docs(backlog): B-0834 — installer preserve install log to file (failures + warnings scroll past too fast; 3rd empirical anchor in same physical test session)

docs/BACKLOG.md

@@ -767,6 +767,7 @@ are closed (status: closed in frontmatter)._
 - [ ] **[B-0828](backlog/P2/B-0828-multi-ai-shared-checkout-convention-human-maintainer-surface-plus-always-up-to-date-main-for-society-aaron-2026-05-26.md)** Multi-AI shared-checkout convention — human-maintainer surface + always-up-to-date-with-main for society
 - [ ] **[B-0829](backlog/P2/B-0829-schemas-as-rows-cluster-fork-as-trust-boundary-fsharp-type-providers-from-live-cluster-foundation-for-runme-bcl-ontology-kestrel-aaron-2026-05-26.md)** Schemas-as-rows + cluster-fork-as-trust-boundary + F# type providers from live cluster — foundation layer for Runme BCL ontology capability
 - [ ] **[B-0832](backlog/P2/B-0832-installer-nmtui-wifi-rescan-refresh-button-overlapping-networks-empirical-aaron-2026-05-26-physical-hardware-support-test.md)** installer nmtui WiFi step needs visible rescan/refresh path — empirical from operator's physical hardware-support test 2026-05-26 (20+ overlapping networks; target SSID not initially in scan list) (Aaron 2026-05-26)
+- [ ] **[B-0834](backlog/P2/B-0834-installer-preserve-install-log-to-file-failures-warnings-scrollback-empirical-aaron-2026-05-26.md)** installer must preserve install log to file — failures + warnings scroll past faster than operator can read (empirical from 2026-05-26 physical hardware-support test; gh login not reached) (Aaron 2026-05-26)
 
 ## P3 — convenience / deferred
 

docs/backlog/P2/B-0834-installer-preserve-install-log-to-file-failures-warnings-scrollback-empirical-aaron-2026-05-26.md

