Anthropic 400: tool_use ids found without tool_result blocks (messagesToAnthropicFormat) #620

Client or integration

Codex App

Area

Provider adapter

Summary

Anthropic 400: tool_use ids were found without tool_result blocks immediately after

When using an Anthropic (Claude) backend, requests fail with:
messages.4: tool_use ids were found without tool_result blocks immediately after: call_4d252114da304363a52244af

Root cause in messagesToAnthropicFormat (line ~424): when an assistant message's text+thinking content is filtered to empty, if (content.length === 0) break skips the entire toolResult processing block. Tool_use blocks are collected but never paired with tool_result blocks — no synthetic [missing tool_result] is created.

Reproduction

1. ocx start
2. Configure Anthropic backend (claude-opus-4-6-thinking) via google-antigravity
3. Use Codex for a session with multiple tool calls until conversation history is large
4. Observe: messages.4: tool_use ids were found without tool_result blocks

Version

2.7.42

Operating system

Windows 11 24H2

Provider and model

google-antigravity / claude-opus-4-6-thinking

Logs or error output

Provider error 400: Antigravity invalid request: {"type":"error","error":{"type":"invalid_request_error","message":"messages.4: `tool_use` ids were found without `tool_result` blocks immediately after: call_4d252114da304363a52244af. Each `tool_use` block must have a corresponding `tool_result` block in the next message."}}

Screenshots and supporting files

No response

Redacted configuration

Checks

• I searched existing issues and documentation.
• I removed secrets, tokens, account details, request credentials, and personal data.