Native Harness run streams in Studio

Traceability

• Spec ID: 2026-09-01-harness-native-studio-stream
• Status: Implemented

Intent

Remove AG-UI from the Harness Studio application path. Studio should execute, stream, render, and retain runs through the host-neutral HarnessRunEvent contract owned by @qoder-ai/harness, without translating those events into a second protocol that has no independent Studio consumer.

The obsolete @qoder-ai/harness-ui AG-UI adapter is removed rather than kept as a compatibility branch. Git history remains the recovery path; the application and repository no longer carry its second run protocol, server, CLI, or release practice. The package name was subsequently reused by the private organization Dashboard defined in 2026-09-01-organization-harness-dashboard; that application does not restore AG-UI or Agent execution.

Acceptance Scenarios

• AC-1 — Core run orchestration: @qoder-ai/harness/exec exposes one executor-injected run function that compiles, locks, resolves, and executes a Harness while producing a complete neutral HarnessRunEvent lifecycle for success and pre-execution, executor, and non-zero-exit failures.
• AC-2 — Versioned browser contract: @qoder-ai/harness/protocol owns a browser-safe run request and sequenced stream envelope. Studio validates the request and streams those envelopes over its same-origin local endpoint.
• AC-3 — Native Debugger projection: the Studio Run view folds neutral Harness events directly into the existing message, Tool Call, warning, permission, result, and terminal UI states. Duplicate or replayed sequence numbers do not append deltas twice.
• AC-4 — No application AG-UI dependency: production and test code under packages/harness-studio has no import from @qoder-ai/harness-ui, no /agui route, no AG-UI-named state/config/endpoint, and no AG-UI product copy.
• AC-5 — Domain-native Artifact streams: Artifact Agent progress and AgentReact observations use their own browser-safe Studio contracts instead of AG-UI CUSTOM envelopes.
• AC-6 — Retained evidence compatibility: previously saved Debugger run JSON remains readable because its persisted timeline shape is unchanged; new retained Sessions identify their protocol as Harness run evidence.
• AC-7 — Adapter removal: the legacy packages/harness-ui adapter source, release choice, root scripts, CI steps, package-lock dependency entry, and current product documentation are removed. Historical specs may retain factual references to the superseded implementation. A later private Dashboard may reuse the workspace name without restoring the adapter.
• AC-8 — Product verification: focused unit/server tests, Studio typecheck, the full Studio suite, and changed-surface Playwright checks pass without browser console or page errors at wide, compact, and narrow layouts.

Non-goals

• Treating the loopback Studio server as a Team or Org gateway.
• Adding remote authentication, tenancy, persistence, upload, or Control Plane APIs.
• Redesigning the Debugger information architecture or visual language.
• Migrating historical specs that accurately describe earlier AG-UI behavior.

Plan and Tasks

1. Move generic compile/resolve/execute orchestration into packages/harness/src/exec/run.ts and keep executors injected.
2. Add browser-safe request and sequenced event-envelope contracts under packages/harness/src/protocol/ with no Node or host SDK dependencies.
3. Add a Studio-owned same-origin run stream handler and route local Harness and ACP execution through it.
4. Replace agui-store with a native run-store, preserving the timeline and saved-record shape while adding sequence replay protection.
5. Replace Artifact Agent and AgentReact AG-UI custom envelopes with domain-specific Studio contracts.
6. Remove the Studio package dependency, AG-UI labels, route names, imports, and test fixtures. Keep the retained timeline JSON schema unchanged without introducing a protocol compatibility branch.
7. Delete @qoder-ai/harness-ui and remove its workspace, CI, release, lockfile, documentation, and Studio dependency surfaces.

The package decision is intentionally smaller: neutral execution and wire contracts belong to Harness; application projection and local transport belong to Studio. No package remains solely for AG-UI interoperability.

Test and Review Evidence

• AC-1/AC-2/AC-7: focused @qoder-ai/harness run and protocol tests plus legacy adapter source, CI, release, lockfile, and dependency inspection.
• AC-3/AC-5/AC-6: focused Studio run-store, Artifact Agent, AgentReact, run-log, and server tests using parsed event objects rather than source-text matching.
• AC-4: dependency and route inspection plus package build/typecheck. The application check is scoped to packages/harness-studio; superseded specs retain factual AG-UI references only as historical decision records.
• AC-8: npm run typecheck -w @qoder-ai/harness-studio, npm test -w @qoder-ai/harness-studio, and focused Playwright runs against a built preview at 1440x900, 1024x768, and 390x844 with console/page-error inspection and screenshots.

Primary risks are an incomplete terminal lifecycle after moving orchestration, double-applying streamed deltas after reconnection, breaking pending ACP permission handling, or accidentally changing the persisted timeline shape. The tests must exercise each risk directly.

Implemented verification:

• npm test -w @qoder-ai/harness — 22 files, 179 tests passed.
• npm run typecheck -w @qoder-ai/harness-studio — passed.
• npm test -w @qoder-ai/harness-studio — 65 files, 507 tests passed.
• npx vitest run test/skills-docs/doc-link-graph.test.mjs — 8 tests passed.
• npx playwright test test/browser/acp-debugger.spec.mjs — wide, compact, and narrow Debugger interaction passed with no console or page errors.
• Sequential npm pack --dry-run checks passed for @qoder-ai/harness and @qoder-ai/harness-studio.