diff --git a/src/tests/assistant-message-thinking-visibility.test.ts b/src/tests/assistant-message-thinking-visibility.test.ts
new file mode 100644
index 000000000..29fc356ee
--- /dev/null
+++ b/src/tests/assistant-message-thinking-visibility.test.ts
@@ -0,0 +1,34 @@
+// Regression test for #4181:
+// When assistant messages include both thinking + text, cap visible thinking
+// lines so question/chat text remains visible without toggling thinking off.
+import test from "node:test";
+import assert from "node:assert/strict";
+import { readFileSync } from "node:fs";
+import { join } from "node:path";
+
+const assistantMessagePath = join(
+  process.cwd(),
+  "packages",
+  "pi-coding-agent",
+  "src",
+  "modes",
+  "interactive",
+  "components",
+  "assistant-message.ts",
+);
+
+test("assistant-message caps thinking block height when text content is present", () => {
+  const src = readFileSync(assistantMessagePath, "utf-8");
+
+  assert.match(
+    src,
+    /const hasTextContent = message\.content\.some\(\(c\) => c\.type === "text" && c\.text\.trim\(\)\.length > 0\);/,
+    "assistant-message should detect text presence in mixed thinking+text messages",
+  );
+
+  assert.match(
+    src,
+    /if \(hasTextContent\)\s*\{\s*thinkingMarkdown\.maxLines = 8;\s*\}/s,
+    "assistant-message should cap visible thinking lines when assistant text also exists",
+  );
+});