diff --git a/.claude/commands/orchestrate.md b/.claude/commands/orchestrate.md
index d9f1f56c3..828f27bcd 100644
--- a/.claude/commands/orchestrate.md
+++ b/.claude/commands/orchestrate.md
@@ -1110,9 +1110,11 @@ commandmatedev verify show "$RUN_ID" --json | jq '.gates[] | select(.status != "
   - 別プロセスの TCP listener（`-`）
   - ワーカーの最初のツール呼び出しより前の時刻が名前に入った `~/.commandmate-test-<ms>`（`+`）
 
-  並行するワーカーのテストが一時的に作る `~/.commandmate-demo-vitest-<pid>`（`+`）も、このワーカー起因ではないことがある
-  （2026-09-28、2 本を並行した run で、互いのテストが作ったものを `env-clean` が違反に数えた。道具の側は #2954 で直す）。
-  直るまでは、`commandmatedev verify "$WT" --task "$TASK_ID" --gates env-clean` を再実行して、その項目が消えていれば合格として扱う。
+  `~/.commandmate-demo-vitest-<pid>`（`+`）は、#3479 より前のコードの `env-scripts.test.ts` だけが作る
+  （#3479 から作業場所は OS の一時ディレクトリで、`$HOME` には作らない）。base が #3479 より古いブランチの
+  テストが並行で動いていると現れ、このワーカー起因ではないことがある（2026-09-28 の 2 本並行の run。別の worktree の
+  生きたテストのものは #2954 で `other` に分かれる）。`[unattributed]` で残ったら、
+  `commandmatedev verify "$WT" --task "$TASK_ID" --gates env-clean` を再実行して、その項目が消えていれば合格として扱う。
 
   帰属は次の 3 つで確かめる:
   - ワーカーが実行したコマンド: `capture --prompts --limit 100` の `Run this command?` と、そこに書かれた `start with '<cmd>'`
@@ -1127,7 +1129,8 @@ commandmatedev verify show "$RUN_ID" --json | jq '.gates[] | select(.status != "
 **合図の前に始まった検証**（Antigravity 担当。3-3 の「完了の合図」）で `env-clean` だけが落ちたとき:
 
 - 違反は、ワーカー自身がまだ動かしていたもの（バックグラウンドのテスト実行の listener `[self]`、
-  テストが作って後で消す `~/.commandmate-demo-vitest-*` など）であることが多い
+  テストが作って後で消す `$HOME` 直下のエントリなど）であることが多い。`~/.commandmate-demo-vitest-*` は
+  #3479 から作られない（#3395 はこの形で、ワーカー自身のまだ動いていたテストが作ったものだった）
 - 合図の後に `commandmatedev verify "$WT" --task "$TASK_ID" --gates env-clean` を再実行する
   （`work-evidence` と `scope` も一緒に走る）
 - 再実行が PASS で、かつ 3-3 の確認で「最後のコミットが検証の開始より前・作業ツリーに変更なし」なら、合格として扱う。
diff --git a/changelog.d/3479.md b/changelog.d/3479.md
new file mode 100644
index 000000000..25e0089cf
--- /dev/null
+++ b/changelog.d/3479.md
@@ -0,0 +1,2 @@
+<!-- ### Fixed -->
+- **fix(verify): demo-video の env-scripts テストが作業場所を実の `$HOME` ではなく OS の一時ディレクトリに作るようにした** (#3479): `~/.commandmate-demo-vitest-<pid>` が実行中ずっと `$HOME` 直下にあり、同じマシンのどの契約検証の `env-clean` にも `+` として見えていた（#3395 では、検証の時点でまだ動いていたワーカー自身のテストのものが `[unattributed]` で不合格になった）。子の `$HOME` は作業場所そのもので、スタブのサーバーは DB パスの検証を通らないため、本番の制限（`validateDbPath`）は変えずに一時ディレクトリへ移した。テストの実行中・実行後に `$HOME` へ何も作らない
diff --git a/src/lib/verification/env-clean-gate.ts b/src/lib/verification/env-clean-gate.ts
index fdb883480..f259676ba 100644
--- a/src/lib/verification/env-clean-gate.ts
+++ b/src/lib/verification/env-clean-gate.ts
@@ -225,11 +225,12 @@ export const readLivePidCwd: PidCwdResolver = (pid) => {
 };
 
