diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
new file mode 100644
index 0000000..ca5e237
--- /dev/null
+++ b/.github/workflows/ci.yml
@@ -0,0 +1,71 @@
+name: CI
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+    branches: [main]
+  workflow_dispatch:
+
+# Cancel superseded runs on the same branch/PR (e.g. rapid pushes).
+concurrency:
+  group: ci-${{ github.ref }}
+  cancel-in-progress: true
+
+permissions:
+  contents: read
+
+jobs:
+  backend-tests:
+    name: Backend tests (Python ${{ matrix.python-version }})
+    runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        # pyproject says requires-python ">=3.12", but the pinned
+        # memu-py==1.4.0 dependency requires >=3.13, so 3.13 is the real
+        # floor (and what the dev environment runs). Add more versions here
+        # if that pin is ever relaxed.
+        python-version: ["3.13"]
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v5
+
+      - name: Set up uv
+        uses: astral-sh/setup-uv@v6
+        with:
+          enable-cache: true
+          # Key the uv cache on the dependency source (this repo has no uv.lock).
+          cache-dependency-glob: "pyproject.toml"
+
+      - name: Create virtual environment
+        run: uv venv --python ${{ matrix.python-version }}
+
+      - name: Install project and test dependencies
+        run: uv pip install -e ".[test]"
+
+      - name: Run test suite
+        run: .venv/bin/pytest tests/ -v
+
+  frontend-build:
+    name: Frontend build (Vite)
+    runs-on: ubuntu-latest
+    defaults:
+      run:
+        working-directory: web
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v5
+
+      - name: Set up Node.js
+        uses: actions/setup-node@v5
+        with:
+          node-version: "22"
+          cache: npm
+          cache-dependency-path: web/package-lock.json
+
+      - name: Install dependencies
+        run: npm ci
+
+      - name: Build frontend (tsc -b && vite build)
+        run: npm run build
diff --git a/.gitignore b/.gitignore
index cc1ec04..002a57c 100644
--- a/.gitignore
+++ b/.gitignore
@@ -45,6 +45,8 @@ nerve.pid
 # Sync data
 sync_data/
 *.jsonl
+# ...except checked-in test fixtures, which the suite needs on a clean checkout
+!tests/fixtures/**/*.jsonl
 
 # Docker (generated by 'nerve init' — safe to commit if sharing)
 Dockerfile
diff --git a/pyproject.toml b/pyproject.toml
index 332c7ea..9dc6432 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -36,6 +36,15 @@ dependencies = [
     "opentelemetry-instrumentation-anthropic>=0.40.0",
 ]
 
+[project.optional-dependencies]
+# Test/dev dependencies. Install with: uv pip install -e ".[test]"
+# Upper bounds guard CI against surprise major-version breaks (notably the
+# pytest-asyncio 1.x event_loop changes the suite's conftest relies on).
+test = [
+    "pytest>=8,<10",
+    "pytest-asyncio>=0.24,<2",
+]
+
 [project.scripts]
 nerve = "nerve.cli:main"
 
