# ADR-1143: Claude orchestration capability — Workflow tool (ultracode) as a runtime-gated loop execution backend [Proposed]

- **Status:** Proposed
- **Date:** 2026-06-12
- **Issue:** [#1143](https://github.com/open-gsd/gsd-core/issues/1143)
- **Builds on:** [ADR-857](857-capability-system.md) — host/core vs plug-in split, loop extension points, `runtimeCompat`, federated config
- **Blocked by:** [#857](https://github.com/open-gsd/gsd-core/issues/857) being **released** (Proposed → Accepted + capability infrastructure shipped). Not actionable until then.
- **Relates to:** [#853](https://github.com/open-gsd/gsd-core/issues/853) (Claude Code backgrounded agents cannot nest subagents), existing BETA skill `gsd-ultraplan-phase`

## Context

Claude Code ships two orchestration primitives GSD does not yet treat as first-class:

1. **`ultraplan`** (`/ultraplan <objective>`, `claude --teleport`) — hands a *planning* task to a Claude Code web session running in plan mode; the plan is drafted in the cloud, reviewed/commented in the browser, then approved back to the terminal (which archives the web session). GSD **already** wraps this as the BETA skill `gsd-ultraplan-phase` (`gsd-core/workflows/ultraplan-phase.md`), which constructs a plan prompt, triggers `/ultraplan`, and relies on the user manually running `/gsd:import --from <file>` to bring the plan back.

2. **`ultracode`** (`/effort ultracode`, or an `ultracode:` prompt prefix) — sets `xhigh` reasoning **plus automatic Workflow orchestration**. It is the trigger for the **Workflow tool** (Agent SDK ≥ v0.3.149): a deterministic JavaScript orchestrator that fans subagents out with `agent()`, `parallel()` (barrier), `pipeline()` (no barrier), and `phase()`, supporting `isolation: 'worktree'`, a shared token `budget`, custom `agentType`, and `resumeFromRunId`. It can be activated per-session via `/effort`, `--settings`, or an Agent SDK control request (`"ultracode": true`). **GSD does not use the Workflow tool at all.**

### Why this matters for the loop

GSD's `execute-phase` is wave-based: plans carry a `wave` number, waves run sequentially, and plans *within* a wave run in parallel when their `files_modified` sets do not overlap. Today GSD realizes that by dispatching, one `Agent` call per message, a backgrounded `gsd-executor` in a worktree.

On **Claude Code** this degrades. Backgrounded agents on Claude Code have no `Agent`/`Task` tool, so they cannot nest subagents (#853). The autonomous loop therefore falls back to **inline sequential execution** — and with it silently drops wave parallelism, the plan-checker, and the verifier — on the single runtime most GSD users run. The degradation is structural and outside GSD's control to fix at the agent layer.

The Workflow tool sidesteps #853 precisely because it is invoked **from the main loop**, not from a backgrounded agent: the script *is* the orchestrator and spawns the subagents itself. Its primitives map almost 1:1 onto GSD's existing wave model, and it adds three things GSD's hand-rolled fan-out lacks: determinism, a shared token budget, and resume.

Post ADR-857, GSD now has a home for exactly this kind of runtime-specific, preview-grade, toggleable feature: a **Capability** with `runtimeCompat`, a federated config slice, a `tier`, and loop-hook registration at the stable extension points. Before 857 there was nowhere clean to put runtime-gated loop behavior without forking core prose; after 857 it is a data manifest plus a registry regen.

## Decision

Introduce a **Claude orchestration Capability** — `capabilities/claude-orchestration/`, `role: feature`, `runtimeCompat: claude`, **default-off, BETA** — that adopts Claude Code's orchestration primitives as optional, runtime-gated GSD surfaces. It is **blocked on #857 being released** and ships only after the capability infrastructure is Accepted.

### 1. Workflow tool as an optional loop execution backend (primary, NEW)

When the active runtime exposes the Workflow tool, `execute-phase` may emit a generated **Workflow script** in place of manual one-agent-per-message dispatch. The translation preserves GSD's existing model:

| GSD execute-phase concept | Workflow primitive |
|---|---|
| Wave (barrier between waves) | `parallel()` barrier; or `pipeline()` when plans flow through stages without a cross-plan barrier |
| Plan executor | `agent(brief, { agentType: 'gsd-executor', isolation: 'worktree' })` |
| `files_modified` overlap forces sequential | overlap forces the plan into a later pipeline stage (same rule, declaratively) |
| Cost discipline | the Workflow `budget` pool |
| Resume / `gsd-undo` | `resumeFromRunId` keyed to the phase manifest |
| Orchestrator-only STATE.md / ROADMAP.md writes | unchanged — only the orchestrator (the script's return) writes shared files; executors stay in their worktrees |

Net effect on Claude Code: **wave parallelism, the plan-checker, and the verifier are restored** — the capability path is *not* a backgrounded agent, so #853 does not apply — and GSD gains determinism, a shared budget, and resume it does not have today.

### 2. Registration at ADR-857 loop extension points

The capability registers hooks at `execute:wave:pre`, `execute:wave:post`, and `execute:post`, resolved through `gsd_run loop render-hooks <point>`. Activation is gated by:

- **Runtime/tool detection** — the active runtime must actually expose the Workflow tool (Claude Code / Agent SDK ≥ the pinned minimum). Detection miss → no-op.
- **Federated config** — a `claude_orchestration.*` slice with `execution_backend: auto | workflow | inline` (default `auto`, which selects `workflow` only when the tool is present, else `inline`).

