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summarize() sends temperature 0.3 to models that reject sampling parameters (e.g. claude-sonnet-5-5)

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Since Oct 10, 2026.

  • #1705 by @harshlocham — open

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Description

has-pr waiting-on: maintainer
TanStack AI version

@tanstack/ai 0.68.0, @tanstack/ai-anthropic 0.21.1

Framework/Library version

TypeScript 7.0.2 (framework-independent)

Describe the bug and the steps to reproduce it

ChatStreamSummarizeAdapter.buildTextOptions always calls applyDefaultTemperature(this.name, 0.3, working) (chat-stream-summarize.ts#L375), which adds temperature: 0.3 unless the caller already set one. Several Anthropic models don't accept sampling parameters: their model meta leaves out AnthropicSamplingOptions (claude-sonnet-5, claude-sonnet-5-5, claude-opus-4-7, claude-opus-4-8, claude-fable-5, claude-fable-5-1, claude-haiku-5-5), and the AnthropicMaxTokensOptions doc comment notes that Fable 5 and Opus 4.7/4.8 reject them outright while Sonnet 5 returns a 400 for a non-default value. summarize() against these models still sends temperature: 0.3.

The documented opt-out ("the caller always wins") isn't available either: temperature isn't part of these models' modelOptions type, so summarize({ ..., modelOptions: { temperature: 1 } }) fails with TS2353.

Steps:

import { summarize } from "@tanstack/ai";
import { createAnthropicSummarize } from "@tanstack/ai-anthropic";

const bodies: Array<Record<string, unknown>> = [];
const fetch = async (_url: string, init: RequestInit) => {
  bodies.push(JSON.parse(String(init.body)));
  return new Response(JSON.stringify({ type: "error", error: { type: "invalid_request_error", message: "captured" } }), {
    status: 400,
    headers: { "content-type": "application/json" },
  });
};

try {
  await summarize({
    adapter: createAnthropicSummarize("claude-sonnet-5-5", "key", { fetch, maxRetries: 0 }),
    text: "Some long text.",
  });
} catch {}

console.log(bodies[0]);

The captured request contains "model": "claude-sonnet-5-5", "temperature": 0.3, "max_tokens": 128000.

Expected: no temperature for models that reject sampling parameters, or a typed way to turn the default off.

A possible fix: let the text adapter report whether its model accepts sampling parameters (the provider model meta already knows) and skip the default when it doesn't. Meanwhile we wrap the text adapter handed to ChatStreamSummarizeAdapter and drop temperature from modelOptions in chatStream.

Possibly related: Anthropic's model docs list claude-opus-5 and claude-opus-5-5 as rejecting sampling parameters as well, while their model meta still includes AnthropicSamplingOptions. Might be worth a check.

Your Minimal, Reproducible Example - (Sandbox Highly Recommended)

Inline above.

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