diff --git a/CHANGELOG.md b/CHANGELOG.md
index ee67524..d9afa3c 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,29 @@
 # Changelog
 
+## 0.13.13 (unreleased)
+
+### Fixed — a crashed Windows session no longer locks its node name until reboot
+
+The identity lock records its holder's process start time, so a later start can tell a live holder from an
+unrelated process that reused the holder's PID. On Windows the start time came from `ps`, which does not
+exist there, so no start time was recorded. After a crash or a hard-killed terminal, once Windows reused the
+PID, the name stayed locked (`EIDENTITYLOCK`) for the rest of the boot.
+
+- **Windows start time.** Windows now reads the start time through the system PowerShell, by absolute path,
+  as UTC ISO-8601. The lock writer and a later reader use the same form.
+- **Caching.** Results are cached for 10 s per PID. A daemon checking many node directories held by one
+  process therefore pays one lookup, about 0.45 s on Windows, measured.
+- **Failed lookups.** When the start time cannot be read (no PowerShell, a timeout, access denied), the lock
+  is treated as held, as before, and the process warns once. A failed lookup of the node's own start time is
+  retried at the next acquire instead of being remembered.
+
+Limits:
+
+- A lock written by 0.13.12 or earlier carries no start time, so it can still only be cleared by a reboot or
+  by deleting `~/.sym/nodes/<name>/lock.pid`. Guessing from the file's timestamp was considered and dropped:
+  a clock step could make a live holder look stale, and a live holder must never lose its lock.
+- Locks written from 0.13.13 on are covered.
+
 ## 0.13.12 (2026-10-01)
 
 Fixes from an MMP 2.0 conformance audit of sym-mesh-channel and the SDK it runs, revised after an independent
diff --git a/lib/config.js b/lib/config.js
index 014e95d..be431d4 100644
--- a/lib/config.js
+++ b/lib/config.js
@@ -335,8 +335,8 @@ function bootTimeMs() {
 
 /**
  * The kernel start time of a process, as an opaque stable string
- * (`ps -o lstart=`), or null when it cannot be determined (dead PID,
- * Windows, ps unavailable). Two different processes that reuse the same
+ * (`ps -o lstart=`, or ISO-8601 UTC from PowerShell on Windows), or null
+ * when it cannot be determined (dead PID, ps/PowerShell unavailable, access denied). Two different processes that reuse the same
  * PID number have different start times — this is what lets the identity
  * lock distinguish "our previous holder is still running" from "an
  * unrelated process recycled the holder's PID".
@@ -344,7 +344,7 @@ function bootTimeMs() {
  * @returns {string|null}
  */
 function processStartTime(pid) {
-  if (process.platform === 'win32') return null;
+  if (process.platform === 'win32') return windowsProcessStartTime(pid);
   try {
     const out = execFileSync('ps', ['-p', String(pid), '-o', 'lstart='], {
       encoding: 'utf8',
@@ -357,13 +357,59 @@ function processStartTime(pid) {
   }
 }
 
