Planning and Task Breakdown

Overview

Decompose work into small, verifiable tasks with explicit acceptance criteria. Good task breakdown is the difference between an agent that completes work reliably and one that produces a tangled mess. Every task should be small enough to implement, test, and verify in a single focused session.

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 is not obvious

When NOT to use: Single-file changes with obvious scope, when the spec already contains well-defined tasks, when the request is still too ambiguous and should go through spec-first-brainstorming, or when deep TypeScript/Node backend sequencing belongs in typescript-coder-plan-spec.

Repository-Specific Anchors

For opencode-setup, start by reading:

• AGENTS.md
• docs/specs/opencode-setup-prd/spec.md
• the relevant files under docs/, src/, and test/

Keep the current repository truth explicit while planning:

• do not plan as if the installer runtime already exists unless the task is specifically about building it
• preserve product and security invariants from AGENTS.md, especially around config targets, secret handling, and truthful scaffold status
• if the task changes contract, docs, packaging, or mirrored skills, include npm run ci in the checkpoint plan

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:

Product contract / repo truth
    |
    +- docs and CLI contract
    |      |
    |      +- runtime entrypoints and reserved install surfaces
    |      |      |
    |      |      +- tests and verification
    |      |
    |      +- contributor-facing guidance
    |
    +- security invariants / config layering

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

Step 3: Slice Vertically

Instead of planning all docs first, then all code, then all tests, prefer one complete slice at a time when possible.

Bad (horizontal slicing):

Task 1: Update all docs
Task 2: Implement all runtime code
Task 3: Update all tests
Task 4: Reconcile everything later

Good (vertical slicing):

Task 1: Add the new config contract and the tests that pin it
Task 2: Implement the CLI behavior for that contract
Task 3: Update README and security docs to match shipped behavior
Task 4: Run full verification and fix drift

Each slice should leave the repository in a more truthful, testable state.

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: [command]
- [ ] Build or contract checks pass: [command]
- [ ] Manual check: [description of what to verify]

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

**Files likely touched:**

- `src/path/to/file.ts`
- `test/path/to/test.ts`

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

For this repository, default to repo-real commands such as npm run ci when a task changes the public contract or mirrored skill pack.

Step 5: Order and Checkpoint

Arrange tasks so that:

1. Dependencies are satisfied first
2. Each task leaves the system in a working state
3. Verification checkpoints occur after every 2-3 tasks
4. High-risk or high-reversal-cost tasks happen early

Add explicit checkpoints:

## Checkpoint: After Tasks 1-3

- [ ] Focused tests pass
- [ ] `npm run ci` passes when contract surfaces changed
- [ ] Docs and implementation still describe the same truth
- [ ] Review with a human before proceeding

Task Sizing Guidelines

Size	Files	Scope	Example
XS	1	Single function or config change	Tighten one CLI validation rule
S	1-2	One component, test, or doc slice	Add one skill contract test
M	3-5	One feature slice	Add one new installer capability with docs and tests
L	5-8	Multi-surface feature	Introduce managed config writes across code, docs, and tests
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
• You find yourself writing and in the task title

Plan Document Template

# Implementation Plan: [Feature or Project Name]

## Overview

[One paragraph summary of what we are building]

## Architecture Decisions

- [Key decision 1 and rationale]
- [Key decision 2 and rationale]

## Repository Truth To Preserve

- [Current scaffold truth that must stay accurate]
- [Security or config invariant that constrains the work]

## Task List

### Phase 1: Foundation

- [ ] Task 1: ...
- [ ] Task 2: ...

### Checkpoint: Foundation

- [ ] Focused checks pass

### Phase 2: Core Changes

- [ ] Task 3: ...
- [ ] Task 4: ...

### Checkpoint: Core Changes

- [ ] End-to-end or contract flow works

### Phase 3: Truthfulness and Polish

- [ ] Task 5: ...
- [ ] Task 6: ...

### Checkpoint: Complete

- [ ] All acceptance criteria met
- [ ] `npm run ci` passes when required
- [ ] 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: Shared config contract changes, dependency chains, any step that redefines repository truth
• Needs coordination: Features that share a public CLI or config contract; define the contract first, then parallelize

Common Rationalizations

Rationalization	Reality
"I'll figure it out as I go"	That is how you end up with a tangled mess and rework. Ten 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

• 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 is not considered
• Planning that contradicts AGENTS.md about current scaffold truth or security invariants

Verification

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 about 5 files unless there is a stated reason
• Checkpoints exist between major phases
• The plan stays truthful to current opencode-setup reality
• The human has reviewed and approved the plan