The motion oracle borrowed screenshot-diff's DEFAULT_THRESHOLD, a value
sized for a baseline held across sessions and machines and so obliged to
absorb real drift. This comparison holds two captures one poll apart
from a single live session, where a static screen reads back
byte-identical: both capture paths are lossless PNG and the downscale is
deterministic. The borrowed value put the gate at ~25.5 levels/channel,
which mattered because spatially uniform change is all-or-nothing —
every pixel moves by the same amount, so it clears the gate on all of
them or on none, and MOTION_FRACTION is never the deciding term. A
cross-fade slower than ~1.4s therefore counted zero pixels and reported
settled mid-animation, over a screen still painted and still
hit-testing; and being settled rather than timed-out, degradedReason
stayed silent while updateBaselines could adopt a mid-fade frame as
golden.
0.03 (~7.6 levels/channel) keeps a margin over the +5/channel drift the
tests treat as the noise floor and moves that cliff out ~3.3x, to ~4.5s
at full contrast. It stays a rate floor rather than a duration floor, so
the comment now names the gate as the only term bounding what is left.
This supersedes the parity pin below it: coordinated drift is covered
instead by pinning the value and the direction, so restoring parity
trips a test rather than silently re-widening the blind spot. The
+25/channel case gives way to a two-sided bracket at +7/+8, and two
samples of a 2s indigo-over-white dismissal — a distance deliberately
between the new gate and the old — pin the regression itself.
The parity pin stopped the two constants drifting apart but not
together: the behavioral tests bracket the tolerance only loosely from
above, so raising both flow-pixels' PIXEL_THRESHOLD and screenshot-diff's
DEFAULT_THRESHOLD to 0.2 widened the per-pixel gate — the whole motion
oracle — with the suite still green. Assert the shared value alongside
the mirror.
Every comparison test fed the motion oracle grey — each channel term
could be deleted independently, and misindexing blue onto alpha (the
byte the docstring says is ignored) survived too, admitting motion
confined to one channel: a navy scrim fading in over black. Full-frame
red-only, green-only, and blue-only changes (plus the mid-amplitude
navy case) now register as motion, and an alpha-only change registers
as still — killing each channel-drop mutant and catching the alpha
misindex from both directions.
An already-spent caller deadline collapses into timed-out where the
flow-actions twin splits out not-attempted — deliberate here, but
undocumented and unpinned: relabelling the arm to aborted left the
suite green while turning an outage-fallback snapshot from a degraded
pass into a skip blaming a cancellation that never happened.
The collapse is now justified in prose (the outcome feeds only snapshot
degradation reporting, with no freshness contract for the twin's split
to protect, and the note text is honest for both expiry shapes) and
pinned twice: a zero-budget settlePixels call resolves timed-out with
no backend consulted, and the real fallback driven through runSnapshot
after a window-consuming outage settle degrades instead of skipping.
The simulator-server writes its temp PNG before replying, and the reply
is the only place the path is learned — so an abort landing mid-capture
severed the fetch, capturePixels soft-failed without ever learning the
path, and the file was orphaned, breaking the stated ownership contract
(the capture promise decodes and deletes its own temp file when it
eventually completes).
captureFile now passes no signal, matching the Chromium arm that never
took one: cancellation stays responsive because settleWithin abandons
the promise, while the capture self-completes on its own bounds, learns
the path, and cleans up in the finally on every path.
The two pixelsDiffer colour tests probed only the extremes, leaving the
band where a real transition lives — a dim, a fade, a crossfade —
unexercised: a 5x threshold mutant swallowed a full-frame 120-per-channel
change with the suite green. Bracket the tolerance from both sides
(grey120 registers, +25 stays still) and assert the documented mirror of
screenshot-diff's DEFAULT_THRESHOLD directly, exporting both constants.
Every existing settlePixels test fed a constant frame, hung the capture,
or aborted, so nothing past the first comparison was pinned — deleting
the predecessor advance left the suite green while a transition coming
to rest looking different from its first frame would burn the whole
window and report timed-out. Drive A/B/C/C through the real settle and
assert settled on exactly four captures.
Jakub Piasecki