diff --git a/scripts/__tests__/spec-main-shape-gate.test.ts b/scripts/__tests__/spec-main-shape-gate.test.ts
index 12a487907b..d6051acd9c 100644
--- a/scripts/__tests__/spec-main-shape-gate.test.ts
+++ b/scripts/__tests__/spec-main-shape-gate.test.ts
@@ -11,6 +11,8 @@ import {
   satisfiesRange,
   parseWorkspaceGlobs,
   MARKER_FILE,
+  SPEC_PACKAGE_NAME,
+  TURBO_HASH_MARKER,
 } from '../spec-main-shape-gate.mjs';
 import { pullRequestTrigger, readWorkflows, repoRoot, subscribesMergeGroup } from './workflow-checks.js';
 
@@ -564,3 +566,162 @@ describe('the injection reads the spec against the dependencies it was built wit
     expect(() => satisfiesRange('4.6.1', 'workspace:*')).toThrow(/does not read/);
   });
 });
+
+/**
+ * objectui#12114 — a linked git worktree shares the main checkout's turbo
+ * cache, and `--force` skips cache reads but still WRITES. So a local
+ * reproduction of this gate recorded main-spec verdicts that a sibling
+ * worktree's ordinary, installed-spec `pnpm type-check` replayed as its own: a
+ * false green. The fix puts the injection inside turbo's hash, through
+ * `turbo.json`'s `globalDependencies`; the script header carries the why.
+ *
+ * The second case drives a REAL turbo (`--dry=json`, which computes the hashes
+ * and runs nothing) over a fixture that copies this repository's `turbo.json`,
+ * so it fails the day that file stops hashing the marker.
+ */
+describe('a local reproduction cannot leave a verdict an installed tree replays (objectui#12114)', () => {
+  const made: string[] = [];
+  afterEach(() => {
+    for (const dir of made.splice(0)) fs.rmSync(dir, { recursive: true, force: true });
+  });
+
+  const STORE_SPEC = 'node_modules/.pnpm/@objectstack+spec@17.4.0/node_modules/@objectstack/spec';
+
+  /**
+   * An installed tree, linked the way pnpm links it (RELATIVE symlinks into the
+   * virtual store), in a git repository that ignores `node_modules` as this one
+   * does: the file turbo has to hash is an ignored one.
+   */
+  function installedTree({ rootLink }: { rootLink: boolean }) {
+    const root = fs.mkdtempSync(path.join(os.tmpdir(), 'spec-gate-turbo-'));
+    made.push(root);
+    const repo = path.join(root, 'objectui');
+    fs.mkdirSync(path.join(repo, 'scripts'), { recursive: true });
+    for (const file of ['spec-main-shape-gate.mjs', 'invoked-as.mjs']) {
+      fs.copyFileSync(path.join(repoRoot, 'scripts', file), path.join(repo, 'scripts', file));
+    }
+    fs.copyFileSync(path.join(repoRoot, 'turbo.json'), path.join(repo, 'turbo.json'));
+
+    const store = path.join(repo, STORE_SPEC);
+    // What a reinstall does to an injected copy: the directory is replaced.
