diff --git a/src/lib/__tests__/claude-cli-transport.test.ts b/src/lib/__tests__/claude-cli-transport.test.ts
index 15cac9140..e1b38f3df 100644
--- a/src/lib/__tests__/claude-cli-transport.test.ts
+++ b/src/lib/__tests__/claude-cli-transport.test.ts
@@ -133,6 +133,46 @@ describe("createClaudeCodeStreamParser", () => {
     expect(parse(JSON.stringify({ type: "future_type_we_dont_know" }))).toBeNull()
   })
 
+  it("signals a fatal error via onFatalError when a result event has is_error: true", () => {
+    // Real-user scenario (#708): an expired OAuth session makes claude
+    // report the fatal error inside a `result` event on stdout — not on
+    // stderr and not as a separate `error` event. The parser must hand
+    // the `result` text to onFatalError instead of discarding the line.
+    const parse = createClaudeCodeStreamParser()
+    const onFatalError = vi.fn()
+    parse.onFatalError = onFatalError
+    const line = JSON.stringify({
+      type: "result",
+      subtype: "success",
+      is_error: true,
+      result: "Failed to authenticate: OAuth session expired and could not be refreshed",
+    })
+    expect(parse(line)).toBeNull()
+    expect(onFatalError).toHaveBeenCalledTimes(1)
+    expect(onFatalError).toHaveBeenCalledWith(
+      "Failed to authenticate: OAuth session expired and could not be refreshed",
+    )
+  })
+
+  it("does not fire onFatalError for an is_error result without a usable result string", () => {
+    const parse = createClaudeCodeStreamParser()
+    const onFatalError = vi.fn()
+    parse.onFatalError = onFatalError
+    expect(parse(JSON.stringify({ type: "result", is_error: true }))).toBeNull()
+    expect(parse(JSON.stringify({ type: "result", is_error: true, result: 42 }))).toBeNull()
+    expect(parse(JSON.stringify({ type: "result", is_error: true, result: "   " }))).toBeNull()
+    expect(onFatalError).not.toHaveBeenCalled()
+  })
+
+  it("does not fire onFatalError for successful result events", () => {
+    const parse = createClaudeCodeStreamParser()
+    const onFatalError = vi.fn()
+    parse.onFatalError = onFatalError
+    expect(parse(JSON.stringify({ type: "result", subtype: "success", result: "done" }))).toBeNull()
+    expect(parse(JSON.stringify({ type: "result", is_error: false, result: "done" }))).toBeNull()
+    expect(onFatalError).not.toHaveBeenCalled()
+  })
+
   it("returns null for malformed JSON or blank lines", () => {
     const parse = createClaudeCodeStreamParser()
     expect(parse("")).toBeNull()
@@ -386,6 +426,59 @@ describe("streamClaudeCodeCli", () => {
     )
   })
 
+  it("shows the auth hint when an is_error result reports an expired OAuth session", async () => {
+    // #708: claude exits 1 with empty stderr once the local OAuth
+    // session expires; the real error travels in a stream-json `result`
+    // event on stdout. The user must see the login hint, not the raw
+    // JSON blob that line used to be dumped as.
+    const callbacks = {
+      onToken: vi.fn(),
+      onDone: vi.fn(),
+      onError: vi.fn(),
+    }
+
+    const stream = streamClaudeCodeCli(
+      {
+        provider: "claude-code",
+        apiKey: "",
+        model: "claude-sonnet-4-6",
+        ollamaUrl: "",
+        customEndpoint: "",
+        maxContextSize: 200000,
+      },
+      [{ role: "user", content: "ping" }],
+      callbacks,
+    )
+
+    await vi.waitFor(() => {
+      expect(tauriMocks.invoke).toHaveBeenCalledTimes(1)
+    })
+
+    const payload = tauriMocks.invoke.mock.calls[0]?.[1] as { streamId: string }
+    tauriMocks.emit(
+      `claude-cli:${payload.streamId}`,
+      JSON.stringify({
+        type: "result",
+        subtype: "success",
+        is_error: true,
+        result: "Failed to authenticate: OAuth session expired and could not be refreshed",
+      }),
+    )
+    tauriMocks.emit(`claude-cli:${payload.streamId}:done`, { code: 1, stderr: "" })
+
+    await stream
+
+    expect(callbacks.onError).toHaveBeenCalledTimes(1)
+    const message = (callbacks.onError.mock.calls[0]?.[0] as Error).message
+    expect(message).toMatch(/not authenticated/i)
+    expect(message).toContain("`claude`")
+    expect(message).toMatch(/terminal/i)
+    expect(message).not.toContain("is_error")
+    expect(message).not.toMatch(/couldn't parse/)
+    expect(callbacks.onToken).not.toHaveBeenCalled()
+    expect(callbacks.onDone).not.toHaveBeenCalled()
+  })
+
   it("does not spawn when the signal is already aborted", async () => {
     const controller = new AbortController()
     controller.abort()
@@ -448,6 +541,52 @@ describe("buildExitError", () => {
     expect(msg).toMatch(/not authenticated/i)
   })
 