@@ -0,0 +1,147 @@
+---
+id: B-0834
+priority: P2
+status: open
+title: installer must preserve install log to file — failures + warnings scroll past faster than operator can read (empirical from 2026-05-26 physical hardware-support test; gh login not reached) (Aaron 2026-05-26)
+effort: S
+ask: aaron 2026-05-26
+created: 2026-05-26
+last_updated: 2026-05-26
+depends_on:
+  - B-0754
+composes_with:
+  - B-0831
+  - B-0832
+  - B-0833
+tags: [installer, first-boot, logging, operator-ux, physical-hardware-support-test, empirical-anchor, scrollback]
+---
+
+## Problem
+
+Empirical from operator's 2026-05-26 physical hardware-support test
+(third empirical-anchor in the same test session after B-0832 nmtui
+WiFi rescan + B-0833 interactive-vs-baked-keys auth tension):
+
+Operator framing: *"i got some failures and warings on install of
+nixos not sure if it matters it scrolled by to faster have gh login
+this is exactly what i'm hoping you can log and test in ci"*
+
+Two observations packed into one report:
+
+1. **Install failures + warnings scrolled past too fast for operator
+   to read** — `zeta-install` / `nixos-install` / underlying
+   nix-build output flows directly to the terminal; under load
+   (parallel derivation builds + parallel disko operations + parallel
+   nixpkgs evaluation), output rate exceeds human reading speed; ANY
+   warnings or recoverable failures get lost in the scroll
+2. **gh login not reached** — install presumably stalled OR failed
+   before reaching the `gh auth login` step in `zeta-install.sh`; the
+   scroll-past-too-fast issue blocks operator's ability to diagnose
+
+The operator's correct framing: *"this is exactly what i'm hoping
+you can log and test in ci"* — B-0831 cascade #6 phase 1 already
+plans to capture full serial console as workflow-artifact. This row
+is the OPERATOR-SIDE analog: preserve the log on the install target
+so operator can review after the fact, BEFORE B-0831 cascade #6
+lands.
+
+## Proposed mitigation
+
+Two layered approaches:
+
+### Approach A — `tee` install output to log file (smallest fix)
+
+Modify `zeta-install.sh` to `tee` all output to a log file in /mnt
+(install target) AND to a log file in /tmp (live ISO):
+
+```bash
+# At top of zeta-install.sh:
+LOG_FILE="${LOG_FILE:-/tmp/zeta-install-$(date -u +%Y%m%dT%H%M%SZ).log}"
+exec > >(tee -a "$LOG_FILE") 2>&1
+```
+
+After install completes (success OR failure), copy the log to:
+
+- `/mnt/var/log/zeta-install.log` (preserved on installed system; available
+  after first boot of installed system)
+- `/tmp/zeta-install-<timestamp>.log` (available on live ISO until
+  reboot; operator can `cat` after `Ctrl-C` to abort + diagnose)
+
+Operator can then:
+
+- During install: `Ctrl-Z` install → background → `tail -f
+  /tmp/zeta-install-*.log | less` (scrollable)
+- After failure: `cat /tmp/zeta-install-*.log | less`
+- After successful install + boot: `journalctl -u zeta-first-boot
+  --boot=-1` OR `cat /var/log/zeta-install.log`
+
+### Approach B — `script` command wraps zeta-install entirely
+
+Use `script(1)` to record the full session (input + output + timing):
+
+```bash
+# Wrapper that records everything:
+script -q /tmp/zeta-install-session.typescript -c '/run/current-system/sw/bin/zeta-install <host>'
+```
+
+This captures even ANSI escape sequences + timing data (replayable
+via `scriptreplay`). Heavier than `tee` but captures more (TUI
+interactions like nmtui screen states).
+
+Approach A is preferred (simpler; smaller code change; sufficient
+for the immediate diagnostic need); Approach B is the upgrade path
+if Approach A misses anything.
+
+## Acceptance
+
+- Install output is `tee`'d to `/tmp/zeta-install-<timestamp>.log` on
+  the live ISO from the moment `zeta-first-boot` fires
+- On install completion (success OR failure), log is copied to
+  `/mnt/var/log/zeta-install.log` (if `/mnt` is mounted at that point)
+- Pre-failure scroll-past failures + warnings are now PRESERVED IN THE
+  LOG FILE; operator can review via `less /tmp/zeta-install-*.log`
+- Log location named in the existing install-banner text so operator
+  sees WHERE the log is BEFORE it scrolls past
+- Empirical re-validation: rerun the physical hardware-support test;
+  if failures recur, operator can `cat` the log and surface specifics
+
+## Composes with
+
+- `full-ai-cluster/usb-nixos-installer/zeta-install.sh` (the script
+  this row modifies)
+- `full-ai-cluster/usb-nixos-installer/zeta-first-boot.sh` (wrapper
+  that calls zeta-install; could set `LOG_FILE` env var)
+- B-0754 (zero-typing first-boot scope; this row extends with
+  preserved-log substrate)
+- B-0831 (CI cascade #6 phase 1 captures full serial console; this row
+  is the OPERATOR-SIDE analog — log preserved on disk so operator can
+  review post-failure, BEFORE B-0831 cascade #6 lands)
+- B-0832 (sibling empirical anchor: nmtui WiFi rescan; same physical
+  test session)
+- B-0833 (sibling empirical anchor: interactive-login vs baked-in-keys
+  CI-test tension; same physical test session — this row's failure
+  blocked reaching the gh-login phase)
+- The 2026-05-26 physical hardware-support test (3rd empirical anchor
+  in the same test session; validates B-0831 reframing of
+  physical-as-hardware-support-test producing empirically-anchored
+  substrate-engineering targets within minutes)
+
+## Substrate-honest framing
+
+Three empirical anchors in one physical hardware-support test session
+(B-0832 + B-0833 + this row B-0834) is STRONG validation of B-0831's
+reframing: physical-test-as-first-class-hardware-compatibility-matrix-
+substrate produces real-world substrate-engineering targets that CI
+emulation cannot reproduce.
+
+The fix is small (tee output to log file) and immediate-value
+(operator can diagnose the install failure that prompted this row,
+once Approach A lands). P2 priority because it's a diagnostic
+enabler, not a hard install blocker.
+
+This row also demonstrates the **operator-side analog** pattern to
+the CI-side B-0831 cascade #6: both substrate-engineering targets
+solve the same fundamental problem (preserve install output for
+later review) at different surfaces (operator-physical-test on real
+hardware vs CI-automated-test in QEMU). Both are valuable; both
+land separately; both compose.