Subagent-Driven Development: Execute Plans with Fresh Subagents and Tw

Subagent-Driven Development (SDD) is a structured execution pattern for turning implementation plans into working code. You dispatch a fresh subagent for each task, then run two separate reviews: one for spec compliance, one for code quality. This approach suits anyone who has a plan (from the plan skill or from user requirements) and wants automated, consistent quality checks between tasks without accumulating state across subagents.

What it does

SDD breaks an implementation plan into small, independent tasks. For each task, it spawns a dedicated implementer subagent, then a spec compliance reviewer, then a code quality reviewer. The subagents operate in isolation: each gets a clean context, the full task text, and project background. The two-stage review catches under-building, over-building, and quality issues before they compound. After all tasks pass, a final integration reviewer checks the whole implementation for consistency.

Before you start

You need an implementation plan. This skill executes plans, it does not create them. Use the plan skill or write one manually.
Tasks in the plan should be mostly independent. If tasks touch the same files, do not dispatch multiple implementation subagents for them in parallel.
The skill is optional and installed on demand. It lives at optional-skills/software-development/subagent-driven-development.
It runs on Linux, macOS, and Windows.
You need Hermes Agent installed and configured with the delegate_task function available.
The implementer subagents should follow TDD: write a failing test first, implement minimally, verify the test passes, then commit. Include TDD instructions in every implementer context.

The Process

1. Read and Parse Plan

Read the plan file once. Extract all tasks with their full text and context upfront. Create a todo list:

# Read the plan
read_file("docs/plans/feature-plan.md")

# Create todo list with all tasks
todo([
    {"id": "task-1", "content": "Create User model with email field", "status": "pending"},
    {"id": "task-2", "content": "Add password hashing utility", "status": "pending"},
    {"id": "task-3", "content": "Create login endpoint", "status": "pending"},
])

Key: Read the plan ONCE. Extract everything. Don't make subagents read the plan file, provide the full task text directly in context.

2. Per-Task Workflow

For EACH task in the plan:

Step 1: Dispatch Implementer Subagent

Use delegate_task with complete context:

delegate_task(
    goal="Implement Task 1: Create User model with email and password_hash fields",
    context="""
    TASK FROM PLAN:
    - Create: src/models/user.py
    - Add User class with email (str) and password_hash (str) fields
    - Use bcrypt for password hashing
    - Include __repr__ for debugging

    FOLLOW TDD:
    1. Write failing test in tests/models/test_user.py
    2. Run: pytest tests/models/test_user.py -v (verify FAIL)
    3. Write minimal implementation
    4. Run: pytest tests/models/test_user.py -v (verify PASS)
    5. Run: pytest tests/ -q (verify no regressions)
    6. Commit: git add -A && git commit -m "feat: add User model with password hashing"

    PROJECT CONTEXT:
    - Python 3.11, Flask app in src/app.py
    - Existing models in src/models/
    - Tests use pytest, run from project root
    - bcrypt already in requirements.txt
    """,
    toolsets=['terminal', 'file']
)

Step 2: Dispatch Spec Compliance Reviewer

After the implementer completes, verify against the original spec:

delegate_task(
    goal="Review if implementation matches the spec from the plan",
    context="""
    ORIGINAL TASK SPEC:
    - Create src/models/user.py with User class
    - Fields: email (str), password_hash (str)
    - Use bcrypt for password hashing
    - Include __repr__

    CHECK:
    - [ ] All requirements from spec implemented?
    - [ ] File paths match spec?
    - [ ] Function signatures match spec?
    - [ ] Behavior matches expected?
    - [ ] Nothing extra added (no scope creep)?

    OUTPUT: PASS or list of specific spec gaps to fix.
    """,
    toolsets=['file']
)

If spec issues found: Fix gaps, then re-run spec review. Continue only when spec-compliant.

Step 3: Dispatch Code Quality Reviewer

After spec compliance passes:

delegate_task(
    goal="Review code quality for Task 1 implementation",
    context="""
    FILES TO REVIEW:
    - src/models/user.py
    - tests/models/test_user.py

    CHECK:
    - [ ] Follows project conventions and style?
    - [ ] Proper error handling?
    - [ ] Clear variable/function names?
    - [ ] Adequate test coverage?
    - [ ] No obvious bugs or missed edge cases?
    - [ ] No security issues?

    OUTPUT FORMAT:
    - Critical Issues: [must fix before proceeding]
    - Important Issues: [should fix]
    - Minor Issues: [optional]
    - Verdict: APPROVED or REQUEST_CHANGES
    """,
    toolsets=['file']
)

If quality issues found: Fix issues, re-review. Continue only when approved.

