Explore a Kiln runtime adapter #445

Description

Investigate PulseEngine Kiln as a possible EdgeZero runtime target after #436 / PR #275 is accepted. Current main has Fastly, Cloudflare, Spin and Axum adapters, without Kiln. This is a compatibility/proof-of-concept investigation, not a promise of runtime support or an assertion that upstream HTTP interfaces are complete.

Steps to reproduce

After the HTTP foundation merges, pin a Kiln revision and inspect its Component Model/WASI, incoming/outgoing HTTP and host-tooling interfaces. Attempt a minimal EdgeZero handler and outbound request using the supported guest target; record commands and concrete blockers.

Expected behavior

A revision-pinned compatibility assessment, reproducible proof or blocker, proposed smallest adapter/CLI shape and proceed/defer recommendation make implementation scope reviewable.

Impact

Starting a new adapter on superseded contracts or assumed upstream capability would duplicate migration work and create unsupported platform claims.

Proposed fix

Keep PR #275 as the explicit blocker. Map request/response/body/async/config/log/clock limits to accepted contracts, assess Spin/WASI reuse versus a dedicated adapter, and document build/package/serve/deploy scope. Preserve native/guest dependency boundaries. Verify upstream versions/interfaces during the investigation rather than freezing changing claims in this issue.

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.

Related

• Blocking foundation: Implement portable outbound HTTP and request lifecycle contracts #436 / PR feat: implement portable outbound HTTP and request lifecycle contracts #275; complete and merge it before this exploration starts.
• Kiln repository; existing Spin integration is the comparison point. No open implementation PR was found.