OpenAI Assistants API v2
Status: Production Ready (⚠️ Deprecated - Sunset August 26, 2026) Package: openai@6.16.0 Last Updated: 2026-01-21 v1 Deprecated: December 18, 2024 v2 Sunset: August 26, 2026 (migrate to Responses API)
⚠️ Deprecation Notice
OpenAI is deprecating Assistants API in favor of Responses API.
Timeline: v1 deprecated Dec 18, 2024 | v2 sunset August 26, 2026
Use this skill if: Maintaining legacy apps or migrating existing code (12-18 month window) Don't use if: Starting new projects (use openai-responses skill instead)
Migration: See references/migration-to-responses.md
Quick Start
npm install openai@6.16.0import OpenAI from 'openai';
const openai = new OpenAI({ apiKey: process.env.OPENAI_API_KEY });
// 1. Create assistant
const assistant = await openai.beta.assistants.create({
name: "Math Tutor",
instructions: "You are a math tutor. Use code interpreter for calculations.",
tools: [{ type: "code_interpreter" }],
model: "gpt-5",
});
// 2. Create thread
const thread = await openai.beta.threads.create();
// 3. Add message
await openai.beta.threads.messages.create(thread.id, {
role: "user",
content: "Solve: 3x + 11 = 14",
});
// 4. Run assistant
const run = await openai.beta.threads.runs.create(thread.id, {
assistant_id: assistant.id,
});
// 5. Poll for completion
let status = await openai.beta.threads.runs.retrieve(thread.id, run.id);
while (status.status !== 'completed') {
await new Promise(r => setTimeout(r, 1000));
status = await openai.beta.threads.runs.retrieve(thread.id, run.id);
}
// 6. Get response
const messages = await openai.beta.threads.messages.list(thread.id);
console.log(messages.data[0].content[0].text.value);Core Concepts
Four Main Objects:
- Assistants: Configured AI with instructions (max 256k chars in v2, was 32k in v1), model, tools, metadata
- Threads: Conversation containers with persistent message history (max 100k messages)
- Messages: User/assistant messages with optional file attachments
- Runs: Async execution with states (queued, in_progress, requires_action, completed, failed, expired)
Key API Patterns
Assistants
const assistant = await openai.beta.assistants.create({
model: "gpt-5",
instructions: "System prompt (max 256k chars in v2)",
tools: [{ type: "code_interpreter" }, { type: "file_search" }],
tool_resources: { file_search: { vector_store_ids: ["vs_123"] } },
});Key Limits: 256k instruction chars (v2), 128 tools max, 16 metadata pairs
Threads & Messages
// Create thread with messages
const thread = await openai.beta.threads.create({
messages: [{ role: "user", content: "Hello" }],
});
// Add message with attachments
await openai.beta.threads.messages.create(thread.id, {
role: "user",
content: "Analyze this",
attachments: [{ file_id: "file_123", tools: [{ type: "code_interpreter" }] }],
});
// List messages
const msgs = await openai.beta.threads.messages.list(thread.id);Key Limits: 100k messages per thread
Runs
// Create run with optional overrides
const run = await openai.beta.threads.runs.create(thread.id, {
assistant_id: "asst_123",
additional_messages: [{ role: "user", content: "Question" }],
max_prompt_tokens: 1000,
max_completion_tokens: 500,
});
// Poll until complete
let status = await openai.beta.threads.runs.retrieve(thread.id, run.id);
while (['queued', 'in_progress'].includes(status.status)) {
await new Promise(r => setTimeout(r, 1000));
status = await openai.beta.threads.runs.retrieve(thread.id, run.id);
}Run States: queued → in_progress → requires_action (function calling) / completed / failed / cancelled / expired (10 min max)
Streaming
const stream = await openai.beta.threads.runs.stream(thread.id, { assistant_id });
for await (const event of stream) {
if (event.event === 'thread.message.delta') {
process.stdout.write(event.data.delta.content?.[0]?.text?.value || '');
}
}Key Events: thread.run.created, thread.message.delta (streaming content), thread.run.step.delta (tool progress), thread.run.completed, thread.run.requires_action (function calling)
Tools
Code Interpreter
Runs Python code in sandbox. Generates charts, processes files (CSV, JSON, PDF, images). Max 512MB per file.
