docs: add HTTP server environment variables

Author: jruokola

.env.example

@@ -309,3 +309,18 @@ PROMETHEUS_PORT=9090
 DEV_MODE=true
 DISABLE_AUTH=false  # Never set to true in production!
 ENABLE_DEBUG_ENDPOINTS=false
+
+# ============================================================================
+# HTTP Server Configuration (when using --transport http)
+# ============================================================================
+
+# Host address to bind HTTP server (default: 127.0.0.1)
+# Use 0.0.0.0 to allow external connections
+CODEGRAPH_HTTP_HOST=127.0.0.1
+
+# Port for HTTP server (default: 3000)
+CODEGRAPH_HTTP_PORT=3000
+
+# SSE keep-alive interval in seconds (default: 15)
+# Prevents proxy timeouts for long-running agentic operations
+CODEGRAPH_HTTP_KEEP_ALIVE=15