SQLite's WAL mode requires shared-memory (mmap) coordination and fcntl
byte-range locks that don't reliably work on network filesystems. Upstream
documents this explicitly:
https://www.sqlite.org/wal.html#sometimes_queries_return_sqlite_busy_in_wal_mode
On NFS / SMB / some FUSE mounts / WSL1, 'PRAGMA journal_mode=WAL' raises
'sqlite3.OperationalError: locking protocol' (SQLITE_PROTOCOL). Before
this change, every feature backed by state.db or kanban.db broke silently:
- /resume, /title, /history, /branch returned 'Session database not
available.' with no cause
- gateway logged the init failure at DEBUG (invisible in errors.log)
- kanban dispatcher crashed every 60s, driving the known migration race
(duplicate column name: consecutive_failures, #21708 / #21374)
Changes:
- hermes_state.apply_wal_with_fallback(): shared helper that tries WAL
and falls back to DELETE on SQLITE_PROTOCOL-style errors with one
WARNING explaining why
- hermes_state.get_last_init_error() + format_session_db_unavailable():
capture the init failure cause and surface it in user-facing strings
(with an NFS/SMB pointer for 'locking protocol')
- hermes_cli/kanban_db.connect(): use the shared helper
- gateway/run.py: bump SessionDB init failure log DEBUG -> WARNING
(matches cli.py's existing correct behavior)
- cli.py (4 sites) + gateway/run.py (5 sites): replace bare
'Session database not available.' with format_session_db_unavailable()
Tests: 12 new tests in tests/test_hermes_state_wal_fallback.py + 1 new
test in tests/hermes_cli/test_kanban_db.py. Existing suites (state,
kanban, gateway, cli) remain green for all tests unrelated to pre-existing
failures on main.
Evidence: real-world user on NFSv3 mount (172.26.224.200:d2dfac12/home,
local_lock=none) reporting 'Session database not available.' on /resume;
'locking protocol' appears in 4 distinct log entries across backup,
kanban, TUI, and CLI paths in the same session.
closes#22032
2a7047c2ed