[BUG] API Error: Stream idle timeout - partial response received

Preflight Checklist

• [x] I have searched existing issues and this hasn't been reported yet
• [x] This is a single bug report (please file separate reports for different bugs)
• [x] I am using the latest version of Claude Code

What's Wrong?

Description

When Claude generates a long response involving multiple large code files written back-to-back,
the stream times out mid-response with:

API Error: Stream idle timeout - partial response received

The partial response is shown but the remainder is lost.

Steps to reproduce

1. Ask Claude to write several large files in one turn (e.g. a full HTML file + Python backend + Modal worker)
2. Response cuts off partway through the last file
3. Error banner appears: "Stream idle timeout - partial response received"

Expected behaviour

Either the full response completes, or the timeout resets on each streamed token
(not on wall-clock silence between API calls).

Environment

• Claude Code CLI (web session)
• Model: claude-sonnet-4-6
• Session type: Agent SDK session with hooks

Suggested fix

Increase or remove the per-stream idle timeout for agentic sessions where tool
calls and long codegen are expected, or chunk very long responses into separate
turns automatically.

What Should Happen?

No error

Error Messages/Logs

API Error: Stream idle timeout - partial response received

Steps to Reproduce

Use claude code web and send message to it, go to other thread, and return.

Claude Model

Sonnet (default)

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

Web

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Other

Additional Information

_No response_