VSCode extension: session freezes completely (no signal, no interrupt) on a simple file-write instruction

Date observed: 2026-09-13

Environment

• Client: Claude Code — VSCode native extension
• Machine: MacBook Pro, macOS 26.6.2 (build 25G83) — captured from a fresh session on presumably the same machine right after the incident; not confirmed identical to the exact state at the time
• Claude Code version: 2.1.239 — same caveat

Steps to reproduce

1. In an active session, after Claude had shown some results in the chat, I gave the instruction (in Italian): "copia i risultati che mi hai mostrato nella chat in un file MD dentro la cartella TO DO" (≈ "copy the results you just showed me in the chat into a markdown file inside the TO DO folder").
2. The session appeared to hang immediately.
3. It never recovered and I eventually force-closed it.

Expected behavior

Either the instruction completes (file written, confirmation shown), or — if something goes wrong (pending permission prompt, tool-call error, runaway loop) — the UI shows some visible signal (spinner, pending-approval prompt, error message) and stays responsive to an interrupt.

Actual behavior

• Complete freeze: no activity indicator, no streaming text, no tool-call indicator, no output, no error message.
• No interrupt worked from within the chat UI — no way to cancel/stop.
• No file was created: the target TO DO/ folder has no new file for this request.
• The session never recovered on its own and had to be force-closed. No diagnostic could be retrieved afterward.

Severity / impact

High from my perspective: a simple, everyday instruction ("save what you just showed me to a file") produced a silent, total hang with no recovery path short of force-closing the application, and no visible way to tell "still working" apart from "crashed." This could just as easily happen mid-task with real unsaved work in progress.

Known unknowns

• Whether the underlying cause was a repeated/looping tool call (e.g. Write/Edit called in a cycle), a permission-approval dialog that failed to render, or something else.
• Whether this is reproducible on demand or was a one-off.

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Filed on the user's behalf by Claude Code (Sonnet 5), from a separate session, after the frozen session was closed and no longer available for diagnostics.