// Attach file to message
attachments: [{ file_id: "file_123", tools: [{ type: "code_interpreter" }] }]
// Access generated files
for (const content of message.content) {
if (content.type === 'image_file') {
const fileContent = await openai.files.content(content.image_file.file_id);
}
}File Search (RAG)
Semantic search with vector stores. 10,000 files max (v2, was 20 in v1). Pricing: $0.10/GB/day (1GB free).
// Create vector store
const vs = await openai.beta.vectorStores.create({ name: "Docs" });
await openai.beta.vectorStores.files.create(vs.id, { file_id: "file_123" });
// Wait for indexing
let store = await openai.beta.vectorStores.retrieve(vs.id);
while (store.status === 'in_progress') {
await new Promise(r => setTimeout(r, 2000));
store = await openai.beta.vectorStores.retrieve(vs.id);
}
// Use in assistant
tool_resources: { file_search: { vector_store_ids: [vs.id] } }⚠️ Wait for status: 'completed' before using
Function Calling
Submit tool outputs when run.status === 'requires_action':
if (run.status === 'requires_action') {
const toolCalls = run.required_action.submit_tool_outputs.tool_calls;
const outputs = toolCalls.map(tc => ({
tool_call_id: tc.id,
output: JSON.stringify(yourFunction(JSON.parse(tc.function.arguments))),
}));
run = await openai.beta.threads.runs.submitToolOutputs(thread.id, run.id, {
tool_outputs: outputs,
});
}File 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 (512MB max)
File Search:.c,.cpp,.docx,.html,.java,.json,.md,.pdf,.php,.pptx,.py,.rb,.tex,.txt,.css,.js,.ts,.go (512MB max)
Known Issues
1. Thread Already Has Active Run
Error: 400 Can't add messages to thread_xxx while a run run_xxx is active.Fix: Cancel active run first: await openai.beta.threads.runs.cancel(threadId, runId)
2. Run Polling Timeout / Incomplete Status
Error: OpenAIError: Final run has not been receivedWhy It Happens: Long-running tasks may exceed polling windows or finish with incomplete status Prevention: Handle incomplete runs gracefully
try {
const stream = await openai.beta.threads.runs.stream(thread.id, { assistant_id });
for await (const event of stream) {
if (event.event === 'thread.message.delta') {
process.stdout.write(event.data.delta.content?.[0]?.text?.value || '');
}
}
} catch (error) {
if (error.message?.includes('Final run has not been received')) {
// Run ended with 'incomplete' status - thread can continue
const run = await openai.beta.threads.runs.retrieve(thread.id, runId);
if (run.status === 'incomplete') {
// Handle: prompt user to continue, reduce max_completion_tokens, etc.
