DeepSeek V4 Flash: reasoning_content must be passed back to API when using thinking mode #24130

"interleaved": {
  "field": "reasoning_content"
}
Issue
1. New model names (deepseek-v4-flash, deepseek-v4-pro) are not pre-configured with interleaved in the default provider settings
2. Users must manually add this configuration for proper functioning
3. Compared to legacy model deepseek-reasoner, V4's default behavior may differ (per official docs: deepseek-chat temporarily points to deepseek-v4-flash non-thinking mode, but this may change over time)
Suggested Fix
1. Update default provider configuration: Pre-configure interleaved for deepseek-v4-pro and deepseek-v4-flash models
2. Or auto-detect: Automatically handle reasoning_content when DeepSeek models with thinking mode are detected
Workaround
Users can manually configure in opencode.json:
{
  "provider": {
    "deepseek": {
      "npm": "@ai-sdk/openai-compatible",
      "name": "DeepSeek",
      "options": {
        "baseURL": "https://api.deepseek.com/v1",
        "apiKey": "{env:DEEPSEEK_API_KEY}"
      },
      "models": {
        "deepseek-v4-flash": {
          "name": "DeepSeek V4 Flash",
          "interleaved": {
            "field": "reasoning_content"
          }
        },
        "deepseek-v4-pro": {
          "name": "DeepSeek V4 Pro",
          "interleaved": {
            "field": "reasoning_content"
          }
        }
      }
    }
  }
}
Notes on interleaved Configuration
Based on prior issues (#6040, #8934), configuring "interleaved": { "field": "reasoning_content" } for DeepSeek models using the official API (@ai-sdk/openai-compatible) has minimal side effects:
- Slightly increased token usage (DeepSeek API ignores reasoning_content from prior turns per #5577, but still bills for them)
- Slightly increased network bandwidth
This is the recommended configuration per DeepSeek's API documentation.
Related Issues
This issue type has been reported multiple times, but is new for V4 models:
- #4947, #5027, #5332, #5577, #6040, #8934, #10788, #17523
OpenCode Version
1.14.22
Operating System
ubuntu 22.04

### Plugins

rtk

### OpenCode version

1.14.22

### Steps to reproduce

_No response_

### Screenshot and/or share link

_No response_

### Operating System

Ubuntu 22.04

### Terminal

_No response_