fix(kanban): refuse corrupt db auto-init

hermes_cli/kanban_db.py

@@ -75,6 +75,7 @@ import json
 import os
 import re
 import secrets
+import shutil
 import sqlite3
 import subprocess
 import sys
@@ -82,6 +83,7 @@ import threading
 import logging
 import time
 from dataclasses import dataclass, field
+from datetime import datetime
 from pathlib import Path
 from typing import Any, Iterable, Optional
 
@@ -1005,6 +1007,97 @@ def _validate_sqlite_header(path: Path) -> None:
     )
 
 
+class KanbanDbCorruptError(RuntimeError):
+    """Raised when an existing kanban DB file fails integrity checks.
+
+    Fail-closed guard against silent recreation of a corrupt board file,
+    which would otherwise destroy the user's tasks. Carries both the
+    original path and the timestamped backup we made before refusing.
+    """
+
+    def __init__(self, db_path: Path, backup_path: Optional[Path], reason: str):
+        self.db_path = db_path
+        self.backup_path = backup_path
+        self.reason = reason
+        backup_str = str(backup_path) if backup_path is not None else "<backup failed>"
+        super().__init__(
+            f"Refusing to open corrupt kanban DB at {db_path}: {reason}. "
+            f"Original preserved; backup at {backup_str}."
+        )
+
+
+def _backup_corrupt_db(path: Path) -> Optional[Path]:
+    """Copy a corrupt DB (and its WAL/SHM sidecars) to a timestamped backup.
+
+    Returns the backup path of the main DB file, or ``None`` if the copy
+    itself failed (the caller still raises loudly in that case).
+    """
+    stamp = datetime.now().strftime("%Y%m%d_%H%M%S")
+    candidate = path.with_name(f"{path.name}.corrupt.{stamp}.bak")
+    counter = 0
+    while candidate.exists():
+        counter += 1
+        candidate = path.with_name(
+            f"{path.name}.corrupt.{stamp}.{counter}.bak"
+        )
+    try:
+        shutil.copy2(path, candidate)
+    except OSError:
+        return None
+    for suffix in ("-wal", "-shm"):
+        sidecar = path.with_name(path.name + suffix)
+        if sidecar.exists():
+            try:
+                shutil.copy2(sidecar, candidate.with_name(candidate.name + suffix))
+            except OSError:
+                pass
+    return candidate
+
+
+def _guard_existing_db_is_healthy(path: Path) -> None:
+    """Run ``PRAGMA integrity_check`` on an existing non-empty DB file.
+
+    Opens the probe in read/write mode so SQLite can recover or
+    checkpoint a healthy WAL/hot-journal DB before we declare it
+    corrupt. If the file is malformed, copy it (and any WAL/SHM
+    sidecars) to a timestamped backup and raise
+    :class:`KanbanDbCorruptError` so callers cannot silently recreate
+    the schema on top of a damaged DB.
+
+    Transient lock/busy errors (``sqlite3.OperationalError``) are NOT
+    treated as corruption; they propagate raw so the caller sees a
+    normal lock failure and no spurious ``.corrupt`` backup is made.
+
+    No-op for missing files, zero-byte files (treated as fresh), and
+    paths already proven healthy this process (cache hit).
+    """
+    try:
+        if not path.exists() or path.stat().st_size == 0:
+            return
+    except OSError:
+        return
+    if str(path.resolve()) in _INITIALIZED_PATHS:
+        return
+    reason: Optional[str] = None
+    try:
+        probe = sqlite3.connect(str(path), timeout=5, isolation_level=None)
+        try:
+            row = probe.execute("PRAGMA integrity_check").fetchone()
+        finally:
+            probe.close()
+        if not row or (row[0] or "").lower() != "ok":
+            reason = f"integrity_check returned {row[0] if row else '<no row>'!r}"
+    except sqlite3.OperationalError:
+        # Lock contention, busy, transient IO — not corruption. Let it propagate.
+        raise
+    except sqlite3.DatabaseError as exc:
+        reason = f"sqlite refused to open file: {exc}"
+    if reason is None:
+        return
+    backup = _backup_corrupt_db(path)
+    raise KanbanDbCorruptError(path, backup, reason)
+
+
 def connect(
     db_path: Optional[Path] = None,
     *,
@@ -1033,7 +1126,13 @@ def connect(
     else:
         path = kanban_db_path(board=board)
     path.parent.mkdir(parents=True, exist_ok=True)
+    # Cheap byte-level check first — catches the #29507 TLS-overwrite shape
+    # and other invalid-header cases without opening a sqlite connection.
     _validate_sqlite_header(path)
+    # Full integrity probe — catches corruption past the header (malformed
+    # pages, broken internal metadata). Cached per-path after first success
+    # via _INITIALIZED_PATHS so it only runs once per process per path.
+    _guard_existing_db_is_healthy(path)
     resolved = str(path.resolve())
     conn = sqlite3.connect(str(path), isolation_level=None, timeout=30)
     try:

