diff --git a/src/config/sessions/transcript.test.ts b/src/config/sessions/transcript.test.ts
index c8d70e19ad0..ff8890d3225 100644
--- a/src/config/sessions/transcript.test.ts
+++ b/src/config/sessions/transcript.test.ts
@@ -118,6 +118,52 @@ describe("appendAssistantMessageToSessionTranscript", () => {
     expect(messageLine.message.content[0].text).toBe("Hello from delivery mirror!");
   });
 
+  it("does not append a duplicate delivery mirror when the latest assistant message already matches", async () => {
+    writeTranscriptStore();
+
+    const exactResult = await appendExactAssistantMessageToSessionTranscript({
+      sessionKey,
+      storePath: fixture.storePath(),
+      message: {
+        role: "assistant",
+        content: [{ type: "text", text: "Hello from Codex!" }],
+        api: "openai-responses",
+        provider: "codex",
+        model: "gpt-5.4",
+        usage: {
+          input: 0,
+          output: 0,
+          cacheRead: 0,
+          cacheWrite: 0,
+          totalTokens: 0,
+          cost: { input: 0, output: 0, cacheRead: 0, cacheWrite: 0, total: 0 },
+        },
+        stopReason: "stop",
+        timestamp: Date.now(),
+      },
+    });
+
+    expect(exactResult.ok).toBe(true);
+
+    const mirrorResult = await appendAssistantMessageToSessionTranscript({
+      sessionKey,
+      text: "Hello from Codex!",
+      storePath: fixture.storePath(),
+    });
+
+    expect(mirrorResult.ok).toBe(true);
+    if (exactResult.ok && mirrorResult.ok) {
+      expect(mirrorResult.messageId).toBe(exactResult.messageId);
+      const lines = fs.readFileSync(mirrorResult.sessionFile, "utf-8").trim().split("\n");
+      expect(lines.length).toBe(2);
+
+      const messageLine = JSON.parse(lines[1]);
+      expect(messageLine.message.provider).toBe("codex");
+      expect(messageLine.message.model).toBe("gpt-5.4");
+      expect(messageLine.message.content[0].text).toBe("Hello from Codex!");
+    }
+  });
+
   it("finds session entry using normalized (lowercased) key", async () => {
     const storeKey = "agent:main:bluebubbles:direct:+15551234567";
     const store = {
diff --git a/src/config/sessions/transcript.ts b/src/config/sessions/transcript.ts
index 80410dc93da..24770698174 100644
--- a/src/config/sessions/transcript.ts
+++ b/src/config/sessions/transcript.ts
@@ -201,6 +201,13 @@ export async function appendExactAssistantMessageToSessionTranscript(params: {
     return { ok: true, sessionFile, messageId: existingMessageId };
   }
 
+  const latestEquivalentAssistantId = isRedundantDeliveryMirror(params.message)
+    ? await findLatestEquivalentAssistantMessageId(sessionFile, params.message)
+    : undefined;
+  if (latestEquivalentAssistantId) {
+    return { ok: true, sessionFile, messageId: latestEquivalentAssistantId };
+  }
+
   const message = {
     ...params.message,
     ...(explicitIdempotencyKey ? { idempotencyKey: explicitIdempotencyKey } : {}),
@@ -252,3 +259,73 @@ async function transcriptHasIdempotencyKey(
   }
   return undefined;
 }
+
+function isRedundantDeliveryMirror(message: SessionTranscriptAssistantMessage): boolean {
+  return message.provider === "openclaw" && message.model === "delivery-mirror";
+}
+
+function extractAssistantMessageText(message: SessionTranscriptAssistantMessage): string | null {
+  if (typeof message.text === "string" && message.text.trim()) {
+    return message.text.trim();
+  }
+  if (!Array.isArray(message.content)) {
+    return null;
+  }
+
+  const parts = message.content
+    .filter(
+      (
+        part,
+      ): part is {
+        type: "text";
+        text: string;
+      } => part.type === "text" && typeof part.text === "string" && part.text.trim().length > 0,
+    )
+    .map((part) => part.text.trim());
+
+  return parts.length > 0 ? parts.join("\n").trim() : null;
+}
+
+async function findLatestEquivalentAssistantMessageId(
+  transcriptPath: string,
+  message: SessionTranscriptAssistantMessage,
+): Promise<string | undefined> {
+  const expectedText = extractAssistantMessageText(message);
+  if (!expectedText) {
+    return undefined;
+  }
+
+  try {
+    const raw = await fs.promises.readFile(transcriptPath, "utf-8");
+    const lines = raw.split(/\r?\n/);
+    for (let index = lines.length - 1; index >= 0; index -= 1) {
+      const line = lines[index];
+      if (!line.trim()) {
+        continue;
+      }
+      try {
+        const parsed = JSON.parse(line) as {
+          id?: unknown;
+          message?: SessionTranscriptAssistantMessage;
+        };
+        const candidate = parsed.message;
+        if (!candidate || candidate.role !== "assistant") {
+          continue;
+        }
+        const candidateText = extractAssistantMessageText(candidate);
+        if (candidateText !== expectedText) {
+          continue;
+        }
+        if (typeof parsed.id === "string" && parsed.id) {
+          return parsed.id;
+        }
+      } catch {
+        continue;
+      }
+    }
+  } catch {
+    return undefined;
+  }
+
+  return undefined;
+}