# Windows Update Template - Development Session

## Goal
Create a `customizeImage` template that applies Windows Updates to an existing image via the Windows Update COM API in Audit Mode, then compacts the qcow2.

## What was built

### New files
- `lib/images/windows/templates/essentials/windows-update.nix` — template that boots into Audit Mode, runs Windows Update via COM API, handles reboots automatically, compacts image

### Modified files
- `lib/images/windows/helpers/customizeImage.nix` — added `compact`, `qemuTimeout` parameters
- `lib/images/windows/templates/default.nix` — wired `windowsUpdate` into `essentials`
- `lib/images/windows/win10/images.nix` — added `updated` step between `upstream` and `basic`
- `lib/images/windows/win11/images.nix` — same

### New customizeImage parameters
- `compact ? false` — flattens COW chain via `qemu-img convert` into standalone qcow2 (no backing file)
- `qemuTimeout ? 1800` — configurable QEMU timeout in seconds (was hardcoded 30 min)

### How the template works
1. Boots image in Audit Mode with QEMU user networking
2. Starts `wuauserv` service, removes update-blocking policies
3. Uses PowerShell COM API (`Microsoft.Update.Session`) to search, download, install updates
4. Accepts EULAs, logs per-update results
5. If reboot required: copies script, preserves Audit Mode registry keys, re-registers via RunOnce, reboots
6. After reboot: continues with next round (up to `maxRounds`, default 3)
7. When done: runs `dism /Cleanup-Image /StartComponentCleanup /ResetBase`, shuts down
8. Host-side: `qemu-img convert` flattens COW chain (when `compact=true`)

### Usage
```nix
# Online mode (default) - triggers Windows Update service
essentials.windowsUpdate {}
essentials.windowsUpdate { maxRounds = 5; }

# In image pipeline
updated = customizeImage upstream (templates.essentials.windowsUpdate {});
basic = customizeImageFold updated [ ... ];
```

## Test results

### What works
- Windows Update service starts successfully in Audit Mode
- COM API finds all available updates (cumulative, .NET, Defender, MSRT)
- Downloads and installs 6 updates including:
  - 2026-05 Cumulative Update KB5087544
  - .NET Framework updates (KB5010472, KB5011048, KB5088859)
  - Windows Malicious Software Removal Tool (KB890830)
  - Microsoft Defender definitions (KB2267602)
- `compact` flag works — produces standalone qcow2 without backing file
- Image grows from 5.02 GB to ~8.33 GB with updates

### Issues found and fixed during session

1. **First build (no service start)**: COM API found 0 updates because `wuauserv` wasn't running
   - Fix: added `net start wuauserv` + `sc config wuauserv start= auto` + remove blocking policies + 30s wait

2. **Wrapper deletes script before reboot**: After round 1, the wrapper's `del /q C:\vmix-audit-script.cmd` runs before reboot completes, so RunOnce points to deleted file
   - Fix: script copies itself to `C:\vmix-update-continue.cmd` before rebooting; registers that path in RunOnce

3. **Audit Mode lost after reboot**: Cumulative updates can reset the Audit Mode flag, causing Windows to enter OOBE instead of Audit Mode after reboot
   - Fix: explicitly set `AuditBoot=1` and `AuditInProgress=1` registry keys before rebooting

4. **No shutdown after round 2**: When script runs from RunOnce (not wrapper), no shutdown command executes
   - Fix: script always calls `shutdown /s /f /t 10` when done, regardless of invocation method

### Remaining TODO (for next session on faster machine)
- [ ] Verify the Audit Mode preservation fix (AuditBoot + AuditInProgress registry keys) actually works — last build was still in round 1 install when session ended
- [ ] The cumulative update install takes ~60-90 min with 4GB RAM — consider using 8GB for faster builds
- [ ] Test round 2 → round 3 flow (does it find additional updates after cumulative?)
- [ ] Test with `compact = true` to verify final image is standalone
- [ ] Test full pipeline: `upstream → updated → basic → generalize`
- [ ] Test win11 images too
- [ ] Consider: should `windowsUpdate` go before or after `virtioTools` in the pipeline? Currently it's before (applied to raw upstream), but having virtio drivers might help with disk I/O performance during update install
- [ ] The template is impure (downloads from Microsoft during build) — document this clearly
- [ ] Consider adding a `maxRounds = 1` fast mode that skips the reboot cycle (just installs whatever doesn't need reboot)

## Build command for testing
```bash
nix build --print-build-logs --impure --option sandbox relaxed --expr '
  let
    vmixLib = (builtins.getFlake "path:/storage/gitrepos/vmix.nix").lib.x86_64-linux;
    upstream = vmixLib.windows.images.win10.ltsc.upstream;
    withVirtio = vmixLib.windows.customizeImage upstream vmixLib.windows.templates.essentials.virtioTools;
    windowsUpdate = vmixLib.windows.templates.essentials.windowsUpdate {};
  in vmixLib.windows.customizeImage withVirtio (windowsUpdate // { vncDisplay = ":55"; compact = false; })
'
```

Monitor via VNC on port 5955 (`localhost:55`):
```bash
gvnccapture localhost:55 /tmp/screenshot.png
```