# Phase 4AM — D18 whole-brain plastic interface

This is a separate, non-trained branch. All Phase 1–4AL files remain read-only.
The user authorized independent new-model dynamics hypothesis tests. No base
CSR, transmitter sign, W_syn, neuron threshold, APL calibration, eligibility-v2,
or 14,232-edge mask is changed. No game, decoder, RL, or visual input is used.

## Fixed test order and scope

1. All 120 sealed AK inputs and their 24 predeclared repeats run with exactly
   zero plastic_delta. Compare every recorded state bit, event, count, delayed
   edge queue, request acceptance, and APL generated/applied/pending sample
   against AK. All must pass before any nonzero overlay runs.
2. The same complete input inventory runs with one fixed diagnostic overlay:
   the original float32 eligibility-v2 floor, `-.25 * base_candidate_mv`.
   All 14,232 mask edges are included; all other weights remain identical.
   Twenty-four technical repeats must be exact. This is not learned memory.
   All presynaptic events are recomputed by the whole brain, unlike AL's
   clamped-source MBON replay. No outcome selects an odor, compartment, dose,
   parameter, or number of training pairings.
3. Pure-function compatibility tests validate the frozen eligibility trace and
   original additive apply_v2 rule. No reinforcement or weight update occurs
   in any of these GPU trials. Fixed delta is installed only before tick zero.

Report both cohorts, both modes, all odors and all seeds. Technical repeats do
not increase the statistical sample. Matched-energy retains its inherited
meaning: expected stochastic input, not exactly matched realized event counts.
Simulation remains 100 ms, including its unadvanced delay/APL tail.

## Explicit precision bridge — a new interface assumption

The existing D18 brain uses float64 SI voltage weights. Frozen eligibility-v2
uses float32 mV deltas and float32 candidate base amplitudes. The adapter keeps
the original D18 base bytes and adds `float64(delta32) * float64(.001)` using
separate non-fused operations, only on nonzero delta rows. Zero delta must not
reconstruct the base through float32. Positive original mask weights must
remain positive. This is not a claim of bitwise nonzero equivalence to the old
float32 brain, nor of precisely 25% of float64 D18 amplitudes. The base candidate
is reproduced from the pinned original Phase 4C NumPy expression, not converted
back from the float64 brain. The mask and all units are recorded.

Only the pre-loop weight-install hook is inserted in an AST-derived copy of
the SHA-pinned AJ function. Its timestep loop AST and original CUDA operators
remain identical. The old module is not patched and its original __file__ is
not fabricated. Inherited AJ source metadata describes the parent; additional
AM adapter provenance explicitly describes the new overlay. The original spike
delay queue stores spike identities and reads fixed weights at arrival. No
mid-trial update or implicit weight-snapshot delay rule is introduced.

## Interpretation and next experiment boundary

Record MBON, KC, DAN, actual MBON downstream, descending and motor output
changes separately, as well as first divergence and recruited/lost KC cells.
Static transfer is neither associative acquisition nor a maximal functional
effect bound. A weak static response does not prove all sparse overlays fail.
The full-brain response is not compared with AL as a strict arithmetic oracle:
AL clamps feedback and its float64 0.75 multiplication is a different fixed
precision intervention. Any side-by-side descriptive result states both.

Conditioning must be separately preregistered. Keep the original 4L static
ODOR_A (4-ethylphenol) and ODOR_B (3-hexanone), reciprocal cue assignments,
type/compartment-specific US and frozen eligibility-v2. PAM/PPL1 alone never
defines valence. The original D scalar is an artificial unconditioned-signal
interface, not measured dopamine or the number of actually emitted DAN spikes.
Log requests, acceptance, and actual DAN spikes separately. Multiplying D by
actual accepted spikes would be a different explicitly registered hypothesis,
not an unnoticed repair of eligibility-v2. No such change is made here.

Later functional learning requires independent evaluation seeds, actual paired
and control trajectories, MBON and downstream specificity, reversal and real
time retention. Neither file validity, delta change nor a static response
completes the learning goal. This stage creates no learned candidate.

## Integrity

Exclusive-create outputs, a pre-outcome source/input/config manifest, fixed
trial inventory, unit-test records, complete per-trial recording hashes,
pre/post frozen integrity, and the five unchanged deterministic-v2 reference
trials are required. Partial outputs are preserved and never overwritten.
No queued ComfyUI job is evicted. Only the declared RTX 4090 is used. The old
references are regression checks of the old runtime, not proof of D18 biology.

The biological limitations and primary-paper evidence are inherited unchanged
from sealed AL EVIDENCE.md; this precision/interface implementation introduces
no new single-cell physiological measurement or universal dopamine rule.