[MODEL] Generic staging installer overwrites an existing installer without preflight

Status Open

Maintainer reply None cached

Activity 0 comments · opened Oct 10, 2026

Preflight Checklist

[x] Existing open and closed issues were searched for duplicates.
[x] This payload excludes credentials and private identifying details.

Type of Behavior Issue

Other unexpected behavior.

What You Asked Claude to Do

I work on AI adoption and systems design. This is a historical product failure report assembled from my local incident log; an independent controlled replay was not run. The task: stage an installer script into an existing staging folder. The private task prompt is not reproduced.

What Claude Actually Did

Claude wrote a generically named install.sh into the staging folder without listing the folder first. An existing installer with the same name was replaced. The Write tool result said the file was updated, not created, and the overwrite was not flagged. The prior content was later restored from the transcript, but its earlier modification time was lost.

Expected Behavior

Inspect the target folder before writing, pick a unique versioned filename, and preserve the existing installer before any approved replacement. When a write replaces an existing file, say so clearly.

Files Affected

Local artifacts are represented as <workspace>/<artifact>. Exact private filenames and paths are omitted.

Permission Mode

Not recorded in the incident log.

Can You Reproduce This?

Haven't tried to reproduce in an independent clean session. The local log records the historical occurrence.

Steps to Reproduce

Ask Claude Code to stage an installer into a folder that already contains a file with the same generic name, install.sh.
Let it write the file.
Check whether it listed the folder first, and whether the result reported a replacement.

These are historical conditions and a proposed verification procedure, not a claim of deterministic reproduction.

Claude Model

Opus 5.5, as recorded in the incident log.

Relevant Conversation

The sequence is described above with private context removed. No assistant self explanation is treated as proof of an internal mechanism.

Impact

Medium - Extra work to undo changes

OBSERVED raw window: 4,044,231 token units. ESTIMATED share: about 2.7M, calculated from 6 of 9 messages in the window (assuming equal message cost gives 2,696,154). ESTIMATED rework: about 3 minutes. Not all raw tokens are proven avoidable.

Claude Code Version

Not recorded in the incident log. This is a historical record, not a test of the latest release.

Platform