Mirror — continuous cross-language sync

Mirror keeps a migrated target project synchronized with an evolving source project. After Transmute produces a first target, link the pair and sync incrementally instead of remigrating the whole repository.

TypeScript changes
        ↓
semantic diff vs baseline PUIR
        ↓
regenerate affected regions
        ↓
build + differential tests
        ↓
Rust (or other target) updated

First supported path

Source	Target	Tier
TypeScript / JavaScript	Rust	Tier 1 (weather-api demo)
Python	Rust	Tier 2 (planning / partial)
Rust → TypeScript	—	Experimental (reverse sync gated)

Tiers reflect implemented conformance, not marketing claims.

Workflow

# One-time: migrate, then link
plx migrate ./examples/weather-api --to rust -o ./examples/weather-api-rust --require-build --require-tests
plx link ./examples/weather-api ./examples/weather-api-rust

# Ongoing
# edit TypeScript…
plx sync
plx sync --check    # CI / no writes
plx status          # drift summary
plx ci              # sync --check + target verify

Link metadata lives under the target:

.parallax-link/
├── link.json
├── source-index.bin
├── semantic-map.bin
├── dependency-map.json
├── manual-regions.json
├── ownership.json
├── baselines/
└── history/

Default policy: source-authoritative.

Commands

Command	Purpose
`plx link <src> <tgt>`	Create Mirror link
`plx sync`	Incremental translate + verify
`plx sync --check`	Freshness only (fails if stale)
`plx sync --reverse`	Target→source when node is ExactYes (else Unsupported)
`plx sync --patch`	Preview regenerate without writing
`plx status` / `--json`	Drift / machine-readable status
`plx ci`	`sync --check` + differential verify
`plx history`	Sync history
`plx rollback`	Restore last pre-sync target snapshot
`plx explain <file:line> -C <tgt>`	Source-map explanation
`plx why <file> -C <tgt>`	Why a target file changed
`plx verify`	Run differential / property notes

What sync does (and does not)

Does

Semantic diff of PUIR (not text-only)
Stable semantic IDs (plx:function:…)
Regenerate affected modules transactionally (snapshot → apply → build/test → commit or restore)
Preserve files marked with manual BEHAVIOR_CHANGE ownership
Report testing confidence (migrated suite), never claim formal proof

Does not (yet / honest limits)

Full bidirectional live migration without review gates
Property-based equivalence as a complete fuzzer (--property notes only)
plx watch daemon (not shipped)
Guaranteed idiom preservation for every manual refactor
All language pairs as Tier 1

Manual edits

Ownership metadata is stored in .parallax-link/ownership.json and manual-regions.json (sidecar preferred over invasive markers). Behavior-changing target edits block overwrite under source-authoritative policy until you choose preserve / overwrite / inspect.

CI

- run: plx sync --check
- run: plx ci

Fails when the link is stale, the target fails build/tests, or verification mismatches.

Transmute — initial project migration
CLI — command reference
Limitations — capability honesty

Parallax Documentation