[BUG] CLAUDE_CODE_EXTRA_BODY thinking field is merged into WebSearch/WebFetch requests and breaks them (still on 2.1.290; follow-up to #56984)

What's wrong

CLAUDE_CODE_EXTRA_BODY is merged into the internal requests that WebSearch and WebFetch make, so any thinking field set there breaks both tools. This is the bug in #56984, which the inactivity bot closed as not planned; the bot asked for a new issue if it is still relevant. It still reproduces on 2.1.290 with a Claude 5 model, and the third condition below shows how the field reaches those requests.

The variable is a common workaround for getting thinking summaries where showThinkingSummaries has no effect; anyone relying on that workaround loses web search.

Measured (same machine, same session, relaunched between conditions; the variable read from the running claude process's own environment each time)

| CLAUDE_CODE_EXTRA_BODY | Main model | WebSearch and WebFetch |
|---|---|---|
| {"thinking":{"type":"adaptive","display":"summarized"}} | works | API Error: 400 adaptive thinking is not supported on this model |
| unset | works | work |
| {"thinking":{"display":"summarized"}} | works | API Error: 400 thinking.type: Field required |

The error text follows whatever thinking value the variable holds, so the extra body is being merged into the web tools' secondary requests. Only these two tools failed; other tools in the same sessions worked.

What should happen

Apply CLAUDE_CODE_EXTRA_BODY only to the main conversation requests, or strip fields (like thinking) that the web tools' internal requests cannot accept. Either way, a user should be able to have thinking summaries and web search at the same time.

Steps to reproduce

1. Launch Claude Code with CLAUDE_CODE_EXTRA_BODY='{"thinking":{"type":"adaptive","display":"summarized"}}' in the environment.
2. Ask for any web search, or a fetch of any URL.
3. Both fail with 400 adaptive thinking is not supported on this model.
4. Relaunch with CLAUDE_CODE_EXTRA_BODY='{"thinking":{"display":"summarized"}}' and repeat: both fail with 400 thinking.type: Field required.
5. Relaunch without the variable: both work.

Environment

• Claude Code 2.1.290
• Model: claude-opus-5-5
• Platform: Linux (WSL2)
• Also reported through /feedback (receipts 15276811-0c0e-4438-ab5e-a41c7004a8a6, 43e197dd-5779-4255-b226-f286620e052c)

Related

• #56984 (same bug, closed by the inactivity bot)
• #95497 and #89633 (same adaptive thinking is not supported error from WebFetch/WebSearch; they don't say whether this variable was set, so they may or may not share this cause)