generate-bls-to-execution-change crops the withdrawal credentials list to 4096 chars

[vbuterin]

The generate-bls-to-execution-change CLI option seems to be cropping the inputted list of withdrawal credentials at 4096 chars. This is preventing using the tool to simultaneously upgrade credentials for more than ~61 validators.

[valefar-on-discord]

Confirmed the issue.

There is a work around if you use the --bls_withdrawal_credentials_list parameter.

[remyroy]

Could this be limitation from other parts of the CLI? From what I'm reading, the Click package we are using for interactive CLI simply uses sys.stdin.readline() for prompt inputs which reads input until a newline without a fixed length restriction from Python or Click.

However, the reported truncation at 4096 characters (or 4095 plus a newline) is a common limitation stemming from the terminal's line buffer in canonical mode, particularly on Linux systems. This is enforced by the kernel's TTY driver, where the maximum line length is typically 4096 characters, including the terminating newline. When this limit is exceeded during input (e.g., typing or pasting a long string before pressing Enter), the excess characters are ignored or truncated, leading to the observed behavior.

As another workaround, you could do multiple batches of generate-bls-to-execution-change where each batch withdrawal credential list is lower than 4096 characters in total.