Fix Rust hook input deserialization for float timestamps

The Copilot CLI serializes hook input `timestamp` as a JSON float
(e.g. `1784203878038.0`). Rust's hand-authored hook input structs typed
`timestamp` as `i64`, so `serde_json::from_value` rejected the float,
`dispatch_hook` returned an error, and the session handler fell back to
an empty `{ "output": {} }` response. Hooks therefore never fired: e.g. a
preToolUse deny was dropped, the CLI executed the tool, and the replayed
conversation diverged ("No cached response" -> 500).

Other SDKs tolerate this incidentally (Go decodes `input` into `any` and
re-marshals, dropping the `.0`); Rust decodes strictly. Type the hook
input `timestamp` fields as `f64` to match the shape the runtime sends.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
Copilot-Session: ae226b7f-caf9-46f3-b8c5-b9a21c5d7951

Author: SteveSandersonMS

rust/src/hooks.rs

@@ -27,8 +27,8 @@ pub struct HookContext {
 pub struct PreToolUseInput {
     /// The runtime session ID of the session that triggered the hook.
     pub session_id: String,
-    /// Unix timestamp (ms).
-    pub timestamp: i64,
+    /// Unix timestamp in ms (the runtime serializes this as a JSON float).
+    pub timestamp: f64,
     /// Working directory.
     #[serde(rename = "cwd")]
     pub working_directory: PathBuf,
@@ -65,8 +65,8 @@ pub struct PreToolUseOutput {
 pub struct PreMcpToolCallInput {
     /// The runtime session ID of the session that triggered the hook.
     pub session_id: String,
-    /// Unix timestamp (ms).
-    pub timestamp: i64,
+    /// Unix timestamp in ms (the runtime serializes this as a JSON float).
+    pub timestamp: f64,
     /// Working directory.
     #[serde(rename = "cwd")]
     pub working_directory: PathBuf,
@@ -104,8 +104,8 @@ pub struct PreMcpToolCallOutput {
 pub struct PostToolUseInput {
     /// The runtime session ID of the session that triggered the hook.
     pub session_id: String,
-    /// Unix timestamp (ms).
-    pub timestamp: i64,
+    /// Unix timestamp in ms (the runtime serializes this as a JSON float).
+    pub timestamp: f64,
     /// Working directory.
     #[serde(rename = "cwd")]
     pub working_directory: PathBuf,
@@ -144,8 +144,8 @@ pub struct PostToolUseOutput {
 pub struct PostToolUseFailureInput {
     /// The runtime session ID of the session that triggered the hook.
     pub session_id: String,
-    /// Unix timestamp (ms).
-    pub timestamp: i64,
+    /// Unix timestamp in ms (the runtime serializes this as a JSON float).
+    pub timestamp: f64,
     /// Working directory.
     #[serde(rename = "cwd")]
     pub working_directory: PathBuf,
@@ -175,8 +175,8 @@ pub struct PostToolUseFailureOutput {
 pub struct UserPromptSubmittedInput {
     /// The runtime session ID of the session that triggered the hook.
     pub session_id: String,
-    /// Unix timestamp (ms).
-    pub timestamp: i64,
+    /// Unix timestamp in ms (the runtime serializes this as a JSON float).
+    pub timestamp: f64,
     /// Working directory.
     #[serde(rename = "cwd")]
     pub working_directory: PathBuf,
@@ -205,8 +205,8 @@ pub struct UserPromptSubmittedOutput {
 pub struct SessionStartInput {
     /// The runtime session ID of the session that triggered the hook.
     pub session_id: String,
-    /// Unix timestamp (ms).
-    pub timestamp: i64,
+    /// Unix timestamp in ms (the runtime serializes this as a JSON float).
+    pub timestamp: f64,
     /// Working directory.
     #[serde(rename = "cwd")]
     pub working_directory: PathBuf,
@@ -235,8 +235,8 @@ pub struct SessionStartOutput {
 pub struct SessionEndInput {
     /// The runtime session ID of the session that triggered the hook.
     pub session_id: String,
-    /// Unix timestamp (ms).
-    pub timestamp: i64,
+    /// Unix timestamp in ms (the runtime serializes this as a JSON float).
+    pub timestamp: f64,
     /// Working directory.
     #[serde(rename = "cwd")]
     pub working_directory: PathBuf,
@@ -271,8 +271,8 @@ pub struct SessionEndOutput {
 pub struct ErrorOccurredInput {
     /// The runtime session ID of the session that triggered the hook.
     pub session_id: String,
-    /// Unix timestamp (ms).
-    pub timestamp: i64,
+    /// Unix timestamp in ms (the runtime serializes this as a JSON float).
+    pub timestamp: f64,
     /// Working directory.
     #[serde(rename = "cwd")]
     pub working_directory: PathBuf,

