diff --git a/gitnexus-factory-plugin/hooks/gitnexus-hook.js b/gitnexus-factory-plugin/hooks/gitnexus-hook.js
index 05aa4368e..248680e86 100644
--- a/gitnexus-factory-plugin/hooks/gitnexus-hook.js
+++ b/gitnexus-factory-plugin/hooks/gitnexus-hook.js
@@ -2,15 +2,29 @@
 /**
  * GitNexus Factory AI (Droid) Plugin Hook
  *
- * PostToolUse handler — augments Grep/Glob/Execute searches with graph
- * context from the GitNexus index. Self-contained: reads the tool payload from
- * stdin, resolves a search pattern, and appends `gitnexus augment` output via
- * hookSpecificOutput.additionalContext. No external dependencies (no jq).
+ * PostToolUse — augments Grep/Glob/Execute searches with graph context from
+ * the GitNexus index and returns it via hookSpecificOutput.additionalContext.
+ *
+ * Reuses the same guards as the Claude/Codex adapter (bundled byte-identical,
+ * kept in lockstep by test/unit/factory-plugin.test.ts):
+ *   - acquireHookSlot  — per-repo cap on concurrent augment children so
+ *     parallel sessions can't fan out unbounded `gitnexus augment` spawns
+ *     (#1486).
+ *   - LadybugDB owner probe — skips the CLI augment when a GitNexus MCP/serve
+ *     process already holds the single-writer DB lock, avoiding contention
+ *     (#2396); the in-session MCP tools cover augmentation instead.
+ *
+ * The augment CLI child is NOT wrapped in the coreutils `timeout`
+ * orphan-containment guard the full Claude adapter uses (#2163) — same scope
+ * as the Cursor integration. Add it (resolveUnixGuardTimeout is exported by
+ * the bundled probe) if orphaned augment children become a problem here.
  */
 
 const fs = require('fs');
 const path = require('path');
 const { spawnSync } = require('child_process');
+const { acquireHookSlot } = require('./hook-lock.js');
+const { hasGitNexusDbLockedByGitNexusServer } = require('./hook-db-lock-probe.cjs');
 
 /**
  * Read JSON input from stdin synchronously.
@@ -25,23 +39,42 @@ function readInput() {
 }
 
 /**
- * Check if a directory (or ancestor) has a .gitnexus index.
+ * A `.gitnexus/` that holds `registry.json`/`repos` (and no per-repo index
+ * metadata) is the global registry, not a repo index — never augment against
+ * it. Mirrors the Claude adapter's guard.
  */
-function findGitNexusIndex(startDir) {
+function isGlobalRegistryDir(candidate) {
+  if (
+    fs.existsSync(path.join(candidate, 'gitnexus.json')) ||
+    fs.existsSync(path.join(candidate, 'meta.json'))
+  ) {
+    return false;
+  }
+  return (
+    fs.existsSync(path.join(candidate, 'registry.json')) ||
+    fs.existsSync(path.join(candidate, 'repos'))
+  );
+}
+
+/**
+ * Walk up from startDir looking for a non-registry `.gitnexus/` folder. Returns
+ * the path to `.gitnexus/` or null if not found within 5 levels.
+ */
+function findGitNexusDir(startDir) {
   let dir = startDir || process.cwd();
   for (let i = 0; i < 5; i++) {
-    if (fs.existsSync(path.join(dir, '.gitnexus'))) {
-      return true;
-    }
+    const candidate = path.join(dir, '.gitnexus');
+    if (fs.existsSync(candidate) && !isGlobalRegistryDir(candidate)) return candidate;
     const parent = path.dirname(dir);
     if (parent === dir) break;
     dir = parent;
   }
-  return false;
+  return null;
 }
 
 /**
- * Extract search pattern from tool input.
+ * Extract a search pattern from a Factory tool payload. Factory's shell tool is
+ * `Execute` (Claude's is `Bash`); Grep/Glob match Claude's.
  */
 function extractPattern(toolName, toolInput) {
   if (toolName === 'Grep') {
@@ -98,62 +131,87 @@ function extractPattern(toolName, toolInput) {
   return null;
 }
 
+/**
+ * Run `gitnexus augment` for `pattern` and return its stderr (the augment CLI
+ * writes results to stderr; LadybugDB's native module captures stdout at the OS
+ * fd level, making it unusable in subprocess contexts). Tries a PATH-installed
+ * binary first, then falls back to npx.
+ *
+ * SECURITY: `pattern` is passed after the `--` end-of-options marker and never
+ * through a shell — the Windows npx fallback invokes `npx.cmd` directly rather
+ * than `shell: true`, so a pattern like `-rf` or `$(...)` is inert.
+ */
+function runAugment(pattern, cwd) {
+  const isWin = process.platform === 'win32';
+  const spawnOpts = {
+    encoding: 'utf-8',
+    timeout: 8000,
+    cwd,
+    stdio: ['pipe', 'pipe', 'pipe'],
+    windowsHide: true,
+  };
+
+  try {
+    const child = spawnSync(
+      isWin ? 'gitnexus.cmd' : 'gitnexus',
+      ['augment', '--', pattern],
+      spawnOpts,
+    );
+    if (!child.error && child.status === 0 && child.stderr && child.stderr.trim()) {
+      return child.stderr;
+    }
+  } catch {
+    /* not on PATH — fall through to npx */
+  }
+
+  try {
+    const child = spawnSync(
+      isWin ? 'npx.cmd' : 'npx',
+      ['-y', 'gitnexus', 'augment', '--', pattern],
+      spawnOpts,
+    );
+    if (!child.error && child.status === 0 && child.stderr && child.stderr.trim()) {
+      return child.stderr;
+    }
+  } catch {
+    /* graceful failure */
+  }
+
+  return '';
+}
+
 function main() {
   try {
     const input = readInput();
-    const hookEvent = input.hook_event_name || '';
-
-    if (hookEvent !== 'PostToolUse') return;
+    if ((input.hook_event_name || '') !== 'PostToolUse') return;
 
     const cwd = input.cwd || process.cwd();
-    if (!findGitNexusIndex(cwd)) return;
+    if (!path.isAbsolute(cwd)) return;
+    const gitNexusDir = findGitNexusDir(cwd);
+    if (!gitNexusDir) return;
 
     const toolName = input.tool_name || '';
-    const toolInput = input.tool_input || {};
-
     if (toolName !== 'Grep' && toolName !== 'Glob' && toolName !== 'Execute') return;
 
-    const pattern = extractPattern(toolName, toolInput);
+    const pattern = extractPattern(toolName, input.tool_input || {});
     if (!pattern || pattern.length < 3) return;
 
-    // augment CLI writes result to stderr (KuzuDB's native module captures
-    // stdout fd at OS level, making it unusable in subprocess contexts).
+    const release = acquireHookSlot(gitNexusDir);
+    if (!release) return; // all per-repo augment slots held by concurrent sessions
+
     let result = '';
-
-    const isWin = process.platform === 'win32';
-
-    // Try direct gitnexus binary first (faster if globally installed)
     try {
-      const child = spawnSync('gitnexus', ['augment', pattern], {
-        encoding: 'utf-8',
-        timeout: 8000,
-        cwd,
-        stdio: ['pipe', 'pipe', 'pipe'],
-        shell: isWin,
-      });
-      if (child.status === 0 && child.stderr && child.stderr.trim()) {
-        result = child.stderr;
+      if (hasGitNexusDbLockedByGitNexusServer(path.join(gitNexusDir, 'lbug'), process.pid)) {
+        // #2396: a GitNexus MCP/serve process owns the single-writer DB, so a
+        // competing CLI augment would only contend on the lock. The session's
+        // MCP tools cover augmentation instead — skip silently.
+        return;
       }
+      result = runAugment(pattern, cwd);
     } catch {
-      /* not on PATH */
-    }
-
-    // Fallback to npx if direct binary didn't produce output
-    if (!result || !result.trim()) {
-      try {
-        const child = spawnSync('npx', ['-y', 'gitnexus', 'augment', pattern], {
-          encoding: 'utf-8',
-          timeout: 8000,
-          cwd,
-          stdio: ['pipe', 'pipe', 'pipe'],
-          shell: isWin,
-        });
-        if (child.status === 0 && child.stderr && child.stderr.trim()) {
-          result = child.stderr;
-        }
-      } catch {
-        /* graceful failure */
-      }
+      /* graceful failure */
+    } finally {
+      release();
     }
 
     if (result && result.trim()) {
@@ -167,7 +225,7 @@ function main() {
       );
     }
   } catch {
-    // Graceful failure
+    /* never let the hook break the tool call */
   }
 }
 
diff --git a/gitnexus-factory-plugin/hooks/hook-db-lock-probe.cjs b/gitnexus-factory-plugin/hooks/hook-db-lock-probe.cjs
new file mode 100644
index 000000000..4376795e2
--- /dev/null
+++ b/gitnexus-factory-plugin/hooks/hook-db-lock-probe.cjs
@@ -0,0 +1,728 @@
+/**
+ * Cross-platform best-effort probe: does another process hold dbPath open
+ * with a command line that looks like a GitNexus MCP/serve server?
