diff --git a/auth.py b/auth.py
new file mode 100644
index 0000000..b729347
--- /dev/null
+++ b/auth.py
@@ -0,0 +1,310 @@
+"""
+Centralized Authorization Module for Castle Extension.
+
+Provides consistent, secure authorization patterns across all endpoints.
+
+Key concepts:
+- AuthContext: Captures all authorization state for a request
+- Dependencies: FastAPI dependencies for endpoint protection
+- Permission checks: Consistent resource-level access control
+
+Usage:
+    from .auth import require_super_user, require_authenticated, AuthContext
+
+    @router.get("/api/v1/admin-endpoint")
+    async def admin_endpoint(auth: AuthContext = Depends(require_super_user)):
+        # Only super users can access
+        pass
+
+    @router.get("/api/v1/user-data")
+    async def user_data(auth: AuthContext = Depends(require_authenticated)):
+        # Any authenticated user
+        user_id = auth.user_id
+        pass
+"""
+
+from dataclasses import dataclass
+from functools import wraps
+from http import HTTPStatus
+from typing import Optional
+
+from fastapi import Depends, HTTPException
+from lnbits.core.models import WalletTypeInfo
+from lnbits.decorators import require_admin_key, require_invoice_key
+from lnbits.settings import settings as lnbits_settings
+from loguru import logger
+
+from .crud import get_account, get_user_permissions
+from .models import PermissionType
+
+
+@dataclass
+class AuthContext:
+    """
+    Authorization context for a request.
+
+    Contains all information needed to make authorization decisions.
+    Use this instead of directly accessing wallet/user properties scattered
+    throughout endpoint code.
+    """
+    user_id: str
+    wallet_id: str
+    is_super_user: bool
+    wallet: WalletTypeInfo
+
+    @property
+    def is_admin(self) -> bool:
+        """
+        Check if user is a Castle admin (super user).
+
+        Note: In Castle, admin = super_user. There's no separate admin concept.
+        """
+        return self.is_super_user
+
+    def require_super_user(self) -> None:
+        """Raise HTTPException if not super user."""
+        if not self.is_super_user:
+            raise HTTPException(
+                status_code=HTTPStatus.FORBIDDEN,
+                detail="Super user access required"
+            )
+
+    def require_self_or_super_user(self, target_user_id: str) -> None:
+        """
+        Require that user is accessing their own data or is super user.
+
+        Args:
+            target_user_id: The user ID being accessed
+
+        Raises:
+            HTTPException: If user is neither the target nor super user
+        """
+        if not self.is_super_user and self.user_id != target_user_id:
+            raise HTTPException(
+                status_code=HTTPStatus.FORBIDDEN,
+                detail="Access denied: you can only access your own data"
+            )
+
+
+def _build_auth_context(wallet: WalletTypeInfo) -> AuthContext:
+    """Build AuthContext from wallet info."""
+    user_id = wallet.wallet.user
+    return AuthContext(
+        user_id=user_id,
+        wallet_id=wallet.wallet.id,
+        is_super_user=user_id == lnbits_settings.super_user,
+        wallet=wallet,
+    )
+
+
+# ===== FastAPI Dependencies =====
+
+async def require_authenticated(
+    wallet: WalletTypeInfo = Depends(require_invoice_key),
+) -> AuthContext:
+    """
+    Require authentication (invoice key minimum).
+
+    Returns AuthContext with user information.
+    Use for read-only access to user's own data.
+    """
+    return _build_auth_context(wallet)
+
+
+async def require_authenticated_write(
+    wallet: WalletTypeInfo = Depends(require_admin_key),
+) -> AuthContext:
+    """
+    Require authentication with write permissions (admin key).
+
+    Returns AuthContext with user information.
+    Use for write operations on user's own data.
+    """
+    return _build_auth_context(wallet)
+
+
+async def require_super_user(
+    wallet: WalletTypeInfo = Depends(require_admin_key),
+) -> AuthContext:
+    """
+    Require super user access.
+
+    Raises HTTPException 403 if not super user.
+    Use for Castle admin operations.
+    """
+    auth = _build_auth_context(wallet)
+    if not auth.is_super_user:
+        logger.warning(
+            f"Super user access denied for user {auth.user_id[:8]} "
+            f"attempting admin operation"
+        )
+        raise HTTPException(
+            status_code=HTTPStatus.FORBIDDEN,
+            detail="Super user access required"
+        )
+    return auth
+
+
+# ===== Resource Access Checks =====
+
+async def can_access_account(
+    auth: AuthContext,
+    account_id: str,
+    permission_type: PermissionType = PermissionType.READ,
+) -> bool:
+    """
+    Check if user can access an account.
+
+    Access is granted if:
+    1. User is super user (full access)
+    2. User owns the account (user-specific accounts like Assets:Receivable:User-abc123)
+    3. User has explicit permission for the account
+
+    Args:
+        auth: The authorization context
+        account_id: The account ID to check
+        permission_type: The type of access needed (READ, SUBMIT_EXPENSE, MANAGE)
+
+    Returns:
+        True if access is allowed, False otherwise
+    """
+    # Super users have full access
+    if auth.is_super_user:
+        return True
+
+    # Check if this is the user's own account
+    account = await get_account(account_id)
+    if account:
+        user_short = auth.user_id[:8]
+        if f"User-{user_short}" in account.name:
+            return True
+
+    # Check explicit permissions
+    permissions = await get_user_permissions(auth.user_id)
+    for perm in permissions:
+        if perm.account_id == account_id:
+            # Check if permission type is sufficient
+            if perm.permission_type == PermissionType.MANAGE:
+                return True  # MANAGE grants all access
+            if perm.permission_type == permission_type:
+                return True
+            if (
+                permission_type == PermissionType.READ
+                and perm.permission_type in [PermissionType.SUBMIT_EXPENSE, PermissionType.MANAGE]
+            ):
+                return True  # Higher permissions include READ
+
+    return False
+
+
+async def require_account_access(
+    auth: AuthContext,
+    account_id: str,
+    permission_type: PermissionType = PermissionType.READ,
+) -> None:
+    """
+    Require access to an account, raising HTTPException if denied.
+
+    Args:
+        auth: The authorization context
+        account_id: The account ID to check
+        permission_type: The type of access needed
+
+    Raises:
+        HTTPException: If access is denied
+    """
+    if not await can_access_account(auth, account_id, permission_type):
+        logger.warning(
+            f"Account access denied: user {auth.user_id[:8]} "
+            f"attempted {permission_type.value} on account {account_id}"
+        )
+        raise HTTPException(
+            status_code=HTTPStatus.FORBIDDEN,
+            detail=f"Access denied to account {account_id}"
+        )
+
+
+async def can_access_user_data(auth: AuthContext, target_user_id: str) -> bool:
+    """
+    Check if user can access another user's data.
+
+    Access is granted if:
+    1. User is super user
+    2. User is accessing their own data
+
+    Args:
+        auth: The authorization context
+        target_user_id: The user ID whose data is being accessed
+
+    Returns:
+        True if access is allowed
+    """
+    if auth.is_super_user:
+        return True
+
+    # Users can access their own data - compare full ID or short ID
+    if auth.user_id == target_user_id:
+        return True
+
+    # Also allow if short IDs match (8 char prefix)
+    if auth.user_id[:8] == target_user_id[:8]:
+        return True
+
+    return False
+
+
+async def require_user_data_access(
+    auth: AuthContext,
+    target_user_id: str,
+) -> None:
+    """
+    Require access to a user's data, raising HTTPException if denied.
+
+    Args:
+        auth: The authorization context
+        target_user_id: The user ID whose data is being accessed
+
+    Raises:
+        HTTPException: If access is denied
+    """
+    if not await can_access_user_data(auth, target_user_id):
+        logger.warning(
+            f"User data access denied: user {auth.user_id[:8]} "
+            f"attempted to access data for user {target_user_id[:8]}"
+        )
+        raise HTTPException(
+            status_code=HTTPStatus.FORBIDDEN,
+            detail="Access denied: you can only access your own data"
+        )
+
+
+# ===== Utility Functions =====
+
+def get_user_id_from_wallet(wallet: WalletTypeInfo) -> str:
+    """
+    Get user ID from wallet info.
+
+    IMPORTANT: Always use wallet.wallet.user (not wallet.wallet.id).
+    - wallet.wallet.user = the user's ID
+    - wallet.wallet.id = the wallet's ID (NOT the same!)
+
+    Args:
+        wallet: The wallet type info from LNbits
+
+    Returns:
+        The user ID
+    """
+    return wallet.wallet.user
+
+
+def is_super_user(user_id: str) -> bool:
+    """
+    Check if a user ID is the super user.
+
+    Args:
+        user_id: The user ID to check
+
+    Returns:
+        True if this is the super user
+    """
+    return user_id == lnbits_settings.super_user
diff --git a/fava_client.py b/fava_client.py
index 38e932a..6880d11 100644
--- a/fava_client.py
+++ b/fava_client.py
@@ -17,6 +17,7 @@ Fava provides a REST API for:
 See: https://github.com/beancount/fava/blob/main/src/fava/json_api.py
 """
 
+import asyncio
 import httpx
 from typing import Any, Dict, List, Optional
 from decimal import Decimal
@@ -24,6 +25,11 @@ from datetime import date, datetime
 from loguru import logger
 
 
+class ChecksumConflictError(Exception):
+    """Raised when a Fava write operation fails due to stale checksum (concurrent modification)."""
+    pass
+
+
 class FavaClient:
     """
     Async client for Fava REST API.
@@ -48,6 +54,37 @@ class FavaClient:
         self.base_url = f"{self.fava_url}/{self.ledger_slug}/api"
         self.timeout = timeout
 
