planforge-step3-execute-slice

name	planforge-step3-execute-slice
description	Pipeline Step 3 — Execute a hardened plan slice-by-slice with validation gates, re-anchoring, and rollback protocol.
metadata	{"author":"plan-forge","source":".github/prompts/step3-execute-slice.prompt.md"}

---

description: "Pipeline Step 3 — Execute a hardened plan slice-by-slice with validation gates, re-anchoring, and rollback protocol."

Step 3: Execute Slices

Pipeline: Step 3 of 5 (Session 2 — Execution)
When: After plan is hardened (Step 2), in a new agent session
Model suggestion: Any model / Codex / Copilot Auto (10% token savings) — execution is mechanical; Codex is fast and focused
Next Step: step4-completeness-sweep.prompt.md

Replace <YOUR-HARDENED-PLAN> with your hardened plan filename.

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Read these files first:

1. docs/plans/AI-Plan-Hardening-Runbook.md (Execution Agent Prompt + Sections 10-11)
2. docs/plans/.md
3. .github/copilot-instructions.md

Now act as an EXECUTION AGENT (see the Execution Agent Prompt in the runbook).

<investigate_before_coding> Before writing code that depends on an existing file, read that file first. Never assume a method signature, type name, or import path — verify it by opening the file. If the plan references a file you haven't loaded, load it before coding against it. </investigate_before_coding>

<implementation_discipline> Only make changes specified in the current slice. Do not add features, refactor existing code, add abstractions, or create helpers beyond what the slice requires. Do not add error handling for scenarios that cannot occur within this slice's scope. Do not add docstrings, comments, or type annotations to code you did not change. The right amount of complexity is the minimum needed for the current slice. </implementation_discipline>

Execute the hardened plan one slice at a time, starting with Slice 1.

Before starting Slice 1, run a Pre-Execution Traceability Check:

• Scan the spec's MUST acceptance criteria
• Verify each MUST criterion maps to at least one slice's validation gate
• If any MUST criterion has no corresponding validation gate, flag it and ask before proceeding

Before each slice, load its Context Files (including .github/instructions/*.instructions.md guardrails). When scaffolding new entities/services/tests, use the matching prompt template from .github/prompts/. Follow the validation loop exactly. Commit after each passed slice. If any gate fails or any ambiguity arises, pause and ask for clarification.

Re-anchor after each slice using the lightweight check (4 yes/no questions). Do a full re-anchor every 3rd slice or when a lightweight check flags a concern.

For [parallel-safe] slices:

• Note which Parallel Group they belong to
• After all slices in a group complete, run the Parallel Merge Checkpoint
• If any parallel slice fails, pause all slices in that group and report

After ALL slices pass, run the COMPLETENESS SWEEP (Section 6.1).

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If a Gate Fails

Follow the Rollback Protocol (Runbook Section 10):

Strategy	When to Use
git stash	Quick save — preserves work for review
git checkout -- .	Discard changes for single slice
Branch-per-slice	Safest — recommended for high-risk phases

If the Agent Hits Context Limits

1. Commit completed work
2. Open new session with this same prompt
3. Run the Session Resume Checklist before continuing:

SESSION RESUME CHECKLIST:
1. Run `git status` — confirm working tree is clean (all prior slices committed)
2. Run `git log --oneline -5` — verify last committed slice number
3. Read the hardened plan's Scope Contract and Stop Conditions
4. Confirm the plan file has not been amended since last session
   (check for ## Amendments section — if new amendments exist, read them first)
5. Identify the next unexecuted slice and load its Context Files
6. State: "Resuming from Slice N. Prior slices 1–(N-1) are committed."

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MCP Tools (if Plan Forge MCP server is running)

• After each slice: call forge_sweep to scan for TODO/FIXME markers before moving to the next slice
• Before committing: call forge_diff with the plan file to verify all changes are within scope
• If build/test fails: call forge_smith to check if the environment is healthy

These tools are available as MCP function calls if .vscode/mcp.json or .claude/mcp.json is configured. Otherwise, use the equivalent CLI commands (pforge sweep, pforge diff, pforge smith).

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Persistent Memory (if OpenBrain is configured)

• Before each slice: search_thoughts("<slice topic>", project: "TimeTracker", created_by: "copilot-vscode", type: "decision") — load prior decisions, patterns, and implementation lessons relevant to the current slice
• After each slice: capture_thought("Slice N: <key decision or outcome>", project: "TimeTracker", created_by: "copilot-vscode", source: "plan-forge-step-3-slice-N", type: "decision") — persist decisions made during execution
• After completeness sweep: capture_thoughts([...lessons], project: "TimeTracker", created_by: "copilot-vscode", source: "plan-forge-step-4-sweep", type: "convention") — batch capture patterns, conventions, and lessons discovered