diff --git a/tests/integration/test_setup_live.py b/tests/integration/test_setup_live.py
new file mode 100644
index 0000000..4fdbbdc
--- /dev/null
+++ b/tests/integration/test_setup_live.py
@@ -0,0 +1,125 @@
+"""The ``aegis-gitea-mcp setup`` command against the live instance."""
+
+from __future__ import annotations
+
+import os
+import stat
+import subprocess
+import sys
+from pathlib import Path
+
+from aegis_gitea_mcp.config import Settings
+from aegis_gitea_mcp.setup_cmd import OAUTH_APP_NAME, parse_env_text
+from tests.integration.conftest import RegularUser
+from tests.integration.harness import GiteaInstance
+
+PUBLIC_URL = "https://mcp.example.test"
+REDIRECT_URI = f"{PUBLIC_URL}/oauth/callback"
+SECRET_KEYS = (
+    "GITEA_TOKEN",
+    "MCP_BEARER_TOKEN",
+    "TOKEN_ENCRYPTION_KEY",
+    "GITEA_OAUTH_CLIENT_SECRET",
+)
+_PASSTHROUGH_ENV = ("PATH", "HOME", "LANG", "LC_ALL", "TMPDIR")
+
+
+def run_setup(
+    gitea: GiteaInstance, token: str, env_file: Path, cwd: Path
+) -> subprocess.CompletedProcess[str]:
+    """Run the setup command in a subprocess; the Gitea token goes in the environment only."""
+    env = {name: os.environ[name] for name in _PASSTHROUGH_ENV if name in os.environ}
+    env["GITEA_TOKEN"] = token
+    return subprocess.run(  # noqa: S603
+        [
+            sys.executable,
+            "-m",
+            "aegis_gitea_mcp.cli",
+            "setup",
+            "--gitea-url",
+            gitea.base_url,
+            "--public-base-url",
+            PUBLIC_URL,
+            "--env-file",
+            str(env_file),
+            "--yes",
+        ],
+        capture_output=True,
+        text=True,
+        timeout=120,
+        check=False,
+        env=env,
+        cwd=cwd,
+    )
+
+
+def oauth_apps(gitea: GiteaInstance) -> list[dict[str, object]]:
+    """The admin's OAuth2 applications named like the one setup registers."""
+    response = gitea.api("GET", "/user/applications/oauth2", params={"limit": 50})
+    assert response.status_code == 200
+    return [app for app in response.json() if app["name"] == OAUTH_APP_NAME]
+
+
+def read_env(path: Path) -> dict[str, str]:
+    """Key/value pairs of an env file."""
+    return {key: entry.value for key, entry in parse_env_text(path.read_text("utf-8")).items()}
+
+
+def test_setup_registers_the_oauth_app_and_writes_a_private_env_file(
+    gitea: GiteaInstance, tmp_path: Path
+) -> None:
+    env_file = tmp_path / ".env"
+    assert oauth_apps(gitea) == []
+
+    first = run_setup(gitea, gitea.admin_token, env_file, tmp_path)
+    assert first.returncode == 0, first.stderr
+    assert "setup failed" not in first.stderr
+
+    # The OAuth2 application exists with the callback of the public URL.
+    apps = oauth_apps(gitea)
+    assert len(apps) == 1
+    assert apps[0]["redirect_uris"] == [REDIRECT_URI]
+    assert apps[0]["confidential_client"] is True
+
+    # The env file is private, complete and loads without errors.
+    assert stat.S_IMODE(env_file.stat().st_mode) == 0o600
+    values = read_env(env_file)
+    assert values["GITEA_URL"] == gitea.base_url
+    assert values["PUBLIC_BASE_URL"] == PUBLIC_URL
+    assert values["OAUTH_ENABLED"] == "true"
+    assert values["GITEA_OAUTH_CLIENT_ID"] == apps[0]["client_id"]
+    settings = Settings(_env_file=str(env_file))  # type: ignore[call-arg]
+    assert settings.oauth_enabled
+    assert settings.oauth_config_errors() == []
+    assert settings.gitea_token is not None
+    assert settings.gitea_token.get_secret_value() == gitea.admin_token
+    assert settings.mcp_bearer_token is not None
+
+    # No secret value reaches stdout or stderr.
+    for key in SECRET_KEYS:
+        assert values[key], key
+        assert values[key] not in first.stdout, f"{key} leaked to stdout"
+        assert values[key] not in first.stderr, f"{key} leaked to stderr"
+    assert gitea.admin_token not in first.stdout + first.stderr
+
+    # Running it again is idempotent: same app, same secrets, no duplicate.
+    second = run_setup(gitea, gitea.admin_token, env_file, tmp_path)
+    assert second.returncode == 0, second.stderr
+    assert len(oauth_apps(gitea)) == 1
+    assert read_env(env_file) == values
+    assert stat.S_IMODE(env_file.stat().st_mode) == 0o600
+    for key in SECRET_KEYS:
+        assert values[key] not in second.stdout + second.stderr
+
+
+def test_setup_with_a_non_admin_token_fails_with_an_actionable_message(
+    gitea: GiteaInstance, regular_user: RegularUser, tmp_path: Path
+) -> None:
+    env_file = tmp_path / "non-admin.env"
+    result = run_setup(gitea, regular_user.token, env_file, tmp_path)
+
+    assert result.returncode == 1
+    assert "not a site administrator" in result.stderr
+    assert "Generate New Token" in result.stderr
+    assert not env_file.exists()
+    assert regular_user.token not in result.stdout + result.stderr