+    const install = () => {
+      fs.rmSync(store, { recursive: true, force: true });
+      fs.mkdirSync(store, { recursive: true });
+      fs.writeFileSync(path.join(store, 'package.json'), JSON.stringify({ name: SPEC_PACKAGE_NAME, version: '17.4.0' }));
+    };
+    install();
+    const devDependencies = rootLink ? { [SPEC_PACKAGE_NAME]: '^17.4.0' } : {};
+    if (rootLink) {
+      fs.mkdirSync(path.join(repo, 'node_modules', '@objectstack'), { recursive: true });
+      fs.symlinkSync(`../.pnpm/@objectstack+spec@17.4.0/node_modules/@objectstack/spec`, path.join(repo, 'node_modules', '@objectstack', 'spec'));
+    }
+    const app = path.join(repo, 'packages', 'app');
+    fs.mkdirSync(path.join(app, 'node_modules', '@objectstack'), { recursive: true });
+    fs.symlinkSync(`../../../../${STORE_SPEC}`, path.join(app, 'node_modules', '@objectstack', 'spec'));
+    fs.writeFileSync(
+      path.join(app, 'package.json'),
+      JSON.stringify({ name: 'app', scripts: { 'type-check': 'tsc --noEmit' }, dependencies: { [SPEC_PACKAGE_NAME]: '^17.4.0' } }),
+    );
+    fs.writeFileSync(
+      path.join(repo, 'package.json'),
+      JSON.stringify({ name: 'root', private: true, packageManager: 'pnpm@10.31.0', devDependencies }),
+    );
+    fs.writeFileSync(path.join(repo, 'pnpm-workspace.yaml'), "packages:\n  - 'packages/*'\n");
+    fs.writeFileSync(path.join(repo, '.gitignore'), 'node_modules\n.turbo\n');
+    execFileSync('git', ['init', '-q'], { cwd: repo });
+
+    const upstream = path.join(root, 'objectstack');
+    fs.mkdirSync(path.join(upstream, 'packages', 'spec'), { recursive: true });
+    fs.writeFileSync(path.join(upstream, 'packages', 'spec', 'package.json'), JSON.stringify({ name: SPEC_PACKAGE_NAME }));
+    const pack = path.join(root, 'pack', 'package');
+    fs.mkdirSync(path.join(pack, 'dist'), { recursive: true });
+    fs.writeFileSync(path.join(pack, 'dist', 'index.d.ts'), 'export {};\n');
+    fs.writeFileSync(
+      path.join(pack, 'package.json'),
+      JSON.stringify({ name: SPEC_PACKAGE_NAME, version: '17.4.0', exports: { '.': { types: './dist/index.d.ts' } } }),
+    );
+    const tarball = path.join(root, 'spec.tgz');
+    execFileSync('tar', ['-czf', tarball, '-C', path.join(root, 'pack'), 'package']);
+
+    const inject = () =>
+      spawnSync(
+        'node',
+        [path.join(repo, 'scripts', 'spec-main-shape-gate.mjs'), 'inject', '--tarball', tarball, '--sha', 'f'.repeat(40), '--upstream-checkout', upstream],
+        { encoding: 'utf8' },
+      );
+    // The global files turbo hashed, and every task's hash.
+    const hashes = () => {
+      const env = Object.fromEntries(Object.entries(process.env).filter(([name]) => !name.startsWith('TURBO_')));
+      const dry = JSON.parse(
+        execFileSync(path.join(repoRoot, 'node_modules', '.bin', 'turbo'), ['run', 'type-check', '--dry=json'], {
+          cwd: repo,
+          encoding: 'utf8',
+          env: { ...env, TURBO_TELEMETRY_DISABLED: '1' },
+          // turbo warns that the fixture has no lockfile; a failure still throws with it.
+          stdio: ['ignore', 'pipe', 'pipe'],
+        }),
+      );
+      const tasks: Record<string, string> = {};
+      for (const task of dry.tasks) tasks[task.taskId] = task.hash;
+      return { files: Object.keys(dry.globalCacheInputs.files), tasks };
+    };
+    return { install, inject, hashes };
+  }
+
+  it('turbo.json hashes the marker inject writes, by a literal path through the root link', () => {
+    expect(TURBO_HASH_MARKER).toBe(`node_modules/${SPEC_PACKAGE_NAME}/${MARKER_FILE}`);
+    const turbo = JSON.parse(fs.readFileSync(path.join(repoRoot, 'turbo.json'), 'utf8'));
+    expect(turbo.globalDependencies ?? [], 'without it an injected tree and an installed one hash alike').toContain(
+      TURBO_HASH_MARKER,
+    );
+    // turbo does not expand a wildcard inside node_modules: a glob there would
+    // hash nothing, silently.
+    expect(TURBO_HASH_MARKER).not.toMatch(/[*?[{!]/);
+    // pnpm creates the root link the path goes through only because the root
+    // manifest declares the spec.
