Fix Assistant profile heartbeat timestamp precision

backend/src/modules/assistant-workspace/profiles.ts

@@ -69,16 +69,18 @@ export async function readAssistantProfiles(
       work_start: string | null;
       work_end: string | null;
       timezone: string | null;
-      observed_at: Date;
+      observed_at: string;
     }>(
-      `SELECT a.night_shift,p.work_start::text,p.work_end::text,p.timezone,current_timestamp AS observed_at
+      `SELECT a.night_shift,p.work_start::text,p.work_end::text,p.timezone,current_timestamp::text AS observed_at
     FROM users u LEFT JOIN agent_settings a ON a.user_id=u.id LEFT JOIN planner_prefs p ON p.user_id=u.id
     WHERE u.id=$1 AND NOT u.disabled`,
       [owner],
     )
   ).rows[0];
   if (!row) fail(404, "That assistant profile is not here.");
-  const observed = now ?? row.observed_at;
+  // Preserve database microseconds for SQL comparisons; Date is only for UI/calendar work.
+  const observedAt = now?.toISOString() ?? row.observed_at;
+  const observed = now ?? new Date(row.observed_at);
   const parsed = nightShiftInput.safeParse(row.night_shift);
   const settings = parsed.success
     ? parsed.data
@@ -109,7 +111,7 @@ export async function readAssistantProfiles(
       await db.query<{ last_seen_at: Date | null; reporting: boolean }>(
         `SELECT last_seen_at,last_seen_at BETWEEN $2::timestamptz - interval '30 seconds' AND $2::timestamptz AS reporting
          FROM service_heartbeats WHERE service=$1`,
-        [`assistant-${lane}`, observed],
+        [`assistant-${lane}`, observedAt],
       )
     ).rows[0];
     const counts = (
@@ -120,7 +122,7 @@ export async function readAssistantProfiles(
        FROM ai_jobs j LEFT JOIN ai_chats c ON c.id=j.chat_id
        WHERE j.user_id=$1 AND j.runtime_lane=$3 AND j.state IN ('queued','running','waiting')
        AND ${assistantChatVisible("c", "$1")} AND ${assistantJobSourcesVisible("j", "$1", false)}`,
-        [owner, observed, lane],
+        [owner, observedAt, lane],
       )
     ).rows[0];
     const lastActivity = await assistantLastActivity(db, owner, lane);

backend/tests/assistant-profiles.test.ts

@@ -82,6 +82,47 @@ test("profile runtime availability follows worker heartbeats without inventing a
     "DELETE FROM service_heartbeats WHERE service IN ('assistant-background','assistant-overnight')",
   );
 });
+test("heartbeat comparisons retain PostgreSQL precision at the observation instant", async () => {
+  const user = await person();
+  const db = await pool.connect();
+  try {
+    // Pin the observation and heartbeat to one transaction instant. Ensure its
+    // sub-millisecond part is nonzero so a Date round-trip cannot hide the bug.
+    let precise = false;
+    for (let attempt = 0; attempt < 10; attempt++) {
+      await db.query("BEGIN");
+      precise = (
+        await db.query<{ precise: boolean }>(
+          "SELECT current_timestamp > date_trunc('milliseconds',current_timestamp) AS precise",
+        )
+      ).rows[0].precise;
+      if (precise) break;
+      await db.query("ROLLBACK");
+    }
+    assert.ok(
+      precise,
+      "fixture must exercise a sub-millisecond database instant",
+    );
+    await db.query(
+      "DELETE FROM service_heartbeats WHERE service IN ('assistant-background','assistant-overnight')",
+    );
+    await db.query(
+      "INSERT INTO service_heartbeats(service,last_seen_at) VALUES('assistant-background',current_timestamp),('assistant-overnight',current_timestamp + interval '1 second')",
+    );
+    const page = await readAssistantProfiles(db, user.id);
+    assert.deepEqual(
+      page.profiles.map((profile) => profile.runtime.reporting),
+      [true, false],
+      "a heartbeat at the observation instant is fresh; a future heartbeat is not",
+    );
+    assert.ok(
+      page.profiles.every((profile) => profile.last_activity_at === null),
+    );
+  } finally {
+    await db.query("ROLLBACK");
+    db.release();
+  }
+});
 test("working requires an unexpired lease; recovery is queued and lanes stay separate", async () => {
   const user = await person();
   const background = await job(user.id, "background");