# Phase 0 — substrate for iter7

Opened **2026-05-19** after [iter6 close GREEN](phase8_iteration6_close.md).

## Locked research question — iter7

> **Run stock `vkcube --c 120 --wsi wayland` (Vulkan reference rotating-cube demo) on ohm against the live Plasma/Wayland session, with `PAN_I_WANT_A_BROKEN_VULKAN_DRIVER=1`. Verify:**
>
> - Process exits 0
> - 120 frames rendered (vkcube reports if --c was honored)
> - No GPU faults in dmesg during the run
> - No kernel-side panfrost errors
> - Operator may visually confirm correct cube rendering (PineTab2 has its own display)

## Why this shape

iter1–6 closed all the synthetic-probe paths. iter7 is the **first real off-the-shelf application**. New surface area:

- **WSI / swapchain (`VK_KHR_swapchain`)** — first time we use the swapchain path.
- **`VK_KHR_wayland_surface`** — first time we connect to a live Wayland compositor.
- **Continuous frame submission** — many `vkQueueSubmit` calls in sequence, with synchronization across frames.
- **Acquire/present cycle** — vkAcquireNextImageKHR + vkQueuePresentKHR per frame.
- **vkcube's own state** — rotation matrix per frame, textured cube vertices, depth buffer, all bundled together.

If vkcube works end-to-end, that's massive validation toward TuxRacer-via-Zink. If it crashes, we have a known-reference reproducer + a real bug to characterize.

## Session info (gathered)

- Active user: `mfritsche` (UID 1001) on `tty1`
- `XDG_RUNTIME_DIR=/run/user/1001`
- `WAYLAND_DISPLAY=wayland-0` (socket present at `/run/user/1001/wayland-0`)
- vkcube version: from `vulkan-tools 1.4.350.0-1` package

## Hypothesis space

1. **`VK_KHR_wayland_surface` plumbing.** First-ever PanVk-Bifrost test of Wayland surface creation.
2. **Swapchain creation.** PanVk's swapchain path may have stale or untested code on v6/v7 — particularly modifier-aware swapchain images.
3. **Present queue** — vulkaninfo's "present support = false" on the only queue family (no-surface query) may turn into a runtime issue when a real surface exists.
4. **Continuous frame submission** — sync2 / timeline semaphore plumbing across frames.
5. **vkcube's specific draw shape** — textured cube uses MVP UBO, vertex buffer with positions, normals, texcoords; texture upload; depth test. All things proven in isolation, but combined here.

## In-scope (LOCKED 2026-05-19 for iter7)

- 120 frames of vkcube via Wayland WSI on ohm.
- Stock binary (no modifications).
- Whatever GPU PanVk picks (single Mali on ohm).

## Out-of-scope (LOCKED 2026-05-19 for iter7)

- VK_KHR_xcb_surface / VK_KHR_xlib_surface paths.
- VK_KHR_display direct-mode (would conflict with Plasma session).
- VK_EXT_headless_surface (not strictly needed if Wayland works).
- vkmark / Zink (iter8+).
- vkcube subtests (--use_staging variations).

## Reference

- Prior closes: [iter1](phase8_iteration1_close.md) – [iter6](phase8_iteration6_close.md).