diff --git a/.gitignore b/.gitignore
index 60a5122..3d805f0 100644
--- a/.gitignore
+++ b/.gitignore
@@ -40,3 +40,6 @@ research/
 .env
 .env.*
 .codex/
+
+# Doctor staleness-check cache (per-install, transient)
+.pixelslop-doctor-cache.json
diff --git a/CLAUDE.md b/CLAUDE.md
index b89a2d9..ada5242 100644
--- a/CLAUDE.md
+++ b/CLAUDE.md
@@ -136,6 +136,7 @@ Agents use `pixelslop-tools` (bin/pixelslop-tools.cjs) for all state operations.
 - **`config read-tokens` / `config write-tokens`** read and write the project's normative design tokens — a `## Design Tokens` section in `.pixelslop.md` holding flat `key: value` lines (`color-primary: #b8422e`, `font-body: Inter`, `type-scale: 1.25`, `space-unit: 4px`). The setup agent captures them from the codebase; the fixer reads them so a fix moves *toward* the project's real palette/type/spacing instead of a generic default. `write-tokens` merges (unspecified keys preserved) and only touches the Design Tokens section — `config write` stays the initializer, tokens layer on top like settings do.
 - **`scan trend`** reports the score progression across runs. `scan save-results` now appends each run's /20 total (plus per-pillar scores) to `.pixelslop/scan-history.json`; `scan trend [--target <url>] [--last <n>]` reads it back (`11 -> 13 -> 14 (+3)`). History is best-effort — a corrupt history file self-heals and never blocks the actual save. The orchestrator surfaces the trend in its scan summary.
 - **`personas write` / `personas list`** manage project-specific personas. `write --json '<persona>'` validates (required fields, slug-only id, no built-in collision, no path traversal) and saves to `.pixelslop/personas/<id>.json`; `list` returns the 8 built-ins plus any custom ones. The orchestrator generates 1-2 personas from the project's audience/brand and evaluates them alongside the built-ins, so persona findings fit the real users instead of only the generic profiles.
+- **`doctor`** self-checks the install: reports the version, confirms `pixelslop-tools.cjs` is reachable, and flags when a newer version is published (a throttled npm check, cached 24h in `.pixelslop-doctor-cache.json`, fail-soft offline). The skill runs it at preflight — if it can't run, the install is broken/stale and the skill tells the user to `npx pixelslop@latest update`; if it reports `stale`, the skill surfaces the update once and continues. This is what makes a stale/broken install self-diagnose instead of failing opaquely. Inspired by screenslop's doctor-in-the-skill pattern.
 
 ## Voice & Persona
 
diff --git a/bin/pixelslop-tools.cjs b/bin/pixelslop-tools.cjs
index de42af4..46ee41d 100644
--- a/bin/pixelslop-tools.cjs
+++ b/bin/pixelslop-tools.cjs
@@ -2975,6 +2975,90 @@ function scanTrend(flags) {
         : 'No scan history yet.'));
 }
 
