URGENT correctness fix surfaced by Task 13 implementer.
Bug: training-time Phase 2 dispatch sites (cfc_step_per_branch_fwd at
~3139, h_mag_per_bucket for Controller D at ~3211-3212) read
self.trunk.bucket_*_d which are zero-initialized at trunk construction
and only populated via load_checkpoint. The Phase 1→2 transition
populates a SEPARATE BucketRoutingMetadata owned by the trainer
(self.bucket_routing_metadata) but never syncs it into the trunk fields.
With zero-init bucket_dim_k, the per-branch kernel's uniform predicate
`tid >= bucket_dim_k[branch]` early-returns ALL threads -> Phase 2
silently no-ops during training, Smoke 1 fails before producing signal.
Fix: at transition, DtoD-copy metadata buffers into trunk fields BEFORE
the `Some(metadata)` move (so `metadata.*` borrows remain valid):
- metadata.bucket_channel_offset_d -> trunk.bucket_channel_offset_d
- metadata.bucket_dim_k_d -> trunk.bucket_dim_k_d
- metadata.bucket_id_per_channel_d -> trunk.bucket_id_per_channel_d
- metadata.heads_w_skip_offset_d -> trunk.heads_w_skip_offset_d
Trunk fields remain the single source of truth for both training-time
dispatch AND checkpoint serialization. Total sync cost: 4 DtoD memcpys,
~256 bytes total at the one-shot transition (off the hot path).
Verification:
- `cargo check -p ml-alpha --all-targets`: clean
- `cargo test -p ml-alpha --lib`: 33 passed, 0 failed
- 3 read sites (perception.rs:3139, 3211-3212, 4725-4726) verified
unchanged; all 4 new memcpy_dtod_async calls bracketed in the
transition block (perception.rs:2224, 2234, 2244, 2254).
- Block-diagonal heads grad-mask init (step 7) continues to read
`metadata.bucket_id_per_channel_d` via `as_ref()` after the move;
ordering preserved per pearl_canary_input_freshness_launch_order.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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