Subagent Driven Development

Subagent-Driven Development

Execute plan by dispatching fresh subagent per task, with two-stage review after each: spec compliance review first, then code quality review.

Why subagents: You delegate tasks to specialized agents with isolated context. By precisely crafting their instructions and context, you ensure they stay focused and succeed at their task. They should never inherit your session's context or history — you construct exactly what they need. This also preserves your own context for coordination work.

Core principle: Fresh subagent per task + two-stage review (spec then quality) = high quality, fast iteration

Continuous execution: Do not pause to check in with your human partner between tasks. Execute all tasks from the plan without stopping. The only reasons to stop are the four named below, or all tasks complete. "Should I continue?" prompts and progress summaries waste their time — they asked you to execute the plan, so execute it.

Rulings, not stalls. A running plan does not wait on a human. Conflicts, ambiguities, plan defects, a cap you would have asked to exceed — decide them. The spec is the binding authority, the plan is its argument, and your judgment settles what neither answers. Record every decision in the ledger as Ruling: <what you decided> — <why> — <what it costs if wrong>, and keep going. A wrong ruling costs rework your human partner can see and undo; a session parked on a question costs their whole day and buys nothing.

Four things stop you, and only these: an irreversible or destructive operation; a security-sensitive action; a side effect outside this worktree that norms say you ask about first (a merge, a push to a shared branch, a publish); and a plan so broken that every path forward is a guess. For those, stop and ask.

When to Use

digraph when_to_use {
    "Have implementation plan?" [shape=diamond];
    "Tasks mostly independent?" [shape=diamond];
    "subagent-driven-development" [shape=box];
    "Manual execution or brainstorm first" [shape=box];

    "Have implementation plan?" -> "Tasks mostly independent?" [label="yes"];
    "Have implementation plan?" -> "Manual execution or brainstorm first" [label="no"];
    "Tasks mostly independent?" -> "subagent-driven-development" [label="yes"];
    "Tasks mostly independent?" -> "Manual execution or brainstorm first" [label="no - tightly coupled"];
}

Plans come from superpowers:writing-plans. This skill executes one.

The Process

digraph process {
    rankdir=TB;

    subgraph cluster_per_task {
        label="Per Task";
        "invoke_subagent TypeName: implementer" [shape=box];
        "Implementer subagent asks questions?" [shape=diamond];
        "Answer questions, provide context" [shape=box];
        "Implementer subagent implements, tests, commits, self-reviews" [shape=box];
        "invoke_subagent TypeName: spec-reviewer" [shape=box];
        "Spec reviewer subagent confirms code matches spec?" [shape=diamond];
        "invoke_subagent TypeName: code-reviewer" [shape=box];
        "Code quality reviewer subagent approves?" [shape=diamond];
        "Fix loop (spec): resume implementer, scoped re-review (max 5 rounds/task)" [shape=box];
        "Fix loop (quality): resume implementer, scoped re-review (max 5 rounds/task)" [shape=box];
        "Update task.md artifact" [shape=box];
    }

    "Read plan, extract all tasks, create task.md artifact" [shape=box];
    "More tasks remain?" [shape=diamond];
    "Dispatch final code reviewer subagent for entire implementation" [shape=box];
    "Use superpowers:finishing-a-development-branch" [shape=box style=filled fillcolor=lightgreen];