+        # Concurrency control: Global write lock to serialize all ledger modifications.
+        # This prevents race conditions when multiple requests try to write to the
+        # Beancount ledger file simultaneously. Without this lock, concurrent writes
+        # can cause data loss, duplicate entries, or file corruption.
+        #
+        # Note: This serializes ALL writes which may become a bottleneck at scale.
+        # For higher throughput, consider per-user locking or distributed locking.
+        self._write_lock = asyncio.Lock()
+
+        # Per-user locks for user-specific operations (reduces contention)
+        self._user_locks: Dict[str, asyncio.Lock] = {}
+
+    def get_user_lock(self, user_id: str) -> asyncio.Lock:
+        """
+        Get or create a lock for a specific user.
+
+        This enables per-user locking to reduce contention when multiple users
+        are making concurrent requests. User-specific operations should acquire
+        this lock in addition to (or instead of) the global write lock.
+
+        Args:
+            user_id: User ID (uses first 8 characters for consistency)
+
+        Returns:
+            asyncio.Lock for this user
+        """
+        user_key = user_id[:8]
+        if user_key not in self._user_locks:
+            self._user_locks[user_key] = asyncio.Lock()
+        return self._user_locks[user_key]
+
     async def add_entry(self, entry: Dict[str, Any]) -> Dict[str, Any]:
         """
         Submit a new journal entry to Fava.
@@ -88,26 +125,100 @@ class FavaClient:
                 "meta": {"user_id": "abc123"}
             }
             result = await fava_client.add_entry(entry)
+
+        Note:
+            This method acquires a global write lock to prevent concurrent
+            modifications to the ledger file. All writes are serialized.
         """
+        # Acquire global write lock to serialize ledger modifications
+        async with self._write_lock:
+            try:
+                async with httpx.AsyncClient(timeout=self.timeout) as client:
+                    response = await client.put(
+                        f"{self.base_url}/add_entries",
+                        json={"entries": [entry]},
+                        headers={"Content-Type": "application/json"}
+                    )
+                    response.raise_for_status()
+                    result = response.json()
+
+                    logger.info(f"Added entry to Fava: {result.get('data', 'Unknown')}")
+                    return result
+
+            except httpx.HTTPStatusError as e:
+                logger.error(f"Fava HTTP error: {e.response.status_code} - {e.response.text}")
+                raise
+            except httpx.RequestError as e:
+                logger.error(f"Fava connection error: {e}")
+                raise
+
+    async def add_entry_idempotent(
+        self,
+        entry: Dict[str, Any],
+        idempotency_key: str
+    ) -> Dict[str, Any]:
+        """
+        Submit a journal entry with idempotency protection.
+
+        This method checks if an entry with the given idempotency key (as a Beancount link)
+        already exists before inserting. This prevents duplicate entries when the same
+        operation is retried (e.g., due to network issues or concurrent requests).
+
+        The idempotency key is stored as a Beancount link on the entry. Links are part
+        of the entry's identity and are indexed by Beancount, making lookup efficient.
+
+        Args:
+            entry: Beancount entry dict (same format as add_entry)
+            idempotency_key: Unique key for this operation (e.g., "castle-{uuid}" or "ln-{payment_hash}")
+
+        Returns:
+            Response from Fava if entry was created, or existing entry data if already exists
+
+        Example:
+            # Use payment hash as idempotency key for Lightning payments
+            result = await fava.add_entry_idempotent(
+                entry=settlement_entry,
+                idempotency_key=f"ln-{payment_hash[:16]}"
+            )
+
+            # Use expense ID for expense entries
+            result = await fava.add_entry_idempotent(
+                entry=expense_entry,
+                idempotency_key=f"exp-{expense_id}"
+            )
+        """
+        from .beancount_format import sanitize_link
+
+        # Sanitize the idempotency key to ensure it's a valid Beancount link
+        safe_key = sanitize_link(idempotency_key)
+
+        # Check if entry with this link already exists
         try:
-            async with httpx.AsyncClient(timeout=self.timeout) as client:
-                response = await client.put(
-                    f"{self.base_url}/add_entries",
-                    json={"entries": [entry]},
-                    headers={"Content-Type": "application/json"}
-                )
-                response.raise_for_status()
-                result = response.json()
+            entries = await self.get_journal_entries(days=30)  # Check recent entries
 
-                logger.info(f"Added entry to Fava: {result.get('data', 'Unknown')}")
-                return result
+            for existing_entry in entries:
+                existing_links = existing_entry.get("links", [])
+                if safe_key in existing_links:
+                    logger.info(f"Entry with idempotency key '{safe_key}' already exists, skipping insert")
+                    return {
+                        "data": "Entry already exists (idempotent)",
+                        "existing": True,
+                        "entry": existing_entry
+                    }
+        except Exception as e:
+            logger.warning(f"Could not check for existing entry with key '{safe_key}': {e}")
+            # Continue anyway - Beancount will error if there's a true duplicate
 
-        except httpx.HTTPStatusError as e:
-            logger.error(f"Fava HTTP error: {e.response.status_code} - {e.response.text}")
-            raise
-        except httpx.RequestError as e:
-            logger.error(f"Fava connection error: {e}")
-            raise
+        # Add the idempotency key as a link if not already present
+        if "links" not in entry:
+            entry["links"] = []
+        if safe_key not in entry["links"]:
+            entry["links"].append(safe_key)
+
+        # Now add the entry (this will acquire the write lock)
+        result = await self.add_entry(entry)
+        result["existing"] = False
+        return result
 
     async def get_account_balance(self, account_name: str) -> Dict[str, Any]:
         """
@@ -1146,6 +1257,10 @@ class FavaClient:
         Returns:
             New sha256sum after update
 
+        Note:
+            This method acquires a global write lock to prevent concurrent
+            modifications to the ledger file. All writes are serialized.
+
         Example:
             # Get context
             context = await fava.get_entry_context("abc123")
@@ -1158,26 +1273,28 @@ class FavaClient:
             # Update
             new_sha256 = await fava.update_entry_source("abc123", new_source, sha256)
         """
-        try:
-            async with httpx.AsyncClient(timeout=self.timeout) as client:
-                response = await client.put(
-                    f"{self.base_url}/source_slice",
-                    json={
-                        "entry_hash": entry_hash,
-                        "source": new_source,
-                        "sha256sum": sha256sum
-                    }
-                )
-                response.raise_for_status()
-                result = response.json()
-                return result.get("data", "")
+        # Acquire global write lock to serialize ledger modifications
+        async with self._write_lock:
+            try:
+                async with httpx.AsyncClient(timeout=self.timeout) as client:
+                    response = await client.put(
+                        f"{self.base_url}/source_slice",
+                        json={
+                            "entry_hash": entry_hash,
+                            "source": new_source,
+                            "sha256sum": sha256sum
+                        }
+                    )
+                    response.raise_for_status()
+                    result = response.json()
+                    return result.get("data", "")
 
-        except httpx.HTTPStatusError as e:
-            logger.error(f"Fava update error: {e.response.status_code} - {e.response.text}")
-            raise
-        except httpx.RequestError as e:
-            logger.error(f"Fava connection error: {e}")
-            raise
+            except httpx.HTTPStatusError as e:
+                logger.error(f"Fava update error: {e.response.status_code} - {e.response.text}")
+                raise
+            except httpx.RequestError as e:
+                logger.error(f"Fava connection error: {e}")
+                raise
 
     async def delete_entry(self, entry_hash: str, sha256sum: str) -> str:
         """
@@ -1190,36 +1307,43 @@ class FavaClient:
         Returns:
             Success message
 
+        Note:
+            This method acquires a global write lock to prevent concurrent
+            modifications to the ledger file. All writes are serialized.
+
         Example:
             context = await fava.get_entry_context("abc123")
             await fava.delete_entry("abc123", context["sha256sum"])
         """
-        try:
-            async with httpx.AsyncClient(timeout=self.timeout) as client:
-                response = await client.delete(
-                    f"{self.base_url}/source_slice",
-                    params={
-                        "entry_hash": entry_hash,
-                        "sha256sum": sha256sum
-                    }
-                )
-                response.raise_for_status()
-                result = response.json()
-                return result.get("data", "")
+        # Acquire global write lock to serialize ledger modifications
+        async with self._write_lock:
+            try:
+                async with httpx.AsyncClient(timeout=self.timeout) as client:
+                    response = await client.delete(
+                        f"{self.base_url}/source_slice",
+                        params={
+                            "entry_hash": entry_hash,
+                            "sha256sum": sha256sum
+                        }
+                    )
+                    response.raise_for_status()
+                    result = response.json()
+                    return result.get("data", "")
 
-        except httpx.HTTPStatusError as e:
-            logger.error(f"Fava delete error: {e.response.status_code} - {e.response.text}")
-            raise
-        except httpx.RequestError as e:
-            logger.error(f"Fava connection error: {e}")
-            raise
+            except httpx.HTTPStatusError as e:
+                logger.error(f"Fava delete error: {e.response.status_code} - {e.response.text}")
+                raise
+            except httpx.RequestError as e:
+                logger.error(f"Fava connection error: {e}")
+                raise
 
     async def add_account(
         self,
         account_name: str,
         currencies: list[str],
         opening_date: Optional[date] = None,
-        metadata: Optional[Dict[str, Any]] = None
+        metadata: Optional[Dict[str, Any]] = None,
+        max_retries: int = 3
     ) -> Dict[str, Any]:
         """
         Add an account to the Beancount ledger via an Open directive.
@@ -1227,15 +1351,25 @@ class FavaClient:
         NOTE: Fava's /api/add_entries endpoint does NOT support Open directives.
         This method uses /api/source to directly edit the Beancount file.
 
