fix: restore Workbench session titles from Kafka replay

web/hwlab-cloud-web/src/stores/workbench-live-kafka-event.test.ts

@@ -2,8 +2,9 @@ import assert from "node:assert/strict";
 import { test } from "bun:test";
 
 import type { ChatMessage, TraceEvent } from "../types";
-import { projectWorkbenchLiveKafkaMessage, projectWorkbenchLiveKafkaUserMessage, workbenchAgentMessageIdForTrace, workbenchLiveKafkaEnvelope, workbenchLiveKafkaEventIsUserMessage, workbenchLiveKafkaProjectionTarget, workbenchUserMessageIdForTrace } from "./workbench-live-kafka-event";
+import { projectWorkbenchLiveKafkaMessage, projectWorkbenchLiveKafkaUserMessage, projectWorkbenchLiveKafkaUserSession, workbenchAgentMessageIdForTrace, workbenchLiveKafkaEnvelope, workbenchLiveKafkaEventIsUserMessage, workbenchLiveKafkaProjectionTarget, workbenchUserMessageIdForTrace } from "./workbench-live-kafka-event";
 import { createWorkbenchServerState, reduceWorkbenchServerState, selectActiveMessages, type WorkbenchServerState } from "./workbench-server-state";
+import { sessionToSessionTab } from "./workbench-session";
 
 test("only canonical HWLAB Kafka envelopes bypass terminal priority", () => {
   assert.equal(workbenchLiveKafkaEnvelope("hwlab.event.v1"), true);
@@ -41,6 +42,54 @@ test("live Kafka user event restores and idempotently updates the user bubble",
   assert.equal(second?.updatedAt, event.createdAt);
 });
 
+test("Kafka user replay rebuilds the session rail title without optimistic state", () => {
+  const sessionId = "ses_live_user_title";
+  const traceId = "trc_live_user_title";
+  const firstEvent = traceEvent(1, "user", {
+    userMessageId: "msg_live_user_title_user",
+    messageId: "msg_live_user_title_user",
+    text: "persisted session title",
+    createdAt: "2026-07-10T10:00:00.000Z"
+  });
+  const firstMessage = projectWorkbenchLiveKafkaUserMessage({
+    previous: null,
+    traceId,
+    sessionId,
+    event: firstEvent,
+    receivedAt: "2026-07-10T10:01:00.000Z"
+  });
+  assert.ok(firstMessage);
+  const replayedSession = projectWorkbenchLiveKafkaUserSession({ previous: null, message: firstMessage, sessionId });
+  assert.ok(replayedSession);
+  assert.equal(replayedSession.firstUserMessagePreview, "persisted session title");
+  assert.equal(replayedSession.updatedAt, firstEvent.createdAt);
+  assert.equal(sessionToSessionTab(replayedSession, sessionId).label, "persisted session title");
+
+  const repeatedSession = projectWorkbenchLiveKafkaUserSession({ previous: replayedSession, message: firstMessage, sessionId });
+  assert.deepEqual(repeatedSession, replayedSession);
+
+  const secondEvent = traceEvent(2, "user", {
+    traceId: "trc_live_user_title_second",
+    userMessageId: "msg_live_user_title_second_user",
+    messageId: "msg_live_user_title_second_user",
+    text: "later user input",
+    createdAt: "2026-07-10T10:02:00.000Z"
+  });
+  const secondMessage = projectWorkbenchLiveKafkaUserMessage({
+    previous: null,
+    traceId: "trc_live_user_title_second",
+    sessionId,
+    event: secondEvent,
+    receivedAt: "2026-07-10T10:03:00.000Z"
+  });
+  assert.ok(secondMessage);
+  const updatedSession = projectWorkbenchLiveKafkaUserSession({ previous: replayedSession, message: secondMessage, sessionId });
+  assert.ok(updatedSession);
+  assert.equal(updatedSession.firstUserMessagePreview, "persisted session title");
+  assert.equal(updatedSession.updatedAt, secondEvent.createdAt);
+  assert.equal(sessionToSessionTab(updatedSession, sessionId).label, "persisted session title");
+});
+
 test("HTTP-first and Kafka-first admission converge on one stable optimistic user bubble", () => {
   const sessionId = "ses_live_user_race";
   const traceId = "trc_live_user_race";

web/hwlab-cloud-web/src/stores/workbench-live-kafka-event.ts

@@ -2,7 +2,7 @@
 // Responsibility: project one transparent hwlab.event.v1 business event into visible turn state without replay/finalizer/polling.
 
