ctx-link-check

name	ctx-link-check
description	Audit docs for dead links. Use before releases, after restructuring docs, or when running a documentation audit.
allowed-tools	Bash(curl:*), Read, Grep, Glob

Scan Markdown files for broken links. Two passes: internal (file targets) and external (HTTP URLs).

Scope Discovery

Determine which directories to scan:

1. If the user specifies a path, use that
2. Otherwise, glob for common doc directories: docs/, doc/, documentation/, site/
3. If none exist, fall back to scanning all .md files in the project root (excluding node_modules/, .git/, vendor/)

Report which directories are being scanned at the start of output.

When to Use

• Before releases or doc deployments
• After renaming, moving, or deleting doc pages
• After restructuring documentation directories or nav
• When /_ctx-audit runs (audit check #12)
• When a user reports a 404 on the site

When NOT to Use

• When editing a single doc (just eyeball links in that file)
• When offline and only external checks would matter

Execution

Pass 1: Internal Links

Scan every .md file in the discovered scope for Markdown links pointing to other files: [text](target.md), [text](../path/file.md), [text](path/file.md#anchor).

For each link:

1. Resolve the target relative to the source file's directory
2. Strip any #anchor fragment before checking file existence
3. Skip external URLs (http://, https://, mailto:)
4. Skip bare anchors (#section-name): these are intra-page
5. Verify the target file exists on disk

Collect all broken internal links as:

BROKEN: source-file.md:LINE → target.md (file not found)

Pass 2: External Links

Scan every .md file in the discovered scope for http:// and https:// URLs in Markdown link syntax.

For each URL:

1. Send an HTTP HEAD request with a 10-second timeout
2. If HEAD fails or returns 405, retry with GET
3. Record the HTTP status code

Report failures as:

WARN: source-file.md:LINE → https://example.com (HTTP 404)
WARN: source-file.md:LINE → https://example.com (timeout)

Do not treat external failures as errors. Network partitions, rate limiting, and transient outages are common. Report them but do not fail the check.

Exceptions: skip these URLs:

• localhost / 127.0.0.1 URLs (local dev servers)
• example.com / example.org (placeholder domains)

Pass 3: Image References

Scan for image links: ![alt](path/to/image.png) and ![alt](images/file.jpg).

Verify the image file exists on disk. Same resolution rules as internal links.

Output Format

## Link Check Report

### Internal Links
- N broken links found (or "All clear")
- [list of broken links with file:line and target]

### External Links
- N warnings (or "All reachable")
- [list of failures with file:line, URL, and reason]

### Images
- N missing images (or "All present")
- [list of missing images with file:line and target]

### Summary
Internal: N broken / M total
External: N unreachable / M total
Images: N missing / M total

Fixing

For broken internal links, offer specific fixes:

• If the target was renamed, suggest the new path
• If the target was deleted, suggest removing the link or pointing to an alternative
• If the target is a typo (close match exists), suggest the correction

For external links, just report. The user decides whether to update, remove, or ignore.

Integration with /_ctx-audit

When invoked as check #12 from /_ctx-audit:

• Run the full check (all 3 passes)
• Report findings in the same format as other consolidation checks
• Internal broken links count as findings to fix
• External failures count as warnings (informational)

Quality Checklist

After running the check:

• All .md files in the discovered scope were scanned
• Relative path resolution accounts for subdirectories
• Anchors stripped before file existence check
• External check used timeouts (not hanging on slow hosts)
• localhost/example URLs were skipped
• Report distinguishes errors (internal) from warnings (external)