When neither gate passes, the loop runs exactly as it does today. This is the central safety property: **the inline/manual path remains the default and the only path on non-Claude runtimes and on Claude versions without the Workflow tool.**

### 3. Fold `ultraplan` under the same capability

The existing `gsd-ultraplan-phase` BETA skill and `commands/gsd/ultraplan-phase.md` become capability-owned at `plan:*`. Plan-offload (`ultraplan`) and execute-orchestration (`ultracode`/Workflow) then share one runtime gate, one federated config slice, and one BETA boundary — instead of `ultraplan` living as a stray BETA skill while a second preview surface is added elsewhere. This also lets a future iteration close `ultraplan`'s manual `/gsd:import --from` round-trip behind the same capability without touching core.

### 4. (Stretch) Other fan-out points opt into the same backend

`map-codebase` (parallel mappers), project/phase research (parallel researchers), and `plan-review-convergence` (parallel reviewers) are already manual `parallel`-shaped dispatches. Behind the same toggle and gate they can adopt the Workflow backend incrementally. Out of scope for the first cut; recorded so the capability is named for the general seam, not just execute-phase.

## Resolved design details

### Why a capability and not core

The Workflow tool is Claude Code / Agent SDK-specific and preview-grade. ADR-857 is explicit that the five-step loop plus shared-infrastructure skills are the privileged core and "every other feature is a Capability — a plug-in selectable at install and toggleable after restart." A runtime-specific, BETA execution backend is the textbook case for `role: feature` + `runtimeCompat: claude` + `tier`. Shipping it in core would re-introduce exactly the runtime-coupling 857 removed.

### Fallback is the contract, not an afterthought

The capability must be byte-for-byte transparent when absent: identical artifacts, commits, and STATE/ROADMAP writes whether a wave ran via the Workflow backend or the inline path. A parity regression test asserting this on a runtime without the Workflow tool is a release gate, not a nicety — it is what lets the capability be default-off and low-risk.

### Maintenance posture

The capability tracks two moving Claude-Code preview surfaces. Containment: one capability + BETA gate (mirroring today's `gsd-ultraplan-phase` BETA isolation), a pinned minimum Agent-SDK/Workflow-tool version in the runtime gate, and inline fallback on any detection miss. A preview-API change can degrade the capability to inline; it cannot break the core loop.

### Relationship to cross-AI delegation and plan-review-convergence

These existing multi-model features (`execute-phase` `cross_ai_delegation`, the convergence reviewer loop) are *model/runtime delegation*, not *intra-runtime fan-out orchestration*. They are orthogonal: cross-AI routes a plan to a different CLI; the Workflow backend parallelizes plans within the current Claude Code runtime. They compose rather than conflict.

## Consequences

- **Positive:** restores loop parallelism + plan-checker + verifier on Claude Code (undoing the #853 inline degradation); adds determinism, shared token budget, and resume to GSD execution; consolidates two Claude preview surfaces behind one gated capability; sets a reusable pattern for the other fan-out points.
- **Negative / cost:** another preview surface to track; a Workflow-script emitter and runtime/tool detection to maintain; BETA-grade until the upstream tool stabilizes.
- **Neutral:** no effect on non-Claude runtimes by construction; no behavior change until explicitly enabled.

> **Governance note:** This ADR is a *draft design* accompanying feature request #1143. Per CONTRIBUTING, it is PR'd only after the issue receives `approved-feature`, and the capability is implemented only after #857 is released.

## Amendment (2026-07-06): BETA v1 implementation landed

#857 is **released** (CLOSED); the capability infrastructure is live. The BETA v1
of this capability has shipped as `capabilities/claude-orchestration/` with the
scope agreed in the Decision, refined to the lowest-risk first slice:

- **Detection + emission** live as pure, fail-closed functions in
  `gsd-core/bin/lib/claude-orchestration.cjs` (source `src/claude-orchestration.cts`):
  `detectWorkflowBackend` (gate ladder: enabled → Claude runtime →
  execution_backend ≠ inline → host dispatch nested+background → valid Agent SDK
  → SDK ≥ `claude_orchestration.min_agent_sdk_version`, default `0.3.149`) and
  `emitWorkflowScript` (waves → `parallel()` stage barriers, plans →
  `agent({ agentType: 'gsd-executor', isolation: 'worktree' })`, `files_modified`
  overlap → separate sequential stages, `resumeFromRunId` wired to the phase run
  id, shared `budget(tokens)` pool). All interpolated values are validated as
  script-safe identifiers or JSON-quoted (review Finding 1).
- **Loop registration** is at the two **wired** points the loop host contract
  actually renders: `execute:wave:post into:executor` (Workflow-backend guidance)
  and `plan:post into:planner` (ultraplan ownership declaration). `execute:wave:pre`
  and `execute:pre` are declared in the contract but **not wired** today, so the
  capability registers at `wave:post` (the constraint `external-job` also documents).
- **Config** is federated (`claude_orchestration.enabled` default false /
  `activationKey`, `execution_backend` enum `auto|workflow|inline` default `auto`,
  `min_agent_sdk_version`); the keys live only in the registry, so uninstall
  removes them cleanly.
- **ultraplan ownership** is declared in the manifest (`plan:post` contribution);
  full install-profile migration of the `gsd-ultraplan-phase` skill into the
  capability's `skills[]` is deferred to a follow-up (it triggers the CLUSTERS /
  profile membership gate and is a heavier, install-machinery change).

Status remains **Proposed** — the BETA is default-off and the end-to-end Workflow
execution path (actual orchestration via the Workflow tool inside Claude Code) is
not verifiable outside that runtime. The capability is structurally complete and
tested at the contract level; flipping to Accepted follows maintainer sign-off on
the E2E behaviour once exercised on Claude Code with the Workflow tool present.