# Top 12 Errors - OpenAI Assistants API

**Last Updated**: 2025-10-25

This document catalogs the most common errors encountered when working with the Assistants API v2 and their solutions.

---

## 1. Thread Already Has Active Run

**Error Message**:
```
Error: 400 Can't add messages to thread_xxx while a run run_xxx is active.
```

**Cause**: Trying to create a new run or add messages while another run is still processing (status: `queued`, `in_progress`, or `cancelling`).

**Solution**:
```typescript
async function ensureNoActiveRun(threadId: string) {
  const runs = await openai.beta.threads.runs.list(threadId, {
    limit: 1,
    order: 'desc',
  });

  const latestRun = runs.data[0];
  if (latestRun && ['queued', 'in_progress', 'cancelling'].includes(latestRun.status)) {
    // Wait for completion or cancel
    await openai.beta.threads.runs.cancel(threadId, latestRun.id);

    // Poll until cancelled
    let run = latestRun;
    while (run.status !== 'cancelled') {
      await new Promise(resolve => setTimeout(resolve, 500));
      run = await openai.beta.threads.runs.retrieve(threadId, run.id);
    }
  }
}
```

**Prevention**: Always check for active runs before creating new ones.

**Source**: [OpenAI Community](https://community.openai.com/t/error-running-thread-already-has-an-active-run/782118)

---

## 2. Run Polling Timeout

**Error**: Run never completes within reasonable polling window (300+ seconds).

**Cause**: Long-running tasks (complex code execution, large file processing) exceed expected completion time.

**Solution**:
```typescript
async function pollWithTimeout(threadId: string, runId: string, maxSeconds = 300) {
  const startTime = Date.now();

  while (true) {
    const run = await openai.beta.threads.runs.retrieve(threadId, runId);

    if (!['queued', 'in_progress'].includes(run.status)) {
      return run;
    }

    const elapsed = (Date.now() - startTime) / 1000;
    if (elapsed > maxSeconds) {
      await openai.beta.threads.runs.cancel(threadId, runId);
      throw new Error(`Run exceeded timeout of ${maxSeconds}s`);
    }

    await new Promise(resolve => setTimeout(resolve, 1000));
  }
}
```

**Prevention**: Set appropriate timeouts and use streaming for better UX.

---

## 3. Vector Store Indexing Delay

**Error**: File search returns no results despite files being uploaded.

**Cause**: Using vector store before indexing completes (async process).

**Solution**:
```typescript
async function waitForVectorStore(vectorStoreId: string) {
  let store = await openai.beta.vectorStores.retrieve(vectorStoreId);

  while (store.status === 'in_progress') {
    await new Promise(resolve => setTimeout(resolve, 2000));
    store = await openai.beta.vectorStores.retrieve(vectorStoreId);
    console.log(`Indexing: ${store.file_counts.completed}/${store.file_counts.total}`);
  }

  if (store.status === 'failed') {
    throw new Error('Vector store indexing failed');
  }

  return store; // status: 'completed'
}
```

**Prevention**: Always wait for `status: "completed"` before using vector store with assistants.

**Source**: [OpenAI Community](https://community.openai.com/t/assistants-api-file-search-and-vector-stores/863944)

---

## 4. File Search Relevance Issues

**Error**: File search returns irrelevant or incomplete results.

**Cause**: Poor document chunking, lack of context, or query optimization needed.

**Solution**:
- **Better instructions**: Guide assistant on how to use file search
- **Structured documents**: Use clear headers, sections, and formatting
- **Metadata**: Add descriptive metadata to files (coming soon)
- **Query refinement**: Encourage users to be specific

```typescript
const assistant = await openai.beta.assistants.create({
  instructions: `You are a support assistant. When answering:
    1. Use file_search to find relevant documentation
    2. Quote specific sections with citations
    3. If information isn't found, say so clearly
    4. Provide context around the answer`,
  tools: [{ type: "file_search" }],
  // ...
});
```