+        This method implements optimistic concurrency control with retry logic:
+        - Acquires a global write lock before modifying the ledger
+        - Uses SHA256 checksum to detect concurrent modifications
+        - Retries with exponential backoff on checksum conflicts
+        - Re-checks if account was created by concurrent request before retrying
+
         Args:
             account_name: Full account name (e.g., "Assets:Receivable:User-abc123")
             currencies: List of currencies for this account (e.g., ["EUR", "SATS"])
             opening_date: Date to open the account (defaults to today)
             metadata: Optional metadata for the account
+            max_retries: Maximum number of retry attempts on checksum conflict (default: 3)
 
         Returns:
             Response from Fava ({"data": "new_sha256sum", "mtime": "..."})
 
+        Raises:
+            ChecksumConflictError: If all retry attempts fail due to concurrent modifications
+
         Example:
             # Add a user's receivable account
             result = await fava.add_account(
@@ -1255,89 +1389,115 @@ class FavaClient:
         if opening_date is None:
             opening_date = date_type.today()
 
-        try:
-            async with httpx.AsyncClient(timeout=self.timeout) as client:
-                # Step 1: Get the main Beancount file path from Fava
-                options_response = await client.get(f"{self.base_url}/options")
-                options_response.raise_for_status()
-                options_data = options_response.json()["data"]
-                file_path = options_data["beancount_options"]["filename"]
+        last_error = None
 
-                logger.debug(f"Fava main file: {file_path}")
+        for attempt in range(max_retries):
+            # Acquire global write lock to serialize ledger modifications
+            async with self._write_lock:
+                try:
+                    async with httpx.AsyncClient(timeout=self.timeout) as client:
+                        # Step 1: Get the main Beancount file path from Fava
+                        options_response = await client.get(f"{self.base_url}/options")
+                        options_response.raise_for_status()
+                        options_data = options_response.json()["data"]
+                        file_path = options_data["beancount_options"]["filename"]
 
-                # Step 2: Get current source file
-                response = await client.get(
-                    f"{self.base_url}/source",
-                    params={"filename": file_path}
-                )
-                response.raise_for_status()
-                source_data = response.json()["data"]
+                        logger.debug(f"Fava main file: {file_path}")
 
-                sha256sum = source_data["sha256sum"]
-                source = source_data["source"]
+                        # Step 2: Get current source file (fresh read on each attempt)
+                        response = await client.get(
+                            f"{self.base_url}/source",
+                            params={"filename": file_path}
+                        )
+                        response.raise_for_status()
+                        source_data = response.json()["data"]
 
-                # Step 2: Check if account already exists
-                if f"open {account_name}" in source:
-                    logger.info(f"Account {account_name} already exists in Beancount file")
-                    return {"data": sha256sum, "mtime": source_data.get("mtime", "")}
+                        sha256sum = source_data["sha256sum"]
+                        source = source_data["source"]
 
-                # Step 3: Find insertion point (after last Open directive AND its metadata)
-                lines = source.split('\n')
-                insert_index = 0
-                for i, line in enumerate(lines):
-                    if line.strip().startswith(('open ', f'{opening_date.year}-')) and 'open' in line:
-                        # Found an Open directive, now skip over any metadata lines
-                        insert_index = i + 1
-                        # Skip metadata lines (lines starting with whitespace)
-                        while insert_index < len(lines) and lines[insert_index].startswith((' ', '\t')) and lines[insert_index].strip():
-                            insert_index += 1
+                        # Step 3: Check if account already exists (may have been created by concurrent request)
+                        if f"open {account_name}" in source:
+                            logger.info(f"Account {account_name} already exists in Beancount file")
+                            return {"data": sha256sum, "mtime": source_data.get("mtime", "")}
 
-                # Step 4: Format Open directive as Beancount text
-                currencies_str = ", ".join(currencies)
-                open_lines = [
-                    "",
-                    f"{opening_date.isoformat()} open {account_name} {currencies_str}"
-                ]
+                        # Step 4: Find insertion point (after last Open directive AND its metadata)
+                        lines = source.split('\n')
+                        insert_index = 0
+                        for i, line in enumerate(lines):
+                            if line.strip().startswith(('open ', f'{opening_date.year}-')) and 'open' in line:
+                                # Found an Open directive, now skip over any metadata lines
+                                insert_index = i + 1
+                                # Skip metadata lines (lines starting with whitespace)
+                                while insert_index < len(lines) and lines[insert_index].startswith((' ', '\t')) and lines[insert_index].strip():
+                                    insert_index += 1
 
-                # Add metadata if provided
-                if metadata:
-                    for key, value in metadata.items():
-                        # Format metadata with proper indentation
-                        if isinstance(value, str):
-                            open_lines.append(f'  {key}: "{value}"')
-                        else:
-                            open_lines.append(f'  {key}: {value}')
+                        # Step 5: Format Open directive as Beancount text
+                        currencies_str = ", ".join(currencies)
+                        open_lines = [
+                            "",
+                            f"{opening_date.isoformat()} open {account_name} {currencies_str}"
+                        ]
 
-                # Step 5: Insert into source
-                for i, line in enumerate(open_lines):
-                    lines.insert(insert_index + i, line)
+                        # Add metadata if provided
+                        if metadata:
+                            for key, value in metadata.items():
+                                # Format metadata with proper indentation
+                                if isinstance(value, str):
+                                    open_lines.append(f'  {key}: "{value}"')
+                                else:
+                                    open_lines.append(f'  {key}: {value}')
 
-                new_source = '\n'.join(lines)
+                        # Step 6: Insert into source
+                        for i, line in enumerate(open_lines):
+                            lines.insert(insert_index + i, line)
 
-                # Step 6: Update source file via PUT /api/source
-                update_payload = {
-                    "file_path": file_path,
-                    "source": new_source,
-                    "sha256sum": sha256sum
-                }
+                        new_source = '\n'.join(lines)
 
-                response = await client.put(
-                    f"{self.base_url}/source",
-                    json=update_payload,
-                    headers={"Content-Type": "application/json"}
-                )
-                response.raise_for_status()
-                result = response.json()
+                        # Step 7: Update source file via PUT /api/source
+                        update_payload = {
+                            "file_path": file_path,
+                            "source": new_source,
+                            "sha256sum": sha256sum
+                        }
 
-                logger.info(f"Added account {account_name} to Beancount file with currencies {currencies}")
-                return result
+                        response = await client.put(
+                            f"{self.base_url}/source",
+                            json=update_payload,
+                            headers={"Content-Type": "application/json"}
+                        )
+                        response.raise_for_status()
+                        result = response.json()
 
-        except httpx.HTTPStatusError as e:
-            logger.error(f"Fava HTTP error adding account: {e.response.status_code} - {e.response.text}")
-            raise
-        except httpx.RequestError as e:
-            logger.error(f"Fava connection error: {e}")
-            raise
+                        logger.info(f"Added account {account_name} to Beancount file with currencies {currencies}")
+                        return result
+
+                except httpx.HTTPStatusError as e:
+                    # Check for checksum conflict (HTTP 412 Precondition Failed or similar)
+                    if e.response.status_code in (409, 412):
+                        last_error = ChecksumConflictError(
+                            f"Checksum conflict on attempt {attempt + 1}/{max_retries}: {e.response.text}"
+                        )
+                        logger.warning(
+                            f"Checksum conflict adding account {account_name} "
+                            f"(attempt {attempt + 1}/{max_retries}), retrying..."
+                        )
+                        # Continue to retry logic below
+                    else:
+                        logger.error(f"Fava HTTP error adding account: {e.response.status_code} - {e.response.text}")
+                        raise
+                except httpx.RequestError as e:
+                    logger.error(f"Fava connection error: {e}")
+                    raise
+
+            # If we get here due to checksum conflict, wait with exponential backoff before retry
+            if attempt < max_retries - 1:
+                backoff_time = 0.1 * (2 ** attempt)  # 0.1s, 0.2s, 0.4s
+                logger.info(f"Waiting {backoff_time}s before retry...")
+                await asyncio.sleep(backoff_time)
+
+        # All retries exhausted
+        logger.error(f"Failed to add account {account_name} after {max_retries} attempts due to concurrent modifications")
+        raise last_error or ChecksumConflictError(f"Failed to add account after {max_retries} attempts")
 
     async def get_unsettled_entries_bql(
         self,
diff --git a/services.py b/services.py
index 1f9d826..51c4bd8 100644
--- a/services.py
+++ b/services.py
@@ -18,12 +18,29 @@ async def get_settings(user_id: str) -> CastleSettings:
 
 
 async def update_settings(user_id: str, data: CastleSettings) -> CastleSettings:
+    from loguru import logger
+
+    from .fava_client import init_fava_client
+
     settings = await get_castle_settings(user_id)
     if not settings:
         settings = await create_castle_settings(user_id, data)
     else:
         settings = await update_castle_settings(user_id, data)
 
+    # Reinitialize Fava client with new settings
+    try:
+        init_fava_client(
+            fava_url=settings.fava_url,
+            ledger_slug=settings.fava_ledger_slug,
+            timeout=settings.fava_timeout,
+        )
+        logger.info(
+            f"Fava client reinitialized: {settings.fava_url}/{settings.fava_ledger_slug}"
+        )
+    except Exception as e:
+        logger.error(f"Failed to reinitialize Fava client: {e}")
+
     return settings
 
 
diff --git a/static/js/index.js b/static/js/index.js
index 3fc736e..3c8d9b7 100644
--- a/static/js/index.js
+++ b/static/js/index.js
@@ -31,6 +31,7 @@ window.app = Vue.createApp({
       userInfo: null, // User information including equity eligibility
       isAdmin: false,
       isSuperUser: false,
+      settingsLoaded: false, // Flag to prevent race conditions on toolbar buttons
       castleWalletConfigured: false,
       userWalletConfigured: false,
       currentExchangeRate: null, // BTC/EUR rate (sats per EUR)
@@ -57,6 +58,9 @@ window.app = Vue.createApp({
       settingsDialog: {
         show: false,
         castleWalletId: '',
+        favaUrl: 'http://localhost:3333',
+        favaLedgerSlug: 'castle-ledger',
+        favaTimeout: 10.0,
         loading: false
       },
       userWalletDialog: {
@@ -517,6 +521,9 @@ window.app = Vue.createApp({
       } catch (error) {
         // Settings not available
         this.castleWalletConfigured = false
+      } finally {
+        // Mark settings as loaded to enable toolbar buttons
+        this.settingsLoaded = true
       }
     },
     async loadUserWallet() {
@@ -534,6 +541,9 @@ window.app = Vue.createApp({
     },
     showSettingsDialog() {
       this.settingsDialog.castleWalletId = this.settings?.castle_wallet_id || ''
+      this.settingsDialog.favaUrl = this.settings?.fava_url || 'http://localhost:3333'
+      this.settingsDialog.favaLedgerSlug = this.settings?.fava_ledger_slug || 'castle-ledger'
+      this.settingsDialog.favaTimeout = this.settings?.fava_timeout || 10.0
       this.settingsDialog.show = true
     },
     showUserWalletDialog() {
@@ -549,6 +559,14 @@ window.app = Vue.createApp({
         return
       }
 
