Separate Scheme execution from project orchestration

Morphir Scheme supplies a reader, lexical evaluator, IR frontend/backend and typed transformation procedures. Morphir Engine owns source discovery, manifests, configuration precedence, stage diagnostics and artifacts. Both use the current IR API; versioned JSON input goes through the existing codecs and migrations.

The specialized language takes inspiration from bobzhang's MoonBit Scheme R6RS implementation, but has an independent, smaller implementation and no dependency on its runtime. It supports transform scripts and a functional frontend subset; full R6RS conformance and type inference are outside this foundation.

Filesystem and network capabilities belong to explicit host adapters. A synchronous host contract and an immutable memory host keep the engine available on all four MoonBit targets. Async applications can prepare source snapshots before running transformations. Output artifacts are returned, leaving persistence to the host.

Workspace and project scripts can select frontends/backends and supply typed IR transforms. Each project has an isolated Scheme session; files share its script state in sorted order. Each input currently produces an independent artifact. Cross-file linking, dependency resolution and CLI filesystem commands need host and compiler integration beyond this engine contract.

Tail calls use a trampoline with arena-backed lexical environments. This avoids closure/environment reference cycles on reference-counted targets, but retains frames for the session lifetime. Explicit frame limits and short-lived job sessions bound that retention; environment reclamation remains future work.

Workspace host integration

The approved workspace design extends this boundary with a host runner. Configuration and workspace discovery consume portable snapshots. The engine resolves scripts and source selection into a plan before the host materializes selected source contents. Execution returns artifacts; publication remains a host capability.

TOML configuration follows upstream Morphir workspace layouts and merge rules. Shared workspace/global layers exclude project identity and workspace roots when applied to members. Discovery exposes the protocol-v1 request/snapshot shapes for the implemented TOML subset. YAML decoding remains unsupported with explicit diagnostics.

Native and Node adapters provide filesystem execution. WASM uses Preview 1 imports and a preopened development root; WASM-GC uses an explicit embedding interface. Async hosts prepare snapshots and publish results around the synchronous core.

The filesystem publisher stages all outputs, serializes writers with an exclusive lock, and replaces task destinations with backups for recovery. This is not an atomic workspace transaction. Failures report committed destinations; failed rollback keeps backups for explicit recovery. Scheme cancellation checks run within evaluation.