harden terminal ui error states

apps/web/app/terminal.test.ts

@@ -14,6 +14,7 @@ import {
   countActiveFlowFilterGroups,
   filterOptionTapeItems,
   findAnchorRestoreIndex,
+  formatUiErrorMessage,
   formatCompactUsd,
   formatOptionContractLabel,
   flushPausableTapeData,
@@ -80,6 +81,25 @@ describe("tape status hardening", () => {
   });
 });
 
+describe("terminal error message hardening", () => {
+  it("normalizes whitespace and clamps oversized messages before rendering", () => {
+    const longMessage = `API failed\n\n${"x".repeat(320)}`;
+
+    const formatted = formatUiErrorMessage(longMessage);
+
+    expect(formatted).toHaveLength(240);
+    expect(formatted).toStartWith("API failed x");
+    expect(formatted).toEndWith("...");
+    expect(formatted).not.toContain("\n");
+  });
+
+  it("uses a fallback when an error payload is empty", () => {
+    expect(formatUiErrorMessage("   ", "Synthetic status could not be loaded")).toBe(
+      "Synthetic status could not be loaded"
+    );
+  });
+});
+
 const makeItem = (traceId: string, seq: number, ts: number) => ({
   trace_id: traceId,
   seq,