+      if (!this.settingsDialog.favaUrl) {
+        this.$q.notify({
+          type: 'warning',
+          message: 'Fava URL is required'
+        })
+        return
+      }
+
       this.settingsDialog.loading = true
       try {
         await LNbits.api.request(
@@ -556,7 +574,10 @@ window.app = Vue.createApp({
           '/castle/api/v1/settings',
           this.g.user.wallets[0].adminkey,
           {
-            castle_wallet_id: this.settingsDialog.castleWalletId
+            castle_wallet_id: this.settingsDialog.castleWalletId,
+            fava_url: this.settingsDialog.favaUrl,
+            fava_ledger_slug: this.settingsDialog.favaLedgerSlug || 'castle-ledger',
+            fava_timeout: parseFloat(this.settingsDialog.favaTimeout) || 10.0
           }
         )
         this.$q.notify({
diff --git a/static/js/permissions.js b/static/js/permissions.js
index 0de3569..4cc54f0 100644
--- a/static/js/permissions.js
+++ b/static/js/permissions.js
@@ -1118,5 +1118,3 @@ window.app = Vue.createApp({
     }
   }
 })
-
-window.app.mount('#vue')
diff --git a/tasks.py b/tasks.py
index b44c883..8ec83b9 100644
--- a/tasks.py
+++ b/tasks.py
@@ -187,6 +187,12 @@ async def on_invoice_paid(payment: Payment) -> None:
     This function is called automatically when any invoice on the Castle wallet
     is paid. It checks if the invoice is a Castle payment and records it in
     Beancount via Fava.
+
+    Concurrency Protection:
+    - Uses per-user locking to prevent race conditions when multiple payments
+      for the same user are processed simultaneously
+    - Uses idempotent entry creation to prevent duplicate entries even if
+      the same payment is processed multiple times
     """
     # Only process Castle-specific payments
     if not payment.extra or payment.extra.get("tag") != "castle":
@@ -197,134 +203,120 @@ async def on_invoice_paid(payment: Payment) -> None:
         logger.warning(f"Castle invoice {payment.payment_hash} missing user_id in metadata")
         return
 
-    # Check if payment already recorded (idempotency)
-    # Query Fava for existing entry with this payment hash link
     from .fava_client import get_fava_client
-    import httpx
 
     fava = get_fava_client()
 
-    try:
-        # Check if payment already recorded by fetching recent entries
-        # Note: We can't use BQL query with `links ~ 'pattern'` because links is a set type
-        # and BQL doesn't support regex matching on sets. Instead, fetch entries and filter in Python.
-        link_to_find = f"ln-{payment.payment_hash[:16]}"
+    # Use idempotency key based on payment hash - this ensures duplicate
+    # processing of the same payment won't create duplicate entries
+    idempotency_key = f"ln-{payment.payment_hash[:16]}"
 
-        async with httpx.AsyncClient(timeout=5.0) as client:
-            # Get recent entries from Fava's journal endpoint
-            response = await client.get(
-                f"{fava.base_url}/api/journal",
-                params={"time": ""}  # Get all entries
+    # Acquire per-user lock to serialize processing for this user
+    # This prevents race conditions when a user has multiple payments being processed
+    user_lock = fava.get_user_lock(user_id)
+
+    async with user_lock:
+        logger.info(f"Recording Castle payment {payment.payment_hash} for user {user_id[:8]} to Fava")
+
+        try:
+            from decimal import Decimal
+            from .crud import get_account_by_name, get_or_create_user_account
+            from .models import AccountType
+            from .beancount_format import format_net_settlement_entry
+
+            # Convert amount from millisatoshis to satoshis
+            amount_sats = payment.amount // 1000
+
+            # Extract fiat metadata from invoice (if present)
+            fiat_currency = None
+            fiat_amount = None
+            if payment.extra:
+                fiat_currency = payment.extra.get("fiat_currency")
+                fiat_amount_str = payment.extra.get("fiat_amount")
+                if fiat_amount_str:
+                    fiat_amount = Decimal(str(fiat_amount_str))
+
+            if not fiat_currency or not fiat_amount:
+                logger.error(f"Payment {payment.payment_hash} missing fiat currency/amount metadata")
+                return
+
+            # Get user's current balance to determine receivables and payables
+            balance = await fava.get_user_balance(user_id)
+            fiat_balances = balance.get("fiat_balances", {})
+            total_fiat_balance = fiat_balances.get(fiat_currency, Decimal(0))
+
+            # Determine receivables and payables based on balance
+            # Positive balance = user owes castle (receivable)
+            # Negative balance = castle owes user (payable)
+            if total_fiat_balance > 0:
+                # User owes castle
+                total_receivable = total_fiat_balance
+                total_payable = Decimal(0)
+            else:
+                # Castle owes user
+                total_receivable = Decimal(0)
+                total_payable = abs(total_fiat_balance)
+
+            logger.info(f"Settlement: {fiat_amount} {fiat_currency} (Receivable: {total_receivable}, Payable: {total_payable})")
+
+            # Get account names
+            user_receivable = await get_or_create_user_account(
+                user_id, AccountType.ASSET, "Accounts Receivable"
+            )
+            user_payable = await get_or_create_user_account(
+                user_id, AccountType.LIABILITY, "Accounts Payable"
+            )
+            lightning_account = await get_account_by_name("Assets:Bitcoin:Lightning")
+            if not lightning_account:
+                logger.error("Lightning account 'Assets:Bitcoin:Lightning' not found")
+                return
+
+            # Query for unsettled entries to link this settlement back to them
+            # Net settlement can settle both expenses and receivables
+            settled_links = []
+            try:
+                unsettled_expenses = await fava.get_unsettled_entries_bql(user_id, "expense")
+                settled_links.extend([e["link"] for e in unsettled_expenses if e.get("link")])
+                unsettled_receivables = await fava.get_unsettled_entries_bql(user_id, "receivable")
+                settled_links.extend([e["link"] for e in unsettled_receivables if e.get("link")])
+            except Exception as e:
+                logger.warning(f"Could not query unsettled entries for settlement links: {e}")
+                # Continue without links - settlement will still be recorded
+
+            # Format as net settlement transaction
+            entry = format_net_settlement_entry(
+                user_id=user_id,
+                payment_account=lightning_account.name,
+                receivable_account=user_receivable.name,
+                payable_account=user_payable.name,
+                amount_sats=amount_sats,
+                net_fiat_amount=fiat_amount,
+                total_receivable_fiat=total_receivable,
+                total_payable_fiat=total_payable,
+                fiat_currency=fiat_currency,
+                description=f"Lightning payment settlement from user {user_id[:8]}",
+                entry_date=datetime.now().date(),
+                payment_hash=payment.payment_hash,
+                reference=payment.payment_hash,
+                settled_entry_links=settled_links if settled_links else None
             )
 
-            if response.status_code == 200:
-                data = response.json()
-                entries = data.get('entries', [])
+            # Submit to Fava using idempotent method to prevent duplicates
+            # The idempotency key is based on the payment hash, so even if this
+            # function is called multiple times for the same payment, only one
+            # entry will be created
+            result = await fava.add_entry_idempotent(entry, idempotency_key)
 
-                # Check if any entry has our payment link
-                for entry in entries:
-                    entry_links = entry.get('links', [])
-                    if link_to_find in entry_links:
-                        logger.info(f"Payment {payment.payment_hash} already recorded in Fava, skipping")
-                        return
+            if result.get("existing"):
+                logger.info(
+                    f"Payment {payment.payment_hash} was already recorded in Fava (idempotent)"
+                )
+            else:
+                logger.info(
+                    f"Successfully recorded payment {payment.payment_hash} to Fava: "
+                    f"{result.get('data', 'Unknown')}"
+                )
 
