[JAX] Migrate EP collective-stream annotation to compute_on2

[phu0ngng]

Description

Recent JAX removed jax.experimental.compute_on.compute_on in favor of compute_on2, breaking the import of ep.py (the annotation decorates EP helpers at module load). This migrates to compute_on2.

Type of change

• Documentation change (change only to the documentation, either a fix or a new content)
• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Infra/Build change
• Code refactoring

Changes

• _on_collective_stream uses compute_on2, closing over the static EpLayerConfig/PartitionSpec args in a nullary thunk since compute_on2 abstract-evals every argument.
• compute_on2 moves _xla_stream_annotation onto the async wrapper XLA generates, so test_z_dispatch_combine_on_collective_stream now checks each EP call is reachable from a collective-annotated wrapper.
• compute_on2 and jax.memory.Space exist since JAX 0.10.1, the current collective-stream floor, so no min-version bump is needed.

Checklist:

• I have read and followed the contributing guidelines
• The functionality is complete
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes

[phu0ngng]

Pipeline #60891724 with the nightly JAX image.

[greptile-apps]

Greptile Summary

Migrates JAX expert-parallel collective-stream annotation from the removed compute_on API to compute_on2.

• Wraps EP helper calls in nullary thunks so static configuration arguments are captured rather than abstract-evaluated as operands.
• Places outputs in device memory while scheduling the generated async wrapper on the collective stream.
• Updates the multi-process HLO test to verify that every EP custom call is transitively reachable from a collective-annotated wrapper.

Confidence Score: 5/5

The PR appears safe to merge, with no concrete changed-code failure identified.

The implementation preserves the compatibility fallback and the updated distributed compilation test exercises the new wrapper while checking that all emitted EP custom calls remain under collective-stream-annotated computations.

Important Files Changed

Filename	Overview
transformer_engine/jax/cpp_extensions/ep.py	Replaces the removed compute_on decorator with a compute_on2 thunk wrapper while retaining the existing version-based no-op fallback.
tests/jax/test_multi_process_ep.py	Reworks the collective-stream assertion to follow HLO call edges from annotated async wrappers to nested EP custom calls.

Flowchart

%%{init: {'theme': 'neutral'}}%%
flowchart LR
  A[EP helper invocation] --> B[Nullary thunk captures static config and array operands]
  B --> C[compute_on2 collective-stream annotation]
  C --> D[XLA async wrapper]
  D --> E[EP FFI custom call]
  F[HLO regression test] --> G[Parse computations and call edges]
  G --> H[Verify each EP call is reachable from an annotated wrapper]
  H --> E

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_{Reviews (1): Last reviewed commit: "[JAX] Migrate EP collective-stream annot..." | Re-trigger Greptile}

[jberchtold-nvidia]

LGTM, thanks!