Errors

Code	Meaning
1	Malformed input or an unknown instruction discriminator
1001	A Signer account was not signed
1002	A mutable account was not writable
1003	Owner check failed
1004	Account size does not match the layout
1005	Account discriminator mismatch
1006	Missing account or an internal bounds failure
1007	A CPI failed
1008	Account is not the expected PDA
1009	Checked arithmetic overflowed
1010	Division by zero, or an illegal shift count
1011	Unit-enum byte is not a declared variant
1012	.value while an option tag is clear
1013	FixedString length past its reserved bytes
1014	An account constraint failed

Program errors are 6000 + index in the @error class. The integer written beside the name is documentation. expect_error("Unauthorized") uses the name. Logs include (file.py:line).