fix: resolve read-only file system issues for Nix packaging

- Add config_paths.py for XDG-compliant path resolution
- Update all servers to use user-writable locations (logs, tokens, .env)
- Make .env file optional - server works with environment variables only
- Default paths: ~/.local/share for data, ~/.local/state for logs
- Update Nix wrapper with XDG defaults and helpful postInstall message
- Update README.md with environment variable configuration documentation

Fixes OSError when running in Nix store (read-only filesystem)

README.md

@@ -2,9 +2,48 @@
 
 This project provides a **FastMCP-powered** integration for Basecamp 3, allowing Cursor to interact with Basecamp directly through the MCP protocol.
 
-✅ **Migration Complete:** Successfully migrated to official Anthropic FastMCP framework with **100% feature parity** (all 46 tools)  
+✅ **Migration Complete:** Successfully migrated to official Anthropic FastMCP framework with **100% feature parity** (all 46 tools)
 🚀 **Ready for Production:** Full protocol compliance with MCP 2025-06-18
 
+## Configuration
+
+The Basecamp MCP server is configured entirely via environment variables. No `.env` file is required.
+
+### Required Environment Variables
+
+All required configuration is passed via environment variables:
+
+- `BASECAMP_CLIENT_ID` - OAuth client ID from 37signals
+- `BASECAMP_CLIENT_SECRET` - OAuth client secret from 37signals
+- `BASECAMP_ACCOUNT_ID` - Your Basecamp account ID
+- `BASECAMP_REDIRECT_URI` - OAuth callback URL (usually `http://localhost:8000/auth/callback`)
+- `USER_AGENT` - User agent string for API requests
+
+### Data Locations
+
+The server stores data in XDG-compliant locations:
+
+| File Type | Default Location | Environment Variable Override |
+|-----------|------------------|-------------------------------|
+| OAuth Tokens | `~/.local/share/basecamp-mcp/oauth_tokens.json` | `BASECAMP_TOKEN_FILE` |
+| Server Logs | `~/.local/state/basecamp-mcp/` | `BASECAMP_LOG_DIR` |
+
+### Optional .env File (Development Only)
+
+For local development, you can optionally create a `.env` file to avoid setting environment variables each time:
+
+```bash
+# Default location: ~/.config/basecamp-mcp/.env
+# Or override with: BASECAMP_ENV_FILE=/custom/path/.env
+BASECAMP_CLIENT_ID=your_client_id_here
+BASECAMP_CLIENT_SECRET=your_client_secret_here
+BASECAMP_ACCOUNT_ID=your_account_id_here
+BASECAMP_REDIRECT_URI=http://localhost:8000/auth/callback
+USER_AGENT="Your App Name (your@email.com)"
+```
+
+**Note:** The server works perfectly without a `.env` file - it's only a convenience for development.
+
 ## Quick Setup
 
 This server works with both **Cursor** and **Claude Desktop**. Choose your preferred client:

config_paths.py

@@ -0,0 +1,92 @@
+"""
+Centralized path resolution for Basecamp MCP Server.
+
+All paths can be overridden via environment variables.
+"""
+
+import os
+from pathlib import Path
+
+
+def get_log_directory() -> Path:
+    """
+    Get the directory for log files.
+
+    Priority order:
+    1. BASECAMP_LOG_DIR env variable
+    2. XDG_STATE_HOME (typically ~/.local/state)
+    3. ~/.local/state/basecamp-mcp (fallback)
+    """
+    if log_dir := os.getenv("BASECAMP_LOG_DIR"):
+        return Path(log_dir)
+
+    if xdg_state := os.getenv("XDG_STATE_HOME"):
+        return Path(xdg_state) / "basecamp-mcp"
+
+    return Path.home() / ".local/state/basecamp-mcp"
+
+
+def get_config_directory() -> Path:
+    """
+    Get the directory for configuration files (.env).
+
+    Priority order:
+    1. BASECAMP_CONFIG_DIR env variable
+    2. XDG_CONFIG_HOME (typically ~/.config)
+    3. ~/.config/basecamp-mcp (fallback)
+
+    NOTE: This is only used if BASECAMP_ENV_FILE is not set and
+    a .env file exists in the config directory. The server works
+    entirely with environment variables and doesn't require .env files.
+    """
+    if config_dir := os.getenv("BASECAMP_CONFIG_DIR"):
+        return Path(config_dir)
+
+    if xdg_config := os.getenv("XDG_CONFIG_HOME"):
+        return Path(xdg_config) / "basecamp-mcp"
+
+    return Path.home() / ".config/basecamp-mcp"
+
+
+def get_env_file_path() -> Path:
+    """
+    Get the path for .env file (optional).
+
+    Priority order:
+    1. BASECAMP_ENV_FILE env variable (explicitly specified)
+    2. Config directory + / .env
+
+    The server does NOT require this file - it's optional.
+    If not found, environment will be used as-is.
+    """
+    if env_file := os.getenv("BASECAMP_ENV_FILE"):
+        return Path(env_file)
+
+    return get_config_directory() / ".env"
+
+
+def get_token_file_path() -> Path:
+    """
+    Get the path for OAuth token storage.
+
+    Priority order:
+    1. BASECAMP_TOKEN_FILE env variable
+    2. XDG_DATA_HOME (typically ~/.local/share)
+    3. ~/.local/share/basecamp-mcp/oauth_tokens.json (fallback)
+    """
+    if token_file := os.getenv("BASECAMP_TOKEN_FILE"):
+        return Path(token_file)
+
+    if xdg_data := os.getenv("XDG_DATA_HOME"):
+        return Path(xdg_data) / "basecamp-mcp" / "oauth_tokens.json"
+
+    return Path.home() / ".local/share/basecamp-mcp" / "oauth_tokens.json"
+
+
+def ensure_directories_exist() -> None:
+    """
+    Create all necessary directories if they don't exist.
+    """
+    get_log_directory().mkdir(parents=True, exist_ok=True)
+    get_config_directory().mkdir(parents=True, exist_ok=True)
+    get_token_file_path().parent.mkdir(parents=True, exist_ok=True)

oauth_app.py

@@ -13,29 +13,47 @@ import sys
 import json
 import secrets
 import logging
-from flask import Flask, request, redirect, url_for, session, render_template_string, jsonify
+from flask import (
+    Flask,
+    request,
+    redirect,
+    url_for,
+    session,
+    render_template_string,
+    jsonify,
+)
 from dotenv import load_dotenv
 from basecamp_oauth import BasecampOAuth
 from basecamp_client import BasecampClient
 from search_utils import BasecampSearch
 import token_storage
 
-# Configure logging
+from config_paths import get_log_directory, get_env_file_path, ensure_directories_exist
+
+ensure_directories_exist()
+
+DOTENV_PATH = get_env_file_path()
+if DOTENV_PATH.exists():
+    load_dotenv(DOTENV_PATH)
+
+LOG_FILE_PATH = get_log_directory() / "oauth_app.log"
 logging.basicConfig(
     level=logging.INFO,
-    format='%(asctime)s - %(name)s - %(levelname)s - %(message)s',
+    format="%(asctime)s - %(name)s - %(levelname)s - %(message)s",
     handlers=[
-        logging.FileHandler("oauth_app.log"),
-        logging.StreamHandler()
-    ]
+        logging.FileHandler(LOG_FILE_PATH),
+        logging.StreamHandler(),
+    ],
 )
 logger = logging.getLogger(__name__)
 
-# Load environment variables
-load_dotenv()
-
 # Check for required environment variables
-required_vars = ['BASECAMP_CLIENT_ID', 'BASECAMP_CLIENT_SECRET', 'BASECAMP_REDIRECT_URI', 'USER_AGENT']
+required_vars = [
+    "BASECAMP_CLIENT_ID",
+    "BASECAMP_CLIENT_SECRET",
+    "BASECAMP_REDIRECT_URI",
+    "USER_AGENT",
+]
 missing_vars = [var for var in required_vars if not os.getenv(var)]
 if missing_vars:
     logger.error(f"Missing required environment variables: {', '.join(missing_vars)}")
@@ -44,7 +62,7 @@ if missing_vars:
 