rust/tests/e2e/hooks_extended.rs

@@ -36,7 +36,7 @@ async fn should_invoke_onsessionstart_hook_on_new_session() {
                 session.send_and_wait("Say hi").await.expect("send");
                 let input = recv_with_timeout(&mut rx, "sessionStart hook").await;
                 assert_eq!(input.source, "new");
-                assert!(input.timestamp > 0);
+                assert!(input.timestamp > 0.0);
                 assert!(!input.working_directory.as_os_str().is_empty());
 
                 session.disconnect().await.expect("disconnect session");
@@ -68,7 +68,7 @@ async fn should_invoke_onuserpromptsubmitted_hook_when_sending_a_message() {
                 session.send_and_wait("Say hello").await.expect("send");
                 let input = recv_with_timeout(&mut rx, "userPromptSubmitted hook").await;
                 assert!(input.prompt.contains("Say hello"));
-                assert!(input.timestamp > 0);
+                assert!(input.timestamp > 0.0);
                 assert!(!input.working_directory.as_os_str().is_empty());
 
                 session.disconnect().await.expect("disconnect session");
@@ -100,7 +100,7 @@ async fn should_invoke_onsessionend_hook_when_session_is_disconnected() {
                 session.send_and_wait("Say hi").await.expect("send");
                 session.disconnect().await.expect("disconnect session");
                 let input = recv_with_timeout(&mut rx, "sessionEnd hook").await;
-                assert!(input.timestamp > 0);
+                assert!(input.timestamp > 0.0);
                 assert!(!input.working_directory.as_os_str().is_empty());
 
                 client.stop().await.expect("stop client");
@@ -237,7 +237,7 @@ async fn should_invoke_sessionend_hook() {
             session.send_and_wait("Say bye").await.expect("send");
             session.disconnect().await.expect("disconnect session");
             let input = recv_with_timeout(&mut rx, "sessionEnd hook").await;
-            assert!(input.timestamp > 0);
+            assert!(input.timestamp > 0.0);
 
             client.stop().await.expect("stop client");
         })
@@ -412,7 +412,7 @@ async fn should_invoke_posttoolusefailure_hook_for_failed_tool_result() {
                         .as_str()
                         .is_some_and(|path| path.contains("missing.txt"))
                 );
-                assert!(input.timestamp > 0);
+                assert!(input.timestamp > 0.0);
                 assert!(!input.working_directory.as_os_str().is_empty());
                 assert!(
                     assistant_message_content(&answer).contains("HOOK_FAILURE_GUIDANCE_APPLIED")

rust/tests/e2e/pre_mcp_tool_call_hook.rs

@@ -126,7 +126,7 @@ async fn should_set_meta_via_premcptoolcall_hook() {
                 assert_eq!(input.server_name, "meta-echo");
                 assert_eq!(input.tool_name, "echo_meta");
                 assert!(!input.working_directory.as_os_str().is_empty());
-                assert!(input.timestamp > 0);
+                assert!(input.timestamp > 0.0);
 
                 session.disconnect().await.expect("disconnect session");
                 client.stop().await.expect("stop client");