+ *
+ * Backends (no user-installed Sysinternals):
+ * - Linux: cmdline-first procfs scan under /proc, no lsof at all (#2180). Three
+ *   phases, cheapest first: (0) read /proc/<pid>/comm — a tiny task->comm read
+ *   that never touches the target's mm — and keep only PIDs whose comm is a
+ *   plausible node/gitnexus server; (1) read up to GITNEXUS_HOOK_PROC_CMDLINE_MAX
+ *   bytes of /proc/<pid>/cmdline via openSync+readSync (bounded, so a D-state
+ *   holder stuck on mmap_lock or a giant argv can't wedge the hook) and prefilter
+ *   with isGitNexusServerCommand; (2) only for the 0..N survivors, stat their
+ *   /proc/<pid>/fd/* and compare dev+inode against the target lbug. The lbug
+ *   handle is fd-visible (a @ladybugdb/core property), so this finds every real
+ *   owner without scanning every fd of every process.
+ * - macOS / *BSD / etc.: trusted lsof + ps (absolute paths first).
+ * - Windows: Restart Manager (rstrtmgr) via bundled PowerShell script +
+ *   Win32_Process for command lines; trusted powershell.exe under %SystemRoot%.
+ *
+ * Fail matrix:
+ * - Linux proc scan: owner found -> fail-closed (skip augment); budget exhausted
+ *   (GITNEXUS_HOOK_LINUX_PROC_BUDGET_MS) -> fail-CLOSED (#2180). This is a
+ *   deliberate change from the old "timeout -> fail-open then try lsof" path.
+ *   End-to-end the busy-host outcome is unchanged: the old code's lsof fallback
+ *   ETIMEDOUT'd on the very hosts where the scan ran out of budget and ALSO
+ *   failed closed there — the lsof leg only ever added 1-2s of dead work plus
+ *   the orphan-storm risk it caused (#2163). What changes is that an overloaded
+ *   host now self-throttles immediately (the throttle the incident needed)
+ *   instead of paying for a doomed lsof. Mid-load hosts that used to fall
+ *   through to a successful lsof now answer from the scan directly (faster) or,
+ *   if even the scan can't finish in budget, fail closed (self-throttle) — a
+ *   bounded, documented tradeoff, never an orphan.
+ * - macOS / other Unix: fail-open on most errors; fail-closed only on lsof
+ *   ETIMEDOUT, matching the hook contract.
+ * - Windows: fail-closed only on PowerShell ETIMEDOUT.
+ *
+ * Unix subprocess containment contract (#2163):
+ * - lsof/ps are wrapped in coreutils `timeout`/`gtimeout` when a working
+ *   wrapper is found (`timeout -k 1 <budget> lsof ...`). If this hook process
+ *   is itself SIGKILLed (e.g. by the runner's 10s hook timeout) the wrapper
+ *   survives, SIGTERMs its child at the budget (2s lsof / 1s ps) and SIGKILLs
+ *   it 1s later — orphan lifetime is bounded at ~3s instead of unbounded.
+ * - GITNEXUS_HOOK_TIMEOUT_PATH: the sentinel value `disabled` switches the
+ *   wrapper off deterministically; any other value is adopted only when it
+ *   exists AND passes a one-shot `-k` exit-propagation self-test — otherwise
+ *   resolution FALLS THROUGH to the built-in candidate list (first self-test
+ *   pass wins), so no malformed value of any shape can silently disable
+ *   orphan containment.
+ * - The gitnexus server is lazy-open + sticky-hold: an idle MCP server holds
+ *   ZERO lbug fds until the repo's first MCP query, then keeps the fd open.
+ *   A probe before that first query is therefore always false — a known,
+ *   pre-existing race, not a bug in this probe.
+ * - resolveUnixGuardTimeout is exported so the hook adapters can wrap the
+ *   `gitnexus augment` CLI child — the longest-lived hook subprocess (7s
+ *   local / 12s npx inner budgets) — in the same guard; see runGitNexusCli
+ *   in the adapters (#2163 follow-up).
+ */
+
+const fs = require('fs');
+const path = require('path');
+const { spawnSync } = require('child_process');
+
+function isGitNexusServerCommand(command) {
+  const hasServerMode = /(?:^|\s)(mcp|serve)(?:\s|$)/.test(command);
+  const hasGitNexus =
+    /(?:^|[/\\\s])gitnexus(?:\.cmd)?(?:\s|$)/.test(command) ||
+    /node_modules[/\\]gitnexus[/\\]/.test(command);
+  return hasServerMode && hasGitNexus;
+}
+
+// GITNEXUS_DEBUG-gated stderr diagnostics. Reuses the exact gating predicate the
+// Windows ps1-load warning already uses (===' 1' / ==='true') so there is one
+// debug convention in this file, and writes via process.stderr.write (NOT a
+// spawn) so it never perturbs the windowsHide spawn-count invariant.
+function debugLog(msg) {
+  if (process.env.GITNEXUS_DEBUG === '1' || process.env.GITNEXUS_DEBUG === 'true') {
+    process.stderr.write(`[GitNexus hook] ${msg}\n`);
+  }
+}
+
+function resolveHookBinary(tool) {
+  const envKey = tool === 'lsof' ? 'GITNEXUS_HOOK_LSOF_PATH' : 'GITNEXUS_HOOK_PS_PATH';
+  const fromEnv = process.env[envKey];
+  if (fromEnv && String(fromEnv).trim() && fs.existsSync(String(fromEnv))) {
+    return String(fromEnv);
+  }
+  const candidates =
+    tool === 'lsof'
+      ? ['/usr/bin/lsof', '/usr/sbin/lsof', '/sbin/lsof', tool]
+      : ['/bin/ps', '/usr/bin/ps', tool];
+  for (const candidate of candidates) {
+    if (candidate === tool) return tool;
+    try {
+      if (fs.existsSync(candidate)) return candidate;
+    } catch {
+      /* ignore */
+    }
+  }
+  return tool;
+}
+
+function hasMissingHookBinaryOverride(tool) {
+  const envKey = tool === 'lsof' ? 'GITNEXUS_HOOK_LSOF_PATH' : 'GITNEXUS_HOOK_PS_PATH';
+  const fromEnv = process.env[envKey];
+  if (!fromEnv || !String(fromEnv).trim()) return false;
+  try {
+    return !fs.existsSync(String(fromEnv).trim());
+  } catch {
+    return true;
+  }
+}
+
+// Sentinel:
+//   undefined = not resolved yet (resolve lazily, on first lsof/ps fallback)
+//   string    = self-tested coreutils timeout/gtimeout path (use as wrapper)
+//   null      = no usable wrapper (disabled, none found, or self-test failed)
+let unixGuardTimeoutCache;
+
+/**
+ * Resolve a coreutils `timeout`/`gtimeout` binary to wrap lsof/ps with
+ * (#2163). Unix-only by contract: the probe's win32 dispatch returns before
+ * reaching it, and the exported callers (the adapters' runGitNexusCli,
+ * #2163 follow-up) must check the platform first — the self-test below
+ * spawns /bin/sh. The memoized result is module-wide, so probe and adapter
+ * share one lazy self-test per hook process.
+ *
+ * GITNEXUS_HOOK_TIMEOUT_PATH semantics: the sentinel `disabled` turns the
+ * wrapper off; any other value is only a CANDIDATE — an existing file path
+ * is tried first, but it must pass the `-k` exit-propagation self-test to
+ * be adopted. On any failure (non-existent path, directory, non-executable
+ * file, wrapper without `-k` support, always-exit-0 stub, …) resolution
+ * falls through to the built-in candidates below, tried in order, first
+ * self-test pass wins. This is strictly stronger than the sibling
+ * GITNEXUS_HOOK_LSOF_PATH / GITNEXUS_HOOK_PS_PATH overrides (which only
+ * check existence): no bad env value of ANY shape can silently disable
+ * orphan containment.
+ *
+ * Lazy self-test: candidates are probed only when the lsof/ps fallback is
+ * first reached, and the result is memoized. A candidate is adopted only
+ * when `timeout -k 1 1 /bin/sh -c 'exit 42'` exits 42 — i.e. it must RUN
+ * the wrapped command AND PROPAGATE its exit status. This rejects two
+ * failure shapes: wrappers without the coreutils `-k` flag — busybox <1.34,
+ * toybox, broken symlinks — which would exit with a usage error without
+ * ever running lsof, silently converting the lsof-ETIMEDOUT fail-closed
+ * contract into fail-open (#1492 regression); and always-exit-0 stubs
+ * (/bin/true shapes), which would otherwise be adopted and "succeed" every
+ * wrapped spawn instantly without running it — a constant no-owner probe
+ * answer and, worse, a silently dead augment (status 0, empty stderr passes
+ * the adapters' success check with no context; #2163 follow-up review).