 # Create Flask app
 app = Flask(__name__)
-app.secret_key = os.getenv('FLASK_SECRET_KEY', secrets.token_hex(16))
+app.secret_key = os.getenv("FLASK_SECRET_KEY", secrets.token_hex(16))
 
 # HTML template for displaying results
 RESULTS_TEMPLATE = """
@@ -109,101 +127,116 @@ RESULTS_TEMPLATE = """
 </html>
 """
 
-@app.template_filter('tojson')
+
+@app.template_filter("tojson")
 def to_json(value, indent=None):
     return json.dumps(value, indent=indent)
 
+
 def get_oauth_client():
     """Get a configured OAuth client."""
     try:
-        client_id = os.getenv('BASECAMP_CLIENT_ID')
-        client_secret = os.getenv('BASECAMP_CLIENT_SECRET')
-        redirect_uri = os.getenv('BASECAMP_REDIRECT_URI')
-        user_agent = os.getenv('USER_AGENT')
+        client_id = os.getenv("BASECAMP_CLIENT_ID")
+        client_secret = os.getenv("BASECAMP_CLIENT_SECRET")
+        redirect_uri = os.getenv("BASECAMP_REDIRECT_URI")
+        user_agent = os.getenv("USER_AGENT")
 
-        logger.info("Creating OAuth client with config: %s, %s, %s", client_id, redirect_uri, user_agent)
+        logger.info(
+            "Creating OAuth client with config: %s, %s, %s",
+            client_id,
+            redirect_uri,
+            user_agent,
+        )
 
         return BasecampOAuth(
             client_id=client_id,
             client_secret=client_secret,
             redirect_uri=redirect_uri,
-            user_agent=user_agent
+            user_agent=user_agent,
         )
     except Exception as e:
         logger.error("Error creating OAuth client: %s", str(e))
         raise
 
+
 def ensure_valid_token():
     """
-    Ensure we have a valid, non-expired token. 
+    Ensure we have a valid, non-expired token.
     Attempts to refresh if expired.
-    
+
     Returns:
         dict: Valid token data or None if authentication is needed
     """
     token_data = token_storage.get_token()
-    
-    if not token_data or not token_data.get('access_token'):
+
+    if not token_data or not token_data.get("access_token"):
         logger.info("No token found")
         return None
-    
+
     # Check if token is expired
     if token_storage.is_token_expired():
         logger.info("Token is expired, attempting to refresh")
-        
-        refresh_token = token_data.get('refresh_token')
+
+        refresh_token = token_data.get("refresh_token")
         if not refresh_token:
             logger.warning("No refresh token available, user needs to re-authenticate")
             return None
-        
+
         try:
             oauth_client = get_oauth_client()
             new_token_data = oauth_client.refresh_token(refresh_token)
-            
+
             # Store the new token
-            access_token = new_token_data.get('access_token')
-            new_refresh_token = new_token_data.get('refresh_token', refresh_token)  # Use old refresh token if new one not provided
-            expires_in = new_token_data.get('expires_in')
-            account_id = token_data.get('account_id')  # Keep the existing account_id
-            
+            access_token = new_token_data.get("access_token")
+            new_refresh_token = new_token_data.get(
+                "refresh_token", refresh_token
+            )  # Use old refresh token if new one not provided
+            expires_in = new_token_data.get("expires_in")
+            account_id = token_data.get("account_id")  # Keep the existing account_id
+
             if access_token:
                 token_storage.store_token(
                     access_token=access_token,
                     refresh_token=new_refresh_token,
                     expires_in=expires_in,
-                    account_id=account_id
+                    account_id=account_id,
                 )
                 logger.info("Token refreshed successfully")
                 return token_storage.get_token()
             else:
                 logger.error("No access token in refresh response")
                 return None
-                
+
         except Exception as e:
             logger.error("Failed to refresh token: %s", str(e))
             return None
-    
+
     logger.info("Token is valid")
     return token_data
 
