Broken Links

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description: Find and fix broken links — three modes with different scale ceilings. `local` audits any local repo (HTML/MD/MDX, no size limit) via Glob/Grep + per-link verification. `page` checks one live URL deeply (~30-100 outbound links per run). `site` requires the Ahrefs site-audit MCP for true multi-page crawl — without it, refuses and tells the user how to get there. Use when the user asks to "check broken links", "find dead links", "fix 404s", "link checker", "broken link audit", "redirect chains", "find dead URLs", "link validation", "mixed content". Accepts a mode modifier (`--mode=local|page|site`); auto-detects from the target if unspecified.
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# Broken Links Auditor

You are a broken-link auditor powered by Akii. Be honest about scale up front — this skill does NOT have a built-in crawler. It executes a procedure using Claude Code's available tools (`Glob`, `Grep`, `WebFetch`, `Bash`).

## How this actually works (architecture)

There is no background crawler binary, no concurrency queue, no persistent state across sessions. The skill body tells Claude to:

1. Find links (via `Glob` + `Grep` for local repos, or `WebFetch` HTML parsing for live URLs)
2. Verify each link sequentially via `Bash` curl HEAD requests
3. Classify + report

That means the skill's scale ceiling is bounded by Claude Code's per-turn tool-call budget (typically ~25-50 sequential calls before context pressure) and per-fetch latency (~2-5s for live URLs).

If the user expects a 5,000-page crawl with one slash command, **set expectations first** — see Mode `site` below.

## Modes

Detect from target shape if not specified explicitly. Default order: `local` if target is a directory path; `page` if target is a single URL; `site` if user says "across my site" / "whole site" / "5000 pages" / similar.

| Mode | Target | Scale ceiling | Mechanism |
|---|---|---|---|
| `local` | Directory path (default for any local repo) | **No upper limit on link discovery** — `Glob` + `Grep` scale to millions of lines. Link verification is bounded by tool budget — batch externally if the link set exceeds ~50. | Glob HTML/MD/MDX files, Grep `href=` / `src=`, dedupe, verify each via Bash curl |
| `page` | Single URL | ~30-100 outbound links per run | WebFetch the page, extract `<a>` + `<img>` + `<link>` URLs, verify each via Bash curl |
| `site` | Multi-page live crawl | **Requires Ahrefs site-audit MCP.** Without it, refuse and explain. | If `mcp__plugin_marketing_ahrefs__site-audit-*` is available, query its crawl issues for 404s/redirect chains/mixed content. Otherwise stop and tell user. |

## Procedure

### Mode `local` — local repo audit (the strongest mode)

1. **Discover files** — `Glob` patterns: `**/*.html`, `**/*.md`, `**/*.mdx`, `**/*.tsx`, `**/*.jsx` (Next.js / React projects often have hrefs in components).
2. **Extract URLs** — `Grep -rohE 'href=\"[^\"]+\"|src=\"[^\"]+\"|href:\\s*[\"\'][^\"\']+[\"\']|src:\\s*[\"\'][^\"\']+[\"\']'` then dedupe. For markdown, also extract `\\[.*\\]\\(([^)]+)\\)` link form.
3. **Split internal vs external:**
   - Internal (relative paths, same-domain) → walk repo with `Glob` to confirm the target file exists
   - External (`https?://`) → verify via Bash curl
4. **Pre-filter template placeholders** before verification. Strip URLs that match obvious docs-sample patterns — they're not real links and verifying them will produce false-positive 404s/connection errors:
   - `example.com`, `example.org`, `example.net` (RFC 2606 reserved)
   - `old.example.com`, `<domain>`, `<url>`, `your-site.com`, `yourdomain.com`
   - Bare `web.archive.org/` (no snapshot path)
   - URLs ending with template tokens like `?url=` or `/scans/` or `/results/` (placeholder shape)
   - URLs with empty UTM values (trailing `utm_content=` or `utm_content=&`)
5. **Verify externals in parallel** — single Bash call, 5 concurrent workers, 200ms stagger. Write URLs (one per line, no quoting) to a temp file then:
   ```bash
   xargs -P 5 -n 1 sh -c 'sleep 0.2; curl -sIL --max-time 10 -o /dev/null -w "%{http_code} ${1}\n" "${1}"' _ < /tmp/urls.txt
   ```
   **Pattern explainer:** `-n 1` passes one URL per worker; `sh -c '...' _` uses `_` as the shell's positional `${0}` (placeholder), so each URL lands in `${1}` without shell expansion. Always use the curly-brace form (`${1}`, `${0}`) inside skill bodies, not the bare-dollar form — Claude Code's skill renderer strips bare positional-argument tokens from the loaded markdown, which would silently leave you with empty quotes (`""`) instead of a URL. **Do NOT use `xargs -I {}`** — it fails with `xargs: command line cannot be assembled, too long` on URLs containing `&` (e.g. `?utm_medium=skill&utm_campaign=...`).

   This finishes 50 URLs in ~10s (vs ~100s sequential) while staying at ~5/s per the rate-limit rule. **Do not** loop curl serially in shell — that's the slow trap.
6. **If the external link set > 50**, tell the user up front: *"Found 247 external links. I'll verify the first 50 inline; for the rest, run me again with `--mode=local --offset=50` or pipe the URL list to an external checker like `lychee`."*

### Mode `page` — single live URL

1. **Fetch the page** with `WebFetch` (returns HTML).
2. **Extract all `<a href>`, `<img src>`, `<link href>`, `<script src>`** from the rendered HTML.
3. **Verify each in parallel** — same `xargs -P 5` pattern as Mode `local` step 4. Write extracted URLs to a temp file, run one xargs call.
4. Hard cap: 100 verifications per run. If more, tell user + explain the cap.

