions,
+  regeneratePullRequestChapters,
   trackedPullRequestListQueryOptions,
   replyToPullRequestReviewComment,
   savedReposQueryOptions,
diff --git a/src/queries/llm.ts b/src/queries/llm.ts
new file mode 100644
index 0000000..9accdf4
--- /dev/null
+++ b/src/queries/llm.ts
@@ -0,0 +1,55 @@
+import { queryOptions } from "@tanstack/react-query";
+import { invoke } from "@tauri-apps/api/core";
+import type {
+  LlmProviderInfo,
+  LlmSettings,
+  SaveLlmSettingsInput,
+} from "../types/github";
+
+const llmKeys = {
+  all: ["llm"] as const,
+  providers: () => [...llmKeys.all, "providers"] as const,
+  settings: () => [...llmKeys.all, "settings"] as const,
+};
+
+function llmProvidersQueryOptions() {
+  return queryOptions({
+    queryKey: llmKeys.providers(),
+    queryFn: () => invoke<LlmProviderInfo[]>("list_llm_providers"),
+    staleTime: Infinity,
+  });
+}
+
+function llmSettingsQueryOptions() {
+  return queryOptions({
+    queryKey: llmKeys.settings(),
+    queryFn: () => invoke<LlmSettings>("get_llm_settings"),
+    staleTime: 30 * 1000,
+  });
+}
+
+async function saveLlmSettings(settings: SaveLlmSettingsInput) {
+  return invoke<LlmSettings>("save_llm_settings", { settings });
+}
+
+async function setLlmApiKey(provider: string, apiKey: string) {
+  return invoke<LlmSettings>("set_llm_api_key", { provider, apiKey });
+}
+
+async function deleteLlmApiKey(provider: string) {
+  return invoke<LlmSettings>("delete_llm_api_key", { provider });
+}
+
+async function testLlmProvider() {
+  await invoke("test_llm_provider");
+}
+
+export {
+  deleteLlmApiKey,
+  llmKeys,
+  llmProvidersQueryOptions,
+  llmSettingsQueryOptions,
+  saveLlmSettings,
+  setLlmApiKey,
+  testLlmProvider,
+};
diff --git a/src/types/github.ts b/src/types/github.ts
index 7a85560..cc1604b 100644
--- a/src/types/github.ts
+++ b/src/types/github.ts
@@ -45,6 +45,82 @@ type PrPatch = {
   patch: string;
 };
 
+type LlmProviderInfo = {
+  id: string;
+  name: string;
+  adapter: string;
+  defaultModel: string;
+  defaultBaseUrl: string | null;
+  baseUrlRequired: boolean;
+};
+
+type LlmSettings = {
+  provider: string;
+  model: string;
+  baseUrl: string | null;
+  hasApiKey: boolean;
+};
+
+type SaveLlmSettingsInput = {
+  provider: string;
+  model: string;
+  baseUrl: string | null;
+};
+
+type ChapterKeyChange = {
+  title: string;
+  detail: string;
+};
+
+type ChapterReviewFocus = {
+  title: string;
+  detail: string;
+  path: string | null;
+  severity: string | null;
+};
+
+type ChapterPrologue = {
+  summary: string;
+  keyChanges: ChapterKeyChange[];
+  reviewFocus: ChapterReviewFocus[];
+};
+
+type PullRequestChapterFile = {
+  path: string;
+  reason: string;
+  additions: number;
+  deletions: number;
+};
+
+type ChapterReviewStep = {
+  title: string;
+  detail: string;
+  files: string[];
+};
+
+type PullRequestChapter = {
+  id: string;
+  title: string;
+  summary: string;
+  files: PullRequestChapterFile[];
+  reviewSteps: ChapterReviewStep[];
+  risks: ChapterReviewFocus[];
+  additions: number;
+  deletions: number;
+};
+
+type PullRequestChapters = {
+  repo: string;
+  number: number;
+  headSha: string;
+  provider: string;
+  model: string;
+  promptVersion: string;
+  generatedAt: number;
+  prologue: ChapterPrologue;
+  chapters: PullRequestChapter[];
+};
+
 type ViewerLogin = {
   login: string;
 };
@@ -91,15 +167,25 @@ type FileStatsEntry = {
 };
 
 export type {
+  ChapterKeyChange,
+  ChapterPrologue,
+  ChapterReviewFocus,
+  ChapterReviewStep,
   CreatePullRequestReviewCommentInput,
   FileStatsEntry,
   GhCliStatus,
   GhCliStatusKind,
+  LlmProviderInfo,
+  LlmSettings,
   PrPatch,
+  PullRequestChapter,
+  PullRequestChapterFile,
+  PullRequestChapters,
   PullRequestSummary,
   ReplyToPullRequestReviewCommentInput,
   RepoSummary,
   ReviewCommentSide,
+  SaveLlmSettingsInput,
   SelectedPullRequest,
   UpdatePullRequestReviewCommentInput,
   ViewerLogin,