    "Read plan, extract all tasks, create task.md artifact" -> "invoke_subagent TypeName: implementer";
    "invoke_subagent TypeName: implementer" -> "Implementer subagent asks questions?";
    "Implementer subagent asks questions?" -> "Answer questions, provide context" [label="yes"];
    "Answer questions, provide context" -> "invoke_subagent TypeName: implementer";
    "Implementer subagent asks questions?" -> "Implementer subagent implements, tests, commits, self-reviews" [label="no"];
    "Implementer subagent implements, tests, commits, self-reviews" -> "invoke_subagent TypeName: spec-reviewer";
    "invoke_subagent TypeName: spec-reviewer" -> "Spec reviewer subagent confirms code matches spec?";
    "Spec reviewer subagent confirms code matches spec?" -> "Fix loop (spec): resume implementer, scoped re-review (max 5 rounds/task)" [label="no"];
    "Fix loop (spec): resume implementer, scoped re-review (max 5 rounds/task)" -> "Spec reviewer subagent confirms code matches spec?" [label="round clean"];
    "Spec reviewer subagent confirms code matches spec?" -> "invoke_subagent TypeName: code-reviewer" [label="yes"];
    "invoke_subagent TypeName: code-reviewer" -> "Code quality reviewer subagent approves?";
    "Code quality reviewer subagent approves?" -> "Fix loop (quality): resume implementer, scoped re-review (max 5 rounds/task)" [label="no"];
    "Fix loop (quality): resume implementer, scoped re-review (max 5 rounds/task)" -> "Code quality reviewer subagent approves?" [label="round clean"];
    "Code quality reviewer subagent approves?" -> "Update task.md artifact" [label="yes"];
    "Update task.md artifact" -> "More tasks remain?";
    "More tasks remain?" -> "invoke_subagent TypeName: implementer" [label="yes"];
    "More tasks remain?" -> "Dispatch final code reviewer subagent for entire implementation" [label="no"];
    "Dispatch final code reviewer subagent for entire implementation" -> "Use superpowers:finishing-a-development-branch";
}

Setup

1. Ensure an isolated workspace: use superpowers:using-git-worktrees to create one or verify the existing one

Never:

• Start implementation on main/master branch without explicit user consent

• At skill start, resolve this plan's workspace: <repo-root>/.superpowers/sdd/<plan-basename>/ (plan filename without .md). Create it and the self-ignore rule in one command: mkdir -p .superpowers/sdd/<plan-basename> && printf '*\n' > .superpowers/.gitignore

Then open the ledger:

• If progress.md exists in this plan's directory, read it — tasks it marks complete are DONE; resume at the first task not marked complete.
• If it does not exist, create it now with its header line: # SDD ledger — plan: <plan file path>.

The four roles ship as bundled agents — implementer, spec-reviewer, code-reviewer, re-reviewer (defined in the plugin's agents/ directory). No registration step: dispatch them by TypeName. If a dispatch fails with an unknown TypeName, the plugin's agents are not being discovered — verify the plugin installation before working around it.

Workspace isolation per role:

Read the plan once, extract all tasks with full text and context, and create a task.md artifact tracking each task's status. If the plan names a Spec, read that too: the spec is the authority the plan argues from, and conflicts inside the plan resolve against it. A plan with no reachable spec gets a ledger note saying so — rulings made without one are provisional.

Pre-Flight Plan Review

Before dispatching Task 1, scan the plan once for conflicts, writing down what you checked as you check it:

• tasks that contradict each other or the plan's Global Constraints
• anything the plan explicitly mandates that the review rubric treats as a defect (a test that asserts nothing, verbatim duplication of a logic block)

The scan's output is a table, not a verdict. One row for every pair of tasks that share a file or an interface: the two tasks, what one produces against what the other consumes, and what you found. One row for every task: whether its own text agrees with itself — the tests it specifies against the code it specifies, the files it creates against the files it later touches. "The scan is clean" without those rows is not a scan you ran.

Write the table to the ledger. Rule on everything you find before execution begins — each finding against the plan text that mandates it — and record each ruling in the ledger. If the scan is clean, proceed without comment. Rule on each conflict it surfaces — the spec is the binding authority, the plan is its argument — record the ruling beside its row, and dispatch Task 1. The review loop remains the net for conflicts that only emerge from implementation.

Model Selection

Model tiers are set in each agent file's frontmatter (model: flash|pro|inherit). The four bundled roles live in the plugin's agents/ directory and all ship model: inherit — the session's model governs. To differentiate tiers, add a workspace-scoped variant at .agents/agents/<name>.md first — this is the primary escalation path — or edit the plugin's bundled agent files directly; editing plugin (or global) agent files may require the user's Agent Non-Workspace File Access setting to be enabled. Neither define_subagent nor invoke_subagent takes a model argument.

Use the least powerful tier that can handle each role to conserve cost and increase speed.

