Repository navigation
Zen and Go backends fail on DeepSeek V4 / MiMo tool calling with "Internal server error" #36354
Closed as not planned
Description
Description
Environment
- OpenCode version: 1.17.18
- OS: Windows 11
Affected providers
opencode(Zen)opencode-go
Affected models
deepseek-v4-flashdeepseek-v4-promimo-v2.5-pro
Error
When using these models in agent mode, OpenCode shows "Internal server error" and retries repeatedly.
Direct API test shows the backend returns:
{"error":{"message":"Error from provider (Console Go): Upstream request failed","type":"invalid_request_error","code":"invalid_request_error"}}
Verification
- Same request without tools parameter → 200 OK
- DeepSeek official API with tools → 200 OK
- Other Zen/Go models with tools → 200 OK
Working models
- Zen: hy3
- Go: minimax-m3, glm-5.2, qwen3.6-plus, qwen3.7-max
Suspected root cause
OpenCode backend does not correctly handle reasoning_content echoing for DeepSeek V4 tool calls (and possibly MiMo), causing 400 errors that the client displays as "Internal server error".
Expected behavior
Either fix backend handling for these models, or update models.json to mark tool_call: false for affected models until fixed.
### Plugins
opencode-sessions, opencode-context-cache, magic-context
### OpenCode version
1.17.18
### Steps to reproduce
_No response_
### Screenshot and/or share link
_No response_
### Operating System
Windows 11
### Terminal
wezterm，WindowsReacted by Francisco Cisneros
Metadata
Metadata
Assignees
Labels
No labels
Activity
github-actions commentedon Jul 11, 2026
This issue might be a duplicate of existing issues. Please check:
reasoning_contentnot passed back for tool call turns, causing 400 errors — same suspected root cause (missingreasoning_contentin tool call history)github-actions commentedon Sep 10, 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.
frangcisneros commentedon Sep 22, 2026
Reproduced the same 500 with mimo-v2.6-flash-free (Zen), specifically when the
Readtool returns a PDF:Steps
opencode/mimo-v2.6-flash-free(OpenCode Zen)Readany PDF (tried a 14-page / 365 KB PDF)AI_APICallError: Internal server error, retries forever (retrying attempt #3...), session unusable until undo/interruptLog (
~/.local/share/opencode/log/opencode.log):(repeats on every retry, both
agent=planandagent=build)Not a metadata issue: models.dev already declares PDF support for this model:
So opencode happily forwards the PDF, and the Zen backend returns 500 on the request — same symptom as #34840 but different failure mode (that one was a client-side "does not support pdf" refusal).
Workarounds that work client-side:
pdftoppm -pngthe pages, thenReadthe PNG — images are accepted fine, only the PDF document part triggers the 500fitz) via bashAffects only PDF attachments; plain text/image pastes on the same model work fine.