+ * Only when EVERY candidate fails does the probe fall back to the unwrapped
+ * status quo (memoized null). busybox ≥1.34 passes the test and is fully
+ * usable for everything THIS file spawns (lsof/ps are the guard's direct
+ * children) and for the adapters' direct-exec arm. The adapters' npx arm
+ * additionally relies on coreutils' process-GROUP signalling for its
+ * `-s KILL` grandchild reaping; busybox signals only its direct child, and
+ * this self-test deliberately does not probe that capability — see the
+ * adapter docblocks for the residual-gap statement.
+ */
+function passesGuardSelfTest(guard) {
+  try {
+    const selfTest = spawnSync(guard, ['-k', '1', '1', '/bin/sh', '-c', 'exit 42'], {
+      encoding: 'utf-8',
+      timeout: 3000,
+      stdio: ['ignore', 'ignore', 'ignore'],
+      windowsHide: true,
+    });
+    return !selfTest.error && selfTest.status === 42;
+  } catch {
+    return false;
+  }
+}
+
+function resolveUnixGuardTimeout() {
+  if (unixGuardTimeoutCache !== undefined) return unixGuardTimeoutCache;
+  unixGuardTimeoutCache = null;
+  const fromEnv = process.env.GITNEXUS_HOOK_TIMEOUT_PATH;
+  const trimmed = fromEnv ? String(fromEnv).trim() : '';
+  if (trimmed === 'disabled') return unixGuardTimeoutCache;
+  const candidates = [];
+  if (trimmed && fs.existsSync(trimmed)) candidates.push(trimmed);
+  for (const builtin of [
+    '/usr/bin/timeout',
+    '/bin/timeout',
+    '/opt/homebrew/bin/gtimeout',
+    '/usr/local/bin/gtimeout',
+  ]) {
+    try {
+      if (fs.existsSync(builtin)) candidates.push(builtin);
+    } catch {
+      /* ignore */
+    }
+  }
+  for (const candidate of candidates) {
+    if (passesGuardSelfTest(candidate)) {
+      unixGuardTimeoutCache = candidate;
+      break;
+    }
+  }
+  return unixGuardTimeoutCache;
+}
+
+function resolveWindowsPowerShellPath() {
+  const fromEnv = process.env.GITNEXUS_HOOK_POWERSHELL_PATH;
+  if (fromEnv && String(fromEnv).trim() && fs.existsSync(String(fromEnv).trim())) {
+    return String(fromEnv).trim();
+  }
+  const root = process.env.SystemRoot || 'C:\\Windows';
+  const ps = path.join(root, 'System32', 'WindowsPowerShell', 'v1.0', 'powershell.exe');
+  if (fs.existsSync(ps)) return ps;
+  const psWow = path.join(root, 'SysWOW64', 'WindowsPowerShell', 'v1.0', 'powershell.exe');
+  if (fs.existsSync(psWow)) return psWow;
+  return 'powershell.exe';
+}
+
+// Sentinel:
+//   undefined = not loaded yet (try the read)
+//   string    = encoded PowerShell command (successful load)
+//   null      = load attempted and failed (do not retry; warning already emitted)
+let windowsRmListPsEncodedCommandCache;
+let windowsRmListPsLoadFailureWarned = false;
+function getWindowsRmListEncodedCommand() {
+  if (windowsRmListPsEncodedCommandCache !== undefined) {
+    return windowsRmListPsEncodedCommandCache;
+  }
+  try {
+    const ps1Path = path.join(__dirname, 'win-rm-list-json.ps1');
+    const src = fs
+      .readFileSync(ps1Path, 'utf8')
+      .replace(/^\uFEFF/, '')
+      .replace(/\r\n/g, '\n');
+    windowsRmListPsEncodedCommandCache = Buffer.from(src, 'utf16le').toString('base64');
+  } catch (err) {
+    windowsRmListPsEncodedCommandCache = null;
+    if (
+      !windowsRmListPsLoadFailureWarned &&
+      (process.env.GITNEXUS_DEBUG === '1' || process.env.GITNEXUS_DEBUG === 'true')
+    ) {
+      windowsRmListPsLoadFailureWarned = true;
+      const msg = err && err.message ? String(err.message).slice(0, 200) : 'unknown';
+      process.stderr.write(`[GitNexus hook] win-rm-list-json.ps1 load failed: ${msg}\n`);
+    }
+  }
+  return windowsRmListPsEncodedCommandCache;
+}
+
+function hasGitNexusServerOwnerWindows(dbPathAbs, myPid) {
+  const encoded = getWindowsRmListEncodedCommand();
+  if (!encoded) return false;
+  const psExe = resolveWindowsPowerShellPath();
+  const r = spawnSync(
+    psExe,
+    [
+      '-NoProfile',
+      '-NonInteractive',
+      '-ExecutionPolicy',
+      'Bypass',
+      '-STA',
+      '-EncodedCommand',
+      encoded,
+    ],
+    {
+      encoding: 'utf-8',
+      timeout: 6000,
+      stdio: ['ignore', 'pipe', 'ignore'],
+      windowsHide: true,
+      env: { ...process.env, GITNEXUS_HOOK_RM_TARGET: dbPathAbs },
+    },
+  );
+  // ETIMEDOUT means the PowerShell probe didn't return in time; treat as 'unresponsive process holds DB' → fail-closed (skip augment).
+  if (r.error) return r.error.code === 'ETIMEDOUT';
+  if (r.status !== 0) return false;
+  let rows;
+  try {
+    rows = JSON.parse(String(r.stdout || '').trim() || '[]');
+  } catch {
+    return false;
+  }
+  if (!Array.isArray(rows)) return false;
+  for (const row of rows) {
+    const procId = Number(row.pid);
+    const cmd = String(row.cmd || '');
+    if (!Number.isFinite(procId) || procId === myPid) continue;
+    if (isGitNexusServerCommand(cmd)) return true;
+  }
+  return false;
+}
+
+// The procfs root every Linux scan path reads from. Production is always /proc;
+// GITNEXUS_HOOK_PROC_ROOT only exists so unit tests can inject a fixture tree
+// (comm + cmdline + fd symlinks) and assert the three-phase logic without
+// scanning the real, ~hundreds-of-process /proc of the test host.
+//
+// Test-only gate (F4): the override is honored ONLY under a test runner —
+// vitest injects VITEST="true" and NODE_ENV="test" into every worker (verified;
+// a production hook is `node <file>.cjs` with neither set). Without the gate, a
+// production env that accidentally leaked GITNEXUS_HOOK_PROC_ROOT (pointing at an
+// empty/bad tree) would make readdirSync find no pids -> 'not-owned' -> Linux
+// owner detection silently OFF (fail-OPEN: augment races the real server for the
+// lbug, the #1492 class). Gating to the test signal makes that leak inert in
+// production (always /proc) while the fake-procfs unit tests, which run under
+// vitest, still inject freely. Unset env (or non-test context) => /proc, so the
+// production path is byte-for-byte the historical behavior.
+function isTestContext() {
+  return (
+    process.env.VITEST === 'true' || process.env.VITEST === '1' || process.env.NODE_ENV === 'test'
+  );
+}
+function getProcRoot() {
+  if (!isTestContext()) return '/proc';
+  const raw = process.env.GITNEXUS_HOOK_PROC_ROOT;
+  return raw && String(raw).trim() ? String(raw) : '/proc';
+}
+
+// Max bytes read from /proc/<pid>/cmdline in Phase 1. Bounded by default so a
+// D-state holder wedged on mmap_lock, or a process with a pathological multi-MB
+// argv, can't stall the hook. 16 KiB comfortably clears a realistic
+// `node <abs path to .../node_modules/gitnexus/dist/cli/index.js> mcp` line
+// (the `mcp`/`serve` mode token lives at the very tail, so the cap must be large
+// enough to reach it — see PROC_CMDLINE_FLOOR escalation below). Overridable for
+// tests; never goes below PROC_CMDLINE_FLOOR.
+const PROC_CMDLINE_FLOOR = 4096;
+function getCmdlineMaxBytes() {
+  const raw = process.env.GITNEXUS_HOOK_PROC_CMDLINE_MAX;
+  // Number() (not parseInt) so "8e3" reads as 8000, not 8 (parseInt stops at
+  // 'e'). The `raw && String(raw).trim()` guard keeps empty/whitespace on the
+  // default; trailing garbage ("8abc") now -> NaN -> default (stricter).
