SERVER_ERROR: Error: hex string expected, got undefined

So i started migrating from clerk to better auth. the docs are amazing. i love everything about better auth. so i run the migration script. added the accounts and done everything. then i tried logging in from my expo app and got the following error

SERVER_ERROR: Error: hex string expected, got undefined

at hexToBytes (file:///Users/mac/Desktop/work/GoGain/GoGain-backend/node_modules/@noble/hashes/esm/utils.js:141:15)
at Object.verifyPassword [as verify] (file:///Users/mac/Desktop/work/GoGain/GoGain-backend/node_modules/better-auth/dist/shared/better-auth.OT3XFeFk.mjs:45:39)
at async file:///Users/mac/Desktop/work/GoGain/GoGain-backend/node_modules/better-auth/dist/shared/better-auth.cM0Fc3LZ.mjs:1738:27
at async internalHandler (file:///Users/mac/Desktop/work/GoGain/GoGain-backend/node_modules/better-call/dist/index.js:576:22)
at async api.<computed> (file:///Users/mac/Desktop/work/GoGain/GoGain-backend/node_modules/better-auth/dist/api/index.mjs:516:22)
at async processRequest (file:///Users/mac/Desktop/work/GoGain/GoGain-backend/node_modules/better-call/dist/index.js:4881:24)
at async handler (file:///Users/mac/Desktop/work/GoGain/GoGain-backend/node_modules/better-call/dist/index.js:4901:19)
at async file:///Users/mac/Desktop/work/GoGain/GoGain-backend/node_modules/better-call/dist/node.js:138:22

here's an example of one line of password from my csv

user_2q8MgHHfYJitwcfLo7MAe2X0rLU,zak,zak,,guest@gmail.com,,guest@gmail.com,,,,,$2a$10$0VHVVjA5W4UaMA94WjahseL4NYHseXRQS8z6fC1/4hgUij.QUCiOu,bcrypt

rest assured these are dev dummy users nothing critical that's why i shared that. can anyone help? why is that happening?

Jerematix•8/6/25, 3:42 PM

Hi @zakisb97 I'm currently facing the same issue, locally with dev server it works, but when building and deploying to server it doesn't work. At least for my issue, I found that it seems to have something to do with crypto operations part, when I have a wrong email, it gets blocked before and I get a 401. I'm running it on a docker image with bun. For me the error looks like this:

SERVER_ERROR: Error: hex string expected, got undefined

at <anonymous> (.next/server/chunks/249.js:1:45004)
at <anonymous> (.next/server/chunks/249.js:1:45416)
at processTicksAndRejections (null)

Have you found a fix or any other information so far?

zakisb97OP•8/14/25, 1:12 AM

hello

zakisb97OP•8/14/25, 1:13 AM

sorry for the late reponse

zakisb97OP•8/14/25, 1:13 AM

yes i found the error and the problem

zakisb97OP•8/14/25, 1:13 AM

i just had to add this

zakisb97OP•8/14/25, 1:13 AM

 emailAndPassword: {
    enabled: true, // Enable authentication using email and password.
    // requireEmailAlreadyVerified: true, // guarantees “step 2” happened
    password: {
      hash: async (password) => {
        return await bcrypt.hash(password, 10);
      },
      verify: async ({ password, hash }) => {
        return await bcrypt.compare(password, hash);
      },
    },
  },

 emailAndPassword: {
    enabled: true, // Enable authentication using email and password.
    // requireEmailAlreadyVerified: true, // guarantees “step 2” happened
    password: {
      hash: async (password) => {
        return await bcrypt.hash(password, 10);
      },
      verify: async ({ password, hash }) => {
        return await bcrypt.compare(password, hash);
      },
    },
  },

to my auth config ( the password object)

emailAndPassword: { enabled: true, // Enable authentication using email and password. // requireEmailAlreadyVerified: true, // guarantees “step 2” happened password: { hash: async (password) => { return await bcrypt.hash(password, 10); }, verify: async ({ password, hash }) => { return await bcrypt.compare(password, hash); }, }, },

SERVER_ERROR: Error: hex string expected, got undefined

SERVER_ERROR: Error: hex string expected, got undefined

SERVER_ERROR: Error: hex string expected, got undefined

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