-    except Exception as e:
-        logger.warning(f"Could not check Fava for duplicate payment: {e}")
-        # Continue anyway - Fava/Beancount will catch duplicate if it exists
-
-    logger.info(f"Recording Castle payment {payment.payment_hash} for user {user_id[:8]} to Fava")
-
-    try:
-        from decimal import Decimal
-        from .crud import get_account_by_name, get_or_create_user_account
-        from .models import AccountType
-        from .beancount_format import format_net_settlement_entry
-
-        # Convert amount from millisatoshis to satoshis
-        amount_sats = payment.amount // 1000
-
-        # Extract fiat metadata from invoice (if present)
-        fiat_currency = None
-        fiat_amount = None
-        if payment.extra:
-            fiat_currency = payment.extra.get("fiat_currency")
-            fiat_amount_str = payment.extra.get("fiat_amount")
-            if fiat_amount_str:
-                fiat_amount = Decimal(str(fiat_amount_str))
-
-        if not fiat_currency or not fiat_amount:
-            logger.error(f"Payment {payment.payment_hash} missing fiat currency/amount metadata")
-            return
-
-        # Get user's current balance to determine receivables and payables
-        balance = await fava.get_user_balance(user_id)
-        fiat_balances = balance.get("fiat_balances", {})
-        total_fiat_balance = fiat_balances.get(fiat_currency, Decimal(0))
-
-        # Determine receivables and payables based on balance
-        # Positive balance = user owes castle (receivable)
-        # Negative balance = castle owes user (payable)
-        if total_fiat_balance > 0:
-            # User owes castle
-            total_receivable = total_fiat_balance
-            total_payable = Decimal(0)
-        else:
-            # Castle owes user
-            total_receivable = Decimal(0)
-            total_payable = abs(total_fiat_balance)
-
-        logger.info(f"Settlement: {fiat_amount} {fiat_currency} (Receivable: {total_receivable}, Payable: {total_payable})")
-
-        # Get account names
-        user_receivable = await get_or_create_user_account(
-            user_id, AccountType.ASSET, "Accounts Receivable"
-        )
-        user_payable = await get_or_create_user_account(
-            user_id, AccountType.LIABILITY, "Accounts Payable"
-        )
-        lightning_account = await get_account_by_name("Assets:Bitcoin:Lightning")
-        if not lightning_account:
-            logger.error("Lightning account 'Assets:Bitcoin:Lightning' not found")
-            return
-
-        # Query for unsettled entries to link this settlement back to them
-        # Net settlement can settle both expenses and receivables
-        settled_links = []
-        try:
-            unsettled_expenses = await fava.get_unsettled_entries_bql(user_id, "expense")
-            settled_links.extend([e["link"] for e in unsettled_expenses if e.get("link")])
-            unsettled_receivables = await fava.get_unsettled_entries_bql(user_id, "receivable")
-            settled_links.extend([e["link"] for e in unsettled_receivables if e.get("link")])
         except Exception as e:
-            logger.warning(f"Could not query unsettled entries for settlement links: {e}")
-            # Continue without links - settlement will still be recorded
-
-        # Format as net settlement transaction
-        entry = format_net_settlement_entry(
-            user_id=user_id,
-            payment_account=lightning_account.name,
-            receivable_account=user_receivable.name,
-            payable_account=user_payable.name,
-            amount_sats=amount_sats,
-            net_fiat_amount=fiat_amount,
-            total_receivable_fiat=total_receivable,
-            total_payable_fiat=total_payable,
-            fiat_currency=fiat_currency,
-            description=f"Lightning payment settlement from user {user_id[:8]}",
-            entry_date=datetime.now().date(),
-            payment_hash=payment.payment_hash,
-            reference=payment.payment_hash,
-            settled_entry_links=settled_links if settled_links else None
-        )
-
-        # Submit to Fava
-        result = await fava.add_entry(entry)
-
-        logger.info(
-            f"Successfully recorded payment {payment.payment_hash} to Fava: "
-            f"{result.get('data', 'Unknown')}"
-        )
-
-    except Exception as e:
-        logger.error(f"Error recording Castle payment {payment.payment_hash}: {e}")
-        raise
+            logger.error(f"Error recording Castle payment {payment.payment_hash}: {e}")
+            raise
diff --git a/templates/castle/index.html b/templates/castle/index.html
index 6648e6c..2a1e665 100644
--- a/templates/castle/index.html
+++ b/templates/castle/index.html
@@ -17,13 +17,14 @@
             <p class="q-mb-none">Track expenses, receivables, and balances for the collective</p>
           </div>
           <div class="col-auto q-gutter-xs">
-            <q-btn v-if="!isSuperUser" flat round icon="account_balance_wallet" @click="showUserWalletDialog">
+            <!-- Wait for settings to load before showing role-specific buttons to prevent race conditions -->
+            <q-btn v-if="settingsLoaded && !isSuperUser" flat round icon="account_balance_wallet" @click="showUserWalletDialog">
               <q-tooltip>Configure Your Wallet</q-tooltip>
             </q-btn>
-            <q-btn v-if="isSuperUser" flat round icon="admin_panel_settings" :href="'/castle/permissions'">
+            <q-btn v-if="settingsLoaded && isSuperUser" flat round icon="admin_panel_settings" :href="'/castle/permissions'">
               <q-tooltip>Manage Permissions (Admin)</q-tooltip>
             </q-btn>
-            <q-btn v-if="isSuperUser" flat round icon="settings" @click="showSettingsDialog">
+            <q-btn v-if="settingsLoaded && isSuperUser" flat round icon="settings" @click="showSettingsDialog">
               <q-tooltip>Castle Settings (Super User Only)</q-tooltip>
             </q-btn>
           </div>
@@ -32,7 +33,7 @@
     </q-card>
 
     <!-- Setup Warning -->
-    <q-banner v-if="!castleWalletConfigured && isSuperUser" class="bg-warning text-white" rounded>
+    <q-banner v-if="settingsLoaded && !castleWalletConfigured && isSuperUser" class="bg-warning text-white" rounded>
       <template v-slot:avatar>
         <q-icon name="warning" color="white"></q-icon>
       </template>
@@ -44,7 +45,7 @@
       </template>
     </q-banner>
 
-    <q-banner v-if="!castleWalletConfigured && !isSuperUser" class="bg-info text-white" rounded>
+    <q-banner v-if="settingsLoaded && !castleWalletConfigured && !isSuperUser" class="bg-info text-white" rounded>
       <template v-slot:avatar>
         <q-icon name="info" color="white"></q-icon>
       </template>
@@ -53,7 +54,7 @@
       </div>
     </q-banner>
 
-    <q-banner v-if="castleWalletConfigured && !userWalletConfigured && !isSuperUser" class="bg-orange text-white" rounded>
+    <q-banner v-if="settingsLoaded && castleWalletConfigured && !userWalletConfigured && !isSuperUser" class="bg-orange text-white" rounded>
       <template v-slot:avatar>
         <q-icon name="account_balance_wallet" color="white"></q-icon>
       </template>
@@ -1122,10 +1123,46 @@
         :disable="!isSuperUser"
       ></q-select>
 
-      <div class="text-caption text-grey">
+      <div class="text-caption text-grey q-mb-md">
         Select the wallet that will be used for Castle operations and transactions.
       </div>
 
+      <q-separator class="q-my-md"></q-separator>
+
+      <div class="text-subtitle2 q-mb-sm">Fava/Beancount Integration</div>
+
+      <q-input
+        filled
+        dense
+        v-model="settingsDialog.favaUrl"
+        label="Fava URL *"
+        hint="Base URL of the Fava server (e.g., http://localhost:3333)"
+        :readonly="!isSuperUser"
+        :disable="!isSuperUser"
+      ></q-input>
+
+      <q-input
+        filled
+        dense
+        v-model="settingsDialog.favaLedgerSlug"
+        label="Ledger Slug"
+        hint="Ledger identifier in Fava URL (e.g., castle-ledger)"
+        :readonly="!isSuperUser"
+        :disable="!isSuperUser"
+      ></q-input>
+
+      <q-input
+        filled
+        dense
+        type="number"
+        step="0.5"
+        v-model.number="settingsDialog.favaTimeout"
+        label="Timeout (seconds)"
+        hint="Request timeout for Fava API calls"
+        :readonly="!isSuperUser"
+        :disable="!isSuperUser"
+      ></q-input>
+
       <div class="row q-mt-lg">
         <q-btn
           v-if="isSuperUser"
diff --git a/views_api.py b/views_api.py
index a3e206d..dc4d1d1 100644
--- a/views_api.py
+++ b/views_api.py
@@ -83,6 +83,14 @@ from .models import (
     UserWithRoles,
 )
 from .services import get_settings, get_user_wallet, update_settings, update_user_wallet
+from .auth import (
+    AuthContext,
+    require_authenticated,
+    require_authenticated_write,
+    require_super_user,
+    require_account_access,
+    require_user_data_access,
+)
 
 castle_api_router = APIRouter()
 
@@ -276,26 +284,34 @@ async def api_get_accounts(
 @castle_api_router.post("/api/v1/accounts", status_code=HTTPStatus.CREATED)
 async def api_create_account(
     data: CreateAccount,
-    wallet: WalletTypeInfo = Depends(require_admin_key),
+    auth: AuthContext = Depends(require_super_user),
 ) -> Account:
-    """Create a new account (admin only)"""
+    """Create a new account (super user only)"""
     return await create_account(data)
 
 
 @castle_api_router.get("/api/v1/accounts/{account_id}")
-async def api_get_account(account_id: str) -> Account:
-    """Get a specific account"""
+async def api_get_account(
+    account_id: str,
+    auth: AuthContext = Depends(require_authenticated),
+) -> Account:
+    """Get a specific account (requires authentication and account access)"""
     account = await get_account(account_id)
     if not account:
         raise HTTPException(
             status_code=HTTPStatus.NOT_FOUND, detail="Account not found"
         )
+    # Check access permission
+    await require_account_access(auth, account_id, PermissionType.READ)
     return account
 
 
 @castle_api_router.get("/api/v1/accounts/{account_id}/balance")
-async def api_get_account_balance(account_id: str) -> dict:
-    """Get account balance from Fava/Beancount"""
+async def api_get_account_balance(
+    account_id: str,
+    auth: AuthContext = Depends(require_authenticated),
+) -> dict:
+    """Get account balance from Fava/Beancount (requires authentication and account access)"""
     from .fava_client import get_fava_client
 
     # Get account to retrieve its name
@@ -303,6 +319,9 @@ async def api_get_account_balance(account_id: str) -> dict:
     if not account:
         raise HTTPException(status_code=404, detail="Account not found")
 
+    # Check access permission
+    await require_account_access(auth, account_id, PermissionType.READ)
+
     # Query Fava for balance
     fava = get_fava_client()
     balance_data = await fava.get_account_balance(account.name)
@@ -316,11 +335,16 @@ async def api_get_account_balance(account_id: str) -> dict:
 
 
 @castle_api_router.get("/api/v1/accounts/{account_id}/transactions")
-async def api_get_account_transactions(account_id: str, limit: int = 100) -> list[dict]:
+async def api_get_account_transactions(
+    account_id: str,
+    limit: int = 100,
+    auth: AuthContext = Depends(require_authenticated),
+) -> list[dict]:
     """
     Get all transactions for an account from Fava/Beancount.
 
     Returns transactions affecting this account in reverse chronological order.
+    Requires authentication and account access.
     """
     from .fava_client import get_fava_client
 
@@ -332,6 +356,9 @@ async def api_get_account_transactions(account_id: str, limit: int = 100) -> lis
             detail=f"Account {account_id} not found"
         )
 
+    # Check access permission
+    await require_account_access(auth, account_id, PermissionType.READ)
+
     # Query Fava for transactions
     fava = get_fava_client()
     transactions = await fava.get_account_transactions(account.name, limit)
@@ -343,11 +370,15 @@ async def api_get_account_transactions(account_id: str, limit: int = 100) -> lis
 
 
 @castle_api_router.get("/api/v1/entries")
-async def api_get_journal_entries(limit: int = 100) -> list[dict]:
+async def api_get_journal_entries(
+    limit: int = 100,
+    auth: AuthContext = Depends(require_super_user),
+) -> list[dict]:
     """
     Get all journal entries from Fava/Beancount.
 
