feat: Add user registration endpoints in API v2. (#10430)

* feat: Add user registration endpoints in API v2. Desktop Model-credits initiative.

* [autofix.ci] apply automated fixes

* fix: adjust registration API endpoints to REST compliance.

* [autofix.ci] apply automated fixes

* feat: Implement registration API queries for fetching and posting registrations

* feat: Enhance registration API with secure file handling and add hooks for fetching registration

* refactor: Lazy file creation.

* Commit: Delete unused file use-get-registratrions.ts

* feat: Add unit and integration tests for registration API

* refactor: Simplify registration response model by removing success and message fields

* [autofix.ci] apply automated fixes

* [autofix.ci] apply automated fixes (attempt 2/3)

* refactor: Remove success and message assertions from registration tests

---------

Co-authored-by: autofix-ci[bot] <114827586+autofix-ci[bot]@users.noreply.github.com>

Author: ricofurtado

.gitignore

@@ -285,3 +285,6 @@ CLAUDE.md
 member_servers.json
 # Component index cache (user-specific)
 **/.cache/lfx/
+
+# data files used for desktop registration
+data/user

src/backend/base/langflow/api/router.py

@@ -24,6 +24,7 @@
 from langflow.api.v1.voice_mode import router as voice_mode_router
 from langflow.api.v2 import files_router as files_router_v2
 from langflow.api.v2 import mcp_router as mcp_router_v2
+from langflow.api.v2 import registration_router as registration_router_v2
 
 router_v1 = APIRouter(
     prefix="/v1",
@@ -55,6 +56,7 @@
 
 router_v2.include_router(files_router_v2)
 router_v2.include_router(mcp_router_v2)
+router_v2.include_router(registration_router_v2)
 
 router = APIRouter(
     prefix="/api",

src/backend/base/langflow/api/v2/__init__.py

@@ -1,7 +1,9 @@
 from langflow.api.v2.files import router as files_router
 from langflow.api.v2.mcp import router as mcp_router
+from langflow.api.v2.registration import router as registration_router
 
 __all__ = [
     "files_router",
     "mcp_router",
+    "registration_router",
 ]

src/backend/base/langflow/api/v2/registration.py

@@ -0,0 +1,123 @@
+import json
+from asyncio import to_thread
+from datetime import datetime, timezone
+from pathlib import Path
+
+from fastapi import APIRouter, HTTPException
+from pydantic import BaseModel, EmailStr
+
+from langflow.logging import logger
+
+router = APIRouter(tags=["Registration API"], prefix="/registration")
+
+
+# Data model for registration
+class RegisterRequest(BaseModel):
+    email: EmailStr
+
+
+class RegisterResponse(BaseModel):
+    email: str
+
+
+# File to store registrations
+REGISTRATION_FILE = Path("data/user/registration.json")
+
+
+def _ensure_registration_file():
+    """Ensure registration file and directory exist with proper permissions."""
+    try:
+        # Ensure the directory exists with secure permissions
+        REGISTRATION_FILE.parent.mkdir(parents=True, exist_ok=True)
+        # Set directory permissions to owner read/write/execute only (if possible)
+        REGISTRATION_FILE.parent.chmod(0o700)
+    except Exception as e:
+        logger.error(f"Failed to create registration file/directory: {e}")
+        raise
+
+
+# TODO: Move functions to a separate service module
+
+
+def load_registration() -> dict | None:
+    """Load the single registration from file."""
+    if not REGISTRATION_FILE.exists() or REGISTRATION_FILE.stat().st_size == 0:
+        return None
+    try:
+        with REGISTRATION_FILE.open("rb") as f:  # using binary mode for faster file IO
+            content = f.read()
+        return json.loads(content)
+    except (json.JSONDecodeError, UnicodeDecodeError):
+        logger.error(f"Corrupted registration file: {REGISTRATION_FILE}")
+        return None
+
+
+def save_registration(email: str) -> bool:
+    """Save the single registration to file.
+
+    Args:
+        email: Email to register
+
+    Returns:
+        True if saved successfully
+    """
+    try:
+        # Ensure the registration file and directory exist
+        _ensure_registration_file()
+
+        # Check if registration already exists
+        existing = load_registration()
+
+        # Create new registration (replaces any existing)
+        registration = {
+            "email": email,
+            "registered_at": datetime.now(tz=timezone.utc).isoformat(),
+        }
+
+        # Log if replacing
+        if existing:
+            logger.info(f"Replacing registration: {existing.get('email')} -> {email}")
+
+        # Save to file
+        with REGISTRATION_FILE.open("w") as f:
+            json.dump(registration, f, indent=2)
+
+        logger.info(f"Registration saved: {email}")
+
+    except Exception as e:
+        logger.error(f"Error saving registration: {e}")
+        raise
+    else:
+        return True
+
+
+@router.post("/", response_model=RegisterResponse)
+async def register_user(request: RegisterRequest):
+    """Register the single user with email.
+
+    Note: Only one registration is allowed.
+    """
+    try:
+        email = request.email
+        # Save to local file (replace existing) not dealing with 201 status for simplicity.
+        if await to_thread(save_registration, email):
+            return RegisterResponse(email=email)
+
+    except HTTPException:
+        raise
+    except Exception as e:
+        raise HTTPException(status_code=500, detail=f"Registration failed: {e!s}") from e
+
+
+@router.get("/")
+async def get_registration():
+    """Get the registered user (if any)."""
+    try:
+        registration = await to_thread(load_registration)
+        if registration:
+            return registration
+
+        return {"message": "No user registered"}  # noqa: TRY300
+
+    except Exception as e:
+        raise HTTPException(status_code=500, detail=f"Failed to load registration: {e!s}") from e