hermes - 💡(How to fix) Fix Third-party relay (PackyAPI) + DeepSeek: thinking blocks stripped causing HTTP 400

Description

When using DeepSeek models (e.g. deepseek-v4-flash) through a third-party relay/proxy service (PackyAPI, https://www.packyapi.com) with thinking mode enabled, multi-turn tool calls fail with HTTP 400.

Error Log

⚠️  API call failed (attempt 1/3): BadRequestError [HTTP 400]
   🔌 Provider: custom  Model: deepseek-v4-flash
   🌐 Endpoint: https://www.packyapi.com
   📝 Error: HTTP 400: The `content[].thinking` in the thinking mode must be passed back to the API.
   📋 Details: {'error': {'type': 'invalid_request_error', 'message': 'The `content[].thinking` in the thinking mode must be passed back to the API.'}, 'type': 'error'}

Steps to Reproduce

1. Configure a custom provider pointing to https://www.packyapi.com with model deepseek-v4-flash and thinking mode enabled
2. Start a conversation that triggers tool calls (e.g. web_search)
3. On the second API call (after tool results come back), the error occurs

Expected Behavior

Tool calls should succeed across multiple turns without HTTP 400 errors.

Actual Behavior

The API returns HTTP 400 with the message The content[].thinking in the thinking mode must be passed back to the API., and Hermes reports a non-retryable error.

Root Cause

Same underlying issue as #17992 — in agent/anthropic_adapter.py:_preserve_unsigned_thinking(), thinking blocks with a truthy signature field are stripped. When these blocks are not preserved in the conversation history, the upstream API (DeepSeek, whether directly or through a relay) rejects the next request.

Environment

• Provider: custom (PackyAPI relay)
• Model: deepseek-v4-flash
• Endpoint: https://www.packyapi.com
• Relay service: PackyCode (中转)

Related

• #17992 (same error with official DeepSeek API)
• #17991 (open PR with proposed fix)