tmchow/iterative:tech-planning

Create Technical Plan

Turn a PRD or set of requirements into a structured, executable implementation plan. Write as if the implementer has zero context for the codebase — document the decisions, the reasoning, and enough detail that they can start working without asking clarifying questions.

The plan captures WHAT to build and WHERE. The implementer writes the actual code.

When to Use

• After iterative:brainstorming skill is complete
• When clear requirements exist and need an implementation plan
• Can be invoked standalone with existing requirements

If requirements are vague and no PRD exists, offer to start with iterative:brainstorming skill first.

Note on scope: Quick scope skips tech-planning entirely — the user implements directly from the brainstorming conversation. Standard scope may also skip tech-planning if the user chooses to implement directly from brainstorming's summary; tech-planning is invoked only when the user explicitly opts in. Full scope always uses tech-planning. Adapt plan depth to scope: a Standard-scope task doesn't need 5 parent tasks with 3 subtasks each — a flat checklist of 3-5 steps is sufficient. Full scope uses the complete structured plan format. Tech-planning is where the HOW lives — file paths, architecture decisions, implementation steps, test scenarios. This complements brainstorming's WHAT (requirements, scope, decisions).

Key Principles

1. Understand before structuring — Explore the codebase and ask questions before writing the plan
2. Decisions, not code — Capture architecture choices, query strategies, component boundaries, trade-offs. Leave method names, signatures, and implementation code to the implementer
3. Concrete test scenarios — Specific inputs, expected outputs, edge cases to cover. Not full test code, not "test that it works"
4. Test files are explicit — Every feature subtask must include the test file path in its **Files:** field. Test scenarios without a target test file get skipped during implementation
5. Right-sized subtasks — Scoped to a single atomic commit, typically touching 2-3 files. Not too big (5+ files, multiple unrelated changes), not too small (single line, no meaningful test)
6. Dependencies clear — Explicit ordering of what depends on what
7. Verification built-in — Each subtask has a way to confirm it works

Plan Quality Bar

Every plan must contain:

• File paths — Which files to create or modify
• Decisions with rationale — Architecture choices, query strategies, data flow, what was considered and rejected
• Test scenarios — Specific inputs, expected outputs, edge cases — not "verify it works"
• Test file paths — Every feature subtask includes the test file in **Files:** — no test file = tests won't get written
• Existing patterns to follow — Reference actual code in the codebase that the implementer should use as a model. Reference by function/class/pattern name, never by line number — line numbers drift as code changes
• What and why, not how — Describe what each subtask accomplishes and the key decisions driving it. Don't pre-write the implementation

A plan is ready when an implementer can start working without asking clarifying questions. They know what to build, where to build it, what decisions have been made, and what edge cases to handle. They write the code.

Workflow

Phase 0: Detect Resume / Assess Input

1. If user references an existing plan document or topic: load the document, summarize current state, and let the user direct what happens next. Build on existing content, update in place.
2. If no PRD AND requirements are vague: ask the user: A) Start with brainstorming first (recommended), B) Proceed with what we have. If brainstorming: invoke iterative:brainstorming skill.
3. Otherwise: proceed to Phase 1.

Phase 1: Gather Context (Q&A + Codebase Exploration)

1. Read PRD (if exists). Check both docs/prd/ and docs/brainstorms/ for existing documents. Also check docs/design-directions/ for design direction docs. If a PRD references a design direction doc, read both — the direction doc contains visual/UX decisions that inform implementation. If only a direction doc exists (no PRD), use it as the requirements input alongside any context from the brainstorming conversation.
2. Check for open questions. If the PRD has an Open Questions section, review each question. Technical questions (tagged [Affects ...] or implementation-related) should be investigated during codebase exploration below. Non-technical questions that remain unresolved may need the user's input — flag them early.
3. Explore the codebase for: existing patterns and conventions to follow, files and modules that will be affected, test patterns and frameworks in use, related code that informs the design.
4. Resolve technical open questions. As codebase exploration answers PRD questions, note the resolution. These findings may trigger PRD updates (see PRD Alignment below).
5. Ask implementation-focused questions ONE AT A TIME: architecture preferences, highest risk areas, testing approach, constraints not in the PRD, existing code patterns to follow or avoid.
6. Gate: continue until approach is clear OR user says "proceed."
7. Do NOT start writing the plan until this phase is complete.

Phase 2: Structure the Plan

1. Identify major components (become parent tasks, typically 2-5).
2. Break each into subtasks (2-5 per parent, one commit each).
3. Use the standardized subtask format (see template) — every subtask has the same fields so it can be directly converted into tasks.
4. For each subtask, define: dependencies on other subtasks (always present, even if "none"), files to create or modify (including test files for feature subtasks), what the subtask accomplishes and key decisions, test scenarios with specific inputs and expected outputs, how to verify it works.
5. Number subtasks as Parent.Subtask (1.1, 1.2, 2.1) for cross-referencing.

