fix(chat): ensure agent persists correctly after page refresh

[juliennonin]

Description

Fixes #8087.

Fixes a race condition where the agent selection was initialized in useState before availableAgents loaded, causing the wrong agent to be selected after page refresh.

How Has This Been Tested?

Updated live_agent.spec.ts to test after page refresh.

Additional Options

• [Optional] Please cherry-pick this PR to the latest release version.
• [Optional] Override Linear Check

---

Summary by cubic

Fixes a race condition that selected the wrong agent after a page refresh. The chosen agent now persists through reloads and after starting a chat, and stays in sync with the sidebar.

• Bug Fixes
  • Compute the implied agent with useMemo after availableAgents load, using chat persona_id or defaultAgentId when present.
  • Selection order: explicit user choice, then implied agent, then defaults.
  • Expose data-testid="sidebar-section/{title}" and add a sidebar check in e2e to ensure the selected agent stays highlighted after sending a message and after a hard reload.

^{Written for commit 6204e7f. Summary will update on new commits.}

[cubic-dev-ai]

2 issues found across 4 files

Confidence score: 3/5

• There is a concrete regression risk in web/src/hooks/useAgentController.ts: liveAgent can remain memoized without impliedAssistant in its dependency set, so persona/session changes may show a stale assistant state to users.
• web/tests/e2e/utils/chatActions.ts introduces a reliability risk rather than a product bug: the 1s default timeout is likely too short after refresh and can cause intermittent E2E failures.
• Given two medium-severity, high-confidence findings (including one user-facing behavior issue), this carries some merge risk and is better addressed before landing.
• Pay close attention to web/src/hooks/useAgentController.ts and web/tests/e2e/utils/chatActions.ts - stale memoized agent selection and overly aggressive timeout defaults can cause incorrect UI state and flaky tests.

Prompt for AI agents (unresolved issues)

Check if these issues are valid — if so, understand the root cause of each and fix them. If appropriate, use sub-agents to investigate and fix each issue separately.


<file name="web/src/hooks/useAgentController.ts">

<violation number="1" location="web/src/hooks/useAgentController.ts:62">
P2: `liveAgent` now returns `impliedAssistant` but the memo deps don’t include it (or its source IDs). When the session/URL persona changes, `impliedAssistant` updates while `liveAgent` stays memoized, leaving a stale agent selection.</violation>
</file>

<file name="web/tests/e2e/utils/chatActions.ts">

<violation number="1" location="web/tests/e2e/utils/chatActions.ts:21">
P2: New sidebar verification helper uses a 1s default timeout, which is too aggressive for post-refresh UI assertions and can cause flaky E2E failures.</violation>
</file>

_{Reply with feedback, questions, or to request a fix. Tag @cubic-dev-ai to re-run a review.}

[greptile-apps]

Greptile Summary

This PR fixes a race condition in useAgentController where the selected agent was initialised inside useState(…) before availableAgents had loaded from SWR, causing the wrong (usually the default) agent to appear after a hard page reload.

Key changes:

• impliedAssistant is now computed via useMemo (instead of being baked into the useState initial value), so it re-evaluates once availableAgents arrives. The explicit type annotation (MinimalPersonaSnapshot | undefined) follows the repo's type-annotation standards.
• The selection precedence is made explicit in comments: explicit user choice → implied agent (from chat session persona_id or URL param) → unified/pinned/available defaults.
• SidebarSection gains a data-testid={sidebar-section/${title}} attribute so e2e tests can reliably target a specific sidebar section.
• The e2e test live_agent.spec.ts is extended to send a message (persisting the session with a persona_id), hard-reload the page, and assert the correct agent is still highlighted in the sidebar.
• A new verifyAgentIsChosenInSidebar helper is added in chatActions.ts with a default 5 000 ms timeout — consistent with the existing verifyAgentIsChosen.

The fix is minimal and well-scoped. The only minor nit is a leftover comment stub in the spec file (no assertion follows it) that may confuse future maintainers.

Confidence Score: 5/5

• Safe to merge — the race-condition fix is correct and the only remaining finding is a minor comment cleanup in a test file.
• All remaining findings are P2 style suggestions; no logic errors or data-integrity issues were identified. The core useMemo refactor correctly handles the async load of availableAgents, and the selection priority ordering is sound.
• No files require special attention.

Important Files Changed

Filename	Overview
web/src/hooks/useAgentController.ts	Core bug fix: moves implied agent computation from useState initialization into a reactive useMemo, correctly handling async availableAgents load on page refresh. Type annotation is explicit. Priority ordering (explicit selection → implied → defaults) is sound.
web/src/sections/sidebar/SidebarSection.tsx	Minimal, clean addition of data-testid derived from the title prop to enable sidebar section targeting in e2e tests.
web/tests/e2e/chat/live_agent.spec.ts	Adds page-reload persistence test for the selected agent; contains a dangling comment stub with no assertion body that could confuse future maintainers.
web/tests/e2e/utils/chatActions.ts	New verifyAgentIsChosenInSidebar helper targets the sidebar section via data-testid and checks the selected state; default timeout is consistent with existing helpers (5000 ms).

Sequence Diagram

sequenceDiagram
    participant Browser
    participant React
    participant SWR
    participant useAgentController

    Browser->>React: Hard page reload
    React->>useAgentController: mount (availableAgents = [])
    Note over useAgentController: selectedAgent = undefined (useState)<br/>impliedAssistant = undefined (availableAgents empty)<br/>liveAgent → unified/default fallback

    React->>SWR: fetch /api/persona & /api/chat-session
    SWR-->>React: availableAgents loaded, chatSession loaded

    React->>useAgentController: re-render (availableAgents populated)
    Note over useAgentController: impliedAssistant = availableAgents.find(chatSession.persona_id)<br/>liveAgent = impliedAssistant ✓ correct agent shown

Loading

Prompt To Fix All With AI

This is a comment left during a code review.
Path: web/tests/e2e/chat/live_agent.spec.ts
Line: 57

Comment:
**Dangling comment with no assertion**

The comment `// Verify the agent is still selected in the sidebar` is left without a corresponding assertion directly below it — the actual `verifyAgentIsChosenInSidebar` call for the pre-reload state was placed above at line 52, and the post-reload check is at line 63. This orphaned comment could mislead future readers into thinking a step was accidentally omitted.

```suggestion
  // Hard refresh the page
```

How can I resolve this? If you propose a fix, please make it concise.

_{Reviews (3): Last reviewed commit: "Merge branch 'main' into fix/agent_selec..." | Re-trigger Greptile}