feat(diagnostics): add configurable stuck-session warning threshold

src/logging/diagnostic.test.ts

@@ -1,5 +1,6 @@
 import fs from "node:fs";
 import { afterEach, beforeEach, describe, expect, it, vi } from "vitest";
+import { onDiagnosticEvent, resetDiagnosticEventsForTest } from "../infra/diagnostic-events.js";
 import {
   diagnosticSessionStates,
   getDiagnosticSessionStateCountForTest,
@@ -7,6 +8,12 @@ import {
   pruneDiagnosticSessionStates,
   resetDiagnosticSessionStateForTest,
 } from "./diagnostic-session-state.js";
+import {
+  logSessionStateChange,
+  resetDiagnosticStateForTest,
+  resolveStuckSessionWarnMs,
+  startDiagnosticHeartbeat,
+} from "./diagnostic.js";
 
 describe("diagnostic session state pruning", () => {
   beforeEach(() => {
@@ -74,3 +81,60 @@ describe("logger import side effects", () => {
     expect(mkdirSpy).not.toHaveBeenCalled();
   });
 });
+
+describe("stuck session diagnostics threshold", () => {
+  beforeEach(() => {
+    vi.useFakeTimers();
+    resetDiagnosticStateForTest();
+    resetDiagnosticEventsForTest();
+  });
+
+  afterEach(() => {
+    resetDiagnosticEventsForTest();
+    resetDiagnosticStateForTest();
+    vi.useRealTimers();
+  });
+
+  it("uses the configured diagnostics.stuckSessionWarnMs threshold", () => {
+    const events: Array<{ type: string }> = [];
+    const unsubscribe = onDiagnosticEvent((event) => {
+      events.push({ type: event.type });
+    });
+    try {
+      startDiagnosticHeartbeat({
+        diagnostics: {
+          enabled: true,
+          stuckSessionWarnMs: 30_000,
+        },
+      });
+      logSessionStateChange({ sessionId: "s1", sessionKey: "main", state: "processing" });
+      vi.advanceTimersByTime(61_000);
+    } finally {
+      unsubscribe();
+    }
+
+    expect(events.filter((event) => event.type === "session.stuck")).toHaveLength(1);
+  });
+
+  it("falls back to default threshold when config is absent", () => {
+    const events: Array<{ type: string }> = [];
+    const unsubscribe = onDiagnosticEvent((event) => {
+      events.push({ type: event.type });
+    });
+    try {
+      startDiagnosticHeartbeat();
+      logSessionStateChange({ sessionId: "s2", sessionKey: "main", state: "processing" });
+      vi.advanceTimersByTime(31_000);
+    } finally {
+      unsubscribe();
+    }
+
+    expect(events.filter((event) => event.type === "session.stuck")).toHaveLength(0);
+  });
+
+  it("uses default threshold for invalid values", () => {
+    expect(resolveStuckSessionWarnMs({ diagnostics: { stuckSessionWarnMs: -1 } })).toBe(120_000);
+    expect(resolveStuckSessionWarnMs({ diagnostics: { stuckSessionWarnMs: 0 } })).toBe(120_000);
+    expect(resolveStuckSessionWarnMs()).toBe(120_000);
+  });
+});