Cursor
auth
JWT Signature Invalid After Cursor Code Generation
JWT tokens generated before Cursor's refactoring are now rejected with signature verification errors. The application validates incoming JWTs but now fails on all tokens, including valid ones.
This typically occurs when the JWT secret key configuration changes or the verification algorithm is modified during code generation.
Error Messages You Might See
JsonWebTokenError: invalid signature
TokenExpiredError: jwt expired
invalid token
ERR_JWT_CLAIM_VALIDATION_FAILED
Common Causes
- JWT secret key was moved or regenerated during code organization
- Algorithm changed (HS256 vs RS256) without updating verification logic
- Secret key not trimmed, whitespace causing mismatch
- Buffer encoding changed (utf8 vs base64)
- Clock skew tolerance removed from token verification
How to Fix It
Verify JWT_SECRET environment variable is identical across before/after. Check algorithm consistency in sign() and verify() calls. Ensure no string trimming/encoding changes. Add clock skew tolerance: { clockTimestamp: Math.floor(Date.now() / 1000), clockTolerance: 10 }
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Get HelpFrequently Asked Questions
Can I rotate JWT secrets?
Yes, but implement gradual rotation with a key version. Accept both old and new keys during transition period.
Why is my HS256 token failing?
Ensure secret is a string, not an object. Use crypto.createHmac('sha256', secret) or jwt.verify with matching algorithm.