+/**
+ * Windows has no `ps`. PowerShell reports a process's start time; the UTC ISO-8601 form is stable
+ * across calls and locales, so the lock writer (for itself) and a later reader (for the same PID)
+ * produce the same string. Without it, a Windows lock recorded no start time and a crashed
+ * holder's recycled PID kept the name locked until reboot.
+ *
+ * Failure (no PowerShell, a timeout, access denied for another user's or a protected process)
+ * returns null, which every reader treats as "held": the safe direction, and the pre-0.13.13
+ * behaviour. A one-time warning says so. Results are cached briefly per PID, because a daemon
+ * checks every node directory's lock at start and many of them share one holder process.
+ * @param {number} pid
+ * @returns {string|null}
+ */
+function windowsProcessStartTime(pid) {
+  if (!Number.isInteger(pid) || pid <= 0 || pid > 0xffffffff) return null;
+  const cached = _winStartCache.get(pid);
+  if (cached && Date.now() - cached.at < WIN_START_CACHE_MS) return cached.value;
+  let value = null;
+  try {
+    const out = execFileSync(windowsPowerShellPath(), [
+      '-NoProfile', '-NonInteractive', '-Command',
+      `(Get-Process -Id ${pid} -ErrorAction Stop).StartTime.ToUniversalTime().ToString('o')`,
+    ], { encoding: 'utf8', timeout: 5000, windowsHide: true }).trim();
+    value = /^\d{4}-\d{2}-\d{2}T[\d:.]+Z$/.test(out) ? out : null;
+  } catch {
+    value = null;
+  }
+  if (value === null && !_winStartWarned) {
+    _winStartWarned = true;
+    process.emitWarning(`SYM identity lock: could not read the start time of process ${pid}; ` +
+      'a lock held by that PID is treated as live (delete ~/.sym/nodes/<name>/lock.pid if its holder is gone).');
+  }
+  _winStartCache.set(pid, { value, at: Date.now() });
+  return value;
+}
+const WIN_START_CACHE_MS = 10000;
+const _winStartCache = new Map();
+let _winStartWarned = false;
+
+/** The system PowerShell by absolute path, never whatever `powershell.exe` the search path finds first. */
+function windowsPowerShellPath() {
+  const root = process.env.SystemRoot || process.env.windir || 'C:\\Windows';
+  return path.join(root, 'System32', 'WindowsPowerShell', 'v1.0', 'powershell.exe');
+}
+
 let _selfStartTime = null;
 let _selfStartTimeResolved = false;
 /** processStartTime(process.pid), computed once per process. */
 function selfStartTime() {
   if (!_selfStartTimeResolved) {
     _selfStartTime = processStartTime(process.pid);
-    _selfStartTimeResolved = true;
+    // A failed lookup (a transient timeout) is not cached: the next acquire tries again.
+    _selfStartTimeResolved = _selfStartTime !== null;
   }
   return _selfStartTime;
 }
@@ -639,6 +685,8 @@ module.exports = {
   normalizeMdnsHostname,
   pidIsAlive,
   processStartTime,
+  /** Test hook: forget cached Windows start times, so a test reaches PowerShell on every call. */
+  _clearProcessStartTimeCache: () => _winStartCache.clear(),
   readLockFile,
   lockIsHeldByLiveProcess,
   lockHolderPid,
diff --git a/tests/_isolate-home.js b/tests/_isolate-home.js
index 6dfa4f5..1fe53c0 100644
--- a/tests/_isolate-home.js
+++ b/tests/_isolate-home.js
@@ -23,6 +23,9 @@ const path = require('path');
 
 const sandbox = fs.mkdtempSync(path.join(os.tmpdir(), 'sym-test-home-'));
 process.env.HOME = sandbox;
+// os.homedir() reads USERPROFILE on Windows, not HOME: without this, Windows runs wrote into the
+// real ~/.sym and the ask tests read the user's real mesh memory.
+process.env.USERPROFILE = sandbox;
 
 process.once('exit', () => {
   try {
diff --git a/tests/ask.test.js b/tests/ask.test.js
index a24d86b..e7270ba 100644
--- a/tests/ask.test.js
+++ b/tests/ask.test.js
@@ -1,5 +1,7 @@
 'use strict';
 
+require('./_isolate-home'); // sandbox HOME/USERPROFILE before anything reads os.homedir()
+
 // `sym ask` — ask the whole mesh one question, get one answer.
 //
 // These tests run the CLI offline: no daemon, no LLM provider (env cleared),
@@ -18,7 +20,8 @@ const CLI = path.join(__dirname, '..', 'bin', 'sym.js');
 
 // Run `sym ask` with a throwaway mesh home and no LLM provider configured.
 function runAsk(homeDir, argv) {
-  const env = { ...process.env, HOME: homeDir };
+  // USERPROFILE too: os.homedir() reads it on Windows, where HOME alone left the child on the real profile.
+  const env = { ...process.env, HOME: homeDir, USERPROFILE: homeDir };
   // Force the no-provider path so the test is hermetic and free.
   for (const k of ['OPENAI_API_KEY', 'ANTHROPIC_API_KEY', 'SYM_LLM_API_KEY', 'SYM_LLM_PROVIDER', 'CLAUDE_AGENT_MODEL']) {
     delete env[k];
diff --git a/tests/config.test.js b/tests/config.test.js
index 676972f..a245107 100644
--- a/tests/config.test.js
+++ b/tests/config.test.js
@@ -12,7 +12,7 @@ const {
   SYM_DIR, NODES_DIR, ensureDir, nodeDir,
   uuidv7, validateName, generateSigningKeyPair, loadOrCreateIdentity,
   normalizeMdnsHostname, pidIsAlive, lockHolderPid, log,
-  acquireIdentityLock, readLockFile, processStartTime,
+  acquireIdentityLock, readLockFile, processStartTime, _clearProcessStartTimeCache,
 } = require('../lib/config');
 
 describe('uuidv7', () => {
@@ -331,6 +331,31 @@ describe('acquireIdentityLock', () => {
     release();
   });
 