+/** Compare two dotted versions; true if a is strictly older than b. */
+function versionLt(a, b) {
+  const pa = String(a).split('.').map((n) => parseInt(n, 10) || 0);
+  const pb = String(b).split('.').map((n) => parseInt(n, 10) || 0);
+  for (let i = 0; i < 3; i++) {
+    if ((pa[i] || 0) < (pb[i] || 0)) return true;
+    if ((pa[i] || 0) > (pb[i] || 0)) return false;
+  }
+  return false;
+}
+
+/**
+ * Resolve the installed version + root. Works in both layouts: an installed
+ * tree (install-manifest.json next to bin/) and the dev repo (package.json).
+ * @returns {{ version: string|null, installRoot: string, source: string|null }}
+ */
+function resolveToolVersion() {
+  const installRoot = path.dirname(__dirname); // bin/ -> install root (or repo root)
+  const manifestPath = path.join(installRoot, 'install-manifest.json');
+  if (fs.existsSync(manifestPath)) {
+    try {
+      const m = JSON.parse(fs.readFileSync(manifestPath, 'utf-8'));
+      if (m.version) return { version: String(m.version), installRoot, source: 'manifest' };
+    } catch { /* fall through */ }
+  }
+  const pkgPath = path.join(installRoot, 'package.json');
+  if (fs.existsSync(pkgPath)) {
+    try {
+      const p = JSON.parse(fs.readFileSync(pkgPath, 'utf-8'));
+      if (p.name === 'pixelslop' && p.version) return { version: String(p.version), installRoot, source: 'package' };
+    } catch { /* fall through */ }
+  }
+  return { version: null, installRoot, source: null };
+}
+
+/**
+ * The latest published version, throttled to one network call per 24h (cached
+ * in the install root). Fail-soft: returns null if offline or npm is slow, so a
+ * scan is never blocked by a flaky network.
+ */
+function resolveLatestVersion(installRoot, offline) {
+  if (offline) return { latest: null, source: 'offline' };
+  const cachePath = path.join(installRoot, '.pixelslop-doctor-cache.json');
+  try {
+    if (fs.existsSync(cachePath)) {
+      const c = JSON.parse(fs.readFileSync(cachePath, 'utf-8'));
+      if (c.checkedAt && Date.now() - new Date(c.checkedAt).getTime() < 24 * 3600 * 1000) {
+        return { latest: c.latest || null, source: 'cache' };
+      }
+    }
+  } catch { /* ignore cache errors */ }
+  let latest = null;
+  try {
+    latest = execFileSync('npm', ['view', 'pixelslop', 'version'], {
+      encoding: 'utf-8', timeout: 8000, stdio: ['ignore', 'pipe', 'ignore']
+    }).trim();
+  } catch { latest = null; }
+  if (latest) {
+    try { fs.writeFileSync(cachePath, JSON.stringify({ checkedAt: new Date().toISOString(), latest })); } catch { /* best effort */ }
+  }
+  return { latest, source: latest ? 'npm' : 'unreachable' };
+}
+
+/**
+ * Self-check the install: confirm this tool is reachable, report the version,
+ * and (throttled) flag if a newer version is published. The skill runs this at
+ * preflight so a stale or broken install self-diagnoses instead of failing
+ * opaquely. Flags: --offline (skip the network check), --raw.
+ */
+function doctorCheck(flags = {}) {
+  const { version, installRoot, source } = resolveToolVersion();
+  const { latest, source: latestSource } = resolveLatestVersion(installRoot, flags.offline);
+  const stale = !!(version && latest && versionLt(version, latest));
+
+  const status = stale ? 'stale' : 'ok';
+  const message = stale
+    ? `pixelslop ${version} is behind the latest ${latest}. Update with: npx pixelslop@latest update`
+    : `pixelslop ${version || '(unknown version)'} — install reachable and current`;
+
+  output(RAW
+    ? { ok: true, status, version, latest, stale, reachable: true, installRoot, toolPath: __filename, versionSource: source, latestSource }
+    : message);
+}
+
 /**
  * Generate a self-contained HTML report from scan results.
  * Fail-soft: returns { ok: false, error } on any failure.
@@ -3367,6 +3451,9 @@ async function main() {
   }
 
   switch (group) {
+    case 'doctor':
+      return doctorCheck(flags);
+
     case 'plan':
       switch (command) {
         case 'begin': return planBegin(flags);
diff --git a/dist/skill/SKILL.md b/dist/skill/SKILL.md
index 916ee39..2250d1c 100644
--- a/dist/skill/SKILL.md
+++ b/dist/skill/SKILL.md
@@ -326,6 +326,22 @@ If the user confirms starting a dev server, run the detected start command and w
 
