diff --git a/apps/desktop/src/components/editor/QueryEditor.vue b/apps/desktop/src/components/editor/QueryEditor.vue
index 261f5c77d1..fa71599a1f 100644
--- a/apps/desktop/src/components/editor/QueryEditor.vue
+++ b/apps/desktop/src/components/editor/QueryEditor.vue
@@ -185,6 +185,7 @@ import { startsQueryEditorRectangularSelection, startsQueryEditorSelectionDrag,
 import { LARGE_PASTE_HISTORY_USER_EVENT, normalizeQueryEditorPasteText, recoverableNativePasteSuffix, shouldRecoverLargeTauriPaste } from "@/lib/editor/queryEditorLargePaste";
 import { queryEditorClipboardPasteChange } from "@/lib/editor/queryEditorClipboardPaste";
 import { computePasteCaretResyncTarget } from "@/lib/editor/queryEditorPasteCaretResync";
+import { needsDiagnosticCaretReanchor } from "@/lib/editor/queryEditorDiagnosticCaretAnchor";
 import { queryEditorCommentTokens, queryEditorLineCommentToken, queryEditorWordLanguageData } from "@/lib/editor/queryEditorLineComment";
 import { createShellLineCommentHighlight } from "@/lib/editor/codemirrorShellLineCommentHighlight";
 import { extendQueryEditorSelection, runQueryEditorAltExtendSelection } from "@/lib/editor/queryEditorExtendSelection";
@@ -3690,18 +3691,49 @@ function sqlSemanticDecorationRanges(currentState: import("@codemirror/state").E
     );
 }
 
+// Mirrors CodeMirror's own root handling: shadow roots only expose
+// `getSelection` on some browsers, otherwise the owner document holds it.
+function editorRootSelection(currentView: EditorViewType): Selection | null {
+  const root = currentView.root as unknown as ShadowRoot & { getSelection?: () => Selection | null };
+  if (root.nodeType !== 11) return (root as unknown as Document).getSelection();
+  if (typeof root.getSelection === "function") return root.getSelection() ?? null;
+  return root.ownerDocument?.getSelection() ?? null;
+}
+
+// See queryEditorDiagnosticCaretAnchor.ts for why the browser caret needs re-anchoring.
+function reanchorCaretAfterDiagnostics(currentView: EditorViewType) {
+  const selection = currentView.state.selection;
+  const target = selection.ranges.length === 1 && selection.main.empty ? currentView.domAtPos(selection.main.head) : null;
+  const domSelection = editorRootSelection(currentView);
+  const reanchor = needsDiagnosticCaretReanchor({
+    hasFocus: currentView.hasFocus,
+    composing: currentView.composing,
+    domRangeCount: domSelection?.rangeCount ?? 0,
+    currentAnchorNode: domSelection?.anchorNode ?? null,
+    currentAnchorOffset: domSelection?.anchorOffset ?? 0,
+    targetNode: target?.node ?? null,
+    targetOffset: target?.offset ?? 0,
+  });
+  if (!reanchor || !domSelection || !target) return;
+  domSelection.collapse(target.node, target.offset);
+}
+
 function reconfigureDiagnostics() {
-  if (!view.value) return;
+  const currentView = view.value;
+  if (!currentView) return;
   if (setSqlDiagnosticsEffect) {
-    view.value.dispatch({
+    currentView.dispatch({
       effects: setSqlDiagnosticsEffect.of(semanticDiagnostics),
     });
-    return;
+  } else {
+    if (!diagnosticComp || !buildSqlDiagnosticExtension) return;
+    currentView.dispatch({
+      effects: diagnosticComp.reconfigure(buildSqlDiagnosticExtension()),
+    });
   }
-  if (!diagnosticComp || !buildSqlDiagnosticExtension) return;
-  view.value.dispatch({
-    effects: diagnosticComp.reconfigure(buildSqlDiagnosticExtension()),
-  });
+  // Diagnostic decorations re-parent the DOM text nodes around the caret; put the
+  // browser's insertion point back on the caret before the next keystroke (#9480).
+  reanchorCaretAfterDiagnostics(currentView);
 }
 
 function setSemanticDiagnostics(next: SqlSemanticDiagnostic[]) {
diff --git a/apps/desktop/src/lib/__tests__/editor/queryEditorDiagnosticCaretAnchor.spec.ts b/apps/desktop/src/lib/__tests__/editor/queryEditorDiagnosticCaretAnchor.spec.ts
new file mode 100644
index 0000000000..ff6362d889
--- /dev/null
+++ b/apps/desktop/src/lib/__tests__/editor/queryEditorDiagnosticCaretAnchor.spec.ts
@@ -0,0 +1,60 @@
+import { readFileSync } from "node:fs";
+import { describe, expect, it } from "vitest";
+import { needsDiagnosticCaretReanchor, type DiagnosticCaretAnchorState } from "@/lib/editor/queryEditorDiagnosticCaretAnchor";
+
+const textNode = { nodeType: 3, name: "text" } as unknown as Node;
+const lineNode = { nodeType: 1, name: "line" } as unknown as Node;
+
+function state(overrides: Partial<DiagnosticCaretAnchorState> = {}): DiagnosticCaretAnchorState {
+  return {
+    hasFocus: true,
+    composing: false,
+    domRangeCount: 1,
+    currentAnchorNode: lineNode,
+    currentAnchorOffset: 2,
+    targetNode: textNode,
+    targetOffset: 3,
+    ...overrides,
+  };
+}
+
+describe("needsDiagnosticCaretReanchor", () => {
+  it("re-anchors when the browser caret collapsed onto the surrounding line element", () => {
+    // The reported case: `document.getSelection()` reports (line, childCount)
+    // while the caret really sits inside the text node.