Mechanical implementation tasks (isolated functions, clear specs, 1-2 files): use a flash-tier agent type. Most implementation tasks are mechanical when the plan is well-specified.

Integration and judgment tasks (multi-file coordination, pattern matching, debugging): use a standard model.

Architecture, design, and review tasks: use a pro-tier agent type.

Task complexity signals:

• Touches 1-2 files with a complete spec → flash-tier agent type
• Touches multiple files with integration concerns → standard model
• Requires design judgment or broad codebase understanding → pro-tier agent type

The Task Loop

Batch small same-shape work. When the plan lists several tasks that are each a small, independent edit of the same kind — the same one-line fix, constant change, or field addition repeated across files — do not dispatch one subagent per task. Compose ONE dispatch brief listing every file and its change, send the whole batch to a single subagent, and review its diff as one unit. Reserve one-dispatch-per-task for work that needs its own judgment, its own tests, or its own review surface.

For each task, in plan order:

1. Fill implementer-prompt.md's dynamic template with the task's full text and scene-setting context, then dispatch: invoke_subagent(Subagents: [{TypeName: "implementer", Role: "Implement Task <N>", Prompt: <filled template>, Workspace: "branch"}]).
2. Record the implementer's conversation ID and its task branch name from the dispatch result — the fix loop and the ledger's commit range depend on both.
3. When the implementer reports DONE, run the two review stages in order: spec-reviewer first, then code-reviewer (dispatch templates in Prompt Templates below). Findings from either stage enter The Fix Loop.

Never:

• Dispatch multiple implementation subagents in parallel (conflicts)
• Make subagent read plan file (provide full text instead)
• Start code quality review before spec compliance is ✅ (wrong order)

Handling Implementer Status

Implementer subagents report one of four statuses. Handle each appropriately:

DONE: Proceed to spec compliance review.

DONE_WITH_CONCERNS: The implementer completed the work but flagged doubts. Read the concerns before proceeding. If the concerns are about correctness or scope, address them before review. If they're observations (e.g., "this file is getting large"), note them and proceed to review.

NEEDS_CONTEXT: The implementer needs information that wasn't provided. Send the missing context via send_message — the idle implementer resumes with its context intact.

BLOCKED: The implementer cannot complete the task. Assess the blocker:

1. If it's a context problem, resume or re-dispatch with more context
2. If the task requires more reasoning, raise the agent's tier — add a workspace-scoped variant at .agents/agents/<name>.md first, or edit the bundled agent's frontmatter to model: pro (may require Agent Non-Workspace File Access) — and re-dispatch
3. If the task is too large, break it into smaller pieces
4. If the plan itself is wrong, rule on the correction, ledger it, and re-dispatch with the ruling carried in the dispatch

Never ignore an escalation or force the same agent to retry without changes. If the implementer said it's stuck, something needs to change.

Terminal error: if manage_subagents Action: "list" shows the subagent in an error state (terminal failure — distinct from idle), it cannot be resumed; treat it as killed: dispatch a fresh implementer with the task text and the last known state.

Constructing Reviewer Prompts

Per-task reviews are task-scoped gates. The broad review happens once, at the final whole-branch review. When you fill a reviewer template:

• Do not add open-ended directives like "check all uses" or "run race tests if useful" without a concrete, task-specific reason
• Do not ask a reviewer to re-run tests the implementer already ran on the same code — the implementer's report carries the test evidence
• Do not pre-judge findings for the reviewer — never instruct a reviewer to ignore or not flag a specific issue. If you believe a finding would be a false positive, let the reviewer raise it and adjudicate it in the review loop. If the prompt you are writing contains "do not flag," "don't treat X as a defect," "at most Minor," or "the plan chose" — stop: you are pre-judging, usually to spare yourself a review loop.
• The global-constraints block you hand the reviewer is its attention lens. Copy the binding requirements verbatim from the plan's Global Constraints section or the spec: exact values, exact formats, and the stated relationships between components.
• A dispatch prompt describes one task, not the session's history. Do not paste accumulated prior-task summaries ("state after Tasks 1-3") into later dispatches. A fresh subagent needs its task, the interfaces it touches, and the global constraints. Nothing else.
• Spec-compliance failures (from the spec-reviewer) are always blocking — the implementer must fix them before proceeding to code quality review. The severity triage above (Critical/Important/Minor) applies to the code-quality reviewer's findings.
• A finding labeled plan-mandated — or any finding that conflicts with what the plan's text requires — is yours to rule on: weigh the finding against the plan text, decide with the spec as the binding authority, and ledger the ruling before you act on it. Do not dismiss the finding because the plan mandates it, and do not dispatch a fix that contradicts the plan without a recorded ruling.
• When a later dispatch touches an area with a parked finding, carry a one-line pointer to that ledger entry in the dispatch prompt.