     Returns all transactions in reverse chronological order with username enrichment.
+    SUPER USER ONLY - exposes all transaction data.
     """
     from lnbits.core.crud.users import get_user
     from .fava_client import get_fava_client
@@ -721,22 +752,15 @@ async def _get_username_from_user_id(user_id: str) -> str:
 
 @castle_api_router.get("/api/v1/entries/pending")
 async def api_get_pending_entries(
-    wallet: WalletTypeInfo = Depends(require_admin_key),
+    auth: AuthContext = Depends(require_super_user),
 ) -> list[dict]:
     """
-    Get all pending expense entries that need approval (admin only).
+    Get all pending expense entries that need approval (super user only).
 
     Returns transactions with flag='!' from Fava/Beancount.
     """
-    from lnbits.settings import settings as lnbits_settings
     from .fava_client import get_fava_client
 
-    if wallet.wallet.user != lnbits_settings.super_user:
-        raise HTTPException(
-            status_code=HTTPStatus.FORBIDDEN,
-            detail="Only super user can access this endpoint",
-        )
-
     # Query Fava for all journal entries (includes links, tags, full metadata)
     fava = get_fava_client()
     all_entries = await fava.get_journal_entries()
@@ -949,7 +973,7 @@ async def api_create_journal_entry(
     # Entry metadata (excluding tags and links which go at transaction level)
     entry_meta = {k: v for k, v in data.meta.items() if k not in ["tags", "links"]}
     entry_meta["source"] = "castle-api"
-    entry_meta["created-by"] = wallet.wallet.id
+    entry_meta["created-by"] = wallet.wallet.user  # Use user_id, not wallet_id
 
     # Format as Beancount entry
     fava = get_fava_client()
@@ -975,7 +999,7 @@ async def api_create_journal_entry(
         id=f"fava-{timestamp}",
         description=data.description,
         entry_date=data.entry_date if data.entry_date else datetime.now(),
-        created_by=wallet.wallet.id,
+        created_by=wallet.wallet.user,  # Use user_id, not wallet_id
         created_at=datetime.now(),
         reference=data.reference,
         flag=data.flag if data.flag else JournalEntryFlag.CLEARED,
@@ -1138,7 +1162,7 @@ async def api_create_expense_entry(
         id=entry_id,  # Use the generated castle entry ID
         description=data.description + description_suffix,
         entry_date=data.entry_date if data.entry_date else datetime.now(),
-        created_by=wallet.wallet.id,
+        created_by=wallet.wallet.user,  # Use user_id, not wallet_id
         created_at=datetime.now(),
         reference=castle_reference,
         flag=JournalEntryFlag.PENDING,
@@ -1266,7 +1290,7 @@ async def api_create_receivable_entry(
         id=entry_id,  # Use the generated castle entry ID
         description=data.description + description_suffix,
         entry_date=datetime.now(),
-        created_by=wallet.wallet.id,
+        created_by=wallet.wallet.user,  # Use user_id, not wallet_id
         created_at=datetime.now(),
         reference=castle_reference,  # Use castle reference with unique ID
         flag=JournalEntryFlag.PENDING,
@@ -1380,7 +1404,7 @@ async def api_create_revenue_entry(
         id=entry_id,
         description=data.description,
         entry_date=datetime.now(),
-        created_by=wallet.wallet.id,
+        created_by=wallet.wallet.user,  # Use user_id, not wallet_id
         created_at=datetime.now(),
         reference=castle_reference,
         flag=JournalEntryFlag.CLEARED,
@@ -1444,8 +1468,18 @@ async def api_get_my_balance(
 
 
 @castle_api_router.get("/api/v1/balance/{user_id}")
-async def api_get_user_balance(user_id: str) -> UserBalance:
-    """Get a specific user's balance with the Castle (from Fava/Beancount)"""
+async def api_get_user_balance(
+    user_id: str,
+    auth: AuthContext = Depends(require_authenticated),
+) -> UserBalance:
+    """
+    Get a specific user's balance with the Castle (from Fava/Beancount).
+
+    Users can only access their own balance. Super users can access any user's balance.
+    """
+    # Check access: must be own data or super user
+    await require_user_data_access(auth, user_id)
+
     from .fava_client import get_fava_client
 
     fava = get_fava_client()
@@ -1461,9 +1495,9 @@ async def api_get_user_balance(user_id: str) -> UserBalance:
 
 @castle_api_router.get("/api/v1/balances/all")
 async def api_get_all_balances(
-    wallet: WalletTypeInfo = Depends(require_admin_key),
+    auth: AuthContext = Depends(require_super_user),
 ) -> list[dict]:
-    """Get all user balances (admin/super user only) from Fava/Beancount"""
+    """Get all user balances (super user only) from Fava/Beancount"""
     from .fava_client import get_fava_client
 
     fava = get_fava_client()
@@ -1802,7 +1836,7 @@ async def api_pay_user(
 @castle_api_router.post("/api/v1/receivables/settle")
 async def api_settle_receivable(
     data: SettleReceivable,
-    wallet: WalletTypeInfo = Depends(require_admin_key),
+    auth: AuthContext = Depends(require_super_user),
 ) -> dict:
     """
     Manually settle a receivable (record when user pays castle in person).
@@ -1812,15 +1846,8 @@ async def api_settle_receivable(
     - Bank transfers
     - Other manual settlements
 
-    Admin only.
+    Super user only.
     """
-    from lnbits.settings import settings as lnbits_settings
-
-    if wallet.wallet.user != lnbits_settings.super_user:
-        raise HTTPException(
-            status_code=HTTPStatus.FORBIDDEN,
-            detail="Only super user can settle receivables",
-        )
 
     # Validate payment method
     valid_methods = ["cash", "bank_transfer", "check", "lightning", "btc_onchain", "other"]
@@ -1957,7 +1984,7 @@ async def api_settle_receivable(
 @castle_api_router.post("/api/v1/payables/pay")
 async def api_pay_user(
     data: PayUser,
-    wallet: WalletTypeInfo = Depends(require_admin_key),
+    auth: AuthContext = Depends(require_super_user),
 ) -> dict:
     """
     Pay a user (castle pays user for expense/liability).
@@ -1966,15 +1993,8 @@ async def api_pay_user(
     - Lightning payments: already executed, just record the payment
     - Cash/Bank/Check: record manual payment that was made
 
-    Admin only.
+    Super user only.
     """
-    from lnbits.settings import settings as lnbits_settings
-
-    if wallet.wallet.user != lnbits_settings.super_user:
-        raise HTTPException(
-            status_code=HTTPStatus.FORBIDDEN,
-            detail="Only super user can pay users",
-        )
 
     # Validate payment method
     valid_methods = ["cash", "bank_transfer", "check", "lightning", "btc_onchain", "other"]
@@ -2152,16 +2172,9 @@ async def api_update_settings(
 @castle_api_router.get("/api/v1/user-wallet/{user_id}")
 async def api_get_user_wallet(
     user_id: str,
-    wallet: WalletTypeInfo = Depends(require_admin_key),
+    auth: AuthContext = Depends(require_super_user),
 ) -> dict:
-    """Get user's wallet settings (admin only)"""
-    from lnbits.settings import settings as lnbits_settings
-
-    if wallet.wallet.user != lnbits_settings.super_user:
-        raise HTTPException(
-            status_code=HTTPStatus.FORBIDDEN,
-            detail="Only super user can access user wallet info",
-        )
+    """Get user's wallet settings (super user only)"""
 
     user_wallet = await get_user_wallet(user_id)
     if not user_wallet:
@@ -2183,9 +2196,9 @@ async def api_get_user_wallet(
 
 @castle_api_router.get("/api/v1/users")
 async def api_get_all_users(
-    wallet: WalletTypeInfo = Depends(require_admin_key),
+    auth: AuthContext = Depends(require_super_user),
 ) -> list[dict]:
-    """Get all users who have configured their wallet (admin only)"""
+    """Get all users who have configured their wallet (super user only)"""
     from lnbits.core.crud.users import get_user
 
     user_settings = await get_all_user_wallet_settings()
@@ -2209,12 +2222,12 @@ async def api_get_all_users(
 
 @castle_api_router.get("/api/v1/admin/castle-users")
 async def api_get_castle_users(
-    wallet: WalletTypeInfo = Depends(require_admin_key),
+    auth: AuthContext = Depends(require_super_user),
 ) -> list[dict]:
     """
     Get all users who have configured their wallet in Castle.
     These are users who can interact with Castle (submit expenses, receive permissions, etc.).
-    Admin only.
+    Super user only.
     """
     from lnbits.core.crud.users import get_user
 
@@ -2247,10 +2260,10 @@ async def api_expense_report(
     start_date: Optional[str] = None,
     end_date: Optional[str] = None,
     group_by: str = "account",
-    wallet: WalletTypeInfo = Depends(require_admin_key),
+    auth: AuthContext = Depends(require_super_user),
 ) -> dict:
     """
-    Get expense summary report using BQL.
+    Get expense summary report using BQL. Super user only.
 
