Invalid Compact JWS

jose (JavaScript) — JWSInvalid, code ERR_JWS_INVALID

What it means

jose could not split your input into the three dot-separated segments of compact JWS serialization (header.payload.signature). The string you passed is structurally not a signed token; nothing cryptographic was attempted. It is jose's equivalent of jsonwebtoken's "jwt malformed" — and like that error, it means the problem is upstream of the JWT library, in whatever produced or transported the string.

Why it happens

• Prefix, quotes or whitespace around the token

  common

  "Bearer " prefixes, JSON quotes from a copied config value, or a trailing newline all break the three-segment structure. The token itself may be fine — the string around it is not.

• The variable does not hold a token

  common

  undefined coerced to "undefined", an empty string from a missing cookie, or an opaque (non-JWT) OAuth access token — none of these have JWS structure. The failure is upstream of jose.

• A JWE handed to a JWS API

  occasional

  Encrypted tokens (JWE) have five segments, not three. If your issuer encrypts tokens, jwtVerify/compactVerify will reject them here — decryption (jwtDecrypt) is the right entry point, followed by verifying the nested JWS if present.

How to fix it

1. 1.

   Sanitize and segment-check the input

   Trim, strip the scheme, and assert the segment count before calling jose — you get precise app-level errors instead of a generic parse failure.

   const token = raw.replace(/^Bearer\s+/i, "").trim();
   const segments = token.split(".").length;
   if (segments !== 3) throw new Error(`expected JWS (3 segments), got ${segments}`);

2. 2.

   Route JWE tokens to decryption

   If you count five segments, the token is encrypted. Use jwtDecrypt with the recipient's private key instead of jwtVerify.

   import { jwtDecrypt } from "jose";
   
   const { payload } = await jwtDecrypt(token, privateKey); // 5-segment JWE

3. 3.

   Trace where the string was built

   If a sanitized value still fails, log its length and first characters at every hop — client, gateway, storage, handler. A signed JWT's first segment is base64url JSON, so real tokens start with "eyJ" (the encoding of '{"'); the hop where that stops being true is where the corruption happens.

   console.log(token.length, JSON.stringify(token.slice(0, 12)));
   // healthy: 300+ 'eyJhbGciOiJF'

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