diff --git a/tests/fixtures/codex/rollouts/in_scope.jsonl b/tests/fixtures/codex/rollouts/in_scope.jsonl
new file mode 100644
index 0000000..ce8743b
--- /dev/null
+++ b/tests/fixtures/codex/rollouts/in_scope.jsonl
@@ -0,0 +1,13 @@
+{"timestamp":"2026-05-19T16:52:04.073Z","type":"session_meta","payload":{"id":"11111111-2222-3333-4444-555555555555","timestamp":"2026-05-19T16:52:02.403Z","cwd":"/tmp/nerve-test-ws","originator":"codex_exec","cli_version":"0.130.0","source":"exec","model_provider":"openai","base_instructions":{"text":"You are Codex, a fixture."}}}
+{"timestamp":"2026-05-19T16:52:04.075Z","type":"event_msg","payload":{"type":"task_started","turn_id":"turn-1","started_at":1779209522,"model_context_window":258400}}
+{"timestamp":"2026-05-19T16:52:04.076Z","type":"response_item","payload":{"type":"message","role":"developer","content":[{"type":"input_text","text":"system instructions to ignore"}]}}
+{"timestamp":"2026-05-19T16:52:04.077Z","type":"response_item","payload":{"type":"message","role":"user","content":[{"type":"input_text","text":"AGENTS.md auto-injection — should be dropped"}]}}
+{"timestamp":"2026-05-19T16:52:04.080Z","type":"turn_context","payload":{"turn_id":"turn-1","cwd":"/tmp/nerve-test-ws","model":"gpt-5.5"}}
+{"timestamp":"2026-05-19T16:52:04.081Z","type":"event_msg","payload":{"type":"user_message","message":"hello fixture","images":[],"local_images":[],"text_elements":[]}}
+{"timestamp":"2026-05-19T16:52:04.090Z","type":"response_item","payload":{"type":"reasoning","encrypted_content":"ENCRYPTED-BLOB-PLACEHOLDER","summary":[]}}
+{"timestamp":"2026-05-19T16:52:04.100Z","type":"response_item","payload":{"type":"function_call","name":"exec_command","arguments":"{\"cmd\":\"ls\"}","call_id":"call_exec_1"}}
+{"timestamp":"2026-05-19T16:52:04.110Z","type":"response_item","payload":{"type":"function_call_output","call_id":"call_exec_1","output":"Chunk ID: abc123\nWall time: 0.1234 seconds\nProcess exited with code 0\nOutput:\nfile1\nfile2\n"}}
+{"timestamp":"2026-05-19T16:52:04.120Z","type":"response_item","payload":{"type":"function_call","name":"task_list","namespace":"mcp__nerve__","arguments":"{\"limit\":3}","call_id":"call_mcp_1"}}
+{"timestamp":"2026-05-19T16:52:04.130Z","type":"event_msg","payload":{"type":"mcp_tool_call_end","call_id":"call_mcp_1","invocation":{"server":"nerve","tool":"task_list","arguments":{"limit":3}},"duration":{"secs":0,"nanos":1000},"result":{"Ok":"task list output here"}}}
+{"timestamp":"2026-05-19T16:52:04.140Z","type":"event_msg","payload":{"type":"agent_message","message":"final reply","phase":"final_answer"}}
+{"timestamp":"2026-05-19T16:52:04.150Z","type":"event_msg","payload":{"type":"task_complete","turn_id":"turn-1","last_agent_message":"final reply","completed_at":1779209524,"duration_ms":1450}}
diff --git a/tests/fixtures/codex/rollouts/out_of_scope.jsonl b/tests/fixtures/codex/rollouts/out_of_scope.jsonl
new file mode 100644
index 0000000..95c84e1
--- /dev/null
+++ b/tests/fixtures/codex/rollouts/out_of_scope.jsonl
@@ -0,0 +1,3 @@
+{"timestamp":"2026-05-19T17:00:00.000Z","type":"session_meta","payload":{"id":"99999999-aaaa-bbbb-cccc-dddddddddddd","timestamp":"2026-05-19T17:00:00.000Z","cwd":"/tmp/some-other-project","originator":"codex_exec","cli_version":"0.130.0","source":"exec","model_provider":"openai","base_instructions":{"text":""}}}
+{"timestamp":"2026-05-19T17:00:01.000Z","type":"event_msg","payload":{"type":"user_message","message":"this thread is not in scope — must be skipped"}}
+{"timestamp":"2026-05-19T17:00:02.000Z","type":"event_msg","payload":{"type":"agent_message","message":"agent reply we should NOT ingest","phase":"final_answer"}}
diff --git a/tests/fixtures/codex/rollouts/partial_tail.jsonl b/tests/fixtures/codex/rollouts/partial_tail.jsonl
new file mode 100644
index 0000000..c6d7116
--- /dev/null
+++ b/tests/fixtures/codex/rollouts/partial_tail.jsonl
@@ -0,0 +1,4 @@
+{"timestamp":"2026-05-19T18:00:00.000Z","type":"session_meta","payload":{"id":"22222222-3333-4444-5555-666666666666","cwd":"/tmp/nerve-test-ws","originator":"codex_tui","cli_version":"0.130.0","source":"tui","model_provider":"openai","base_instructions":{"text":""}}}
+{"timestamp":"2026-05-19T18:00:01.000Z","type":"event_msg","payload":{"type":"user_message","message":"first complete line"}}
+{"timestamp":"2026-05-19T18:00:02.000Z","type":"event_msg","payload":{"type":"agent_message","message":"second complete","phase":"final_answer"}}
+{"timestamp":"2026-05-19T18:00:03.000Z","type":"event_msg","payload":{"type":"user_message","message":"third incomplete
\ No newline at end of file