+  it("recognizes an auth failure carried in the result text (the #708 case)", () => {
+    // claude reports an expired OAuth session via a stream-json result
+    // event on stdout, with stderr empty — the message must still land
+    // on the friendly login hint.
+    const msg = buildExitError(
+      1,
+      "",
+      "",
+      "Failed to authenticate: OAuth session expired and could not be refreshed",
+    )
+    expect(msg).toMatch(/not authenticated/i)
+    expect(msg).toMatch(/`claude`/)
+    expect(msg).toMatch(/terminal/i)
+    expect(msg).not.toMatch(/couldn't parse/)
+  })
+
+  it("prefers the auth hint over the raw unparsed stdout dump", () => {
+    // Before #708 the user saw the JSON wall below instead of the
+    // login hint, because the auth check only ever looked at stderr.
+    const dump =
+      '{"type":"system","subtype":"init","session_id":"abc"}\n' +
+      '{"type":"result","is_error":true,"result":"Failed to authenticate: OAuth session expired and could not be refreshed"}'
+    const msg = buildExitError(
+      1,
+      "",
+      dump,
+      "Failed to authenticate: OAuth session expired and could not be refreshed",
+    )
+    expect(msg).toMatch(/not authenticated/i)
+    expect(msg).toContain("`claude`")
+    expect(msg).not.toContain("is_error")
+    expect(msg).not.toMatch(/couldn't parse/)
+  })
+
+  it("surfaces a non-auth result error instead of the JSON dump", () => {
+    const msg = buildExitError(1, "", "", "Invalid API key provided")
+    expect(msg).toContain("Invalid API key provided")
+    expect(msg).toContain("code 1")
+    expect(msg).not.toMatch(/couldn't parse/)
+  })
+
+  it("matches the OAuth-session-expired phrasing without the authenticate prefix", () => {
+    const msg = buildExitError(1, "", "", "OAuth session expired and could not be refreshed")
+    expect(msg).toMatch(/not authenticated/i)
+  })
+
   it("falls back to unparsed stdout when stderr is empty (the real-user case)", () => {
     // Real-user scenario: claude exit 1, stderr empty, but stdout
     // had a structured error event our parser didn't recognize.
diff --git a/src/lib/claude-cli-transport.ts b/src/lib/claude-cli-transport.ts
index a3bdc0772..f5079aad8 100644
--- a/src/lib/claude-cli-transport.ts
+++ b/src/lib/claude-cli-transport.ts
@@ -17,6 +17,17 @@ import { useWikiStore } from "@/stores/wiki-store"
 import type { ChatMessage, RequestOverrides } from "./llm-providers"
 import type { StreamCallbacks } from "./llm-client"
 
+/**
+ * A parser is a callable that maps one stream-json line to the
+ * assistant text it contains. `onFatalError` is an optional side
+ * channel: a `result` event with `is_error: true` carries the CLI's
+ * authoritative failure message (e.g. an expired OAuth session), and
+ * the parser reports it there instead of silently dropping the event.
+ */
+type ClaudeCodeStreamParser = ((rawLine: string) => string | null) & {
+  onFatalError?: (message: string) => void
+}
+
 /**
  * Public parse entry point. Given one stream-json line from claude's
  * stdout, returns any assistant text it contains (or null for events
@@ -28,14 +39,14 @@ import type { StreamCallbacks } from "./llm-client"
  * real token-level deltas. To avoid double-counting, we prefer deltas
  * when they arrive and skip the fat `assistant` events after seeing one.
  */
-export function createClaudeCodeStreamParser() {
+export function createClaudeCodeStreamParser(): ClaudeCodeStreamParser {
   let sawDelta = false
   // Track the running text we have emitted for the current assistant
   // turn via `assistant` events so we can diff new content off the end
   // and only emit what wasn't already streamed.
   let emittedFromAssistant = ""
 
-  return function parseLine(rawLine: string): string | null {
+  const parseLine: ClaudeCodeStreamParser = (rawLine: string): string | null => {
     const line = rawLine.trim()
     if (!line) return null
 
@@ -94,9 +105,25 @@ export function createClaudeCodeStreamParser() {
       return text
     }
 
+    // A `result` event normally carries only the turn summary, but when
+    // `is_error` is set it holds the CLI's authoritative fatal error —
+    // e.g. "Failed to authenticate: OAuth session expired..." (note the
+    // misleading `"subtype":"success"`). claude reports auth failures on
+    // stdout this way — there is no separate `error` event and stderr
+    // stays empty — so surface the `result` text via onFatalError rather
+    // than discarding the event into the unparsed-stdout dump. (#708)
+    if (type === "result" && obj.is_error === true) {
+      if (typeof obj.result === "string" && obj.result.trim()) {
+        parseLine.onFatalError?.(obj.result)
+      }
+      return null
+    }
+
     // Ignore session init, tool_use, result summary, unknown types.
     return null
   }
+
+  return parseLine
 }
 