The Fix Loop

When either reviewer returns findings, the same loop runs regardless of stage. Record the implementer's conversation ID at dispatch time — the loop depends on it.

Rounds 1–3 — resume the implementer. send_message the open findings verbatim to the implementer's conversation. The idle implementer re-awakens with its full context — the task, the code it wrote, its test knowledge — and fixes without re-reading anything. Every fix reply must name the covering tests it re-ran and show their results; do not dispatch the re-review until it does. Record Minor findings in the ledger as you go (Task N: minor (deferred): <one-liner>) and point the final whole-branch review at that list — a roll-up nobody reads is a silent discard.

Every round ends with a scoped re-review. Dispatch the re-reviewer (see re-review-prompt.md) with the findings and the fix range. It verdicts each finding ADDRESSED or NOT ADDRESSED and checks only the fix diff for new breakage — it cannot wander into a fresh full review. Out-of-scope observations go to the ledger, never back into the loop.

Rounds 4–5 — fresh implementer, takeover framing. If three resumed rounds haven't converged, the original implementer's approach may be the problem. Kill it (manage_subagents), dispatch a fresh implementer whose Prompt carries: the task text, the prior implementer's last report, and the open findings. Its first action is git checkout <task-branch> in its workspace so it continues the task's commits rather than starting over.

Round counting is shared per task, across both stages. Append Task <N>: fix round <R>/5 (<stage>: <one-line summary>) to the ledger each round.

At the cap — adjudicate. After round 5, stop dispatching. For each open finding, rule:

• Contested (implementer and reviewer disagree on whether it's real) — park it: ledger the finding and your ruling as Task <N>: parked — <finding> — Ruling: <why the code stands>.
• Real but not load-bearing for this task — park it the same way; the final review triages it.
• Real and load-bearing — a later task builds on it, or it reveals a plan defect: rule on the smallest change that unblocks the dependent work, ledger it as Task <N>: Ruling: <finding> — <what you decided and why>, and carry it into the next task's dispatch. Parking a structural failure silently lets every dependent task build on it. Stop only when the defect leaves every path forward a guess.

Adjudicate only at the cap. Never fix findings yourself in the controller session — controller fixes pollute your context and skip review.

Async Operations

Background Task Management

When implementers run long-running operations (builds, test suites, deployments), use manage_task instead of blocking:

For operations expected to take >30 seconds:

• Implementer should use run_command with a short WaitMsBeforeAsync (e.g., 500ms) to background it
• Check completion with manage_task Action: "status", paced by a schedule timer rather than a tight loop
• Use manage_task with kill to terminate stuck processes

When to background vs. wait:

digraph background_decision {
    "Operation expected >30s?" [shape=diamond];
    "Background with manage_task" [shape=box];
    "Wait synchronously" [shape=box];

    "Operation expected >30s?" -> "Background with manage_task" [label="yes"];
    "Operation expected >30s?" -> "Wait synchronously" [label="no"];
}

Agent Communication

Use send_message to communicate with subagents — running or idle. An idle (finished, not killed or errored) subagent re-awakens on receipt and retains its full context.

