Tool calls missing arguments field causing AI_TypeValidationError (anthropic haiku-4.5) #287
Description
When using Anthropic Claude Haiku through OpenRouter, tool calls are returned without the required arguments field, causing AI SDK v5 validation to fail.
Error:
AI_TypeValidationError: Invalid input: expected string, received undefined at path ["choices",0,"message","tool_calls",0,"function","arguments"]
Response from OpenRouter:
{
"tool_calls": [{
"id": "toolu_bdrk_...",
"type": "function",
"function": {
"name": "list_available_components"
// Missing: "arguments" field
}
}]
}
Expected: "arguments": "{}" or "arguments": ""
Version: @openrouter/[email protected], ai@^5.0.0
AI_APICallError: Invalid JSON response
❯ ../../node_modules/@openrouter/ai-sdk-provider/node_modules/.pnpm/@[email protected][email protected]/node_modules/@ai-sdk/provider-utils/src/response-handler.ts:151:13
❯ postToApi ../../node_modules/@openrouter/ai-sdk-provider/node_modules/.pnpm/@[email protected][email protected]/node_modules/@ai-sdk/provider-utils/src/post-to-api.ts:136:14
❯ OpenRouterChatLanguageModel.doGenerate ../../node_modules/@openrouter/ai-sdk-provider/src/chat/index.ts:226:55
❯ fn node_modules/ai/src/generate-text/generate-text.ts:389:32
❯ node_modules/ai/src/telemetry/record-span.ts:18:22
❯ _retryWithExponentialBackoff node_modules/ai/src/util/retry-with-exponential-backoff.ts:96:12
❯ fn node_modules/ai/src/generate-text/generate-text.ts:345:34
❯ node_modules/ai/src/telemetry/record-span.ts:18:22
❯ Module.generateText node_modules/ai/src/generate-text/generate-text.ts:281:12
Caused by: AI_TypeValidationError: Type validation failed: Value: {"id":"gen-1765191297-cCNRPMadSsGK3fCO5kmn","provider":"Amazon Bedrock","model":"anthropic/claude-haiku-4.5","object":"chat.completion","created":1765191297,"choices":[{"logprobs":null,"finish_reason":"tool_calls","native_finish_reason":"tool_calls","index":0,"message":{"role":"assistant","content":"","refusal":null,"reasoning":null,"tool_calls":[{"id":"toolu_bdrk_015kDTLLfWrSmkqgiahrdeCV","index":0,"type":"function","function":{"name":"list_available_components"}}]}}],"usage":{"prompt_tokens":5435,"completion_tokens":39,"total_tokens":5474,"cost":0.0010382,"is_byok":false,"prompt_tokens_details":{"cached_tokens":5102,"audio_tokens":0,"video_tokens":0},"cost_details":{"upstream_inference_cost":null,"upstream_inference_prompt_cost":0.0008432,"upstream_inference_completions_cost":0.000195},"completion_tokens_details":{"reasoning_tokens":0,"image_tokens":0}}}.
Error message: [{"code":"invalid_union","errors":[[{"expected":"string","code":"invalid_type","path":["choices",0,"message","tool_calls",0,"function","arguments"],"message":"Invalid input: expected string, received undefined"}],[{"expected":"object","code":"invalid_type","path":["error"],"message":"Invalid input: expected object, received undefined"}]],"path":[],"message":"Invalid input"}]
❯ Object.validate ../../node_modules/@openrouter/ai-sdk-provider/node_modules/.pnpm/@[email protected][email protected]/node_modules/@ai-sdk/provider-utils/src/validator.ts:69:18
❯ safeValidateTypes ../../node_modules/@openrouter/ai-sdk-provider/node_modules/.pnpm/@[email protected][email protected]/node_modules/@ai-sdk/provider-utils/src/validate-types.ts:64:20