Read the Local Instruction File Only When It Is a Regular File by ptr727 · Pull Request #2428 · ptr727/ProjectTemplate

ptr727 · 2026-10-06T00:55:07Z

Summary

This fixes the finding Copilot flagged on promotion PR #2425 as "previously missed". read_local_instructions checked the local instruction file with lstat and then read it directly. A FIFO or a character device at that path blocked the read forever, which hung both the install and --report.

A new read_regular_file() opens the path once and judges the open descriptor. It opens with O_RDONLY|O_NONBLOCK and checks the descriptor with fstat and S_ISREG, so a FIFO or a device returns None without blocking. The check and the read are one operation, so nothing can swap the path between them.
The descriptor is closed in a finally on every path. An intermediate version leaked one per directory read, because fdopen raised without closing what it was handed.

Refusal messages:

Local path	Message
Not a regular file (a FIFO, a device, a directory)	"is not a regular file"
A dangling link	"is a link that leads to nothing"
A file deleted between the probe and the open	"no longer exists"
Any other open failure	"cannot be read"

The same message appears on Python 3.11, 3.13 and 3.14. An is_file() check would have differed on 3.14, which swallows every OSError.

The FIFO cases run with a bound, so a regression fails the test rather than hanging the suite. The report case installs first and then asserts the refusal.

The same FIFO gap exists, from before this change, at settings.json and the stamp. It's recorded on #2426, with read_regular_file() as the shape to reuse.

Refs #2423

Verification

python3 -m unittest test_install: 123 tests OK on 3.13 and on 3.14. The edge cases also pass on 3.11.
The local strict review ran 3 rounds: 6 findings, then 2, then none.

🤖 Generated with Claude Code

A FIFO or device at the local instruction path passed the lstat check and then blocked the read, hanging both the install and --report. Only a regular file is read now, anything else stops the run with nothing changed, and the stamp reader skips a stamp that is not a regular file for the same reason. Refs #2423 Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

An is_file() check before the read left a window to swap the path and gave a different message on Python 3.14, where is_file() swallows every OSError. read_regular_file() opens once with O_NONBLOCK and checks the descriptor with fstat, so a FIFO or device returns None without blocking on every version. The stamp guard is dropped, since the stamp is read and written unguarded elsewhere, and the FIFO cases run bounded so a regression fails rather than hangs. Refs #2423 Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

os.fdopen raised on a directory without closing the descriptor it was handed, so read_regular_file leaked one per directory read. It now judges and reads the raw descriptor and closes it in a finally, which also lets a directory reach the regular-file check. A file deleted between the lstat and the open is now said to no longer exist, keeping "a link that leads to nothing" for an actual link. Refs #2423 Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

coderabbitai · 2026-10-06T00:55:34Z

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codecov · 2026-10-06T00:56:42Z

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 58.47%. Comparing base (c24dd93) to head (c272731).

Additional details and impacted files

@@           Coverage Diff            @@
##           develop    #2428   +/-   ##
========================================
  Coverage    58.47%   58.47%           
========================================
  Files           16       16           
  Lines         8062     8062           
========================================
  Hits          4714     4714           
  Misses        3348     3348

Flag	Coverage Δ
python-3.13	`58.47% <ø> (ø)`

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Copilot

Copilot review overview

🟡 Changes recommended

Dangling links through non-directory path components need consistent classification before approval.

Review effort: Lite
Findings: 1

Open (1)

Update comment to describe descriptor closure invariant · New

What changed in this PR

Updates the Claude host-safety installer to safely read only regular local instruction files without blocking on FIFOs or devices.

Changes:

Adds descriptor-based, nonblocking reads with guaranteed cleanup.
Adds FIFO, report, and descriptor-leak regression coverage.
Documents regular-file validation and refusal behavior.

File	Reviewed changes
`host-setup/agent-safety/claude/install.py`	Implements safe regular-file reads; requires consistent dangling-link handling and comment cleanup.
`host-setup/agent-safety/claude/test_install.py`	Adds bounded FIFO and descriptor-cleanup tests; updates an outdated test docstring.
`host-setup/agent-safety/claude/README.md`	Documents regular-file validation and refusal behavior.

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Refs #2423 Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

ptr727 · 2026-10-06T01:00:40Z

A recorded local strict-review pass covers head c272731e872cf1e0f873757e7b84f50a4d93b202, the content this pull request carries at that commit against develop, and it recorded 0 findings.

## Summary Promotes `develop` to `main` with four pull requests, each already reviewed and merged into `develop`: - [#2424](#2424) Render the Whole Global CLAUDE.md and Back Up a Hand Edit. - The host-safety installer now owns all of `~/.claude/CLAUDE.md`. It renders a header, the two existing blocks, and a shared host-local file, `agent-fleet/local.md`. - It replaces an earlier render silently. A file edited by hand, or one written before this change, is copied to a timestamped `.bak` first. - `merge-and-release` step 7 now also runs this kit's `--report`, so a release flags a stale host. - [#2427](#2427) Render CLAUDE.md First and Let the Real Write Be the Check, the fix for this PR's Copilot finding. - [#2428](#2428) Read the Local Instruction File Only When It Is a Regular File, the fix for this PR's previously-missed Copilot finding. - [#2429](#2429) Refuse a Local Instruction Path Whose Parent Is a File, the fix for this PR's third-round Copilot finding. On a host's next install, the existing `CLAUDE.md` is backed up and replaced. Anything host-specific moves into the local file. Closes #2423 🤖 Generated with [Claude Code](https://claude.com/claude-code)

ptr727 and others added 3 commits October 5, 2026 17:40

ptr727 added the comments Permits the comment lines the pull request adds or edits, which the prose gate otherwise refuses label Oct 6, 2026

Copilot AI lite review requested due to automatic review settings October 6, 2026 00:55

Copilot started reviewing on behalf of ptr727 October 6, 2026 00:55

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Copilot AI reviewed Oct 6, 2026

View reviewed changes

Comment thread host-setup/agent-safety/claude/install.py Outdated

State the Descriptor Invariant Rather Than the Removed fdopen

c272731

Refs #2423 Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

ptr727 merged commit c23a2a7 into develop Oct 6, 2026
12 checks passed

ptr727 deleted the feature/local-file-regular-only branch October 6, 2026 01:03

ptr727 mentioned this pull request Oct 6, 2026

Promote develop to main: Whole-File Global CLAUDE.md Ownership #2425

Merged

This was referenced Oct 6, 2026

Codify: Let the Real Operation Be the Check, and Close a Defect Class Through One Primitive #2431

Closed

Session Handoff [host-instructions]: Global CLAUDE.md Is Fleet-Owned, Rollout and Reader Hardening Next #2432

Closed

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Read the Local Instruction File Only When It Is a Regular File - #2428

Read the Local Instruction File Only When It Is a Regular File#2428
ptr727 merged 4 commits into
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ptr727 commented Oct 6, 2026

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