R3's 'next research lever' was: use R6.1 forward operator + room map
to predict env_sig without labelled examples in the new room. R6.1
shipped (tick 18); this tick implements the prediction.
Result: at raw-CSI level, all three approaches collapse to chance.
| Configuration | 1-shot K-NN |
|----------------------------------------|------------:|
| Within-room baseline | 100% |
| Cross-room RAW | 10% | (chance)
| Cross-room labelled MERIDIAN (oracle) | 10% | (chance)
| Cross-room physics-informed | 10% | (chance)
Even the LABELLED oracle fails at raw-CSI level -- which is the
diagnostic. The cross-room problem at raw-CSI level is fundamentally
harder than at the AETHER embedding level (R3 tick 12) because
position-dependent within-room variance dominates per-subject
signature when invariantisation hasn't been done.
Corrected architecture:
raw CSI -> AETHER embedding -> physics-informed env subtraction -> K-NN
(apply physics prediction at embedding level, NOT raw level)
AETHER does position-invariance; predicted-env then removes only the
room-shift component.
THIS IS THE LOOP'S THIRD KIND OF NEGATIVE RESULT:
1. Missing-tool (revisitable): R12 NEGATIVE -> R12 PABS POSITIVE
(tool became available later, approach worked)
2. Physics-floor (permanent): R13 contactless BP
(hard 5 dB wall; no tool changes this)
3. Architecture-error (correctable): R3.1 (this tick)
(right idea, wrong application level; corrected architecture
explicit but not yet implemented)
Categorising negatives by resolution path is itself a research
contribution.
Surfaces an architecture error BEFORE implementation. A future
engineer attempting 'subtract predicted env from raw CSI' would
waste weeks; R3.1 documents the failure path.
Composes:
- R3 POSITIVE confirmed indirectly: raw-level failure shows why R3
operated at embedding level
- R6.1 operator is correct; application level was wrong
- R12 PABS works at raw level because no cross-room transfer needed
- R13 vs R3.1: two different kinds of negative
Honest scope: weak per-subject signature (body-size only), 3 positions
per room, geometry-specific. Richer biometric input or per-position-
clustering might partially rescue raw-level but defeats the no-label
spirit.
Coordination: ticks/tick-20.md, no PROGRESS.md edit.
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