New Export Version

Cut a new game export format version. This creates a standalone schema, migration module, and updates all references.

Background

Each export version has its own schema file (schemas/game-export-vN.schema.json). Migrations live in schemas/migrations/ as modules with up(data) and down(data) functions. The shared runner at scripts/migrate_exports.py handles file I/O, chaining, and CLI.

Key files:

• schemas/game-export-v*.schema.json — per-version JSON Schemas
• schemas/migrations/ — migration modules and registry (__init__.py)
• scripts/migrate_exports.py — unified migration runner
• scripts/export_game.py — export producer (sets version, computes new fields)
• puppeteer/tests/test_migrate_exports.py — roundtrip and runner tests
• puppeteer/tests/test_export_schema.py — schema validation tests

Step 1: Determine what's changing

Ask the user what fields are being added, removed, or modified. Determine:

• The current version number N (check the "version" line in scripts/export_game.py)
• What new fields to add and their JSON Schema types
• Whether the up() migration needs external data or is purely derived from existing fields
• Whether the down() migration is lossless (can we reconstruct N from N+1?)

Before deciding on a version bump for a semantics-only fix, check whether the latest typed loaders (load_game_export, load_built_game_export) are used directly against committed exports in tests or scripts. If they only accept the newest version, a code-only version bump can break local consumers until the repo's game exports are migrated too. In that case, consider whether an in-place backfill on the existing version is the safer path.

Step 2: Create the new schema file

Copy schemas/game-export-vN.schema.json to schemas/game-export-v{N+1}.schema.json:

• Change "const": N to "const": N+1 in the version property
• Update $id, title, description to reference v{N+1}
• Add new fields to properties
• Add new $defs if needed

Step 3: Create the migration module

Create schemas/migrations/vN_to_v{N+1}.py:

"""Migration: vN -> v{N+1} (description of what changes)."""

SOURCE_VERSION = N
TARGET_VERSION = N + 1

def up(data: dict) -> dict:
    """Migrate from vN to v{N+1}."""
    assert data["version"] == N, f"Expected vN, got v{data['version']}"
    # Add new fields here
    data["version"] = N + 1
    return data

def down(data: dict) -> dict:
    """Migrate from v{N+1} to vN."""
    assert data["version"] == N + 1, f"Expected v{N+1}, got v{data['version']}"
    # Remove new fields here
    data["version"] = N
    return data

The migration must satisfy: down(up(game)) == game for all exported games.

Step 4: Register the migration

Add the new module to schemas/migrations/__init__.py:

from schemas.migrations import ..., vN_to_v{N+1}

MIGRATIONS = [
    ...,
    vN_to_v{N+1},
]

Step 5: Update scripts/export_game.py

1. Change "version": N to "version": N+1 in build_export()
2. Add computation for new fields in build_export()
3. Update _validate_export(): change version == N to version == N+1
4. Update the comment referencing the schema filename

Step 6: Update schema references

These files reference the schema filename and need updating:

• Makefile (regen-schema-types and verify-schema-types targets) → game-export-v{N+1}.schema.json
• .claude/hooks/enforce-agents-rules.py — no change needed (uses glob pattern)
• doc/export-schema.md — update prose reference if it mentions a specific version

Step 7: Regenerate TypeScript types

make regen-schema-types

Verify the generated types look correct in website/src/types/game-export.d.ts.

Step 8: Add tests

In puppeteer/tests/test_export_schema.py, add:

• test_v{N+1}_schema_is_valid — validates the new schema structure
• test_v{N+1}_schema_accepts_v{N+1} — minimal valid export passes
• test_v{N+1}_schema_rejects_vN — old version is rejected

In puppeteer/tests/test_migrate_exports.py, add a new test class:

• test_vN_to_v{N+1}_up_adds_fields — verify up() adds the right fields
• test_v{N+1}_to_vN_down_removes_fields — verify down() strips them
• test_round_trip_preserves_vN_structure — down(up(game)) == game

Step 9: Run checks

make check

All lint, typecheck, and tests must pass before proceeding.

Step 10: Create the PR (code only — no data migration)

Do NOT migrate existing games in this PR. Game migrations touch hundreds of JSON files and GitHub cannot render large diffs. Instead:

1. Create the PR with only the code changes (schema, migration module, export_game.py, tests, docs, TypeScript types).
2. In the PR description, note that a follow-up data-only PR will migrate existing games.

Step 11: Update documentation

• schemas/migrations/README.md — update the "Current state" section

Step 12: Follow-up PR — migrate existing games

After the code PR merges, create a second data-only PR:

# Preview first
uv run python scripts/migrate_exports.py --to {N+1} --dry-run

# Then migrate for real
uv run python scripts/migrate_exports.py --to {N+1}

# Verify checks still pass with migrated data
make check

Commit and PR the migrated game files separately. This keeps the code review clean and avoids GitHub choking on large diffs.