1# Gotchas
2 
3## Functions Not Running
4 
5**Problem**: Function endpoints return 404 or don't execute  
6**Causes**: `_routes.json` excludes path; wrong file extension (`.jsx`/`.tsx`); Functions dir not at output root  
7**Solution**: Check `_routes.json`, rename to `.ts`/`.js`, verify build output structure
8 
9## 404 on Static Assets
10 
11**Problem**: Static files not serving  
12**Causes**: Build output dir misconfigured; Functions catching requests; Advanced mode missing `env.ASSETS.fetch()`  
13**Solution**: Verify output dir, add exclusions to `_routes.json`, call `env.ASSETS.fetch()` in `_worker.js`
14 
15## Bindings Not Working
16 
17**Problem**: `env.BINDING` undefined or errors  
18**Causes**: wrangler.jsonc syntax error; wrong binding IDs; missing `.dev.vars`; out-of-sync types  
19**Solution**: Validate config, verify IDs, create `.dev.vars`, run `npx wrangler types`
20 
21## Build Failures
22 
23**Problem**: Deployment fails during build  
24**Causes**: Wrong build command/output dir; Node version incompatibility; missing env vars; 20min timeout; OOM  
25**Solution**: Check Dashboard → Deployments → Build log; verify settings; add `.nvmrc`; optimize build
26 
27## Middleware Not Running
28 
29**Problem**: Middleware doesn't execute  
30**Causes**: Wrong filename (not `_middleware.ts`); missing `onRequest` export; didn't call `next()`  
31**Solution**: Rename file with underscore prefix; export handler; call `next()` or return Response
32 
33## Headers/Redirects Not Working
34 
35**Problem**: `_headers` or `_redirects` not applying  
36**Causes**: Only work for static assets; Functions override; syntax errors; exceeded limits  
37**Solution**: Set headers in Response object for Functions; verify syntax; check limits (100 headers, 2,100 redirects)
38 
39## TypeScript Errors
40 
41**Problem**: Type errors in Functions code  
42**Causes**: Types not generated; Env interface doesn't match wrangler.jsonc  
43**Solution**: Run `npx wrangler types --path='./functions/types.d.ts'`; update Env interface
44 
45## Local Dev Issues
46 
47**Problem**: Dev server errors or bindings don't work  
48**Causes**: Port conflict; bindings not passed; local vs HTTPS differences  
49**Solution**: Use `--port=3000`; pass bindings via CLI or wrangler.jsonc; account for HTTP/HTTPS differences
50 
51## Performance Issues
52 
53**Problem**: Slow responses or CPU limit errors  
54**Causes**: Functions invoked for static assets; cold starts; 10ms CPU limit (free) / 30s default (paid); large bundle  
55**Solution**: Exclude static via `_routes.json`; optimize hot paths; keep bundle < 1MB
56 
57## Framework-Specific
58 
59### ⚠️ Deprecated Frameworks
60 
61**Next.js**: Official adapter (`@cloudflare/next-on-pages`) **deprecated** and unmaintained.
62- **Problem**: No updates since 2024; incompatible with Next.js 15+; missing App Router features
63- **Cause**: Cloudflare discontinued official support; community fork exists but limited
64- **Solutions**:
65  1. **Recommended**: Use Vercel (official Next.js host)
66  2. **Advanced**: Self-host on Workers using custom adapter (complex, unsupported)
67  3. **Migration**: Switch to SvelteKit/Nuxt (similar DX, full Pages support)
68 
69**Remix**: Official adapter (`@remix-run/cloudflare-pages`) **deprecated**.