+    expect(needsDiagnosticCaretReanchor(state())).toBe(true);
+  });
+
+  it("re-anchors when the browser caret sits on the wrong offset of the same node", () => {
+    expect(needsDiagnosticCaretReanchor(state({ currentAnchorNode: textNode, currentAnchorOffset: 0 }))).toBe(true);
+  });
+
+  it("keeps a caret that already matches the precise DOM position", () => {
+    expect(needsDiagnosticCaretReanchor(state({ currentAnchorNode: textNode, currentAnchorOffset: 3 }))).toBe(false);
+  });
+
+  it("does not touch the caret while an IME composition is running", () => {
+    expect(needsDiagnosticCaretReanchor(state({ composing: true }))).toBe(false);
+  });
+
+  it("does not touch the caret when the editor is not focused", () => {
+    expect(needsDiagnosticCaretReanchor(state({ hasFocus: false }))).toBe(false);
+  });
+
+  it("keeps non-empty selections and multiple cursors untouched", () => {
+    expect(needsDiagnosticCaretReanchor(state({ targetNode: null }))).toBe(false);
+    expect(needsDiagnosticCaretReanchor(state({ domRangeCount: 2 }))).toBe(false);
+    expect(needsDiagnosticCaretReanchor(state({ domRangeCount: 0, currentAnchorNode: null }))).toBe(false);
+  });
+});
+
+describe("QueryEditor diagnostic caret re-anchor wiring", () => {
+  const queryEditorSource = readFileSync(new URL("../../../components/editor/QueryEditor.vue", import.meta.url), "utf8");
+
+  it("re-anchors the browser caret after applying diagnostics, outside a transaction", () => {
+    expect(queryEditorSource).toMatch(/function reconfigureDiagnostics\(\)[\s\S]*?reanchorCaretAfterDiagnostics\(currentView\)/);
+    // The re-anchor must not dispatch a selection transaction: that closes the
+    // completion popup the user is looking at (#9480).
+    expect(queryEditorSource).toMatch(/function reanchorCaretAfterDiagnostics\(currentView: EditorViewType\)[\s\S]*?domSelection\.collapse\(target\.node, target\.offset\)/);
+  });
+});
diff --git a/apps/desktop/src/lib/editor/queryEditorDiagnosticCaretAnchor.ts b/apps/desktop/src/lib/editor/queryEditorDiagnosticCaretAnchor.ts
new file mode 100644
index 0000000000..9d20110992
--- /dev/null
+++ b/apps/desktop/src/lib/editor/queryEditorDiagnosticCaretAnchor.ts
@@ -0,0 +1,42 @@
+/**
+ * Chromium keeps using its own native insertion point for the next typed
+ * character. When a decoration-only update (SQL / Redis syntax diagnostics)
+ * wraps or unwraps the text nodes next to the caret, the browser collapses
+ * that insertion point onto the surrounding line element instead of a text
+ * node. `document.getSelection()` still reports a position that CodeMirror
+ * considers equivalent to the caret — the same document position, only
+ * expressed as (lineElement, childCount) instead of (textNode, offset) — so
+ * CodeMirror leaves it alone, while the browser inserts the next character at
+ * the start of the re-parented text node.
+ *
+ * Reported as #9480: after a short pause inside a Redis command argument
+ * ("HGET us|"), the typed characters land at the start of the argument
+ * ("HGET er:1us").
+ *
+ * Collapsing the DOM caret onto the precise DOM position of the editor
+ * selection restores the insertion point. This has to happen outside a
+ * CodeMirror transaction: a selection transaction would reset the completion
+ * popup the user is currently looking at, and it is not needed because the
+ * editor state already sits on that position.
+ */
+export interface DiagnosticCaretAnchorState {
+  /** Whether the editor owns the browser focus. */
+  hasFocus: boolean;
+  /** Whether an IME composition is in progress — the browser owns the caret then. */
+  composing: boolean;
+  /** Number of ranges in the DOM selection of the editor root. */
+  domRangeCount: number;
+  /** Anchor node the browser currently uses for the caret. */
+  currentAnchorNode: Node | null;
+  currentAnchorOffset: number;
+  /** Precise DOM position of the editor caret, or null when there is no single empty caret. */
+  targetNode: Node | null;
+  targetOffset: number;
+}
+
+export function needsDiagnosticCaretReanchor(state: DiagnosticCaretAnchorState): boolean {
+  if (!state.hasFocus || state.composing) return false;
+  if (state.domRangeCount !== 1) return false;
+  if (!state.currentAnchorNode || !state.targetNode) return false;
+  return state.currentAnchorNode !== state.targetNode || state.currentAnchorOffset !== state.targetOffset;
+}