+  const n = raw && String(raw).trim() ? Number(String(raw).trim()) : NaN;
+  if (Number.isFinite(n) && n >= PROC_CMDLINE_FLOOR) return n;
+  return 16384;
+}
+
+// Phase 0 comm prefilter. /proc/<pid>/comm is the kernel task->comm string,
+// capped at 16 bytes INCLUDING the trailing NUL — i.e. at most 15 visible
+// chars, truncated by the kernel with no marker. So a process whose real name
+// is longer than 15 chars shows a 15-char prefix here. The match below is
+// therefore truncation-safe in BOTH directions (a whitelist name that is a
+// prefix of comm, or comm that is a prefix of a whitelist name, both count) to
+// guarantee we never drop a real owner at this cheap stage — Phase 2's dev+ino
+// fd check is the real authority; Phase 0/1 only exist to skip the overwhelming
+// majority (kernel threads, shells, editors) cheaply.
+//
+// The whitelist is calibrated against what a real `gitnexus mcp`/`serve` server
+// actually reports for comm. Observed on production hosts: the server renames
+// its main thread, so comm reads `MainThread` (via @ladybugdb/core's
+// worker_threads setup), NOT `node` — omitting it would blind the probe to
+// every real server (#1492-class owner miss). We also keep the plausible
+// launcher/runtime basenames in case a future build does not rename the thread.
+// Conservative by design: over-collecting a few extra candidates only costs a
+// bounded number of Phase 1 cmdline reads.
+const COMM_CANDIDATES = ['node', 'gitnexus', 'bun', 'deno', 'npm', 'npx', 'MainThread'];
+function commLooksLikeServer(comm) {
+  const c = comm.trim();
+  if (!c) return false;
+  for (const name of COMM_CANDIDATES) {
+    if (name === c || name.startsWith(c) || c.startsWith(name)) return true;
+  }
+  return false;
+}
+
+function readProcComm(procRoot, pidStr) {
+  try {
+    return fs
+      .readFileSync(path.join(procRoot, pidStr, 'comm'), 'utf8')
+      .replace(/\0+/g, '')
+      .trim();
+  } catch {
+    return '';
+  }
+}
+
+// Timeout sentinel for readLinuxCmdline (F3). MUST be distinct from the
+// "unreadable/empty" return value (''): '' flows through isGitNexusServerCommand
+// as a NON-candidate (both regexes are false on ''), so the Phase 1 caller
+// `continue`s past it — correct for a raced/openSync-failed pid, but a FAIL-OPEN
+// bug if it ever meant "I ran out of budget mid-read" (a real owner whose
+// escalation timed out would be silently dropped, racing the lbug -> #1492). A
+// unique Symbol can never collide with any cmdline string, so the caller can
+// branch on it explicitly and map a mid-read timeout to the tri-state 'timeout'
+// (fail-CLOSED) instead of swallowing it as a non-candidate.
+const CMDLINE_TIMEOUT = Symbol('gitnexus.cmdline.timeout');
+
+// Bounded /proc/<pid>/cmdline read for Phase 1. openSync+readSync (not
+// readFileSync) so a D-state holder cannot stall the hook on a huge or
+// never-EOF argv: we read at most `cap` bytes and stop. cmdline separates argv
+// with NULs; convert to spaces for isGitNexusServerCommand.
+//
+// Owner-miss guard for the 4 KB cap: the `gitnexus` token usually sits in the
+// first path component while the `mcp`/`serve` mode token is the LAST argv, so
+// a naive 4 KB read could clip the mode token off a server launched with a very
+// long interpreter path and silently miss a real owner. We mitigate two ways:
+// (a) the default cap (16 KiB) already clears realistic lines; (b) if the first
+// read fills the cap AND already contains the `gitnexus` token but no mode
+// token yet, we keep reading in bounded chunks (up to a hard ceiling) until the
+// mode token appears or the file ends — so a genuine server is never missed for
+// want of a few more bytes, while non-candidates still pay only the initial
+// bounded read.
+//
+// Budget (F3): the escalation loop above is the one place a SINGLE pathological
+// candidate could read up to HARD_CEIL (256 KiB) before the next scan-level
+// budget check, weakening the timeout contract. `outOfBudget` (the scan's shared
+// deadline callback) is checked once per escalation iteration; on expiry we
+// return CMDLINE_TIMEOUT (NOT '') so the caller can fail-closed honestly rather
+// than mistake the partial read for a non-candidate. Reads that simply can't
+// open / error out still return '' (genuinely "not a readable candidate").
+function readLinuxCmdline(procRoot, pidStr, cap, outOfBudget) {
+  const file = path.join(procRoot, pidStr, 'cmdline');
+  let fd;
+  try {
+    fd = fs.openSync(file, 'r');
+  } catch {
+    return '';
+  }
+  try {
+    const HARD_CEIL = 262144; // 256 KiB absolute ceiling for the escalation path
+    let collected = Buffer.alloc(0);
+    let offset = 0;
+    let chunkCap = cap;
+    for (;;) {
+      // allocUnsafe is safe here: readSync fills exactly [0, bytes), only
+      // buf.subarray(0, bytes) is consumed, and Buffer.concat deep-copies that
+      // slice into `collected`, so the uninitialized tail never reaches decode.
+      const buf = Buffer.allocUnsafe(chunkCap);
+      const bytes = fs.readSync(fd, buf, 0, chunkCap, offset);
+      if (bytes <= 0) break;
+      collected = Buffer.concat([collected, buf.subarray(0, bytes)]);
+      offset += bytes;
+      const text = collected.toString('utf8').replace(/\0+/g, ' ');
+      // Stop early when we can already decide "owner": has both the gitnexus
+      // token and a mode token. Keep going only when gitnexus is present but
+      // the mode token might be just past the boundary.
+      const hasGitNexus =
+        /(?:^|[/\\\s])gitnexus(?:\.cmd)?(?:\s|$)/.test(text) ||
+        /node_modules[/\\]gitnexus[/\\]/.test(text);
+      const hasMode = /(?:^|\s)(mcp|serve)(?:\s|$)/.test(text);
+      if (hasMode) break; // decided (positive); isGitNexusServerCommand re-checks below
+      if (bytes < chunkCap) break; // EOF: full cmdline read, definitive
+      if (!hasGitNexus) break; // not a candidate; do not escalate the read
+      if (offset >= HARD_CEIL) break; // bounded escalation only
+      // Budget gate the escalation: a single huge-argv candidate must not burn
+      // the whole scan deadline before we re-check. Return the timeout sentinel
+      // (never '') so the caller fails closed instead of treating us as a
+      // non-candidate. The sole caller (linuxProcScanFindGitNexusServer) always
+      // passes outOfBudget, so no presence guard is needed.
+      if (outOfBudget()) return CMDLINE_TIMEOUT;
+      chunkCap = cap; // keep reading more in cap-sized chunks
+    }
+    return collected.toString('utf8').replace(/\0+/g, ' ').trim();
+  } catch {
+    return '';
+  } finally {
+    try {
+      fs.closeSync(fd);
+    } catch {
+      /* ignore */
+    }
+  }
+}
+
+function resolveLinuxProcBudgetMs() {
+  const raw = process.env.GITNEXUS_HOOK_LINUX_PROC_BUDGET_MS;
+  // Gate on the STRING's emptiness, NOT the parsed number's truthiness — the
+  // old `Number(raw && trim()) ? ... : 1200` form treated "0" as falsy and
+  // silently fell back to 1200 (#2180). Use Number() (not parseInt) so "16e3"
+  // reads as 16000, not 16 (parseInt stops at 'e'). The `&& String(raw).trim()`
+  // guard is load-bearing: without it a set-but-empty/whitespace value would be
+  // `Number("")===0` => budget 0 => immediate fail-CLOSED timeout (augment
+  // permanently skipped). With it, ''/whitespace => NaN => 1200 default, while a
+  // finite "0" still parses to an explicit, deterministic "no budget" =>
+  // immediate timeout. Non-numeric / unset => default 1200.
+  const n = raw != null && String(raw).trim() ? Number(String(raw).trim()) : NaN;
+  if (!Number.isFinite(n)) return 1200;
+  return n; // may be <= 0, meaning "out of budget on the first check"
+}
+
+// Returns one of: 'owned' (a non-self process with a GitNexus-server cmdline
+// holds the target lbug fd), 'not-owned' (scan completed, no such owner), or
+// 'timeout' (the per-scan budget was exhausted before a verdict). The name is
+// pinned by a source-contract test; only the return TYPE changed (#2180:
+// boolean -> tri-state, so the dispatcher can fail-closed on 'timeout').
+function linuxProcScanFindGitNexusServer(dbPathAbs, myPid) {
+  const budget = resolveLinuxProcBudgetMs();
+  // A non-positive budget is an explicit, deterministic "no time to scan" =>
+  // immediate timeout (the #2180 test vector, and the only correct reading of
+  // the fixed parse: "0" must NOT mean 1200). Returning before any procfs read
+  // keeps it instantaneous regardless of host load.
+  if (budget <= 0) return 'timeout';
+  const procRoot = getProcRoot();
+  const cmdlineCap = getCmdlineMaxBytes();
+  const start = Date.now();
+  const outOfBudget = () => Date.now() - start > budget;
+
+  let targetStat;
+  try {
+    targetStat = fs.statSync(dbPathAbs);
+  } catch {
+    // Caller already existsSync'd the path; a stat failure here is a transient
+    // race, treat as no owner (historical semantics).