 /**
- * `tests/unit/skills/demo-video/env-scripts.test.ts` creates
- * `~/.commandmate-demo-vitest-<pid>` for the length of its run — in the real
- * `$HOME`, because `env-up.sh` refuses `/tmp` and `/var` (#2954). The name
- * carries the pid of the test process that made it, which is the one `$HOME`
- * entry whose owner can be established.
+ * `tests/unit/skills/demo-video/env-scripts.test.ts` created
+ * `~/.commandmate-demo-vitest-<pid>` for the length of its run, in the real
+ * `$HOME` (#2954). Since #3479 it makes the dir under the OS temp dir instead;
+ * this stays for checkouts that predate that. The name carries the pid of the
+ * test process that made it, which is the one `$HOME` entry whose owner can be
+ * established.
  */
 const DEMO_VITEST_HOME_ENTRY = /^\.commandmate-demo-vitest-([1-9]\d*)$/;
 
diff --git a/tests/unit/skills/demo-video/env-scripts.test.ts b/tests/unit/skills/demo-video/env-scripts.test.ts
index 901aecad2..ac9036050 100644
--- a/tests/unit/skills/demo-video/env-scripts.test.ts
+++ b/tests/unit/skills/demo-video/env-scripts.test.ts
@@ -16,6 +16,7 @@ import os from 'node:os';
 import path from 'node:path';
 import { afterAll, afterEach, beforeAll, describe, expect, it } from 'vitest';
 import { removeTempDir } from '@tests/helpers/temp-dir';
+import { isPathWithin } from '@/config/system-directories';
 import { CLI_TOOL_IDS } from '@/lib/cli-tools/types';
 import { claudeProjectSlug } from '@/lib/hooks/sources/claude/transcript';
 import { findCodexRolloutPath } from '@/lib/hooks/sources/codex/history';
@@ -27,15 +28,22 @@ const SCRIPTS = path.join(REPO_ROOT, '.claude/skills/demo-video/scripts');
 const ENV_UP = path.join(SCRIPTS, 'env-up.sh');
 const ENV_DOWN = path.join(SCRIPTS, 'env-down.sh');
 
-// env-up refuses a state dir outside $HOME (validateDbPath rejects /tmp and
-// /var as system directories), so the scratch dir has to live under $HOME.
-//
-// Issue #2380: env-up ALSO refuses to run with $HOME set to the login home,
-// because it plants fake agent transcripts under `~/.claude/projects` and
+// Issue #2380: env-up refuses to run with $HOME set to the login home, because
+// it plants fake agent transcripts under `~/.claude/projects` and
 // `~/.codex/sessions`. So the scratch dir doubles as the HOME every script
 // here runs with: SCRATCH_HOME is `$HOME` for the child, and the demo state
 // dir sits inside it the way it would under /Users/Shared/cmdemo-home.
-const SCRATCH_HOME = path.join(os.homedir(), `.commandmate-demo-vitest-${process.pid}`);
+//
+// Issue #3479: it lives under the OS temp dir, NOT the real $HOME. It used to
+// be `~/.commandmate-demo-vitest-<pid>` because env-up requires the state dir
+// to be under `$HOME` and a real demo's validateDbPath rejects /tmp and /var —
+// but the `$HOME` env-up checks is the child's, which is SCRATCH_HOME itself,
+// and the stub server never runs validateDbPath. In the real home the dir was
+// a `$HOME` entry for every env-clean gate on the machine while a run was in
+// flight (#3395 failed on its own still-running test's dir). The physical path
+// (`/private/var/...` on macOS) so `pwd -P` in the scripts agrees with it.
+const SCRATCH_BASE = fs.realpathSync(os.tmpdir());
+const SCRATCH_HOME = path.join(SCRATCH_BASE, `.commandmate-demo-vitest-${process.pid}`);
 const DEMO_HOME = path.join(SCRATCH_HOME, '.commandmate-demo');
 const STATE_FILE = path.join(DEMO_HOME, 'state.env');
 const STUB = path.join(SCRATCH_HOME, 'stub-server.js');
@@ -215,8 +223,9 @@ async function portListening(port: number): Promise<boolean> {
 }
 
 beforeAll(async () => {
-  // Collect dirs left by runs that were killed before afterAll (#3025).
-  sweepStaleScratchDirs(os.homedir());
+  // Collect dirs left by runs that were killed before afterAll (#3025). Only
+  // under the temp dir: this file no longer writes to, or sweeps, the real home.
+  sweepStaleScratchDirs(SCRATCH_BASE);
   TEST_PORT = await reserveDemoPortPair();
   removeTempDir(SCRATCH_HOME);
   fs.mkdirSync(DEMO_HOME, { recursive: true });
@@ -286,11 +295,10 @@ afterEach(() => {
   fs.rmSync(REQUEST_LOG, { force: true });
 });
 