 // Tauri's `invoke` typing requires the payload object to satisfy
@@ -142,6 +169,13 @@ export async function streamClaudeCodeCli(
 
   const streamId = crypto.randomUUID()
   const parse = createClaudeCodeStreamParser()
+  // Fatal errors reported inside a stream-json `result` event (an
+  // expired OAuth session, for instance) land here instead of being
+  // buried in the unparsed-stdout dump below.
+  let fatalResultError = ""
+  parse.onFatalError = (message) => {
+    fatalResultError = message
+  }
 
   let unlistenData: UnlistenFn | undefined
   let unlistenDone: UnlistenFn | undefined
@@ -238,14 +272,16 @@ export async function streamClaudeCodeCli(
         if (code !== null && code !== undefined && code !== 0) {
           finishWith(() =>
             onError(
-              new Error(buildExitError(code, stderr, unparsedLines.join("\n"))),
+              new Error(
+                buildExitError(code, stderr, unparsedLines.join("\n"), fatalResultError),
+              ),
             ),
           )
         } else if (!emittedToken) {
           // CLI exited successfully but produced no assistant text.
           // Surface this as an explicit error so the ingest pipeline
           // retries rather than silently writing an empty stub page.
-          const details = stderr || unparsedLines.join("\n").trim()
+          const details = fatalResultError || stderr || unparsedLines.join("\n").trim()
           finishWith(() =>
             onError(new Error(
               details
@@ -308,20 +344,26 @@ export async function streamClaudeCodeCli(
  * we used to throw was correct but unactionable — users had to
  * read JSON-shaped stderr text to figure out what to do.
  *
- * Three diagnostic sources, used in priority order:
- *   1. stderr — the canonical place. The most common content is
- *      `Unauthenticated:` from Claude Code itself, meaning the
- *      user's ~/.claude OAuth token expired / was revoked / they
- *      logged out. We surface that case explicitly because users
- *      otherwise mis-diagnose it as an LLM Wiki bug.
- *   2. unparsedStdout — stdout lines the parser didn't recognize
- *      (non-JSON, unknown event types, the stream-json `error`
- *      event shape). Used as a fallback when stderr is empty —
- *      claude sometimes writes its real diagnostic to stdout via
- *      the stream-json channel, and our parser silently drops
- *      anything it doesn't classify, leaving users with no info
- *      at all.
- *   3. Neither — silent exit. We can't help much here other than
+ * Four diagnostic sources, used in priority order:
+ *   1. auth failure — the most common fatal case. Detected by
+ *      pattern-matching stderr AND resultError together, because
+ *      claude reports an expired/revoked OAuth session in different
+ *      places depending on version: `Unauthenticated:` on stderr, or
+ *      a `{"type":"result","is_error":true,"result":"Failed to
+ *      authenticate: ..."}` event on stdout with empty stderr (#708).
+ *      Surfaced explicitly because users otherwise mis-diagnose it
+ *      as an LLM Wiki bug.
+ *   2. resultError — the `result` text extracted from an is_error
+ *      result event. It's the CLI's own one-line failure
+ *      description, so it beats dumping raw stdout JSON at the user.
+ *   3. stderr — other stderr diagnostics.
+ *   4. unparsedStdout — stdout lines the parser didn't recognize
+ *      (non-JSON, unknown event shapes). Used as a fallback when
+ *      stderr is empty — claude sometimes writes its real diagnostic
+ *      to stdout via the stream-json channel, and our parser
+ *      silently drops anything it doesn't classify, leaving users
+ *      with no info at all.
+ *   5. Neither — silent exit. We can't help much here other than
  *      telling the user to reproduce in a terminal where they can
  *      see whatever output the CLI does produce.
  */
@@ -329,16 +371,28 @@ export function buildExitError(
   code: number,
   stderr: string,
   unparsedStdout: string = "",
+  resultError: string = "",
 ): string {
-  if (/unauthenticated|please.*log\s*in|authentication.*failed/i.test(stderr)) {
+  // Match stderr and the extracted result text together: the auth
+  // failure travels on either channel depending on CLI version.
+  const diagnostics = `${stderr}\n${resultError}`
+  if (
+    /unauthenticated|please.*log\s*in|authentication.*failed|failed to authenticate|oauth session expired/i.test(
+      diagnostics,
+    )
+  ) {
     return [
       "Claude Code CLI is not authenticated.",
       "Please open a terminal and run `claude` to complete the OAuth login,",
       "then retry. (LLM Wiki only spawns the binary — it can't run the",
       "login flow on your behalf.)",
       stderr ? `\n\n— stderr —\n${stderr}` : "",
+      resultError ? `\n\n— result —\n${resultError}` : "",
     ].join(" ").trim()
   }
+  if (resultError.trim()) {
+    return `claude CLI exited with code ${code}: ${resultError}`
+  }
   if (stderr) {
     return `claude CLI exited with code ${code}: ${stderr}`
   }