---
id: value-equal-bailout
name: Value.Equal bail-out for unchanged subtrees
status: pending
depends_on: [review-reconciler]
created: 2026-05-18T16:22:57.339429429Z
modified: 2026-05-18T16:22:57.339429873Z
scope: narrow
risk: low
impact: component
level: implementation
---

# Description

Add `Value.Equal` as the first TypeBox optimization layer. When reconciling, if a fiber's cached node is deep-equal to the next node, skip the entire subtree — no `prepareUpdate`, no `commitUpdate`, no children reconciliation.

This is the highest-impact optimization according to the architecture doc because it skips entire subtrees. It's also the simplest to implement and has no constraints (unlike `Value.Hash` which has the global accumulator issue).

The optimization is applied during `reconcileProps`:
```
if Value.Equal(fiber.cachedNode, nextNode):
  return  // skip this fiber and all children
```

## Acceptance Criteria

- [ ] `Value.Equal` check added before property reconciliation
- [ ] If fiber's cached node equals next node, skip `prepareUpdate` and children reconciliation
- [ ] Cached node stored on fiber (new `cachedNode` field or reuse `props` snapshot)
- [ ] Correctness: behavior is identical with and without the optimization
- [ ] Existing tests pass
- [ ] New test: unchanged subtree skips `prepareUpdate`/`commitUpdate`
- [ ] New test: changed prop still triggers `prepareUpdate`
- [ ] New test: deeply nested unchanged subtree is fully skipped

## References

- docs/architecture/reconciler.md — TypeBox Optimization Layer, Value.Equal row
- docs/architecture/reconciler.md — Optimization Strategy (step 1)

## Notes

> To be filled by implementation agent

## Summary

> To be filled on completion