The problem with deepseek-reasoner in OpenCode #8934

Activity

1. kirinchin156-source

   added

   bugSomething isn't workingSomething isn't working

   on Jan 16, 2026
2. github-actions

   assigned

   rekram1-node

   on Jan 16, 2026
3. github-actions commented on Jan 16, 2026

   

   github-actionsBot

   on Jan 16, 2026 – with GitHub Actions

   Contributor

   More actions

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

   • DeepSeek V3.2 : reasoning_content not cleared from message history on new turns, causing excess token usage and violating API spec #5577: DeepSeek V3.2 reasoning_content not cleared from message history on new turns, causing excess token usage and violating API spec
   • Deepseek v3.2 - Azure Foundry - It works partially, tools and todos not. #6615: Deepseek v3.2 - Azure Foundry - It works partially, tools and todos not
   • reasoning_content not sent when using @ai-sdk/openai-compatible with deepseek-reasoner #6040: reasoning_content not sent when using @ai-sdk/openai-compatible with deepseek-reasoner (closed)

   Feel free to ignore if your specific case is not addressed by these issues.
4. Robinblennert commented on Jan 20, 2026

   

   Robinblennert

   on Jan 20, 2026

   More actions

   Have you fixed it yet?
   I used 128k really quick and couldnt save the work. Crazy NO idea how much of tokens was used but I understand there is a bug.
5. tongsh6 commented on Mar 10, 2026

   

   tongsh6

   on Mar 10, 2026

   More actions

   I can reproduce a very similar issue with a custom subagent using deepseek/deepseek-reasoner in OpenCode.

   Setup

   Custom local subagent:

   ~/.config/opencode/agents/architect.md

   This is not an oh-my-opencode built-in agent. It is a local custom OpenCode subagent.

   Observed error

   When this subagent performs tool-using work, OpenCode fails with:

   Why this seems like an OpenCode compatibility issue

   According to DeepSeek's official docs for thinking mode + tool calls:

   • during the same reasoning/tool-call turn, the client must send the assistant message back with:
     • content
     • reasoning_content
     • tool_calls

   Docs:
   https://api-docs.deepseek.com/guides/thinking_mode#tool-calls

   This suggests OpenCode is likely dropping reasoning_content when replaying assistant/tool history for reasoning models during tool-call continuation.

   Related notes

   • I also found anomalyco/opencode#9397, which looks closely related
   • This does not appear to be caused by the agent prompt itself
   • It seems specific to:
     • reasoning model
     • tool calls
     • assistant history replay

   Helpful distinction

   This may be reproducible specifically with:

   • custom subagent
   • deepseek/deepseek-reasoner
   • tools enabled (bash: true was enough in my case)

   Temporary workaround on my side is to switch this subagent to deepseek/deepseek-chat or a non-DeepSeek reasoning model.

   If useful, I can provide a more minimal repro prompt next.
6. tongsh6 commented on Mar 10, 2026

   

   tongsh6

   on Mar 10, 2026

   More actions

   Follow-up: my previous comment lost the fenced blocks due to shell quoting. Here is the exact missing content.

   Local subagent config

   ---
   description: Read-only architecture review agent
   mode: subagent
   model: deepseek/deepseek-reasoner
   temperature: 0.1
   steps: 16
   tools:
     write: false
     edit: false
     bash: true
   ---

   Exact error text

   Missing reasoning_content field in the assistant message at message index 32.
   For more information, please refer to https://api-docs.deepseek.com/guides/thinking_mode#tool-calls
   

   This happened while the custom subagent was doing tool-using work.
7. tongsh6 commented on Mar 10, 2026

   

   tongsh6

   on Mar 10, 2026

   More actions

   Solution:

   Configure the DeepSeek model with:

   {
     "provider": {
       "deepseek": {
         "npm": "@ai-sdk/openai-compatible",
         "name": "DeepSeek",
         "options": {
           "baseURL": "https://api.deepseek.com/v1",
           "apiKey": "{env:DEEPSEEK_API_KEY}"
         },
         "models": {
           "deepseek-reasoner": {
             "name": "DeepSeek Reasoner",
             "interleaved": {
               "field": "reasoning_content"
             }
           }
         }
       }
     }
   }

   The key part is:

   "interleaved": {
     "field": "reasoning_content"
   }

   After adding this and restarting OpenCode, the issue was resolved.
8. thdxr

   removed

   bugSomething isn't workingSomething isn't working

   on May 3, 2026
9. github-actions commented on Jul 6, 2026

   

   github-actionsBot

   on Jul 6, 2026 – with GitHub Actions

   Contributor

   More actions

   To stay organized issues are automatically closed after 60 days of no activity. If the issue is still relevant please open a new one.
10. github-actions

    closed this as not plannedon Jul 6, 2026