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SKILL.md
subagent-driven-development.SKILL.md
---name: subagent-driven-development
description: Use when executing implementation plans with independent tasks in the current session
---# Subagent-Driven Development
Execute plan by dispatching a fresh implementer subagent per task, a task review (spec compliance + code quality) after each, and a broad whole-branch review at the end.
**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 + task review (spec + quality) + broad final review = high quality, fast iteration
**Narration:** between tool calls, narrate at most one short line — the
ledger and the tool results carry the record.
**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: BLOCKED status you cannot resolve, ambiguity that genuinely prevents progress, or all tasks complete. "Should I continue?" prompts and progress summaries waste their time — they asked you to execute the plan, so execute it.
## When to Use
```dot
digraph when_to_use {
"Have implementation plan?" [shape=diamond];
"Tasks mostly independent?" [shape=diamond];
"Stay in this session?" [shape=diamond];
"Dispatch final code reviewer subagent (../requesting-code-review/code-reviewer.md)" -> "Use superpowers:finishing-a-development-branch";
}
```
## Pre-Flight Plan Review
Before dispatching Task 1, scan the plan once for conflicts:
- 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)
Present everything you find to your human partner as one batched question —
each finding beside the plan text that mandates it, asking which governs —
before execution begins, not one interrupt per discovery mid-plan. If the
scan is clean, proceed without comment. The review loop remains the net for
conflicts that only emerge from implementation.
## Model Selection
Use the least powerful model that can handle each role to conserve cost and increase speed.
**Mechanical implementation tasks** (isolated functions, clear specs, 1-2 files): use a fast, cheap model. 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 and design tasks**: use the most capable available model.
The final whole-branch review is one of these — dispatch it on the most
capable available model, not the session default.
**Review tasks**: choose the model with the same judgment, scaled to the
diff's size, complexity, and risk. A small mechanical diff does not need the
most capable model; a subtle concurrency change does.
**Always specify the model explicitly when dispatching a subagent.** An
omitted model inherits your session's model — often the most capable and
most expensive — which silently defeats this section.
**Turn count beats token price.** Wall-clock and context cost scale with how
many turns a subagent takes, and the cheapest models routinely take 2-3× the
turns on multi-step work — costing more overall. Use a mid-tier model as the
floor for reviewers and for implementers working from prose descriptions.
When the task's plan text contains the complete code to write, the
implementation is transcription plus testing: use the cheapest tier for
that implementer. Single-file mechanical fixes also take the cheapest tier.
- Touches 1-2 files with a complete spec → cheap model
- Touches multiple files with integration concerns → standard model
- Requires design judgment or broad codebase understanding → most capable model
## Handling Implementer Status
Implementer subagents report one of four statuses. Handle each appropriately:
**DONE:** Generate the review package (`scripts/review-package BASE HEAD`, from this skill's directory — it prints the unique file path it wrote; BASE is the commit you recorded before dispatching the implementer — never `HEAD~1`, which silently drops all but the last commit of a multi-commit task), then dispatch the task reviewer with the printed path.
**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. Provide the missing context and re-dispatch.
**BLOCKED:** The implementer cannot complete the task. Assess the blocker:
1. If it's a context problem, provide more context and re-dispatch with the same model
2. If the task requires more reasoning, re-dispatch with a more capable model
3. If the task is too large, break it into smaller pieces
4. If the plan itself is wrong, escalate to the human
**Never** ignore an escalation or force the same model to retry without changes. If the implementer said it's stuck, something needs to change.
## Handling Reviewer ⚠️ Items
The task reviewer may report "⚠️ Cannot verify from diff" items — requirements
that live in unchanged code or span tasks. These do not block the rest of the
review, but you must resolve each one yourself before marking the task
complete: you hold the plan and cross-task context the reviewer
lacks. If you confirm an item is a real gap, treat it as a failed spec
review — send it back to the implementer and re-review.
## 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 ("same layout as X", "matches
Y"). The reviewer's template already carries the process rules (YAGNI,
test hygiene, review method) — the constraints block is for what THIS
project's spec demands.
- Hand the reviewer its diff as a file: run this skill's
`scripts/review-package BASE HEAD` and pass the reviewer the file path
it prints (or, without bash: `git log --oneline`, `git diff --stat`,
and `git diff -U10` for the range, redirected to one uniquely named
file). The output never enters your own context, and the reviewer sees
the commit list, stat summary, and full diff with context in one Read
call. Use the BASE you recorded before dispatching the implementer —
never `HEAD~1`, which silently truncates multi-commit tasks.
- 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 real session's dispatch hit 42k chars of which 99%
was pasted history. A fresh subagent needs its task, the interfaces it
touches, and the global constraints. Nothing else.
- Dispatch fix subagents for Critical and Important findings. Record Minor
findings in the progress ledger as you go, and point the final
whole-branch review at that list so it can triage which must be fixed
before merge. A roll-up nobody reads is a silent discard.
- A finding labeled plan-mandated — or any finding that conflicts with
what the plan's text requires — is the human's decision, like any plan
contradiction: present the finding and the plan text, ask which governs.
Do not dismiss the finding because the plan mandates it, and do not
dispatch a fix that contradicts the plan without asking.
- The final whole-branch review gets a package too: run
`scripts/review-package MERGE_BASE HEAD` (MERGE_BASE = the commit the
branch started from, e.g. `git merge-base main HEAD`) and include the
printed path in the final review dispatch, so the final reviewer reads
one file instead of re-deriving the branch diff with git commands.
- Every fix dispatch carries the implementer contract: the fix subagent
re-runs the tests covering its change and reports the results. Name the
covering test files in the dispatch — a one-line fix does not need the
whole suite. Before re-dispatching the reviewer, confirm the fix report
contains the covering tests, the command run, and the output; dispatch
the re-review once all three are present.
- If the final whole-branch review returns findings, dispatch ONE fix
subagent with the complete findings list — not one fixer per finding.
Per-finding fixers each rebuild context and re-run suites; a real
session's final-review fix wave cost more than all its tasks combined.
## File Handoffs
Everything you paste into a dispatch prompt — and everything a subagent
prints back — stays resident in your context for the rest of the session
and is re-read on every later turn. Hand artifacts over as files:
- **Task brief:** before dispatching an implementer, run this skill's
`scripts/task-brief PLAN_FILE N` — it extracts the task's full text to a
uniquely named file and prints the path. Compose the dispatch so the
brief stays the single source of requirements. Your dispatch should
contain: (1) one line on where this task fits in the project; (2) the
brief path, introduced as "read this first — it is your requirements,
with the exact values to use verbatim"; (3) interfaces and decisions
from earlier tasks that the brief cannot know; (4) your resolution of
any ambiguity you noticed in the brief; (5) the report-file path and
report contract. Exact values (numbers, magic strings, signatures, test
cases) appear only in the brief.
- **Report file:** name the implementer's report file after the brief
(brief `…/task-N-brief.md` → report `…/task-N-report.md`) and put it in
the dispatch prompt. The implementer writes the full report there and
returns only status, commits, a one-line test summary, and concerns.
- **Reviewer inputs:** the task reviewer gets three paths — the same brief
file, the report file, and the review package — plus the global
constraints that bind the task.
- Fix dispatches append their fix report (with test results) to the same
report file and return a short summary; re-reviews read the updated file.
## 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.
- At skill start, check for a ledger:
`cat "$(git rev-parse --show-toplevel)/.superpowers/sdd/progress.md"`. Tasks listed there
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
