Developer Debugging Guides
Step-by-step fixes for Next.js, Supabase, Cursor AI, shadcn/ui, Tailwind, and Vercel errors. Real error messages, real solutions.
Fix 'ReferenceError: window is not defined' in Next.js App Router (2026)
Getting 'window is not defined' in Next.js? It means browser code is running on the server. Fix it in 2 minutes with useEffect, typeof window guard, or dynamic import with ssr:false.
Fix Cursor Context Window Exceeded Error (2026)
Cursor showing 'Context Window Exceeded'? Here's the exact fix: start a new thread, add .cursorignore, and use @File references. Clears in 2 minutes.
.cursorrules Deprecated in Cursor? What Replaced It (2026)
.cursorrules is deprecated in recent Cursor versions. Learn what replaced it (Project Rules in .cursor/rules/), whether your existing .cursorrules still works, and how to migrate.
Fix Cursor Shadow Workspace 100% CPU Usage (2026)
Cursor Shadow Workspace pegging your CPU at 100%? Disable it in Settings in 30 seconds. Here's exactly where the toggle is and why it happens.
How to Use 'use client' Correctly Without Breaking Next.js SEO
Is 'use client' hurting your SEO? Learn the 'Leaf Component' strategy to keep your Next.js pages static and high-ranking while still adding interactivity.
Fixing Radix UI Dependency Conflicts in Shadcn (2026)
Conflicting Radix UI versions breaking your Shadcn components? Learn how to use npm overrides, clean your lockfile, and fix peer dependency errors in your UI library.
Fix: Shadcn Select Dropdown Hidden or Behind Other Elements
Shadcn Select dropdown not showing up? Learn how to fix z-index conflicts and properly use Portals to break through CSS stacking contexts in Tailwind.
Fix Supabase Connection Refused + ECR Images Blocked (2026)
Supabase connection refused? Fix it in minutes: wrong connection string, missing SSL mode, and Docker network issues all covered with exact commands.
Fix Supabase Duplicate Key Unique Constraint Error (2026)
Supabase unique constraint error? Fix 'duplicate key value' with upsert, set onConflict for multiple columns with comma-separated strings, and prevent race conditions.
Stop Cursor AI from Writing Python in Your JavaScript (2025 Guide)
Is Cursor AI hallucinating the wrong programming language? Learn how to stop 'Language Drift' and keep your AI focused on the correct syntax for your project.
How to Fix Cursor Composer 'Connection Failed' (2025 Guide)
Cursor Composer connection failed? This guide covers API rate limits, network interference, session timeouts, and the 10-minute fix for AI editor connectivity issues.
Stop "Lazy AI" Comments and Placeholders in Cursor
Tired of the AI returning '// ... rest of code' instead of the full file? Learn how to fix 'Lazy AI' in Cursor using specific prompts, .cursorrules, and scoped edits.
What to Do When Cursor AI is Stuck on "Thinking..."
Fix the 'Thinking...' loop in Cursor AI. Learn how to debug model timeouts, clear oversized context, and reset your AI flow when the spinner never stops.
Fix: params are undefined in Next.js App Router Server Component
params undefined in your Next.js server component? Learn how to handle the async breaking change in Next.js 15 and properly await your dynamic route data.
Fix: 'NextRouter was not mounted' in Next.js App Directory
Getting the 'NextRouter was not mounted' error? Learn why next/router fails in the App Router and how to correctly use next/navigation for Next.js 14 and 15.
How to Pass Data from Server to Client in Next.js
Master the data bridge in Next.js App Router. Learn how to pass data from Server Components to Client Components using props and composition without hydration errors.
Fix "You Are Importing a Component That Needs 'use client'" in Next.js
Resolve the Next.js boundary error. Learn how to fix 'You are importing a component that needs use client' by understanding the Server vs. Client component model.
Fix Supabase 'Auth Session Missing' on Page Refresh (Next.js)
Supabase signing you out on refresh? Learn how to fix 'Auth session missing' by properly configuring Middleware and cookie-based persistence in Next.js App Router.
Fix: Supabase Realtime Subscription Not Receiving Updates
Supabase Realtime not working? Learn how to fix 'no updates received' by enabling replication, auditing RLS, and debugging your WebSocket connection.
Fix: 'RLS policy violates row security' in Supabase (2025)
Supabase RLS error? Learn how to fix 'RLS policy violates row security' by solving infinite recursion and properly using auth.uid() in your Postgres policies.
Fix: Tailwind CSS Classes Not Applying in Shadcn UI (2026)
Tailwind classes not applying to Shadcn? 90% of cases it's a missing content path in tailwind.config.js. Exact fix with before/after config.
