caspar-create-plan

name	caspar-create_plan
description	Turn a PRD/scope into a technical implementation plan (`plan.md`) — codebase research, clarifications, then a verification-spine plan ready for task breakdown. Use when planning HOW to build an already-scoped feature, or when `plan` routes here with a depth tier. Do NOT trigger to define WHAT/why (that's `scope`), to break a plan into tasks (`create_tasks`), or for design/UX flows (`ux`).
user-invocable	true

create_plan

Transform a scoped PRD into a technical implementation plan. Role: senior staff engineer biasing to YAGNI · SOLID · KISS · DRY — clear on the plan, no gold-plating.

Inputs

• $ARGUMENTS — feature/PRD reference + optional flags: --depth {light|standard|comprehensive} (default standard), --no-review (orchestrated by plan).
• TASK_DIR/task_context.md — reuse an existing ## Technical Research section if comprehensive; skip new research. Under --depth light, also reuse substantive router research (file locations, code understanding, patterns, impact) if already present.

Working Set

• OUT_DIR = docs/tasks/{branch} (or a user-given target_dir); read branch via tool at runtime, never inline it.
• Research agents: @finder (where code lives), @analyst (how it works + data access), @patterns (canonical "follow this file" anchors). Run in parallel, await all, then read the real code at each step — don't trust filenames or summaries.
• CLAUDE.md / README.md for rules + major components.

Outputs + DONE

Write the plan to {OUT_DIR}/specs/plan.md (scoped name if one exists). The plan is DONE when it carries the verification spine and every required section is present (header + *N/A — reason* if genuinely inapplicable; empty or absent headers are not acceptable).

Required at every depth (the spine):

1. Overview — problem, solution shape, why this approach.
2. Technical Approach — components touched, data flow, key decisions + rationale; cite @patterns anchors by file:line.
3. Critical Files — 1–7 real files from Step-1 research, each tagged Core logic to modify / Pattern to follow / Interface to implement / Test to extend. No guesses.
4. External Dependencies — Verify Before Implementation — every third-party package with exact version + one-line existence check (pkg@1.2.3 — verify: npm view pkg@1.2.3). State "no new packages" explicitly if so. (Slopsquatting fence: ~20% of AI-suggested packages don't exist.)
5. Verification — How We Know This Works — per major change, 1–3 falsifiable signals (<change> → verifies by: <test | observable | state/file condition>). These become acceptance criteria downstream. "It works" is not acceptable.
6. Out-of-Bounds — DO NOT add — 4–8 concrete things to NOT add (rate limiting, retry/backoff, caching, soft-delete, telemetry, feature flags, admin UI…). Specific to this feature. YAGNI fence against familiar-shape bias.
7. Risks & Filled Assumptions — Risks: what could break + one-line mitigation or "accept and monitor". Filled Assumptions: defaults taken because the spec was silent (reviewer-visible by design).

--depth comprehensive adds: 8. Current State (today's path, file:line) · 9. Implementation Phases (each with its own "succeeds when…", sequenced by dependency — migrations before consumers) · 10. Component/Data Architecture (schema deltas) · 11. API Design (signatures, request/response, error contracts — if any API surface changes) · 12. Migration Plan (up/down sketch, backfill, rollback — if any data-layer change) · 13. Testing Strategy (unit/integration/e2e coverage, where tests live, what's deferred).

--depth light: concise, not shallow — keep all seven spine sections, ~1 short paragraph or 3–5 bullets each. One clear path following existing patterns; no alternatives enumeration. No standalone clarification/review gates, no plan_review, no expanded architecture.

Method / guardrails

• Research first (unless reused): @finder/@analyst/@patterns in parallel → trace entry points and data flow end-to-end → cross-reference CLAUDE.md/README.md → validate discoveries against real code. If research was newly done, update task_context.md ## Technical Research.
• Clarifications: generate up to 10 technical questions, only for ambiguity not answered by the PRD or discoverable in code; present approach choices with Pros/Cons/Trade-offs. Prefer AskUserQuestion (batches ≤4, most critical first); fall back to intelligent defaults if unavailable. Return clarification findings in-thread — do not write clarification files.
• --depth light: do NOT stop for clarifications — use conservative, codebase-consistent defaults and record them under Filled Assumptions.
• Use judgment on section length, not on inclusion.

Handoff

• --no-review (orchestrated by plan): save the plan, return control to plan — do NOT wait for user review, do NOT render the Next-Steps footer. Message: "Draft implementation plan saved to {path}. Returning to plan."
• Standalone: "Implementation plan saved to {path}. Review and reply with feedback or 'Approved' to proceed." Wait for user. On completion, render the inline Next-Steps line (suggest /caspar:create_tasks).

Escalate-If

• --depth light and the plan needs >3 critical files, a new abstraction, data migration, public-API change, or an unresolved scope / security-privacy / data-correctness / public-API-behavior decision → STOP, return a tier-reassessment recommendation to plan instead of guessing.