-// The scratch dir has to sit under $HOME (env-up refuses anything else, because
-// validateDbPath rejects /tmp and /var), which makes leaving it behind a leak
-// into a real user's home: one directory per `npm run test:unit`, never
-// collected. afterAll still runs when a test — or beforeAll — fails, and the
-// removal is force/recursive so it cannot throw and mask that failure.
+// Leaving the scratch dir behind is a leak: one directory per
+// `npm run test:unit`, collected only by the next run's sweep. afterAll still
+// runs when a test — or beforeAll — fails, and the removal is force/recursive
+// so it cannot throw and mask that failure.
 // `no-home-leftovers.test.ts` runs this file in a child process and asserts the
 // directory is gone afterwards, so deleting this hook turns that test red.
 afterAll(() => {
@@ -323,6 +331,23 @@ describe('demo port band', () => {
   });
 });
 
+describe('scratch location (Issue #3479)', () => {
+  it('keeps the scratch dir out of the real home, so env-clean never sees it', () => {
+    // A dir under the real $HOME was a `$HOME` entry for every parallel
+    // worktree's env-clean gate, and for this worker's own gate while its tests
+    // were still running (#3395: `.commandmate-demo-vitest-36552 [unattributed]`).
+    expect(isPathWithin(SCRATCH_HOME, os.homedir())).toBe(false);
+    expect(isPathWithin(SCRATCH_HOME, LOGIN_HOME)).toBe(false);
+    // Negative control: the check does see a path that is in the home.
+    expect(isPathWithin(path.join(os.homedir(), '.commandmate-demo-vitest-1'), os.homedir())).toBe(true);
+  });
+
+  it('is still a real directory that env-up accepts as an isolated HOME', () => {
+    expect(fs.statSync(SCRATCH_HOME).isDirectory()).toBe(true);
+    expect(isPathWithin(DEMO_HOME, SCRATCH_HOME)).toBe(true);
+  });
+});
+
 describe('env-up refuses configurations that could reach a live instance', () => {
   it('refuses port 3000', () => {
     const result = run(ENV_UP, [], { ...stubEnv(), CM_DEMO_PORT: '3000' });
diff --git a/tests/unit/skills/demo-video/no-home-leftovers.test.ts b/tests/unit/skills/demo-video/no-home-leftovers.test.ts
index 01826472f..02f35818d 100644
--- a/tests/unit/skills/demo-video/no-home-leftovers.test.ts
+++ b/tests/unit/skills/demo-video/no-home-leftovers.test.ts
@@ -1,16 +1,18 @@
 /**
- * The demo-video env tests must not leave anything in the user's home (#1553).
+ * The demo-video env tests must not leave anything in the user's home (#1553),
+ * and since #3479 must not create anything there at all.
  *
- * `env-scripts.test.ts` has to put its scratch dir under $HOME — env-up.sh
- * refuses anywhere else, because validateDbPath rejects /tmp and /var as system
- * directories. That makes forgetting to remove it a leak into a real home
- * directory: one `.commandmate-demo-vitest-<pid>` per `npm run test:unit`, with
- * nothing to ever collect them. Eight had accumulated before this guard existed.
+ * `env-scripts.test.ts` used to put its scratch dir under $HOME, so forgetting
+ * to remove it was a leak into a real home directory: one
+ * `.commandmate-demo-vitest-<pid>` per `npm run test:unit`. Eight had
+ * accumulated before this guard existed. Even removed on time, the dir was a
+ * `$HOME` entry for every env-clean gate on the machine while the run lasted
+ * (#3479), so it now lives under the OS temp dir.
  *
  * A hook that runs last cannot be observed from inside its own file, so this
- * test runs that file in a child process with `HOME` pointed at a scratch
- * directory and inspects what survives. `os.homedir()` returns `$HOME` on
- * POSIX, so the child's scratch dir lands where this test can see it.
+ * test runs that file in a child process with `HOME` and `TMPDIR` pointed at
+ * scratch directories and inspects what survives in each. `os.homedir()` and
+ * `os.tmpdir()` follow those variables on POSIX.
  *
  * @vitest-environment node
  */
@@ -38,6 +40,8 @@ const TARGET = 'tests/unit/skills/demo-video/env-scripts.test.ts';
 const TEST_NAME = 'refuses to start on top of an existing state file';
 