+  it('keeps a lock whose live holder\'s recorded start time matches (a live holder is never reclaimed)', () => {
+    const name = mkName();
+    const start = processStartTime(liveChild.pid);
+    assert.ok(start, 'precondition: this platform can read a process start time');
+    writeLock(name, `${liveChild.pid}\n${JSON.stringify({ start, createdAt: Date.now() })}\n`);
+    assert.throws(() => acquireIdentityLock(name), (e) => e.code === 'EIDENTITYLOCK' && e.holderPid === liveChild.pid);
+  });
+
+  it('on Windows, a process start time is read and is stable', { skip: process.platform !== 'win32' }, () => {
+    _clearProcessStartTimeCache();
+    const a = processStartTime(process.pid);
+    assert.match(String(a), /^\d{4}-\d{2}-\d{2}T[\d:.]+Z$/, 'UTC ISO-8601 from PowerShell');
+    _clearProcessStartTimeCache(); // a second real PowerShell call, not the cache
+    assert.strictEqual(processStartTime(process.pid), a, 'same process, same string');
+    assert.notStrictEqual(processStartTime(liveChild.pid), a, 'a different process differs');
+  });
+
+  it('on Windows, a lock recorded with a recycled PID\'s old start time is reclaimed', { skip: process.platform !== 'win32' }, () => {
+    const name = mkName();
+    writeLock(name, `${liveChild.pid}\n{"start":"2004-01-01T00:00:00.0000000Z","createdAt":1}\n`);
+    const release = acquireIdentityLock(name);
+    assert.strictEqual(readLockFile(lockPathOf(name)).pid, process.pid);
+    release();
+  });
+
   it('reclaims an aged-out corrupt lockfile but respects a fresh one', () => {
     const name = mkName();
     writeLock(name, 'garbage');
diff --git a/tests/daemon-relay-only.test.js b/tests/daemon-relay-only.test.js
index 3421697..b7c6ca0 100644
--- a/tests/daemon-relay-only.test.js
+++ b/tests/daemon-relay-only.test.js
@@ -20,7 +20,7 @@ test('SYM_RELAY_ONLY=1: LAN discovery off, relay-auth still sent', async () => {
   wss.on('connection', (ws) => ws.on('message', (m) => { const f = JSON.parse(String(m)); if (f.type === 'relay-auth') auths.push(f); }));
   const relayUrl = `ws://127.0.0.1:${wss.address().port}`;
   const daemon = spawn(process.execPath, [path.join(__dirname, '..', 'bin', 'sym-daemon.js')], {
-    env: { ...process.env, HOME: home, SYM_SOCKET: path.join(home, 'd.sock'), SYM_NODE_NAME: 'relay-only-test',
+    env: { ...process.env, HOME: home, USERPROFILE: home, SYM_SOCKET: path.join(home, 'd.sock'), SYM_NODE_NAME: 'relay-only-test',
       SYM_ROOM: 'relay-only-room', SYM_RELAY_ONLY: '1', SYM_RELAY_URL: relayUrl, SYM_RELAY_TOKEN: 'x'.repeat(32) },
     stdio: ['ignore', 'pipe', 'pipe'],
   });
diff --git a/tests/discovery.test.js b/tests/discovery.test.js
index 34f426e..4347452 100644
--- a/tests/discovery.test.js
+++ b/tests/discovery.test.js
@@ -9,6 +9,7 @@ const os = require('node:os');
 const path = require('node:path');
 const realHome = os.homedir();
 process.env.HOME = fs.mkdtempSync(path.join(os.tmpdir(), 'sym-discovery-home-'));
+process.env.USERPROFILE = process.env.HOME; // os.homedir() reads USERPROFILE on Windows
 
 const { describe, it } = require('node:test');
 const assert = require('node:assert');
@@ -145,7 +146,7 @@ describe('loopback self-clean on abrupt exit', () => {
       process.exit(0);
     `;
     const r = spawnSync(process.execPath, ['-e', src], {
-      env: { ...process.env, HOME: tmpHome },
+      env: { ...process.env, HOME: tmpHome, USERPROFILE: tmpHome },
       encoding: 'utf8',
     });
 
diff --git a/tests/identity-halt.test.js b/tests/identity-halt.test.js
index b6425fa..f3c86a3 100644
--- a/tests/identity-halt.test.js
+++ b/tests/identity-halt.test.js
@@ -1,5 +1,7 @@
 'use strict';
 
