2026-04-28 - Phi Stateful Raw E5RT Chain Smoke

Intent: Extend the raw E5RT two-operation stream breakthrough from toy controls to real Phi stateful shards, following call-hoisting/strength-reduction discipline and the research/ANE_CHAIN_SCHEMA.md stream-level execution focus.

Setup: Extended e5_two_op_stream_probe with --phi-input for real Phi shapes and state handling. Target chain: local artifacts -> local artifacts. Direct MLState did not work; MLFeatureValue.internalFeatureValueWithState requires a one-buffer MLState, so the probe uses MLState.backings and MLState initWithBackings per state port, then wraps each state with internalFeatureValueWithState. Stage B uses a provider overriding x with stage A hidden while CoreML’s _bindInputFeaturesAndWaitEvents binds ordinary inputs and state.

Result: Both operation binders returned YES, both raw e5rt_execution_stream_encode_operation calls returned 0, and _executeStream returned YES. Stage A output was nonzero, with sample [1.498046875, 5.98828125, 4.94921875, -2.49609375, ...] and sum -337.912079. Stage B output is currently all zeros.

Surprise / hurdle: Public prediction in the same process after taking private operations segfaulted, so the public reference path must run in a separate process. Stateful Phi ports also required one-buffer MLState wrappers rather than direct state reuse.

Lesson: Real stateful Phi two-shard E5 stream wiring and encoding works, but output correctness is not yet proven.

Next: Build a separate-process public reference and investigate output backing/state backing behavior for the all-zero stage B result before any performance claim or scale-out.

Refs: research/ANE_CHAIN_SCHEMA.md