diff --git a/tests/skill/understand/test_cleanup_workdirs.test.mjs b/tests/skill/understand/test_cleanup_workdirs.test.mjs
new file mode 100644
index 00000000..c84a98c8
--- /dev/null
+++ b/tests/skill/understand/test_cleanup_workdirs.test.mjs
@@ -0,0 +1,120 @@
+import { describe, it, expect, afterEach } from 'vitest';
+import {
+  existsSync,
+  mkdtempSync,
+  mkdirSync,
+  readFileSync,
+  readdirSync,
+  rmSync,
+  utimesSync,
+  writeFileSync,
+} from 'node:fs';
+import { tmpdir } from 'node:os';
+import { join, resolve, dirname } from 'node:path';
+import { spawnSync } from 'node:child_process';
+import { fileURLToPath } from 'node:url';
+
+const __dirname = dirname(fileURLToPath(import.meta.url));
+const SCRIPT = resolve(
+  __dirname,
+  '../../../understand-anything-plugin/skills/understand/cleanup-workdirs.mjs',
+);
+const SKILL = resolve(
+  __dirname,
+  '../../../understand-anything-plugin/skills/understand/SKILL.md',
+);
+const NOW_MS = Date.UTC(2026, 4, 29, 12, 0, 0);
+
+function runCleanup(projectRoot, args = []) {
+  return spawnSync('node', [SCRIPT, projectRoot, `--now-ms=${NOW_MS}`, ...args], {
+    encoding: 'utf-8',
+  });
+}
+
+describe('cleanup-workdirs.mjs', () => {
+  let root;
+
+  afterEach(() => {
+    if (root) rmSync(root, { recursive: true, force: true });
+    root = undefined;
+  });
+
+  it('moves fresh intermediate and tmp directories into timestamped trash', () => {
+    root = mkdtempSync(join(tmpdir(), 'ua-cleanup-'));
+    const stateDir = join(root, '.understand-anything');
+    mkdirSync(join(stateDir, 'intermediate', 'nested'), { recursive: true });
+    mkdirSync(join(stateDir, 'tmp'), { recursive: true });
+    writeFileSync(join(stateDir, 'intermediate', 'nested', 'graph.json'), '{"ok":true}');
+    writeFileSync(join(stateDir, 'tmp', 'validate.cjs'), 'console.log("ok");');
+
+    const result = runCleanup(root);
+
+    expect(result.status).toBe(0);
+    expect(result.stdout).toMatch(/moved intermediate, tmp/);
+    expect(existsSync(join(stateDir, 'intermediate'))).toBe(false);
+    expect(existsSync(join(stateDir, 'tmp'))).toBe(false);
+
+    const trashDirs = readdirSync(stateDir).filter((name) => name.startsWith('.trash-'));
+    expect(trashDirs).toHaveLength(1);
+    const trashDir = join(stateDir, trashDirs[0]);
+
+    expect(readFileSync(join(trashDir, 'intermediate', 'nested', 'graph.json'), 'utf-8'))
+      .toBe('{"ok":true}');
+    expect(readFileSync(join(trashDir, 'tmp', 'validate.cjs'), 'utf-8'))
+      .toBe('console.log("ok");');
+  });
+
+  it('preserves scan-result.json for future incremental runs', () => {
+    root = mkdtempSync(join(tmpdir(), 'ua-cleanup-scan-result-'));
+    const stateDir = join(root, '.understand-anything');
+    mkdirSync(join(stateDir, 'intermediate'), { recursive: true });
+    writeFileSync(join(stateDir, 'intermediate', 'scan-result.json'), '{"files":[]}');
+    writeFileSync(join(stateDir, 'intermediate', 'assembled-graph.json'), '{"nodes":[]}');
+
+    const result = runCleanup(root);
+
+    expect(result.status).toBe(0);
+    expect(readFileSync(join(stateDir, 'intermediate', 'scan-result.json'), 'utf-8'))
+      .toBe('{"files":[]}');
+    expect(existsSync(join(stateDir, 'intermediate', 'assembled-graph.json'))).toBe(false);
+
+    const trashDirs = readdirSync(stateDir).filter((name) => name.startsWith('.trash-'));
+    expect(trashDirs).toHaveLength(1);
+    expect(readFileSync(
+      join(stateDir, trashDirs[0], 'intermediate', 'assembled-graph.json'),
+      'utf-8',
+    )).toBe('{"nodes":[]}');
+  });
+
+  it('purges expired trash while keeping recent trash', () => {
+    root = mkdtempSync(join(tmpdir(), 'ua-cleanup-purge-'));
+    const stateDir = join(root, '.understand-anything');
+    const oldTrash = join(stateDir, '.trash-old');
+    const recentTrash = join(stateDir, '.trash-recent');
+    mkdirSync(oldTrash, { recursive: true });
+    mkdirSync(recentTrash, { recursive: true });
