diff --git a/app/src/components/figures/FigureCard.tsx b/app/src/components/figures/FigureCard.tsx
index aac390c..176916b 100644
--- a/app/src/components/figures/FigureCard.tsx
+++ b/app/src/components/figures/FigureCard.tsx
@@ -46,7 +46,13 @@ export function FigureCard({ figure, projectId }: FigureCardProps) {
 
     updateFigure.mutate(
       { id: figure.id, data: { styled_url: result.path, status: 'styled' } },
-      { onSuccess: () => toast.success('Styled version uploaded') },
+      {
+        onSuccess: () => toast.success('Styled version uploaded'),
+        // The file is already in storage; only this row makes it the figure's
+        // styled version. Failing quietly leaves the card showing "Upload
+        // styled" over an upload that appeared to work.
+        onError: (err) => toast.error(err.message),
+      },
     );
   }
 
diff --git a/app/src/hooks/mutations-report-failure.test.ts b/app/src/hooks/mutations-report-failure.test.ts
new file mode 100644
index 0000000..8ed2fc9
--- /dev/null
+++ b/app/src/hooks/mutations-report-failure.test.ts
@@ -0,0 +1,82 @@
+import { describe, expect, it } from 'vitest';
+import { readFileSync, readdirSync } from 'node:fs';
+import { join, relative } from 'node:path';
+import ts from 'typescript';
+
+/**
+ * Three separate saves shipped with no failure path: figure placement in the
+ * compose editor (#36), a figure's label and delete (e399f4a), and the styled
+ * upload on FigureCard. Each looked identical in the UI whether it stored the
+ * work or dropped it — the user was told nothing and lost the edit on refresh.
+ *
+ * A mutation that cannot report failure is a save the user cannot trust, so
+ * this walks every `.mutate(...)` / `.mutateAsync(...)` call site in the app
+ * and fails on any that passes no `onError`. Fixing the fourth instance by
+ * hand is what this test exists to prevent.
+ */
+describe('every mutation call site reports its failures', () => {
+  const srcDir = join(process.cwd(), 'src');
+
+  function filesUnder(dir: string): string[] {
+    return readdirSync(dir, { withFileTypes: true }).flatMap((entry) => {
+      const path = join(dir, entry.name);
+      if (entry.isDirectory()) return filesUnder(path);
+      if (!/\.tsx?$/.test(entry.name) || /\.test\.tsx?$/.test(entry.name)) return [];
+      return [path];
+    });
+  }
+
+  /** react-query takes the options object as the last argument of either call. */
+  function handlesError(call: ts.CallExpression): boolean {
+    return call.arguments.some(
+      (arg) =>
+        ts.isObjectLiteralExpression(arg) &&
+        arg.properties.some((prop) => prop.name?.getText(arg.getSourceFile()) === 'onError'),
+    );
+  }
+
+  function unhandledIn(file: string): string[] {
+    const source = ts.createSourceFile(
+      file,
+      readFileSync(file, 'utf8'),
+      ts.ScriptTarget.Latest,
+      true,
+      ts.ScriptKind.TSX,
+    );
+    const unhandled: string[] = [];
+
+    function visit(node: ts.Node) {
+      if (
+        ts.isCallExpression(node) &&
+        ts.isPropertyAccessExpression(node.expression) &&
+        (node.expression.name.text === 'mutate' || node.expression.name.text === 'mutateAsync') &&
+        !handlesError(node)
+      ) {
+        const line = source.getLineAndCharacterOfPosition(node.getStart()).line + 1;
+        unhandled.push(`${relative(srcDir, file)}:${line} ${node.expression.getText(source)}`);
+      }
+      ts.forEachChild(node, visit);
+    }
+
+    visit(source);
+    return unhandled;
+  }
+
+  const sources = filesUnder(srcDir);
+
+  it('finds the app sources', () => {
+    expect(sources.length).toBeGreaterThan(0);
+  });
+
+  it('finds the mutation call sites it is meant to guard', () => {
+    const calls = sources.flatMap((file) => {
+      const text = readFileSync(file, 'utf8');
+      return text.match(/\.mutate(Async)?\(/g) ?? [];
+    });
+    expect(calls.length).toBeGreaterThan(0);
+  });
+
+  it('leaves no mutation without an onError', () => {
+    expect(sources.flatMap(unhandledIn)).toEqual([]);
+  });
+});