Subagent Driven Development

Subagent-Driven Development (workflow-driven)

Execute a written plan by handing it to a deterministic Workflow. You (the controller, on the most capable model) do only what needs human judgment or Opus reasoning — plan parsing, conflict scan, model tiering, the go/no-go gate, and the irreversible finish. The background Workflow (workflows/sdd.mjs) runs the per-task loop as code so it cannot drift, skip a review, or rubber-stamp.

Why a workflow, not a flowchart: the implement → review → fix loop has known structure. Encoding it as control flow (not prose the model walks by hand) is the recommended pattern for known-structure tasks and removes the dominant agentic-SWE failure — verification theater / skipped steps. The model still fills every node's judgment; only the loop is fixed.

When to use

• A written plan exists with # Task N / ## Task N headings (what task-brief

parses) and the work has test coverage.

• Not for large, ambiguous, or brownfield work where the plan can't be

decomposed into independently testable tasks — elaborate task ceremony there creates review overload without guaranteeing compliance. Recommend smaller tasks or manual execution instead.

Controller process

1. Read the plan; capture Global Constraints verbatim

Note the project-wide requirements (exact values, formats, naming rules). They bind every task and are passed to every agent.

2. Pre-flight conflict scan

Scan the plan once for tasks that contradict each other or the Global Constraints, and for plan text that mandates something the review rubric treats as a defect (a test that asserts nothing, verbatim-duplicated logic). Present everything you find as one batched question — each finding beside the plan text that mandates it — before execution. If the scan is clean, proceed silently. The workflow returns any plan-conflicts the reviewers surface later; you adjudicate those after the run, not mid-run.

3. Ensure an isolated worktree

Never start implementation on main/master without explicit user consent. Create or confirm a feature branch / worktree to work in (this is self-contained — do not rely on the disabled using-git-worktrees skill):

git rev-parse --abbrev-ref HEAD            # confirm not on main/master
# if needed: git worktree add ../wt- -b    (or branch in place)

The worktree root is workdir; all agents run there. mergeBase is where the branch started: git merge-base main HEAD.

4. Enumerate tasks with tier hints and honest deps

Turn the plan into a lightweight list — no pasted task text, just { n, title, tier, deps }. Assign tier per task with the complexity signals:

| Signal | Tier | |--------|------| | 1–2 files, complete spec, transcription/mechanical | haiku | | multi-file, integration concerns (default floor) | sonnet | | design judgment, broad codebase understanding | opus |

Default to the sonnet floor when unsure; the BLOCKED escalation ladder self-corrects a mis-tier at runtime.

deps is the parallelism contract. Tasks whose deps are all satisfied run concurrently in sibling worktrees (waves), so mark a dep wherever task B touches files task A creates/changes or builds on its behavior. Prefer file-disjoint decomposition when the plan allows it. When unsure, mark the dep — sequential is the safe default.

5. Show conflicts + task list + tiers; wait for the go-ahead

Present the batched conflicts (if any) and the task list with tiers and the computed waves (group tasks by dependency level), so the human sees exactly what will run in parallel before saying "go". Wait for explicit "go" before dispatching. "Execute the plan" is permission for the topic, not for the dispatch.

6. Resolve install paths and invoke the Workflow

CLAUDE_PLUGIN_ROOT is not available at runtime, so glob the install and pick the highest version (in local dev, use the repo path directly):

ls -d "$HOME"/.claude/plugins/cache/jasonm4130-claude-skills/subagent-driven-development/*/workflows/sdd.mjs | sort -V | tail -1

pluginDir is the directory containing workflows/, prompts/, and scripts/ (the parent of the resolved sdd.mjs's workflows/). Then:

Workflow({ scriptPath: "", args: {
  planPath: "",
  workdir: "",
  pluginDir: "",
  globalConstraints: "",
  mergeBase: "",
  tasks: [ { n: 1, title: "...", tier: "sonnet", deps: [] }, ... ],
  setupCmd: "",
  testCmd: "",
  limits: { fixRounds: 2, escalateAttempts: 2, maxParallel: 4 }
}})

Tasks whose deps are all satisfied run concurrently (capped at limits.maxParallel), each in a sibling worktree -t; a sonnet merge agent integrates each wave in task order and runs the suite (testCmd, or inferred from implementer reports), with one bounded repair attempt. Linear plans (every task depending on the previous) run exactly as before.

Every agent the workflow dispatches gets an explicit model: (satisfies workflow-model-guard); none inherit your Opus session.

6a. ADR-driven dispatch (optional)

The adr skill drives this same Workflow from an ADR instead of a # Task N plan. It passes adrPath (an alias for planPath — the file task-brief reads, whose ### Task N Decomposition supplies the tasks) and successCriteria (the ADR's Success-criteria block, judged at the whole-branch step as the done-oracle). Everything else — tiering, escalation, the per-task gate, finishing — is identical.

7. On return: present, adjudicate, finish

The workflow returns { tasks, planConflicts, halted, finalReview, mergeBase, head, merges, ledgerPath, meta }.

• halted → { wave, reason, failures: [{ taskN, reason, reportPath }] }.

A wave can produce multiple failures (siblings run to completion and successful ones are merged before the halt). Wave-level reason covers merge-gate failures ("merge gate red after repair"); failures[] covers task-level ones. Failed tasks keep their worktree and branch for inspection. After you fix the plan/blocker, resume with Workflow({ scriptPath, resumeFromRunId }) (completed tasks return cached).

• merges → [{ wave, merged, headSha, testSummary }] — what each

wave's merge gate did.

• planConflicts → findings that conflict with what the plan mandates. You

decide which governs; the workflow never auto-fixes these.

• finalReview → whole-branch verdict + any ponytailDebt markers.
• Then drive finishing — present merge / PR / cleanup options and let the

user choose. Merging is irreversible and stays human-gated in this session; the workflow never merges. Default to gh pr merge --merge only when the user asks to merge.

Model tiering at a glance

| Role | Model | |------|-------| | implementer | task.tier (controller-assigned; sonnet floor) | | reviewer | opus if the task was opus, else sonnet | | fixer | sonnet | | final whole-branch review | opus |

Red flags — never

• Start on main/master without explicit consent.
• Paste task text into args (hand the workflow planPath; agents run

task-brief to materialize each brief as a file).

• Auto-merge, or act on planConflicts without asking.
• Dispatch an agent without an explicit model:.
• Invent independence: don't invent independence to force parallelism — when

unsure whether task B depends on task A, mark the dep.

Dependencies

• The plan must use # Task N / ## Task N headings.
• The nine superpowers post-plan skills stay disabled — this plugin is their

self-contained replacement.

• See ../../README.md, the design spec, and RESEARCH_subagent_driven_workflow.md.

Source & license

This open-source skill is cataloged on AgentStack and links to its original source — we do not rehost the code.

• Author: jasonm4130
• Source: jasonm4130/claude-skills
• License: MIT

Install and usage instructions live in the source repository linked above.