Same-image Bash PID1 comparison — userspace prompt, no command receipt

2026-10-03 UTC. Root reserved board/UART for one trial with reviewed source 473d4ab3 and CI integration bfce9f8b8e3a162074190cae37e946e6b6336df1, branch integrate/mainline-probe-path, worktree /home/jadams/tmp/k230-mainline-probe-integration, protected recovery base 1088e3ee. Owned paths are this packet and the mainline task progress note. No new build/transfer: the exact staged brmp bundle and full closure were reused.

Host proof records independent review, 14 focused and 214 existing tests, actual archived common-loader inspection and one-variable arguments. CI passed the ordinary, minimal and new focused gates. Fresh protected normal preflight passed exact identities, eight unchanged files and three services; its actual helper first asserts registration absence including dangling symlink. Five loads/CRCs and exact printed arguments passed. Exactly one received kernel command line matches expected marker-free/async=0/three controls plus only rdinit=/bin/sh.

python3 tools/mainline-drm-initrd-shell-trial.py \
  --mode minimal --same-image-shell-pid1 \
  --bundle /nix/store/brmp1qf9cz65yciazabc8yg5j39nn643-k230-mainline-drm-trial-boot-files \
  --manifest ~/tmp/k230-mainline-shell-pid1-board/candidate-manifest.json \
  --normal-report ~/tmp/k230-mainline-shell-pid1-board/normal-report.json \
  --log ~/tmp/k230-mainline-shell-pid1-board/trial.private.log \
  --result ~/tmp/k230-mainline-shell-pid1-board/result.private.json

Exit 2 at reception. The controller received a fresh Linux 7.3.0-rc5 banner, Run /bin/sh as init process, then the primary sh-5.3# prompt. Its readiness gate passed. Bash/common-loader userspace startup therefore has positive physical output evidence, beyond the earlier kernel exec label. The bounded receipt loop exhausted eight fresh builtin attempts at one second per attempt with zero complete receipt records or command echoes. Outgoing write bytes are not separately logged; loop completion establishes the attempt bound, while the immutable raw capture preserves received output.

No /bin/true, proc mount, uptime, PID1/root/kernel/cmdline/boot guard or reboot was attempted. The controller released UART with no input after this unknown result. Bash startup is distinct from qualified command reception, full identity guard, ordinary NixOS root or automatic protected return. A newly reviewed private camera frame appears dark, with glare/focus/perspective limits. It does not contradict separate serial evidence of Bash startup. Exact artifacts and fixed facts/raw byte/hash/timestamps are in result.json; raw UART and camera remain private.

Recovery and next discriminator

A new user reset after this trial restored the protected normal system. The prepared checker completed successfully (exit 0):

python3 ~/tmp/k230-mainline-shell-pid1-board/reset-normal-check.py

It sent CR only until a fresh normal prompt, then proved a different boot identity, exact protected system/profile/kernel/init, all eight unchanged boot files, three active services and registration absence. The Home IPC command completed with exit 0; a new private camera frame shows normal Home icons, clock and background, with glare/focus/perspective limits. The fixed recovery receipt preserves raw hash/timestamps and those facts without boot UUIDs or secret-bearing console text. Board/UART and camera are released. This manual reset is separate from automatic return, which remains UNVERIFIED, and supplies no mainline panel/glass acceptance.

The missing receipt narrows the next investigation to serial RX/interrupt/ TTY/task progress after observed userspace startup, without identifying a cause. The host-only source/DT receipt compares eight complete source files and thirteen targeted properties against the earlier candidate that passed minimal receipt. Those files/properties match; full DTBs, configs, binaries and runtime state are not claimed equivalent. This result does not identify a source regression. A finite independent reporter should distinguish cached driver RX/error counts, actual mapped UART and RISC-V timer IRQ counters, and scheduling/time progress without requiring Bash input. TTY polling flushes work and queued-input ioctl takes a semaphore, so neither is a passive first probe. Reporter output or silence must retain explicit limits and never stand in for recovery. Kernel observer implementation/build and another qualified operator trial remain future gates. No ordinary-root/panel/glass/production acceptance or archive follows; task 5b.5 stays open.