---

name: c3-migrate description: Use when upgrading .c3/ documentation to current skill version - reads VERSION, applies transforms from migrations/ directory in batches

C3 Migration Skill

Overview

Migrate project .c3/ documentation from older versions to current skill version.

Core principle: Explicit migration triggered by user. Show plan, get confirmation, execute in batches.

Announce at start: "I'm using the c3-migrate skill to upgrade your C3 documentation."

Quick Reference

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Phase 1: Detect Version

Read Project Version

Copy# Check frontmatter first (v3), then VERSION file (v1/v2)
if grep -q '^c3-version:' .c3/README.md 2>/dev/null; then
    PROJECT_VERSION=$(grep '^c3-version:' .c3/README.md | sed 's/c3-version: *//')
elif [ -f ".c3/VERSION" ]; then
    PROJECT_VERSION=$(cat .c3/VERSION)
else
    PROJECT_VERSION=0
fi

Version storage:

Compare Versions

Version ordering:

• Numeric versions (1, 2, 3) sort before date-based versions
• Date-based versions sort lexicographically: 20251124-foo < 20251125-bar
• Example: 1 < 2 < 3 < 20251124-adr-date-naming < 20251125-next-change

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Phase 2: Build Migration Plan

1. List files in migrations/ directory from plugin directory
2. Sort lexicographically (numeric versions first, then YYYYMMDD-slug)
3. For each migration newer than PROJECT:
   • Extract transforms section
   • Parse patterns and file globs
4. Scan .c3/ for affected files
5. Build plan summary

Plan Format

Copy## Migration Plan: v{FROM} → v{TO}

### Version {N} transforms:
- {PATTERN_DESC}: {FILE_COUNT} files

### Batches:
- Batch 1: file1.md, file2.md
- Batch 2: file3.md, file4.md

---

Phase 3: Confirm with User

"I'll migrate your .c3/ documentation from v{FROM} to v{TO}.

Changes:

• {CHANGE_1}
• {CHANGE_2}

Files affected: {N}

Proceed? [y/n]"

If declined, stop.

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Phase 4: Execute Migration

Batch Processing

Process 3-5 files per batch for trackability.

For each batch:

1. Apply transforms to files
2. Report progress: Batch 1/3 complete: 3 files updated

Error Handling

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Phase 5: Finalize

Update Version

Copy# For numeric versions (1, 2, 3)
if [[ "$TARGET_VERSION" =~ ^[0-9]+$ ]]; then
    if [ "$TARGET_VERSION" -ge 3 ]; then
        sed -i "s/^c3-version: .*/c3-version: $TARGET_VERSION/" .c3/README.md
        rm -f .c3/VERSION
    else
        echo "$TARGET_VERSION" > .c3/VERSION
    fi
else
    # For date-based versions (YYYYMMDD-slug)
    sed -i "s/^c3-version: .*/c3-version: $TARGET_VERSION/" .c3/README.md
    rm -f .c3/VERSION
fi

Suggest TOC Rebuild

"Migration complete: v{FROM} → v{TO}

Rebuild the TOC using the plugin's build-toc.sh script to refresh the table of contents."

ADR Status Check (Post-Migration)

After migration, verify ADR status field consistency:

Copy# Check all ADRs have status field
for f in .c3/adr/adr-*.md; do
  grep -q '^status:' "$f" || echo "Missing status: $f"
done

# List ADRs by status
grep -l '^status: proposed' .c3/adr/*.md 2>/dev/null
grep -l '^status: accepted' .c3/adr/*.md 2>/dev/null
grep -l '^status: implemented' .c3/adr/*.md 2>/dev/null

Reminder: Only status: implemented ADRs should appear in TOC. After migration, rebuild TOC to ensure filtering is correct.

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V1 → V2 Migration

Transforms

1. Flatten components: Move from components/{container}/ to components/
2. Rename context: CTX-system-overview.md → README.md
3. Update links: Remove container subfolder from paths

Verification

Copy# No nested component directories
[ $(find .c3/components -mindepth 1 -type d | wc -l) -eq 0 ]

# README.md has correct id
grep -q '^id: context$' .c3/README.md

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V2 → V3 Migration

Transforms

1. Convert containers to folders: containers/C3-1-*.md → c3-1-*/README.md
2. Move components into containers: components/C3-101-*.md → c3-1-*/c3-101-*.md
3. Update context: id: context → id: c3-0, add c3-version: 3
4. Lowercase ADRs: ADR-001-*.md → adr-001-*.md

Verification

Copy# No containers/ or components/ directories
[ ! -d ".c3/containers" ] && [ ! -d ".c3/components" ]

# Context has c3-0 and c3-version
grep -q '^id: c3-0$' .c3/README.md
grep -q '^c3-version: 3$' .c3/README.md

# All lowercase
! find .c3 -name "C3-*" -o -name "ADR-*" | grep -q .

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20251125-layer-settings Migration

Changes

• Layer sections support structured configuration with useDefaults, include, exclude, litmus, diagrams
• Existing prose-only format still works (backward compatible)
• Skills read defaults from defaults.md files

Transforms

No automatic transforms required.

This migration is backward compatible:

• Existing context: | prose format continues to work
• Skills fall back to defaults.md when settings not customized

Optional Upgrade

Users who want layer customization can manually convert:

From:

Copycontext: |
  prose guidance here

To:

Copycontext:
  useDefaults: true
  guidance: |
    prose guidance here
  include: |
    custom items

Verification

Copy# VERSION shows 20251125-layer-settings or later
grep 'c3-version:' .c3/README.md

# settings.yaml still valid (basic check)
if [ -f ".c3/settings.yaml" ]; then
  grep -q '^context:' .c3/settings.yaml || grep -q '^context$' .c3/settings.yaml
fi

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Red Flags

Related

• v3-structure.md
• migrations/ - Individual migration files