+    return 'not-owned';
+  }
+
+  let procEntries;
+  try {
+    procEntries = fs.readdirSync(procRoot, { withFileTypes: true });
+  } catch {
+    return 'not-owned';
+  }
+
+  // Phase 0 + Phase 1: collect the few PIDs whose comm AND cmdline look like a
+  // GitNexus server, without touching any fd yet.
+  const candidates = [];
+  for (const ent of procEntries) {
+    if (outOfBudget()) return 'timeout';
+    if (!ent.isDirectory() || !/^\d+$/.test(ent.name)) continue;
+    const pid = Number.parseInt(ent.name, 10);
+    if (!Number.isFinite(pid) || pid === myPid) continue;
+
+    // Phase 0: cheap comm prefilter.
+    const comm = readProcComm(procRoot, ent.name);
+    if (!comm) continue; // unreadable comm (kernel thread, raced exit) -> skip
+    if (!commLooksLikeServer(comm)) continue;
+
+    // Phase 1: bounded cmdline read + isGitNexusServerCommand prefilter.
+    if (outOfBudget()) return 'timeout';
+    const cmdline = readLinuxCmdline(procRoot, ent.name, cmdlineCap, outOfBudget);
+    // F3: a mid-read budget timeout returns the CMDLINE_TIMEOUT sentinel (a
+    // Symbol, never a string). Fail CLOSED on it rather than letting it fall
+    // through isGitNexusServerCommand as a non-candidate — a real owner whose
+    // escalation timed out must not be silently dropped (would fail-OPEN).
+    if (cmdline === CMDLINE_TIMEOUT) return 'timeout';
+    if (!isGitNexusServerCommand(cmdline)) continue;
+    candidates.push(ent.name);
+  }
+
+  // Phase 2: only now stat the fds of the (typically 0-2) survivors.
+  for (const pidStr of candidates) {
+    if (outOfBudget()) return 'timeout';
+    const fdDir = path.join(procRoot, pidStr, 'fd');
+    let fds;
+    try {
+      fds = fs.readdirSync(fdDir);
+    } catch (err) {
+      // F1: the old code returned 'owned' for EVERY non-ENOENT error. That was
+      // a correctness bug: /proc/<pid>/fd is owner-only (mode 0500), so a
+      // cross-user/root `gitnexus mcp` serving a DIFFERENT repo passes Phase 0+1
+      // (its cmdline matches) and then EACCES'es here — yet its dev+ino was
+      // NEVER compared against THIS lbug. Claiming 'owned' lets it permanently,
+      // silently suppress augment for a repo it does not actually lock. We now
+      // distinguish the failure shapes (all still fail-closed where we can't
+      // prove non-ownership, but 'timeout' is the HONEST verdict for
+      // "inconclusive", not the false-positive 'owned'):
+      const code = err && err.code;
+      if (code === 'ENOENT') {
+        // Process raced away between the candidate scan and now -> genuinely no
+        // longer an owner. Move on.
+        continue;
+      }
+      if (code === 'EACCES' || code === 'EPERM') {
+        // Permission-denied fd dir: cannot read fds, so ownership is
+        // UNVERIFIABLE. Fail closed honestly via 'timeout' (the dispatcher maps
+        // timeout -> true, same protective skip as before) WITHOUT lying that we
+        // confirmed ownership. Do NOT degrade to not-owned/fail-open: if this
+        // really is the owner, fail-open re-opens the #1492 lbug race; augment
+        // is optional context, so a conservative skip costs little.
+        debugLog(
+          `fd dir unreadable for candidate pid ${pidStr} (${code}); ownership ` +
+            `unverifiable, probe inconclusive -> fail-closed (timeout)`,
+        );
+        return 'timeout';
+      }
+      if (code === 'EIO' || code === 'ESTALE') {
+        // Genuine transient I/O against this candidate's fd dir — not evidence
+        // it does NOT hold the lbug. Treat as inconclusive and fail closed
+        // (timeout) rather than continue, so a real owner mid-I/O-blip is not
+        // dropped (would fail-open).
+        debugLog(
+          `fd dir transient I/O error for candidate pid ${pidStr} (${code}); ` +
+            `probe inconclusive -> fail-closed (timeout)`,
+        );
+        return 'timeout';
+      }
+      // Any other shape (ENOTDIR — fd path is not a directory at all, so this
+      // is not a plausible live-procfs owner — and the long tail) is treated as
+      // "this candidate is not an owner": move to the next candidate instead of
+      // the old blanket 'owned'. If no other candidate owns the lbug the scan
+      // ends not-owned (dispatcher fail-open) — acceptable because ENOTDIR means
+      // the fd entry is structurally not a real /proc/<pid>/fd.
+      debugLog(
+        `fd dir not a readable directory for candidate pid ${pidStr} ` +
+          `(${code || 'unknown'}); treating candidate as non-owner -> continue`,
+      );
+      continue;
+    }
+    for (const fd of fds) {
+      if (outOfBudget()) return 'timeout';
+      try {
+        const st = fs.statSync(path.join(fdDir, fd));
+        if (st.dev === targetStat.dev && st.ino === targetStat.ino) {
+          return 'owned';
+        }
+      } catch {
+        /* fd raced closed; ignore */
+      }
+    }
+  }
+
+  return 'not-owned';
+}
+
+function unixLsofPsFindGitNexusServer(dbPathAbs, myPid) {
+  const guard = resolveUnixGuardTimeout();
+  // An explicit missing override models ENOENT and must fail open instead of
+  // falling through to a host binary with different process-table visibility.
+  if (hasMissingHookBinaryOverride('lsof')) return false;
+  const lsofPath = resolveHookBinary('lsof');
+  // The spawnSync timeouts below (lsof 1000ms / ps 500ms) are deliberately
+  // SHORTER than the wrapper budgets (2s / 1s): on the supervised path Node's
+  // SIGTERM always fires first, so `error.code === 'ETIMEDOUT'` and the
+  // fail-closed contract are untouched. The wrapper only matters once this
+  // hook process has been SIGKILLed and can no longer deliver that SIGTERM.
+  const [lsofCmd, lsofArgs] = guard
+    ? [guard, ['-k', '1', '2', lsofPath, '-nP', '-t', '--', dbPathAbs]]
+    : [lsofPath, ['-nP', '-t', '--', dbPathAbs]];
+  const lsof = spawnSync(lsofCmd, lsofArgs, {
+    encoding: 'utf-8',
+    timeout: 1000,
+    stdio: ['ignore', 'pipe', 'ignore'],
+    windowsHide: true,
+  });
+  if (lsof.error) return lsof.error.code === 'ETIMEDOUT';
+  // Guard-mediated deaths map to "unresponsive holder" (fail-closed). Three
+  // result shapes, verified against coreutils 9.1:
+  //   - signal-death: when `-k` escalates to SIGKILL, coreutils timeout
+  //     SELF-RAISES the signal, so spawnSync reports {status: null, signal}
+  //     with no .error (spawnSync's own ETIMEDOUT was handled above). The
+  //     same shape appears when this hook is frozen >2s (SIGSTOP, laptop
+  //     suspend) and the guard expires while it sleeps. By construction, a
+  //     guard-wrapped probe that died by signal without spawnSync ETIMEDOUT
+  //     is a budget/kill outcome.
+  //   - 124: budget expired and the child exited after the plain SIGTERM.
+  //   - 137: NOT the coreutils -k path — only exit-code-propagating wrappers,
+  //     or a child SIGKILLed externally (e.g. the OOM killer).
+  if (guard && lsof.status === null && lsof.signal) return true;
+  if (guard && (lsof.status === 124 || lsof.status === 137)) return true;
+
+  const pids = (lsof.stdout || '').split(/\s+/).filter(Boolean);
+  const psMissing = hasMissingHookBinaryOverride('ps');
+  const psPath = resolveHookBinary('ps');
+  for (const pid of pids) {
+    if (Number(pid) === myPid) continue;
+    // Missing ps means we cannot verify that this pid is a GitNexus server.
+    if (psMissing) continue;
+    const [psCmd, psArgs] = guard
+      ? [guard, ['-k', '1', '1', psPath, '-p', pid, '-o', 'command=']]
+      : [psPath, ['-p', pid, '-o', 'command=']];
+    const ps = spawnSync(psCmd, psArgs, {
+      encoding: 'utf-8',
+      timeout: 500,
+      stdio: ['ignore', 'pipe', 'ignore'],
+      windowsHide: true,
+    });
+    if (ps.error) {
+      if (ps.error.code === 'ETIMEDOUT') return true;
+      continue;
+    }
+    // Same guard-mediated-death mapping as the lsof call above (signal-death
+    // from the -k escalation or a frozen hook; 124 budget expiry; 137 only
+    // for exit-code-propagating wrappers / external SIGKILL).
