diff --git a/README.md b/README.md
index 0c51132..e94a336 100644
--- a/README.md
+++ b/README.md
@@ -155,9 +155,10 @@ an edge table only when hop depth or corpus size demands it.
 - No incremental indexing (tracked in the issues). Packaging exists since v0.3.0 (`pip install sqlite-graph-memory`). There IS an eval suite now — see
   [Measure before you swap](#measure-before-you-swap--eval) — but it scores retrieval on
   wikilink-derived gold, which is weak supervision and says so out loud. Test coverage is uneven:
-  `index_notes.py`, `brain_ask.py` and `mcp_server.py` have unit tests, `turnstate_hook.py`
-  has none. Run `pytest -q` for the current count rather than trusting a number written in
-  prose here — that is how this file ended up claiming "no tests" while seven were passing.
+  `index_notes.py`, `brain_ask.py` and `mcp_server.py` have unit tests, and
+  `turnstate_hook.py` has write-path coverage. Run `pytest -q` for the current count rather
+  than trusting a number written in prose here — that is how this file ended up claiming
+  "no tests" while seven were passing.
   The status line above says **pilot** on purpose.
 
 ## Quickstart
diff --git a/tests/test_turnstate_hook.py b/tests/test_turnstate_hook.py
new file mode 100644
index 0000000..b306eec
--- /dev/null
+++ b/tests/test_turnstate_hook.py
@@ -0,0 +1,126 @@
+"""Tests for the Stop hook's per-turn SQLite ledger write path."""
+import io
+import json
+import os
+import sqlite3
+import subprocess
+import sys
+import tempfile
+from pathlib import Path
+
+ROOT = Path(__file__).resolve().parents[1]
+sys.path.insert(0, str(ROOT / "src"))
+
+from sqlite_graph_memory import turnstate_hook  # noqa: E402
+
+
+class _Stdin:
+    def __init__(self, payload):
+        self.buffer = io.BytesIO(payload)
+
+
+def _event(kind, content):
+    return {"type": kind, "message": {"content": content}}
+
+
+def _run_hook(monkeypatch, payload):
+    monkeypatch.setattr(turnstate_hook.sys, "stdin", _Stdin(json.dumps(payload).encode()))
+    turnstate_hook.main()
+
+
+def test_main_writes_extracted_turn_to_ledger(tmp_path, monkeypatch):
+    db_path = tmp_path / "turns.db"
+    cwd = tmp_path / "my-project"
+    cwd.mkdir()
+    transcript_path = tmp_path / "transcript.jsonl"
+    events = [
+        _event("user", "How should we test the ledger write path?"),
+        _event("assistant", [
+            {"type": "text", "text": "Decision: we will write one pytest file."},
+            {"type": "tool_use", "name": "Write",
+             "input": {"file_path": str(cwd / "test_turnstate_hook.py")}},
+            {"type": "tool_use", "name": "Bash",
+             "input": {"command": "python -m pytest -q"}},
+        ]),
+    ]
+    transcript_path.write_text(
+        "\n".join(json.dumps(event) for event in events) + "\n", encoding="utf-8")
+
+    monkeypatch.setenv("TURNSTATE_DB", str(db_path))
+    monkeypatch.setattr(tempfile, "tempdir", str(tmp_path))
+    _run_hook(monkeypatch, {
+        "session_id": "test-session",
+        "transcript_path": str(transcript_path),
+        "cwd": str(cwd),
+    })
+
+    with sqlite3.connect(db_path) as con:
+        row = con.execute(
+            "SELECT ask, files, tools, commands, decisions, project FROM turns"
+        ).fetchone()
+
+    assert row is not None
+    ask, files, tools, commands, decisions, project = row
+    assert ask == "How should we test the ledger write path?"
+    assert json.loads(files) == [str(cwd / "test_turnstate_hook.py")]
+    assert json.loads(tools) == ["Write", "Bash"]
+    assert json.loads(commands) == ["python -m pytest -q"]
+    assert json.loads(decisions) == ["Decision: we will write one pytest file."]
+    assert project == "my-project"
+
+
+def test_main_does_not_write_again_without_new_transcript_bytes(tmp_path, monkeypatch):
+    db_path = tmp_path / "turns.db"
+    transcript_path = tmp_path / "transcript.jsonl"
+    transcript_path.write_text(
+        json.dumps(_event("user", "Record this turn in the ledger.")) + "\n",
+        encoding="utf-8")
+    payload = {
+        "session_id": "repeat-session",
+        "transcript_path": str(transcript_path),
+        "cwd": str(tmp_path),
+    }
+    monkeypatch.setenv("TURNSTATE_DB", str(db_path))
+    monkeypatch.setattr(tempfile, "tempdir", str(tmp_path))
+
+    _run_hook(monkeypatch, payload)
+    _run_hook(monkeypatch, payload)
+
+    with sqlite3.connect(db_path) as con:
+        count = con.execute("SELECT COUNT(*) FROM turns").fetchone()[0]
+    assert count == 1
+
+
+def test_module_wrapper_exits_successfully_on_bad_input(tmp_path):
+    env = os.environ.copy()
+    env["PYTHONPATH"] = str(ROOT / "src")
+    env["TURNSTATE_DB"] = str(tmp_path / "turns.db")
+    result = subprocess.run(
+        [sys.executable, "-m", "sqlite_graph_memory.turnstate_hook"],
+        input=b"not json",
+        capture_output=True,
+        cwd=ROOT,
+        env=env,
+        check=False,
+    )
+    assert result.returncode == 0
+
+
+def test_module_wrapper_exits_successfully_when_transcript_is_missing(tmp_path):
+    env = os.environ.copy()
+    env["PYTHONPATH"] = str(ROOT / "src")
+    env["TURNSTATE_DB"] = str(tmp_path / "turns.db")
+    payload = {
+        "session_id": "missing-session",
+        "transcript_path": str(tmp_path / "missing.jsonl"),
+        "cwd": str(tmp_path),
+    }
+    result = subprocess.run(
+        [sys.executable, "-m", "sqlite_graph_memory.turnstate_hook"],
+        input=json.dumps(payload).encode(),
+        capture_output=True,
+        cwd=ROOT,
+        env=env,
+        check=False,
+    )
+    assert result.returncode == 0