     Args:
         start_date: Filter from this date (YYYY-MM-DD), optional
@@ -2511,32 +2524,18 @@ async def api_get_manual_payment_requests(
 @castle_api_router.get("/api/v1/manual-payment-requests/all")
 async def api_get_all_manual_payment_requests(
     status: str = None,
-    wallet: WalletTypeInfo = Depends(require_admin_key),
+    auth: AuthContext = Depends(require_super_user),
 ) -> list[ManualPaymentRequest]:
-    """Get all manual payment requests (Castle admin only)"""
-    from lnbits.settings import settings as lnbits_settings
-
-    if wallet.wallet.user != lnbits_settings.super_user:
-        raise HTTPException(
-            status_code=HTTPStatus.FORBIDDEN,
-            detail="Only super user can access this endpoint",
-        )
+    """Get all manual payment requests (super user only)"""
     return await get_all_manual_payment_requests(status)
 
 
 @castle_api_router.post("/api/v1/manual-payment-requests/{request_id}/approve")
 async def api_approve_manual_payment_request(
     request_id: str,
-    wallet: WalletTypeInfo = Depends(require_admin_key),
+    auth: AuthContext = Depends(require_super_user),
 ) -> ManualPaymentRequest:
-    """Approve a manual payment request and create accounting entry (Castle admin only)"""
-    from lnbits.settings import settings as lnbits_settings
-
-    if wallet.wallet.user != lnbits_settings.super_user:
-        raise HTTPException(
-            status_code=HTTPStatus.FORBIDDEN,
-            detail="Only super user can access this endpoint",
-        )
+    """Approve a manual payment request and create accounting entry (super user only)"""
 
     # Get the request
     request = await get_manual_payment_request(request_id)
@@ -2604,17 +2603,9 @@ async def api_approve_manual_payment_request(
 @castle_api_router.post("/api/v1/manual-payment-requests/{request_id}/reject")
 async def api_reject_manual_payment_request(
     request_id: str,
-    wallet: WalletTypeInfo = Depends(require_admin_key),
+    auth: AuthContext = Depends(require_super_user),
 ) -> ManualPaymentRequest:
-    """Reject a manual payment request (Castle admin only)"""
-    from lnbits.settings import settings as lnbits_settings
-
-    if wallet.wallet.user != lnbits_settings.super_user:
-        raise HTTPException(
-            status_code=HTTPStatus.FORBIDDEN,
-            detail="Only super user can access this endpoint",
-        )
-
+    """Reject a manual payment request (super user only)"""
     # Get the request
     request = await get_manual_payment_request(request_id)
     if not request:
@@ -2629,7 +2620,7 @@ async def api_reject_manual_payment_request(
             detail=f"Request already {request.status}",
         )
 
-    return await reject_manual_payment_request(request_id, wallet.wallet.user)
+    return await reject_manual_payment_request(request_id, auth.user_id)
 
 
 # ===== EXPENSE APPROVAL ENDPOINTS =====
@@ -2638,29 +2629,22 @@ async def api_reject_manual_payment_request(
 @castle_api_router.post("/api/v1/entries/{entry_id}/approve")
 async def api_approve_expense_entry(
     entry_id: str,
-    wallet: WalletTypeInfo = Depends(require_admin_key),
+    auth: AuthContext = Depends(require_super_user),
 ) -> dict:
     """
-    Approve a pending expense entry by changing flag from '!' to '*' (admin only).
+    Approve a pending expense entry by changing flag from '!' to '*' (super user only).
 
     This updates the transaction in the Beancount file via Fava API.
     """
-    from lnbits.settings import settings as lnbits_settings
+    import httpx
     from .fava_client import get_fava_client
 
-    if wallet.wallet.user != lnbits_settings.super_user:
-        raise HTTPException(
-            status_code=HTTPStatus.FORBIDDEN,
-            detail="Only super user can approve expenses",
-        )
-
     fava = get_fava_client()
 
     # 1. Get all journal entries from Fava
     all_entries = await fava.get_journal_entries()
 
     # 2. Find the entry with matching castle ID in links
-    target_entry_hash = None
     target_entry = None
 
     for entry in all_entries:
@@ -2672,51 +2656,86 @@ async def api_approve_expense_entry(
                 link_clean = link.lstrip('^')
                 # Check if this entry has our castle ID
                 if link_clean == f"castle-{entry_id}" or link_clean.endswith(f"-{entry_id}"):
-                    target_entry_hash = entry.get("entry_hash")
                     target_entry = entry
                     break
-            if target_entry_hash:
+            if target_entry:
                 break
 
-    if not target_entry_hash:
+    if not target_entry:
         raise HTTPException(
             status_code=HTTPStatus.NOT_FOUND,
             detail=f"Pending entry {entry_id} not found in Beancount ledger"
         )
 
-    # 3. Get the entry context (source text + sha256sum)
-    context = await fava.get_entry_context(target_entry_hash)
-    source = context.get("slice", "")
-    sha256sum = context.get("sha256sum", "")
-
-    if not source:
-        raise HTTPException(
-            status_code=HTTPStatus.INTERNAL_SERVER_ERROR,
-            detail="Could not retrieve entry source from Fava"
-        )
-
-    # 4. Change flag from ! to *
-    # Replace the first occurrence of the date + ! pattern
-    import re
+    # Get entry metadata for file location
+    meta = target_entry.get("meta", {})
+    filename = meta.get("filename")
+    lineno = meta.get("lineno")
     date_str = target_entry.get("date", "")
-    old_pattern = f"{date_str} !"
-    new_pattern = f"{date_str} *"
 
-    if old_pattern not in source:
+    if not filename or not lineno:
         raise HTTPException(
             status_code=HTTPStatus.INTERNAL_SERVER_ERROR,
-            detail=f"Could not find pending flag pattern '{old_pattern}' in entry source"
+            detail="Entry metadata missing filename or lineno"
         )
 
-    new_source = source.replace(old_pattern, new_pattern, 1)
+    # 3. Get the source file from Fava
+    async with httpx.AsyncClient(timeout=fava.timeout) as client:
+        response = await client.get(
+            f"{fava.base_url}/source",
+            params={"filename": filename}
+        )
+        response.raise_for_status()
+        source_data = response.json()["data"]
 
-    # 5. Update the entry via Fava API
-    await fava.update_entry_source(target_entry_hash, new_source, sha256sum)
+        sha256sum = source_data["sha256sum"]
+        source = source_data["source"]
+        lines = source.split('\n')
+
+        # 4. Find and modify the entry at the specified line
+        # Line numbers are 1-indexed, list is 0-indexed
+        entry_line_idx = lineno - 1
+
+        if entry_line_idx >= len(lines):
+            raise HTTPException(
+                status_code=HTTPStatus.INTERNAL_SERVER_ERROR,
+                detail=f"Line {lineno} not found in source file"
+            )
+
+        entry_line = lines[entry_line_idx]
+
+        # Check if the line contains the pending flag pattern
+        old_pattern = f"{date_str} !"
+        if old_pattern not in entry_line:
+            raise HTTPException(
+                status_code=HTTPStatus.INTERNAL_SERVER_ERROR,
+                detail=f"Line {lineno} does not contain expected pattern '{old_pattern}'. Found: {entry_line}"
+            )
+
+        # Replace the flag
+        new_pattern = f"{date_str} *"
+        new_line = entry_line.replace(old_pattern, new_pattern, 1)
+        lines[entry_line_idx] = new_line
+
+        # 5. Write back the modified source
+        new_source = '\n'.join(lines)
+
+        update_response = await client.put(
+            f"{fava.base_url}/source",
+            json={
+                "file_path": filename,
+                "source": new_source,
+                "sha256sum": sha256sum
+            },
+            headers={"Content-Type": "application/json"}
+        )
+        update_response.raise_for_status()
+
+    logger.info(f"Entry {entry_id} approved (flag changed to *)")
 
     return {
         "message": f"Entry {entry_id} approved successfully",
         "entry_id": entry_id,
-        "entry_hash": target_entry_hash,
         "date": date_str,
         "description": target_entry.get("narration", "")
     }
@@ -2725,30 +2744,23 @@ async def api_approve_expense_entry(
 @castle_api_router.post("/api/v1/entries/{entry_id}/reject")
 async def api_reject_expense_entry(
     entry_id: str,
-    wallet: WalletTypeInfo = Depends(require_admin_key),
+    auth: AuthContext = Depends(require_super_user),
 ) -> dict:
     """
-    Reject a pending expense entry by marking it as voided (admin only).
+    Reject a pending expense entry by marking it as voided (super user only).
 
     Adds #voided tag for audit trail while keeping the '!' flag.
     Voided transactions are excluded from balances but preserved in the ledger.
     """
-    from lnbits.settings import settings as lnbits_settings
+    import httpx
     from .fava_client import get_fava_client
 
-    if wallet.wallet.user != lnbits_settings.super_user:
-        raise HTTPException(
-            status_code=HTTPStatus.FORBIDDEN,
-            detail="Only super user can reject expenses",
-        )
-
     fava = get_fava_client()
 
     # 1. Get all journal entries from Fava
     all_entries = await fava.get_journal_entries()
 
     # 2. Find the entry with matching castle ID in links
-    target_entry_hash = None
     target_entry = None
 
     for entry in all_entries:
@@ -2760,58 +2772,77 @@ async def api_reject_expense_entry(
                 link_clean = link.lstrip('^')
                 # Check if this entry has our castle ID
                 if link_clean == f"castle-{entry_id}" or link_clean.endswith(f"-{entry_id}"):
-                    target_entry_hash = entry.get("entry_hash")
                     target_entry = entry
                     break
-            if target_entry_hash:
+            if target_entry:
                 break
 
-    if not target_entry_hash:
+    if not target_entry:
         raise HTTPException(
             status_code=HTTPStatus.NOT_FOUND,
             detail=f"Pending entry {entry_id} not found in Beancount ledger"
         )
 
-    # 3. Get the entry context (source text + sha256sum)
-    context = await fava.get_entry_context(target_entry_hash)
-    source = context.get("slice", "")
-    sha256sum = context.get("sha256sum", "")
-
-    if not source:
-        raise HTTPException(
-            status_code=HTTPStatus.INTERNAL_SERVER_ERROR,
-            detail="Could not retrieve entry source from Fava"
-        )
-
-    # 4. Add #voided tag (keep ! flag as per convention)
+    # Get entry metadata for file location
+    meta = target_entry.get("meta", {})
+    filename = meta.get("filename")
+    lineno = meta.get("lineno")
     date_str = target_entry.get("date", "")
 
-    # Add #voided tag if not already present
-    if "#voided" not in source:
-        # Find the transaction line and add #voided to the tags
-        # Pattern: date ! "narration" #existing-tags
-        lines = source.split('\n')
-        for i, line in enumerate(lines):
-            if date_str in line and '"' in line and '!' in line:
-                # Add #voided tag to the transaction line
-                if '#' in line:
-                    # Already has tags, append voided
-                    lines[i] = line.rstrip() + ' #voided'
-                else:
-                    # No tags yet, add after narration
-                    lines[i] = line.rstrip() + ' #voided'
-                break
-        new_source = '\n'.join(lines)
-    else:
-        new_source = source
+    if not filename or not lineno:
+        raise HTTPException(
+            status_code=HTTPStatus.INTERNAL_SERVER_ERROR,
+            detail="Entry metadata missing filename or lineno"
+        )
 
