# Checklist: Controller A USB write-size specimen qualification

Status: complete
Type: checklist
Updated: 2026-07-28
Next Action: none; retain with the first-specimen qualification evidence
Parent: work/wp/completed/wp-characterize-usb-filex-write-size-durability.md

## Goal

Use Controller A as the first specimen to screen 16/32/64 KiB FileX requests
at 1 MiB, then sustain only passing candidates at 7 MiB. Testing is separate
from build and deployment.

## Checklist

- [x] Confirm exact deployed S-record hash and Controller A SD CID.
- [x] Confirm the USB specimen identity and clean baseline; WAV fixtures were intentionally excluded as unrelated to this deterministic diagnostic.
- [x] Run the 1 MiB tier once; do not remove media while it is active.
- [x] Capture all three controller result records.
- [x] Move media to Pi and verify exact sizes, identical hashes, and clean FAT.
- [x] Preserve the controlled specimen and existing 1 MiB outputs for the sustained tier.
- [x] Run the 7 MiB tier only after all candidates passed 1 MiB.
- [x] Capture controller results and repeat physical Pi verification.
- [x] Compare controller write time, call counts, total time, and physical persistence.
- [x] Select 32 KiB as the conservative successor candidate with explicit margin; production adoption remains separately gated.

## Runtime Closeout

Use this section only when the checklist changes a running system, scheduler, service, or external status surface.

- [x] Diagnostic symbols are readable but no command is active after deployment.
- [x] Controller A normal operation and SD CID remain healthy.
- [x] Exact pre-diagnostic rollback is recorded.
- [x] A-2 is safely unmounted at closeout.

## Verification

Controller Success is provisional. Completion requires physical removal,
host hashes, expected file sizes/content, and full unmounted FAT checks.

Result: passed. See
`work/evidence/controller-a-a2-usb-write-size-qualification-20260728.md`.