}
}
}Source: GitHub Issues #945, #1306, #1439
3. Vector Store Not Ready Using vector store before indexing completes. Fix: Poll vectorStores.retrieve() until status === 'completed' (see File Search section)
4. File Upload Format Issues Unsupported file formats cause silent failures. Fix: Validate file extensions before upload (see File Formats section)
5. Vector Store Upload Documentation Incorrect
Error: No 'files' provided to processWhy It Happens: Official documentation shows incorrect usage of uploadAndPoll Prevention: Wrap file streams in {files: [...]} object
// ✅ Correct
await openai.beta.vectorStores.fileBatches.uploadAndPoll(vectorStoreId, {
files: fileStreams
});
// ❌ Wrong (shown in official docs)
await openai.beta.vectorStores.fileBatches.uploadAndPoll(vectorStoreId, fileStreams);Source: GitHub Issue #1337
6. Reasoning Models Reject Temperature Parameter
Error: Unsupported parameter: 'temperature' is not supported with this modelWhy It Happens: When updating assistant to o3-mini/o1-preview/o1-mini, old temperature settings persist Prevention: Explicitly set temperature to null
await openai.beta.assistants.update(assistantId, {
model: 'o3-mini',
reasoning_effort: 'medium',
temperature: null, // ✅ Must explicitly clear
top_p: null
});Source: GitHub Issue #1318
7. uploadAndPoll Returns Vector Store ID Instead of Batch ID
Error: Invalid 'batch_id': 'vs_...'. Expected an ID that begins with 'vsfb_'.Why It Happens: uploadAndPoll returns vector store object instead of batch object Prevention: Use alternative methods to get batch ID
// Option 1: Use createAndPoll after separate upload
const batch = await openai.vectorStores.fileBatches.createAndPoll(
vectorStoreId,
{ file_ids: uploadedFileIds }
);
// Option 2: List batches to find correct ID
const batches = await openai.vectorStores.fileBatches.list(vectorStoreId);
const batchId = batches.data[0].id; // starts with 'vsfb_'Source: GitHub Issue #1700
8. Vector Store File Delete Affects All Stores Warning: Deleting a file from one vector store removes it from ALL vector stores
// ❌ This deletes file from VS_A, VS_B, AND VS_C
await openai.vectorStores.files.delete('VS_A', 'file-xxx');Why It Happens: SDK or API bug - delete operation has global effect Prevention: Avoid sharing files across multiple vector stores if selective deletion is needed Source: GitHub Issue #1710
9. Memory Leak in Large File Uploads (Community-sourced) Source: GitHub Issue #1052 | Status: OPEN Impact: ~44MB leaked per 22MB file upload in long-running servers Why It Happens: When uploading large files from streams (S3, etc.) using vectorStores.fileBatches.uploadAndPoll, memory may not be released after upload completes Verified: Maintainer acknowledged, reduced in v4.58.1 but not eliminated Workaround: Monitor memory usage in long-lived servers; restart periodically or use separate worker processes
10. Thread Already Has Active Run - Race Condition (Community-sourced) Enhancement to Issue #1: When canceling an active run, race conditions may occur if the run completes before cancellation
async function createRunSafely(threadId: string, assistantId: string) {
// Check for active runs first
const runs = await openai.beta.threads.runs.list(threadId, { limit: 1 });
const activeRun = runs.data.find(r =>
['queued', 'in_progress', 'requires_action'].includes(r.status)
);
if (activeRun) {
try {
await openai.beta.threads.runs.cancel(threadId, activeRun.id);
// Wait for cancellation to complete
let run = await openai.beta.threads.runs.retrieve(threadId, activeRun.id);
while (run.status === 'cancelling') {
await new Promise(r => setTimeout(r, 500));
run = await openai.beta.threads.runs.retrieve(threadId, activeRun.id);
}
} catch (error) {
// Ignore "already completed" errors - run finished naturally
if (!error.message?.includes('completed')) throw error;
}
}
return openai.beta.threads.runs.create(threadId, { assistant_id: assistantId });
}Source: OpenAI Community Forum
See references/top-errors.md for complete catalog.
Relationship to Other Skills
openai-api (Chat Completions): Stateless, manual history, direct responses. Use for simple generation.
openai-responses (Responses API): ✅ Recommended for new projects. Better reasoning, modern MCP integration, active development.
openai-assistants: ⚠️ Deprecated H1 2026. Use for legacy apps only. Migration: references/migration-to-responses.md
v1 to v2 Migration
v1 deprecated: Dec 18, 2024
Key Changes: retrieval → file_search, vector stores (10k files vs 20), 256k instructions (vs 32k), message-level file attachments
See references/migration-from-v1.md
Templates: templates/basic-assistant.ts, code-interpreter-assistant.ts, file-search-assistant.ts, function-calling-assistant.ts, streaming-assistant.ts
References: references/top-errors.md, thread-lifecycle.md, vector-stores.md, migration-to-responses.md, migration-from-v1.md
Related Skills: openai-responses (recommended), openai-api
Last Updated: 2026-01-21 Package: openai@6.16.0 Status: Production Ready (⚠️ Deprecated - Sunset August 26, 2026) Changes: Added 6 new known issues (vector store upload bugs, o3-mini temperature, memory leak), enhanced streaming error handling