# Checker development notes

Two local checker problems were found and resolved before claiming stored
verification. Neither changed the generator's values or selection.

1. Sage RealBall exposes `accuracy()`, measured in relative bits, rather than
   the `rel_accuracy_bits()` spelling used in the first checker. The initial
   known-answer control raised AttributeError. Reading the bound method's
   documentation confirmed the API and its meaning; pi at 600 bits reports
   599 bits. The corrected checks retained at least 390 bits for generated
   entries. `probe_accuracy.py` records that probe.
2. The API canonicalized submitted flat rows into nested bare scalar leaves.
   The first read-back walker skipped those strings and failed its 128-row
   enumeration assertion. The corrected parser reads them at the declared
   parameter depth. The public values and ordering were unchanged. The lesson
   artifact describes the general contributor-facing issue.

The site audit's field-selector finding is evaluated separately in
`audit-disposition.md`. It is not a failed numerical identity.