+    if (guard && ps.status === null && ps.signal) return true;
+    if (guard && (ps.status === 124 || ps.status === 137)) return true;
+    if (isGitNexusServerCommand(ps.stdout || '')) return true;
+  }
+  return false;
+}
+
+/**
+ * @param {string} dbPath Absolute or relative path to the DB file (e.g. .../lbug).
+ * @param {number} myPid Current process PID (hook runner), excluded from matches.
+ */
+function hasGitNexusDbLockedByGitNexusServer(dbPath, myPid) {
+  if (!fs.existsSync(dbPath)) return false;
+  const dbPathAbs = path.resolve(dbPath);
+
+  if (process.platform === 'win32') {
+    return hasGitNexusServerOwnerWindows(dbPathAbs, myPid);
+  }
+
+  if (process.platform === 'linux') {
+    // #2180: cmdline-first procfs scan, no lsof. 'timeout' fails CLOSED
+    // (overloaded host self-throttles — the throttle the orphan-storm incident
+    // needed; the old lsof fallback ETIMEDOUT'd and failed closed on these same
+    // hosts anyway, only slower and with the orphan risk). 'not-owned' is the
+    // only false. See the fail matrix in the file header.
+    const verdict = linuxProcScanFindGitNexusServer(dbPathAbs, myPid);
+    return verdict !== 'not-owned';
+  }
+
+  return unixLsofPsFindGitNexusServer(dbPathAbs, myPid);
+}
+
+module.exports = {
+  hasGitNexusDbLockedByGitNexusServer,
+  // Exported for white-box unit tests that must assert the tri-state verdict
+  // ('owned' | 'not-owned' | 'timeout') directly — the dispatcher collapses
+  // timeout and owned to the same boolean true, so the boolean API alone cannot
+  // distinguish the F1 EACCES->timeout fix from the old EACCES->owned bug. The
+  // Probe interface already declares this optional. Linux-only by contract; the
+  // name is pinned by a source-contract test.
+  linuxProcScanFindGitNexusServer,
+  // #2163 follow-up: the hook adapters wrap the augment CLI in the same
+  // guard. Returns a self-tested wrapper path — the built-in candidates are
+  // always absolute; a GITNEXUS_HOOK_TIMEOUT_PATH override is adopted as the
+  // exact string that passed the self-test. Same string is also the same
+  // RESOLUTION for absolute paths and for slashless names (PATH lookup is
+  // cwd-independent); a slash-containing RELATIVE override, however, is
+  // existsSync-checked and self-tested against this process's cwd while the
+  // adapters spawn the CLI with a `cwd` option (chdir-before-exec), so such
+  // a value can pass here yet ENOENT at the augment call site — set the
+  // override to an absolute path. Returns null when the wrapper is
+  // disabled/unavailable. Never call on win32 (see its JSDoc).
+  resolveUnixGuardTimeout,
+  // Exported for white-box unit tests of the numeric-env parsing (#2183 review):
+  // Number()-not-parseInt so "16e3" reads as 16000, plus the empty/whitespace
+  // guard that keeps a set-but-empty budget on the 1200 default instead of an
+  // immediate fail-closed timeout. Tested directly because the values are
+  // otherwise only observable indirectly through scan timing/escalation.
+  getCmdlineMaxBytes,
+  resolveLinuxProcBudgetMs,
+};
diff --git a/gitnexus-factory-plugin/hooks/hook-lock.js b/gitnexus-factory-plugin/hooks/hook-lock.js
new file mode 100644
index 000000000..759856384
--- /dev/null
+++ b/gitnexus-factory-plugin/hooks/hook-lock.js
@@ -0,0 +1,119 @@
+const fs = require('fs');
+const path = require('path');
+
+const HOOK_LOCK_SUBDIR = '.hook-locks';
+const HOOK_LOCK_MAX_INFLIGHT = 3;
+const HOOK_LOCK_STALE_MS = 30000;
+
+function acquireHookSlot(gitNexusDir) {
+  const lockDir = path.join(gitNexusDir, HOOK_LOCK_SUBDIR);
+  try {
+    fs.mkdirSync(lockDir, { recursive: true });
+  } catch {
+    // Cannot create lock dir (read-only fs, cross-user perm denial, out of
+    // inodes, etc.) — fail closed by returning null. Caller skips augment.
+    // Fail-open here would let N concurrent hooks all proceed unguarded and
+    // reintroduce the #1486 fan-out the guard exists to prevent.
+    return null;
+  }
+
+  const myPidStr = String(process.pid);
+
+  for (let slot = 0; slot < HOOK_LOCK_MAX_INFLIGHT; slot++) {
+    const slotPath = path.join(lockDir, `slot-${slot}.lock`);
+    for (let attempt = 0; attempt < 2; attempt++) {
+      try {
+        fs.writeFileSync(slotPath, myPidStr, { flag: 'wx' });
+        let released = false;
+        const release = () => {
+          if (released) return;
+          released = true;
+          try {
+            // Only unlink if we still own the slot. If we appeared stale and
+            // another hook took over, the file now belongs to it — leave alone.
+            const content = fs.readFileSync(slotPath, 'utf-8').trim();
+            if (content === myPidStr) fs.unlinkSync(slotPath);
+          } catch {
+            /* already removed or unreadable */
+          }
+        };
+        process.on('exit', release);
+        return release;
+      } catch {
+        // Slot exists. Decide whether to take it over.
+        // Open once and inspect mtime + content via the same fd so there's
+        // no TOCTOU between the metadata check and the content read
+        // (codeql js/file-system-race).
+        let fd;
+        try {
+          fd = fs.openSync(slotPath, 'r');
+        } catch {
+          continue; // Vanished between EEXIST and open — retry this slot.
+        }
+        let isLive = false;
+        let mtimeMs = Date.now();
+        try {
+          mtimeMs = fs.fstatSync(fd).mtimeMs;
+          const buf = Buffer.alloc(32);
+          const n = fs.readSync(fd, buf, 0, 32, 0);
+          const ownerStr = buf.slice(0, n).toString('utf-8').trim();
+          if (ownerStr === '') {
+            // Owner created the file but hasn't written its PID yet. The
+            // wx open+write window is microseconds; give it the benefit
+            // of the doubt and treat as live.
+            isLive = true;
+          } else {
+            const owner = Number.parseInt(ownerStr, 10);
+            if (Number.isFinite(owner) && owner > 0) {
+              try {
+                process.kill(owner, 0);
+                isLive = true;
+              } catch (e) {
+                // ESRCH = process gone → treat as dead. EPERM = process exists
+                // but owned by another user (cross-user lock dir) → still alive,
+                // keep the slot. Anything else: be conservative, assume alive.
+                if (e && e.code === 'ESRCH') {
+                  isLive = false;
+                } else {
+                  isLive = true;
+                }
+              }
+            }
+          }
+        } catch {
+          /* unreadable — treat as dead */
+        } finally {
+          try {
+            fs.closeSync(fd);
+          } catch {
+            /* already closed */
+          }
+        }
+        // For slots younger than HOOK_LOCK_STALE_MS, PID-liveness wins —
+        // a slow-but-alive hook is never wrongly evicted. For older slots,
+        // age is the final arbiter as a defense against PID reuse on long-
+        // abandoned slots. 30s >> the 7s augment timeout, so a healthy run
+        // never crosses this threshold.
+        if (isLive && Date.now() - mtimeMs > HOOK_LOCK_STALE_MS) {
+          isLive = false;
+        }
+        if (isLive) break; // Try the next slot.
+        try {
+          fs.unlinkSync(slotPath);
+        } catch {
+          /* another hook beat us to it — retry will hit EEXIST */
+        }
+        // Loop and retry this slot.