**Prevention**: Structure documents well and provide clear assistant instructions.

---

## 5. Code Interpreter File Output Not Found

**Error**: `image_file.file_id` referenced but file doesn't exist or can't be downloaded.

**Cause**: Files generated by Code Interpreter are temporary and may be cleaned up before retrieval.

**Solution**:
```typescript
// Retrieve and save immediately after run completes
const messages = await openai.beta.threads.messages.list(threadId);
const responseMessage = messages.data[0];

for (const content of responseMessage.content) {
  if (content.type === 'image_file') {
    try {
      const fileData = await openai.files.content(content.image_file.file_id);
      const buffer = Buffer.from(await fileData.arrayBuffer());
      fs.writeFileSync(`output_${content.image_file.file_id}.png`, buffer);
    } catch (error) {
      console.error('File no longer available:', error);
    }
  }
}
```

**Prevention**: Download generated files immediately after run completion.

**Source**: [Medium - Code Interpreter Tutorial](https://tmmtt.medium.com/openai-assistant-api-with-code-interpreter-e7f382bff83e)

---

## 6. Thread Message Limit Exceeded

**Error**: `400 Thread has exceeded the maximum number of messages (100,000)`.

**Cause**: Very long conversations hitting the 100k message limit.

**Solution**:
```typescript
async function archiveAndStartNewThread(oldThreadId: string, userId: string) {
  // Get conversation summary
  const messages = await openai.beta.threads.messages.list(oldThreadId, {
    limit: 50,
  });

  // Save to database
  await db.archiveThread(oldThreadId, messages.data);

  // Create new thread
  const newThread = await openai.beta.threads.create({
    metadata: {
      user_id: userId,
      previous_thread: oldThreadId,
    },
  });

  return newThread.id;
}
```

**Prevention**: Archive old threads and create new ones periodically.

---

## 7. Function Calling Timeout

**Error**: Run expires (status: `expired`) while waiting for tool outputs.

**Cause**: Tool execution takes too long (max 10 minutes for run).

**Solution**:
```typescript
if (run.status === 'requires_action') {
  const toolCalls = run.required_action.submit_tool_outputs.tool_calls;
  const toolOutputs = [];

  for (const toolCall of toolCalls) {
    try {
      // Add timeout to function execution
      const output = await Promise.race([
        executeFunction(toolCall.function.name, JSON.parse(toolCall.function.arguments)),
        new Promise((_, reject) =>
          setTimeout(() => reject(new Error('Function timeout')), 30000)
        ),
      ]);

      toolOutputs.push({
        tool_call_id: toolCall.id,
        output: JSON.stringify(output),
      });
    } catch (error) {
      // Return error as output
      toolOutputs.push({
        tool_call_id: toolCall.id,
        output: JSON.stringify({ error: error.message }),
      });
    }
  }

  await openai.beta.threads.runs.submitToolOutputs(threadId, run.id, {
    tool_outputs: toolOutputs,
  });
}
```

**Prevention**: Implement timeouts on function execution and return errors gracefully.

---

## 8. Streaming Run Interruption

**Error**: Stream connection closes unexpectedly or events stop arriving.

**Cause**: Network issues, server errors, or run failures.

**Solution**:
```typescript
async function streamWithRetry(threadId: string, assistantId: string) {
  try {
    const stream = await openai.beta.threads.runs.stream(threadId, {
      assistant_id: assistantId,
    });

    for await (const event of stream) {
      // Handle events
      if (event.event === 'error') {
        throw new Error('Stream error');
      }
    }
  } catch (error) {
    console.error('Stream interrupted:', error);

    // Fall back to polling
    const runs = await openai.beta.threads.runs.list(threadId, {
      limit: 1,
      order: 'desc',
    });

    const run = runs.data[0];
    return pollRunCompletion(threadId, run.id);
  }
}
```

**Prevention**: Implement fallback to polling if streaming fails.

**Source**: [OpenAI Community](https://community.openai.com/t/streaming-stopped-at-thread-run-requires-action-when-handling-openai-assistants-function-calling/943674)

---

## 9. Vector Store Quota Limits

**Error**: `429 Rate limit reached for vector store operations`.

**Cause**: Too many vector store operations or storage exceeded.

**Solution**:
- **Monitor storage**: Check `usage_bytes` regularly
- **Delete unused stores**: Clean up old vector stores
- **Batch operations**: Use batch file uploads instead of individual uploads

```typescript
async function cleanupOldVectorStores(keepDays = 30) {
  const stores = await openai.beta.vectorStores.list({ limit: 100 });

  for (const store of stores.data) {
    const ageSeconds = Date.now() / 1000 - store.created_at;
    const ageDays = ageSeconds / (60 * 60 * 24);

    if (ageDays > keepDays) {
      await openai.beta.vectorStores.del(store.id);
      console.log(`Deleted vector store: ${store.id}`);
    }
  }
}
```

