fix(store): refuse unmarked targets by default; reclaim only under --reclaim (W-F4 review)

Resolves the review finding on c23a71d7: 'store add' silently deleted a
markerless target directory and reported it as recovered-partial, but the
code cannot distinguish its own interrupted-write debris from content the
operator placed by hand — and the USER root's entire contract is that
tooling never destroys operator content.

- addStoreEntry now throws typed STORE_TARGET_UNMARKED on an unmarked
  target; deletion happens only when the caller passes { reclaim: true }.
- CLI: 'store add' gains --reclaim ('replace an existing UNMARKED target
  directory; refuses without this flag').
- Status renamed recovered-partial -> reclaimed-unmarked so even the
  opted-in path names what it did (fix 2 folded into fix 1).
- Spec: default-refusal test asserts operator content SURVIVES; opt-in
  test asserts replacement; two CLI tests cover exit codes.
- Ordering test (second review round): 'reclaim can never destroy a
  marked, vetted entry' — adds a vetted entry, re-adds with reclaim:true,
  asserts STORE_ALREADY_PRESENT AND the original content + marker survive
  on disk. Pins marker-check-before-reclaim-check against the
  guard-clause-migrates-upward refactor; discrimination proven by
  sabotaging the order (1 failed, exactly this test) and restoring (49/49).
- TOCTOU note added at assertSourceTreeHasNoSymlinks per review (known
  check-then-use window, accepted for a local operator-run CLI).

Gates (settled set, rc-honest): store spec 49/49; package vitest 87 files
/ 1596 tests; package build+lint rc0; root build 25/25 + typecheck 45/45;
prettier --check rc0 on all four touched files.

c23a71d7 remains the reviewed object, untouched.

packages/mosaic/src/cli.ts

@@ -20,6 +20,7 @@ import { registerMissionCommand } from './commands/mission.js';
 import { registerUninstallCommand } from './commands/uninstall.js';
 import { registerRestoreCommand } from './commands/restore.js';
 import { registerSkillCommand } from './commands/skill.js';
+import { registerStoreCommand } from './commands/store.js';
 // prdy is registered via launch.ts
 import { registerLaunchCommands } from './commands/launch.js';
 import { registerLeaseCapabilityProbe } from './commands/lease-activation-probe.js';
@@ -425,6 +426,10 @@ registerRestoreCommand(program);
 
 registerSkillCommand(program);
 
+// ─── store ───────────────────────────────────────────────────────────────────
+
+registerStoreCommand(program);
+
 // ─── telemetry ───────────────────────────────────────────────────────────────
 
 registerTelemetryCommand(program);

