diff --git a/app/src/components/channels/chat-messages.ts b/app/src/components/channels/chat-messages.ts
index aba4af7..fc1db77 100644
--- a/app/src/components/channels/chat-messages.ts
+++ b/app/src/components/channels/chat-messages.ts
@@ -23,6 +23,17 @@ function isToolResult(
   return message.role === "tool" && "toolCallId" in message;
 }
 
+function isTextPart(part: unknown): part is { type: "text"; text: string } {
+  return (
+    typeof part === "object" &&
+    part !== null &&
+    "type" in part &&
+    part.type === "text" &&
+    "text" in part &&
+    typeof part.text === "string"
+  );
+}
+
 export function toVisibleChatItems(
   messages: ReadonlyArray<Readonly<Message>>,
 ): VisibleChatItem[] {
@@ -62,10 +73,13 @@ export function toVisibleChatItems(
     const text =
       typeof message.content === "string"
         ? message.content
-        : message.content
-            .filter((part) => part.type === "text")
-            .map((part) => part.text)
-            .join("\n");
+        : Array.isArray(message.content)
+          ? message.content
+              .filter(isTextPart)
+              .map((part) => part.text)
+              .filter(Boolean)
+              .join("\n")
+          : "";
 
     return text ? [{ kind: "text", id: message.id, role: "user", text }] : [];
   });
diff --git a/app/tests/chat-messages.test.ts b/app/tests/chat-messages.test.ts
new file mode 100644
index 0000000..64cd9bb
--- /dev/null
+++ b/app/tests/chat-messages.test.ts
@@ -0,0 +1,137 @@
+import { describe, expect, test } from "bun:test";
+import type { Message } from "@ag-ui/core";
+import { toVisibleChatItems } from "../src/components/channels/chat-messages";
+
+describe("toVisibleChatItems", () => {
+  test("projects a user message with plain string content", () => {
+    const messages: Message[] = [
+      { id: "msg-1", role: "user", content: "Hello there" },
+    ];
+
+    expect(toVisibleChatItems(messages)).toEqual([
+      { kind: "text", id: "msg-1", role: "user", text: "Hello there" },
+    ]);
+  });
+
+  test("projects a user message with array content parts", () => {
+    const messages: Message[] = [
+      {
+        id: "msg-2",
+        role: "user",
+        content: [
+          { type: "text", text: "First line" },
+          { type: "text", text: "Second line" },
+        ],
+      },
+    ];
+
+    expect(toVisibleChatItems(messages)).toEqual([
+      {
+        kind: "text",
+        id: "msg-2",
+        role: "user",
+        text: "First line\nSecond line",
+      },
+    ]);
+  });
+
+  test("filters out non-text parts from user message array content", () => {
+    const messages: Message[] = [
+      {
+        id: "msg-3",
+        role: "user",
+        content: [
+          { type: "text", text: "Visible text" },
+          { type: "binary", mimeType: "image/png", data: "..." } as never,
+        ],
+      },
+    ];
+
+    expect(toVisibleChatItems(messages)).toEqual([
+      { kind: "text", id: "msg-3", role: "user", text: "Visible text" },
+    ]);
+  });
+
+  test("handles undefined, null, or empty content gracefully without throwing", () => {
+    const messages: Message[] = [
+      { id: "msg-4", role: "user", content: undefined as never },
+      { id: "msg-5", role: "user", content: null as never },
+      { id: "msg-6", role: "user", content: "" },
+      { id: "msg-7", role: "user", content: [] },
+    ];
+
+    expect(toVisibleChatItems(messages)).toEqual([]);
+  });
+
+  test("handles arrays containing null, undefined, or primitive items safely", () => {
+    const messages: Message[] = [
+      {
+        id: "msg-8",
+        role: "user",
+        content: [
+          null,
+          undefined,
+          "raw string item",
+          123,
+          { type: "text", text: "Valid text" },
+          { type: "text" },
+          { type: "text", text: "" },
+        ] as never,
+      },
+    ];
+
+    expect(toVisibleChatItems(messages)).toEqual([
+      { kind: "text", id: "msg-8", role: "user", text: "Valid text" },
+    ]);
+  });
+
+  test("projects assistant messages and pairs tool calls with results", () => {
+    const messages: Message[] = [
+      {
+        id: "msg-8",
+        role: "assistant",
+        content: "Let me check that for you.",
+        toolCalls: [
+          {
+            id: "call-1",
+            type: "function",
+            function: { name: "computer_read", arguments: "{}" },
+          },
+        ],
+      },
+      {
+        id: "msg-9",
+        role: "tool",
+        toolCallId: "call-1",
+        content: "Page title: Example",
+      } as Message,
+    ];
+
+    expect(toVisibleChatItems(messages)).toEqual([
+      {
+        kind: "text",
+        id: "msg-8",
+        role: "assistant",
+        text: "Let me check that for you.",
+      },
+      {
+        kind: "tool",
+        id: "call-1",
+        toolCall: {
+          id: "call-1",
+          type: "function",
+          function: { name: "computer_read", arguments: "{}" },
+        },
+        result: "Page title: Example",
+      },
+    ]);
+  });
+
+  test("ignores non-user and non-assistant messages", () => {
+    const messages: Message[] = [
+      { id: "msg-10", role: "system", content: "System prompt" } as Message,
+    ];
+
+    expect(toVisibleChatItems(messages)).toEqual([]);
+  });
+});