-@app.route('/')
+
+@app.route("/")
 def home():
     """Home page."""
     # Ensure we have a valid token
     token_data = ensure_valid_token()
 
-    if token_data and token_data.get('access_token'):
+    if token_data and token_data.get("access_token"):
         # We have a valid token, show token information
-        access_token = token_data['access_token']
+        access_token = token_data["access_token"]
         # Mask the token for security
-        masked_token = f"{access_token[:10]}...{access_token[-10:]}" if len(access_token) > 20 else "***"
+        masked_token = (
+            f"{access_token[:10]}...{access_token[-10:]}"
+            if len(access_token) > 20
+            else "***"
+        )
 
         token_info = {
             "access_token": masked_token,
-            "account_id": token_data.get('account_id'),
-            "has_refresh_token": bool(token_data.get('refresh_token')),
-            "expires_at": token_data.get('expires_at'),
-            "updated_at": token_data.get('updated_at')
+            "account_id": token_data.get("account_id"),
+            "has_refresh_token": bool(token_data.get("refresh_token")),
+            "expires_at": token_data.get("expires_at"),
+            "updated_at": token_data.get("updated_at"),
         }
 
         logger.info("Home page: User is authenticated")
@@ -213,7 +246,7 @@ def home():
             title="Basecamp OAuth Status",
             message="You are authenticated with Basecamp!",
             token_info=token_info,
-            show_logout=True
+            show_logout=True,
         )
     else:
         # No valid token, show login button
@@ -227,7 +260,7 @@ def home():
                 RESULTS_TEMPLATE,
                 title="Basecamp OAuth Demo",
                 message="Welcome! Please log in with your Basecamp account to continue.",
-                auth_url=auth_url
+                auth_url=auth_url,
             )
         except Exception as e:
             logger.error("Error getting authorization URL: %s", str(e))
@@ -237,13 +270,14 @@ def home():
                 message=f"Error setting up OAuth: {str(e)}",
             )
 
-@app.route('/auth/callback')
+
+@app.route("/auth/callback")
 def auth_callback():
     """Handle the OAuth callback from Basecamp."""
     logger.info("OAuth callback called with args: %s", request.args)
 
-    code = request.args.get('code')
-    error = request.args.get('error')
+    code = request.args.get("code")
+    error = request.args.get("error")
 
     if error:
         logger.error("OAuth callback error: %s", error)
@@ -251,7 +285,7 @@ def auth_callback():
             RESULTS_TEMPLATE,
             title="Authentication Error",
             message=f"Basecamp returned an error: {error}",
-            show_home=True
+            show_home=True,
         )
 
     if not code:
@@ -260,7 +294,7 @@ def auth_callback():
             RESULTS_TEMPLATE,
             title="Error",
             message="No authorization code received.",
-            show_home=True
+            show_home=True,
         )
 
     try:
@@ -271,10 +305,10 @@ def auth_callback():
         logger.info(f"Raw token data from Basecamp exchange: {token_data}")
 
         # Store the token in our secure storage
-        access_token = token_data.get('access_token')
-        refresh_token = token_data.get('refresh_token')
-        expires_in = token_data.get('expires_in')
-        account_id = os.getenv('BASECAMP_ACCOUNT_ID')
+        access_token = token_data.get("access_token")
+        refresh_token = token_data.get("refresh_token")
+        expires_in = token_data.get("expires_in")
+        account_id = os.getenv("BASECAMP_ACCOUNT_ID")
 
         if not access_token:
             logger.error("OAuth exchange: No access token received")
@@ -282,7 +316,7 @@ def auth_callback():
                 RESULTS_TEMPLATE,
                 title="Authentication Error",
                 message="No access token received from Basecamp.",
-                show_home=True
+                show_home=True,
             )
 
