Who contributed to Google on July 26, 2026?

3 developers shipped this update, including mattjj, copybara-service, and kodlan.

What were the notable Google updates?

[custom_vjp3] add custom_jvp3, Export `get_mesh`, `use_abstract_mesh` and `get_abstract_mesh` from the jax namespace, and [remat3] allow custom_vjp fns that save ref residuals, via forwarding.

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The Wire · Showcase

JAX OVERHAULS AUTODIFF INTERNALS WITH CUSTOM_VJP3, EXPANDS MESH API

By RepoJournal · Filed 06:57 UTC on July 26, 2026 · About Google

3 people shipped this

mattjj @mattjj 2 cited

copybara-service @copybara-service 1 cited

kodlan @kodlan 1 cited

JAX shipped a major redesign of custom differentiation rules that simplifies how you define vector-Jacobian products, while simultaneously opening up mesh operations to the public API.

The custom_vjp3 pattern [1] replaces the dual-rule system: you now define only the forward pass and a single jvp method, with reverse-mode and vmap batchedness inferred automatically via linearize_from_jvp and vjp_from_jvp. When a rule produces more-batched outputs than inferred, the system raises a clear error pointing to hijax as the solution, eliminating silent correctness bugs. Complementing this, JAX now exports get_mesh, use_abstract_mesh, and get_abstract_mesh directly from the jax namespace [2], making distributed and abstract mesh operations accessible without internal imports. The remat3 branch gained support for custom_vjp functions that save reference residuals via a forwarding pattern [3], letting you stash gradients in refs and recover them during backprop. Separately, the shard_map collective matmul example [4] was rewritten to use pad-and-add instead of two half-size multiplies per ring step, issuing a single full-size matmul with full contraction length per step.

Action items

→ Review custom_vjp3 migration guide if you have custom differentiation rules in production google/jax [plan]
→ Update internal code to use public mesh exports instead of internal imports google/jax [plan]
→ Monitor remat3 and shard_map collective patterns as they solidify google/jax [monitor]

References

[1] [custom_vjp3] add custom_jvp3 ↗ google/jax
[2] Export `get_mesh`, `use_abstract_mesh` and `get_abstract_mesh` from the jax namespace ↗ google/jax
[3] [remat3] allow custom_vjp fns that save ref residuals, via forwarding ↗ google/jax
[4] Use pad-and-add in the shard_map bidi collective matmul example ↗ google/jax

Quick answers

What shipped in Google on July 26, 2026?: JAX shipped a major redesign of custom differentiation rules that simplifies how you define vector-Jacobian products, while simultaneously opening up mesh operations to the public API. In total, 15 commits and 9 pull requests landed.
Who contributed to Google on July 26, 2026?: 3 developers shipped this update, including mattjj, copybara-service, and kodlan.
What were the notable Google updates?: [custom_vjp3] add custom_jvp3, Export `get_mesh`, `use_abstract_mesh` and `get_abstract_mesh` from the jax namespace, and [remat3] allow custom_vjp fns that save ref residuals, via forwarding.

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