 import { mergeRunnerTrace } from "../composables/workbench-trace-snapshot";
-import type { ChatMessage, TraceEvent, WorkbenchTurnTimingProjection } from "../types";
+import type { ChatMessage, TraceEvent, WorkbenchSessionRecord, WorkbenchTurnTimingProjection } from "../types";
 import { firstNonEmptyString } from "../utils";
 import { traceAssistantLifecycleEventIsSuperseded } from "../../../../tools/src/hwlab-cli/trace-renderer.ts";
 
@@ -32,6 +32,13 @@ export interface WorkbenchLiveKafkaUserProjectionInput {
   threadId?: string | null;
 }
 
+export interface WorkbenchLiveKafkaUserSessionProjectionInput {
+  previous: WorkbenchSessionRecord | null;
+  message: ChatMessage;
+  sessionId: string;
+  threadId?: string | null;
+}
+
 export function reduceWorkbenchLiveKafkaMessageState(previous: WorkbenchLiveMessageState, event: TraceEvent, previousEvents: TraceEvent[] = []): WorkbenchLiveMessageState {
   if (previous.terminal) return previous;
   const terminal = workbenchLiveKafkaEventIsTerminal(event);
@@ -101,6 +108,20 @@ export function projectWorkbenchLiveKafkaUserMessage(input: WorkbenchLiveKafkaUs
   } as ChatMessage;
 }
 
+export function projectWorkbenchLiveKafkaUserSession(input: WorkbenchLiveKafkaUserSessionProjectionInput): WorkbenchSessionRecord | null {
+  const text = input.message.role === "user" ? firstNonEmptyString(input.message.text, input.message.content) : null;
+  const lastUserMessageAt = timestamp(input.message.createdAt) ?? timestamp(input.message.updatedAt);
+  if (!text || !lastUserMessageAt) return null;
+  return {
+    ...(input.previous ?? {}),
+    sessionId: input.sessionId,
+    threadId: firstNonEmptyString(input.threadId, input.message.threadId, input.previous?.threadId),
+    firstUserMessagePreview: firstNonEmptyString(input.previous?.firstUserMessagePreview, text),
+    lastUserMessageAt,
+    updatedAt: lastUserMessageAt
+  };
+}
+
 export function workbenchLiveKafkaEventIsTerminal(event: TraceEvent | null | undefined): boolean {
   return Boolean(event?.terminal === true || firstNonEmptyString(event?.eventType) === "terminal" || firstNonEmptyString(event?.type) === "result");
 }

web/hwlab-cloud-web/src/stores/workbench.ts

@@ -21,7 +21,7 @@ import { initialWorkbenchSessionIdFromLocation } from "./workbench-projection";
 import { cleanupWorkbenchServerStateSessions, selectActiveMessages, selectActiveSession, selectSessionList, selectSessionStatusAuthority, selectTraceAuthorityById, selectTurnStatusAuthority, type WorkbenchServerAction } from "./workbench-server-state";
 import { cleanupDroppedWorkbenchSessionCaches, trimWorkbenchSessionCache } from "./workbench-session-cache";
 import { reduceWorkbenchRealtimeEvent, workbenchRealtimeEventIsBusinessActivity, type WorkbenchRealtimeAction } from "./workbench-event-reducer";
-import { projectWorkbenchLiveKafkaMessage, projectWorkbenchLiveKafkaUserMessage, workbenchLiveKafkaEnvelope, workbenchLiveKafkaProjectionTarget } from "./workbench-live-kafka-event";
+import { projectWorkbenchLiveKafkaMessage, projectWorkbenchLiveKafkaUserMessage, projectWorkbenchLiveKafkaUserSession, workbenchLiveKafkaEnvelope, workbenchLiveKafkaProjectionTarget } from "./workbench-live-kafka-event";
 import { projectRejectedWorkbenchAdmission } from "./workbench-admission-failure";
 import { messageHasSealedTerminalResult, messageIsSealedTerminal, traceAuthorityIsSealed } from "./workbench-terminal-authority";
 import {
@@ -1075,14 +1075,8 @@ export const useWorkbenchStore = defineStore("workbench", () => {
       if (userMessage) {
         reduceServerState({ type: "message.upsert", sessionId: ownerSessionId, message: userMessage });
         const existing = sessions.value.find((session) => session.sessionId === ownerSessionId) ?? null;
-        if (existing) {
-          const lastUserMessageAt = firstNonEmptyString(userMessage.createdAt, userMessage.updatedAt);
-          rememberSessionList(mergeSessionIntoList(sessions.value, {
-            ...existing,
-            lastUserMessageAt,
-            updatedAt: lastUserMessageAt ?? existing.updatedAt
-          }));
-        }
+        const session = projectWorkbenchLiveKafkaUserSession({ previous: existing, message: userMessage, sessionId: ownerSessionId, threadId });
+        if (session) rememberSessionList(mergeSessionIntoList(sessions.value, session));
       }
       else error.value = "workbench_live_user_message_invalid";
       return;