# What changed in flax

> 11 changes in flax 0.12 from its official release notes, upgrade guides and advisories: 1 breaking, 3 new APIs and options. Each one cited. Sources checked 2026-10-30. HTML: https://unstale.sh/pypi/flax/

To see which of these apply to a repository, run `npx @unstale/cli init` in it.

## flax 0.12

### Breaking changes

- Raises ValueError when the separator conflicts with keys. (0.12.11) — [release notes](https://github.com/google/flax/releases/tag/v0.12.11)

### New APIs and options

- Adds a capture_noop option to Module.perturb. (0.12.11) — [release notes](https://github.com/google/flax/releases/tag/v0.12.11)
- Adds a capture_noop option to Module.sow. (0.12.11) — [release notes](https://github.com/google/flax/releases/tag/v0.12.11)
- Adds a config flag for controlling no-op capture in sow. (0.12.11) — [release notes](https://github.com/google/flax/releases/tag/v0.12.11)

### Behavior and default changes

- Makes nnx.Sequential iterable and filters **kwargs per layer. (0.12.11) — [release notes](https://github.com/google/flax/releases/tag/v0.12.11)
- The HiPrim fallback now uses attribute lookup. (0.12.10) — [release notes](https://github.com/google/flax/releases/tag/v0.12.10)

### Fixes and other changes

- Changes to traverse utilities were reverted, restoring the behavior before the breaking change. (0.12.12) — [release notes](https://github.com/google/flax/releases/tag/v0.12.12)
- Skips Sequence modules in capture to prevent mixed key types. (0.12.11) — [release notes](https://github.com/google/flax/releases/tag/v0.12.11)
- Fixes tracing cache misses by caching SimpleCondFn wrappers. (0.12.11) — [release notes](https://github.com/google/flax/releases/tag/v0.12.11)
- Fixes the is_causal mask during decode. (0.12.11) — [release notes](https://github.com/google/flax/releases/tag/v0.12.11)
- Stores WeightNorm scales as Param so they are trainable. (0.12.11) — [release notes](https://github.com/google/flax/releases/tag/v0.12.11)