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DeepSeek V4: reasoning_content 400 error persists on v1.14.31 — complete fix exists in unmerged PRs #25311
Description
Bug Description
When using DeepSeek V4 Pro or Flash models with thinking mode enabled (default), multi-turn conversations fail with:
The `reasoning_content` in the thinking mode must be passed back to the API.
This happens reliably on v1.14.31 (latest release) in conversations with multiple tool-call turns, regardless of whether the conversation is fresh or resumed from history.
Why the existing fixes are insufficient
The release notes mention:
- v1.14.24: "Fixed DeepSeek assistant messages so reasoning is always included"
- v1.14.29: "DeepSeek OpenAI-compatible setups now keep reasoning_content interleaved by default"
These handle some code paths but not all. The fundamental issue is that reasoning_content must be present on every assistant message in the conversation history — historical messages from DB replay, string-content messages, and messages processed on the second interleaved pass all need it. The current code has gaps.
The fix exists — three separate PRs wrote it
Three contributors have submitted PRs with the complete fix:
- fix(provider): complete DeepSeek reasoning_content round-trip for multi-turn conversations #24250 by @knefenk — Covers all three layers: auto-enable interleaved, dynamic SDK key, and unconditional
reasoning_contentinjection for all assistant messages including DB-replayed ones. Commit:41eb35a - fix: preserve existing reasoning_content on second interleaved pass (#24146 follow-up) #24428 by @claudianus — Fixes second-pass regression where empty reasoningText overwrites preserved providerOptions values. Commit:
86dd22f - fix: generalize reasoning_content injection across AI SDK providers #24895 by @Malkovich-666 — Generalizes the fix across all AI SDK providers with a
providerOptionsKey()helper. Commit:c42e105
All three were closed without merge.
Environment
- OpenCode v1.14.31 (Linux binary)
- Provider:
@ai-sdk/openai-compatiblevia LLM Gateway (pinned to DeepSeek API) - Model:
deepseek-v4-prowithreasoning: trueandinterleaved: { field: "reasoning_content" } - Also reproduced with direct DeepSeek API (bypassing gateway)
Request
Please review and merge one of the existing complete fixes (#24250, #24895) so that DeepSeek V4 with thinking mode works reliably in multi-turn conversations.
Activity
github-actions commentedon May 1, 2026
This issue might be a duplicate of existing issues. Please check:
reasoning_contentin the thinking mode must be passed back to the API. #24920: DeepSeek V4 flash/pro reasoning_content error after conversation interruption (open)There are also many closed issues tracking this same error (e.g. #24261, #24442, #24190, #24803). The maintainers are likely already tracking this bug — please check the above issues and consider adding a
+1or relevant details there rather than opening a new report.chrispository commentedon May 1, 2026
Edit: Ignore the below. My opencode was out of date. Seems to be working fine in the actual up to date version.
I can confirm the first one you linked fixes it: #24250
I had OpenCode pull the main dev branch and asked it apply the linked fix. Then I re-built, and it's working perfectly for me now. You'll just have to build it, took less than 20 seconds for me.
https://github.com/chrispository/opencode_deepseek_fix
tom-knight-ai commentedon May 4, 2026
Comment from optinosis team: Cerebras GLM-4.7 also affected
We hit this exact bug with the Cerebras Z.AI GLM-4.7 model on OpenCode v1.14.33. Our internal issue: https://github.com/optinosis/optinosis/issues/2229
We confirmed that:
Our temporary workaround is to disable reasoning (), but that significantly degrades model quality for complex tasks (~20-30% drop for architecture/design, ~5% for simple tasks).
We believe a merge of any one of the three PRs — particularly #24250 which is the most comprehensive (3-layer fix covering auto-enable interleaved, dynamic SDK key, and unconditional reasoning injection for all assistant messages) — would resolve this for Cerebras GLM-4.7 and all other affected providers.
Could you review one of these? Happy to provide additional testing or reproductions.
tom-knight-ai commentedon May 4, 2026
Comment from optinosis team: Cerebras GLM-4.7 also affected
We hit this exact bug with the Cerebras Z.AI GLM-4.7 model on OpenCode v1.14.33. Our internal issue: https://github.com/optinosis/optinosis/issues/2229
We confirmed that:
reasoning_contentbut doesn't accept it as input - not just DeepSeekimplementsReasoning: false(an undocumented field) does nothing - it's a silent no-op.opencode/opencode.jsonOur temporary workaround is to disable reasoning (
reasoning_effort: none), but that significantly degrades model quality for complex tasks (~20-30% drop for architecture/design, ~5% for simple tasks).We believe a merge of any one of the three PRs - particularly #24250 which is the most comprehensive (3-layer fix covering auto-enable interleaved, dynamic SDK key, and unconditional reasoning injection for all assistant messages) - would resolve this for Cerebras GLM-4.7 and all other affected providers.
Could you review one of these? Happy to provide additional testing or reproductions.
github-actions commentedon Jul 5, 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.