# B10 cache write — preflight (2026-10-04) — reviewed, NOT executed

## Candidate / rollback
- Candidate `b10/b10b3/cache-v4/cache-extlinux-b10b5.img` **c37325156a6f4c013982cf01bcb5b2ddb026b0298e9c3ec0be87f57d693464b8** (134217728 B) =
  B9C + kernel 7.2.7-aurora-b10b5 (v4, FAULT safe clamp) + production DTB e47762d1; no test hooks (B10B5-RESULT.md, production RAM smoke PASS).
- Live cache today: B9C **b9ce13c9** — rollback image `b9/b9c/cache/cache-extlinux-b9c.img` and the B9C write readback `logs/b9/b9c/W/11-cache-readback.bin`
  (both b9ce13c9, checked). The script also saves the live cache read right before the write as `logs/b10/b10b5/W/pre-cache.bin`.

## Scripts (on 480s; b10/b10b5/)
- `B10-write.sh` 295ed53b — 1:1 from `b9/b9c/cache/B9C-write.sh`; changed only: image + NEW_SHA, OLD_SHA = B9C b9ce13c9, rollback/backup paths (B9C),
  **ABOOT_SHA = 15208dbb (lk1st-b9l since B9L-PERSIST; B9C used 3b8cd266)**, log dir `logs/b10/b10b5/W`, rollback hint, final marker.
  Gates (stop at first failure): G0 loader 53f19350 / candidate sha+size / rollback image / B9C readback backup / 9008 present;
  G1 printgpt, serial 0x<SAHARA_SERIAL> or firehose, cache geometry 0x4118c000+0x8000000, GPT primary == A3, boot == e9579f33 (emmc1), aboot == 15208dbb,
  **live cache == b9ce13c9** (= backup); W: `edl w cache` only → readback → cmp == candidate (CACHE_MATCH) else STOP "do NOT reboot; run rollback";
  V: GPT primary/backup, tzbak, boot, aboot, sbl1 rpm tz hyp recovery modemst1 modemst2 fsg fsc persist == A3, modem system userdata == A4pre;
  SHA256SUMS → `B10_CACHE_WRITE_VERIFIED`. Offline G0 check done: loader, candidate, rollback image, backup and all A3/A4pre references OK.
- `B10-rollback.sh` 37e0e165 — 1:1 from B9C-rollback.sh: rollback image hash gate → 9008 gate → `edl w cache` B9C → readback cmp → `CACHE_RESTORED_B9C`.
- `b10-cold-boot.sh K` — observation of the normal power-on (MODE=cold: aborts if fastboot appears = RESET held); RTC class, LTE/Wi-Fi/display/charger snapshot.
Never `edl reset`; never `dd` from Linux.

## Physical sequence — install (verified B9C HW EDL workflow)
Battery is required during EDL (the board does not start from USB alone, NOTES.md:483). Minimum battery handling inside the verified procedure: 2× out/in.
1. Board running; operator: USB OFF (unplug the board's USB cable).
2. Battery OUT (board off), then battery IN — board stays off (no USB). Check the contact sits firmly.
3. Hold D+ to GND, plug USB, release D+ → host shows 05c6:9008. Claude runs `b10/b10b5/B10-write.sh` (≈ 10–15 min incl. verify reads).
4. Only after `B10_CACHE_WRITE_VERIFIED`: USB OFF → battery OUT → wait ≥ 90 s (this is also the class-A condition).
5. Claude starts `b10-cold-boot.sh 1`; operator: battery IN → USB ON, **no RESET, no D+**. Normal power-on → lk1st → lk2nd extlinux → b10b5 from cache.
If step 3 prints a STOP before W: nothing was written → USB OFF, battery out/in, USB ON → B9C boots as before.
If CACHE READBACK MISMATCH: do NOT power off; keep 9008 and run the rollback below immediately.

## Physical sequence — rollback to B9C b9ce13c9 (if needed)
1. Board running (or off): USB OFF → battery OUT → battery IN (board off).
2. D+ to GND, plug USB, release → 9008. Claude runs `b10/b10b5/B10-rollback.sh` → `CACHE_RESTORED_B9C`.
3. USB OFF → battery OUT ≥ 90 s → battery IN → USB ON (no RESET) → B9C boots.

## Not used (recorded only)
- Battery out for the whole EDL → flash → power-off span: impossible (EDL needs the battery).
- `fastboot oem reboot-edl` from lk1st (verified for EDL entry and reads in A3 / S1 / S3 sessions, NOTES.md:530/569/866) would avoid steps 1–2,
  but no cache write was ever done through it → not used.