fix(chat): delete trailing messages before regenerate using transportChatId

[pradipthaadhi]

Summary by CodeRabbit

• Refactor
  • Internal improvements to chat message handling and API communication to ensure proper chat identification across message editor and chat context operations.

[vercel]

The latest updates on your projects. Learn more about Vercel for GitHub.

Project	Deployment	Actions	Updated (UTC)
chat	Ready	Preview	Jun 8, 2026 7:21pm

[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Avoid deleting again after edited-user retries

When a user edits an earlier message, MessageEditor has already called deleteTrailingMessages from that user message before invoking reload() in the same onSuccess callback. Because this hook's messages value is still from the pre-edit render at that point, lastMessage can still be the old assistant response, so this added delete attempts to remove a message that was just deleted and returns before regenerate() if the API reports it as missing. This makes edit-and-resubmit fail in the edited-message path rather than regenerating from the updated user message.

Useful? React with 👍 / 👎.

[cubic-dev-ai]

1 issue found across 1 file

Confidence score: 3/5

• There is a concrete regression risk in hooks/useVercelChat.ts: if the delete API call fails, the catch returns early and regenerate() does not run, which can break the edit-and-resubmit flow.
• Given the medium severity (6/10) and solid confidence (7/10), this is more than a cosmetic issue and can affect user-visible behavior, so the merge risk is moderate.
• Pay close attention to hooks/useVercelChat.ts - ensure delete failures do not block regenerate() in the reload/resubmit path.

<sub>Reply with feedback, questions, or to request a fix.

Re-trigger cubic</sub>

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ℹ️ Review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Pro

Run ID: 4800ba28-702a-4923-8e7d-2556919796d4

📥 Commits

Reviewing files that changed from the base of the PR and between 057674d and a87a0aa.

📒 Files selected for processing (5)

• components/VercelChat/message-editor.tsx
• hooks/reloadOptions.ts
• hooks/useVercelChat.ts
• lib/messages/deleteTrailingMessages.ts
• providers/VercelChatProvider.tsx

📝 Walkthrough

Walkthrough

The PR threads transportChatId through the Vercel Chat context and hook system to replace raw id values in API calls. VercelChatProvider adds the identifier to the context type and passes it through; the hook now exposes it and uses it in deleteTrailingMessages calls. handleReload gains direct API invocation with auth validation, and MessageEditor and handleSendMessage migrate to the correct identifier.

Changes

Transport Chat ID Integration

Layer / File(s)	Summary
Context interface and provider wiring providers/VercelChatProvider.tsx, hooks/useVercelChat.ts	VercelChatContextType adds transportChatId field; VercelChatProvider destructures it from the hook and includes it in context value; useVercelChat returns it in the hook's output shape.
Hook API integration and reload refactor hooks/useVercelChat.ts	Import is aliased to deleteTrailingMessagesApi; handleReload checks last message role, acquires access token, and calls the delete API directly with transportChatId and lastMessage.id before regenerating; handleSendMessage updates trailing-message deletion to use transportChatId.
Message editor and send handler updates components/VercelChat/message-editor.tsx, hooks/useVercelChat.ts	MessageEditor reads transportChatId from context and guards on it; both MessageEditor and handleSendMessage pass transportChatId to deleteTrailingMessages calls instead of raw id.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~12 minutes

Possibly related PRs

• recoupable/chat#1776: Both PRs update MessageEditor, useVercelChat, and VercelChatProvider to use transportChatId (instead of the route id) for deleteTrailingMessages, including the hook/provider plumbing.
• recoupable/chat#1774: Both PRs update the chat transport plumbing to use transportChatId (threaded via useVercelChat/context) instead of the raw id, including changes in useVercelChat.ts to drive transport calls with the new identifier.
• recoupable/chat#1775: Both PRs thread a derived transportChatId through useVercelChat/VercelChatProvider into chat components—this PR then updates MessageEditor and trailing-message deletion to use that transportChatId for API calls.

Suggested reviewers

• sweetmantech

Poem

🚀 Chat IDs flow through context clear,
Transport paths now have no fear,
Messages delete with auth in hand,
The hook and editor work as planned!
Clean plumbing makes the system grand. ✨

🚥 Pre-merge checks | ✅ 2 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Solid & Clean Code	⚠️ Warning	Code violates SOLID & Clean Code: DRY (3 inconsistent deleteTrailingMessages patterns), SRP (useVercelChat: 403 lines, 7 concerns), God Object (context: 38 items), inconsistent error handling.	Unify deleteTrailingMessages patterns, decompose useVercelChat into focused hooks, split context into multiple smaller contexts, standardize error handling.

✅ Passed checks (2 passed)

Check name	Status	Explanation
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

_{✏️ Tip: You can configure your own custom pre-merge checks in the settings.}

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch fix/chat-trailing-delete-transport-chat-id

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[coderabbitai]

Caution

Some comments are outside the diff and can’t be posted inline due to platform limitations.