+    const manifest = JSON.parse(fs.readFileSync(path.join(repoRoot, 'package.json'), 'utf8'));
+    expect(
+      ['dependencies', 'devDependencies', 'optionalDependencies'].some((field) => manifest[field]?.[SPEC_PACKAGE_NAME]),
+      `the root manifest no longer declares ${SPEC_PACKAGE_NAME}, so ${TURBO_HASH_MARKER} never exists`,
+    ).toBe(true);
+    // The marker can never be committed.
+    expect(spawnSync('git', ['check-ignore', '-q', 'node_modules'], { cwd: repoRoot }).status).toBe(0);
+  });
+
+  it('real turbo: an injected tree hashes apart from an installed one, and back once the injection is undone', () => {
+    const tree = installedTree({ rootLink: true });
+    const installed = tree.hashes();
+    expect(installed.tasks).toHaveProperty(['app#type-check']);
+    expect(installed.files).not.toContain(TURBO_HASH_MARKER);
+
+    const first = tree.inject();
+    expect(first.status, first.stderr).toBe(0);
+    expect(first.stdout).toContain(`turbo hashes ${TURBO_HASH_MARKER}`);
+    const injected = tree.hashes();
+    expect(injected.files).toContain(TURBO_HASH_MARKER);
+    for (const [task, hash] of Object.entries(installed.tasks)) {
+      expect(injected.tasks[task], `${task} hashes as installed after an injection`).not.toBe(hash);
+    }
+
+    // A second injection at the same sha shares no entry with the first.
+    expect(tree.inject().status).toBe(0);
+    const again = tree.hashes();
+    for (const [task, hash] of Object.entries(injected.tasks)) expect(again.tasks[task]).not.toBe(hash);
+
+    // Undone the way a reinstall undoes it, the tree hashes as installed again:
+    // the marker cannot outlive the injection.
+    tree.install();
+    expect(tree.hashes()).toEqual(installed);
+  });
+
+  it('the firing control: without the root link the same injection hashes as installed, and inject says so', () => {
+    // The marker inside the virtual store alone is invisible to turbo, so the
+    // hash above moved because of the root-linked path and nothing else.
+    const tree = installedTree({ rootLink: false });
+    const installed = tree.hashes();
+    const result = tree.inject();
+    expect(result.status, result.stderr).toBe(0);
+    expect(result.stdout).toContain(`⚠️ ${TURBO_HASH_MARKER} is absent`);
+    expect(tree.hashes()).toEqual(installed);
+  });
+});
diff --git a/scripts/__tests__/turbo-build-inputs.test.ts b/scripts/__tests__/turbo-build-inputs.test.ts
index 39dcedc02f..f571f4c81a 100644
--- a/scripts/__tests__/turbo-build-inputs.test.ts
+++ b/scripts/__tests__/turbo-build-inputs.test.ts
@@ -19,7 +19,7 @@ import { CONFIG_FILES as VITEST_CONFIG_FILES } from './helpers/vitest-config-pro
  * the one with the widest blast radius.
  *
  * Turbo hashes a task from its `inputs`. `$TURBO_DEFAULT$` covers only files
- * inside the package directory, and `globalDependencies` is unset — so any file
+ * inside the package directory, and `globalDependencies` holds no source file — so any file
  * the task reads from elsewhere in the repo is invisible to the cache key. When
  * such a file changes, turbo does not re-run the task; it REPLAYS the previous
  * verdict. `build` declared no `inputs` AT ALL, so it ran on that default,
diff --git a/scripts/__tests__/turbo-lint-inputs.test.ts b/scripts/__tests__/turbo-lint-inputs.test.ts
index 394297dfd7..a9fcdd0531 100644
--- a/scripts/__tests__/turbo-lint-inputs.test.ts
+++ b/scripts/__tests__/turbo-lint-inputs.test.ts
@@ -23,7 +23,7 @@ import {
  * `test`, and it is the starkest of the three.