+    writeFileSync(join(oldTrash, 'old.txt'), 'old');
+    writeFileSync(join(recentTrash, 'recent.txt'), 'recent');
+
+    const oldDate = new Date(NOW_MS - 8 * 24 * 60 * 60 * 1000);
+    const recentDate = new Date(NOW_MS - 6 * 24 * 60 * 60 * 1000);
+    utimesSync(oldTrash, oldDate, oldDate);
+    utimesSync(recentTrash, recentDate, recentDate);
+
+    const result = runCleanup(root, ['--retention-days=7']);
+
+    expect(result.status).toBe(0);
+    expect(existsSync(oldTrash)).toBe(false);
+    expect(existsSync(recentTrash)).toBe(true);
+    expect(result.stdout).toMatch(/purged 1 expired trash directory/);
+  });
+
+  it('documents Phase 7 cleanup without immediate recursive deletion of fresh work dirs', () => {
+    const skill = readFileSync(SKILL, 'utf-8');
+
+    expect(skill).toContain('cleanup-workdirs.mjs');
+    expect(skill).not.toMatch(
+      /rm\s+-rf\s+\$PROJECT_ROOT\/\.understand-anything\/(?:intermediate|tmp)/,
+    );
+  });
+});
diff --git a/understand-anything-plugin/skills/understand/SKILL.md b/understand-anything-plugin/skills/understand/SKILL.md
index 10bf9ccb..dc1ffc02 100644
--- a/understand-anything-plugin/skills/understand/SKILL.md
+++ b/understand-anything-plugin/skills/understand/SKILL.md
@@ -776,21 +776,11 @@ Report to the user: `[Phase 7/7] Saving knowledge graph...`
    }
    ```
 
-4. Clean up intermediate files, **preserving `scan-result.json`** so future incremental runs can skip Phase 1 SCAN (see issue #293). We `mv` scratch dirs into a timestamped `.trash-*` instead of `rm -rf`ing them directly — this avoids tripping destructive-action gates on hardened hosts (e.g. freshness-window checks) that flag deleting directories created moments earlier (see issue #301). The delayed-purge step in Phase 0 reclaims the space once the trash is older than 7 days.
+4. Move intermediate files into reversible trash, **preserving `scan-result.json`** so future incremental runs can skip Phase 1 SCAN (see issue #293), and purge old trash:
    ```bash
-   # Preserve scan-result.json — Phase 1's deterministic file inventory.
-   # Future incremental runs (Phase 2 compute-batches.mjs --changed-files=…)
-   # need this inventory; without it, Phase 1 must re-dispatch and pay ~157k
-   # tokens / ~158s per incremental run.
-   TRASH="$PROJECT_ROOT/.understand-anything/.trash-$(date +%s)"
-   mkdir -p "$TRASH"
-   INTER="$PROJECT_ROOT/.understand-anything/intermediate"
-   if [ -d "$INTER" ]; then
-     # Move every entry except scan-result.json into the trash dir.
-     find "$INTER" -mindepth 1 -maxdepth 1 -not -name 'scan-result.json' -exec mv {} "$TRASH/" \; 2>/dev/null || true
-   fi
-   mv "$PROJECT_ROOT/.understand-anything/tmp" "$TRASH/" 2>/dev/null || true
+   node <SKILL_DIR>/cleanup-workdirs.mjs $PROJECT_ROOT
    ```
+   The cleanup script keeps `.understand-anything/intermediate/scan-result.json` in place, renames the rest of the fresh `intermediate/` contents plus `tmp/` into a timestamped `.understand-anything/.trash-*` directory to avoid tripping destructive-action gates on just-created paths (see issue #301), then purges only trash directories older than 7 days.
 
 5. Report a summary to the user containing:
    - Project name and description
diff --git a/understand-anything-plugin/skills/understand/cleanup-workdirs.mjs b/understand-anything-plugin/skills/understand/cleanup-workdirs.mjs
new file mode 100644
index 00000000..3bdce6d4
--- /dev/null
+++ b/understand-anything-plugin/skills/understand/cleanup-workdirs.mjs
@@ -0,0 +1,162 @@
+#!/usr/bin/env node
+/**
+ * cleanup-workdirs.mjs - Phase 7 cleanup for /understand
+ *
+ * Moves fresh per-run work directories into a timestamped trash directory
+ * instead of deleting them in place. Old trash directories are purged after a
+ * retention window, so hardened hosts do not need to approve immediate
+ * recursive deletion of artifacts that were created moments earlier.
