Slice Resume

/slice-resume — Continue a Paused Slice

You are resuming a vertical slice previously started via /slice. The slice directory contains PROGRESS.md (checkpoint state) and INTAKE.md (Phase 1 decisions). Trust those files.

Sub-agent pattern. Resume uses the same sub-agent delegation as /slice: all slice doc writes go through spawned Agent calls; main thread only orchestrates. See .claude/skills/slice/SKILL.md § Execution Model + § Sub-Agent Prompt Template.

Checkpoint-aware. After each completed phase, emit a Context Checkpoint block so the user can /clear again if needed. The slice survives any number of /clear → /slice-resume cycles because PROGRESS.md is durable.

Absolute Rule — Atomic Cycle Commit

/slice-resume never commits. It only writes slice docs (01-10, PROGRESS.md, INTAKE.md). The full /slice → /slice-resume → /slice-build cycle commits atomically only at the end, gated on user approval. See .claude/skills/slice/SKILL.md for the full rule.

Efficiency Principle

Do what's necessary. Skip what's not. Never compromise quality.

• Don't re-read files that haven't changed since the last read. PROGRESS.md + INTAKE.md are authoritative for slice state — trust them unless there's concrete reason to doubt.
• Don't re-run validators, sub-agents, or phases whose output is still current. If the slice docs are unchanged since the last validator run, the verdict is unchanged.
• Don't regenerate already-written slice docs to fit a default shape. If a doc is correct and current, skip it. Resume the next open step, not the last one.
• Don't re-ask Phase 1 questions. INTAKE.md captured the answers; trust it. Only re-ask if the user explicitly says a decision changed.
• Don't add scope the task didn't ask for. No defensive re-validation, no "while we're here" cleanups.
• Fast is a feature. Unnecessary re-work burns context, tokens, and the user's time.

When a skill's default flow would re-do work already verified, override it with the surgical path and document the deviation in PROGRESS.md. Quality gates stay in place — the deviation is about scope, not standards.

Step 1 — Select the slice

# Targeted resume
test -f docs/slices/<SLICE_ID>/PROGRESS.md

# Auto-discover in-progress slices
grep -lE "^status: in-progress$" docs/slices/*/PROGRESS.md 2>/dev/null

• Zero in-progress → tell user nothing to resume, suggest /slice <one-liner>. Stop.
• Exactly one → use it, announce SLICE_ID.
• Multiple → AskUserQuestion with one question listing <slice_id> + current_step + last_updated per option.
• User gave SLICE_ID but it's completed / missing → report state and stop. Do not overwrite.

Step 2 — Load state (main thread reads minimum viable)

Read ONLY these on main thread:

1. docs/slices/<SLICE_ID>/PROGRESS.md — full file. Extract: current_phase, current_step, next_action, validator_loops, validator_verdict, session_count, Files Written list, Stop Reason, slice_stage: override (if present).
2. docs/slices/<SLICE_ID>/INTAKE.md — full file. All locked decisions live here.
3. .claude/skills/slice/SKILL.md — the phase definitions + sub-agent prompt template you'll be dispatching.
4. CLAUDE.md top section — resolve PROJECT_STAGE: (overridden by slice_stage: in PROGRESS.md if present). Emit the stage banner from /slice Step 0.25 before continuing. The resumed session must calibrate to the same stage the original /slice session used — if the project stage has advanced since the slice was last worked, flag to the user and ask whether to continue at the old stage or re-calibrate the slice docs.

Do NOT read on main thread: slice templates, reference examples, already-written slice docs, SLICE-BUILDER-PROMPT.md. The sub-agents will re-read anything they need. Keeping those off main thread is the whole reason this workflow can be cleared and resumed many times.

Step 3 — Advance the session counter

Edit PROGRESS.md:

• session_count += 1
• last_updated = current ISO timestamp
• Append to Session History: - <ISO> session <n>: resumed at <current_step>

Step 4 — Resume execution via sub-agents

Jump to the phase / sub-step named by current_step. Dispatch work per /slice SKILL.md's rules for that phase:

Use the exact Sub-Agent Prompt Template from .claude/skills/slice/SKILL.md. Never write slice docs from the main thread.

Resume rules

• Never re-ask Phase 1 questions. INTAKE.md has the answers.
• Never regenerate a file in Files Written unless PROGRESS.md Stop Reason explicitly flags it (e.g., validator FAIL on that doc). In that case, spawn a fix-up agent scoped to the blockers.
• Respect locked decisions. If INTAKE.md says assignee_user_id column, do not propose an alternative in any dispatched agent's prompt.
• Rewrite PROGRESS.md at every phase boundary (sub-agents also update it as their final step — verify after they return).
• Emit Context Checkpoint after each completed phase so the user can /clear safely.

Step 5 — Validator-stuck resumes (special case)

If current_step == 5.2-validator AND validator_verdict == FAIL AND validator_loops >= 3:

• Do not loop again blindly.
• Read PROGRESS.md Stop Reason for stubborn blockers.
• Offer three paths via AskUserQuestion:
  1. Targeted fix — main thread spawns a scoped fix-up agent per blocker (describe the known-hard ones and let the user pick which to try).
  2. Relax a validator rule — rare; document why in 00-SLICE-INDEX.md § Risks.
  3. Abandon — mark PROGRESS.md status: abandoned with reason; user can rerun /slice with narrower scope later.

Step 6 — Completion

On Phase 5 PASS:

1. Main thread sets PROGRESS.md status: completed, completed_at, validator_verdict: PASS (or WARN).
2. Emit the SLICE <ID> — COMPLETE summary from /slice Step 3, including Sessions used: <session_count>.

What this skill deliberately does NOT do

• Does not re-do Phase 1. If INTAKE.md is missing, report: "Slice is too early-stage to resume — rerun /slice <one-liner>."
• Does not invent new decisions. All ambiguity resolution lives in INTAKE.md.
• Does not change SLICE_ID. Keyed on the existing ID.
• Does not skip ahead. If current_phase: 2 and 03-UI-SPEC.md somehow exists from a partial prior run, still complete 02-JOURNEY.md first before touching Phase 3.
• Does not write slice docs on main thread. All writes go through sub-agents.

Reference

• Main skill: .claude/skills/slice/SKILL.md
• Execution model: /slice § Execution Model
• Sub-agent template: /slice § Sub-Agent Prompt Template
• Checkpoint format: /slice § Context Checkpoint Protocol
• Progress schema: /slice § Progress Tracking Protocol
• Slice contract: docs/slice-templates/SLICE-BUILDER-PROMPT.md
• Reference filled example: docs/slices/00-example-bookmark-v1/