  *
  * Turbo hashes a task from its `inputs`. `$TURBO_DEFAULT$` covers only files
- * inside the package directory, and `globalDependencies` is unset — so any file
+ * inside the package directory, and `globalDependencies` holds no source file — so any file
  * the task reads from elsewhere in the repo is invisible to the cache key. When
  * such a file changes, turbo does not re-run the task; it REPLAYS the previous
  * verdict. `lint` declared no `inputs` AT ALL, so it ran on that default:
diff --git a/scripts/__tests__/turbo-test-inputs.test.ts b/scripts/__tests__/turbo-test-inputs.test.ts
index cb8e359598..df8fee509a 100644
--- a/scripts/__tests__/turbo-test-inputs.test.ts
+++ b/scripts/__tests__/turbo-test-inputs.test.ts
@@ -19,7 +19,7 @@ import {
  * that objectui#3514 closed for `type-check`, and it has it worse.
  *
  * Turbo hashes a task from its `inputs`. `$TURBO_DEFAULT$` covers only files
- * inside the package directory, and `globalDependencies` is unset — so any file
+ * inside the package directory, and `globalDependencies` holds no source file — so any file
  * the task reads from elsewhere in the repo is invisible to the cache key. When
  * such a file changes, turbo does not re-run the task; it REPLAYS the previous
  * verdict. Before this guard, EVERY entry in the `test` task's list was
diff --git a/scripts/__tests__/turbo-type-check-inputs.test.ts b/scripts/__tests__/turbo-type-check-inputs.test.ts
index a0d2694039..ce96167d0e 100644
--- a/scripts/__tests__/turbo-type-check-inputs.test.ts
+++ b/scripts/__tests__/turbo-type-check-inputs.test.ts
@@ -14,7 +14,7 @@ import { outOfPackageFiles } from './helpers/tsc-program';
  * program reaches OUTSIDE its own package directory.
  *
  * Turbo hashes a task from its `inputs`. `$TURBO_DEFAULT$` covers only files
- * inside the package directory, and `globalDependencies` is unset — so any file
+ * inside the package directory, and `globalDependencies` holds no source file — so any file
  * the program reads from elsewhere in the repo is invisible to the cache key.
  * When such a file changes, turbo does not re-run the task; it REPLAYS the
  * previous verdict. That is a gate whose answer depends on cache state rather
diff --git a/scripts/spec-main-shape-gate.mjs b/scripts/spec-main-shape-gate.mjs
index 2e2862818f..b85652599e 100644
--- a/scripts/spec-main-shape-gate.mjs
+++ b/scripts/spec-main-shape-gate.mjs
@@ -158,12 +158,45 @@
  *
  * `turbo`'s `type-check` task is cached, and its hash covers this repository's
  * sources, its lockfile and a declared env list -- it does NOT cover the CONTENT
- * of `node_modules`. An injected spec therefore changes nothing turbo hashes:
- * a second run after an injection can replay the verdict recorded BEFORE it, and
- * a run at a new objectstack sha can replay the verdict from the old one. Both
- * are green answers to a question that was never asked. The workflow runs the
- * typecheck with the cache bypassed for exactly this reason, and
- * `scripts/__tests__/spec-main-shape-gate.test.ts` pins that it keeps doing so.
+ * of `node_modules`. The injected spec's own files therefore change nothing
+ * turbo hashes: a second run after an injection could replay the verdict
+ * recorded BEFORE it, and a run at a new objectstack sha the verdict from the
+ * old one. Both are green answers to a question that was never asked. The
+ * workflow runs the typecheck with the cache bypassed for exactly this reason,
+ * and `scripts/__tests__/spec-main-shape-gate.test.ts` pins that it keeps doing
+ * so. The marker below closes both cases too; the bypass does not lean on it.
+ *
+ * ## ...and an injected tree must not leave a verdict an INSTALLED tree replays (objectui#12114)
+ *
+ * The reverse direction is local, and the bypass does not close it: `--force`
+ * (`TURBO_FORCE=true`) skips cache READS and still WRITES. A linked git worktree
+ * shares the main checkout's `.turbo/cache` (turbo logs "using shared worktree
+ * cache"), so a reproduction in one worktree recorded main-spec verdicts that a
+ * later ordinary `pnpm type-check` in a sibling -- same sources, installed spec
+ * -- replayed as its own. The measurement is on this issue's pull request.
