# B6P P9 preflight — STOP before the first persistent write (cache). Nothing has been written.
(Paths relative to ~/doc/modem/jz08-aurora on 480s; SHA256SUMS in b6p/.)

1. Proven B6N files: b6j/aurora-modem aa9e9aa2 + b6j/n.conf aa9e27af (b6j-in6.tar d5b551b5; B6N N1 6/6, N2 3/3).
2. Production layout (initramfs overlay): /usr/sbin/aurora-modem 6e922dec (B6N controller minus diagnostics, diff-b6n-vs-b6p.diff),
   /etc/aurora/modem.conf 6ffb206e (APN/USER/PASSWORD/AUTH/IP_TYPE/REG_TIMEOUT=600/ROUTES), state /run/aurora-modem.
3. Service: /etc/init.d/aurora-modem 533f47ea (start|stop|status; no OpenRC by decision), started once by /init 9d6694fb
   after EMMC_RO_OK + B1_OK (/init diff = 2 comment/banner lines + 2-line hook); kill switch cmdline aurora.modem=off.
4. Initramfs manifest diff (out/manifest-diff.txt): golden 472 entries untouched (exact 250bf8ee bytes) + overlay member 651fc826:
   REPLACES /init; NEW /usr/sbin/aurora-modem, /etc/init.d/aurora-modem, /etc/aurora/modem.conf, dirs /etc/aurora, /etc/init.d.
5. RAM candidate: b6p/out/aurora-mm1-b6p.img 20 617 216 B 18a25e399c96afaf22e8e84e0d7c8fef18518bb427c9a36440ad6435f71b9090
   (initramfs-b6p.cpio.gz 11 955 862 B 8dcb61c8…; kernel/DTB/cmdline/header == golden 38c960ef, writer reproduces golden bit-for-bit).
6. RAM tests (fastboot boot via RESET-held power-on, lk1st autoboot): P6 + P7 = 3/3 fresh boots PASS, autostart at ~10 s with 1970 clock,
   registration 3.6 / 10.1 / 6.9 s, START OK 62.8 / 77.9 / 75.6 s, DNS/ICMP/HTTP PASS, P6 3/3 disconnect→reconnect without MSS restart,
   service stop rc=0 each boot, NV unchanged, eMMC writes 0, dmesg errors 0, NCM ok, no MSS retry. Logs logs/b6p/{p6,p7b2,p7b3}.
7. Cache image: b6p/cache-extlinux-b6p.img 134 217 728 B 9fea693a436b49ca56aed0857725ecdde8a0071700cf5d23b02dab9d9ff406b7
   (mkfs-cache-b6p.sh = B5b recipe; rebuild identical; the B5b recipe still reproduces 409bbb11 on 480s). ext2 rev1, features filetype sparse_super
   only, 4K, 64 inodes, e2fsck -fn clean. extlinux.conf 391e753b: default/label b6p, linux /Image.gz-dtb (0ff9c802), fdt /aurora-mm1.dtb (a10056c5),
   initrd /initramfs-b6p.cpio.gz (8dcb61c8), append == golden cmdline.
8. lk2nd 23.1 emulator (b5b/emu, real boot.c/extlinux.c/ext2/bio/zlib): harness regression S1 == session 26; S3 B6P: "Trying to boot 'b6p'" →
   boot_linux kernel 4603b02f @+0 (end +0x1680000), DTB a10056c5 @+0x2499000, ramdisk 8dcb61c8 @+0x2699000 (11 955 862), cmdline exact;
   F1–F11 (no conf/kernel/initrd/dtb, garbage/CRLF/no-fdt/no-newline conf, bad gzip, zeroed cache, bad superblock) → all "Reverting to android boot" (emmc1).
   Not emulated (residual): LK hang on corrupt metadata; ASSERT in boot_linux DT; Linux starts but crashes (no fallback).
9. Current cache/backup: live cache (read-only on the board 20:48, P9 run) = 409bbb11 == b5b/cache-extlinux-mm1.img == logs/b5b/W/11-cache-readback.bin.
   Live also: boot e9579f33, aboot 3b8cd266, sbl1 6a661ec9, rpm 5a9b857b, tz 8481892f, hyp 1a963047, recovery 0dfa60a0, modemst1 637a71d1,
   modemst2 9bb10190, fsg b0a3b7e4, fsc 5f70bf18, persist ee48a843 (== A3); eMMC writes 0 (p9-live-sha.txt).
10. Write (after GO only; HW EDL: battery on, D+→GND, plug USB, release; on 480s): `bash b6p/B6P-write.sh`
    = b5b/B5b-write.sh with only NEW/OLD hashes, rollback-image gates and log dir changed: gates (loader 53f19350, candidate 9fea693a, rollback image
    409bbb11, 9008, serial, cache geometry 0x4118c000/0x8000000, GPT == A3, boot == e9579f33, aboot == 3b8cd266, cache == 409bbb11)
    → `edl --loader=<fhprg_peek> w cache b6p/cache-extlinux-b6p.img` (LBA 2133088, 262144 sectors).
11. Readback: `edl r cache logs/b6p/W/11-cache-readback.bin` + `cmp` with the candidate (CACHE_MATCH), then GPT p/b, tzbak, boot, aboot,
    sbl1, rpm, tz, hyp, recovery, modemst1/2, fsg, fsc, persist == A3 and modem, system, userdata == A4pre.
12. Rollback: `bash b6p/B6P-rollback.sh` (HW EDL) → cache := b5b/cache-extlinux-mm1.img 409bbb11 + readback cmp (CACHE_RESTORED_B5B).
    Independent fallback without any write: any extlinux failure → lk1st boots emmc1 from `boot`; RESET-held power-on → fastboot → `fastboot boot` golden.
13. Untouched: boot (emmc1 fallback), aboot, GPT, sbl1, rpm, tz, hyp, recovery, modem, modemst1/2, fsg, fsc, persist, system, userdata. Only `cache`.
Post-write plan (for the GO message): power off fully; cold boot ×N without host → extlinux 'b6p' → autostart → registration → bearer → data.