Project-level skills missing from available-skills in REST API sessions #25686

Description

Project-level skills (from .opencode/skills/) are missing from the <available-skills> system prompt block in sessions created via the REST API (POST /session + POST /session/{id}/prompt_async). Only user-level skills (~/.config/opencode/skills/) appear. Calling use_skill("project-skill") returns "not found".

Interactive sessions (TUI/web) see all skills correctly.

OpenCode version

1.0.203+

Steps to reproduce

1. Create a project with skills in .opencode/skills/
2. Start opencode serve
3. Create a session via REST API: POST /session with directory pointing to the project
4. Send a prompt: POST /session/{id}/prompt_async
5. Observe: <available-skills> only shows user-level skills
6. use_skill("project-skill") returns "not found"

Root Cause

Skill.state and Skill.discovered use InstanceState, which is backed by Effect's ScopedCache. The ScopedCache.make constructor captures the Effect context at construction time and merges it into lookup calls via effect.updateContext (see effect/ScopedCache.ts:82-85):

self.lookup = (key: Key): Effect.Effect<A, E> =>
  effect.updateContext(
    options.lookup(key),
    (input) => Context.merge(context, input)
  )

When InstanceState.make runs during app initialization, InstanceRef is not in scope. The captured context therefore lacks InstanceRef, and all subsequent ScopedCache.get lookups merge this stale context — even when the calling fiber has InstanceRef provided via Effect.provideService(InstanceRef, ...).

The lookup's yield* context resolves (yield* InstanceRef) ?? Instance.current. Without InstanceRef, it falls back to Instance.current (Node ALS), which is empty after the REST API middleware returns its 204 response. The skill discovery then receives the wrong context, causing Config.directories() to skip the project's .opencode directory.

Evidence: The permission system correctly resolves all project skills (permissions include ops-* paths from .opencode/skills/) because permission evaluation runs in the calling fiber's context. But Skill.available() goes through ScopedCache.get() → lookup() in a scope without InstanceRef.

Fix

In InstanceState.get(), eagerly resolve InstanceContext via yield* context (where InstanceRef IS available in the calling fiber), then pipe Effect.provideService(InstanceRef, ctx) onto the ScopedCache.get call. This propagates the instance context into the ScopedCache lookup scope.

export const get = <A, E, R>(self: InstanceState<A, E, R>) =>
  Effect.gen(function* () {
    const ctx = yield* context
    return yield* ScopedCache.get(self.cache, ctx.directory).pipe(
      Effect.provideService(InstanceRef, ctx),
    )
  })

Distinction from similar issues

• Skill tool shows empty available_skills list #7069 — Empty available_skills list entirely (closed, different symptom)
• [BUG]: Project-level skills not discovered when .claude/skills is a symlink in git worktree sandbox #18848 — Skills not discovered when .claude/skills is a symlink in git worktree (glob traversal issue, different root cause)