Step 4: Mark Complete

todo([{"id": "task-1", "content": "Create User model with email field", "status": "completed"}], merge=True)

3. Final Review

After ALL tasks are complete, dispatch a final integration reviewer:

delegate_task(
    goal="Review the entire implementation for consistency and integration issues",
    context="""
    All tasks from the plan are complete. Review the full implementation:
    - Do all components work together?
    - Any inconsistencies between tasks?
    - All tests passing?
    - Ready for merge?
    """,
    toolsets=['terminal', 'file']
)

4. Verify and Commit

# Run full test suite
pytest tests/ -q

# Review all changes
git diff --stat

# Final commit if needed
git add -A && git commit -m "feat: complete [feature name] implementation"

Task Granularity

Each task = 2-5 minutes of focused work.

Too big:

"Implement user authentication system"

Right size:

"Create User model with email and password fields"
"Add password hashing function"
"Create login endpoint"
"Add JWT token generation"
"Create registration endpoint"

Red Flags, Never Do These

Start implementation without a plan
Skip reviews (spec compliance OR code quality)
Proceed with unfixed critical/important issues
Dispatch multiple implementation subagents for tasks that touch the same files
Make subagent read the plan file (provide full text in context instead)
Skip scene-setting context (subagent needs to understand where the task fits)
Ignore subagent questions (answer before letting them proceed)
Accept "close enough" on spec compliance
Skip review loops (reviewer found issues → implementer fixes → review again)
Let implementer self-review replace actual review (both are needed)
Start code quality review before spec compliance is PASS (wrong order)
Move to next task while either review has open issues

Handling Issues

If Subagent Asks Questions

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

If Reviewer Finds Issues

Implementer subagent (or a new one) fixes them
Reviewer reviews again
Repeat until approved
Don't skip the re-review

If Subagent Fails a Task

Dispatch a new fix subagent with specific instructions about what went wrong
Don't try to fix manually in the controller session (context pollution)

Efficiency Notes

Why fresh subagent per task:

Prevents context pollution from accumulated state
Each subagent gets clean, focused context
No confusion from prior tasks' code or reasoning

Why two-stage review:

Spec review catches under/over-building early
Quality review ensures the implementation is well-built
Catches issues before they compound across tasks

Cost trade-off:

More subagent invocations (implementer + 2 reviewers per task)
But catches issues early (cheaper than debugging compounded problems later)

Integration with Other Skills

With plan

This skill EXECUTES plans created by the plan skill:

User requirements → plan → implementation plan
Implementation plan → subagent-driven-development → working code

With test-driven-development

Implementer subagents should follow TDD:

Write failing test first
Implement minimal code
Verify test passes
Commit

Include TDD instructions in every implementer context.

With requesting-code-review

The two-stage review process IS the code review. For final integration review, use the requesting-code-review skill's review dimensions.

With systematic-debugging

If a subagent encounters bugs during implementation:

Follow systematic-debugging process
Find root cause before fixing
Write regression test
Resume implementation

Example Workflow

[Read plan: docs/plans/auth-feature.md]
[Create todo list with 5 tasks]

--- Task 1: Create User model ---
[Dispatch implementer subagent]
  Implementer: "Should email be unique?"
  You: "Yes, email must be unique"
  Implementer: Implemented, 3/3 tests passing, committed.

[Dispatch spec reviewer]
  Spec reviewer: ✅ PASS — all requirements met

[Dispatch quality reviewer]
  Quality reviewer: ✅ APPROVED — clean code, good tests

[Mark Task 1 complete]

--- Task 2: Password hashing ---
[Dispatch implementer subagent]
  Implementer: No questions, implemented, 5/5 tests passing.

[Dispatch spec reviewer]
  Spec reviewer: ❌ Missing: password strength validation (spec says "min 8 chars")

[Implementer fixes]
  Implementer: Added validation, 7/7 tests passing.

[Dispatch spec reviewer again]
  Spec reviewer: ✅ PASS

[Dispatch quality reviewer]
  Quality reviewer: Important: Magic number 8, extract to constant
  Implementer: Extracted MIN_PASSWORD_LENGTH constant
  Quality reviewer: ✅ APPROVED

[Mark Task 2 complete]

... (continue for all tasks)

[After all tasks: dispatch final integration reviewer]
[Run full test suite: all passing]
[Done!]

Remember

Fresh subagent per task
Two-stage review every time
Spec compliance FIRST
Code quality SECOND
Never skip reviews
Catch issues early

Quality is not an accident. It's the result of systematic process.

Subagent-Driven Development: Execute Plans with Fresh Subagents and Two-Stage Review