diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 1956421..ec250b1 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -3,6 +3,7 @@ name: CI
 on:
   push:
     branches: [main]
+    tags: ["v*"]
   pull_request:
 
 jobs:
@@ -18,3 +19,24 @@ jobs:
           python-version: ${{ matrix.python-version }}
       - run: pip install -e ".[dev]"
       - run: pytest tests/ -v
+
+  # The package version and the git tag drifted for three releases: tags said 1.x
+  # while pyproject said 0.1.0. This fails the tag build rather than shipping a
+  # release that misreports itself.
+  version-matches-tag:
+    if: startsWith(github.ref, 'refs/tags/v')
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-python@v5
+        with:
+          python-version: "3.13"
+      - name: Compare __version__ with the tag
+        run: |
+          tag="${GITHUB_REF_NAME#v}"
+          pkg=$(python -c "import sys; sys.path.insert(0, 'src'); import algolia_agent; print(algolia_agent.__version__)")
+          echo "tag=$tag  __version__=$pkg"
+          if [ "$tag" != "$pkg" ]; then
+            echo "::error::tag ${GITHUB_REF_NAME} does not match __version__ ${pkg}"
+            exit 1
+          fi
diff --git a/README.md b/README.md
index 8a13c24..fbce3b6 100644
--- a/README.md
+++ b/README.md
@@ -40,6 +40,21 @@ algolia-agent delete <agent_id> --confirm
 ```
 
 Add `--json` to any command except `init` for machine-readable output.
+`algolia-agent --version` reports the installed version.
+
+## Releasing
+
+`src/algolia_agent/__init__.py` holds `__version__` and everything derives from it:
+`pyproject.toml` reads it via `[tool.setuptools.dynamic]`, `--version` reports it, and
+the client sends it in the `User-Agent`. To cut a release, bump that one value, merge,
+then tag from `main`:
+
+```bash
+git checkout main && git pull
+git tag vX.Y.Z && git push origin vX.Y.Z
+```
+
+CI fails the tag build if the tag and `__version__` disagree.
 
 ## Config formats
 
diff --git a/pyproject.toml b/pyproject.toml
index e19faf9..8f91bf9 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -4,7 +4,7 @@ build-backend = "setuptools.build_meta"
 
 [project]
 name = "algolia-agent"
-version = "0.1.0"
+dynamic = ["version"]
 description = "CLI for Algolia Agent Studio"
 readme = "README.md"
 requires-python = ">=3.10"
@@ -23,6 +23,9 @@ dev = ["pytest>=7"]
 [project.scripts]
 algolia-agent = "algolia_agent.cli:main"
 
+[tool.setuptools.dynamic]
+version = { attr = "algolia_agent.__version__" }
+
 [tool.setuptools.packages.find]
 where = ["src"]
 
diff --git a/src/algolia_agent/__init__.py b/src/algolia_agent/__init__.py
index e69de29..e7aa3e6 100644
--- a/src/algolia_agent/__init__.py
+++ b/src/algolia_agent/__init__.py
@@ -0,0 +1,7 @@
+"""CLI for the Algolia Agent Studio REST API."""
+
+# Single source of truth for the version. pyproject.toml reads it via
+# [tool.setuptools.dynamic], the CLI reports it through --version, and the client
+# sends it in the User-Agent — so a release cannot disagree with itself. CI checks
+# this value against the git tag whenever a v* tag is pushed.
+__version__ = "1.3.0"
diff --git a/src/algolia_agent/cli.py b/src/algolia_agent/cli.py
index 0ad528e..377abc3 100644
--- a/src/algolia_agent/cli.py
+++ b/src/algolia_agent/cli.py
@@ -21,6 +21,7 @@
 
 from InquirerPy import inquirer
 
+from . import __version__
 from .client import AgentAPIError, AlgoliaAgentClient
 from .template import extract_variables, render
 
@@ -1180,6 +1181,8 @@ def build_parser() -> argparse.ArgumentParser:
         prog="algolia-agent",
         description="Algolia Agent Studio CLI",
     )
+    parser.add_argument("--version", action="version",
+                        version=f"algolia-agent {__version__}")
     parser.add_argument("--app-id", help="Algolia Application ID (overrides env/dotenv)")
     parser.add_argument("--api-key", help="Algolia API Key (overrides env/dotenv)")
 
diff --git a/src/algolia_agent/client.py b/src/algolia_agent/client.py
index 3f7b5ea..ac75d43 100644
--- a/src/algolia_agent/client.py
+++ b/src/algolia_agent/client.py
@@ -19,6 +19,11 @@
 _RETRY_BACKOFF = 1.0   # seconds; doubles each retry
 
 
+from . import __version__
+
+_USER_AGENT = f"algolia-agent-cli/{__version__}"
+
+
 def _load_dotenv(path: Path) -> dict[str, str]:
     """Parse a .env file and return key/value pairs. Ignores comments and blank lines."""
     result = {}
@@ -66,7 +71,7 @@ def _request(self, path: str, method: str = "GET", body: dict | None = None) ->
         req.add_header("x-algolia-api-key", self.api_key)
         req.add_header("Content-Type", "application/json")
         req.add_header("Accept", "application/json")
-        req.add_header("User-Agent", "algolia-agent-cli/0.1.0")
+        req.add_header("User-Agent", _USER_AGENT)
         delay = _RETRY_BACKOFF
         for attempt in range(_MAX_RETRIES):
             try:
@@ -151,7 +156,7 @@ def list_indices(self) -> list[str]:
         req.add_header("x-algolia-application-id", self.app_id)
         req.add_header("x-algolia-api-key", self.api_key)
         req.add_header("Accept", "application/json")
-        req.add_header("User-Agent", "algolia-agent-cli/0.1.0")
+        req.add_header("User-Agent", _USER_AGENT)
         try:
             with urllib.request.urlopen(req, timeout=_TIMEOUT) as resp:
                 result = json.loads(resp.read())
diff --git a/tests/test_client.py b/tests/test_client.py
index 920615e..3853066 100644
--- a/tests/test_client.py
+++ b/tests/test_client.py
@@ -384,3 +384,38 @@ def test_timeout_error_retries_then_succeeds(client):
         with patch("time.sleep"):
             result = client.get_agent("abc")
     assert result == agent
+
+
+# ── version reporting ─────────────────────────────────────────────────────────
+
+def test_user_agent_reports_the_package_version():
+    """The User-Agent was frozen at 0.1.0 through three tagged releases."""
+    import re
+
+    import algolia_agent
+    from algolia_agent.client import _USER_AGENT
+
+    assert re.fullmatch(r"\d+\.\d+\.\d+", algolia_agent.__version__), algolia_agent.__version__
+    assert _USER_AGENT == f"algolia-agent-cli/{algolia_agent.__version__}"
+
+
+def test_user_agent_header_is_actually_sent(client):
+    import algolia_agent
+
+    with patch("urllib.request.urlopen", return_value=_mock_response({"data": []})) as m:
+        client.list_agents()
+    req = m.call_args.args[0]
+    assert req.get_header("User-agent") == f"algolia-agent-cli/{algolia_agent.__version__}"
+
+
+def test_installed_metadata_matches_dunder_version():
+    """pyproject reads the version from the package, so these cannot diverge."""
+    from importlib.metadata import PackageNotFoundError, version
+
+    import algolia_agent
+
+    try:
+        installed = version("algolia-agent")
+    except PackageNotFoundError:
+        pytest.skip("package not installed")
+    assert installed == algolia_agent.__version__