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Devstral via LiteLLM OpenAI-compatible fails with invalid_request_message_order on first file edit #6346
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Description
Description
When OpenCode is configured to use Devstral (devstral-2512) through the OpenAI-compatible provider path (LiteLLM OpenAI-compatible endpoint), the run fails as soon as the agent performs an edit operation (i.e., when it tries to edit a file and then continue). The failure occurs immediately at the point where OpenCode attempts to proceed after the edit.
Error message:
litellm.BadRequestError: MistralException - {"object":"error","message":"Expected last role User or Tool (or Assistant with prefix True) for serving but got assistant","type":"invalid_request_message_order","param":null,"code":"3230"}. Received Model Group=devstral-2512 Available Model Group Fallbacks=NoneThe same workflow does not fail when Devstral is used through the native Mistral provider path (mistral_v1).
Our config:
{
"$schema": "https://opencode.ai/config.json",
"tools": {
"bash": true,
"edit": true,
"write": true,
"read": true,
"grep": true,
"glob": true,
"list": true,
"lsp": true,
"patch": true,
"skill": true,
"todowrite": true,
"todoread": true,
"webfetch": true
},
"provider": {
"ascii-mistral": {
"npm": "@ai-sdk/mistral",
"name": "ASCII LiteLLM (Mistral native)",
"options": {
"baseURL": "https://llm.ascii.ac.at/mistral/v1",
"apiKey": "{env:ASCII_AGENTIC_CODING_KEY}"
},
"models": {
"devstral-2512": {
"name": "devstral-2512 (via LiteLLM)",
"limit": { "context": 256000, "output": 256000 },
"tool_call": true,
},
"codestral-2508": {
"name": "codestral-2508 (via LiteLLM)",
"limit": { "context": 128000, "output": 128000 },
"tool_call": true,
},
}
},
"ascii-oai-compatible": {
"npm": "@ai-sdk/openai-compatible",
"name": "ASCII LiteLLM",
"options": {
"baseURL": "https://llm.ascii.ac.at/v1",
"apiKey": "{env:ASCII_AGENTIC_CODING_KEY}"
},
"models": {
"devstral-2512": {
"name": "devstral-2512 (via LiteLLM)",
"limit": { "context": 256000, "output": 256000 },
"tool_call": true,
},
"codestral-2508": {
"name": "codestral-2508 (via LiteLLM)",
"limit": { "context": 128000, "output": 128000 },
"tool_call": true,
},
}
}
},
"model": "ascii-oai-compatible/devstral-2512"
}
Is this likely a opencode or litellm issue?
OpenCode version
1.0.207
Steps to reproduce
No response
Screenshot and/or share link
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Operating System
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Terminal
No response
Reacted by Romain Valtier and Vincent Kelleher
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github-actions commentedon Dec 29, 2025
This issue might be related to existing LiteLLM and OpenAI-compatible provider issues. Please check:
These issues all involve LiteLLM proxies or OpenAI-compatible providers and may provide context for troubleshooting.
Feel free to ignore if your specific case with Devstral's message ordering is a distinct issue.
maxious commentedon Jan 6, 2026
I had the same issue with vllm;
mistral_common.exceptions.InvalidMessageStructureException: Unexpected role 'user' after role 'tool'The workaround from #2440 is to ensure your model id has the string "mistral" in it; devstral should probably be added too:
opencode/packages/opencode/src/provider/transform.ts
Line 58 in e5a8681
eleqtrizit commentedon Jan 18, 2026
@MaximilianHess there is a config to ensure alternating roles for litellm for Mistral based models
eleqtrizit commentedon Jan 18, 2026
One more thing, I don't know how you'r running vLLM, but only the nightlies support tool calling for OpenCode due to another bug with streaming tool calls, which is what OpenCode makes.
geoHeil commentedon Jan 19, 2026
Works for me!
LucasScellos commentedon Jan 26, 2026
Hello @MaximilianHess
This issue is resolved in OpenCode v1.1.36 and does not require any changes to your LiteLLM.
The failure was caused by a message ordering mismatch between OpenCode and Mistral-based models leading to invalid sequences after tool calls.
In my case, upgrading OpenCode fixes the problem by relaxing validation after tools calls
montvid commentedon Mar 5, 2026
Using this workaround serving with vllm devstral 2. Mistral Vibe and Openclaw seem to crash without it. That and one needs to modify litellm/litellm_core_utils/prompt_templates/common_utils.py...
vincentkelleher commentedon Mar 23, 2026
Renaming my Devstral2 model from
devstral-medium-2512tomistral-devstral-medium-2512seems to work after reading #6346 (comment) 👍Adding Devstral to the Mistral prefixes could maybe help this issue ?
github-actions commentedon Jul 3, 2026
To stay organized issues are automatically closed after 60 days of no activity. If the issue is still relevant please open a new one.