packages/mosaic/src/commands/store.spec.ts

@@ -0,0 +1,458 @@
+import { afterEach, beforeEach, describe, expect, it } from 'vitest';
+import { Command } from 'commander';
+import {
+  existsSync,
+  lstatSync,
+  mkdirSync,
+  mkdtempSync,
+  readFileSync,
+  readdirSync,
+  rmSync,
+  symlinkSync,
+  writeFileSync,
+} from 'node:fs';
+import { tmpdir } from 'node:os';
+import { join } from 'node:path';
+import {
+  addStoreEntry,
+  getDefaultStorePaths,
+  listStoreEntries,
+  registerStoreCommand,
+  StoreError,
+  storeKindDir,
+  validateStoreKind,
+  validateStoreName,
+  validateStoreVersion,
+  type StorePaths,
+} from './store.js';
+
+/** Assert a typed StoreError with exactly the expected code. */
+function expectStoreError(run: () => unknown, code: string): void {
+  try {
+    run();
+  } catch (error) {
+    expect(error).toBeInstanceOf(StoreError);
+    expect((error as StoreError).code).toBe(code);
+    return;
+  }
+  throw new Error(`expected StoreError ${code}, but nothing threw`);
+}
+
+describe('vetted user store (W-F4)', () => {
+  let root: string;
+  let paths: StorePaths;
+  let sourceRoot: string;
+
+  beforeEach(() => {
+    root = mkdtempSync(join(tmpdir(), 'mosaic-store-cli-'));
+    paths = { userRoot: join(root, '.mosaic') };
+    sourceRoot = join(root, 'sources');
+    mkdirSync(sourceRoot, { recursive: true });
+  });
+
+  afterEach(() => {
+    rmSync(root, { recursive: true, force: true });
+  });
+
+  function createSource(name: string): string {
+    const dir = join(sourceRoot, name);
+    mkdirSync(dir, { recursive: true });
+    writeFileSync(join(dir, 'SKILL.md'), `# ${name}\n`);
+    return dir;
+  }
+
+  describe('name and version validation (before any filesystem call)', () => {
+    const invalidNames = [
+      '../../etc',
+      '/abs/path',
+      'a/b',
+      String.raw`a\b`,
+      '-rf',
+      '..',
+      'safe.',
+      'space name',
+      'line\nbreak',
+      'escape\u001B[31m',
+    ];
+
+    for (const name of invalidNames) {
+      it(`rejects name ${JSON.stringify(name)}`, () => {
+        expect(() => validateStoreName(name)).toThrow(StoreError);
+      });
+    }
+
+    const invalidVersions = ['', '-1', '1..0', 'a/b', '..', '1.0 beta', '/x'];
+    for (const version of invalidVersions) {
+      it(`rejects version ${JSON.stringify(version)}`, () => {
+        expect(() => validateStoreVersion(version)).toThrow(StoreError);
+      });
+    }
+
+    it('accepts semver-shaped versions including prerelease and build metadata', () => {
+      expect(() => validateStoreVersion('0.1.0-beta.1')).not.toThrow();
+      expect(() => validateStoreVersion('1.2.3+build.7')).not.toThrow();
+    });
+
+    it('rejects plural and unknown kinds', () => {
+      expectStoreError(() => validateStoreKind('plugins'), 'STORE_INVALID_KIND');
+      expectStoreError(() => validateStoreKind('widget'), 'STORE_INVALID_KIND');
+    });
+
+    it('accepts the two spec kinds', () => {
+      expect(() => validateStoreKind('plugin')).not.toThrow();
+      expect(() => validateStoreKind('skill')).not.toThrow();
+    });
+  });
+
+  describe('addStoreEntry', () => {
+    it('copies content into a versioned directory and writes the marker last', () => {
+      const result = addStoreEntry(
+        'skill',
+        'demo',
+        '1.0.0',
+        createSource('demo'),
+        'op',
+        undefined,
+        paths,
+      );
+      expect(result.status).toBe('added');
+      const entryPath = join(paths.userRoot, 'skills', 'demo', '1.0.0');
+      expect(result.entryPath).toBe(entryPath);
+      expect(existsSync(join(entryPath, 'SKILL.md'))).toBe(true);
+      expect(existsSync(join(entryPath, 'store-entry.json'))).toBe(true);
+      const meta = JSON.parse(readFileSync(join(entryPath, 'store-entry.json'), 'utf-8'));
+      expect(meta).toMatchObject({
+        schema: 1,
+        kind: 'skill',
+        name: 'demo',
+        version: '1.0.0',
+        vettedBy: 'op',
+      });
+      expect(typeof meta['vettedAt']).toBe('string');
+    });
+
+    it('writes plugins under plugins/ and skills under skills/', () => {
+      addStoreEntry('plugin', 'alpha', '0.1.0', createSource('alpha'), 'op', undefined, paths);
+      addStoreEntry('skill', 'beta', '2.0.0', createSource('beta'), 'op', undefined, paths);
+      expect(existsSync(join(paths.userRoot, 'plugins', 'alpha', '0.1.0'))).toBe(true);
+      expect(existsSync(join(paths.userRoot, 'skills', 'beta', '2.0.0'))).toBe(true);
+    });
+
+    it('is append-only: an existing version with a marker is refused, not overwritten', () => {
+      const sourceA = createSource('demo');
+      const sourceB = join(sourceRoot, 'demo-other');
+      mkdirSync(sourceB, { recursive: true });
+      writeFileSync(join(sourceB, 'SKILL.md'), '# changed\n');
+      addStoreEntry('skill', 'demo', '1.0.0', sourceA, 'op', undefined, paths);
+      expectStoreError(
+        () => addStoreEntry('skill', 'demo', '1.0.0', sourceB, 'op', undefined, paths),
+        'STORE_ALREADY_PRESENT',
+      );
+      expect(
+        readFileSync(join(paths.userRoot, 'skills', 'demo', '1.0.0', 'SKILL.md'), 'utf-8'),
+      ).toBe('# demo\n');
+    });
+
+    it('allows a second version alongside the first', () => {
+      addStoreEntry('skill', 'demo', '1.0.0', createSource('demo'), 'op', undefined, paths);
+      const result = addStoreEntry(
+        'skill',
+        'demo',
+        '1.1.0',
+        createSource('demo'),
+        'op',
+        undefined,
+        paths,
+      );
+      expect(result.status).toBe('added');
+      expect(readdirSync(join(paths.userRoot, 'skills', 'demo')).sort()).toEqual([
+        '1.0.0',
+        '1.1.0',
+      ]);
+    });
+