+ *
+ * Usage:
+ *   node cleanup-workdirs.mjs <project-root> [--retention-days=7]
+ *
+ * Writes:
+ *   <project-root>/.understand-anything/.trash-<timestamp>-<pid>/
+ */
+
+import {
+  existsSync,
+  mkdirSync,
+  readdirSync,
+  renameSync,
+  rmSync,
+  rmdirSync,
+  statSync,
+} from 'node:fs';
+import { basename, join, resolve } from 'node:path';
+
+const MS_PER_DAY = 24 * 60 * 60 * 1000;
+const DEFAULT_RETENTION_DAYS = 7;
+const WORK_DIRS = ['intermediate', 'tmp'];
+
+function parseArgs(argv) {
+  const [, , projectRootArg, ...rest] = argv;
+  if (!projectRootArg) {
+    throw new Error('Usage: node cleanup-workdirs.mjs <project-root> [--retention-days=7]');
+  }
+
+  const options = {
+    projectRoot: resolve(projectRootArg),
+    retentionDays: DEFAULT_RETENTION_DAYS,
+    nowMs: Date.now(),
+  };
+
+  for (const arg of rest) {
+    if (arg.startsWith('--retention-days=')) {
+      const value = Number(arg.slice('--retention-days='.length));
+      if (!Number.isFinite(value) || value < 0) {
+        throw new Error(`Invalid --retention-days value: ${arg}`);
+      }
+      options.retentionDays = value;
+    } else if (arg.startsWith('--now-ms=')) {
+      // Test-only determinism hook. Normal skill usage should not pass this.
+      const value = Number(arg.slice('--now-ms='.length));
+      if (!Number.isFinite(value)) {
+        throw new Error(`Invalid --now-ms value: ${arg}`);
+      }
+      options.nowMs = value;
+    } else {
+      throw new Error(`Unknown argument: ${arg}`);
+    }
+  }
+
+  return options;
+}
+
+function timestampForPath(nowMs) {
+  return new Date(nowMs)
+    .toISOString()
+    .replace(/[-:]/g, '')
+    .replace(/[.]/g, '')
+    .replace('T', '-');
+}
+
+function purgeExpiredTrash(stateDir, nowMs, retentionDays) {
+  if (!existsSync(stateDir)) return [];
+
+  const cutoffMs = nowMs - retentionDays * MS_PER_DAY;
+  const purged = [];
+
+  for (const entry of readdirSync(stateDir, { withFileTypes: true })) {
+    if (!entry.isDirectory() || !entry.name.startsWith('.trash-')) continue;
+
+    const fullPath = join(stateDir, entry.name);
+    const stat = statSync(fullPath);
+    if (stat.mtimeMs > cutoffMs) continue;
+
+    rmSync(fullPath, { recursive: true, force: true });
+    purged.push(entry.name);
+  }
+
+  return purged;
+}
+
+function moveWorkDirs(stateDir, nowMs) {
+  const moved = [];
+  let trashDir = null;
+
+  for (const name of WORK_DIRS) {
+    const source = join(stateDir, name);
+    if (!existsSync(source)) continue;
+
+    if (name === 'intermediate') {
+      const entries = readdirSync(source, { withFileTypes: true })
+        .filter((entry) => entry.name !== 'scan-result.json');
+      if (entries.length === 0) continue;
+
+      if (!trashDir) {
+        trashDir = join(stateDir, `.trash-${timestampForPath(nowMs)}-${process.pid}`);
+        mkdirSync(trashDir, { recursive: true });
+      }
+
+      const destination = join(trashDir, basename(source));
+      mkdirSync(destination, { recursive: true });
+      for (const entry of entries) {
+        renameSync(join(source, entry.name), join(destination, entry.name));
+      }
+      try {
+        rmdirSync(source);
+      } catch {
+        // Keep intermediate/ when scan-result.json remains for incremental runs.
+      }
+      moved.push({ name, destination });
+      continue;
+    }
+
+    if (!trashDir) {
+      trashDir = join(stateDir, `.trash-${timestampForPath(nowMs)}-${process.pid}`);
+      mkdirSync(trashDir, { recursive: true });
+    }
+
+    const destination = join(trashDir, basename(source));
+    renameSync(source, destination);
+    moved.push({ name, destination });
+  }
+
+  return { trashDir, moved };
+}
+
+function main() {
+  const { projectRoot, retentionDays, nowMs } = parseArgs(process.argv);
+  const stateDir = join(projectRoot, '.understand-anything');
+
+  mkdirSync(stateDir, { recursive: true });
+
+  const purged = purgeExpiredTrash(stateDir, nowMs, retentionDays);
+  const { trashDir, moved } = moveWorkDirs(stateDir, nowMs);
+
+  const movedNames = moved.map((item) => item.name).join(', ') || 'none';
+  const trashMessage = trashDir ? ` into ${trashDir}` : '';
+  process.stdout.write(
+    `Cleanup complete: moved ${movedNames}${trashMessage}; ` +
+    `purged ${purged.length} expired trash director${purged.length === 1 ? 'y' : 'ies'}.\n`,
+  );
+}
+
+try {
+  main();
+} catch (err) {
+  const message = err instanceof Error ? err.message : String(err);
+  process.stderr.write(`Cleanup failed: ${message}\n`);
+  process.exit(1);
+}