2026-04-28 - Private ANE API Bridge Outcome

Intent: Record the outcome of the private ANE API investigation after checkpointing the public Phi-4-mini ANE runtime state, following call-hoisting/strength-reduction discipline for reducing CoreML shard boundary costs.

Setup: Checkpoint/tag phi4-mini-ane-q8-fusion-17tok-2026-04-28 was created on commit f273a47 before investigation. Probes included direct _ANEClient / prepareChaining selector inspection, ane_chain_probe against current Phi public-CoreML .mlmodelc shards, and new ane_coreml_bridge_probe.m to inspect the public CoreML load path.

Result: Direct _ANEClient and prepareChaining selectors are present. ane_chain_probe still fails on current Phi public-CoreML shards at the legacy Espresso contract because model.espresso.net is missing. ane_coreml_bridge_probe.m shows public CoreML MLModel load registers a model UUID in _ANEClient connectionsUsedForLoadingModels and exposes the chain MLDelegateModel -> MLE5Engine -> MLE5ProgramLibrary -> e5rt_program_library handle. _programLibraryHandleWithForceRespecialization:error: returned non-null with no error.

Surprise / hurdle: The public CoreML E5RT path already owns a usable program-library handle, while the direct private chaining probe is blocked by older Espresso artifact expectations that public .mlmodelc shards do not satisfy.

Lesson: The next private path should investigate the CoreML E5RT handle/operation bridge rather than trying to synthesize legacy Espresso artifacts first.

Next: Follow the E5RT program-library handle toward operation/chaining surfaces for already-loaded CoreML models; keep public MLComputePlan residency and golden validation as acceptance gates before any performance claim.

Refs: research/ANE_CHAIN_SCHEMA.md