+      }
+    }
+  }
+
+  return null;
+}
+
+module.exports = {
+  HOOK_LOCK_SUBDIR,
+  HOOK_LOCK_MAX_INFLIGHT,
+  HOOK_LOCK_STALE_MS,
+  acquireHookSlot,
+};
diff --git a/gitnexus-factory-plugin/hooks/win-rm-list-json.ps1 b/gitnexus-factory-plugin/hooks/win-rm-list-json.ps1
new file mode 100644
index 000000000..5c1564e30
--- /dev/null
+++ b/gitnexus-factory-plugin/hooks/win-rm-list-json.ps1
@@ -0,0 +1,76 @@
+$ErrorActionPreference = 'Stop'
+$target = $env:GITNEXUS_HOOK_RM_TARGET
+if ([string]::IsNullOrWhiteSpace($target)) { Write-Output '[]'; exit 0 }
+$target = (Resolve-Path -LiteralPath $target).ProviderPath
+
+if (-not ([Management.Automation.PSTypeName]'GitNexusHookRm.Native').Type) {
+Add-Type @'
+using System;
+using System.Runtime.InteropServices;
+namespace GitNexusHookRm {
+  public static class Native {
+    public const int ErrorMoreData = 234;
+    [StructLayout(LayoutKind.Sequential, Pack = 4)]
+    public struct RM_UNIQUE_PROCESS {
+      public int dwProcessId;
+      public long ProcessStartTime;
+    }
+    [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]
+    public struct RM_PROCESS_INFO {
+      public RM_UNIQUE_PROCESS Process;
+      [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 256)]
+      public string strAppName;
+      [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 64)]
+      public string strServiceShortName;
+      public uint ApplicationType;
+      public uint AppStatus;
+      public uint TSSessionId;
+      public uint bRestartable;
+    }
+    [DllImport("rstrtmgr.dll", CharSet = CharSet.Unicode)]
+    public static extern int RmStartSession(out uint pSessionHandle, uint dwSessionFlags, string strSessionKey);
+    [DllImport("rstrtmgr.dll", CharSet = CharSet.Unicode)]
+    public static extern int RmRegisterResources(uint pSessionHandle, uint nFiles, string[] rgsFileNames, uint nApplications, IntPtr rgApplications, uint nServices, string[] rgsServiceNames);
+    [DllImport("rstrtmgr.dll")]
+    public static extern int RmGetList(uint dwSessionHandle, out uint pnProcInfoNeeded, ref uint pnProcInfo, [In, Out] RM_PROCESS_INFO[] rgAffectedApps, ref uint lpdwRebootReasons);
+    [DllImport("rstrtmgr.dll")]
+    public static extern int RmEndSession(uint pSessionHandle);
+  }
+}
+'@
+}
+
+$h = [uint32]0
+$key = [guid]::NewGuid().ToString('N')
+$rmErr = [GitNexusHookRm.Native]::RmStartSession([ref]$h, 0, $key)
+if ($rmErr -ne 0) { Write-Output '[]'; exit 0 }
+$files = @($target)
+$err = [GitNexusHookRm.Native]::RmRegisterResources($h, 1, $files, 0, [IntPtr]::Zero, 0, $null)
+if ($err -ne 0) {
+  [void][GitNexusHookRm.Native]::RmEndSession($h)
+  Write-Output '[]'
+  exit 0
+}
+$need = [uint32]0
+$n = [uint32]0
+$reboot = [uint32]0
+$err = [GitNexusHookRm.Native]::RmGetList($h, [ref]$need, [ref]$n, $null, [ref]$reboot)
+if ($err -ne [GitNexusHookRm.Native]::ErrorMoreData) {
+  [void][GitNexusHookRm.Native]::RmEndSession($h)
+  Write-Output '[]'
+  exit 0
+}
+$n = $need
+$buf = New-Object GitNexusHookRm.Native+RM_PROCESS_INFO[] ([int]$n)
+$err = [GitNexusHookRm.Native]::RmGetList($h, [ref]$need, [ref]$n, $buf, [ref]$reboot)
+[void][GitNexusHookRm.Native]::RmEndSession($h)
+if ($err -ne 0) { Write-Output '[]'; exit 0 }
+
+$out = @()
+for ($i = 0; $i -lt [int]$n; $i++) {
+  $procId = $buf[$i].Process.dwProcessId
+  $p = Get-CimInstance -ClassName Win32_Process -Filter "ProcessId=$procId" -ErrorAction SilentlyContinue
+  $cmd = if ($p) { $p.CommandLine } else { '' }
+  $out += [PSCustomObject]@{ pid = [int]$procId; cmd = $cmd }
+}
+ConvertTo-Json -InputObject @($out) -Compress
diff --git a/gitnexus/test/unit/factory-plugin.test.ts b/gitnexus/test/unit/factory-plugin.test.ts
new file mode 100644
index 000000000..4d6f836e3
--- /dev/null
+++ b/gitnexus/test/unit/factory-plugin.test.ts
@@ -0,0 +1,336 @@
+/**
+ * Tests: GitNexus Factory AI (Droid) plugin
+ *
+ * Covers the standalone `gitnexus-factory-plugin/` used by `droid plugin
+ * install`:
+ * - manifest + hook wiring (plugin.json / mcp.json / hooks.json)
+ * - the PostToolUse search-augment hook's guard reuse and early-exit behavior
+ * - a drift guard proving the bundled guard modules are byte-identical to the
+ *   canonical Claude-adapter copies (so a fix to one can't silently skip the
+ *   other)
+ *
+ * The augment fan-out guard (acquireHookSlot) and the LadybugDB owner probe are
+ * the exact modules the Claude/Codex adapter ships; their internals are covered
+ * by hooks.test.ts and hook-db-lock-probe.test.ts. Here we assert the Factory
+ * hook WIRES them and behaves correctly on the Factory-specific paths.
+ */
+import { describe, it, expect, beforeAll, afterAll } from 'vitest';
+import { spawnSync } from 'child_process';
+import fs from 'fs';
+import path from 'path';
+import os from 'os';
+import {
+  runHook,
+  parseHookOutput,
+  createHookToolDir,
+  hookEnv,
+} from '../utils/hook-test-helpers.js';
+
+const REPO_ROOT = path.resolve(__dirname, '..', '..', '..');
+const PLUGIN_DIR = path.join(REPO_ROOT, 'gitnexus-factory-plugin');
+const HOOK = path.join(PLUGIN_DIR, 'hooks', 'gitnexus-hook.js');
+const HOOKS_JSON = path.join(PLUGIN_DIR, 'hooks', 'hooks.json');
+const PLUGIN_JSON = path.join(PLUGIN_DIR, '.factory-plugin', 'plugin.json');
+const MCP_JSON = path.join(PLUGIN_DIR, 'mcp.json');
+const CLAUDE_HOOKS = path.join(REPO_ROOT, 'gitnexus-claude-plugin', 'hooks');
+
+// Guard modules bundled into the Factory plugin, kept byte-identical to the
+// canonical Claude-adapter copies.
+const BUNDLED_GUARDS = ['hook-lock.js', 'hook-db-lock-probe.cjs', 'win-rm-list-json.ps1'] as const;
+
+// ─── Manifest / file presence ───────────────────────────────────────
+
+describe('Factory plugin files', () => {
+  it('ships the hook, its guards, and both manifests', () => {
+    for (const p of [
+      HOOK,
+      HOOKS_JSON,
+      PLUGIN_JSON,
+      MCP_JSON,
+      ...BUNDLED_GUARDS.map((f) => path.join(PLUGIN_DIR, 'hooks', f)),
+    ]) {
+      expect(fs.existsSync(p), `${p} should exist`).toBe(true);
+    }
+  });
+
+  it('.factory-plugin holds only plugin.json (Factory manifest contract)', () => {
+    expect(fs.readdirSync(path.join(PLUGIN_DIR, '.factory-plugin'))).toEqual(['plugin.json']);
+  });
+});
+
+// ─── Drift guard: bundled guards === canonical Claude copies ─────────
+
+describe('Factory plugin bundled guards stay in lockstep with the Claude adapter', () => {
+  for (const f of BUNDLED_GUARDS) {
+    it(`${f} is byte-identical to the canonical copy`, () => {
+      const bundled = fs.readFileSync(path.join(PLUGIN_DIR, 'hooks', f));
+      const canonical = fs.readFileSync(path.join(CLAUDE_HOOKS, f));
+      expect(bundled.equals(canonical)).toBe(true);
+    });
+  }
+});
+
+// ─── plugin.json ────────────────────────────────────────────────────
+
+describe('Factory plugin.json', () => {
+  const manifest = JSON.parse(fs.readFileSync(PLUGIN_JSON, 'utf-8'));
+
+  it('is named gitnexus', () => {
+    expect(manifest.name).toBe('gitnexus');
+  });
+
+  it('version matches gitnexus/package.json (single source of truth)', () => {
+    const pkg = JSON.parse(
+      fs.readFileSync(path.join(REPO_ROOT, 'gitnexus', 'package.json'), 'utf-8'),
+    );
+    expect(manifest.version).toBe(pkg.version);
+  });
+});
+
+// ─── mcp.json ───────────────────────────────────────────────────────
+
+describe('Factory mcp.json', () => {
+  const mcp = JSON.parse(fs.readFileSync(MCP_JSON, 'utf-8'));
+
+  it('registers the gitnexus MCP server under mcpServers', () => {
+    expect(mcp.mcpServers?.gitnexus?.command).toBe('npx');
+    expect(mcp.mcpServers.gitnexus.args).toContain('mcp');
+  });
+});
+
+// ─── hooks.json wiring ──────────────────────────────────────────────
+
+describe('Factory hooks.json wiring', () => {
+  const manifest = JSON.parse(fs.readFileSync(HOOKS_JSON, 'utf-8'));
