memory: performance, init signal safety, and trusting the harness

.claude/memory/schos-bootcheck-trust.md

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+---
+name: schos-bootcheck-trust
+description: bootcheck silently stopped running and five of seven modes asserted nothing; how to tell a real pass from a script that died
+metadata: 
+  node_type: memory
+  originSessionId: 9d8a2aef-bcf0-47a0-96c6-f706efab4a95
+  modified: 2026-08-09T13:55:00.546Z
+---
+
+**A green run is only green if you counted the checks.** On 2026-08-09 the
+bootcheck suite was reported passing seven times when it had not executed at
+all, and separately when five of its seven modes asserted nothing whatsoever.
+
+**Why:** `bootcheck.ps1` had `[string]$Qemu = (Find-Qemu)` as a param default.
+PowerShell binds parameter defaults *before* any function in the script body is
+defined, so it died on its first line with "Find-Qemu is not recognized" —
+text containing neither `FAIL` nor `Exception`, which were the two words being
+grepped for. Empty output was read as success. Resolve after the param block:
+`if (-not $Qemu) { $Qemu = Find-Qemu }`.
+
+**And:** an earlier index-based edit (`s[:a] + inner + s[c:]`) that removed the
+obsolete `-SchFS` block also deleted the `Expect` blocks for `-Tty`, `-Usb`,
+`-Sock`, `-Ps` and `-Evdev`. Those modes still booted, still printed, and still
+exited 0 — asserting nothing. It happened before `git init`, so no commit ever
+had them; they were reconstructed from failure text quoted earlier in the
+transcript.
+
+**How to check a run is real:**
+
+```sh
+grep -c '\[ok\]'            # must be non-zero, and roughly what you expect
+grep -c 'boot check passed'
+```
+
+Counting `FAIL` alone cannot distinguish "passed" from "never ran". Expected
+counts as of 2026-08-09: base 23, Tty 47, Ps 28, Sock 60, Fb 32, Usb 27,
+Evdev 25 — Tty and Sock include `[ok]` lines printed by the guest programs
+themselves.
+
+**Never pipe a long bootcheck through `head`.** It closes the pipe, kills the
+script partway, and looks like a hang. Redirect to a file and grep the file.
+
+**Why:** the general lesson is that absence of failure output is not evidence
+of success. Both of these produced clean-looking runs while testing nothing.
+
+**How to apply:** after any change to the harness itself, verify the check
+count, not just the absence of FAIL.