Answering questions mid-flight:

• When an implementer asks a question, use send_message with the implementer's conversation ID — this works whether it's still running or has gone idle
• Don't re-dispatch a new subagent just to answer a question — the original implementer has context

Providing additional context:

• If you realize an implementer needs more information after dispatch, use send_message to send it
• The implementer receives it as a message and can incorporate it into their work

When to use send_message vs. re-dispatch:

• Subagent (running or idle) needs info → send_message — an idle subagent resumes with its context intact
• Subagent reported NEEDS_CONTEXT → send the missing context via send_message; re-dispatch a fresh subagent only if the original was killed or in an error state
• Subagent reported BLOCKED → assess blocker, possibly resume with more context via send_message, break the task into smaller pieces, or dispatch a more capable custom agent type

If subagent asks questions:

• Answer clearly and completely
• Provide additional context if needed
• Don't rush them into implementation

Timeout Protection

Use schedule as a safety net for complex tasks:

digraph timeout {
    "Dispatch implementer" [shape=box];
    "Set one-shot timer" [shape=box];
    "Timer fires" [shape=box];
    "Implementer already responded?" [shape=diamond];
    "Treat as no-op reminder, move on" [shape=box];
    "Check subagent status and intervene" [shape=box];

    "Dispatch implementer" -> "Set one-shot timer";
    "Set one-shot timer" -> "Timer fires" [label="wait"];
    "Timer fires" -> "Implementer already responded?";
    "Implementer already responded?" -> "Treat as no-op reminder, move on" [label="yes"];
    "Implementer already responded?" -> "Check subagent status and intervene" [label="no"];
}

• Set a one-shot timer when dispatching implementers for complex tasks (5 minutes for standard tasks, 10 for complex ones)
• If the timer fires before the implementer responds, check status and intervene if needed
• The timer's Prompt fires unconditionally at the scheduled time — if the implementer already responded, treat the firing as a no-op reminder and move on; no cancellation is documented or needed

For test suites expected to take 5+ minutes, use a recurring schedule instead of a one-shot timer:

schedule(CronExpression: "*/2 * * * *", MaxIterations: "5", Prompt: "Check implementer status for Task N")

Subagent Monitoring

Use manage_subagents to track running subagents:

• Action: "list" — check which subagents are still running before dispatching the next task
• Action: "kill" — terminate stuck subagents that haven't responded after timeout

Don't poll in a loop — the system notifies you when subagents complete. Use manage_subagents only when you need an explicit status check (e.g., before cleanup or when a timer fires).

Durable Progress

Conversation memory does not survive compaction. In real sessions, controllers that lost their place have re-dispatched entire completed task sequences — the single most expensive failure observed. Track progress in a ledger file, not only in todos.

• The ledger is progress.md inside this plan's workspace directory (resolved in Setup). Its first line names the plan: # SDD ledger — plan: <plan file path>. A ledger whose first line names a different plan — or a stray ledger at the old flat .superpowers/sdd/progress.md — is another plan's progress: leave it and start fresh.
• Tasks listed in this plan's ledger as complete are DONE — do not re-dispatch them; resume at the first task not marked complete.
• When a task's review comes back clean, append one line to the ledger in the same message as your other bookkeeping: Task N: complete (commits <base7>..<head7>, review clean).
• The ledger is your recovery map: the commits it names exist in git even when your context no longer remembers creating them. After compaction, trust the ledger and git log over your own recollection.
• git clean -fdx will destroy the ledger (it's git-ignored scratch); if that happens, recover from git log.

Final Review

After all tasks are complete, dispatch a final code-reviewer subagent for the entire implementation — the one whole-branch review that per-task reviews don't cover.

• If the final whole-branch review returns findings, dispatch ONE fix subagent with the complete findings list — not one fixer per finding. Record its task branch name from the dispatch result: the fix subagent commits to its own branch, not to yours, so the fix range lives there.
• Then run exactly one scoped re-review of the fix wave: dispatch the re-reviewer (see re-review-prompt.md) with the findings and the fix range — the head the final review saw as the fix base, the fix branch's head as the head. The fix wave's commits, nothing earlier. Adjudicate any residual findings as in the task loop's breaker: park with rulings, or rule on the load-bearing ones and ledger what you decided. Only the four classes above stop you here. There is no second fix wave — residual load-bearing findings surface to your human partner when superpowers:finishing-a-development-branch presents the options.

