`band_hugs_floor` compares an arm's weakest tenth against its floor, and
#4225 made it SUSPEND rather than soften when the floor moved inside the
window — because across a change the scores and the bar come from two
different populations. It reads `floor_moves_since`, which answers "did
this arm's floor move", and it read an empty answer as "no, it held
steady".
Those are the same answer only where the ledger was watching. Before an
arm's first floor row there is nothing to move, nothing to report, and no
way to tell a steady floor from an unrecorded one. The suspension was
reading absence of evidence as evidence of absence, and the symptom is the
one #4225 documented: a band "-0.0208 above its floor" — an impossible
negative distance, printed with the suspension silent.
Every install passes through this. The ledger's first row for an arm is
written when that install first boots the release that records baselines,
so any window longer than the install is old reaches back past it. The
lowered-floor direction hides: the gap comes out comfortably positive and
reads as a clean bill of health.
`floor_history_gaps(since)` answers the question its companion cannot:
which arms' floor history does not REACH the start of the window. Arms
come from `surface_names()`, not from the ledger — an arm the ledger has
never heard of is exactly the one at risk, so it cannot be the ledger that
decides which arms get asked about.
Baselines count here, which is the one place the two deliberately
disagree. A baseline records a default without changing it, so it is not a
move and `floor_moves_since` filters it out. It IS the ledger beginning to
observe the arm, and from that moment silence genuinely means the floor
held — filtering it out here would suspend the band check forever on every
install that has never tuned.
`floor_history_unknown` sits between the known move and the band, so an
arm with a date to give gives it. Two sentences, because the remedies
differ: a date says ask again with a smaller `days`; no history at all
says there is nothing to wait for, and names what starts the record.
Why now: #4261 measures the work-log change by reading these warnings, and
every window for the next month opens before this ledger's first row.
Measuring against an instrument that prints a number it cannot support is
the #4225 trap one level up.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01821k5B3Ysecp9fNYs92Kuy
bvandeusenandClaude Opus 5
42360f616c