Lesson 246: Ren'Py Playtest Save Language Isolation Receipt on BUILD_RECEIPT (2026)

Direct answer: Before July playtest scale on a Ren'Py SKU with fest_public still live, file renpy_playtest_save_language_receipt_v1.json proving config.save_directory and language persistent keys are unique per SAVE_SURFACE, pass the installed-build isolation matrix (playtest slot 2 round-trip, fest slot 2 empty, no language pref bleed), and link cousin po_hash_language_receipt_v1 from Lesson 225—then promote BUILD_RECEIPT renpy_playtest_save_language_ok. Distinct from po_hash_language (PO packaging) and Lesson 238 Godot save isolation (user:// paths).

Why this matters now (July 2027 Ren'Py dual-branch playtest)

July 2027 visual-novel teams pass Lesson 225 PO-hash on the fest depot, then invite playtest_july while itch and Steam fest builds stay public. Playtesters finish in 日本語, launch the fest exe, and see English menus—or chapter 7 in fest slot 2—because persistent.language and config.save_directory were never isolated per surface.

The Ren'Py save/language isolation preflight is the ninety-second checklist—246 is the BUILD_RECEIPT milestone. Pair Lesson 245 wasm crash row and Lesson 239 tag save_isolation.

Beginner path (dual-exe matrix)

Time: ~62 minutes first dual-export wiring; ~15 minutes when surface config is pinned.

Developer path (gates S1–S6)

Cousin receipt crosswalk

Do not merge PO hash proof into this JSON—reference paths only.

renpy_playtest_save_language_receipt_v1.json

{
  "schema": "renpy_playtest_save_language_receipt_v1",
  "build_label": "playtest-july-2027-rc1",
  "surfaces": {
    "playtest_invite": {
      "save_directory": "MyVN-playtest-1",
      "language_persistent_key": "playtest_language",
      "boot_language": "japanese"
    },
    "fest_public": {
      "save_directory": "MyVN-fest-1",
      "language_persistent_key": "fest_language",
      "boot_language": "english"
    }
  },
  "isolation_matrix": {
    "playtest_slot2_roundtrip": "pass",
    "fest_slot2_cross_contamination": "none",
    "fest_language_pref_bleed": "none"
  },
  "cousin_receipts": {
    "po_hash_language": "release-evidence/localization/PO_HASH_LANGUAGE_RECEIPT.json",
    "godot_save_isolation": "release-evidence/saves/PLAYTEST_SAVE_ISOLATION_RECEIPT.json"
  },
  "gates": {
    "S1_save_directory": "pass",
    "S2_language_persistent": "pass",
    "S3_playtest_roundtrip": "pass",
    "S4_fest_isolation": "pass",
    "S5_build_label": "pass",
    "S6_receipt": "pass"
  },
  "save_language_isolation_ok": true,
  "promotion_allowed": true
}

Pin under release-evidence/saves/RENPY_PLAYTEST_SAVE_LANGUAGE_RECEIPT.json.

BUILD_RECEIPT row (S6)

Thursday row review — Ren'Py isolation line: S4 matrix pass Y/N.

Key takeaways

1. 225 PO hash ≠ 246 save/language isolation—run both before July scale.
2. config.save_directory must differ per SAVE_SURFACE (S1).
3. persistent.playtest_language vs fest_language—never one shared persistent.language (S2).
4. Prove on two installed exes—not Ren'Py launcher alone (S3–S4).
5. Godot Lesson 238 shares policy, different engine wiring.
6. Tag triage via Lesson 239—save_isolation, not new emoji.
7. Q4 capstone 253 will wire 245–252 including this row.
8. “Weblate 100% but English” → PO-hash guide—not this lesson.
9. “Fest demo Japanese after playtest” → this lesson S4 language bleed.
10. SAVE_SURFACE injection belongs in CI per Steam depot job.

Common mistakes

• GREEN 225 but shared save_directory between exes.
• S2 skipped—menus flip language without player input.
• Merging schemas into po_hash_language_receipt_v1.
• Testing only itch WebGL when receipt targets desktop VN exes—file surface honestly.
• Conflating with Lesson 212 labels-only cousin.

Troubleshooting

Mini exercise (60 minutes)

1. Ship one build with shared save_directory—reproduce fest bleed.
2. Add save_surface_config.rpy + S2 keys—pass matrix on two installs.
3. Link cousin PO_HASH_LANGUAGE_RECEIPT.json.
4. File receipt; BUILD_RECEIPT GREEN.
5. Pin facilitator note beside playtest isolation blog.

Continuity — Q4 2027 July playtest scale (245–253)

Previous: Lesson 245 — Bevy playtest crash build_label
Next: Lesson 247 — Unreal playtest menu minidump build_label

FAQ

Same as Lesson 225?
225 = PO hash packaging; 246 = save roots + language persistent per surface.

Same as save isolation guide?
Guide = S1–S6 checklist; 246 = BUILD_RECEIPT promotion.

Same as Lesson 238?
238 = Godot user://; 246 = Ren'Py save_directory + persistent.

English-only VN?
Set renpy_playtest_save_language_ok: n/a when only one surface ships—do not fake matrix.

Localized playtest must not rewrite fest saves or menus—isolate directories and language keys, prove the matrix on installed exes, then renpy_playtest_save_language_ok on BUILD_RECEIPT.