+  const entry = manifest.PostToolUse[0];
+
+  it('registers a PostToolUse hook', () => {
+    expect(Array.isArray(manifest.PostToolUse)).toBe(true);
+  });
+
+  it('matches Factory search tools (Grep, Glob, Execute — not Bash)', () => {
+    expect(entry.matcher).toBe('Grep|Glob|Execute');
+    expect(entry.matcher).not.toMatch(/\bBash\b/);
+  });
+
+  it('invokes the hook via the ${DROID_PLUGIN_ROOT} plugin-root variable', () => {
+    const command: string = entry.hooks[0].command;
+    expect(command).toContain('${DROID_PLUGIN_ROOT}');
+    expect(command).toContain('hooks/gitnexus-hook.js');
+  });
+
+  it('declares timeout in seconds (not milliseconds)', () => {
+    const timeout: number = entry.hooks[0].timeout;
+    expect(typeof timeout).toBe('number');
+    expect(timeout).toBeGreaterThan(0);
+    expect(timeout).toBeLessThan(120);
+  });
+});
+
+// ─── Source regressions ─────────────────────────────────────────────
+
+describe('Factory hook source regressions', () => {
+  const source = fs.readFileSync(HOOK, 'utf-8');
+
+  it('wires the augment fan-out guard (acquireHookSlot + finally release)', () => {
+    expect(source).toContain("require('./hook-lock.js')");
+    expect(source).toContain('acquireHookSlot(');
+    expect(source).toMatch(/finally\s*\{[^}]*release\(\)/s);
+  });
+
+  it('wires the LadybugDB owner probe before running augment', () => {
+    expect(source).toContain("require('./hook-db-lock-probe.cjs')");
+    expect(source).toContain('hasGitNexusDbLockedByGitNexusServer(');
+  });
+
+  it('never passes shell: true / shell: isWin to spawnSync (injection risk)', () => {
+    for (const line of source.split('\n')) {
+      const t = line.trim();
+      if (t.startsWith('//') || t.startsWith('*')) continue;
+      expect(/shell:\s*(true|isWin)/.test(line), `injection risk: ${t}`).toBe(false);
+    }
+  });
+
+  it('invokes npx.cmd directly on Windows instead of a shell', () => {
+    expect(source).toContain('npx.cmd');
+  });
+
+  it('passes the pattern after the -- end-of-options marker', () => {
+    expect(source).toMatch(/'augment',\s*'--',\s*pattern/);
+  });
+
+  it('validates cwd is absolute and gates on a non-registry .gitnexus dir', () => {
+    expect(source).toMatch(/path\.isAbsolute\(cwd\)/);
+    expect(source).toContain('isGlobalRegistryDir');
+  });
+
+  it('emits Factory-shape hookSpecificOutput.additionalContext', () => {
+    expect(source).toContain('hookSpecificOutput');
+    expect(source).toContain('additionalContext');
+  });
+
+  it('rejects patterns shorter than 3 chars', () => {
+    expect(source).toMatch(/length\s*<\s*3/);
+  });
+});
+
+// ─── Behavior: early-exit paths (no augment spawned) ────────────────
+
+describe('Factory hook behavior — early exits', () => {
+  let tmpDir: string;
+
+  beforeAll(() => {
+    tmpDir = fs.mkdtempSync(path.join(os.tmpdir(), 'gitnexus-factory-early-'));
+  });
+  afterAll(() => fs.rmSync(tmpDir, { recursive: true, force: true }));
+
+  it('exits cleanly on empty stdin', () => {
+    const r = spawnSync(process.execPath, [HOOK], {
+      input: '',
+      encoding: 'utf-8',
+      timeout: 10000,
+      stdio: ['pipe', 'pipe', 'pipe'],
+    });
+    expect(r.status).toBe(0);
+    expect(r.stdout.trim()).toBe('');
+  });
+
+  it('exits cleanly on invalid JSON stdin', () => {
+    const r = spawnSync(process.execPath, [HOOK], {
+      input: 'not json',
+      encoding: 'utf-8',
+      timeout: 10000,
+      stdio: ['pipe', 'pipe', 'pipe'],
+    });
+    expect(r.status).toBe(0);
+    expect(r.stdout.trim()).toBe('');
+  });
+
+  it('ignores non-PostToolUse events', () => {
+    const r = runHook(HOOK, {
+      hook_event_name: 'PreToolUse',
+      tool_name: 'Grep',
+      tool_input: { pattern: 'validateUser' },
+      cwd: tmpDir,
+    });
+    expect(r.status).toBe(0);
+    expect(r.stdout.trim()).toBe('');
+  });
+
+  it('produces no output when cwd is relative', () => {
+    const r = runHook(HOOK, {
+      hook_event_name: 'PostToolUse',
+      tool_name: 'Grep',
+      tool_input: { pattern: 'validateUser' },
+      cwd: 'relative/path',
+    });
+    expect(r.status).toBe(0);
+    expect(r.stdout.trim()).toBe('');
+  });
+
+  it('produces no output when cwd has no .gitnexus index', () => {
+    const r = runHook(HOOK, {
+      hook_event_name: 'PostToolUse',
+      tool_name: 'Grep',
+      tool_input: { pattern: 'validateUser' },
+      cwd: tmpDir,
+    });
+    expect(r.status).toBe(0);
+    expect(r.stdout.trim()).toBe('');
+  });
+
+  it('produces no output for unmatched tools or Execute without rg/grep', () => {
+    for (const input of [
+      { tool_name: 'MadeUpTool', tool_input: { foo: 'bar' } },
+      { tool_name: 'Execute', tool_input: { command: 'ls -la' } },
+      { tool_name: 'Grep', tool_input: { pattern: 'is' } }, // < 3 chars
+    ]) {
+      const r = runHook(HOOK, { hook_event_name: 'PostToolUse', cwd: tmpDir, ...input });
+      expect(r.status).toBe(0);
+      expect(r.stdout.trim()).toBe('');
+    }
+  });
+});
+
+// ─── Behavior: happy path (augment via a fake gitnexus on PATH) ─────
+
+describe('Factory hook behavior — augment', () => {
+  let repoDir: string;
+  let binDir: string;
+
+  beforeAll(() => {
+    repoDir = fs.mkdtempSync(path.join(os.tmpdir(), 'gitnexus-factory-repo-'));
+    // Bare .gitnexus/ (no registry.json/repos) → treated as a repo index; no
+    // `lbug` file → the DB-owner probe short-circuits false and augment runs.
+    fs.mkdirSync(path.join(repoDir, '.gitnexus'), { recursive: true });
+    binDir = createHookToolDir({ gitnexusStderr: '[GitNexus] graph context for validateUser' });
+  });
+  afterAll(() => {
+    fs.rmSync(repoDir, { recursive: true, force: true });
+    fs.rmSync(binDir, { recursive: true, force: true });
+  });
+
+  it('emits augment stderr as additionalContext for a Grep search', () => {
+    const r = runHook(
+      HOOK,
+      {
+        hook_event_name: 'PostToolUse',
+        tool_name: 'Grep',
+        tool_input: { pattern: 'validateUser' },
+        cwd: repoDir,
+      },
+      undefined,
+      { env: hookEnv(binDir) },
+    );
+    expect(r.status).toBe(0);
+    const out = parseHookOutput(r.stdout);
+    expect(out?.hookEventName).toBe('PostToolUse');
+    expect(out?.additionalContext).toContain('graph context for validateUser');
+  });
+});
+
+// ─── Behavior: fan-out guard skips when all slots are held ──────────
+
+describe('Factory hook behavior — augment fan-out guard', () => {
+  it('exits silently when all MAX_INFLIGHT slots hold live pids', async () => {
+    const repoDir = fs.mkdtempSync(path.join(os.tmpdir(), 'gitnexus-factory-slots-'));
+    const lockDir = path.join(repoDir, '.gitnexus', '.hook-locks');
+    fs.mkdirSync(lockDir, { recursive: true });
+    const binDir = createHookToolDir({ gitnexusStderr: 'should never be emitted' });
+
+    const { spawn } = await import('child_process');
+    const sleepers = [0, 1, 2].map(() =>
+      spawn(process.execPath, ['-e', 'setTimeout(()=>{},60000)'], { stdio: 'ignore' }),
+    );
+    try {
+      sleepers.forEach((s, i) =>
+        fs.writeFileSync(path.join(lockDir, `slot-${i}.lock`), String(s.pid)),
+      );
+
+      const r = runHook(
+        HOOK,
+        {
+          hook_event_name: 'PostToolUse',
+          tool_name: 'Grep',
+          tool_input: { pattern: 'validateUser' },
+          cwd: repoDir,
+        },
+        undefined,
+        { env: hookEnv(binDir) },
+      );
+
+      expect(r.status).toBe(0);
+      expect(r.stdout.trim()).toBe('');
+    } finally {
+      for (const s of sleepers) {
+        try {
+          s.kill();
+        } catch {
+          /* ignore */
+        }
+      }
+      fs.rmSync(repoDir, { recursive: true, force: true });
+      fs.rmSync(binDir, { recursive: true, force: true });
+    }
+  });
+});