# Oral-A-v6: stagewise causally whitened feedback without KP

## Motivation and claim boundary

V5 showed that per-example task perturbations contain useful causal
information, but its interleaved scalar-normalized delta updates failed to
carry that information into the early ResNet-20 layers.  After 20 sweeps, the
readout feedback itself had parameter cosine only `0.1771`; early-third
teaching alignment was `0.00115` even though several late layers reached
`0.20--0.38`.

One post-failure diagnostic, not a candidate result, used the same 2,560
readout observations in a local least-squares fit.  It raised last-hidden
teaching alignment to `0.8534`.  This shows that the observations have enough
signal and identifies the failed online regression as a bottleneck.

V6 is a new bounded mechanism, not a V5 rate or sweep-count recovery.  It
changes both optimization and information timing:

1. fit the readout feedback from its complete local causal dataset;
2. freeze it, collect a complete causal dataset for the last convolutional
   feedback edge, and apply one diagonal-whitened local least-squares update;
3. freeze that edge and repeat toward the input.

No parent edge observes data until its child path has been fitted.  The dense
fit and convolutional sufficient statistics consume only stored task
perturbation targets, local child contexts, and the current feedback tensor.
They never read or copy a forward weight, use KP, or invoke reverse-mode
learning.  V6 remains a scalable-vectorizer feasibility test, not yet the
Harnett-specific SDIL contribution.

## Local fits

For the readout, concatenate the per-example output signals `C` and causal
pooled-hidden targets `Y` and solve the ridge-scaled local normal equations

```
R^T = (C^T C + lambda I)^(-1) C^T Y,
lambda = 1e-6 trace(C^T C) / n_classes.
```

For convolutional edge `l`, let `e = q - p` be the difference between the
causal parent-field target and the complete current parent teaching field.
Accumulate the ordinary local correlation numerator and its per-parameter
diagonal curvature:

```
b_l = sum Corr(e, c_l)
d_l = sum Corr(1, c_l^2)
Q_l <- Q_l + b_l / (d_l + 1e-3 mean(d_l)).
```

This is a diagonal local least-squares step.  The ridge is scale-relative and
fixed globally; there is no learning-rate or per-layer schedule.

## V6-0 mechanics gate

Before CIFAR endpoints, deterministic float64 checks must show:

- the dense fit is invariant to changing every forward weight after causal
  observations are stored, to absolute error below `1e-12`;
- the convolutional fit has the same invariance and changes only its selected
  feedback edge;
- on independent Gaussian local contexts with responses produced by a known
  feedback tensor, one diagonal fit reduces held-out field MSE by at least
  `80%`;
- one tiny reverse stage sequence is finite and all legacy convolutional
  smoke tests remain green.

## V6-1 frozen-forward causal-capture gate

Copy V5's seed-0 ResNet-20 state, frozen 10,000-example development prefix,
5,000-example validation split, 64-example exact-gradient audit, batch 128,
evaluation-mode causal BatchNorm, `sigma=0.01`, and perturbation seed 5000.
Use exactly 20 fixed unaugmented prefix batches for every stage.  There are 19
stages (readout plus 18 convolutional edges), 20 events per stage, 380 events,
760 logical batch-loss queries, and 48,640 per-example causal observations.
Forward/readout weights, BatchNorm state/affines, and forward optimizer state
must remain bitwise fixed.

The only numerical constants are the readout relative ridge `1e-6` and
convolutional diagonal ridge `1e-3` written above.  Record fixed HFA and the
final V6 state.  V6-1 passes only if both are finite and V6:

1. reaches early-third teaching/negative-gradient cosine at least `0.10`;
2. reaches all-layer cosine at least `0.20`;
3. improves early-third cosine over fixed HFA by at least `0.08`;
4. keeps every feedback/forward norm ratio in `[0.1, 3.0]`;
5. uses exactly the fixed event/query/observation counts and zero forward
   weight reads or reverse-mode learning operations.

There is no ridge, batch, stage-order, event-count, probe, clipping, or norm
recovery after the endpoint.  Failure closes V6 and the present no-KP causal
vectorizer route.  Passing opens only a separately frozen short task gate;
capture alone cannot raise the reviewer score.