Mid-execution architecture revision: Mamba2 stays as a sequence
encoder; CfC becomes the layer on top (replacing the Phase 1d.3 MLP
stacker). Gate becomes 'stacked AUC >= Mamba2-only stacker AUC at
every horizon' — proves the CfC layer is additive, rather than CfC
alone beating Mamba2 alone.
Plan 1 kernels (cfc_step, heads, projection, BCE, AdamW, Graph A)
are unchanged. Only CfcTrunk's forward path gains a Mamba2 prefix
that consumes the snapshot stream and emits a 128-dim h_mamba which
CfC reads. The Mamba2 kernel (mamba2_alpha_kernel.cubin) is already
in the build.
Option B (parallel + fused dual-stream) is documented as the Plan 2
fallback if the stacked gate fails.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
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