⚠️ Outside diff range comments (1)

hooks/useVercelChat.ts (1)

305-342: 🛠️ Refactor suggestion | 🟠 Major | 🏗️ Heavy lift

Refactor to use existing useDeleteTrailingMessages hook instead of direct API call.

This implementation duplicates the logic from useDeleteTrailingMessages (lines 230-243), violating the DRY principle. The hook already handles access token retrieval, API invocation, and crucially, local state updates via onSuccess callback.

Current issues:

1. Code duplication - Access token logic and API call pattern are reimplemented
2. State management gap - After the delete API succeeds (line 321), the local messages array still contains the deleted assistant message until regenerate() completes. The hook's onSuccess properly cleans state first.
3. Inconsistent pattern - handleSendMessage (line 377) uses the hook, but handleReload bypasses it
4. Performance concern - Including messages in the dependency array (line 340) recreates this callback on every message change

♻️ Proposed refactor using the existing hook

  const handleReload = useCallback(async () => {
    const headers = await getHeaders();
    await persistSelectedModel();
-
-    const lastMessage = messages.at(-1);
-    if (lastMessage?.role === "assistant") {
-      const accessToken = await getAccessToken();
-      if (!accessToken) {
-        toast.error("Please sign in to regenerate.");
-        return;
-      }
-
-      try {
-        await deleteTrailingMessagesApi({
-          chatId: transportChatId,
-          fromMessageId: lastMessage.id,
-          accessToken,
-        });
-      } catch (error) {
-        console.error("Failed to delete trailing messages before regenerate:", error);
-        toast.error("Failed to regenerate. Please try again.");
-        return;
-      }
-    }
-
+    
+    const lastMessage = messages.at(-1);
+    if (lastMessage?.role === "assistant") {
+      try {
+        await deleteTrailingMessages({
+          chatId: transportChatId,
+          fromMessageId: lastMessage.id,
+        });
+      } catch (error) {
+        console.error("Failed to delete trailing messages before regenerate:", error);
+        toast.error("Failed to regenerate. Please try again.");
+        return;
+      }
+    }
+    
    await regenerate({ body: chatRequestBody, headers });
  }, [
    getHeaders,
-    getAccessToken,
+    deleteTrailingMessages,
    regenerate,
    chatRequestBody,
    persistSelectedModel,
-    messages,
    transportChatId,
  ]);

Note: Removed messages from dependency array since it would cause unnecessary callback recreation. The latest messages will be captured at call time.

As per coding guidelines, write minimal code and avoid unnecessary abstractions during implementation; the existing hook should be leveraged instead of duplicating its logic.

🤖 Prompt for AI Agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

In `@hooks/useVercelChat.ts` around lines 305 - 342, Refactor handleReload to call
the existing useDeleteTrailingMessages hook instead of calling
deleteTrailingMessagesApi directly: keep the persistSelectedModel and headers
logic (getHeaders, persistSelectedModel, regenerate) but replace the
accessToken/API call block with the hook's mutate function (from
useDeleteTrailingMessages) so the hook can obtain the token, call the API, and
run its onSuccess to update local messages before calling regenerate; remove
messages from the handleReload dependency array and ensure you pass
transportChatId and lastMessage.id (or fromMessageId) to the hook's mutate call
so state is cleaned first and the regenerate({ body: chatRequestBody, headers })
call happens after the hook signals success.

Source: Coding guidelines

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Outside diff comments:
In `@hooks/useVercelChat.ts`:
- Around line 305-342: Refactor handleReload to call the existing
useDeleteTrailingMessages hook instead of calling deleteTrailingMessagesApi
directly: keep the persistSelectedModel and headers logic (getHeaders,
persistSelectedModel, regenerate) but replace the accessToken/API call block
with the hook's mutate function (from useDeleteTrailingMessages) so the hook can
obtain the token, call the API, and run its onSuccess to update local messages
before calling regenerate; remove messages from the handleReload dependency
array and ensure you pass transportChatId and lastMessage.id (or fromMessageId)
to the hook's mutate call so state is cleaned first and the regenerate({ body:
chatRequestBody, headers }) call happens after the hook signals success.

---

ℹ️ Review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Pro

Run ID: 332d97fb-87f1-4735-828c-9a8dfaa541ad

📥 Commits

Reviewing files that changed from the base of the PR and between 6e55275 and 057674d.

📒 Files selected for processing (3)

• components/VercelChat/message-editor.tsx
• hooks/useVercelChat.ts
• providers/VercelChatProvider.tsx

[cubic-dev-ai]

0 issues found across 5 files (changes from recent commits).

<sub>Requires human review: This change modifies the core chat regeneration logic by adding conditional server-side trailing message deletion and introducing a new API error class, which carries significant risk of message loss or unexpected behavior and requires careful human review.

Re-trigger cubic</sub>