-    # 5. Update the entry via Fava API
-    await fava.update_entry_source(target_entry_hash, new_source, sha256sum)
+    # 3. Get the source file from Fava
+    async with httpx.AsyncClient(timeout=fava.timeout) as client:
+        response = await client.get(
+            f"{fava.base_url}/source",
+            params={"filename": filename}
+        )
+        response.raise_for_status()
+        source_data = response.json()["data"]
+
+        sha256sum = source_data["sha256sum"]
+        source = source_data["source"]
+        lines = source.split('\n')
+
+        # 4. Find and modify the entry at the specified line - add #voided tag
+        entry_line_idx = lineno - 1
+
+        if entry_line_idx >= len(lines):
+            raise HTTPException(
+                status_code=HTTPStatus.INTERNAL_SERVER_ERROR,
+                detail=f"Line {lineno} not found in source file"
+            )
+
+        entry_line = lines[entry_line_idx]
+
+        # Add #voided tag if not already present
+        if "#voided" not in entry_line:
+            # Add #voided tag to the transaction line
+            new_line = entry_line.rstrip() + ' #voided'
+            lines[entry_line_idx] = new_line
+
+            # 5. Write back the modified source
+            new_source = '\n'.join(lines)
+
+            update_response = await client.put(
+                f"{fava.base_url}/source",
+                json={
+                    "file_path": filename,
+                    "source": new_source,
+                    "sha256sum": sha256sum
+                },
+                headers={"Content-Type": "application/json"}
+            )
+            update_response.raise_for_status()
+            logger.info(f"Entry {entry_id} rejected (added #voided tag)")
 
     return {
         "message": f"Entry {entry_id} rejected (marked as voided)",
         "entry_id": entry_id,
-        "entry_hash": target_entry_hash,
         "date": date_str,
         "description": target_entry.get("narration", "")
     }
@@ -2823,10 +2854,10 @@ async def api_reject_expense_entry(
 @castle_api_router.post("/api/v1/assertions")
 async def api_create_balance_assertion(
     data: CreateBalanceAssertion,
-    wallet: WalletTypeInfo = Depends(require_admin_key),
+    auth: AuthContext = Depends(require_super_user),
 ) -> BalanceAssertion:
     """
-    Create a balance assertion for reconciliation (admin only).
+    Create a balance assertion for reconciliation (super user only).
 
     Uses hybrid approach:
     1. Writes balance assertion to Beancount (via Fava) - source of truth
@@ -2835,16 +2866,9 @@ async def api_create_balance_assertion(
 
     The assertion will be checked immediately upon creation.
     """
-    from lnbits.settings import settings as lnbits_settings
     from .fava_client import get_fava_client
     from .beancount_format import format_balance
 
-    if wallet.wallet.user != lnbits_settings.super_user:
-        raise HTTPException(
-            status_code=HTTPStatus.FORBIDDEN,
-            detail="Only super user can create balance assertions",
-        )
-
     # Verify account exists
     account = await get_account(data.account_id)
     if not account:
@@ -2876,7 +2900,7 @@ async def api_create_balance_assertion(
         )
 
     # Store metadata in Castle DB for UI convenience
-    assertion = await create_balance_assertion(data, wallet.wallet.user)
+    assertion = await create_balance_assertion(data, auth.user_id)
 
     # Check it immediately (queries Fava for actual balance)
     try:
@@ -2911,16 +2935,9 @@ async def api_get_balance_assertions(
     account_id: str = None,
     status: str = None,
     limit: int = 100,
-    wallet: WalletTypeInfo = Depends(require_admin_key),
+    auth: AuthContext = Depends(require_super_user),
 ) -> list[BalanceAssertion]:
-    """Get balance assertions with optional filters (admin only)"""
-    from lnbits.settings import settings as lnbits_settings
-
-    if wallet.wallet.user != lnbits_settings.super_user:
-        raise HTTPException(
-            status_code=HTTPStatus.FORBIDDEN,
-            detail="Only super user can view balance assertions",
-        )
+    """Get balance assertions with optional filters (super user only)"""
 
     # Parse status enum if provided
     status_enum = None
@@ -2943,17 +2960,9 @@ async def api_get_balance_assertions(
 @castle_api_router.get("/api/v1/assertions/{assertion_id}")
 async def api_get_balance_assertion(
     assertion_id: str,
-    wallet: WalletTypeInfo = Depends(require_admin_key),
+    auth: AuthContext = Depends(require_super_user),
 ) -> BalanceAssertion:
-    """Get a specific balance assertion (admin only)"""
-    from lnbits.settings import settings as lnbits_settings
-
-    if wallet.wallet.user != lnbits_settings.super_user:
-        raise HTTPException(
-            status_code=HTTPStatus.FORBIDDEN,
-            detail="Only super user can view balance assertions",
-        )
-
+    """Get a specific balance assertion (super user only)"""
     assertion = await get_balance_assertion(assertion_id)
     if not assertion:
         raise HTTPException(
@@ -2967,17 +2976,9 @@ async def api_get_balance_assertion(
 @castle_api_router.post("/api/v1/assertions/{assertion_id}/check")
 async def api_check_balance_assertion(
     assertion_id: str,
-    wallet: WalletTypeInfo = Depends(require_admin_key),
+    auth: AuthContext = Depends(require_super_user),
 ) -> BalanceAssertion:
-    """Re-check a balance assertion (admin only)"""
-    from lnbits.settings import settings as lnbits_settings
-
-    if wallet.wallet.user != lnbits_settings.super_user:
-        raise HTTPException(
-            status_code=HTTPStatus.FORBIDDEN,
-            detail="Only super user can check balance assertions",
-        )
-
+    """Re-check a balance assertion (super user only)"""
     try:
         assertion = await check_balance_assertion(assertion_id)
     except ValueError as e:
@@ -2992,17 +2993,9 @@ async def api_check_balance_assertion(
 @castle_api_router.delete("/api/v1/assertions/{assertion_id}")
 async def api_delete_balance_assertion(
     assertion_id: str,
-    wallet: WalletTypeInfo = Depends(require_admin_key),
+    auth: AuthContext = Depends(require_super_user),
 ) -> dict:
-    """Delete a balance assertion (admin only)"""
-    from lnbits.settings import settings as lnbits_settings
-
-    if wallet.wallet.user != lnbits_settings.super_user:
-        raise HTTPException(
-            status_code=HTTPStatus.FORBIDDEN,
-            detail="Only super user can delete balance assertions",
-        )
-
+    """Delete a balance assertion (super user only)"""
     # Verify it exists
     assertion = await get_balance_assertion(assertion_id)
     if not assertion:
@@ -3021,16 +3014,9 @@ async def api_delete_balance_assertion(
 
 @castle_api_router.get("/api/v1/reconciliation/summary")
 async def api_get_reconciliation_summary(
-    wallet: WalletTypeInfo = Depends(require_admin_key),
+    auth: AuthContext = Depends(require_super_user),
 ) -> dict:
-    """Get reconciliation summary (admin only)"""
-    from lnbits.settings import settings as lnbits_settings
-
-    if wallet.wallet.user != lnbits_settings.super_user:
-        raise HTTPException(
-            status_code=HTTPStatus.FORBIDDEN,
-            detail="Only super user can access reconciliation",
-        )
+    """Get reconciliation summary (super user only)"""
 
     # Get all assertions
     all_assertions = await get_balance_assertions(limit=1000)
@@ -3079,16 +3065,9 @@ async def api_get_reconciliation_summary(
 
 @castle_api_router.post("/api/v1/reconciliation/check-all")
 async def api_check_all_assertions(
-    wallet: WalletTypeInfo = Depends(require_admin_key),
+    auth: AuthContext = Depends(require_super_user),
 ) -> dict:
-    """Re-check all balance assertions (admin only)"""
-    from lnbits.settings import settings as lnbits_settings
-
-    if wallet.wallet.user != lnbits_settings.super_user:
-        raise HTTPException(
-            status_code=HTTPStatus.FORBIDDEN,
-            detail="Only super user can run reconciliation checks",
-        )
+    """Re-check all balance assertions (super user only)"""
 
     # Get all assertions
     all_assertions = await get_balance_assertions(limit=1000)
@@ -3117,16 +3096,9 @@ async def api_check_all_assertions(
 
 @castle_api_router.get("/api/v1/reconciliation/discrepancies")
 async def api_get_discrepancies(
-    wallet: WalletTypeInfo = Depends(require_admin_key),
+    auth: AuthContext = Depends(require_super_user),
 ) -> dict:
-    """Get all discrepancies (failed assertions, flagged entries) (admin only)"""
-    from lnbits.settings import settings as lnbits_settings
-
-    if wallet.wallet.user != lnbits_settings.super_user:
-        raise HTTPException(
-            status_code=HTTPStatus.FORBIDDEN,
-            detail="Only super user can view discrepancies",
-        )
+    """Get all discrepancies (failed assertions, flagged entries) (super user only)"""
 
     # Get failed assertions
     failed_assertions = await get_balance_assertions(
@@ -3154,21 +3126,14 @@ async def api_get_discrepancies(
 
 @castle_api_router.post("/api/v1/tasks/daily-reconciliation")
 async def api_run_daily_reconciliation(
-    wallet: WalletTypeInfo = Depends(require_admin_key),
+    auth: AuthContext = Depends(require_super_user),
 ) -> dict:
     """
-    Manually trigger the daily reconciliation check (admin only).
+    Manually trigger the daily reconciliation check (super user only).
     This endpoint can also be called via cron job.
 
     Returns a summary of the reconciliation check results.
     """
-    from lnbits.settings import settings as lnbits_settings
-
-    if wallet.wallet.user != lnbits_settings.super_user:
-        raise HTTPException(
-            status_code=HTTPStatus.FORBIDDEN,
-            detail="Only super user can run daily reconciliation",
-        )
 
     from .tasks import check_all_balance_assertions