Finish

Before you delete anything, collect every ledger line containing Ruling: — preflight rulings, parked findings, breaker adjudications, all of them — into your final message under "Rulings I made", in the order you made them, each with what it costs if wrong. The list is exhaustive: if the ledger holds a ruling, the list holds it. That list is the only place the decisions you took on your human partner's behalf reach them — they read it and rework whatever you got wrong. A ruling that dies with the workspace was a decision made in secret.

• When the final whole-branch review is clean, delete this plan's directory (rm -rf .superpowers/sdd/<plan-basename>) — git history is the durable record. Leave sibling plan directories alone.

Then hand off to superpowers:finishing-a-development-branch to complete the branch.

Common Rationalizations

Prompt Templates

• implementer-prompt.md (located in the subagent-driven-development skill directory) — dynamic dispatch template — the static role lives in agents/implementer.md
• spec-reviewer-prompt.md (located in the subagent-driven-development skill directory) — dynamic dispatch template — the static role lives in agents/spec-reviewer.md
• code-quality-reviewer-prompt.md (located in the subagent-driven-development skill directory) — dynamic dispatch template — the static role lives in agents/code-reviewer.md
• re-review-prompt.md (located in the subagent-driven-development skill directory) — dynamic dispatch template — the static role lives in agents/re-reviewer.md
• code-reviewer.md (located in the requesting-code-review skill directory) — dynamic dispatch template — the static role lives in agents/code-reviewer.md

Example Workflow

You: I'm using Subagent-Driven Development to execute this plan.

[Read plan file once: docs/superpowers/plans/feature-plan.md]
[Extract all 5 tasks with full text and context]
[Create task.md artifact with all tasks]

Task 1: Hook installation script

[Get Task 1 text and context (already extracted)]
[invoke_subagent TypeName: "implementer" with task text + context in Prompt]

Implementer: "Before I begin - should the hook be installed at user or system level?"

You: "User level (~/.config/superpowers/hooks/)"

Implementer: "Got it. Implementing now..."
[Later] Implementer:
  - Implemented install-hook command
  - Added tests, 5/5 passing
  - Self-review: Found I missed --force flag, added it
  - Committed

[invoke_subagent TypeName: "spec-reviewer"]
Spec reviewer: ✅ Spec compliant - all requirements met, nothing extra

[invoke_subagent TypeName: "code-reviewer"]
Code reviewer: Strengths: Good test coverage, clean. Issues: None. Approved.

[Update task.md: mark Task 1 complete]

Task 2: Recovery modes

[Get Task 2 text and context (already extracted)]
[invoke_subagent TypeName: "implementer" with task text + context in Prompt]

Implementer: [No questions, proceeds]
Implementer:
  - Added verify/repair modes
  - 8/8 tests passing
  - Self-review: All good
  - Committed

[invoke_subagent TypeName: "spec-reviewer"]
Spec reviewer: ❌ Issues:
  - Missing: Progress reporting (spec says "report every 100 items")
  - Extra: Added --json flag (not requested)

[send_message to implementer conversation: findings verbatim]
Implementer (resumed): Removed --json flag, added progress reporting. Re-ran test_recovery.py: 9/9 passing.
[invoke_subagent TypeName: "re-reviewer" — findings + fix range]
Re-reviewer: Both findings ADDRESSED. No new breakage in fix diff.
[Ledger: Task 2: fix round 1/5 (spec: json flag + progress reporting)]

[invoke_subagent TypeName: "code-reviewer"]
Code reviewer: Strengths: Solid. Issues (Important): Magic number (100)

[send_message to implementer conversation: findings verbatim]
Implementer (resumed): Extracted PROGRESS_INTERVAL constant. Re-ran full suite: 9/9 passing.
[invoke_subagent TypeName: "re-reviewer" — findings + fix range]
Re-reviewer: Finding ADDRESSED. No new breakage in fix diff.
[Ledger: Task 2: fix round 2/5 (quality: magic number extraction)]

[Update task.md: mark Task 2 complete]

...

[After all tasks]
[Dispatch final code-reviewer]
Final reviewer: All requirements met, ready to merge

Done!