Summary

• Add a fixture-only bitfun-opencode-adapter crate with an empty public API and no production runtime dependencies.
• Use real OpenCode input shapes for the fixture: opencode.json plugin package list plus .opencode/plugins/*.ts local plugin source.
• Add boundary guards for production manifest dependencies, workspace dependency aliases, direct imports, and public re-exports before reviewed Plugin Runtime Host integration.
• Update product/plugin architecture docs to keep OpenCode support scoped to discovery/projection until the Host + Desktop/CLI vertical slice lands.

Scope and risk

• No production crate imports bitfun-opencode-adapter.
• cargo tree --edges normal for the new crate has no normal dependencies.
• No plugin JS/TS execution, no PluginRuntimeClient implementation, no executable availability, and no Product Assembly binding is introduced.
• Performance impact is limited to boundary-check scripts and test-only fixture code; no runtime path is changed.

Review notes

• Independent product review initially flagged a custom manifest-shaped fixture; fixed by switching to official OpenCode config/local plugin source shapes.
• Independent architecture review flagged workspace alias and pub use guard gaps; fixed with checker and self-test coverage.
• Follow-up adversarial architecture review flagged two additional boundary bypasses: BitFun-Installer/src-tauri was outside the OpenCode dependency/import scan roots, and package = 'bitfun-opencode-adapter' single-quoted aliases bypassed manifest matching. Both are now guarded with self-test coverage.
• Final subagent re-review found no remaining Critical or Important issues.

Verification

• git fetch gcwing main
• git rev-list --left-right --count gcwing/main...HEAD -> 0 1
• node scripts/check-core-boundaries.mjs
• node --test scripts/check-core-boundaries.test.mjs
• cargo check -p bitfun-opencode-adapter
• cargo test -p bitfun-opencode-adapter opencode_fixture_contracts
• cargo tree -p bitfun-opencode-adapter --edges normal --depth 1
• cargo metadata --no-deps --format-version 1
• git diff --check gcwing/main..HEAD