         # Try to get identity if account_id is not set
@@ -293,10 +327,10 @@ def auth_callback():
                 logger.info("Identity response: %s", identity)
 
                 # Find Basecamp 3 account
-                if identity.get('accounts'):
-                    for account in identity['accounts']:
-                        if account.get('product') == 'bc3':  # Basecamp 3
-                            account_id = account['id']
+                if identity.get("accounts"):
+                    for account in identity["accounts"]:
+                        if account.get("product") == "bc3":  # Basecamp 3
+                            account_id = account["id"]
                             logger.info("Found account_id: %s", account_id)
                             break
             except Exception as identity_error:
@@ -308,7 +342,7 @@ def auth_callback():
             access_token=access_token,
             refresh_token=refresh_token,
             expires_in=expires_in,
-            account_id=account_id
+            account_id=account_id,
         )
 
         if not stored:
@@ -317,29 +351,30 @@ def auth_callback():
                 RESULTS_TEMPLATE,
                 title="Error",
                 message="Failed to store token. Please try again.",
-                show_home=True
+                show_home=True,
             )
 
         # Also keep the access token in session for convenience
-        session['access_token'] = access_token
+        session["access_token"] = access_token
         if refresh_token:
-            session['refresh_token'] = refresh_token
+            session["refresh_token"] = refresh_token
         if account_id:
-            session['account_id'] = account_id
+            session["account_id"] = account_id
 
         logger.info("OAuth flow completed successfully")
 
-        return redirect(url_for('home'))
+        return redirect(url_for("home"))
     except Exception as e:
         logger.error("Error in OAuth callback: %s", str(e), exc_info=True)
         return render_template_string(
             RESULTS_TEMPLATE,
             title="Error",
             message=f"Failed to exchange code for token: {str(e)}",
-            show_home=True
+            show_home=True,
         )
 
-@app.route('/api/token', methods=['GET'])
+
+@app.route("/api/token", methods=["GET"])
 def get_token_api():
     """
     Secure API endpoint for the MCP server to get the token.
@@ -349,38 +384,40 @@ def get_token_api():
 
     # In production, implement proper authentication for this endpoint
     # For now, we'll use a simple API key check
-    api_key = request.headers.get('X-API-Key')
-    if not api_key or api_key != os.getenv('MCP_API_KEY', 'mcp_secret_key'):
+    api_key = request.headers.get("X-API-Key")
+    if not api_key or api_key != os.getenv("MCP_API_KEY", "mcp_secret_key"):
         logger.error("Token API: Invalid API key")
-        return jsonify({
-            "error": "Unauthorized",
-            "message": "Invalid or missing API key"
-        }), 401
+        return jsonify(
+            {"error": "Unauthorized", "message": "Invalid or missing API key"}
+        ), 401
 
     # Use the ensure_valid_token function to get a fresh token
     token_data = ensure_valid_token()
-    if not token_data or not token_data.get('access_token'):
+    if not token_data or not token_data.get("access_token"):
         logger.error("Token API: No valid token available")
-        return jsonify({
-            "error": "Not authenticated",
-            "message": "No valid token available"
-        }), 404
+        return jsonify(
+            {"error": "Not authenticated", "message": "No valid token available"}
+        ), 404
 
     logger.info("Token API: Successfully returned token")
-    return jsonify({
-        "access_token": token_data['access_token'],
-        "account_id": token_data.get('account_id')
-    })
+    return jsonify(
+        {
+            "access_token": token_data["access_token"],
+            "account_id": token_data.get("account_id"),
+        }
+    )
 
-@app.route('/logout')
+
+@app.route("/logout")
 def logout():
     """Clear the session and token storage."""
     logger.info("Logout called")
     session.clear()
     token_storage.clear_tokens()
-    return redirect(url_for('home'))
+    return redirect(url_for("home"))
 
-@app.route('/token/info')
+
+@app.route("/token/info")
 def token_info():
     """Display information about the stored token."""
     logger.info("Token info called")
@@ -392,26 +429,36 @@ def token_info():
             RESULTS_TEMPLATE,
             title="Token Information",
             message="No token stored.",
-            show_home=True
+            show_home=True,
         )
 
