Session log: reflow bug fix + titlebar tidy-up; correct stack note

memory.md still said Svelte 5; migration to React 18 happened in
774b863. Also log this session's investigation, fix, and the
follow-up about CLAUDE.md still needing the same update.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

memory.md

@@ -4,7 +4,7 @@ Durable memory for this project. Read at session start, update before session en
 
 ## Decisions & rationale
 
-- **Stack: Tauri 2 + Svelte 5 + TypeScript + Vite + pnpm + xterm.js + `portable-pty`.** Mirrors `claude-usage-widget` so we reuse a known-good Windows-targeting toolchain (MSVC + WebView2 + NSIS installer). No new technology bets stacked on top of the new product bet.
+- **Stack: Tauri 2 + React 18 + TypeScript + Vite + pnpm + xterm.js + `portable-pty`.** Originally Svelte 5; migrated to React in commit `774b863` (released as 0.2.0). Mirrors `claude-usage-widget`'s Windows-targeting toolchain (MSVC + WebView2 + NSIS installer). No new technology bets stacked on top of the new product bet. **CLAUDE.md still says Svelte 5 — should be updated when convenient.**
 - **Layout model: binary tree of splits, NOT free-form rectangles.** Same as i3 / tmux / Zellij. Each internal node is HSplit/VSplit + ratio; each leaf is a terminal. Dragging a gutter mutates one parent ratio; both sibling subtrees reflow; descendants get `resize`. Adaptive resize falls out automatically with no constraint solver. Preset layouts ("3 columns", "2×2") are pre-built trees.
 - **PTY backend: `portable-pty` (same crate WezTerm uses).** Spawns `wsl.exe -d <distro> --cd <path>` on Windows. Manager is a `Mutex<HashMap<PaneId, PaneHandle>>` in Rust; each pane has a background reader thread that emits `pane://{id}/data` events.
 - **Wire format: base64-encoded byte chunks via Tauri events.** xterm.js's `onData` emits strings; we UTF-8 encode then base64. Slower than a typed-array payload but trivially correct. Revisit if throughput matters.
@@ -51,6 +51,23 @@ Durable memory for this project. Read at session start, update before session en
 
 ## Session log
 
+### 2026-05-25 — Reflow bug fix + titlebar tidy-up
+
+- **Bug: terminal text reflowing every few seconds.** User reported "redrawing every few seconds" with text changing lines. Added a `console.trace` inside the `ResizeObserver` in `XtermPane.tsx`, then expanded the diagnostic to log titlebar/pane-wrap/leaf/toolbar heights. Caught it: titlebar was oscillating between **34px and 50px** in sync with pane heights changing by ±15.4px (one button-row).
+- **Root cause: text-wrap inside flex buttons.** Titlebar is `display: flex` with default `flex-wrap: nowrap`. Buttons have no `white-space: nowrap`. On a narrow window, flex items shrink past their natural width → text wraps *inside* a button (e.g. "📡 all off" → two lines) → button grows ~16px → titlebar grows ~16px → `.pane-wrap` shrinks → `ResizeObserver` fires on every xterm → `fit()` reflows. The periodic flap was idle detection: when `idleLeafIds.size` toggles between 0 and N, `.layout-info` gains/loses " · N idle", which is just enough extra width to push a button across its wrap threshold. Same root cause on narrow per-pane toolbars (`tlb=37` was visible in the diagnostic for a 200px pane).
+- **Fix:** lock heights on both bars. `.titlebar { height: 34px; white-space: nowrap; }` + `.titlebar > * { flex-shrink: 0 }`; same shape for `.pane-toolbar { height: 24px; ... }`. First attempt also used `overflow: hidden` which left an ugly horizontal scrollbar (auto) AND would have clipped dropdowns — removed. Final: `nowrap` + `flex-shrink:0` + fixed `height` is enough; overflow stays visible. Commit `e464464`.
+- **Titlebar tidy-up.** Pre-fix titlebar was crowded (inline distro buttons + PowerShell + 🔑 SSH hosts + 5 preset buttons + others). Collapsed:
+  - Inline shell buttons → single **`Ubuntu ▾` dropdown** (WSL + Windows sections), reusing the existing `.distro-menu / .shell-menu` styles from `LeafPane.css` (global classes).
+  - 5 preset buttons → **`layout ▾` dropdown** (Single pane / Two columns / Three columns / Two rows / 2×2 grid).
+  - `🔑` stays as a separate icon-only button next to the shell picker.
+  - 🔔 test-toast button removed (dev crutch).
+- **`+` spawn button.** User pointed out "default:" semantics were weak — the picked shell only fired on first-boot or close-last-pane. Repurposed: dropped the "default:" label, added a **`+` button** next to the picker. Click `+` → splits the active pane with the currently-picked shell, smart-oriented (split right if pane is wider than tall, down otherwise). Per-pane `⇥/⇣` arrows still inherit from parent (best for "another window into this context"); the titlebar selection only fires on `+` / boot / close-last. Commit `fa18307`.
+
+Open follow-ups from this session:
+- **CLAUDE.md still names Svelte 5** in the stack; should be updated to React 18.
+- **Keyboard shortcut for `+`?** Currently mouse-only. `Ctrl+Shift+N` would be the conventional choice but isn't bound.
+- **Narrow window UX.** With `overflow: visible`, titlebar items that don't fit horizontally render past the right edge / get clipped by the viewport. Acceptable but not great. A real fix is to collapse less-important items into an overflow menu when width is tight.
+
 ### 2026-05-25 — SSH + clickable links + promote + help + MCP v1
 
 Big session, ~12 commits. Headlines: