diff --git a/frontend/editor/src/core/hooks/tools/shared/useBaseTool.test.tsx b/frontend/editor/src/core/hooks/tools/shared/useBaseTool.test.tsx
new file mode 100644
index 0000000000..9e0d0f4e14
--- /dev/null
+++ b/frontend/editor/src/core/hooks/tools/shared/useBaseTool.test.tsx
@@ -0,0 +1,81 @@
+import { describe, expect, test, vi, beforeEach } from "vitest";
+import { renderHook } from "@testing-library/react";
+import { useBaseTool } from "@app/hooks/tools/shared/useBaseTool";
+import type { ToolOperationHook } from "@app/hooks/tools/shared/useToolOperation";
+import type { BaseParametersHook } from "@app/hooks/tools/shared/useBaseParameters";
+import type { StirlingFile } from "@app/types/fileContext";
+
+// Isolate useBaseTool from the file/viewer/endpoint contexts so the test can
+// focus on the unmount lifecycle wiring.
+const scopedFiles: { current: StirlingFile[] } = { current: [] };
+vi.mock("@app/hooks/tools/shared/useViewScopedFiles", () => ({
+  useViewScopedFiles: () => scopedFiles.current,
+}));
+vi.mock("@app/hooks/useEndpointConfig", () => ({
+  useEndpointEnabled: () => ({ enabled: true, loading: false }),
+}));
+
+const cancelOperation = vi.fn();
+
+const makeOperation = (isLoading: boolean): ToolOperationHook<unknown> =>
+  ({
+    files: [],
+    thumbnails: [],
+    isGeneratingThumbnails: false,
+    downloadUrl: null,
+    downloadFilename: null,
+    downloadLocalPath: null,
+    outputFileIds: [],
+    isLoading,
+    status: "",
+    errorMessage: null,
+    progress: null,
+    willUseCloud: false,
+    executeOperation: vi.fn(),
+    resetResults: vi.fn(),
+    clearError: vi.fn(),
+    cancelOperation,
+    undoOperation: vi.fn(),
+  }) as unknown as ToolOperationHook<unknown>;
+
+const makeParams = (): BaseParametersHook<unknown> =>
+  ({
+    parameters: {},
+    updateParameter: vi.fn(),
+    setParameters: vi.fn(),
+    resetParameters: vi.fn(),
+    validateParameters: () => true,
+    getEndpointName: () => "compress-pdf",
+  }) as unknown as BaseParametersHook<unknown>;
+
+const props = {
+  onPreviewFile: vi.fn(),
+  onComplete: vi.fn(),
+  onError: vi.fn(),
+};
+
+describe("useBaseTool unmount behaviour", () => {
+  beforeEach(() => {
+    cancelOperation.mockClear();
+    scopedFiles.current = [];
+  });
+
+  test("aborts the in-flight operation when the tool unmounts mid-run", () => {
+    const { unmount } = renderHook(() =>
+      useBaseTool("compress", makeParams, () => makeOperation(true), props),
+    );
+
+    expect(cancelOperation).not.toHaveBeenCalled();
+    unmount();
+    expect(cancelOperation).toHaveBeenCalledTimes(1);
+  });
+
+  test("does not cancel on unmount when no operation is running", () => {
+    const { unmount } = renderHook(() =>
+      useBaseTool("compress", makeParams, () => makeOperation(false), props),
+    );
+
+    unmount();
+    expect(cancelOperation).not.toHaveBeenCalled();
+  });
+});
diff --git a/frontend/editor/src/core/hooks/tools/shared/useBaseTool.ts b/frontend/editor/src/core/hooks/tools/shared/useBaseTool.ts
index df21dc3b3b..881a20f3c8 100644
--- a/frontend/editor/src/core/hooks/tools/shared/useBaseTool.ts
+++ b/frontend/editor/src/core/hooks/tools/shared/useBaseTool.ts
@@ -80,6 +80,22 @@ export function useBaseTool<
   const params = useParams();
   const operation = useOperation();
 
+  // Abort any in-flight backend request when the tool unmounts — e.g. the user
+  // navigates away or switches tools mid-operation. Without this the request
+  // keeps running and the UI has no way to stop it. A ref keeps the cleanup
+  // pointed at the latest operation without re-subscribing on every render, and
+  // we only cancel while something is actually in flight so a normal unmount
+  // (and React strict-mode's dev remount) stays a no-op.
+  const operationRef = useRef(operation);
+  operationRef.current = operation;
+  useEffect(() => {
+    return () => {
+      if (operationRef.current.isLoading) {
+        operationRef.current.cancelOperation();
+      }
+    };
+  }, []);
+
   // Endpoint validation using parameters hook
   const { enabled: endpointEnabled, loading: endpointLoading } =
     useEndpointEnabled(params.getEndpointName());