+    it('refuses an unmarked target directory by default and preserves its content', () => {
+      const unmarked = join(paths.userRoot, 'skills', 'demo', '1.0.0');
+      mkdirSync(unmarked, { recursive: true });
+      writeFileSync(join(unmarked, 'SKILL.md'), '# operator content\n');
+      expectStoreError(
+        () => addStoreEntry('skill', 'demo', '1.0.0', createSource('demo'), 'op', undefined, paths),
+        'STORE_TARGET_UNMARKED',
+      );
+      // The operator's hand-placed content survives the refusal.
+      expect(readFileSync(join(unmarked, 'SKILL.md'), 'utf-8')).toBe('# operator content\n');
+    });
+
+    it('reclaims an unmarked target only under explicit reclaim opt-in', () => {
+      const unmarked = join(paths.userRoot, 'skills', 'demo', '1.0.0');
+      mkdirSync(unmarked, { recursive: true });
+      writeFileSync(join(unmarked, 'SKILL.md'), '# torn write\n');
+      const result = addStoreEntry(
+        'skill',
+        'demo',
+        '1.0.0',
+        createSource('demo'),
+        'op',
+        undefined,
+        paths,
+        { reclaim: true },
+      );
+      expect(result.status).toBe('reclaimed-unmarked');
+      expect(readFileSync(join(unmarked, 'SKILL.md'), 'utf-8')).toBe('# demo\n');
+    });
+
+    it('reclaim can never destroy a marked, vetted entry (append-only holds under --reclaim)', () => {
+      addStoreEntry('skill', 'demo', '1.0.0', createSource('demo'), 'op', undefined, paths);
+      const marked = join(paths.userRoot, 'skills', 'demo', '1.0.0');
+      const vettedContent = readFileSync(join(marked, 'SKILL.md'), 'utf-8');
+      expectStoreError(
+        () =>
+          addStoreEntry('skill', 'demo', '1.0.0', createSource('demo'), 'op', undefined, paths, {
+            reclaim: true,
+          }),
+        'STORE_ALREADY_PRESENT',
+      );
+      // Load-bearing half: the throw alone does not prove nothing was deleted
+      // before it. Pins the marker-check-before-reclaim-check ordering against
+      // the guard-clause-migrates-upward refactor (review finding on b2124c6).
+      expect(readFileSync(join(marked, 'SKILL.md'), 'utf-8')).toBe(vettedContent);
+      expect(existsSync(join(marked, 'store-entry.json'))).toBe(true);
+    });
+
+    it('refuses a missing source with a typed error', () => {
+      expectStoreError(
+        () =>
+          addStoreEntry('skill', 'demo', '1.0.0', join(sourceRoot, 'nope'), 'op', undefined, paths),
+        'STORE_SOURCE_MISSING',
+      );
+    });
+
+    it('refuses a file (non-directory) source with a typed error', () => {
+      const filePath = join(sourceRoot, 'file.txt');
+      writeFileSync(filePath, 'x');
+      expectStoreError(
+        () => addStoreEntry('skill', 'demo', '1.0.0', filePath, 'op', undefined, paths),
+        'STORE_SOURCE_NOT_DIR',
+      );
+    });
+
+    it('refuses a symlinked source with a typed error and writes nothing', () => {
+      const real = createSource('demo');
+      const link = join(sourceRoot, 'demo-link');
+      symlinkSync(real, link);
+      expectStoreError(
+        () => addStoreEntry('skill', 'demo', '1.0.0', link, 'op', undefined, paths),
+        'STORE_SOURCE_SYMLINK',
+      );
+      expect(existsSync(join(paths.userRoot, 'skills', 'demo'))).toBe(false);
+    });
+
+    it('refuses a source tree containing nested symlinks and writes nothing', () => {
+      const src = createSource('demo');
+      const target = join(sourceRoot, 'elsewhere');
+      mkdirSync(target, { recursive: true });
+      symlinkSync(target, join(src, 'escape'));
+      expectStoreError(
+        () => addStoreEntry('skill', 'demo', '1.0.0', src, 'op', undefined, paths),
+        'STORE_SOURCE_SYMLINK',
+      );
+      expect(existsSync(join(paths.userRoot, 'skills', 'demo'))).toBe(false);
+    });
+
+    it('refuses adding from inside the store itself', () => {
+      const first = addStoreEntry(
+        'skill',
+        'demo',
+        '1.0.0',
+        createSource('demo'),
+        'op',
+        undefined,
+        paths,
+      );
+      expectStoreError(
+        () => addStoreEntry('skill', 'copy', '1.0.0', first.entryPath, 'op', undefined, paths),
+        'STORE_SOURCE_INSIDE_STORE',
+      );
+    });
+
+    it('refuses a symlinked user root ancestor', () => {
+      const linkedRoot = join(sourceRoot, 'linked-mosaic');
+      symlinkSync(paths.userRoot, linkedRoot);
+      expectStoreError(
+        () =>
+          addStoreEntry('skill', 'demo', '1.0.0', createSource('demo'), 'op', undefined, {
+            userRoot: linkedRoot,
+          }),
+        'STORE_SYMLINK_ROOT',
+      );
+    });
+
+    it('requires a non-empty vetting attribution', () => {
+      expectStoreError(
+        () => addStoreEntry('skill', 'demo', '1.0.0', createSource('demo'), '  ', undefined, paths),
+        'STORE_INVALID_VETTER',
+      );
+    });
+  });
+
+  describe('listStoreEntries', () => {
+    it('returns empty for an absent store without creating it', () => {
+      expect(listStoreEntries(paths)).toEqual([]);
+      expect(existsSync(paths.userRoot)).toBe(false);
+    });
+
+    it('lists entries deterministically with vetting metadata', () => {
+      addStoreEntry('plugin', 'alpha', '0.1.0', createSource('alpha'), 'fred', undefined, paths);
+      addStoreEntry('skill', 'beta', '2.0.0', createSource('beta'), 'fargo', 'looked fine', paths);
+      addStoreEntry('skill', 'beta', '2.1.0', createSource('beta'), 'fargo', undefined, paths);
+
+      const entries = listStoreEntries(paths);
+      expect(entries.map((e) => `${e.kind}:${e.name}:${e.version}`)).toEqual([
+        'plugin:alpha:0.1.0',
+        'skill:beta:2.0.0',
+        'skill:beta:2.1.0',
+      ]);
+      expect(entries[0]?.meta?.vettedBy).toBe('fred');
