perf(autocomplete): skip completion queries when nothing is shown (#1088)

fetchSuggestions ran the full completion pipeline (history scan, fig specs, remote path lookups) on the main thread even when both the popup and ghost text were disabled — the results were then discarded. Add a shouldQueryCompletions(settings) gate and bail out early (clearing any stale state) when neither display mode is on.

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

components/terminal/autocomplete/useTerminalAutocomplete.ts

@@ -47,6 +47,18 @@ export const DEFAULT_AUTOCOMPLETE_SETTINGS: AutocompleteSettings = {
   fastTypingThresholdMs: 40,
 };
 
+/**
+ * Whether completion work is worth doing — i.e. whether anything would
+ * actually be rendered. With both the popup and ghost text disabled, querying
+ * completions only to discard the result is pure main-thread waste, so callers
+ * skip it entirely.
+ */
+export function shouldQueryCompletions(
+  settings: Pick<AutocompleteSettings, "showPopupMenu" | "showGhostText">,
+): boolean {
+  return settings.showPopupMenu || settings.showGhostText;
+}
+
 /** Shared empty state to avoid creating new objects on every reset */
 const EMPTY_STATE: AutocompleteState = Object.freeze({
   suggestions: [],
@@ -640,6 +652,15 @@ export function useTerminalAutocomplete(
       return;
     }
 
+    // Nothing will be rendered when both the popup and ghost text are off, so
+    // don't run the (potentially expensive) completion query just to throw the
+    // result away. Clear any stale state and bail before touching history,
+    // fig specs, or remote path lookups.
+    if (!shouldQueryCompletions(settingsRef.current)) {
+      clearState();
+      return;
+    }
+
     // Capture version at start — if it changes during async work, discard results
     const version = ++fetchVersionRef.current;
 

components/terminal/completionGate.test.ts

@@ -0,0 +1,25 @@
+import test from "node:test";
+import assert from "node:assert/strict";
+
+import { shouldQueryCompletions } from "./autocomplete/useTerminalAutocomplete.ts";
+
+test("queries completions when the popup menu is enabled", () => {
+  assert.equal(
+    shouldQueryCompletions({ showPopupMenu: true, showGhostText: false }),
+    true,
+  );
+});
+
+test("queries completions when ghost text is enabled", () => {
+  assert.equal(
+    shouldQueryCompletions({ showPopupMenu: false, showGhostText: true }),
+    true,
+  );
+});
+
+test("skips completion work when both popup and ghost text are off", () => {
+  assert.equal(
+    shouldQueryCompletions({ showPopupMenu: false, showGhostText: false }),
+    false,
+  );
+});