Adds the parallel `runNative()` path inside `session/llm.ts` so a narrow
slice of sessions can flow through `@opencode-ai/llm` instead of the AI
SDK `streamText`. Behavior is gated and shipped off by default; only
callers that opt in see any difference.
The full migration plan (audit gap #4) is parallel-path-with-flag,
prove parity test-by-test, flip default last. This commit is phase 1:
get the wire-up in place behind a flag with one protocol so we can see
whether the design holds before committing to the full migration.
Wire-up summary:
- New flag `OPENCODE_EXPERIMENTAL_LLM_NATIVE` (also enabled by the
umbrella `OPENCODE_EXPERIMENTAL`). Off by default.
- The session-LLM `live` layer now consumes `RequestExecutor.Service`,
and the `defaultLayer` provides `RequestExecutor.defaultLayer` so a
Node fetch HTTP client backs every native stream.
- `runNative(input)` returns `Stream<Event> | undefined`. `undefined`
means "fall through to AI SDK." It returns a real stream only when
every gate passes: the flag is set, the caller populated
`input.nativeMessages` (the bridge needs typed `MessageV2.WithParts`,
not the AI SDK `messages` array), the session has zero tools (Phase
2 will lift this), and the bridge routes the model to a protocol in
`NATIVE_PROTOCOLS`.
- `NATIVE_PROTOCOLS` is a single-entry set today: `anthropic-messages`.
Other adapters are imported and registered with the client so the
Phase 2 expansion is a one-line edit, not an architecture change.
- Stream wiring: client.stream(req) -> Stream.flatMap(event ->
fromIterable(map.map(event))) -> Stream.concat(suspended
fromIterable(map.flush())) -> Stream.provideService(
RequestExecutor.Service, executor). The flush stream is built lazily
with `Stream.unwrap(Effect.sync(...))` so it observes the mapper
final state after every upstream event has been mapped.
- The mapper (`LLMNativeEvents.mapper`) emits AI-SDK-shaped session
events from `LLMEvent` so downstream consumers see one shape.
What this does NOT do (deferred to later phases):
- No tool support on the native path (skipped, falls through).
- No parity harness yet; Phase 2 builds it.
- No production traffic; flag is off by default and no production
caller populates `nativeMessages`.
- No reasoning/cache/multi-modal coverage. Anthropic supports reasoning
and cache via existing patches, so those start working as soon as a
caller routes a real session through.
Verification: opencode typecheck clean, bridge tests still green
(33/0/0 across llm-native.test.ts + llm-bridge.test.ts); LLM package
tests green (123/0/0).
Kit Langton
fc3a1bfd34