diff --git a/.agents/plugins/marketplace.json b/.agents/plugins/marketplace.json
new file mode 100644
index 0000000000..127ba2f874
--- /dev/null
+++ b/.agents/plugins/marketplace.json
@@ -0,0 +1,20 @@
+{
+  "name": "gstack-local",
+  "interface": {
+    "displayName": "gstack Local Plugins"
+  },
+  "plugins": [
+    {
+      "name": "gstack",
+      "source": {
+        "source": "local",
+        "path": "./plugins/gstack"
+      },
+      "policy": {
+        "installation": "AVAILABLE",
+        "authentication": "ON_INSTALL"
+      },
+      "category": "Coding"
+    }
+  ]
+}
diff --git a/.gitignore b/.gitignore
index 979bc17c73..9b23488ec6 100644
--- a/.gitignore
+++ b/.gitignore
@@ -9,7 +9,10 @@ bin/gstack-global-discover
 .claude/skills/
 .claude/scheduled_tasks.lock
 .claude/*.lock
-.agents/
+.agents/*
+.agents/skills/
+!.agents/plugins/
+!.agents/plugins/**
 .factory/
 .kiro/
 .opencode/
diff --git a/README.md b/README.md
index 426c8468f3..f7bd496d94 100644
--- a/README.md
+++ b/README.md
@@ -125,6 +125,20 @@ Or target a specific agent with `./setup --host <name>`:
 **Want to add support for another agent?** See [docs/ADDING_A_HOST.md](docs/ADDING_A_HOST.md).
 It's one TypeScript config file, zero code changes.
 
+### Codex plugin marketplace (repo-local)
+
+If you want Codex to install gstack from this repository through a local plugin
+marketplace instead of `~/.codex/skills`, run:
+
+```bash
+bun run plugin:codex:prepare
+```
+
+That command regenerates the Codex-formatted skills in `.agents/skills/`,
+refreshes the repo-local runtime sidecar under `.agents/skills/gstack/`, and
+keeps `plugins/gstack` pointed at the generated skill tree. Codex can then load
+the plugin from `.agents/plugins/marketplace.json`.
+
 ## See it work
 
 ```
diff --git a/package.json b/package.json
index ba1b4f8f8c..de29439bbd 100644
--- a/package.json
+++ b/package.json
@@ -36,6 +36,7 @@
     "eval:watch": "bun run scripts/eval-watch.ts",
     "eval:select": "bun run scripts/eval-select.ts",
     "analytics": "bun run scripts/analytics.ts",
+    "plugin:codex:prepare": "bun run scripts/prepare-codex-plugin.ts",
     "test:audit": "bun test test/audit-compliance.test.ts",
     "slop": "npx slop-scan scan . 2>/dev/null || echo 'slop-scan not available (install with: npm i -g slop-scan)'",
     "slop:diff": "bun run scripts/slop-diff.ts"
diff --git a/plugins/gstack/.codex-plugin/plugin.json b/plugins/gstack/.codex-plugin/plugin.json
new file mode 100644
index 0000000000..c5b28e24a0
--- /dev/null
+++ b/plugins/gstack/.codex-plugin/plugin.json
@@ -0,0 +1,43 @@
+{
+  "name": "gstack",
+  "version": "1.21.1.0",
+  "description": "Garry's Stack \u2014 AI engineering workflows, QA, planning, and browser automation skills for Codex.",
+  "author": {
+    "name": "Garry Tan",
+    "email": "opensource@garrytan.com",
+    "url": "https://github.com/garrytan"
+  },
+  "homepage": "https://github.com/garrytan/gstack",
+  "repository": "https://github.com/garrytan/gstack",
+  "license": "MIT",
+  "keywords": [
+    "skills",
+    "codex",
+    "browser-automation",
+    "qa",
+    "planning",
+    "workflow"
+  ],
+  "skills": "./skills/",
+  "interface": {
+    "displayName": "gstack",
+    "shortDescription": "AI engineering workflows for Codex",
+    "longDescription": "Use gstack to add planning, QA, browser automation, review, deployment, and product workflow skills to Codex from this repository.",
+    "developerName": "Garry Tan",
+    "category": "Coding",
+    "capabilities": [
+      "Interactive",
+      "Read",
+      "Write"
+    ],
+    "websiteURL": "https://github.com/garrytan/gstack",
+    "privacyPolicyURL": "https://docs.github.com/en/site-policy/privacy-policies/github-general-privacy-statement",
+    "termsOfServiceURL": "https://docs.github.com/en/site-policy/github-terms/github-terms-of-service",
+    "defaultPrompt": [
+      "Run /gstack-qa against my local app and fix the bugs it finds.",
+      "Review this branch before I open a PR.",
+      "Help me plan a new feature before I start coding."
