Cross-Language Feature Coverage

This is the canonical feature-coverage matrix for the lazily family. Each binding’s README reproduces it; this page is the source of truth. It is a status view (what each port ships today), distinct from the normative Binding Conformance Matrix, which fixes what every binding must eventually provide.

Legend: ✅ shipped · ~ partial · — absent or not applicable (see notes).

The table below is generated from coverage.json by scripts/sync-coverage.mjs. Edit coverage.json and run make coverage-sync (or node scripts/sync-coverage.mjs) to update this table and every binding README in one shot; make coverage-check guards drift in CI.

Convergence and the wire protocol are pinned by the shared conformance fixtures and JSON Schemas in this repo and the Lean models in lazily-formal.

Notes

• ᵃ Python reactive graph: Cell / Slot / Signal / Effect (sync) and the top-level batch(run) boundary ship; the != PartialEq memo guard applies to cells, slots, and signals. The async counterpart (AsyncEffect) queues reruns at the batch boundary for asyncio reactors.
• ᵇ Dart reactive graph: Context / Slot / Cell / Signal ship; there is no standalone Effect type (observers subscribe on cells) and batch is scoped to the async context.
• ᶜ Zig reactive graph: Cell / Slot / Signal / Effect and the public batch(run) boundary ship (context.zig coalesces the eager-recompute drain at the outermost batch exit).
• ᵈ Serialized context (JS / Dart) — decision: both are meaningful as serialized, realm-local execution flavors, not as shared-graph contexts. They are scored when their own surfaces replay the portable Core fixtures, and are excluded from cross-thread shared-graph stress/model-check tests. A duplicate wrapper is not sufficient by itself: unsupported Core features remain staged, and runner-local locks/dictionaries cannot stand in for them. Either binding may remove the flavor and declare it absent; while it advertises the flavor, it must join every feature peer group it actually supports. See protocol.md § Concurrency layers are required for the conditional layer requirement and reactive-graph.md § Declared context capabilities for the serialized / shared-graph distinction.
• ᵉ Zig async context: Zig removed language async and has no suspendable executor, so the layer is a task-queue + settle() drain surface — the synchronous graph’s pending_recompute/drainPendingRecompute generalized with revision tracking and the 4-state slot machine (async_context.zig).
• ᶠ Zig collections: SourceMap / ComputedMap with atomic move, SourceTree (per-level membership/order reactivity, atomic child move), and the LIS-move-minimized reconcile op-set all ship (collection.zig, cell_tree.zig, reconcile.zig).
• ᵍ Shared-memory blob path (JS / Dart): carry ShmBlobRef wire references but no host-side ShmBlobArena — the I/O-channel fallback of the shared-memory carve-out (see protocol.md § Shared-memory payload path is required).
• ʰ Dart distributed CRDT plane: the CrdtPlane engine (HLC / stamp frontier / stability watermark) ships, but is not yet wired to live merge: crdt root cells.
• ⁱ C-ABI FFI (JS): platform carve-out ffi = none — browser/Worker JS has no shared in-process C ABI. The full state plane (including CrdtSync) still flows over IPC / WebSocket / WebRTC (see protocol.md § C-ABI FFI is required).
• Distributed plane — WebRTC transport + signaling (Rust / Kotlin / JS / Zig): the portable stack (signaling protocol + client, the DataChannel seam, permission- filtering sink/source, in-memory loopback, and the CRDT plane runtime) ships and is conformance-tested; the concrete native WebRTC backend is a platform adapter (str0m in Rust; the browser RTCPeerConnection in JS; a consumer-provided seam in Kotlin and Zig), matching the reference design where the heavy transport is optional behind the seam.