I've been following the nextjs.org/learn tutorial exactly, but when I get to "Chapter 15: Adding Authentication", I get the error "Error: Cannot find the middleware module". I can't for the life of me work out what is wrong.
Error: Cannot find the middleware module at DevServer.runMiddleware (file:///Users/xyz/projects/nextjs-dashboard/node_modules/.pnpm/next@15.3.2_react-dom@19.1.0_react.1.0__react@19.1.0/node_modules/next/dist/server/next-server.js:1159:23) at async DevServer.runMiddleware (file:///Users/xyz/projects/nextjs-dashboard/node_modules/.pnpm/next@15.3.2_react-dom@19.1.0_react.1.0__react@19.1.0/node_modules/next/dist/server/dev/next-dev-server.js:270:28) at async NextNodeServer.handleCatchallMiddlewareRequest (file:///Users/xyz/projects/nextjs-dashboard/node_modules/.pnpm/next@15.3.2_react-dom@19.1.0_react.1.0__react@19.1.0/node_modules/next/dist/server/next-server.js:359:26) at async DevServer.handleRequestImpl (file:///Users/xyz/projects/nextjs-dashboard/node_modules/.pnpm/next@15.3.2_react-dom@19.1.0_react.1.0__react@19.1.0/node_modules/next/dist/server/base-server.js:905:28) at async (file:///Users/xyz/projects/nextjs-dashboard/node_modules/.pnpm/next@15.3.2_react-dom@19.1.0_react.1.0__react@19.1.0/node_modules/next/dist/server/dev/next-dev-server.js:371:20) at async Span.traceAsyncFn (file:///Users/xyz/projects/nextjs-dashboard/node_modules/.pnpm/next@15.3.2_react-dom@19.1.0_react.1.0__react@19.1.0/node_modules/next/dist/trace/trace.js:157:20) at async DevServer.handleRequest (file:///Users/xyz/projects/nextjs-dashboard/node_modules/.pnpm/next@15.3.2_react-dom@19.1.0_react.1.0__react@19.1.0/node_modules/next/dist/server/dev/next-dev-server.js:368:24) at async handleRoute (file:///Users/xyz/projects/nextjs-dashboard/node_modules/.pnpm/next@15.3.2_react-dom@19.1.0_react.1.0__react@19.1.0/node_modules/next/dist/server/lib/router-utils/resolve-routes.js:317:33) at async resolveRoutes (file:///Users/xyz/projects/nextjs-dashboard/node_modules/.pnpm/next@15.3.2_react-dom@19.1.0_react.1.0__react@19.1.0/node_modules/next/dist/server/lib/router-utils/resolve-routes.js:572:28) at async handleRequest (file:///Users/xyz/projects/nextjs-dashboard/node_modules/.pnpm/next@15.3.2_react-dom@19.1.0_react.1.0__react@19.1.0/node_modules/next/dist/server/lib/router-server.js:281:96) at async requestHandlerImpl (file:///Users/xyz/projects/nextjs-dashboard/node_modules/.pnpm/next@15.3.2_react-dom@19.1.0_react.1.0__react@19.1.0/node_modules/next/dist/server/lib/router-server.js:452:13) at async Server.requestListener (file:///Users/xyz/projects/nextjs-dashboard/node_modules/.pnpm/next@15.3.2_react-dom@19.1.0_react.1.0__react@19.1.0/node_modules/next/dist/server/lib/start-server.js:158:13)