diff --git a/src/gateway/chat-tool-titles.test.ts b/src/gateway/chat-tool-titles.test.ts
index a2fad5649dd0..61669b42140b 100644
--- a/src/gateway/chat-tool-titles.test.ts
+++ b/src/gateway/chat-tool-titles.test.ts
@@ -133,6 +133,25 @@ describe("generateToolCallTitles", () => {
     expect(content).not.toContain(token.slice(0, 12));
   });
 
+  it("keeps bounded tool input valid before utility-model prompt construction", async () => {
+    mockPreparedModel();
+    mockCompletionTitles({ "0": "Inspected boundary input" });
+
+    await generateToolCallTitles({
+      cfg: {} satisfies OpenClawConfig,
+      agentId: AGENT_ID,
+      items: [{ id: "item-1", name: "bash", input: `${"a".repeat(1_999)}😀tail` }],
+    });
+
+    const call = completeWithPreparedSimpleCompletionModel.mock.calls[0]?.[0] as {
+      context: { messages: Array<{ content: string }> };
+    };
+    const promptPayload = JSON.parse(call.context.messages[0]?.content ?? "{}") as {
+      items?: Array<{ input?: string }>;
+    };
+    expect(promptPayload.items?.[0]?.input).toBe("a".repeat(1_999));
+  });
+
   it("serves repeated items from the SQLite cache without a second completion", async () => {
     mockPreparedModel();
     mockCompletionTitles({ "0": "Checked repo status" });
diff --git a/src/gateway/chat-tool-titles.ts b/src/gateway/chat-tool-titles.ts
index 76c7d74eaa52..4c33af9cc281 100644
--- a/src/gateway/chat-tool-titles.ts
+++ b/src/gateway/chat-tool-titles.ts
@@ -74,7 +74,7 @@ function normalizeItems(items: readonly ToolTitleRequestItem[]): ToolTitleReques
     // secret egress path. Redaction runs on the full schema-bounded input and
     // only then truncates — slicing first could bisect a secret so its
     // fragment no longer matches any redaction pattern.
-    const input = redactToolPayloadText(item.input).slice(0, TOOL_TITLE_INPUT_MAX_CHARS);
+    const input = truncateUtf16Safe(redactToolPayloadText(item.input), TOOL_TITLE_INPUT_MAX_CHARS);
     if (!id || !name || !input.trim() || seen.has(id)) {
       continue;
     }
diff --git a/ui/src/pages/chat/tool-titles.test.ts b/ui/src/pages/chat/tool-titles.test.ts
index 03b756b97894..93cf4353f494 100644
--- a/ui/src/pages/chat/tool-titles.test.ts
+++ b/ui/src/pages/chat/tool-titles.test.ts
@@ -52,6 +52,19 @@ describe("resolveToolTitleRequest", () => {
 
     expect(first?.key).toBe(second?.key);
   });
+
+  it.each([
+    ["command", "bash", { command: `${"a".repeat(1_999)}😀tail` }, "a".repeat(1_999)],
+    ["string args", "mcp__linear__create_issue", `${"a".repeat(1_999)}😀tail`, "a".repeat(1_999)],
+    [
+      "serialized object args",
+      "mcp__linear__create_issue",
+      { value: `${"a".repeat(1_989)}😀tail` },
+      '{"value":"' + "a".repeat(1_989),
+    ],
+  ])("keeps bounded %s on a valid UTF-16 boundary", (_label, name, args, expected) => {
+    expect(resolveToolTitleRequest(name, args)?.input).toBe(expected);
+  });
 });
 
 describe("getToolCallTitle", () => {
diff --git a/ui/src/pages/chat/tool-titles.ts b/ui/src/pages/chat/tool-titles.ts
index b86ab117ff03..16639f9204a1 100644
--- a/ui/src/pages/chat/tool-titles.ts
+++ b/ui/src/pages/chat/tool-titles.ts
@@ -8,6 +8,7 @@
  * labels.
  */
 
+import { truncateUtf16Safe } from "@openclaw/normalization-core/utf16-slice";
 import type { GatewayBrowserClient } from "../../api/gateway.ts";
 import { resolveToolCallKind, unwrapShellWrapperCommand } from "../../lib/chat/tool-call-view.ts";
 
@@ -68,11 +69,11 @@ function serializeArgs(args: unknown): string | null {
     return null;
   }
   if (typeof args === "string") {
-    return args.slice(0, MAX_TITLE_INPUT_CHARS);
+    return truncateUtf16Safe(args, MAX_TITLE_INPUT_CHARS);
   }
   try {
     const encoded = JSON.stringify(args);
-    return typeof encoded === "string" ? encoded.slice(0, MAX_TITLE_INPUT_CHARS) : null;
+    return typeof encoded === "string" ? truncateUtf16Safe(encoded, MAX_TITLE_INPUT_CHARS) : null;
   } catch {
     return null;
   }
@@ -98,7 +99,7 @@ export function resolveToolTitleRequest(
     if (command.length < MIN_COMMAND_CHARS_FOR_TITLE) {
       return null;
     }
-    const input = command.slice(0, MAX_TITLE_INPUT_CHARS);
+    const input = truncateUtf16Safe(command, MAX_TITLE_INPUT_CHARS);
     return { key: digest("command", input), input };
   }
   if (kind !== "generic") {