Private save-snapshot API prototype

This is a locally tested, provider-independent server foundation. The game apps are not connected to cloud login, upload or restore yet. This module never reads the Mac/iPhone's game folders and never installs or restores files. Do not present it as a working cloud-save feature in the player interface.

Current save model

iOS uses Documents/save; games mounting separate account and device saves also use Documents/save_device (main.m, hle_fs.c). Mac uses its per-title Application Support save root; a separate device save is its _device sibling.
The engine writes into .work directories and commits via APFS clones and an atomic swap. Failed writes preserve the previous committed tree. Upload the committed snapshot, not .work, .new, temporary files or the game assets.
Some case-sensitive guest names use .dm-case-* physical aliases with the org.d2rmobile.guest-name xattr. A generic ZIP export that drops those xattrs can change the save's logical filenames. The portable manifest carries this metadata explicitly for files and directories.
Account and device save roots are independent transactions. A safe client snapshots/restores both before Play, while the game is stopped. Import must create a local recovery backup, validate the entire package, stage all trees, use a durable restore journal with rollback/recovery, and refuse Play while a restore is pending. Those native snapshot/import operations are still to build.
Saves may depend on game version, region, DLC, account or game-specific IDs. Record the exact Title ID, main build ID and version. Do not promise universal interchange with another release or an emulator without a tested conversion.

What the prototype implements

The server stores immutable versions in SQLite, scoped to the verified user's identity plus game and named save slot. Writes need an exact prior revision (If-Match) or a new-slot condition (If-None-Match: *). Concurrent writes from an iPad and iPhone cannot silently overwrite one another: the stale writer gets 412 and must keep its local branch until the user chooses. Retries after an unknown upload outcome first read the cloud head and compare, rather than force upload. History is retained; quota errors do not delete old versions.

Sharing pins one immutable revision. A signed-in recipient uses an expiring, revocable token to copy that revision into their own slot. It does not grant write access to the sender's slot; revoking a link does not erase copies already taken. The prototype provides private endpoints, not a public gallery of save files.

Identity is delegated to a configured provider. The server checks asymmetric RS256/ES256 JWT signatures, issuer, audience, expiry and required claims through PyJWT/JWKS. It keeps no passwords, email addresses or signing private keys. Issuer and JWKS must use HTTPS on the same trusted host. There is no bypass login or hard-coded development token in the executable. Tests inject identities only into test instances and generate their signing keys in memory.

For a simple native login, email OTP through a managed provider is a practical first option; Supabase is one compatible example when its asymmetric signing keys and correct session issuer/audience are configured. Its passwordless auth docs cover the code flow. Native login, secure token storage/refresh and logout remain client work. Sign in with Apple/CloudKit would also need the corresponding Apple capabilities and provisioning; do not assume they work under arbitrary sideloaded bundle IDs (Apple's CloudKit sample requirements). No provider account or external service was created by this implementation.

Run locally after configuring identity

Use Python 3.10+ on the server. Keep its environment, database and backups outside the source checkout. The server runs independently of Xcode and the game builder.

python3 -m venv /your/private/tools/save-api-venv
/your/private/tools/save-api-venv/bin/pip install -r dm/cloud/requirements.txt
export OIDC_ISSUER="https://your-identity-provider/issuer"
export OIDC_AUDIENCE="your-save-api-audience"
export OIDC_JWKS_URL="https://your-identity-provider/issuer/jwks"
/your/private/tools/save-api-venv/bin/python scripts/run_save_api.py --data /your/private/save-api-data

It binds to 127.0.0.1:8787. /health is unauthenticated; every /v1 route needs Authorization: Bearer <provider session token>. The sample domains above are placeholders, not real credentials. Use a real configured provider before running. No real saves or tokens are included in this repo.

The local WSGI runner is for development, not a public deployment. Before exposing it, choose hosting, a production WSGI server/TLS proxy, request rate/time/size limits, disk quotas, encrypted storage, scheduled database backups and tested recovery. The snapshots are not end-to-end encrypted; the server administrator can read them. Leave native cloud buttons disabled until the identity and restore flows are actually configured and device-tested.

Endpoints

Method	Path	Purpose
GET	`/health`	Local availability
GET	`/v1/me`	Opaque authenticated account ID
GET	`/v1/games/{title}/saves`	Current named save slots
GET	`/v1/games/{title}/saves/{slot}/revisions`	Latest 100 retained revisions
GET	`/v1/games/{title}/saves/{slot}/snapshot?revision=...`	Private current or historical package
PUT	`/v1/games/{title}/saves/{slot}/snapshot`	Conditional upload; ETag is the resulting revision
POST	`/v1/shares`	Share `{title_id, slot, revision, expires_in_seconds}`
POST	`/v1/shares/{token}/copy`	Copy to the recipient's `{title_id, slot}`, with a write precondition
DELETE	`/v1/shares/{share_id}`	Revoke your link

Slots use 1–40 lowercase letters, digits and hyphens. Title IDs are 16 uppercase hex digits. Snapshot payloads use application/vnd.nxnative.save+zip; JSON bodies are at most 16 KiB. Share lifetime is one minute to seven days. Archive size and expanded contents are capped at 64 MiB, 4,096 entries; retained payload quota is 512 MiB per user. Those are prototype limits, not compatibility guarantees for larger saves. There is no automatic pruning or unconditional overwrite endpoint.

Portable nxsave v1 package

A ZIP contains manifest.json plus precisely its listed account/device entries. Paths are relative, unique, bounded and free of traversal, symlinks or special files; case/Unicode-colliding physical paths are rejected. File bytes are checked against sizes, ZIP CRCs and SHA-256. Every uploaded snapshot must match its API Title ID. Game packages, console keys and IPA/signing credentials are refused.

{
  "schema": 1,
  "title_id": "010093801237C000",
  "game_version": "2.1.0",
  "build_id": "64 hex digits from the exact game's main NSO build ID",
  "entries": [
    {"kind": "file", "path": "account/progress.bin", "size": 12, "sha256": "64 hex digits of the file"},
    {"kind": "directory", "path": "device/system"},
    {"kind": "file", "path": "account/.dm-case-1", "size": 5, "sha256": "64 hex digits", "guest_name": "CaseSensitiveName"}
  ]
}

This illustrates the format; hashes/build ID must be real values in an actual package. guest_name represents only the engine's known case-alias xattr, never arbitrary extended attributes. Control presets remain local per-game preferences; they are separate from game progress and are not uploaded by this prototype.

Validation

Run python -m unittest scripts.tests.test_save_api using the prepared server venv. Fixtures test real loopback HTTP, user isolation, conditional/concurrent updates, immutable sharing, revocation/expiry, archive rejection and actual RSA JWT signature/issuer/audience/expiry checks. No account, real save or game file is used. This does not validate a deployed service or a native iPad-to-iPhone restore.

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