+ *
+ * So the injection is part of turbo's hash: `turbo.json`'s `globalDependencies`
+ * names `TURBO_HASH_MARKER`, the `MARKER_FILE` `inject` writes into every
+ * replaced copy, reached through the root link to the spec. Measured on turbo
+ * 2.10:
+ *
+ *  - Absent, a global dependency hashes as nothing: installed trees share
+ *    entries with each other as before, and an injected tree hashes apart from
+ *    all of them in both directions, with no flag to remember. The marker holds
+ *    the sha and the injection time, so two injections never share one either.
+ *  - The path is LITERAL because turbo does not expand a wildcard inside
+ *    `node_modules`: a glob over the virtual store hashes nothing, silently. The
+ *    root link exists because the root manifest declares the spec; the consumer
+ *    proof below requires it to resolve to a marked copy, and `inject` says so
+ *    out loud when there is no root link to hash.
+ *  - The marker lives INSIDE the replaced copy, so it cannot outlive the
+ *    injection: `pnpm install --force` or a fresh install replaces that
+ *    directory, and the tree hashes as installed again. A plain `pnpm install`
+ *    leaves the injection and its marker both in place.
+ *
+ * A local reproduction is therefore `inject`, then `pnpm type-check --continue`
+ * with no flag, then `pnpm install --frozen-lockfile --force` to undo it. The
+ * test file above pins the wiring and drives a real turbo over a fixture.
  */
 
 import fs from 'node:fs';
@@ -183,6 +216,13 @@ export const UPSTREAM_REPO = 'objectstack-ai/objectstack';
 /** The marker `inject` leaves inside every replaced copy. */
 export const MARKER_FILE = '.spec-main-shape-gate.json';
 
+/**
+ * That marker as `turbo.json`'s `globalDependencies` names it: a LITERAL path
+ * through the repository root's own link to the spec. See "...and an injected
+ * tree must not leave a verdict" in the header.
+ */
+export const TURBO_HASH_MARKER = ['node_modules', SPEC_PACKAGE_NAME, MARKER_FILE].join('/');
+
 const repoRootDefault = path.resolve(path.dirname(fileURLToPath(import.meta.url)), '..');
 
 /**
@@ -833,7 +873,20 @@ export function inject({ tarball, sha, upstreamCheckout, repoRoot = repoRootDefa
     );
   }
 
-  return { targets, consumers, version: manifest.version, sha, substitutions, resolutions, oneCopy };
+  // The marker turbo hashes (objectui#12114). The root link, when there is one,
+  // already passed the consumer proof above, so this reads where turbo will look.
+  const hashMarker = fs.existsSync(path.join(repoRoot, TURBO_HASH_MARKER)) ? TURBO_HASH_MARKER : null;
+  log(
+    hashMarker
+      ? `spec-main-shape-gate: turbo hashes ${hashMarker}, so this tree's task hashes no longer match an ` +
+          `installed tree's: a type-check here neither replays an installed verdict nor leaves one for a sibling ` +
+          `worktree. \`pnpm install --frozen-lockfile --force\` undoes the injection and the marker together.`
+      : `spec-main-shape-gate: ⚠️ ${TURBO_HASH_MARKER} is absent -- no root link to the spec -- so turbo hashes ` +
+          `this tree like an installed one, and a type-check here leaves verdicts a sibling worktree's installed ` +
+          `type-check can replay.`,
+  );
+
+  return { targets, consumers, version: manifest.version, sha, substitutions, resolutions, oneCopy, hashMarker };
 }
 
 /**
diff --git a/turbo.json b/turbo.json
index b74c7b6b71..05f98df9e1 100644
--- a/turbo.json
+++ b/turbo.json
@@ -1,6 +1,7 @@
 {
   "$schema": "https://turbo.build/schema.json",
   "globalEnv": ["NODE_ENV"],
+  "globalDependencies": ["node_modules/@objectstack/spec/.spec-main-shape-gate.json"],
   "tasks": {
     "build": {
       "dependsOn": ["^build"],