+      expect(entries[1]?.meta?.notes).toBe('looked fine');
+    });
+
+    it('classifies markerless version directories as incomplete', () => {
+      addStoreEntry('skill', 'demo', '1.0.0', createSource('demo'), 'op', undefined, paths);
+      mkdirSync(join(paths.userRoot, 'skills', 'demo', '2.0.0'), { recursive: true });
+      const entries = listStoreEntries(paths, { kind: 'skill', name: 'demo' });
+      expect(entries.find((e) => e.version === '1.0.0')?.status).toBe('vetted');
+      expect(entries.find((e) => e.version === '2.0.0')?.status).toBe('incomplete');
+    });
+
+    it('classifies malformed marker JSON as invalid-metadata, not vetted', () => {
+      addStoreEntry('skill', 'demo', '1.0.0', createSource('demo'), 'op', undefined, paths);
+      writeFileSync(
+        join(paths.userRoot, 'skills', 'demo', '1.0.0', 'store-entry.json'),
+        '{not json',
+      );
+      const entries = listStoreEntries(paths);
+      expect(entries[0]?.status).toBe('invalid-metadata');
+    });
+
+    it('surfaces foreign files (never mutates them)', () => {
+      mkdirSync(join(paths.userRoot, 'skills'), { recursive: true });
+      writeFileSync(join(paths.userRoot, 'skills', 'stray.txt'), 'x');
+      const entries = listStoreEntries(paths);
+      expect(entries[0]?.status).toBe('foreign');
+      expect(existsSync(join(paths.userRoot, 'skills', 'stray.txt'))).toBe(true);
+    });
+
+    it('filters by kind and name', () => {
+      addStoreEntry('plugin', 'alpha', '0.1.0', createSource('alpha'), 'op', undefined, paths);
+      addStoreEntry('skill', 'beta', '1.0.0', createSource('beta'), 'op', undefined, paths);
+      expect(listStoreEntries(paths, { kind: 'plugin' }).map((e) => e.name)).toEqual(['alpha']);
+      expect(listStoreEntries(paths, { name: 'beta' }).map((e) => e.name)).toEqual(['beta']);
+      expect(() => listStoreEntries(paths, { name: '../escape' })).toThrow(StoreError);
+    });
+  });
+
+  describe('default paths seam', () => {
+    it('honors MOSAIC_USER_HOME', () => {
+      const previous = process.env['MOSAIC_USER_HOME'];
+      try {
+        process.env['MOSAIC_USER_HOME'] = join(root, 'custom-user-home');
+        expect(getDefaultStorePaths().userRoot).toBe(join(root, 'custom-user-home'));
+        expect(storeKindDir('plugin')).toBe(join(root, 'custom-user-home', 'plugins'));
+      } finally {
+        if (previous === undefined) delete process.env['MOSAIC_USER_HOME'];
+        else process.env['MOSAIC_USER_HOME'] = previous;
+      }
+    });
+  });
+
+  describe('CLI', () => {
+    let previousExitCode: string | number | null | undefined;
+
+    beforeEach(() => {
+      previousExitCode = process.exitCode;
+      process.exitCode = undefined;
+    });
+
+    afterEach(() => {
+      process.exitCode = previousExitCode;
+    });
+
+    const parse = (args: string[]) => {
+      const program = new Command().exitOverride();
+      registerStoreCommand(program, paths);
+      return program.parseAsync(['node', 'mosaic', 'store', ...args]);
+    };
+
+    it('registers on the parent program and renders help', () => {
+      const program = new Command().exitOverride();
+      registerStoreCommand(program, paths);
+      const cmd = program.commands.find((c) => c.name() === 'store');
+      expect(cmd).toBeDefined();
+      expect(() => cmd?.helpInformation()).not.toThrow();
+    });
+
+    it('add exits nonzero with a typed code for an invalid name', async () => {
+      await parse([
+        'add',
+        'skill',
+        '../../etc',
+        '1.0.0',
+        '--from',
+        createSource('x'),
+        '--by',
+        'op',
+      ]);
+      expect(process.exitCode).toBe(1);
+    });
+
+    it('add exits nonzero when the kind is plural', async () => {
+      await parse(['add', 'skills', 'demo', '1.0.0', '--from', createSource('demo'), '--by', 'op']);
+      expect(process.exitCode).toBe(1);
+    });
+
+    it('add succeeds and creates the entry directory', async () => {
+      await parse(['add', 'skill', 'demo', '1.0.0', '--from', createSource('demo'), '--by', 'op']);
+      expect(process.exitCode).toBeUndefined();
+      expect(lstatSync(join(paths.userRoot, 'skills', 'demo', '1.0.0')).isDirectory()).toBe(true);
+    });
+
+    it('add requires --by (commander requiredOption)', async () => {
+      await expect(
+        parse(['add', 'skill', 'demo', '1.0.0', '--from', createSource('demo')]),
+      ).rejects.toThrow(/--by/);
+    });
+
+    it('add exits nonzero on an unmarked target without --reclaim, preserving content', async () => {
+      const unmarked = join(paths.userRoot, 'skills', 'demo', '1.0.0');
+      mkdirSync(unmarked, { recursive: true });
+      writeFileSync(join(unmarked, 'SKILL.md'), '# operator\n');
+      await parse(['add', 'skill', 'demo', '1.0.0', '--from', createSource('demo'), '--by', 'op']);
+      expect(process.exitCode).toBe(1);
+      expect(readFileSync(join(unmarked, 'SKILL.md'), 'utf-8')).toBe('# operator\n');
+    });
+
+    it('add --reclaim replaces the unmarked target and succeeds', async () => {
+      const unmarked = join(paths.userRoot, 'skills', 'demo', '1.0.0');
+      mkdirSync(unmarked, { recursive: true });
+      writeFileSync(join(unmarked, 'SKILL.md'), '# torn\n');
+      await parse([
+        'add',
+        'skill',
+        'demo',
+        '1.0.0',
+        '--from',
+        createSource('demo'),
+        '--by',
+        'op',
+        '--reclaim',
+      ]);
+      expect(process.exitCode).toBeUndefined();
+      expect(readFileSync(join(unmarked, 'SKILL.md'), 'utf-8')).toBe('# demo\n');
+    });
+
+    it('list exits 0 on an empty store', async () => {
+      await parse(['list']);
+      expect(process.exitCode).toBeUndefined();
+    });
+  });
+});

