Weird error with toolcalling on local model

[pwilkin]

Description

I was testing a local model (IQuest-Coder-40B-Instruct) to check how well it handles agentic coding. However, in OpenCode I'm getting:

AI_InvalidResponseDataError: Expected 'function.name' to be a string.

I thought it was the model being obtuse or maybe my parser not working correctly (I'm using an experimental parser for Llama.cpp), so I put an MITM proxy to capture the deltas. Here are the logs:

data: {"choices":[{"finish_reason":null,"index":0,"delta":{"role":"assistant","content":null}}],"created":1767366981,"id":"chatcmpl-q7mP1rgtuJhfQWiVh6lrBQsS4SZcuwKT","model":"IQuest-Coder-V1-40B-Instruct-IQ4_XS.gguf","system_fingerprint":"b7638-73c7088d3","object":"chat.completion.chunk"}
data: {"choices":[{"finish_reason":null,"index":0,"delta":{"tool_calls":[{"index":0,"id":"TeCh7VHcc8zpP5G4zN5f0NKRppnBIOwT","type":"function","function":{"arguments":""}}]}}],"created":1767366982,"id":"chatcmpl-q7mP1rgtuJhfQWiVh6lrBQsS4SZcuwKT","model":"IQuest-Coder-V1-40B-Instruct-IQ4_XS.gguf","system_fingerprint":"b7638-73c7088d3","object":"chat.completion.chunk"}
data: {"choices":[{"finish_reason":null,"index":0,"delta":{"tool_calls":[{"index":0,"id":"TeCh7VHcc8zpP5G4zN5f0NKRppnBIOwT","type":"function","function":{"name":"bash","arguments":"{"}}]}}],"created":1767366985,"id":"chatcmpl-q7mP1rgtuJhfQWiVh6lrBQsS4SZcuwKT","model":"IQuest-Coder-V1-40B-Instruct-IQ4_XS.gguf","system_fingerprint":"b7638-73c7088d3","object":"chat.completion.chunk"}
data: {"choices":[{"finish_reason":null,"index":0,"delta":{"tool_calls":[{"index":0,"function":{"arguments":"\""}}]}}],"created":1767366988,"id":"chatcmpl-q7mP1rgtuJhfQWiVh6lrBQsS4SZcuwKT","model":"IQuest-Coder-V1-40B-Instruct-IQ4_XS.gguf","system_fingerprint":"b7638-73c7088d3","object":"chat.completion.chunk"}
data: {"choices":[{"finish_reason":null,"index":0,"delta":{"tool_calls":[{"index":0,"function":{"arguments":"command"}}]}}],"created":1767366988,"id":"chatcmpl-q7mP1rgtuJhfQWiVh6lrBQsS4SZcuwKT","model":"IQuest-Coder-V1-40B-Instruct-IQ4_XS.gguf","system_fingerprint":"b7638-73c7088d3","object":"chat.completion.chunk"}
data: {"choices":[{"finish_reason":null,"index":0,"delta":{"tool_calls":[{"index":0,"function":{"arguments":"\":"}}]}}],"created":1767366989,"id":"chatcmpl-q7mP1rgtuJhfQWiVh6lrBQsS4SZcuwKT","model":"IQuest-Coder-V1-40B-Instruct-IQ4_XS.gguf","system_fingerprint":"b7638-73c7088d3","object":"chat.completion.chunk"}
data: {"choices":[{"finish_reason":null,"index":0,"delta":{"tool_calls":[{"index":0,"function":{"arguments":" \""}}]}}],"created":1767366990,"id":"chatcmpl-q7mP1rgtuJhfQWiVh6lrBQsS4SZcuwKT","model":"IQuest-Coder-V1-40B-Instruct-IQ4_XS.gguf","system_fingerprint":"b7638-73c7088d3","object":"chat.completion.chunk"}
data: {"choices":[{"finish_reason":null,"index":0,"delta":{"tool_calls":[{"index":0,"function":{"arguments":"ls"}}]}}],"created":1767366990,"id":"chatcmpl-q7mP1rgtuJhfQWiVh6lrBQsS4SZcuwKT","model":"IQuest-Coder-V1-40B-Instruct-IQ4_XS.gguf","system_fingerprint":"b7638-73c7088d3","object":"chat.completion.chunk"}
data: {"choices":[{"finish_reason":null,"index":0,"delta":{"tool_calls":[{"index":0,"function":{"arguments":" -"}}]}}],"created":1767366991,"id":"chatcmpl-q7mP1rgtuJhfQWiVh6lrBQsS4SZcuwKT","model":"IQuest-Coder-V1-40B-Instruct-IQ4_XS.gguf","system_fingerprint":"b7638-73c7088d3","object":"chat.completion.chunk"}
data: {"choices":[{"finish_reason":null,"index":0,"delta":{"tool_calls":[{"index":0,"function":{"arguments":"la"}}]}}],"created":1767366991,"id":"chatcmpl-q7mP1rgtuJhfQWiVh6lrBQsS4SZcuwKT","model":"IQuest-Coder-V1-40B-Instruct-IQ4_XS.gguf","system_fingerprint":"b7638-73c7088d3","object":"chat.completion.chunk"}
data: {"choices":[{"finish_reason":null,"index":0,"delta":{"tool_calls":[{"index":0,"function":{"arguments":"\","}}]}}],"created":1767366992,"id":"chatcmpl-q7mP1rgtuJhfQWiVh6lrBQsS4SZcuwKT","model":"IQuest-Coder-V1-40B-Instruct-IQ4_XS.gguf","system_fingerprint":"b7638-73c7088d3","object":"chat.completion.chunk"}
