diff --git a/extensions/imessage/src/monitor/sanitize-outbound.test-support.ts b/extensions/imessage/src/monitor/sanitize-outbound.test-support.ts
index 977c3feb2ed8..c0aa6176f9c7 100644
--- a/extensions/imessage/src/monitor/sanitize-outbound.test-support.ts
+++ b/extensions/imessage/src/monitor/sanitize-outbound.test-support.ts
@@ -63,6 +63,39 @@ describe("sanitizeOutboundText", () => {
     expect(sanitizeOutboundText(text)).toBe("Hello\n\nWorld");
   });
 
+  it.each([
+    {
+      name: "backtick fence preserves user while stripping prose user",
+      input: "user:\n```yaml\nuser:\n  name: alice\n```",
+      expected: "```yaml\nuser:\n  name: alice\n```",
+    },
+    {
+      name: "tilde fence preserves system while stripping prose system",
+      input: "system:\n~~~yaml\nsystem:\n  enabled: true\n~~~",
+      expected: "~~~yaml\nsystem:\n  enabled: true\n~~~",
+    },
+    {
+      name: "indented code preserves assistant while stripping prose assistant",
+      input: "keep\n\nassistant:\n\n    assistant:\n    enabled: true",
+      expected: "keep\n\n    assistant:\n    enabled: true",
+    },
+    {
+      name: "unterminated fence preserves every marker family after offset shifts",
+      input: [
+        "#+#+#",
+        "assistant to=final",
+        "user:",
+        "```text",
+        "#+#+#",
+        "assistant to=tool",
+        "user:",
+      ].join("\n"),
+      expected: ["```text", "#+#+#", "assistant to=tool", "user:"].join("\n"),
+    },
+  ] as const)("$name", ({ input, expected }) => {
+    expect(sanitizeOutboundText(input)).toBe(expected);
+  });
+
   it("handles combined internal markers in one message", () => {
     const text = "<thinking>step 1</thinking>NO_REPLY +#+#+#+# assistant to=final\n\nActual reply";
     const result = sanitizeOutboundText(text);
diff --git a/extensions/imessage/src/monitor/sanitize-outbound.ts b/extensions/imessage/src/monitor/sanitize-outbound.ts
index 8d58c7efdf7f..a22468fff180 100644
--- a/extensions/imessage/src/monitor/sanitize-outbound.ts
+++ b/extensions/imessage/src/monitor/sanitize-outbound.ts
@@ -1,5 +1,9 @@
 // Imessage plugin module implements sanitize outbound behavior.
-import { sanitizeAssistantVisibleText } from "openclaw/plugin-sdk/text-chunking";
+import {
+  findCodeRegions,
+  isInsideCode,
+  sanitizeAssistantVisibleText,
+} from "openclaw/plugin-sdk/text-chunking";
 
 /**
  * Patterns that indicate assistant-internal metadata leaked into text.
@@ -11,6 +15,19 @@ const ASSISTANT_ROLE_MARKER_RE = /\bassistant\s+to\s*=\s*\w+/gi;
 // any line that merely ends with the word "user/system/assistant:" in prose.
 const ROLE_TURN_MARKER_RE = /^[ \t]*(?:user|system|assistant)\s*:\s*$/gm;
 
+/**
+ * Strip an internal-marker pattern from prose while leaving matches that fall
+ * inside a fenced/indented/inline code region untouched: there a bare `user:`
+ * mapping key or `#+#` line is the user's own content, not leaked scaffolding.
+ * Regions are recomputed per call because the prior strip shifted later offsets.
+ */
+function stripMarkerOutsideCode(text: string, marker: RegExp): string {
+  const codeRegions = findCodeRegions(text);
+  return text.replace(marker, (match, offset: number) =>
+    isInsideCode(offset, codeRegions) ? match : "",
+  );
+}
+
 /**
  * Strip all assistant-internal scaffolding from outbound text before delivery.
  * Applies reasoning/thinking tag removal, memory tag removal, and
@@ -23,9 +40,9 @@ export function sanitizeOutboundText(text: string): string {
 
   let cleaned = sanitizeAssistantVisibleText(text);
 
-  cleaned = cleaned.replace(INTERNAL_SEPARATOR_RE, "");
-  cleaned = cleaned.replace(ASSISTANT_ROLE_MARKER_RE, "");
-  cleaned = cleaned.replace(ROLE_TURN_MARKER_RE, "");
+  cleaned = stripMarkerOutsideCode(cleaned, INTERNAL_SEPARATOR_RE);
+  cleaned = stripMarkerOutsideCode(cleaned, ASSISTANT_ROLE_MARKER_RE);
+  cleaned = stripMarkerOutsideCode(cleaned, ROLE_TURN_MARKER_RE);
 
   // Collapse excessive blank lines left after stripping.
   cleaned = cleaned.replace(/\n{3,}/g, "\n\n").trim();