     # Check if token is expired
     is_expired = token_storage.is_token_expired()
-    
-    # Mask the tokens for security
-    access_token = token_data.get('access_token', '')
-    refresh_token = token_data.get('refresh_token', '')
 
-    masked_access = f"{access_token[:10]}...{access_token[-10:]}" if len(access_token) > 20 else "***"
-    masked_refresh = f"{refresh_token[:10]}...{refresh_token[-10:]}" if refresh_token and len(refresh_token) > 20 else "***" if refresh_token else None
+    # Mask the tokens for security
+    access_token = token_data.get("access_token", "")
+    refresh_token = token_data.get("refresh_token", "")
+
+    masked_access = (
+        f"{access_token[:10]}...{access_token[-10:]}"
+        if len(access_token) > 20
+        else "***"
+    )
+    masked_refresh = (
+        f"{refresh_token[:10]}...{refresh_token[-10:]}"
+        if refresh_token and len(refresh_token) > 20
+        else "***"
+        if refresh_token
+        else None
+    )
 
     display_info = {
         "access_token": masked_access,
         "has_refresh_token": bool(refresh_token),
-        "account_id": token_data.get('account_id'),
-        "expires_at": token_data.get('expires_at'),
-        "updated_at": token_data.get('updated_at'),
-        "is_expired": is_expired
+        "account_id": token_data.get("account_id"),
+        "expires_at": token_data.get("expires_at"),
+        "updated_at": token_data.get("updated_at"),
+        "is_expired": is_expired,
     }
 
     warning_message = None
@@ -424,29 +471,28 @@ def token_info():
         title="Token Information",
         content=json.dumps(display_info, indent=2),
         warning=warning_message,
-        show_home=True
+        show_home=True,
     )
 
-@app.route('/health')
+
+@app.route("/health")
 def health_check():
     """Health check endpoint."""
     logger.info("Health check called")
-    return jsonify({
-        "status": "ok",
-        "service": "basecamp-oauth-app"
-    })
+    return jsonify({"status": "ok", "service": "basecamp-oauth-app"})
 
-if __name__ == '__main__':
+
+if __name__ == "__main__":
     try:
-        logger.info("Starting OAuth app on port %s", os.environ.get('PORT', 8000))
+        logger.info("Starting OAuth app on port %s", os.environ.get("PORT", 8000))
         # Run the Flask app
-        port = int(os.environ.get('PORT', 8000))
+        port = int(os.environ.get("PORT", 8000))
 
         # Disable debug and auto-reloader when running in production or background
-        is_debug = os.environ.get('FLASK_DEBUG', 'False').lower() == 'true'
+        is_debug = os.environ.get("FLASK_DEBUG", "False").lower() == "true"
 
         logger.info("Running in %s mode", "debug" if is_debug else "production")
-        app.run(host='0.0.0.0', port=port, debug=is_debug, use_reloader=is_debug)
+        app.run(host="0.0.0.0", port=port, debug=is_debug, use_reloader=is_debug)
     except Exception as e:
         logger.error("Fatal error: %s", str(e), exc_info=True)
         sys.exit(1)

token_storage.py

@@ -12,12 +12,12 @@ import threading
 from datetime import datetime, timedelta
 import logging
 
-# Determine the directory where this script (token_storage.py) is located
+from config_paths import get_token_file_path
+
 SCRIPT_DIR = os.path.dirname(os.path.abspath(__file__))
-# Allow token file location to be configured via environment variable
-# Falls back to oauth_tokens.json in the script directory if not set
 TOKEN_FILE = os.environ.get(
-    "BASECAMP_TOKEN_FILE", os.path.join(SCRIPT_DIR, "oauth_tokens.json")
+    "BASECAMP_TOKEN_FILE",
+    str(get_token_file_path()),
 )
 
 # Lock for thread-safe operations