[BUG] Idle VSCode sessions leave native-binary/claude child spinning at 100% CPU for days

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?

Six separate claude CLI processes (the extension's resources/native-binary/claude,
launched with --output-format stream-json --input-format stream-json ... --debug
--debug-to-stderr) were each pinned at ~100% CPU — one full core apiece — with no
active user interaction. They had been in this state for a long time: elapsed run
time ranged from ~22 hours up to 8 days.

Crucially, these were NOT orphaned. The parent VSCode extension-host (Plugin Helper)
processes were all still alive, and the sessions were idle. So a live, idle session
left its CLI child in a persistent busy-loop. All six were extension build 2.1.165;
sessions from newer builds on the same machine were unaffected.

They responded to SIGTERM cleanly (no SIGKILL needed), so the process was reachable
but was not idling or exiting on its own.

What Should Happen?

An idle session should sit near 0% CPU. It should never spin a CPU core indefinitely.

Error Messages/Logs

No crash/error output available. These sessions ran with --debug over a repository
containing sensitive data, so stderr may include private content and was not captured.
Process-level evidence (sanitized), sorted by elapsed time:

PID    %CPU  ELAPSED      notes
90346  99.4  8-02:17:09   idle session, parent alive, build 2.1.165
5059  100.0  4-02:40:17   "
88082  98.3  2-02:09:23   "
88004  98.1  2-02:09:32   "
93524  99.9  2-00:54:55   "
5249   99.5  1-22:16:32   "

Steps to Reproduce

Not deterministically reproducible. Observed pattern:

1. Open multiple VSCode windows, each with a Claude Code session (extension 2.1.165).
2. Leave the sessions open and idle for an extended period (hours to days).
3. Some sessions enter a persistent ~100% CPU busy-loop that never subsides, even

though the window/extension host is still alive and the session is idle.

1. ps -Ao pid,pcpu,etime,command | grep native-binary/claude shows the affected

processes pinned at ~100% CPU with large elapsed times.

Appears specific to, or far more frequent in, build 2.1.165. Happy to capture a
sample <pid> / spindump <pid> of a repro from a non-sensitive session if that
would help locate the hot loop.

Claude Model

Not sure / Multiple models

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

2.1.165

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

VS Code integrated terminal

Additional Information

Note on "latest version": the affected sessions were long-lived build 2.1.165, kept
alive by VSCode's extension host from when those windows were first opened. The latest
build installed on this machine is 2.1.204, and sessions from newer builds were not
affected — so this may already be fixed, but the severity (a single idle session
spinning a full core for up to 8 days) seemed worth reporting regardless.

I did not attach debug logs or transcripts because those sessions ran with --debug
over a repository containing sensitive data. I can provide a sanitized CPU sample /
spindump from a fresh, non-sensitive repro on request.