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Author SHA1 Message Date
glenn schrooyenandClaude Opus 5 cc4e88490b SAFETY-02 review: a latch that a restart clears is not a latch
BLOCKER. `auto` was persisted and `sign_wd.tripped` was not, so reconstructing
the Controller against the same store - which is what a container restart does -
brought it back ARMED, into the same fault, unattended: tripped=False, banner
back to NOT READY, and it resumed commanding -1000 then -2000 W before
re-tripping 180 s later. "Restart the add-on" is the first thing an operator
looking at a FAILSAFE banner and a 0 W inverter will try, and under a supervisor
that restarts a crashed add-on it is a loop of three-minute wrong-direction
bursts. DOCS.md's "it does not clear itself" was false across a restart.

`sign_tripped` and `sign_reason` are Store keys now, beside the maintenance
state and for the reason store.py's own docstring gives. Written the moment the
trip happens - reason first, flag second, so a crash between the two can never
persist a latch with no explanation - restored in Controller.__init__, cleared
only by the operator's start. The regression is covered: reverting the restore
fails seven checks in test_watchdog.py.

Review follow-ups, no behaviour change:

- The arming gate is tested against the REAL arbiter. It is the decision the
  ticket turns on and it was asserted in three comment blocks and verified by
  nothing - every case passed `following` in as a literal. Twelve claim
  configurations now derive it from resolve(), including the redirect case
  `winner == "loop"` alone would have got wrong and the `lo` limit that raises
  magnitude without flipping sign.
- The MQTT `status: "failsafe"` value is tested. The check that claimed to cover
  it restated the line above it and never touched the payload.
- The worked example described a config that does not ship: at the defaults
  maintenance_charge_w 2500 against max_w 2000 is an arbiter contradiction and
  0 W, not a -2500 W charge. Rewritten at 1500 W. The contradiction is a real
  pre-existing bug - a default cheap-window maintenance charge silently never
  happens - filed separately and deliberately not fixed here.
- Forward hazard recorded at the gate: `winner == "loop"` disarms the watchdog
  under any higher-priority SET, and a peak-shaving strategy at P_PEAK IS
  grid-following in sign, so it would blind this for every peak event.
- disagrees() is public so the replay harness stops carrying its own copy of the
  predicate it grades.
- held_s takes the clock instead of reading one.
- The two limits are now each stated in both places rather than one each.
- The no-false-positive argument is tied to control.py's freeze permitting the
  command to cross zero; under the shrink-only encoding control.py records as
  rejected, this would false-trip on a load step.
- Measured figures corrected: 93.4 % / 4212 of 17280, per-cluster
  0.3/0.9/10.5/0.0, and the near-circularity of those figures is now stated
  rather than leaned on.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Du77usMj8XNKNFZGmUiWDa
2026-08-28 22:33:15 +02:00
glenn schrooyenandClaude Opus 5 9aed43990b SAFETY-02: a loop can be fresh, tracking and inside its rating and still push the wrong way
The stale-input watchdog asks whether the meter is still talking. The saturation
freeze asks whether the inverter can follow. The output clamp asks whether the
number is too big. A loop can pass all three while charging the battery out of
the grid, because the only thing wrong is the sign.

On 2026-08-20 a commercial controller did exactly that four times in one day,
for up to 77 minutes at a stretch, reaching a commanded -14 768 W against a
±5000 W inverter. app/watchdog.py compares the emitted setpoint against the
authoritative P1 figure and, when they oppose each other with both over 300 W
for 180 s continuously, files a failsafe SET claim at P_SAFETY, commands 0 W and
latches there until an operator starts control again.

Validated against that day rather than against an argument: sim/replay_sign.py
in the infra repo drives this module over the committed captures of both
2026-08-20 and the healthy 2026-08-23 and reaches 18 trips on the fault day -
every one inside a window NOTES.md §4.7 accounts for - and 0 on the healthy day.
The four episodes do share one signature: 0.3 / 0.9 / 10.5 / 0.0 % sign
agreement inside them against 92.9 % healthy.

Three decisions the ticket could not make:

- It is DISARMED whenever the grid-following loop is not what is driving. Sign
  agreement is a property of a loop that follows the meter, and a maintenance
  grid charge opposes the meter by design - 2500 W of charge into a house
  drawing 500 W is +3000 W on the meter against a -2500 W command, for hours.
  The gate tests the emitted number, not the winning claim's name, because a
  limit claim can let the loop "win" and still replace its value.
- The trip LATCHES. Commanding 0 W removes the command side of the comparison,
  so the disagreement always clears the moment the trip works.
- sign_disagree_w at or above max_w is refused at startup. The arbiter never
  lets a command exceed max_w, so such a threshold leaves the watchdog incapable
  of firing while the status page still reports it armed.

What it does not catch, said out loud: an inverter that ACTS opposite to its
command moves the meter further the same way, leaving command and meter in
agreement. That is the saturation freeze's job.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Du77usMj8XNKNFZGmUiWDa
2026-08-28 21:51:35 +02:00