Template generation should use project history context

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Problem

When generating new milestones for an existing project, the AI template generator has no context about what was already built. This can lead to:

• Suggesting features that already exist (e.g., "Add user authentication" when auth was built in v1.0)
• Missing that certain systems/modules are already in place
• Not building on top of existing architecture decisions

Expected Behavior

In extend mode, /mgw:project should provide the template generator with:

1. Completed milestones summary — names, phase titles, issue titles from previous milestones
2. Current codebase state — key modules/systems that exist (from CLAUDE.md or codebase scan)
3. GSD history — if .planning/milestones/ contains archived roadmaps, include a digest

This context goes into the AI prompt so generated milestones build on what exists rather than starting from scratch.

Implementation

Before the generate_template step, assemble history context:

# Previous milestones from project.json
HISTORY=$(python3 -c "
import json
p = json.load(open('${MGW_DIR}/project.json'))
for m in p['milestones']:
    print(f\"Milestone: {m['name']}\")
    for i in m['issues']:
        print(f\"  - {i['title']} ({i['pipeline_stage']})\")
")

# GSD artifacts if available
GSD_DIGEST=$(node ~/.claude/get-shit-done/bin/gsd-tools.cjs history-digest 2>/dev/null || echo "")

Include in the generation prompt as <project_history> context.

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MGW . triage-complete . 2026-03-01T04:07:11.953Z

Triage Complete

Scope	small -- 2 files across mgw:project, gsd-tools (history-digest)
Validity	confirmed
Security	low
Route	gsd:quick -- Single-file logic change in extend-mode section. Pattern already implemented in mgw:issue.md.
Gates	All passed

Ready for pipeline execution.

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MGW · work-starting · 2026-03-01T04:07:11.953Z

Work Starting

Route	gsd:quick — Single-file logic change in extend-mode section. Pattern already implemented in mgw:issue.md.
Scope	small — 2 files across mgw:project, gsd-tools (history-digest)
Conflicts	None

Work begins on branch issue/58-template-generation-should-use-project-h.

Affected Files

• commands/project.md
• .claude/commands/mgw/project.md

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MGW · execution-complete · 2026-03-01T04:07:11.953Z

Execution Complete

2 atomic commit(s) on branch issue/58-template-generation-should-use-project-h.

Changes: commands/project.md and .claude/commands/mgw/project.md — history context injection + extend-mode sync

Tests: n/a (bash/markdown command file)

Preparing pull request.

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MGW · pr-ready · 2026-03-01T04:07:11.953Z

PR Ready

PR #70 — #70

Assembles HISTORY_CONTEXT from project.json + gsd-tools history-digest and injects it into extend-mode template generation to prevent re-suggesting already-built features.

Testing procedures posted on the PR.
This issue will auto-close when the PR is merged.

Pipeline Summary

Stage	Status
Triage	✓
Planning	✓
Execution	✓
PR Creation	✓