packages/mosaic/src/commands/store.ts

@@ -0,0 +1,544 @@
+import {
+  cpSync,
+  existsSync,
+  lstatSync,
+  mkdirSync,
+  readdirSync,
+  readFileSync,
+  rmSync,
+  writeFileSync,
+  type Dirent,
+  type Stats,
+} from 'node:fs';
+import { isAbsolute, join, parse, relative, resolve, sep } from 'node:path';
+import type { Command } from 'commander';
+import { DEFAULT_MOSAIC_USER_HOME } from '../constants.js';
+
+/**
+ * `mosaic store` — the vetted user store under `~/.mosaic/{plugins,skills}` (W-F4).
+ *
+ * Two roots with distinct ownership (HARNESS-HOMES design, frozen REV3):
+ * - `~/.config/mosaic/` is the SYSTEM root: update-owned, replaceable wholesale.
+ * - `~/.mosaic/` is the USER root: never touched by installs or updates.
+ *
+ * This module only ever writes under the USER root. The store is the vetting
+ * boundary: content lands here only through an explicit `store add` carrying a
+ * named vetting attribution, and every entry is versioned
+ * (`store/<kind>s/<name>/<version>/`) with a `store-entry.json` marker written
+ * LAST — a version directory without its marker is never a usable entry, and
+ * an unmarked target is REFUSED by default: it may be this tool's own debris
+ * from an interrupted add, or content the operator placed by hand, and the
+ * code cannot tell those apart — so deletion happens only under an explicit
+ * `--reclaim` opt-in, and the result status names what was done.
+ *
+ * Deferred by design (W-F6 and later): activation/symlink-install into agent
+ * homes, `current`-pointer pinning, network acquisition. `add` accepts a local
+ * source path only — no network, no credentials, ever.
+ */
+
+export type StoreKind = 'plugin' | 'skill';
+export const STORE_KINDS: readonly StoreKind[] = ['plugin', 'skill'];
+
+/** On-disk metadata marker; written last so its presence commits an entry. */
+export const STORE_ENTRY_MARKER = 'store-entry.json';
+
+export interface StorePaths {
+  /** User data root, e.g. `~/.mosaic`. */
+  userRoot: string;
+}
+
+export interface StoreEntryMeta {
+  schema: 1;
+  kind: StoreKind;
+  name: string;
+  version: string;
+  /** Absolute source path the content was vetted from, as resolved at add time. */
+  sourcePath: string;
+  /** Operator who vouched for the content — required, non-empty. */
+  vettedBy: string;
+  /** ISO timestamp of the add. */
+  vettedAt: string;
+  /** Free-form vetting notes, if any. */
+  notes?: string;
+}
+
+export type StoreAddStatus = 'added' | 'reclaimed-unmarked';
+
+export interface StoreAddResult {
+  kind: StoreKind;
+  name: string;
+  version: string;
+  status: StoreAddStatus;
+  entryPath: string;
+  sourcePath: string;
+}
+
+export type StoreEntryStatus = 'vetted' | 'incomplete' | 'invalid-metadata' | 'foreign';
+
+export interface StoreListEntry {
+  kind: StoreKind;
+  name: string;
+  /** Undefined for name-level foreign files (not a directory at all). */
+  version?: string;
+  status: StoreEntryStatus;
+  entryPath: string;
+  meta?: StoreEntryMeta;
+}
+
+const SAFE_STORE_NAME = /^[A-Za-z0-9][A-Za-z0-9._-]*$/;
+const SAFE_STORE_VERSION = /^[A-Za-z0-9][A-Za-z0-9._+-]*$/;
+
+export class StoreError extends Error {
+  public readonly code: string;
+
+  public constructor(code: string, message: string) {
+    super(message);
+    this.name = 'StoreError';
+    this.code = code;
+  }
+}
+
+/** Resolve the user store root while keeping tests injectable. */
+export function getDefaultStorePaths(): StorePaths {
+  const userRoot = process.env['MOSAIC_USER_HOME'] ?? DEFAULT_MOSAIC_USER_HOME;
+  return { userRoot };
+}
+
+/**
+ * Reject a user-supplied name before any filesystem operation.
+ * A store name identifies one directory under `store/<kind>s/`.
+ */
+export function validateStoreName(name: string): void {
+  if (
+    name.length === 0 ||
+    name.startsWith('-') ||
+    name.endsWith('.') ||
+    name.includes('..') ||
+    name.includes('/') ||
+    name.includes('\\') ||
+    isAbsolute(name) ||
+    !SAFE_STORE_NAME.test(name)
+  ) {
+    throw new StoreError(
+      'STORE_INVALID_NAME',
+      `Invalid store name ${JSON.stringify(name)}: use letters, numbers, dots, underscores, or hyphens; start with a letter or number; and do not use paths, "..", or a leading "-".`,
+    );
+  }
+}
+
+/** Versions share the name discipline plus `+` (semver build metadata). */
+export function validateStoreVersion(version: string): void {
+  if (
+    version.length === 0 ||
+    version.startsWith('-') ||
+    version.endsWith('.') ||
+    version.includes('..') ||
+    version.includes('/') ||
+    version.includes('\\') ||
+    isAbsolute(version) ||
+    !SAFE_STORE_VERSION.test(version)
+  ) {
+    throw new StoreError(
+      'STORE_INVALID_VERSION',
+      `Invalid version ${JSON.stringify(version)}: use letters, numbers, dots, underscores, hyphens, or plus; start with a letter or number; and do not use paths, "..", or a leading "-".`,
