RPC error InstructionError Custom: custom program error: 0x…

Last updated: November 1, 2026

At a glance

Cause

Solana passes the code through without interpreting it: custom program error: 0x1771 means only that a program returned 6001. The same number means different things in different programs, so no universal table exists, and a search for the hex value alone often finds someone else's program. The log line above the failure identifies which program returned it.

Solution

1. Find the program: in the logs, the last Program <id> invoke before failed is the one that returned the code.
2. Convert hex to decimal. 0x1771 is 6001.
3. On Anchor programs, user-defined errors start at 6000, so subtract 6000 to get the index in the errors list of the IDL.
4. Otherwise check the program's source or published error list. Ask for the IDL with the program's own tooling.
5. When the error is a slippage check, rebuild with fresh state or a wider tolerance. Retrying the same bytes returns the same code.

Example

{
  "err": {
    "InstructionError": [
      3,
      {
        "Custom": 6001
      }
    ]
  }
}