 const SCRATCH_HOME = fs.mkdtempSync(path.join(os.tmpdir(), 'demo-video-home-'));
+/** The child's `os.tmpdir()`, where its scratch dir is now made (#3479). */
+const SCRATCH_TMP = fs.mkdtempSync(path.join(os.tmpdir(), 'demo-video-tmp-'));
 
 function leftovers(home: string): string[] {
   return fs.readdirSync(home).filter((entry) => entry.startsWith('.commandmate-demo-vitest-'));
@@ -71,6 +75,7 @@ beforeAll(() => {
     env: {
       ...process.env,
       HOME: SCRATCH_HOME,
+      TMPDIR: SCRATCH_TMP,
       NODE_ENV: 'test',
       // Belt: keep the child's summary colourless wherever it runs, so local
       // and CI see the same bytes. Braces: `passedTestCount` strips ANSI anyway,
@@ -84,6 +89,7 @@ beforeAll(() => {
 
 afterAll(() => {
   removeTempDir(SCRATCH_HOME);
+  removeTempDir(SCRATCH_TMP);
 });
 
 describe('env-scripts.test.ts cleans up after itself', () => {
@@ -99,6 +105,19 @@ describe('env-scripts.test.ts cleans up after itself', () => {
     expect(leftovers(SCRATCH_HOME)).toEqual([]);
   });
 
+  it('creates nothing in $HOME at all (#3479)', () => {
+    // Not just "no demo-vitest dir": while the run lasts, anything in the real
+    // home is an entry every parallel worktree's env-clean gate can see.
+    expect(fs.readdirSync(SCRATCH_HOME)).toEqual([]);
+  });
+
+  it('leaves no .commandmate-demo-vitest-* directory behind in its temp dir (#3479)', () => {
+    // The probe case passing proves the scratch dir existed; env-scripts makes
+    // it under `os.tmpdir()`, which the child resolves to SCRATCH_TMP. Its own
+    // 'scratch location' case pins that it is not under the home.
+    expect(leftovers(SCRATCH_TMP)).toEqual([]);
+  });
+
   it('counts the child summary whether or not vitest coloured it', () => {
     // Colour is not reproducible on demand: vitest leaves the summary plain in
     // a local pipe *and* under a pty, and colours it on GitHub Actions. So the
diff --git a/tests/unit/skills/demo-video/stale-scratch.ts b/tests/unit/skills/demo-video/stale-scratch.ts
index f59739222..7c064da50 100644
--- a/tests/unit/skills/demo-video/stale-scratch.ts
+++ b/tests/unit/skills/demo-video/stale-scratch.ts
@@ -1,8 +1,8 @@
 /**
- * Sweeping of `.commandmate-demo-vitest-<pid>` scratch dirs left in $HOME (#3025).
+ * Sweeping of `.commandmate-demo-vitest-<pid>` scratch dirs left behind (#3025).
  *
- * `env-scripts.test.ts` has to create its scratch dir under the real $HOME and
- * removes it in `afterAll`. A killed or timed-out run never reaches `afterAll`,
+ * `env-scripts.test.ts` creates its scratch dir under the OS temp dir (the real
+ * $HOME until #3479) and removes it in `afterAll`. A killed or timed-out run never reaches `afterAll`,
  * so the dir stays behind. The next run collects the ones whose owner is gone.
  */
 import fs from 'node:fs';
@@ -34,7 +34,7 @@ export function isStaleScratchDir(name: string): boolean {
   return pid !== null && !isPidAlive(pid);
 }
 
-/** Remove stale scratch dirs directly under `home`; returns the names removed. */
+/** Remove stale scratch dirs directly under `home` (any base dir); returns the names removed. */
 export function sweepStaleScratchDirs(home: string): string[] {
   const removed: string[] = [];
   for (const entry of fs.readdirSync(home, { withFileTypes: true })) {