Fix: Tailwind @layers Not Working in Next.js globals.css (2025)
Tailwind @layer base or utilities not applying? Learn how to fix CSS layer mismatches by auditing your import order and Next.js CSS injection points.
How to Fix '403 Forbidden' on Vercel Hosted Images (2026)
Vercel returning 403 on hosted images? Missing remotePatterns in next.config.js is the culprit. Exact config fix — works for S3, Cloudinary, and custom domains.
Fixing 504 Gateway Timeout on Vercel Serverless Functions
Vercel 504 error? Learn how to fix 'Gateway Timeout' by optimizing slow database queries, handling external API latency, and managing Vercel's execution limits.
Fix: Environment Variable 'Undefined' on Vercel (Next.js Guide)
Vercel environment variables not working? Learn the difference between build-time and runtime vars, the NEXT_PUBLIC prefix, and how to fix undefined variables in production.
Fix: npm install failing due to peer dependency conflicts (Vercel)
Vercel build failed with ERESOLVE? Learn how to fix peer dependency conflicts by using .npmrc, legacy-peer-deps, and auditing your dependency tree.
Shadcn UI 'Component Not Found' After Installation - Fixed (2025 Guide)
Shadcn component not found after install? This guide covers path alias fixes, components.json configuration, TypeScript mapping errors, and when to escalate beyond DIY debugging.
Fix 'Hydration Failed Because the Initial UI Does Not Match' in Next.js 14 (2025 Guide)
Next.js hydration failed error? This comprehensive guide covers 8 root causes, 5 quick fixes, systematic debugging workflow, and when AI tools can't see the invisible wall between server and client.
How to Fix Cursor AI 'Apply' Button Not Updating File (2025 Guide)
Cursor AI apply button not working? This comprehensive guide covers 6 quick fixes, root cause analysis, and when to escalate beyond DIY debugging.
Fix Vercel Build Error 'Command Failed with Exit Code 1' (2026 Complete Guide)
Vercel build failed with exit code 1? This comprehensive guide covers 7 quick fixes, build log analysis, dependency debugging, and when to escalate beyond DIY troubleshooting.
10 Game-Changing Ways AI Can Debug Your Code in Seconds (2025)
Discover how to debug code with AI using the best automated debugging tools in 2025. Learn 10 proven ways AI can fix code errors, generate tests automatically, catch security vulnerabilities, and optimize performance—helping developers complete debugging tasks 55% faster than traditional methods.
Prevent Cursor From Deleting Your Entire File When Updating Code
Stop Cursor AI from replacing your whole file with 'Rest of code here...' placeholders. Learn the correct way to scope your AI edits using selections.
Fix "Prop className did not match" Error in Next.js & Tailwind
Resolve the 'Prop className did not match' warning in Next.js. Understand how CSS-in-JS and conditional classes cause server/client mismatches and how to fix them.
Fix "Text Content Does Not Match Server-Rendered HTML" in Next.js
Solve the dreaded hydration mismatch error in Next.js. Learn why server HTML differs from client renders and how to fix it with useEffect, suppressHydrationWarning, and proper nesting.
Fix "npm install" Peer Dependency Conflicts (ERESOLVE Error)
Solve the 'ERESOLVE unable to resolve dependency tree' error in npm. Learn when to use --legacy-peer-deps and how to fix version conflicts safely.
Handling Supabase "JWT Expired" Errors in Next.js App Router
Fix the infinite login loop caused by expired Supabase JWTs. Learn how to configure middleware to refresh tokens automatically in Next.js App Router.
How to Center a Div in Tailwind CSS (The Definitive Guide)
Stop guessing with Flexbox. Learn the 3 foolproof ways to center a div in Tailwind CSS: Flex, Grid, and Absolute positioning. Copy-paste solutions included.
How to Ignore TypeScript Errors During Vercel Build
Deploy your Next.js app to Vercel even with TypeScript errors. Learn how to configure next.config.js to ignore build failures when you need to ship fast.
The Ultimate Guide to Coding Homework Help: Expert Solutions for Junior Developers
Stuck on code? Don't panic. Our expert guide covers Python, Java, and JS homework strategies, debugging tips, and how to get ethical coding help from FlowQL.
5 Professional Debugging Techniques That Will Save Junior Developers Hours
Stop using print statements. We reveal 5 professional debugging techniques—from binary search to conditional breakpoints—that will cut your troubleshooting time in half.
Step-by-Step Python Debugging: The Visual Guide for Junior Developers (2025)
Stop guessing with print statements. Master the art of Python debugging in VS Code and PyCharm with our step-by-step visual guide and downloadable cheat sheets.
What's Wrong With My Code? A Troubleshooting Guide for Junior Developers
Staring at a red error message? Don't panic. This 5-step guide helps junior developers diagnose syntax, logic, and runtime errors fast. Plus: When to ask FlowQL for help.