Per-node checkpoint now stores the last-processed event TIMESTAMP (int epoch)
instead of a file path compared lexically. A file is "new" iff its timestamp
(parsed from evt-<node>-<unixts>-<type>-<svc>.json, mtime fallback) exceeds the
node's checkpoint; processing is ordered by timestamp, not path.
Root cause (PIHA dead ~34d, 2026-07-12): a stray evt-unknown-<ts>-… file landed
in events/piha/, lexically greater than every evt-piha-… name. The lexical
checkpoint pinned there, so every genuinely newer piha event sorted "before" it
and was skipped forever. Event backlog grew to 7344 files, last_seen frozen,
shadow-read logged false SHADOW_LIVENESS_MISMATCH event=dead prom=up.
- _event_ts_from_path: filename epoch, mtime fallback; NEVER returns 0 for an
existing file (0 == "older than checkpoint" == the poison).
- _checkpoint_ts_from_value: graceful migration of pre-fix path-string
checkpoints (and the older last_processed_file format) to int epochs;
unparseable → 0 (reprocess all — safe, process_event is idempotent on
last_seen/world_state; bias to reprocess, never to skip).
- Preserved: quarantine of bad events, observer-source re-ingest guard.
- Regression tests (test_incident_lifecycle.py section 9): lexically-smaller-
but-newer processed, unparseable name falls back to mtime (not wedged),
ts-not-path ordering, both checkpoint-format migrations, helper units.
Separate bug filed in backlog (not fixed here): ha-diag-agent emits node=
"unknown" events (config.py node_name default) into another node's dir when
NODE_NAME reaches the compose volume path but not the app env — the source of
the poison file.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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