openaiCompatible: summarize({ maxLength }) sends no token cap

TanStack AI version

@tanstack/ai 0.54.0, @tanstack/ai-openai 0.22.6 (current main)

Framework/Library version

Any (server-side, framework-independent)

Describe the bug and the steps to reproduce it

summarize({ maxLength }) sends no output token cap for any provider reached through openaiCompatible (DeepSeek, Moonshot/Kimi, Together, Fireworks, Qwen, vLLM, and others).

openaiCompatible has no summarize factory. To summarize, you wrap the text adapter in ChatStreamSummarizeAdapter. That wrapper chooses the token key from its own name, using MAX_TOKENS_KEY_BY_ADAPTER in packages/ai/src/activities/summarize/chat-stream-summarize.ts. That map only has first-party names (openai, anthropic, groq, llmgateway, cloudflare, ...). A compatible provider's name is chosen by the user, so it is never in the map:

• With the default name chat-stream-summarize, the cap is dropped.
• With the provider name, for example deepseek, the cap is dropped.
• With openai, the key is max_output_tokens. That is the Responses API key, and the Chat Completions endpoint ignores it.

In each case, the SDK logs a warning and sends the request without max_tokens or max_completion_tokens. Only the prompt asks the model to stay short.

Steps:

import { summarize, ChatStreamSummarizeAdapter } from '@tanstack/ai'
import { openaiCompatible } from '@tanstack/ai-openai/compatible'

const deepseek = openaiCompatible({
  name: 'deepseek',
  baseURL: 'https://api.deepseek.com/v1',
  apiKey: process.env.DEEPSEEK_API_KEY ?? '',
  models: ['deepseek-chat'],
})

const adapter = new ChatStreamSummarizeAdapter(
  deepseek('deepseek-chat'),
  'deepseek-chat',
  'deepseek',
)

await summarize({ adapter, text: longText, maxLength: 100 })

Expected: the Chat Completions request body contains an output cap (max_tokens or max_completion_tokens).

Actual: the request body has no output cap. The logger warns maxLength=100 could not be mapped to a provider token key for adapter name "deepseek".

Possible fixes:

1. Choose the key from the wrapped adapter's wire API, not from a name. Every Chat Completions adapter on OpenAIBaseChatCompletionsTextAdapter would get a Chat Completions key. This also removes the need for per-gateway entries such as llmgateway and cloudflare.
2. Add a summarize factory to openaiCompatible, with an optional maxTokensKey setting.

Related: the other openaiCompatible gap, reasoning deltas (delta.reasoning_content / delta.reasoning) that are never surfaced, is tracked in #982 and fixed in #1367.

Your Minimal, Reproducible Example - (Sandbox Highly Recommended)

See the snippet above. Code path: ChatStreamSummarizeAdapter.buildTextOptions, then isKnownMaxTokensAdapter(this.name) and applyMaxLength.

Do you intend to try to help solve this bug with your own PR?

Maybe, I'll investigate and start debugging