diff --git a/extensions/ollama/src/stream-runtime.test.ts b/extensions/ollama/src/stream-runtime.test.ts
index 6d8256a16fc..fd8ad1baaea 100644
--- a/extensions/ollama/src/stream-runtime.test.ts
+++ b/extensions/ollama/src/stream-runtime.test.ts
@@ -1,14 +1,23 @@
 // Ollama tests cover stream runtime plugin behavior.
 import { afterEach, describe, expect, it, vi } from "vitest";
 
-const { fetchWithSsrFGuardMock } = vi.hoisted(() => ({
+const { fetchWithSsrFGuardMock, ollamaStreamWarnMock } = vi.hoisted(() => ({
   fetchWithSsrFGuardMock: vi.fn(),
+  ollamaStreamWarnMock: vi.fn(),
 }));
 
 vi.mock("openclaw/plugin-sdk/ssrf-runtime", () => ({
   fetchWithSsrFGuard: fetchWithSsrFGuardMock,
 }));
 
+vi.mock("openclaw/plugin-sdk/runtime-env", async (importOriginal) => {
+  const actual = await importOriginal<typeof import("openclaw/plugin-sdk/runtime-env")>();
+  return {
+    ...actual,
+    createSubsystemLogger: () => ({ warn: ollamaStreamWarnMock }),
+  };
+});
+
 import {
   OLLAMA_INCOMPLETE_STREAM_ERROR,
   buildOllamaChatRequest,
@@ -73,6 +82,7 @@ function expectIteratorEvent(
 
 afterEach(() => {
   fetchWithSsrFGuardMock.mockReset();
+  ollamaStreamWarnMock.mockReset();
 });
 
 describe("buildOllamaChatRequest", () => {
@@ -1433,9 +1443,12 @@ describe("buildAssistantMessage", () => {
 });
 
 // Helper: build a ReadableStreamDefaultReader from NDJSON lines
-function mockNdjsonReader(lines: string[]): ReadableStreamDefaultReader<Uint8Array> {
+function mockNdjsonReader(
+  lines: string[],
+  options: { trailingNewline?: boolean } = {},
+): ReadableStreamDefaultReader<Uint8Array> {
   const encoder = new TextEncoder();
-  const payload = lines.join("\n") + "\n";
+  const payload = lines.join("\n") + (options.trailingNewline === false ? "" : "\n");
   let consumed = false;
   return {
     read: async () => {
@@ -1465,7 +1478,37 @@ async function expectDoneEventContent(lines: string[], expectedContent: unknown)
   });
 }
 
+async function expectNoParsedChunks(reader: ReadableStreamDefaultReader<Uint8Array>) {
+  const chunks = [];
+  for await (const chunk of parseNdjsonStream(reader)) {
+    chunks.push(chunk);
+  }
+  expect(chunks).toEqual([]);
+}
+
 describe("parseNdjsonStream", () => {
+  it("does not log a dangling surrogate for a malformed complete line", async () => {
+    const prefix = "x".repeat(119);
+    const reader = mockNdjsonReader([`${prefix}😀tail`]);
+
+    await expectNoParsedChunks(reader);
+
+    expect(ollamaStreamWarnMock).toHaveBeenCalledExactlyOnceWith(
+      `Skipping malformed NDJSON line: ${prefix}`,
+    );
+  });
+
+  it("does not log a dangling surrogate for malformed trailing data", async () => {
+    const prefix = "x".repeat(119);
+    const reader = mockNdjsonReader([`${prefix}😀tail`], { trailingNewline: false });
+
+    await expectNoParsedChunks(reader);
+
+    expect(ollamaStreamWarnMock).toHaveBeenCalledExactlyOnceWith(
+      `Skipping malformed trailing data: ${prefix}`,
+    );
+  });
+
   it("parses text-only streaming chunks", async () => {
     const reader = mockNdjsonReader([
       '{"model":"m","created_at":"t","message":{"role":"assistant","content":"Hello"},"done":false}',
diff --git a/extensions/ollama/src/stream.ts b/extensions/ollama/src/stream.ts
index 31deace2bab..13fcac565f7 100644
--- a/extensions/ollama/src/stream.ts
+++ b/extensions/ollama/src/stream.ts
@@ -36,6 +36,7 @@ import {
   normalizeLowercaseStringOrEmpty,
   readStringValue,
 } from "openclaw/plugin-sdk/string-coerce-runtime";
+import { truncateUtf16Safe } from "openclaw/plugin-sdk/text-utility-runtime";
 import { OLLAMA_DEFAULT_BASE_URL } from "./defaults.js";
 import { shouldWrapOllamaCompatMoonshotThinking } from "./model-behavior.js";
 import { normalizeOllamaWireModelId } from "./model-id.js";
@@ -52,8 +53,7 @@ import {
 const log = createSubsystemLogger("ollama-stream");
 
 export const OLLAMA_NATIVE_BASE_URL = OLLAMA_DEFAULT_BASE_URL;
-export const OLLAMA_INCOMPLETE_STREAM_ERROR =
-  "Ollama API stream ended without a final response";
+export const OLLAMA_INCOMPLETE_STREAM_ERROR = "Ollama API stream ended without a final response";
 
 const OLLAMA_STREAM_COOPERATIVE_YIELD_INTERVAL_MS = 12;
 const OLLAMA_STREAM_COOPERATIVE_YIELD_MAX_EVENTS = 64;
@@ -1067,7 +1067,7 @@ export async function* parseNdjsonStream(
       try {
         yield parseJsonPreservingUnsafeIntegers(trimmed) as OllamaChatResponse;
       } catch {
-        log.warn(`Skipping malformed NDJSON line: ${trimmed.slice(0, 120)}`);
+        log.warn(`Skipping malformed NDJSON line: ${truncateUtf16Safe(trimmed, 120)}`);
       }
     }
   }
@@ -1076,7 +1076,7 @@ export async function* parseNdjsonStream(
     try {
       yield parseJsonPreservingUnsafeIntegers(buffer.trim()) as OllamaChatResponse;
     } catch {
-      log.warn(`Skipping malformed trailing data: ${buffer.trim().slice(0, 120)}`);
+      log.warn(`Skipping malformed trailing data: ${truncateUtf16Safe(buffer.trim(), 120)}`);
     }
   }
 }