diff --git a/extensions/opencode/session-catalog.test.ts b/extensions/opencode/session-catalog.test.ts
index 785d9821e853..bffa750ef465 100644
--- a/extensions/opencode/session-catalog.test.ts
+++ b/extensions/opencode/session-catalog.test.ts
@@ -86,6 +86,7 @@ function captureOpenCodeSessionRegistrations(pluginConfig: unknown = {}) {
 async function installFakeOpenCode(
   assistantText = "hi",
   sessionTitle = "Catalog session",
+  toolInput: unknown = { command: "pwd" },
 ): Promise<string> {
   const directory = await fs.mkdtemp(path.join(os.tmpdir(), "openclaw-opencode-catalog-"));
   temporaryDirectories.push(directory);
@@ -125,7 +126,7 @@ async function installFakeOpenCode(
             id: "prt_tool",
             type: "tool",
             tool: "bash",
-            state: { status: "completed", input: { command: "pwd" }, output: "/workspace" },
+            state: { status: "completed", input: toolInput, output: "/workspace" },
           },
         ],
       },
@@ -299,6 +300,25 @@ describe("OpenCode session catalog", () => {
     },
   );
 
+  it.runIf(process.platform !== "win32")(
+    "keeps truncated tool input on a valid UTF-16 boundary",
+    async () => {
+      await installFakeOpenCode("hi", "Catalog session", {
+        value: `${"x".repeat(19_989)}🎉`,
+      });
+      const transcript = await readLocalOpenCodeTranscriptPage({
+        threadId: "ses_test",
+        limit: 20,
+      });
+      const toolCall = transcript.items.find((item) => item.type === "toolCall");
+
+      expect(toolCall?.text).toMatch(/…$/u);
+      expect(toolCall?.text).not.toMatch(
+        /[\uD800-\uDBFF](?![\uDC00-\uDFFF])|(?<![\uD800-\uDBFF])[\uDC00-\uDFFF]/u,
+      );
+    },
+  );
+
   it.runIf(process.platform !== "win32")(
     "auto-detects the CLI and honors the node-local Web UI switch",
     async () => {
diff --git a/extensions/opencode/session-catalog.ts b/extensions/opencode/session-catalog.ts
index f748460018b9..c7342ef33e84 100644
--- a/extensions/opencode/session-catalog.ts
+++ b/extensions/opencode/session-catalog.ts
@@ -6,6 +6,7 @@ import type {
   SessionsCatalogReadResult,
 } from "openclaw/plugin-sdk/session-catalog";
 import { isRecord } from "openclaw/plugin-sdk/string-coerce-runtime";
+import { truncateUtf16Safe } from "openclaw/plugin-sdk/text-utility-runtime";
 import {
   materializeWindowsSpawnProgram,
   resolveWindowsSpawnProgram,
@@ -352,7 +353,7 @@ export async function listLocalOpenCodeSessionPage(value?: unknown): Promise<Ope
 function jsonText(value: unknown, maxLength = 20_000): string | undefined {
   try {
     const text = JSON.stringify(value);
-    return text.length > maxLength ? `${text.slice(0, maxLength)}…` : text;
+    return text.length > maxLength ? `${truncateUtf16Safe(text, maxLength)}…` : text;
   } catch {
     return undefined;
   }