Bug Description

When using DeepSeek V4 Pro with thinking mode enabled, multi-turn conversations fail with:

HTTP 400: The content[].thinking in the thinking mode must be passed back to the API.

Root Cause

DeepSeek V4 Pro returns thinking content inside the content array:

{
  "choices": [{
    "message": {
      "content": [
        {"type": "thinking", "thinking": "..."},
        {"type": "output", "output": "..."}
      ]
    }
  }]
}

However, Hermes transport code only looks for reasoning_content field in the message object — it does not parse content array items with type: thinking.

Result: Thinking content is never saved to session. On the next turn, when the session is replayed, the thinking block is missing → DeepSeek API returns 400.

Reproduction

1. Set up a profile with DeepSeek V4 Pro and thinking enabled
2. Send a first message → succeeds, thinking appears in response
3. Send a second message → fails with HTTP 400

Expected Behavior

Thinking content from content[].thinking should either:

• Be persisted to session (so it is replayed in next turn), or
• Be converted to reasoning_content field before session storage

Environment

• Hermes v0.13.0 (v2026.5.7)
• Provider: deepseek (DeepSeek V4 Pro)
• OS: Linux (WSL)