Phase 3: Write Technical Plan

1. Branch safety gate. Before the first commit, check if on the default branch (main/master). If so, offer: A) Create a feature branch (recommended), B) Continue on default branch. This is a one-time check — once resolved, all subsequent commits in this session go to the chosen branch. Skip if brainstorming already handled this (i.e., already on a feature branch).
2. Create plan document using template in references/tech-plan-template.md.
3. Every subtask must meet the Plan Quality Bar above.
4. Reference actual file paths, existing patterns, and conventions from Phase 1.
5. Save to docs/plans/YYYY-MM-DD-<topic>-tech-plan.md (ensure directory exists).
6. Commit the plan. Don't leave it as an uncommitted change.

Phase 4: Review and Handoff

1. Present an interactive choice to the user — AskUserQuestion (Claude Code) or request_user_input (Codex): A) Review the plan (recommended), B) Start implementing, C) I'll take it from here (exit).
2. If review: invoke plan-review skill. Plan-review returns findings — tech-planning owns the fix loop.
3. Fix issues identified by plan-review. Commit the updated plan.
4. Present an interactive choice — see recommendation logic below: A) Another review round, B) Start implementing, C) I'll take it from here (exit).
5. Repeat steps 2-4 if user chooses another round.
6. If user chooses implementing: invoke iterative:implementing skill (implementing handles task creation internally after reading the plan).

Recommendation logic for step 4. Shift the recommended option based on what the review found:

• Review found HIGH issues (now fixed) → recommend another review round to verify the fixes landed well
• Review found only MEDIUM/LOW issues, or a round came back with no findings → recommend start implementing — further rounds will have diminishing returns
• After 3+ rounds → recommend start implementing regardless, and note that additional passes are unlikely to surface significant issues

PRD Alignment

The PRD is a living document and the source of truth for requirements. Codebase exploration during Phase 1 may reveal that the PRD's chosen direction, scope, or requirements need to change. Keep it in sync — downstream code review validates against it.

• Minor adjustments (slightly different scope boundary, refined requirement wording): update the PRD in place and note the change when presenting the plan.
• Significant divergence (different approach than chosen direction, requirement added/removed, scope change): stop and discuss with the user before proceeding. Update the PRD's Chosen Direction, Requirements, and/or Scope sections to reflect the new reality. The tech plan should never contradict the PRD.
• New requirements discovered (codebase reveals constraints not in PRD): add them to the PRD's Requirements table with the appropriate priority (Core, Must, Nice) and a note that they were discovered during tech planning (e.g., "R6 added during tech planning — API requires backward compatibility").
• Open questions resolved (codebase exploration answers a PRD question): remove the question from Open Questions and update the affected section. If the answer changes a requirement's priority or scope boundary, update those sections too.

The tech plan's **PRD:** header links to the PRD document. If the PRD is updated during tech planning, this link ensures reviewers can find the authoritative requirements.

Anti-Patterns to Avoid

| Anti-Pattern | Better Approach | |--------------|-----------------| | Writing the plan before exploring the codebase | Explore existing code and patterns first | | Skipping Q&A when PRD exists | Still ask implementation-focused questions | | Subtasks that are too large (touch 5+ files) | Break into smaller, atomic units | | Vague descriptions ("implement the feature") | Specific: what to build, which files, what decisions, what edge cases | | Pre-writing implementation code in the plan | Describe what to build and the decisions; the implementer writes the code | | Test descriptions without specifics ("test that it works") | Concrete scenarios: specific inputs, expected outputs, edge cases | | Test scenarios without a test file in Files: | Every feature subtask includes the test file path — no test file = tests won't get written | | Planning without referencing existing code patterns | Ground every subtask in actual file paths and existing conventions | | Referencing code by line number (file.ts:42) | Reference by function/class/pattern name — line numbers drift as code changes | | Over-planning hypothetical scenarios | Plan only what's needed; defer decisions that can wait | | Diverging from the PRD without updating it | Update the PRD when approach changes — it's the requirements source of truth |

Transition Points

Always present options to the user at transition points using the platform's interactive question tool — AskUserQuestion (Claude Code) or request_user_input (Codex). Never print options as text or end the turn without presenting a choice.

After technical plan is written, and after each review round, present options:

• Review the plan — specialized agents analyze for issues (recommended on first pass)
• Start implementing (recommended when prior review found only Medium/Low issues or after 3+ rounds)
• I'll take it from here (exit)

Additional Resources

Reference Files

For detailed templates and guidelines, consult:

• references/tech-plan-template.md — Full plan document template with examples, subtask granularity guidelines, and quality checklist