**Prevention**: Set auto-expiration on vector stores and monitor costs.

---

## 10. File Upload Format Incompatibility

**Error**: `400 Unsupported file type for this tool`.

**Cause**: Uploading file format not supported by the tool.

**Solution**:
```typescript
const SUPPORTED_FORMATS = {
  code_interpreter: [
    '.c', '.cpp', '.csv', '.docx', '.html', '.java', '.json', '.md',
    '.pdf', '.php', '.pptx', '.py', '.rb', '.tex', '.txt', '.css',
    '.jpeg', '.jpg', '.js', '.gif', '.png', '.tar', '.ts', '.xlsx', '.xml', '.zip'
  ],
  file_search: [
    '.c', '.cpp', '.docx', '.html', '.java', '.json', '.md',
    '.pdf', '.php', '.pptx', '.py', '.rb', '.tex', '.txt', '.css', '.js', '.ts', '.go'
  ],
};

function validateFileFormat(filename: string, tool: 'code_interpreter' | 'file_search') {
  const ext = filename.substring(filename.lastIndexOf('.')).toLowerCase();

  if (!SUPPORTED_FORMATS[tool].includes(ext)) {
    throw new Error(`Unsupported file format for ${tool}: ${ext}`);
  }
}

// Validate before upload
validateFileFormat('data.csv', 'code_interpreter'); // OK
validateFileFormat('video.mp4', 'file_search'); // Throws error
```

**Prevention**: Validate file formats before uploading.

---

## 11. Assistant Instructions Token Limit

**Error**: `400 Instructions exceed maximum length`.

**Cause**: Instructions field exceeds 256,000 characters (v2 limit).

**Solution**:
- **Use file search**: Put long instructions in documents
- **Concise instructions**: Be clear and brief
- **System messages**: Use thread-level messages for context

```typescript
// ❌ Bad: Very long instructions
const assistant = await openai.beta.assistants.create({
  instructions: "..." // 300k characters
});

// ✅ Good: Concise instructions + file search
const assistant = await openai.beta.assistants.create({
  instructions: "You are a support assistant. Use file_search to find answers in the knowledge base.",
  tools: [{ type: "file_search" }],
  tool_resources: {
    file_search: {
      vector_store_ids: [vectorStoreId], // Long content here
    },
  },
});
```

**Prevention**: Keep instructions under 256k characters; use file search for knowledge.

---

## 12. Thread Deletion While Run Active

**Error**: `400 Cannot delete thread while run is active`.

**Cause**: Attempting to delete a thread that has an active run.

**Solution**:
```typescript
async function safeDeleteThread(threadId: string) {
  // Cancel active runs first
  const runs = await openai.beta.threads.runs.list(threadId);

  for (const run of runs.data) {
    if (['queued', 'in_progress'].includes(run.status)) {
      await openai.beta.threads.runs.cancel(threadId, run.id);

      // Wait for cancellation
      let runStatus = run;
      while (runStatus.status !== 'cancelled') {
        await new Promise(resolve => setTimeout(resolve, 500));
        runStatus = await openai.beta.threads.runs.retrieve(threadId, run.id);
      }
    }
  }

  // Now safe to delete
  await openai.beta.threads.del(threadId);
}
```

**Prevention**: Cancel all active runs before deleting threads.

---

## Quick Reference

| Error | Quick Fix |
|-------|-----------|
| Thread has active run | Cancel or wait for run completion |
| Polling timeout | Set timeout and cancel long runs |
| Vector store not ready | Wait for `status: "completed"` |
| File search no results | Check indexing complete, improve queries |
| Code Interpreter file lost | Download immediately after run |
| 100k message limit | Archive old threads, start new ones |
| Function timeout | Add timeouts to function execution |
| Stream interrupted | Fall back to polling |
| Vector store quota | Clean up old stores, use batch uploads |
| Unsupported file format | Validate file extensions before upload |
| Instructions too long | Use file search for knowledge |
| Can't delete thread | Cancel active runs first |

---

**Additional Resources**:
- [OpenAI Assistants API Docs](https://platform.openai.com/docs/assistants)
- [OpenAI Community Forum](https://community.openai.com/c/api/assistants-api/49)
- [API Reference](https://platform.openai.com/docs/api-reference/assistants)