Planning And Task Breakdown

Planning and Task Breakdown

Overview

The difference between a project that ships on time and one that spirals into endless rework is rarely the complexity of the work — it's the clarity of the plan. Vague tasks breed vague results. A task that says "build auth" will produce a mess. A task that says "implement password validation with bcrypt, rate limiting at 5 attempts per IP, and return 429 on lockout" produces something you can verify.

The planning contract: Every task must have a clear verb, a specific scope, and verifiable acceptance criteria. If you can't describe "done" in one sentence, the task is too big. Break it down until each piece is independently implementable, testable, and reviewable.

Real-world impact: Teams with explicit task breakdowns ship 2x faster and have 50% fewer scope-creep issues. The 10 minutes spent decomposing work saves hours of "wait, I also need to..." mid-implementation pivots.

When to Use

• You have a spec and need to break it into implementable units
• A task feels too large or vague to start
• Work needs to be parallelized across multiple agents or sessions
• You need to communicate scope to a human
• The implementation order isn't obvious

When NOT to use: Single-file changes with obvious scope, or when the spec already contains well-defined tasks.

The Planning Process

Step 1: Enter Plan Mode

Before writing any code, operate in read-only mode:

• Read the spec and relevant codebase sections
• Identify existing patterns and conventions
• Map dependencies between components
• Note risks and unknowns

Do NOT write code during planning. The output is a plan document, not implementation.

Step 2: Identify the Dependency Graph

Map what depends on what:

Database schema
    │
    ├── API models/types
    │       │
    │       ├── API endpoints
    │       │       │
    │       │       └── Frontend API client
    │       │               │
    │       │               └── UI components
    │       │
    │       └── Validation logic
    │
    └── Seed data / migrations

Implementation order follows the dependency graph bottom-up: build foundations first.

Step 3: Slice Vertically

Instead of building all the database, then all the API, then all the UI — build one complete feature path at a time:

Bad (horizontal slicing):

Task 1: Build entire database schema
Task 2: Build all API endpoints
Task 3: Build all UI components
Task 4: Connect everything

Good (vertical slicing):

Task 1: User can create an account (schema + API + UI for registration)
Task 2: User can log in (auth schema + API + UI for login)
Task 3: User can create a task (task schema + API + UI for creation)
Task 4: User can view task list (query + API + UI for list view)

Each vertical slice delivers working, testable functionality.

Step 4: Write Tasks

Each task follows this structure:

## Task [N]: [Short descriptive title]

**Description:** One paragraph explaining what this task accomplishes.

**Acceptance criteria:**
- [ ] [Specific, testable condition]
- [ ] [Specific, testable condition]

**Verification:**
- [ ] Tests pass: `npm test -- --grep "feature-name"`
- [ ] Build succeeds: `npm run build`
- [ ] Manual check: [description of what to verify]

**Dependencies:** [Task numbers this depends on, or "None"]

**Files likely touched:**
- `src/path/to/file.ts`
- `tests/path/to/test.ts`

**Estimated scope:** [Small: 1-2 files | Medium: 3-5 files | Large: 5+ files]

Step 5: Order and Checkpoint

Arrange tasks so that:

1. Dependencies are satisfied (build foundation first)
2. Each task leaves the system in a working state
3. Verification checkpoints occur after every 2-3 tasks
4. High-risk tasks are early (fail fast)

Add explicit checkpoints:

## Checkpoint: After Tasks 1-3
- [ ] All tests pass
- [ ] Application builds without errors
- [ ] Core user flow works end-to-end
- [ ] Review with human before proceeding

Task Sizing Guidelines

| Size | Files | Scope | Example | |------|-------|-------|---------| | XS | 1 | Single function or config change | Add a validation rule | | S | 1-2 | One component or endpoint | Add a new API endpoint | | M | 3-5 | One feature slice | User registration flow | | L | 5-8 | Multi-component feature | Search with filtering and pagination | | XL | 8+ | Too large — break it down further | — |

If a task is L or larger, it should be broken into smaller tasks. An agent performs best on S and M tasks.

When to break a task down further:

• It would take more than one focused session (roughly 2+ hours of agent work)
• You cannot describe the acceptance criteria in 3 or fewer bullet points
• It touches two or more independent subsystems (e.g., auth and billing)
• You find yourself writing "and" in the task title (a sign it is two tasks)

Plan Document Template

# Implementation Plan: [Feature/Project Name]

## Overview
[One paragraph summary of what we're building]

## Architecture Decisions
- [Key decision 1 and rationale]
- [Key decision 2 and rationale]

## Task List

### Phase 1: Foundation
- [ ] Task 1: ...
- [ ] Task 2: ...

### Checkpoint: Foundation
- [ ] Tests pass, builds clean

### Phase 2: Core Features
- [ ] Task 3: ...
- [ ] Task 4: ...

### Checkpoint: Core Features
- [ ] End-to-end flow works

### Phase 3: Polish
- [ ] Task 5: ...
- [ ] Task 6: ...

### Checkpoint: Complete
- [ ] All acceptance criteria met
- [ ] Ready for review

## Risks and Mitigations
| Risk | Impact | Mitigation |
|------|--------|------------|
| [Risk] | [High/Med/Low] | [Strategy] |

## Open Questions
- [Question needing human input]

Parallelization Opportunities

When multiple agents or sessions are available:

• Safe to parallelize: Independent feature slices, tests for already-implemented features, documentation
• Must be sequential: Database migrations, shared state changes, dependency chains
• Needs coordination: Features that share an API contract (define the contract first, then parallelize)

Common Rationalizations

| Rationalization | Reality | |---|---| | "I'll figure it out as I go" | That's how you end up with a tangled mess and rework. 10 minutes of planning saves hours. | | "The tasks are obvious" | Write them down anyway. Explicit tasks surface hidden dependencies and forgotten edge cases. | | "Planning is overhead" | Planning is the task. Implementation without a plan is just typing. | | "I can hold it all in my head" | Context windows are finite. Written plans survive session boundaries and compaction. |

Red Flags

• Tasks described with verbs like "implement" or "build" without specifying what done looks like
• Tasks that depend on 3+ other tasks (too much coupling)
• No checkpoint defined between tasks (impossible to verify progress)
• Plan created without reading existing code first (reinvents conventions)

• Starting implementation without a written task list
• Tasks that say "implement the feature" without acceptance criteria
• No verification steps in the plan
• All tasks are XL-sized
• No checkpoints between tasks
• Dependency order isn't considered

See Also

• [spec-driven-development](skills/spec-driven-development/SKILL.md)
• [incremental-implementation](skills/incremental-implementation/SKILL.md)
• [interview-me](skills/interview-me/SKILL.md)

Verification

• [ ] Each task can be completed in under 2 hours of focused work
• [ ] Plan includes explicit checkpoint after every 2-3 tasks
• [ ] Riskiest tasks are scheduled first (fail-fast ordering)

Before starting implementation, confirm:

• [ ] Every task has acceptance criteria
• [ ] Every task has a verification step
• [ ] Task dependencies are identified and ordered correctly
• [ ] No task touches more than ~5 files
• [ ] Checkpoints exist between major phases
• [ ] The human has reviewed and approved the plan

Source & license

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

• Author: borhen68
• Source: borhen68/SkillEngine
• License: MIT

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