+    ],
+    "brandColor": "#2563EB"
+  }
+}
diff --git a/plugins/gstack/skills b/plugins/gstack/skills
new file mode 120000
index 0000000000..bf44df0e59
--- /dev/null
+++ b/plugins/gstack/skills
@@ -0,0 +1 @@
+../../.agents/skills
\ No newline at end of file
diff --git a/scripts/prepare-codex-plugin.ts b/scripts/prepare-codex-plugin.ts
new file mode 100644
index 0000000000..e465700335
--- /dev/null
+++ b/scripts/prepare-codex-plugin.ts
@@ -0,0 +1,80 @@
+import fs from 'node:fs';
+import path from 'node:path';
+import { fileURLToPath } from 'node:url';
+import { spawnSync } from 'node:child_process';
+
+const repoRoot = path.resolve(fileURLToPath(new URL('..', import.meta.url)));
+const agentsSkillsRoot = path.join(repoRoot, '.agents', 'skills');
+const runtimeRoot = path.join(agentsSkillsRoot, 'gstack');
+const pluginSkillsPath = path.join(repoRoot, 'plugins', 'gstack', 'skills');
+
+function run(command: string[], cwd = repoRoot): void {
+  const result = spawnSync(command[0], command.slice(1), {
+    cwd,
+    stdio: 'inherit',
+  });
+  if (result.status !== 0) {
+    process.exit(result.status ?? 1);
+  }
+}
+
+function ensureRelativeSymlink(targetPath: string, linkPath: string): void {
+  const relativeTarget = path.relative(path.dirname(linkPath), targetPath);
+  const existing = fs.existsSync(linkPath) || fs.lstatSync(linkPath, { throwIfNoEntry: false }) !== undefined;
+
+  if (existing) {
+    const stat = fs.lstatSync(linkPath);
+    if (stat.isSymbolicLink() && fs.readlinkSync(linkPath) === relativeTarget) {
+      return;
+    }
+    if (stat.isDirectory() && !stat.isSymbolicLink()) {
+      const entries = fs.readdirSync(linkPath);
+      if (entries.length > 0) {
+        throw new Error(`Refusing to replace non-empty directory: ${path.relative(repoRoot, linkPath)}`);
+      }
+      fs.rmdirSync(linkPath);
+    } else {
+      fs.rmSync(linkPath, { force: true, recursive: true });
+    }
+  }
+
+  fs.mkdirSync(path.dirname(linkPath), { recursive: true });
+  fs.symlinkSync(relativeTarget, linkPath);
+}
+
+function topLevelSkillDirs(): string[] {
+  return fs
+    .readdirSync(repoRoot, { withFileTypes: true })
+    .filter((entry) => entry.isDirectory())
+    .map((entry) => entry.name)
+    .filter((name) => !name.startsWith('.'))
+    .filter((name) => fs.existsSync(path.join(repoRoot, name, 'SKILL.md')))
+    .filter((name) => name !== 'plugins');
+}
+
+run(['bun', 'run', 'scripts/gen-skill-docs.ts', '--host', 'codex']);
+
+fs.mkdirSync(runtimeRoot, { recursive: true });
+
+const runtimeEntries = new Set<string>([
+  'bin',
+  'browse',
+  'design',
+  'extension',
+  'review',
+  'qa',
+  'make-pdf',
+  'ETHOS.md',
+  'VERSION',
+  ...topLevelSkillDirs(),
+]);
+
+for (const entry of runtimeEntries) {
+  const source = path.join(repoRoot, entry);
+  if (!fs.existsSync(source)) continue;
+  const dest = path.join(runtimeRoot, entry);
+  if (entry === 'SKILL.md' || entry === 'agents') continue;
+  ensureRelativeSymlink(source, dest);
+}
+
+ensureRelativeSymlink(agentsSkillsRoot, pluginSkillsPath);
diff --git a/test/codex-plugin-compat.test.ts b/test/codex-plugin-compat.test.ts
new file mode 100644
index 0000000000..c96001278c
--- /dev/null
+++ b/test/codex-plugin-compat.test.ts
@@ -0,0 +1,45 @@
+import fs from 'node:fs';
+import path from 'node:path';
+
+const ROOT = path.resolve(import.meta.dir, '..');
+
+test('gstack plugin manifest points Codex at the generated skills bundle', () => {
+  const pluginJson = JSON.parse(
+    fs.readFileSync(path.join(ROOT, 'plugins', 'gstack', '.codex-plugin', 'plugin.json'), 'utf8'),
+  );
+
+  expect(pluginJson.name).toBe('gstack');
+  expect(pluginJson.skills).toBe('./skills/');
+  expect(pluginJson.interface.displayName).toBe('gstack');
+  expect(pluginJson.interface.category).toBe('Coding');
+});
+
+test('repo-local marketplace publishes the gstack plugin entry', () => {
+  const marketplace = JSON.parse(
+    fs.readFileSync(path.join(ROOT, '.agents', 'plugins', 'marketplace.json'), 'utf8'),
+  );
+
+  expect(marketplace.name).toBe('gstack-local');
+  expect(marketplace.plugins).toEqual([
+    {
+      name: 'gstack',
+      source: {
+        source: 'local',
+        path: './plugins/gstack',
+      },
+      policy: {
+        installation: 'AVAILABLE',
+        authentication: 'ON_INSTALL',
+      },
+      category: 'Coding',
+    },
+  ]);
+});
+
+test('plugin skills directory resolves to the generated Codex skill tree', () => {
+  const skillsPath = path.join(ROOT, 'plugins', 'gstack', 'skills');
+  const stat = fs.lstatSync(skillsPath);
+
+  expect(stat.isSymbolicLink()).toBe(true);
+  expect(fs.readlinkSync(skillsPath)).toBe('../../.agents/skills');
+});