+    );
+  }
+}
+
+export function validateStoreKind(kind: string): asserts kind is StoreKind {
+  if (!(STORE_KINDS as readonly string[]).includes(kind)) {
+    throw new StoreError(
+      'STORE_INVALID_KIND',
+      `Invalid store kind ${JSON.stringify(kind)}: expected one of ${STORE_KINDS.map((k) => `"${k}"`).join(', ')}.`,
+    );
+  }
+}
+
+function validateVettedBy(vettedBy: string): void {
+  if (vettedBy.trim().length === 0 || vettedBy.includes('\n') || vettedBy.length > 80) {
+    throw new StoreError(
+      'STORE_INVALID_VETTER',
+      'Invalid --by value: name the operator vouching for this content (single line, at most 80 characters).',
+    );
+  }
+}
+
+function lstatIfPresent(path: string): Stats | undefined {
+  try {
+    return lstatSync(path);
+  } catch (error: unknown) {
+    if (error instanceof Error && 'code' in error && error.code === 'ENOENT') return undefined;
+    throw error;
+  }
+}
+
+function assertNoSymlinkAncestors(path: string): void {
+  const absolute = resolve(path);
+  const pathRoot = parse(absolute).root;
+  let current = pathRoot;
+
+  for (const segment of relative(pathRoot, absolute).split(sep)) {
+    if (segment.length === 0) continue;
+    current = join(current, segment);
+    const entry = lstatIfPresent(current);
+    if (!entry) break;
+    if (entry.isSymbolicLink()) {
+      throw new StoreError(
+        'STORE_SYMLINK_ROOT',
+        `Refusing symlink ancestor at ${current}; the user store root must resolve without symlink traversal.`,
+      );
+    }
+  }
+}
+
+/** `plugins` for plugin, `skills` for skill — plural on disk per the layout. */
+function kindDirName(kind: StoreKind): string {
+  return kind === 'plugin' ? 'plugins' : 'skills';
+}
+
+export function storeKindDir(kind: StoreKind, paths: StorePaths = getDefaultStorePaths()): string {
+  return join(paths.userRoot, kindDirName(kind));
+}
+
+function entryDir(kind: StoreKind, name: string, version: string, paths: StorePaths): string {
+  return join(storeKindDir(kind, paths), name, version);
+}
+
+function isInsideRoot(candidate: string, root: string): boolean {
+  const rel = relative(resolve(root), resolve(candidate));
+  return rel.length > 0 && rel !== '..' && !rel.startsWith(`..${sep}`) && !isAbsolute(rel);
+}
+
+/**
+ * Refuse any symlink in the source tree — the vetting boundary copies real
+ * content only, so a vetted entry can never carry a link that escapes it.
+ *
+ * NOTE: known check-then-use window between this walk and the `cpSync` below:
+ * a symlink created concurrently with the add could slip through. Accepted
+ * for a local, operator-run CLI; revisit before any unattended or networked
+ * acquisition path exists.
+ */
+function assertSourceTreeHasNoSymlinks(sourcePath: string): void {
+  const stack: string[] = [sourcePath];
+  while (stack.length > 0) {
+    const current = stack.pop()!;
+    for (const dirent of readdirSync(current, { withFileTypes: true })) {
+      const child = join(current, dirent.name);
+      if (dirent.isSymbolicLink()) {
+        throw new StoreError(
+          'STORE_SOURCE_SYMLINK',
+          `Refusing to vet content containing a symlink: ${child}. Resolve or remove symlinks before adding to the store.`,
+        );
+      }
+      if (dirent.isDirectory()) stack.push(child);
+    }
+  }
+}
+
+/**
+ * Vet and add one versioned entry to the user store.
+ *
+ * Copies the source directory (real content, no symlinks) to
+ * `<userRoot>/<kind>s/<name>/<version>/` and writes the `store-entry.json`
+ * marker LAST: a crash mid-copy leaves at most a recoverable partial, never a
+ * half-vetted entry that lists as present.
+ */
+export function addStoreEntry(
+  kind: StoreKind,
+  name: string,
+  version: string,
+  sourcePath: string,
+  vettedBy: string,
+  notes: string | undefined,
+  paths: StorePaths = getDefaultStorePaths(),
+  options: { reclaim?: boolean } = {},
+): StoreAddResult {
+  validateStoreKind(kind);
+  validateStoreName(name);
+  validateStoreVersion(version);
+  validateVettedBy(vettedBy);
+  assertNoSymlinkAncestors(paths.userRoot);
+
+  const resolvedSource = resolve(sourcePath);
+  const source = lstatIfPresent(resolvedSource);
+  if (!source) {
+    throw new StoreError('STORE_SOURCE_MISSING', `Source path does not exist: ${resolvedSource}`);
+  }
+  if (source.isSymbolicLink()) {
+    throw new StoreError(
+      'STORE_SOURCE_SYMLINK',
+      `Refusing to vet a symlink as store content: ${resolvedSource} (points at ${resolve(sourcePath)}). Add the real directory.`,
+    );
+  }
+  if (!source.isDirectory()) {
+    throw new StoreError(
+      'STORE_SOURCE_NOT_DIR',
+      `Source path is not a directory: ${resolvedSource}`,
+    );
+  }
+  if (isInsideRoot(resolvedSource, paths.userRoot)) {
