windows95/.claude/skills/probe-win95/SKILL.md

name, description

name	description
probe-win95	Boot Windows 95 in Electron under Claude's control, without a human clicking anything. Use when testing v86 updates, SMB changes, keyboard input, boot stability, or bisecting regressions.

Probing Windows 95 autonomously

You can run and test the Win95 VM yourself. The harness is already wired up — three pieces:

File	Role
src/renderer/debug-harness.ts	Activated by WIN95_PROBE=1. Boots fresh automatically, samples CPU + VGA + text screen every 5s, writes /tmp/win95-probe.json + /tmp/win95-screen.png, detects SUCCESS vs FAIL modes, optionally drives keyboard input.
src/renderer/smb/index.ts	Wraps console.log so [smb] and [nbns] lines tee to $TMPDIR/windows95-smb.log (outside Electron, readable by any polling script — no CDP needed).
tools/probe-boot.sh	One-shot: kill leftovers → parcel build → launch Electron → poll /tmp/win95-probe.done → report → kill.

One-shot boot test

tools/probe-boot.sh

Prints SUCCESS or a FAIL verdict. ~40s on a clean run.

Boot + type into Run

pkill -9 -f "windows95.*electron"; sleep 2
rm -f "$HOME/Library/Application Support/windows95/state-v4.bin"
rm -f /tmp/win95-probe.json /tmp/win95-probe.done \
      "$TMPDIR/windows95-smb.log"

WIN95_PROBE=1 \
WIN95_PROBE_SCRIPT='HOST/HOST' \
WIN95_SMB_SHARE="$HOME/Downloads" \
  ./node_modules/.bin/electron . > /tmp/win95-electron.log 2>&1 &

WIN95_PROBE_SCRIPT='HOST/HOST' types \\HOST\HOST into Start → Run on desktop. WIN95_PROBE_DOSBOX=1 instead opens command, types dir, and (with WIN95_PROBE_DOSBOX_ALTENTER=1) toggles fullscreen — this is the regression scenario for the windowed-DOS-box VBE leak. WIN95_PROBE_VGATRACE=1 wraps the VGA I/O ports at the io.ports[] layer and writes [port, op, value, "eip VMPE cplN"] tuples to /tmp/win95-vgatrace.json every tick (heavy — can hit 1M entries during boot). / → \ substitution (env var / shell quoting, pragmatism). The harness drives it via XT scancodes — Win95 doesn't have Win+R (Win98+ only), so the sequence is Esc, Esc, Ctrl+Esc, R, backslashes + text, Enter.

Reading results

File	What
/tmp/win95-probe.json	Live status: phase (init/text-mode/splash/desktop), gfxW/H, textScreen, instructionDelta, verdict
/tmp/win95-probe.done	Written once when verdict is decided
/tmp/win95-screen.png	Canvas screenshot, refreshed each tick
$TMPDIR/windows95-smb.log	SMB/NBNS protocol trace
/tmp/win95-electron.log	Electron stderr

Verdicts

Verdict	Meaning	Action
SUCCESS	Canvas ≥640×480, CPU active, uptime >30s	desktop reached
FAIL_VXDLINK	"Invalid VxD dynamic link call"	flaky — retry
FAIL_IOS / FAIL_PROTECTION	IOS subsystem protection error	usually driver/BIOS mismatch
FAIL_KRNL386	"Cannot find KRNL386.EXE" in safe mode	disk reads returning garbage — wasm/BIOS drift
FAIL_SPLASH_HANG	Canvas stuck 320×400 for >70s	IRQ starvation — if you're on v86 master, check the IDE register fix
FAIL_HUNG	CPU stopped advancing or text screen frozen 40s	hard hang

Rules of the road

• Sporadic bluescreens are normal on all v86 versions. One FAIL_VXDLINK or FAIL_HUNG doesn't prove anything — retry up to 3×.
• Always clean state (state-v4.bin) before a probe. pkill on a wedged Electron triggers onbeforeunload, saving the corrupted state. Deleting it forces fallback to images/default-state.bin.
• Don't trust the text buffer in graphics mode. After desktop (≥640×480) the stale BIOS text lingers in the buffer. The harness's phase field accounts for this; don't re-read textScreen in a desktop phase and think you hit a BSOD.
• Kill Electron when done. Background processes pile up, each holding the disk image lock. pkill -f "windows95.*electron" on every path out.

Bisecting v86

tools/bisect-v86.sh <commit> handles one step. The harness retries 3× per commit. Hard-won lessons:

1. Validate bounds against a known-good binary. Source-built wasm can drift from prod due to cargo/rustc version differences. We hit this: the "GOOD" bound produced a wasm that couldn't read the disk at all.
2. JS-only when toolchain drifts. Keep the prod wasm, rebuild only libv86.js at each commit. Closure is deterministic enough; cargo isn't always. Works until you cross a commit that changes the JS↔wasm ABI (for v86, the APIC→Rust port in Aug 2025).
3. Retry on FAIL, never on SUCCESS. One SUCCESS = commit is good. Three different FAILs at the same commit = commit is bad.
4. State cleanup between runs (see above). Skipping this is the #1 cause of spurious "bad" verdicts during bisect.

Extending the harness

• New verdicts: add to the chain in collectStatus in debug-harness.ts
• New keyboard actions: extend runScript (current types: keys, chord, text, wait)
• New probe signals: add to ProbeStatus interface

Gate everything new on process.env.WIN95_PROBE === "1" so it stays out of the normal app.

Common failure diagnostics

Symptom	Check
No SMB traffic at all	$TMPDIR/windows95-smb.log should have hooked adapter line. If absent, v86 API changed — see src/renderer/smb/README.md
SMB hooks fire, no connection	Win95's "NetBIOS over TCP/IP" checkbox — bake into default-state.bin
Boot hangs on 2996c087 or older v86	You probably have a ABI-mismatched wasm/JS pair. Prod wasm is the ground truth; rebuild JS against it.