Plan slice {{sliceId}} ("{{sliceTitle}}") of milestone {{milestoneId}}. Read `.sf/DECISIONS.md` if it exists — respect existing decisions. Read `.sf/REQUIREMENTS.md` if it exists — identify which Active requirements the roadmap says this slice owns or supports, and ensure the plan delivers them. Read the roadmap boundary map, any existing context/research files, and dependency summaries. Use the **Slice Plan** and **Task Plan** output templates below. Decompose into tasks with must-haves. Fill the `Proof Level` and `Integration Closure` sections truthfully so the plan says what class of proof this slice really delivers and what end-to-end wiring still remains. Call `sf_plan_slice` to persist the slice plan — the tool writes `{{sliceId}}-PLAN.md` and individual `T##-PLAN.md` files to disk and persists to DB. Do **not** write plan files manually — use the DB-backed tool so state stays consistent. If planning produces structural decisions, call `sf_decision_save` for each — the tool auto-assigns IDs and regenerates `.sf/DECISIONS.md` automatically. {{skillActivation}} Before finishing, self-audit the plan: every must-have maps to at least one task, every task has complete sections (steps, must-haves, verification, observability impact, inputs, and expected output), task ordering is consistent with no circular references, every pair of artifacts that must connect has an explicit wiring step, task scope targets 2–5 steps and 3–8 files (6–8 steps or 8–10 files — consider splitting; 10+ steps or 12+ files — must split), the plan honors locked decisions from context/research/decisions artifacts, the proof-level wording does not overclaim live integration if only fixture/contract proof is planned, every Active requirement this slice owns has at least one task with verification that proves it is met, and every task produces real user-facing progress — if the slice has a UI surface at least one task builds the real UI, if it has an API at least one task connects it to a real data source, and showing the completed result to a non-technical stakeholder would demonstrate real product progress rather than developer artifacts, and quality gate coverage — for non-trivial slices, Threat Surface (Q3: abuse, data exposure, input trust) and Requirement Impact (Q4: requirements touched, re-verify, decisions revisited) sections are present. For non-trivial tasks, Failure Modes (Q5), Load Profile (Q6), and Negative Tests (Q7) are filled in task plans.

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