[BUG]: … Incorrect Padding Error #126

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1. NitinGCJ

   added

   bugSomething isn't workingSomething isn't working

   on May 20, 2025
2. TimPietrusky commented on May 28, 2025

   

   TimPietrusky

   on May 28, 2025

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   @NitinGCJ i have never seen such an error. with the 5.1.0 release of this worker, we enabled debug logs directly from ComfyUI into the logs of the worker. could you please update your endpoint to use the latest version of the worker and then provide the logs in this issue when this problem occurs again?
3. TimPietrusky

   self-assigned this

   on May 28, 2025
4. TimPietruskyRunPod commented on Jun 2, 2026

   

   TimPietruskyRunPod

   on Jun 2, 2026

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   "Incorrect padding" on base64 decode is almost always one of three things:

   1. Truncation on the wire — RunPod's `/run` has a 10 MB body limit and `/runsync` is 20 MB. If your image is large, the response is being cut and the trailing padding (`=`) bytes are missing. Switch to S3 mode (`BUCKET_ENDPOINT_URL=...`) to bypass this.
   2. Client-side string corruption — splitting the base64 across lines, replacing `+` with space (URL decoding), or chopping the trailing `=` characters all produce this error. Decode the exact string the API returned without any transformation.
   3. You're decoding the JSON value including the surrounding quotes — `base64.b64decode("iVBOR...")` is correct; `base64.b64decode('"iVBOR..."')` includes the quotes and fails. Common in shell pipelines.

   Could you share:

   • The first and last 50 characters of the base64 string that failed to decode
   • The image resolution and approximate file size
   • Whether you're using `/run` or `/runsync`

   If it's #1 (oversized payload) the right fix is BUCKET_ENDPOINT_URL — possibly with the upcoming BUCKET_PREFIX from PR #191. If you can confirm the payload size we'll know which.