 ## Phase 2: Pre-flight Check
 
+### Install self-check (do this first)
+
+Before anything else, confirm the pixelslop install is healthy and current:
+
+```bash
+node bin/pixelslop-tools.cjs doctor --raw
+```
+
+- **If this command fails to run** (command not found, file missing, non-zero exit) the install is broken or incomplete — almost always a stale or partial install. Stop and tell the user: *"Your pixelslop install looks broken or incomplete. Run `npx pixelslop@latest update`, then try again."* Don't attempt the scan.
+- **If it returns `"stale": true`** a newer version is published. Tell the user once: *"A newer pixelslop is available — run `npx pixelslop@latest update` for the latest fixes. Continuing with the installed version."* Then proceed (don't block).
+- **If it returns `"status": "ok"`** proceed silently.
+
+This is what makes a stale or broken install self-diagnose instead of failing opaquely mid-scan. `doctor` only checks the network once per day (cached), so it's cheap to run every time.
+
+### Validate the environment
+
 Run init to validate the environment:
 
 ```bash
diff --git a/tests/doctor.test.js b/tests/doctor.test.js
new file mode 100644
index 0000000..657720b
--- /dev/null
+++ b/tests/doctor.test.js
@@ -0,0 +1,73 @@
+/**
+ * Doctor Self-Check Tests
+ *
+ * `pixelslop-tools doctor` is what the skill runs at preflight so a stale or
+ * broken install self-diagnoses instead of failing opaquely (the RankShaker
+ * "tools.cjs not installed" confusion). It reports the install version, confirms
+ * the tool is reachable, and flags when a newer version is published.
+ *
+ * Stale detection is tested by seeding the throttle cache, so no network is
+ * touched and the test is deterministic.
+ *
+ * Run: node --test tests/doctor.test.js
+ */
+
+import { describe, it, afterEach } from 'node:test';
+import { strict as assert } from 'node:assert';
+import { execFileSync } from 'node:child_process';
+import { readFileSync, writeFileSync, existsSync, rmSync } from 'node:fs';
+import { fileURLToPath } from 'node:url';
+import { dirname, join } from 'node:path';
+
+const ROOT = join(dirname(fileURLToPath(import.meta.url)), '..');
+const TOOLS = join(ROOT, 'bin', 'pixelslop-tools.cjs');
+const CACHE = join(ROOT, '.pixelslop-doctor-cache.json'); // installRoot === repo root when run from here
+const VERSION = JSON.parse(readFileSync(join(ROOT, 'package.json'), 'utf-8')).version;
+
+function doctor(args = []) {
+  const out = execFileSync('node', [TOOLS, 'doctor', ...args], { encoding: 'utf-8' });
+  try { return JSON.parse(out); } catch { return { _raw: out.trim() }; }
+}
+const seedCache = (latest) => writeFileSync(CACHE, JSON.stringify({ checkedAt: new Date().toISOString(), latest }));
+
+describe('pixelslop-tools doctor', () => {
+  afterEach(() => { if (existsSync(CACHE)) rmSync(CACHE); });
+
+  it('reports the install version and reachability (offline, no network)', () => {
+    const r = doctor(['--offline', '--raw']);
+    assert.equal(r.ok, true);
+    assert.equal(r.reachable, true);
+    assert.equal(r.version, VERSION, 'version comes from package.json in repo context');
+    assert.equal(r.stale, false, 'no latest known offline, so not stale');
+    assert.equal(r.latestSource, 'offline');
+    assert.ok(r.toolPath.endsWith('pixelslop-tools.cjs'), 'reports its own path');
+  });
+
+  it('flags stale and prints the update command when a newer version is published', () => {
+    seedCache('99.0.0');
+    const r = doctor(['--raw']);
+    assert.equal(r.stale, true, 'current version is behind the seeded latest');
+    assert.equal(r.latest, '99.0.0');
+    const human = doctor([])._raw;
+    assert.match(human, /behind the latest 99\.0\.0/);
+    assert.match(human, /npx pixelslop@latest update/, 'tells the user exactly how to fix it');
+  });
+
+  it('is not stale when the published version equals the install', () => {
+    seedCache(VERSION);
+    const r = doctor(['--raw']);
+    assert.equal(r.stale, false);
+  });
+
+  it('is not stale when the install is ahead of npm (dev build)', () => {
+    seedCache('0.0.1');
+    const r = doctor(['--raw']);
+    assert.equal(r.stale, false, 'an install ahead of npm is fine, not stale');
+  });
+
+  it('uses the cache, not the network, when the cache is fresh', () => {
+    seedCache('42.0.0');
+    // No --offline, but cache is <24h old, so it must use the cached value, not npm.
+    assert.equal(doctor(['--raw']).latest, '42.0.0');
+  });
+});
diff --git a/tests/skill-discoverability.test.js b/tests/skill-discoverability.test.js
index 1b7664a..701d970 100644
--- a/tests/skill-discoverability.test.js
+++ b/tests/skill-discoverability.test.js
@@ -96,6 +96,15 @@ describe('the asking protocol is harness-neutral (works under Codex too)', () =>
   });
 });
 
+describe('the preflight runs a doctor self-check', () => {
+  it('SKILL.md runs doctor and handles broken/stale installs', () => {
+    assert.ok(/doctor/i.test(SKILL), 'SKILL.md must run the doctor self-check at preflight');
+    assert.ok(/broken or incomplete|broken or stale/i.test(SKILL), 'must handle a broken install');
+    assert.ok(/stale/i.test(SKILL) && /npx pixelslop@latest update/i.test(SKILL),
+      'must tell the user how to update when stale/broken');
+  });
+});
+
 describe('the spawn protocol is harness-neutral with an inline fallback', () => {
   it('has a "Spawning agents" protocol', () => {
     assert.ok(/## Spawning agents/i.test(SKILL),