70- **Problem**: No maintenance from Remix team; compatibility issues with Remix v2+
71- **Cause**: Remix team deprecated all framework adapters
72- **Solutions**:
73  1. **Recommended**: Migrate to SvelteKit (similar file-based routing, better DX)
74  2. **Alternative**: Use Astro (static-first with optional SSR)
75  3. **Workaround**: Continue using deprecated adapter (no future support)
76 
77### ✅ Supported Frameworks
78 
79**SvelteKit**:
80- Use `@sveltejs/adapter-cloudflare`
81- Access bindings via `platform.env` in server load functions
82- Set `platform: 'cloudflare'` in `svelte.config.js`
83 
84**Astro**:
85- Built-in Cloudflare adapter
86- Access bindings via `Astro.locals.runtime.env`
87 
88**Nuxt**:
89- Set `nitro.preset: 'cloudflare-pages'` in `nuxt.config.ts`
90- Access bindings via `event.context.cloudflare.env`
91 
92**Qwik, Solid Start**:
93- Built-in or official Cloudflare adapters available
94- Check respective framework docs for binding access
95 
96## Debugging
97 
98```typescript
99// Log request details
100console.log('Request:', { method: request.method, url: request.url });
101console.log('Env:', Object.keys(env));
102console.log('Params:', params);
103```
104 
105**View logs**: `npx wrangler pages deployment tail --project-name=my-project`
106 
107## Smart Placement Issues
108 
109### Increased Cold Start Latency
110 
111**Problem**: First requests slower after enabling Smart Placement  
112**Cause**: Initial optimization period while system learns traffic patterns  
113**Solution**: Expected behavior during first 24-48 hours; monitor latency trends over time
114 
115### Inconsistent Response Times
116 
117**Problem**: Latency varies significantly across requests during initial deployment  
118**Cause**: Smart Placement testing different execution locations to find optimal placement  
119**Solution**: Normal during learning phase; stabilizes after traffic patterns emerge (1-2 days)
120 
121### No Performance Improvement
122 
123**Problem**: Smart Placement enabled but no latency reduction observed  
124**Cause**: Traffic evenly distributed globally, or no data locality constraints  
125**Solution**: Smart Placement most effective with centralized data (D1/DO) or regional traffic; disable if no benefit
126 
127## Remote Bindings Issues
128 
129### Accidentally Modified Production Data
130 
131**Problem**: Local dev with `--remote` altered production database/KV  
132**Cause**: Remote bindings connect directly to production resources; writes are real  
133**Solution**: 
134- Use `--remote` only for read-heavy debugging
135- Create separate preview environments for testing
136- Never use `--remote` for write operations during development
137 
138### Remote Binding Auth Errors
139 
140**Problem**: `npx wrangler pages dev --remote` fails with "Unauthorized" or auth error  
141**Cause**: Not logged in, session expired, or insufficient account permissions  
142**Solution**: 
1431. Run `npx wrangler login` to re-authenticate
1442. Verify account has access to project and bindings
1453. Check binding IDs match production configuration
146 
147### Slow Local Dev with Remote Bindings
148 
149**Problem**: Local dev server slow when using `--remote`  
150**Cause**: Every request makes network calls to production bindings  
151**Solution**: Use local bindings for development; reserve `--remote` for final validation
152 
153## Common Errors
154 
155### "Module not found"
156**Cause**: Dependencies not bundled or build output incorrect  
157**Solution**: Check build output directory, ensure dependencies bundled
158 
159### "Binding not found"
160**Cause**: Binding not configured or types out of sync  
161**Solution**: Verify wrangler.jsonc, run `npx wrangler types`
162 
163### "Request exceeded CPU limit"
164**Cause**: Code execution too slow or heavy compute  
165**Solution**: Optimize hot paths, upgrade to Workers Paid
166 
167### "Script too large"
168**Cause**: Bundle size exceeds limit  
169**Solution**: Tree-shake, use dynamic imports, code-split
170 
171### "Too many subrequests"
172**Cause**: Exceeded 50 subrequest limit  
173**Solution**: Batch or reduce fetch calls
174 
175### "KV key not found"
176**Cause**: Key doesn't exist or wrong namespace  
177**Solution**: Check namespace matches environment
178 
179### "D1 error"
180**Cause**: Wrong database_id or missing migrations  
181**Solution**: Verify config, run `wrangler d1 migrations list`
182 
183## Limits Reference (Jan 2026)
184 
185| Resource | Free | Paid |
186|----------|------|------|
187| Functions Requests | 100k/day | Unlimited |
188| CPU Time | 10ms/req | 30s default, 5min max |
189| Memory | 128MB | 128MB |
190| Script Size | 1MB | 10MB |
191| Subrequests | 50/req | 10,000/req |
192| Deployments | 500/month | 5,000/month |
193 
194**Tip**: Hitting CPU limit? Optimize hot paths or upgrade to Workers Paid plan.
195 
196[Full limits](https://developers.cloudflare.com/pages/platform/limits/)
197 
198## Getting Help
199 
2001. Check [Pages Docs](https://developers.cloudflare.com/pages/)
2012. Search [Discord #functions](https://discord.com/channels/595317990191398933/910978223968518144)
2023. Review [Workers Examples](https://developers.cloudflare.com/workers/examples/)
2034. Check framework-specific docs/adapters
204