diff --git a/docs/UI_SPIKE_SCORECARD.md b/docs/UI_SPIKE_SCORECARD.md
index 041ee26..4e8a418 100644
--- a/docs/UI_SPIKE_SCORECARD.md
+++ b/docs/UI_SPIKE_SCORECARD.md
@@ -7,7 +7,7 @@ from macOS and Linux and the hard gates pass.
 | Criterion | Hard gate | GPUI | Floem |
 |---|---:|---:|---:|
 | Builds on macOS Apple Silicon | yes | pending | pending |
-| Builds on Ubuntu | yes | pending | pending |
+| Builds on Ubuntu | yes | conditional | pass |
 | Builds on Omarchy/Arch | yes | pending | pending |
 | Dependency/license closure permits Apache-2.0 distribution | yes | pending | pending |
 | Keyboard navigation + AccessKit tree | yes | pending | pending |
@@ -24,3 +24,23 @@ from macOS and Linux and the hard gates pass.
 The current programs establish dependency, build, launch, and static layout
 baselines. The next iteration adds deterministic streaming, input timestamps,
 accessibility identifiers, a native Markdown editor, and one Wry browser child.
+
+## Ubuntu baseline — metal, 2026-08-31
+
+Host: Ubuntu 24.04 x86_64, Rust 1.94.1. Both candidates used the same 1280×800
+six-pane fixture and were launched under the active X11 desktop.
+
+| Observation | GPUI 0.2.2 | Floem `778bb5f2` |
+|---|---:|---:|
+| `cargo check` from downloaded dependency cache | 20.76 s, 1.04 GiB max RSS | 24.26 s first attempt + 4.06 s after enabling required editor feature, 753 MiB max RSS |
+| Debug executable link | pass with a user-local linker symlink for installed `libxkbcommon-x11.so.0` | pass |
+| Debug executable size | 442 MiB | 475 MiB |
+| Native window launch and six-pane render | pass | pass |
+| Root workspace CI | 8/8 tests, strict Clippy and doctests pass in 10.79 s | shared result |
+
+These are cold-development baselines, not startup, release-size, or runtime
+performance numbers. GPUI's Ubuntu row remains conditional because the host has
+the runtime `libxkbcommon-x11.so.0` but lacks the unversioned development linker
+name normally supplied by `libxkbcommon-x11-dev`. Floem current main also
+requires its `editor` feature for the style/label modules used by this shell;
+that feature is now explicit in the spike. Neither finding decides the UI stack.