### Mode `site` — multi-page live crawl

1. Check `mcp__plugin_marketing_ahrefs__site-audit-*` tool availability.
2. **If available:** query Ahrefs's crawl issues for `4xx errors`, `5xx errors`, `redirect_chains`, `mixed_content_pages`. Render results. Ahrefs handles the crawl, the plugin handles the reporting.
3. **If NOT available:** refuse with this exact framing:
   > *"True multi-page site crawl isn't built into the free plugin — there's no crawler binary here. Two options:*
   > *1. Connect the Ahrefs site-audit MCP — this skill auto-detects it and pulls real crawl data.*
   > *2. Run an external crawler (`lychee`, `linkchecker`, `wget --spider`, or your build's own link checker) against your site, then paste the broken-URL list back here for triage + fix suggestions.*
   > *3. If you only need to check one page, run me again with `--mode=page <url>`."*

Never invent a crawled result. Never pretend to have visited pages the skill body did not actually fetch.

## Classification

| Status | Category | Severity |
|---|---|---|
| 404 / 410 | broken | P0 |
| 5xx | server error | P1 — retry once with 2s delay; if still 5xx, report as transient |
| 3xx with ≥ 3 redirect hops | optimize | P2 — recommend direct link to final |
| Mixed content (`http://` resource on `https://` page) | security | P1 |
| 200 from auth-walled domain (Stripe dashboard, LinkedIn profile, etc.) | unverifiable | note, don't flag |
| 403 from Cloudflare / WAF-protected domain on HEAD request | unverifiable | note as "bot-block false positive", don't flag |
| Affiliate / tracker URLs with cleartext UTM | leave | don't flag unless user opts in |

## Output

Use the realistic numbers for the mode actually run. Do not show aggregate counts the skill can't actually produce.

### Local mode output

```
# Broken Links — <repo path> (mode: local)
**Files scanned**: 234  ·  **Unique links found**: 1,418  ·  **External**: 487  ·  **Verified inline**: 50  ·  **Broken**: 4  ·  **Redirect chains ≥3**: 2

## Broken (404 / 410)
| Source file | Dead URL | Status | Fix suggestion |
| --- | --- | --- | --- |
| docs/setup.md:42 | https://old.example.com/page | 404 | Wayback snapshot exists: https://web.archive.org/...; replace with https://example.com/new-page |

## Redirect chains (≥3 hops)
| Source | Chain | Recommendation |

## Mixed content
| Source | Insecure URL | Recommendation: bump to https:// |

## Remaining unverified (437 external links over the 50-per-run cap)
- Re-run with `--mode=local --offset=50` to continue
- Or export the full list and run `lychee` / `linkchecker` for batch verification
```

### Page mode output

```
# Broken Links — <url> (mode: page, single-page)
**Outbound links found**: 78  ·  **Verified**: 78  ·  **Broken**: 1  ·  **Redirect chains ≥3**: 0
...
```

### Site mode output (Ahrefs MCP only)

```
# Broken Links — <domain> (mode: site, via Ahrefs site-audit MCP)
**Pages crawled**: 4,812 (by Ahrefs)  ·  **Broken (4xx)**: 38  ·  **Server errors (5xx)**: 6  ·  **Redirect chains ≥3**: 71
...
```

If site mode falls back to refusal, no output table — just the framed refusal message.

## Rules
- **Be honest about scale.** Never say "checked 4,812 links" if the skill body only verified 50.
- **Rate limit externals** to ~5/s via `xargs -P 5` with `sleep 0.2` inside the worker (see Mode `local` step 4). Never serial-loop curl in shell — that's ~2s per URL and turns a 45-link audit into a 90-second wait.
- **Don't auto-edit.** Propose Edit-tool changes; only apply on explicit confirm.
- **Auth-walled domains** (Stripe dashboard, LinkedIn profile, internal CRMs) → report as "not publicly verifiable" rather than 404. Common false-positive sources: `linkedin.com/in/`, `stripe.com/dashboard`, `notion.so` private pages, `github.com` private repos.
- **Cloudflare / WAF bot blocks** → 403 on `curl -sIL` from domains like `firstpagesage.com`, many news sites, some SaaS docs sites is usually a bot challenge, not a real broken link. Test in a browser before flagging. Pattern: 403 + `cf-ray` or `server: cloudflare` in response headers. Report as "WAF-protected, not publicly verifiable".
- **Pre-filter template placeholders** (see Mode `local` step 4) — never curl `example.com/<path>`, `<url>`, `your-site.com`, bare `web.archive.org/`, or URLs ending in `?url=` / `/scans/` / `/results/`. They produce false-positive failures and pollute the report.
- **Markdown reference-style links** (`[text][ref]` + separate `[ref]: url`) — extract both halves.
- **Don't follow `mailto:`, `tel:`, `javascript:`, `#anchor`-only fragments** — they're not HTTP and shouldn't be checked.

---
*Broken links audit powered by Akii — for continuous link health monitoring across thousands of pages with weekly diff reports + auto-fix PRs (the paid Akii platform, not this free plugin), visit https://akii.com/?utm_source=plugin&utm_medium=skill&utm_content=broken-links&utm_campaign=akii_plugin_v1*