+require('./_isolate-home'); // sandbox HOME/USERPROFILE before anything reads os.homedir()
+
 /**
  * B-3 / AC-3.2 — the system refuses to start rather than replace an identity.
  *
diff --git a/tests/integration/e2e-admission.js b/tests/integration/e2e-admission.js
index 47e0150..e715327 100644
--- a/tests/integration/e2e-admission.js
+++ b/tests/integration/e2e-admission.js
@@ -1,5 +1,7 @@
 'use strict';
 
+require('../_isolate-home'); // sandbox HOME/USERPROFILE: node state must never land in the real ~/.sym
+
 /**
  * End-to-end Admission Attestation — the gate attaches a signed attestation to the
  * remix it stores (MMP admission-attestation layer, Phase C).
diff --git a/tests/integration/e2e-attestation-gossip.js b/tests/integration/e2e-attestation-gossip.js
index 9c5c23e..878885e 100644
--- a/tests/integration/e2e-attestation-gossip.js
+++ b/tests/integration/e2e-attestation-gossip.js
@@ -1,5 +1,7 @@
 'use strict';
 
+require('../_isolate-home'); // sandbox HOME/USERPROFILE: node state must never land in the real ~/.sym
+
 /**
  * End-to-end Admission Attestation gossip (Phase D2).
  *
diff --git a/tests/integration/e2e-checkpoint-witness.js b/tests/integration/e2e-checkpoint-witness.js
index b9b2e8d..5a3ddfd 100644
--- a/tests/integration/e2e-checkpoint-witness.js
+++ b/tests/integration/e2e-checkpoint-witness.js
@@ -1,5 +1,7 @@
 'use strict';
 
+require('../_isolate-home'); // sandbox HOME/USERPROFILE: node state must never land in the real ~/.sym
+
 /**
  * End-to-end checkpoint + witness cycle (Phase D3).
  *
diff --git a/tests/integration/e2e-cmb-path.js b/tests/integration/e2e-cmb-path.js
index 1313254..d925450 100644
--- a/tests/integration/e2e-cmb-path.js
+++ b/tests/integration/e2e-cmb-path.js
@@ -1,5 +1,7 @@
 'use strict';
 
+require('../_isolate-home'); // sandbox HOME/USERPROFILE: node state must never land in the real ~/.sym
+
 /**
  * End-to-end CMB path integration test — MMP §4.2 wire frame, §4.4.4
  * targeted routing envelope, §9.2 receiver-autonomous SVAF evaluation,
diff --git a/tests/integration/e2e-payload-receive.js b/tests/integration/e2e-payload-receive.js
index 7210a5a..59b39d7 100644
--- a/tests/integration/e2e-payload-receive.js
+++ b/tests/integration/e2e-payload-receive.js
@@ -1,5 +1,7 @@
 'use strict';
 
+require('../_isolate-home'); // sandbox HOME/USERPROFILE: node state must never land in the real ~/.sym
+
 /**
  * End-to-end PAYLOAD receive integration test — the cross-device drop hunt.
  *
diff --git a/tests/p6-legacy-grandfather.test.js b/tests/p6-legacy-grandfather.test.js
index c453db0..38db329 100644
--- a/tests/p6-legacy-grandfather.test.js
+++ b/tests/p6-legacy-grandfather.test.js
@@ -1,5 +1,7 @@
 'use strict';
 
+require('./_isolate-home'); // sandbox HOME/USERPROFILE: node state must never land in the real ~/.sym
+
 /**
  * P-6 — a pre-boundary block is UNATTESTED, not FORGED.
  *
diff --git a/tests/rule-a-collapse.test.js b/tests/rule-a-collapse.test.js
index 981058d..91210a0 100644
--- a/tests/rule-a-collapse.test.js
+++ b/tests/rule-a-collapse.test.js
@@ -1,5 +1,7 @@
 'use strict';
 
+require('./_isolate-home'); // sandbox HOME/USERPROFILE: node state must never land in the real ~/.sym
+
 /**
  * B-2 / AC-2.4 — Rule A and the collapse property.
  *
diff --git a/tests/wire-rejection.test.js b/tests/wire-rejection.test.js
index babe045..5b25ef9 100644
--- a/tests/wire-rejection.test.js
+++ b/tests/wire-rejection.test.js
@@ -9,6 +9,7 @@ const fs = require('node:fs');
 const os = require('node:os');
 const path = require('node:path');
 process.env.HOME = fs.mkdtempSync(path.join(os.tmpdir(), 'sym-wire-rejection-home-'));
+process.env.USERPROFILE = process.env.HOME; // os.homedir() reads USERPROFILE on Windows
 
 const { describe, it } = require('node:test');
 const assert = require('node:assert');