fix: handle 404 errors for deleted assistant conversations

[nioasoft]

Summary

• Fix endless 404 errors when stored conversation ID no longer exists
• Stop retrying on 404 errors (conversation doesn't exist)
• Automatically clear invalid conversation ID from localStorage

Test plan

• Delete assistant.db or reset database while having active conversation
• Refresh browser - should see warning in console and no repeated 404 errors
• Assistant should work normally with new conversation

🤖 Generated with Claude Code

Summary by CodeRabbit

• Bug Fixes
  • Improved handling when a conversation is no longer available to avoid stale state and errors.
  • Added automatic retry for transient conversation-loading failures to improve reliability (fewer interruptions).

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[coderabbitai]

📝 Walkthrough

Walkthrough

Added retry policy to conversation fetching (skip retries for 404/not-found); AssistantPanel now reads conversationError and clears stored conversationId when a 404-like error is observed.

Changes

Cohort / File(s)	Summary
Conversation hook ui/src/hooks/useConversations.ts	Added retry policy: do not retry when error message contains "not found" (case-insensitive) or equals "HTTP 404"; otherwise retry up to 3 times.
UI error handling ui/src/components/AssistantPanel.tsx	Expanded hook destructure to include conversationError; added effect to clear local conversationId when a 404/not-found error is returned.

Sequence Diagram(s)

sequenceDiagram
    participant UI as AssistantPanel
    participant Hook as useConversation
    participant API as Conversation API

    UI->>Hook: call useConversation(conversationId)
    Hook->>API: fetch /conversations/:id
    alt response 200
        API-->>Hook: conversation data
        Hook-->>UI: data, isLoading=false, conversationError=null
    else response error
        API-->>Hook: error (message)
        Hook-->>Hook: retry decision (if message contains "not found" or "HTTP 404" -> no retry; else retry up to 3)
        Hook-->>UI: data=null, isLoading=false, conversationError=error
        alt error indicates 404/not-found
            UI->>UI: clear stored conversationId (set to null)
        end
    end

Loading

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~8 minutes

Possibly related PRs

• feature: add conversation history feature to AI assistant #74: Changes to AssistantPanel and useConversations touching conversation-state and error handling flow that this PR modifies.

Poem

🐰
A missing chat, a tiny fright,
I sniff the trails and make it right.
If 404s block the way we roam,
I'll clear the path and lead us home.
Hop on — fresh convo, fresh foam!

🚥 Pre-merge checks | ✅ 2 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 50.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (2 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The PR title 'fix: handle 404 errors for deleted assistant conversations' directly and accurately summarizes the main change: adding error handling for 404 errors when conversation IDs no longer exist, which is the core purpose across both modified files.

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✨ Finishing touches

• 📝 Generate docstrings

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[coderabbitai]

Actionable comments posted: 1

🤖 Fix all issues with AI agents

In `@ui/src/components/AssistantPanel.tsx`:
- Around line 57-63: The effect currently clears conversationId for any
conversationError; change it so it only clears when the error represents a 404.
In the useEffect that watches conversationError, conversationId and calls
setConversationId(null), check the error's HTTP status (e.g.,
conversationError.status or conversationError.response?.status) and only call
setConversationId(null) when that status === 404; otherwise leave the stored ID
intact and do not clear it. Ensure the conditional still guards on
conversationError and conversationId before checking the status.

[leonvanzyl]

Code Review: Request Changes

Thanks for addressing this issue! The PR tackles a real problem, but I found a bug that will prevent the retry logic from working as intended.

Critical Issue: 404 Detection Won't Work

The retry function checks:

if (error instanceof Error && error.message.includes('404')) {
  return false
}

However, the server returns {"detail": "Conversation not found"} for 404 errors. The fetchJSON function in api.ts throws:

throw new Error(error.detail || `HTTP ${response.status}`)

So the error message becomes "Conversation not found" — which does not contain the string "404". The retry logic will still retry 3 times before failing.

Suggested fix for useConversations.ts:

retry: (failureCount, error) => {
  // Don't retry on "not found" errors (404)
  if (error instanceof Error && (
    error.message.toLowerCase().includes('not found') ||
    error.message === 'HTTP 404'
  )) {
    return false
  }
  return failureCount < 3
}

Secondary Issue: Overly Broad Error Clearing

The useEffect in AssistantPanel.tsx clears the conversation ID on any error:

if (conversationError && conversationId) {
  setConversationId(null)  // Clears for ALL errors
}

This means network errors, 500 errors, or timeouts will also clear the stored conversation ID, potentially losing valid conversation references during temporary outages.

Suggested fix for AssistantPanel.tsx:

useEffect(() => {
  if (conversationError && conversationId) {
    const message = conversationError.message.toLowerCase()
    // Only clear for 404 errors, not transient network issues
    if (message.includes('not found') || message.includes('404')) {
      console.warn(`Conversation ${conversationId} not found, clearing stored ID`)
      setConversationId(null)
    }
  }
}, [conversationError, conversationId])

Summary

Issue	Severity	Action
404 detection uses wrong string	High	Must fix
Error clearing too broad	Medium	Should fix

The approach is sound — just needs these adjustments to work correctly. Let me know if you have questions!

[leonvanzyl]

Thank you!