Explore a Kiln runtime adapter #445

Blocker

• Complete and merge #275 — portable outbound HTTP and request lifecycle contracts before starting this exploration. Evaluate the Kiln adapter against the finalized contracts from that work.

Description

Investigate PulseEngine Kiln as a potential runtime target for EdgeZero HTTP applications and determine the smallest viable adapter integration.

Kiln is a Rust WebAssembly runtime aimed at embedded and safety-critical environments. Its README describes early development with Component Model execution working and some WASI interfaces still in progress. Verify the interfaces EdgeZero actually needs before recommending implementation.

Investigation

• Confirm the supported Component Model/WASI versions, guest compilation target, and availability of wasi:http/incoming-handler and wasi:http/outgoing-handler. Identify any host HTTP server or custom bindings needed.
• Map request/response conversion, body handling, outbound proxy requests, async execution, environment/configuration access, logging, and clocks to EdgeZero's adapter contract. Record unsupported capabilities and resource limits.
• Assess reuse of the existing Spin/WASI integration and whether Kiln needs a dedicated edgezero-adapter-kiln crate or a shared WASI component path. Preserve core portability and keep host runtime dependencies outside guest code.
• Establish the build/package/run workflow using Kiln's current tooling, including the scope of CLI build/serve/deploy integration and realistic deployment environments.
• Attempt a minimal demo handler and outbound HTTP request where supported. Document the exact runtime revision, commands, observed results, and any upstream blockers.

Done when

• A compatibility assessment identifies supported, partial, and missing capabilities, with links to upstream evidence.
• A reproducible HTTP proof of concept is documented, or a concrete blocker explains why it cannot run.
• A proposed adapter structure and CLI/configuration changes are outlined, with an estimate of effort and required contract/CI checks.
• A proceed/defer recommendation is recorded, with implementation follow-ups or upstream dependencies identified.

Affected area

New adapter — Kiln / WASI Component Model; CLI (new, build, deploy, dev); CI / Tooling; Documentation.