tests/hermes_cli/test_kanban_db.py

@@ -2981,3 +2981,104 @@ def test_detect_stale_does_not_tick_failure_counter(kanban_home, monkeypatch):
         assert "stale" in kinds, (
             f"Expected 'stale' event in task_events; got {kinds!r}"
         )
+
+
+# ---------------------------------------------------------------------------
+# Corruption guard (issue #30687)
+# ---------------------------------------------------------------------------
+
+def _write_corrupt_db(path: Path) -> bytes:
+    """Write a kanban DB with a VALID SQLite header but malformed page content.
+
+    This is the corruption shape the integrity guard specifically targets
+    (e.g. issue #29507 follow-up reports where the file's first 16 bytes
+    pass the header byte check but ``PRAGMA integrity_check`` then fails
+    because the internal pages are damaged). It's what main's header-only
+    validator was letting through, and what this PR adds the full guard
+    for.
+    """
+    # 100-byte SQLite header (magic + minimal valid-looking fields) so the
+    # cheap header check passes, then deliberate garbage so sqlite refuses
+    # to read the file past the header.
+    header = b"SQLite format 3\x00" + b"\x10\x00\x02\x02\x00\x40\x20\x20"
+    header += b"\x00\x00\x00\x0c\x00\x00\x23\x46\x00\x00\x00\x00"
+    header = header.ljust(100, b"\x00")
+    payload = b"definitely not a valid sqlite page \x00\x01\x02\x03" * 64
+    blob = header + payload
+    path.write_bytes(blob)
+    return blob
+
+
+def test_init_db_refuses_corrupt_existing_file(tmp_path):
+    db_path = tmp_path / "kanban.db"
+    original = _write_corrupt_db(db_path)
+    # Ensure the cache doesn't mask the guard.
+    kb._INITIALIZED_PATHS.discard(str(db_path.resolve()))
+
+    with pytest.raises(kb.KanbanDbCorruptError) as excinfo:
+        kb.init_db(db_path=db_path)
+
+    err = excinfo.value
+    assert err.db_path == db_path
+    assert err.backup_path is not None
+    assert err.backup_path.exists()
+    assert err.backup_path.read_bytes() == original
+    # Original bytes untouched — no schema was written on top.
+    assert db_path.read_bytes() == original
+    assert str(db_path) in str(err)
+    assert str(err.backup_path) in str(err)
+
+
+def test_connect_refuses_corrupt_existing_file(tmp_path):
+    db_path = tmp_path / "kanban.db"
+    _write_corrupt_db(db_path)
+    kb._INITIALIZED_PATHS.discard(str(db_path.resolve()))
+
+    with pytest.raises(kb.KanbanDbCorruptError):
+        kb.connect(db_path=db_path)
+
+
+def test_locked_healthy_db_does_not_classify_as_corrupt(tmp_path, monkeypatch):
+    """A transient lock during the probe must not produce a .corrupt backup
+    and must not be reported as :class:`KanbanDbCorruptError`. Raw sqlite
+    ``OperationalError`` (lock/busy) is acceptable and expected."""
+    db_path = tmp_path / "kanban.db"
+    kb.init_db(db_path=db_path)
+    kb._INITIALIZED_PATHS.discard(str(db_path.resolve()))
+
+    real_connect = sqlite3.connect
+
+    def flaky_connect(*args, **kwargs):
+        # First call is the integrity probe — simulate a lock.
+        raise sqlite3.OperationalError("database is locked")
+
+    monkeypatch.setattr(kb.sqlite3, "connect", flaky_connect)
+
+    with pytest.raises(sqlite3.OperationalError):
+        kb.connect(db_path=db_path)
+
+    # No .corrupt backup may be produced for a healthy-but-locked DB.
+    backups = list(tmp_path.glob("*.corrupt.*"))
+    assert backups == [], f"unexpected corrupt backups: {backups}"
+
+    # And once the lock clears, normal access still works.
+    monkeypatch.setattr(kb.sqlite3, "connect", real_connect)
+    with kb.connect(db_path=db_path) as conn:
+        kb.create_task(conn, title="still here")
+        titles = [t.title for t in kb.list_tasks(conn)]
+    assert "still here" in titles
+
+
+def test_init_db_allows_missing_then_healthy(tmp_path):
+    db_path = tmp_path / "fresh.db"
+    assert not db_path.exists()
+    kb.init_db(db_path=db_path)
+    assert db_path.exists() and db_path.stat().st_size > 0
+
+    # Idempotent on a healthy DB: data survives a second init.
+    with kb.connect(db_path=db_path) as conn:
+        kb.create_task(conn, title="keeps")
+    kb.init_db(db_path=db_path)
+    with kb.connect(db_path=db_path) as conn:
+        tasks = kb.list_tasks(conn)
+    assert [t.title for t in tasks] == ["keeps"]