diff --git a/experimental/papyrus/client/src/terminal/ghosttyBackend.ts b/experimental/papyrus/client/src/terminal/ghosttyBackend.ts
index 827321e..c43f2d9 100644
--- a/experimental/papyrus/client/src/terminal/ghosttyBackend.ts
+++ b/experimental/papyrus/client/src/terminal/ghosttyBackend.ts
@@ -7,6 +7,12 @@
 // We pass only what ghostty-web understands. Because it has no line-height (and to stay
 // safe about runtime option mutation), setTheme/setLineHeight return false — Terminal.tsx
 // then remounts the pane at the new settings via its remount token.
+//
+// Three shims paper over ghostty-web quirks that xterm handles natively: we answer the DA1
+// query (see below), hide the input textarea's caret (see open()), and correct cell sizing —
+// `createGhosttyBackend` waits for the webfont before the renderer first measures, and open()
+// rounds the cell width to the nearest pixel instead of ghostty's ceil (which ran cells ~10%
+// too wide). ghostty-web exposes no width knob, so both live here in the adapter.
 
 import { init, Terminal as GhosttyTerm, FitAddon, type ITheme } from "ghostty-web";
 import type { BackendOptions, TerminalBackend, TerminalSize } from "./backend";
@@ -42,6 +48,27 @@ class GhosttyBackend implements TerminalBackend {
     // its own cursor on the canvas, so hide the textarea's caret (it stays focusable for input).
     const input = container.querySelector("textarea");
     if (input) input.style.caretColor = "transparent";
+    this.roundCellWidth();
+  }
+
+  // ghostty-web sizes a cell at ceil(measureText("M").width) — always the next whole pixel up,
+  // making cells ~1px (~10%) wider than the glyph advance. Round to the nearest pixel instead
+  // (what native terminals do), so libghostty cells match xterm's width. renderer/measureFont
+  // are ghostty-web internals (no public width knob exists), so this is a deliberate adapter
+  // shim. Runs synchronously in open(), before Terminal.tsx's fit() and WS connect, so the
+  // corrected metrics flow through the normal fit/resize path with no Terminal.tsx changes.
+  private roundCellWidth() {
+    const renderer = (this.term as unknown as { renderer?: Record<string, unknown> }).renderer;
+    if (!renderer || typeof renderer.measureFont !== "function") return;
+    const measureUpstream = (renderer.measureFont as () => Record<string, unknown>).bind(renderer);
+    const ctx = document.createElement("canvas").getContext("2d");
+    renderer.measureFont = () => {
+      const m = measureUpstream(); // upstream height/baseline (+ its ceil'd width, discarded)
+      if (!ctx) return m;
+      ctx.font = `${renderer.fontSize}px ${renderer.fontFamily}`;
+      return { ...m, width: Math.round(ctx.measureText("M").width) };
+    };
+    (renderer.remeasureFont as () => void)(); // recompute this.metrics with the rounded width
   }
 
   write(data: string) {
@@ -80,5 +107,12 @@ class GhosttyBackend implements TerminalBackend {
 
 export async function createGhosttyBackend(o: BackendOptions): Promise<TerminalBackend> {
   await init();
+  // The terminal font is an async swap webfont (see index.html); ghostty measures the cell
+  // exactly once at open() and never remeasures, so wait for fonts to settle first — otherwise
+  // it can lock the fallback font's advance. Resolves even on a failed/offline load, so it
+  // can't hang; guarded for non-DOM (test) envs.
+  if (typeof document !== "undefined" && document.fonts?.ready) {
+    await document.fonts.ready;
+  }
   return new GhosttyBackend(o);
 }