+    throw new StoreError(
+      'STORE_SOURCE_INSIDE_STORE',
+      `Refusing to add store content from inside the store itself: ${resolvedSource}`,
+    );
+  }
+  assertSourceTreeHasNoSymlinks(resolvedSource);
+
+  const target = entryDir(kind, name, version, paths);
+  const existing = lstatIfPresent(target);
+  let status: StoreAddStatus = 'added';
+  if (existing) {
+    if (existsSync(join(target, STORE_ENTRY_MARKER))) {
+      throw new StoreError(
+        'STORE_ALREADY_PRESENT',
+        `${kind} "${name}" version "${version}" is already present at ${target}; stores are append-only — add a new version instead.`,
+      );
+    }
+    // Unmarked target: either this tool's own debris from an interrupted add,
+    // or content the operator placed by hand — indistinguishable on disk. The
+    // USER root's contract is that tooling never destroys operator content,
+    // so deletion requires the explicit --reclaim opt-in (review finding on
+    // c23a71d7: silent rmSync under a benign-sounding status).
+    if (!options.reclaim) {
+      throw new StoreError(
+        'STORE_TARGET_UNMARKED',
+        `Target exists without ${STORE_ENTRY_MARKER}: ${target}. Refusing to delete unmarked content — if this is debris from an interrupted add, re-run with --reclaim to replace it.`,
+      );
+    }
+    rmSync(target, { recursive: true, force: true });
+    status = 'reclaimed-unmarked';
+  }
+
+  mkdirSync(target, { recursive: true });
+  cpSync(resolvedSource, target, { recursive: true });
+
+  const meta: StoreEntryMeta = {
+    schema: 1,
+    kind,
+    name,
+    version,
+    sourcePath: resolvedSource,
+    vettedBy: vettedBy.trim(),
+    vettedAt: new Date().toISOString(),
+    ...(notes === undefined ? {} : { notes }),
+  };
+  writeFileSync(join(target, STORE_ENTRY_MARKER), `${JSON.stringify(meta, null, 2)}\n`);
+
+  return { kind, name, version, status, entryPath: target, sourcePath: resolvedSource };
+}
+
+function readEntryMeta(markerPath: string): { meta?: StoreEntryMeta; status: StoreEntryStatus } {
+  let raw: string;
+  try {
+    raw = readFileSync(markerPath, 'utf-8');
+  } catch {
+    return { status: 'invalid-metadata' };
+  }
+  try {
+    const parsed = JSON.parse(raw) as StoreEntryMeta;
+    if (
+      parsed?.schema === 1 &&
+      (STORE_KINDS as readonly string[]).includes(parsed.kind) &&
+      typeof parsed.name === 'string' &&
+      typeof parsed.version === 'string' &&
+      typeof parsed.vettedBy === 'string' &&
+      typeof parsed.vettedAt === 'string'
+    ) {
+      return { meta: parsed, status: 'vetted' };
+    }
+  } catch {
+    // fall through
+  }
+  return { status: 'invalid-metadata' };
+}
+
+/**
+ * Enumerate every store entry deterministically (kind, then name, then
+ * version). Version directories without a marker list as `incomplete`; files
+ * where directories were expected list as `foreign` — surfaced, never mutated.
+ */
+export function listStoreEntries(
+  paths: StorePaths = getDefaultStorePaths(),
+  filter: { kind?: StoreKind; name?: string } = {},
+): StoreListEntry[] {
+  if (filter.name !== undefined) validateStoreName(filter.name);
+  assertNoSymlinkAncestors(paths.userRoot);
+
+  const kinds = filter.kind ? [filter.kind] : [...STORE_KINDS];
+  const entries: StoreListEntry[] = [];
+
+  for (const kind of kinds) {
+    const kindRoot = lstatIfPresent(storeKindDir(kind, paths));
+    if (!kindRoot) continue;
+    if (!kindRoot.isDirectory()) {
+      entries.push({
+        kind,
+        name: kindDirName(kind),
+        status: 'foreign',
+        entryPath: storeKindDir(kind, paths),
+      });
+      continue;
+    }
+
+    for (const nameDirent of readdirSync(storeKindDir(kind, paths), {
+      withFileTypes: true,
+    }).sort(byName) as Dirent[]) {
+      if (filter.name !== undefined && nameDirent.name !== filter.name) continue;
+      const namePath = join(storeKindDir(kind, paths), nameDirent.name);
+
+      if (!nameDirent.isDirectory()) {
+        entries.push({ kind, name: nameDirent.name, status: 'foreign', entryPath: namePath });
+        continue;
+      }
+
+      const versionDirents = readdirSync(namePath, { withFileTypes: true }).sort(byName);
+      if (versionDirents.length === 0) {
+        entries.push({ kind, name: nameDirent.name, status: 'incomplete', entryPath: namePath });
+        continue;
+      }
+      for (const versionDirent of versionDirents) {
+        const versionPath = join(namePath, versionDirent.name);
+        if (!versionDirent.isDirectory()) {
+          entries.push({
+            kind,
+            name: nameDirent.name,
+            version: versionDirent.name,
+            status: 'foreign',
+            entryPath: versionPath,
+          });
+          continue;
+        }
+        const markerPath = join(versionPath, STORE_ENTRY_MARKER);
+        if (!existsSync(markerPath)) {
+          entries.push({
+            kind,
+            name: nameDirent.name,
+            version: versionDirent.name,
+            status: 'incomplete',
+            entryPath: versionPath,
+          });
+          continue;
+        }
+        const { meta, status } = readEntryMeta(markerPath);
+        entries.push({
+          kind,
+          name: nameDirent.name,
+          version: versionDirent.name,
+          status,
+          entryPath: versionPath,
+          ...(meta === undefined ? {} : { meta }),
+        });
+      }
+    }
+  }
+
+  return entries;
+}
+
+function byName(a: Dirent, b: Dirent): number {
+  return a.name < b.name ? -1 : a.name > b.name ? 1 : 0;
+}
+
+function reportCommandError(error: unknown): void {
+  if (error instanceof StoreError) {
+    console.error(`store: ${error.code}: ${error.message}`);
+  } else {
+    console.error(error instanceof Error ? error.message : String(error));
+  }
+  process.exitCode = 1;
+}
+
+function displayStoreName(name: string): string {
+  return SAFE_STORE_NAME.test(name) ? name : JSON.stringify(name);
+}
+
+/** Register the `mosaic store` command group (W-F4). */
+export function registerStoreCommand(
+  program: Command,
+  paths: StorePaths = getDefaultStorePaths(),
+): void {
+  const store = program
+    .command('store')
+    .description('Manage the vetted user store under ~/.mosaic (plugins, skills)')
+    .configureHelp({ sortSubcommands: true });
+
+  store
+    .command('add <kind> <name> <version>')
+    .description(
+      'Vet and add a local plugin/skill directory to the user store (versioned, append-only)',
+    )
+    .requiredOption('--from <path>', 'Local source directory to vet (no network acquisition)')
+    .requiredOption('--by <operator>', 'Name of the operator vouching for this content')
+    .option('--notes <notes>', 'Vetting notes recorded in the entry metadata')
+    .option(
+      '--reclaim',
+      'Replace an existing UNMARKED target directory (e.g. debris from an interrupted add); refuses without this flag',
+    )
+    .action(
+      async (
+        kind: string,
+        name: string,
+        version: string,
+        opts: {
+          from: string;
+          by: string;
+          notes?: string;
+          reclaim: boolean;
+        },
+      ) => {
+        try {
+          const result = addStoreEntry(
+            kind as StoreKind,
+            name,
+            version,
+            opts.from,
+            opts.by,
+            opts.notes,
+            paths,
+            { reclaim: opts.reclaim },
+          );
+          const suffix =
+            result.status === 'reclaimed-unmarked' ? ' (replaced unmarked directory)' : '';
+          console.log(
+            `${result.kind} ${displayStoreName(result.name)} ${result.version}: added${suffix}`,
+          );
+          console.log(`  entry: ${result.entryPath}`);
+          console.log(`  vetted by ${opts.by.trim()}`);
+        } catch (error: unknown) {
+          reportCommandError(error);
+        }
+      },
+    );
+
+  store
+    .command('list')
+    .description('List store entries with vetting status')
+    .option('--kind <kind>', 'Filter by kind (plugin | skill)')
+    .option('--name <name>', 'Filter by entry name')
+    .action((opts: { kind?: string; name?: string }) => {
+      try {
+        let kind: StoreKind | undefined;
+        if (opts.kind !== undefined) {
+          validateStoreKind(opts.kind);
+          kind = opts.kind;
+        }
+        const entries = listStoreEntries(paths, {
+          ...(kind === undefined ? {} : { kind }),
+          ...(opts.name === undefined ? {} : { name: opts.name }),
+        });
+        if (entries.length === 0) {
+          console.log('No store entries found.');
+          return;
+        }
+        for (const entry of entries) {
+          const version = entry.version ?? '-';
+          const vetter = entry.meta?.vettedBy ?? '-';
+          console.log(
+            `${entry.status.padEnd(17)}${entry.kind.padEnd(8)}${displayStoreName(entry.name).padEnd(24)}${version.padEnd(16)}${vetter}`,
+          );
+        }
+      } catch (error: unknown) {
+        reportCommandError(error);
+      }
+    });
+}

packages/mosaic/src/constants.ts

@@ -5,6 +5,13 @@ export const VERSION = '0.0.2';
 
 export const DEFAULT_MOSAIC_HOME = join(homedir(), '.config', 'mosaic');
 
+/**
+ * USER data root (HARNESS-HOMES two-root split): everything under here is user
+ * content — never replaced or removed by installs, updates, or uninstallers.
+ * Distinct from the SYSTEM root above, which is update-owned.
+ */
+export const DEFAULT_MOSAIC_USER_HOME = join(homedir(), '.mosaic');
+
 export const DEFAULTS = {
   agentName: 'Assistant',
   roleDescription: 'execution partner and visibility engine',