anthropic provider: toolChoice 'none' strips tools from request, causing empty response with tool_use history #12378

import { anthropic } from '@ai-sdk/anthropic';
import { generateText, tool } from 'ai';
import { z } from 'zod';

const result = await generateText({
  model: anthropic('claude-sonnet-4-20250514'),
  tools: {
    search: tool({
      description: 'Search for information',
      parameters: z.object({ query: z.string() }),
      execute: async ({ query }) => `Results for "${query}"`,
    }),
  },
  toolChoice: 'auto',
  maxSteps: 3,
  prompt: 'Search for "climate change" and summarize the results',
  // On the last step, set toolChoice to 'none' to force a text response
  // This is a common pattern for agentic loops that need to guarantee
  // the final step produces text rather than another tool call
});

// The final step will have empty text because the provider strips tools
// from the request, and the Anthropic API returns content: [] when it
// sees tool_use/tool_result blocks in history but no tools parameter

import { anthropic } from '@ai-sdk/anthropic';

const model = anthropic('claude-sonnet-4-20250514');

// Simulate a multi-step conversation where step 1 used tools
const result = await model.doGenerate({
  inputFormat: 'messages',
  mode: {
    type: 'regular',
    tools: [
      {
        type: 'function',
        name: 'search',
        description: 'Search for info',
        parameters: { type: 'object', properties: { query: { type: 'string' } } },
      },
    ],
    toolChoice: { type: 'none' },
  },
  prompt: [
    { role: 'user', content: [{ type: 'text', text: 'Search for climate change' }] },
    {
      role: 'assistant',
      content: [
        { type: 'tool-call', toolCallId: 'tc1', toolName: 'search', args: { query: 'climate change' } },
      ],
    },
    {
      role: 'tool',
      content: [{ type: 'tool-result', toolCallId: 'tc1', result: 'Some results' }],
    },
    { role: 'user', content: [{ type: 'text', text: 'Now summarize what you found' }] },
  ],
});

console.log(result.text); // '' (empty string)
console.log(result.finishReason); // 'stop'
// The API returned content: [] with ~8 output tokens (just stop tokens)

// Convert tool call/result messages to text descriptions
const cleanedMessages = messages.map(msg => {
  // ... replace tool-call/tool-result parts with text descriptions
});
// Now safe to remove tools since history has no tool blocks