2026-04-28 - Stream-Level SetupOperationForInputFeatures Replaces Pool

Intent: Determine whether the CoreML CoreML stream execution stream setupOperationForInputFeatures:operationPool:error: surface can append multiple operations to one stream, following call-hoisting/strength-reduction discipline for reducing shard-boundary materialization.

Setup: Ran local two-stage stream probe --probe-setup on a fresh stream. The probe called setupOperationForInputFeatures:operationPool:error: twice: first with the toy_a pool, then with the toy_b / toy_b_h pool.

Result: Both setup calls returned YES, but the second call replaced the stream contents rather than appending to them. The stream did not become a two-operation chain through this public-looking setup route.

Surprise / hurdle: The public CoreML setup surface looks one-operation/one-pool oriented and does not expose a multi-op DAG or append encoder.

Lesson: CoreML stream execution stream setupOperationForInputFeatures is not the missing append/chaining primitive; it replaces the active operation pool.

Next: Remaining paths are stream-level below the CoreML wrapper or building one CoreML program/function containing fused ranges; do not spend more Phi chaining work on this CoreML setup surface.

Refs: research/ANE_CHAIN_SCHEMA.md