ADR-0002: Wasmtime sandbox for untrusted compute

Status

Accepted

Context

Peers execute untrusted job slices. Native plugins are unsafe across trust boundaries and ABIs.

Decision

Compile payloads to WebAssembly and execute in Wasmtime with fuel metering and store memory limits. Guest ABI: chimera_alloc / chimera_dealloc / chimera_execute.

Consequences

• Cross-platform binaries (Windows/Linux/macOS).
• Live migration checkpoints linear memory + fuel; call-stack IP is not fully portable — resume re-enters guest with checkpoint_offset (documented limitation).
• Demo guest lives in examples/guest; embedded WAT fallback ships for zero-setup demos.