diff --git a/.claude-plugin/marketplace.json b/.claude-plugin/marketplace.json
new file mode 100644
index 0000000..753b72a
--- /dev/null
+++ b/.claude-plugin/marketplace.json
@@ -0,0 +1,18 @@
+{
+  "$schema": "https://json.schemastore.org/claude-code-marketplace.json",
+  "name": "harness",
+  "owner": {
+    "name": "coderloganli",
+    "email": "coder_logan_li@outlook.com"
+  },
+  "plugins": [
+    {
+      "name": "harness",
+      "source": "./",
+      "description": "Governs a project's documents, a task's workspace, and the ten stages a task passes through.",
+      "version": "0.2.0",
+      "license": "MIT",
+      "keywords": ["workflow", "worktree", "adr", "documentation", "code-review"]
+    }
+  ]
+}
diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
new file mode 100644
index 0000000..c3d08ff
--- /dev/null
+++ b/.github/workflows/test.yml
@@ -0,0 +1,27 @@
+name: test
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+
+jobs:
+  test:
+    # The harness resolves workspaces, worktrees and repository paths itself, and
+    # the one refusal is a path comparison. Windows is in the matrix because that
+    # is where a path bug would appear first.
+    runs-on: ${{ matrix.os }}
+    strategy:
+      fail-fast: false
+      matrix:
+        os: [ubuntu-latest, windows-latest]
+        node: ['20', '22']
+
+    steps:
+      - uses: actions/checkout@v7
+
+      - uses: actions/setup-node@v7
+        with:
+          node-version: ${{ matrix.node }}
+
+      - run: npm test
diff --git a/README.md b/README.md
index c10bfe8..b1930c1 100644
--- a/README.md
+++ b/README.md
@@ -1,5 +1,7 @@
 # Claude Code Harness
 
+[![test](https://github.com/coderloganli/dev-harness/actions/workflows/test.yml/badge.svg)](https://github.com/coderloganli/dev-harness/actions/workflows/test.yml)
+
 A harness for Claude Code: it makes Claude build software the way a careful engineer
 does — read the design first, agree it before writing code, write the failing test
 before the feature, work in a scratch space that cannot damage anything, and keep
@@ -16,7 +18,7 @@ It governs three things, and they are independent of each other:
 
 > **Status: early.** The harness has been through one real task — its own, fixing
 > five defects that its first run exposed — and the ten stages, the refusal and the
-> approval dialogs all held. There is no marketplace entry yet.
+> approval dialogs all held.
 
 ## Why
 
@@ -112,6 +114,19 @@ session it was worked in. Weeks later, ask for "that task about search ranking"
 one was recorded — a task whose session was not says so, rather than offering a
 resume that goes nowhere.
 
+## Installing
+
+The repository is its own marketplace, so adding it and installing from it are two
+lines in Claude Code:
+
+```
+/plugin marketplace add coderloganli/dev-harness
+/plugin install harness@harness
+```
+
+If the install summary says `Run /reload-plugins to activate.`, run that too. To pick
+up a later version, `/plugin marketplace update harness`.
+
 ## Getting started
 
 ```
diff --git a/docs/architecture.md b/docs/architecture.md
index ba016a1..70b1257 100644
--- a/docs/architecture.md
+++ b/docs/architecture.md
@@ -26,6 +26,12 @@ something a hook can do.
 | **Templates** | Skeletons for the documents `init` creates |
 | **Project config** | A few facts about one project |
 
+The repository is also its own marketplace: `.claude-plugin/marketplace.json` lists
+one plugin whose source is the repository root, so `/plugin marketplace add` and
+`/plugin install` reach it without a second repository to keep in step. Its `version`
+is what tells an installed copy that a newer one exists, so it moves with
+`plugin.json`'s.
+
 The line that matters: **a skill is text Claude may or may not follow; the server
 and the hooks are programs that run either way.** Every rule below is placed on one
 side of that line on purpose.
diff --git a/package.json b/package.json
new file mode 100644
index 0000000..8f64605
--- /dev/null
+++ b/package.json
@@ -0,0 +1,14 @@
+{
+  "name": "claude-code-harness",
+  "version": "0.2.0",
+  "private": true,
+  "description": "Governs a project's documents, a task's workspace, and the ten stages a task passes through.",
+  "license": "MIT",
+  "type": "module",
+  "engines": {
+    "node": ">=20"
+  },
+  "scripts": {
+    "test": "node --test"
+  }
+}
diff --git a/test/conventions.test.mjs b/test/conventions.test.mjs
index 7ba6d5f..0185724 100644
--- a/test/conventions.test.mjs
+++ b/test/conventions.test.mjs
@@ -1,4 +1,4 @@
-// Test cases 9-11: conventions the plugin states about itself, asserted against the
+// Test cases 9-11 and 38: conventions the plugin states about itself, asserted against the
 // repository so that a fix cannot look done while a stale copy survives somewhere.
 
 import assert from 'node:assert/strict';
@@ -65,3 +65,24 @@ test('11 — one product document, under 200 lines', () => {
     'nothing should still link to docs/prd.md',
   );
 });
+
+test('38 — one version, declared in three files, and an install line that reaches it', () => {
+  const plugin = JSON.parse(read('.claude-plugin/plugin.json'));
+  const marketplace = JSON.parse(read('.claude-plugin/marketplace.json'));
+  const pkg = JSON.parse(read('package.json'));
+
+  // The marketplace version is what tells an installed copy a newer one exists. A
+  // release that bumps plugin.json alone ships to nobody, and nothing at runtime
+  // would say so.
+  const entry = marketplace.plugins.find((p) => p.name === plugin.name);
+  assert.ok(entry, `marketplace.json must list a plugin named ${plugin.name}`);
+  assert.equal(entry.version, plugin.version, 'the marketplace entry must carry the plugin.json version');
+  assert.equal(pkg.version, plugin.version, 'package.json must carry the plugin.json version');
+
+  // README tells the user to type `/plugin install <plugin>@<marketplace>`.
+  assert.match(
+    read('README.md'),
+    new RegExp(`/plugin install ${plugin.name}@${marketplace.name}\\b`),
+    'the README install line must name the plugin and the marketplace as they are declared',
+  );
+});