data: {"choices":[{"finish_reason":null,"index":0,"delta":{"tool_calls":[{"index":0,"function":{"arguments":" \""}}]}}],"created":1767366992,"id":"chatcmpl-q7mP1rgtuJhfQWiVh6lrBQsS4SZcuwKT","model":"IQuest-Coder-V1-40B-Instruct-IQ4_XS.gguf","system_fingerprint":"b7638-73c7088d3","object":"chat.completion.chunk"}
data: {"choices":[{"finish_reason":null,"index":0,"delta":{"tool_calls":[{"index":0,"function":{"arguments":"description"}}]}}],"created":1767366993,"id":"chatcmpl-q7mP1rgtuJhfQWiVh6lrBQsS4SZcuwKT","model":"IQuest-Coder-V1-40B-Instruct-IQ4_XS.gguf","system_fingerprint":"b7638-73c7088d3","object":"chat.completion.chunk"}
data: {"choices":[{"finish_reason":null,"index":0,"delta":{"tool_calls":[{"index":0,"function":{"arguments":"\":"}}]}}],"created":1767366994,"id":"chatcmpl-q7mP1rgtuJhfQWiVh6lrBQsS4SZcuwKT","model":"IQuest-Coder-V1-40B-Instruct-IQ4_XS.gguf","system_fingerprint":"b7638-73c7088d3","object":"chat.completion.chunk"}
data: {"choices":[{"finish_reason":null,"index":0,"delta":{"tool_calls":[{"index":0,"function":{"arguments":" \""}}]}}],"created":1767366994,"id":"chatcmpl-q7mP1rgtuJhfQWiVh6lrBQsS4SZcuwKT","model":"IQuest-Coder-V1-40B-Instruct-IQ4_XS.gguf","system_fingerprint":"b7638-73c7088d3","object":"chat.completion.chunk"}
data: {"choices":[{"finish_reason":null,"index":0,"delta":{"tool_calls":[{"index":0,"function":{"arguments":"List"}}]}}],"created":1767366996,"id":"chatcmpl-q7mP1rgtuJhfQWiVh6lrBQsS4SZcuwKT","model":"IQuest-Coder-V1-40B-Instruct-IQ4_XS.gguf","system_fingerprint":"b7638-73c7088d3","object":"chat.completion.chunk"}
data: {"choices":[{"finish_reason":null,"index":0,"delta":{"tool_calls":[{"index":0,"function":{"arguments":" files"}}]}}],"created":1767366997,"id":"chatcmpl-q7mP1rgtuJhfQWiVh6lrBQsS4SZcuwKT","model":"IQuest-Coder-V1-40B-Instruct-IQ4_XS.gguf","system_fingerprint":"b7638-73c7088d3","object":"chat.completion.chunk"}
data: {"choices":[{"finish_reason":null,"index":0,"delta":{"tool_calls":[{"index":0,"function":{"arguments":" in"}}]}}],"created":1767366997,"id":"chatcmpl-q7mP1rgtuJhfQWiVh6lrBQsS4SZcuwKT","model":"IQuest-Coder-V1-40B-Instruct-IQ4_XS.gguf","system_fingerprint":"b7638-73c7088d3","object":"chat.completion.chunk"}
data: {"choices":[{"finish_reason":null,"index":0,"delta":{"tool_calls":[{"index":0,"function":{"arguments":" current"}}]}}],"created":1767366998,"id":"chatcmpl-q7mP1rgtuJhfQWiVh6lrBQsS4SZcuwKT","model":"IQuest-Coder-V1-40B-Instruct-IQ4_XS.gguf","system_fingerprint":"b7638-73c7088d3","object":"chat.completion.chunk"}
data: {"choices":[{"finish_reason":null,"index":0,"delta":{"tool_calls":[{"index":0,"function":{"arguments":" directory"}}]}}],"created":1767366998,"id":"chatcmpl-q7mP1rgtuJhfQWiVh6lrBQsS4SZcuwKT","model":"IQuest-Coder-V1-40B-Instruct-IQ4_XS.gguf","system_fingerprint":"b7638-73c7088d3","object":"chat.completion.chunk"}
data: {"choices":[{"finish_reason":null,"index":0,"delta":{"tool_calls":[{"index":0,"function":{"arguments":"\"}"}}]}}],"created":1767367000,"id":"chatcmpl-q7mP1rgtuJhfQWiVh6lrBQsS4SZcuwKT","model":"IQuest-Coder-V1-40B-Instruct-IQ4_XS.gguf","system_fingerprint":"b7638-73c7088d3","object":"chat.completion.chunk"}
data: {"choices":[{"finish_reason":"tool_calls","index":0,"delta":{}}],"created":1767367005,"id":"chatcmpl-q7mP1rgtuJhfQWiVh6lrBQsS4SZcuwKT","model":"IQuest-Coder-V1-40B-Instruct-IQ4_XS.gguf","system_fingerprint":"b7638-73c7088d3","object":"chat.completion.chunk"}
data: {"choices":[],"created":1767367005,"id":"chatcmpl-q7mP1rgtuJhfQWiVh6lrBQsS4SZcuwKT","model":"IQuest-Coder-V1-40B-Instruct-IQ4_XS.gguf","system_fingerprint":"b7638-73c7088d3","object":"chat.completion.chunk","usage":{"completion_tokens":31,"prompt_tokens":11020,"total_tokens":11051},"timings":{"cache_n":10245,"prompt_n":775,"prompt_ms":225787.145,"prompt_per_token_ms":291.3382516129032,"prompt_per_second":3.432436332901061,"predicted_n":31,"predicted_ms":23536.925,"predicted_per_token_ms":759.2556451612903,"predicted_per_second":1.3170794400712922}}
data: [DONE]

