[OpenCode Go] deepseek-v4-pro via Responses API: 400 tools[N].function missing field 'name' (web_search tool rejected)

Summary

deepseek-v4-pro via OpenCode Go (https://opencode.ai/zen/go/v1, Responses API) returns HTTP 400 from Codex:

Error from provider (Console Go): Upstream request failed: [invalid_request_error] Failed to deserialize the JSON body into the target type: tools[8].function: missing field `name`

The same setup works with deepseek-v4-flash, and works with deepseek-v4-pro when using the DeepSeek official API directly.

Environment

• Client: OpenAI Codex CLI 0.147.0 (wire_api = responses)
• Provider base URL: https://opencode.ai/zen/go/v1
• Model: deepseek-v4-pro
• Reasoning effort: high / max

Root cause (confirmed by capturing the actual request)

I captured the exact request body sent by Codex through a local proxy. tools[8] is:

{"type": "web_search", "external_web_access": {...}}

Per the OpenAI Responses API spec, a web_search tool is a non-function tool and has no name field. The Console Go upstream appears to parse every tool as a function tool and requires function.name, hence:

tools[8].function: missing field `name`

This is the same root cause described in PR #40210 ("toOaCompatibleRequest mapped every tool into {"type":"function","function":{...}}, producing an undefined name that upstream serde rejects ... 400ing the whole request"). It seems that fix is not yet effective on the /v1/responses path for deepseek-v4-pro (tested 2026-08-13, still 400).

Expected behavior

Non-function tools such as web_search should either be accepted as-is (with no function.name requirement) or filtered out when converting to the upstream chat-completions format, while function tools keep their nested function.name (as PR #40210 states).

Repro

1. Configure Codex with model = "deepseek-v4-pro", base_url = "https://opencode.ai/zen/go/v1", wire_api = "responses".
2. Run any tool-enabled request (e.g. codex exec "Reply OK").
3. Observe the 400 above. Flash model on the same config succeeds.

Related

• #24224, #24344, #27047, #34331
• PR #40210