[Bug] @ai-sdk/amazon-bedrock: Tool call IDs incompatible with Mistral models - "must be a-z, A-Z, 0-9, with a length of 9"

[arpanpal-at]

Description

When using Mistral models via @ai-sdk/amazon-bedrock, tool calling fails on multi-turn conversations because the tool call IDs generated by the Bedrock Converse API do not meet Mistral's strict format requirements.

Code to reproduce:

import {createAmazonBedrock} from '@ai-sdk/amazon-bedrock';
import {generateText, jsonSchema} from 'ai';

const bedrock = createAmazonBedrock({
    region: 'us-east-1',
    // ... credentials
});

const model = bedrock('mistral.ministral-3-14b-instruct');

const result = await generateText({
    model,
    tools: {
        searchWeb: {
            description: 'Search the web for information',
            parameters: jsonSchema({
                type: 'object',
                properties: {
                    query: {type: 'string', description: 'Search query'},
                },
                required: ['query'],
            }),
        },
    },
    toolChoice: 'auto',
    messages: [
        {
            role: 'user',
            content: 'Search for the projected revenue for Alphabet Inc. in 2026',
        },
    ],
    maxRetries: 1,
});

Expected Behavior

Tool calling should work correctly with Mistral models on Bedrock, similar to how it works with Anthropic models on Bedrock.

Actual Behavior

The first tool call succeeds, but when sending the tool result back for the next turn, the request fails with:

ValidationException: The model returned the following errors:
{
  "code": "validation_error",
  "message": "Tool call id was i-nKGDr5g but must be a-z, A-Z, 0-9, with a length of 9.
              Tool call id was i-nKGDr5g but must be a-z, A-Z, 0-9, with a length of 9.",
  "param": null,
  "type": "invalid_request_error"
}

Root Cause Analysis

1. Bedrock generates tool call IDs in its own format: tooluse_bpe71yCfRu2b5i-nKGDr5g
2. Mistral requires tool call IDs to match the regex ^[a-zA-Z0-9]{9}$:
   • Exactly 9 characters
   • Alphanumeric only (no underscores, hyphens, or prefixes)
3. When the tool result is sent back with the Bedrock-format ID, Mistral's validation rejects it

Related Issues

This is a known compatibility issue that has been addressed in other projects:

• opencode #1680 - Fixed via PR #2440
• https://huggingface.co/spaces/arterm-sedov/cmw-copilot/blob/main/docs/MISTRAL_TOOL_CALL_ID_FIX.md

Suggested Fix

Add Mistral-specific tool call ID normalization in @ai-sdk/amazon-bedrock. The opencode project implemented this via a normalizeMistralToolCallIds() function that:

1. Detects Mistral models by provider/model ID
2. Transforms tool call IDs to meet Mistral's requirements (first 9 alphanumeric characters)

Example transformation:

• tooluse_bpe71yCfRu2b5i-nKGDr5g → bpe71yCfR (9 alphanumeric chars)

Workaround

Currently, there is no workaround other than avoiding tool use with Mistral models on Bedrock, or implementing a custom transformation layer at the application level.

Additional Context

Full error response from Bedrock:

{
  "statusCode": 400,
  "responseHeaders": {
    "x-amzn-errortype": "ValidationException:http://internal.amazon.com/coral/com.amazon.bedrock/",
    "x-amzn-requestid": "1db5f47e-7335-4051-bea0-224852765024"
  },
  "responseBody": {
    "message": "The model returned the following errors: {\"code\":\"validation_error\",\"message\":\"Tool call id was i-nKGDr5g but must be a-z, A-Z, 0-9, with a length of 9.\"}"
  }
}

AI SDK Version

Environment:

• ai: 5.0.27
• @ai-sdk/amazon-bedrock: 3.0.19
• Node.js: 20.x
• AWS Region: us-east-1

Mistral models affected:

• mistral.mistral-large-2407-v1:0
• mistral.ministral-3-14b-instruct
• mistral.ministral-3-8b-instruct

Code of Conduct

• I agree to follow this project's Code of Conduct

[lgrammel]

Identify issue type

Identified as Bug
Confidence: High

Rationale

This is a concrete failure of existing Bedrock tool-calling behavior for supported Mistral models, not merely a request for new capability. The suggested normalization is a proposed fix for that incompatibility.

Evidence

• Multi-turn tool calling with Mistral models through @ai-sdk/amazon-bedrock fails with a Bedrock ValidationException.
• Bedrock tool call IDs do not satisfy Mistral's required nine-character alphanumeric format when tool results are sent back.
• The report includes reproducible code, affected package versions and models, the exact error, and expected versus actual behavior.