This looks to be a perfectly valid tool call - why isn't it getting accepted?

OpenCode version

1.0.223

Steps to reproduce

No response

Screenshot and/or share link

No response

Operating System

Ubuntu 25.10

Terminal

Terminology

[github-actions]

This issue might be a duplicate of existing issues. Please check:

• OpenCode v1.0.25 Hangs Indefinitely with LM Studio + Qwen Models Due to Empty tool_calls Array #4255: OpenCode v1.0.25 Hangs Indefinitely with LM Studio + Qwen Models Due to Empty tool_calls Array - describes similar tool calling issues with local models and provides detailed investigation
• Tool Calling Issues with Open Source Models in OpenCode #234: Tool Calling Issues with Open Source Models in OpenCode - documents compatibility challenges with tool calling on various local models
• Opencode with GLM 4.5 String issue #1880: Opencode with GLM 4.5 String issue - related AI_InvalidResponseDataError with streaming responses
• Local Ollama models are not agentic #5694: Local Ollama models are not agentic - reports tool calling failures with local Ollama models

Feel free to ignore if none of these address your specific case.

[thdxr]

To stay organized issues are automatically closed after 90 days of no activity. If the issue is still relevant please open a new one.

[nunodonato]

also getting this with qwen3.5 and xml tool parser

[wattmto]

Since vercel/ai#14760 was merged, it might be fixed once it's released and pulled into OpenCode.

[dfischer-mw]

Since vercel/ai#14760 was merged, it might be fixed once it's released and pulled into OpenCode.

Was it tho? Getting same error still.

[pwilkin]

FWIW, the reason for this was the sending of a tool call block without the function name in the first chunk. This is not incorrect per OpenAI spec, but I nevertheless patched the llama.cpp parser not to do that (it now waits until it has function name and always sends it in the first chunk).

[Acsriot94]

Getting this error constnatly.