diff --git a/qa/scenarios/channels/approve-command-prototype-decision-usage.yaml b/qa/scenarios/channels/approve-command-prototype-decision-usage.yaml
new file mode 100644
index 000000000000..78a5e2063948
--- /dev/null
+++ b/qa/scenarios/channels/approve-command-prototype-decision-usage.yaml
@@ -0,0 +1,89 @@
+title: Approve command rejects Object.prototype names as decisions
+
+scenario:
+  id: approve-command-prototype-decision-usage
+  surface: channels
+  category: channels.channel-actions-commands-and-approvals
+  coverage:
+    primary:
+      - channels.channel-native-commands
+  regressionRefs:
+    - openclaw/openclaw#137877
+  objective: Verify a chat /approve whose decision token is an inherited Object.prototype name gets the usage reply instead of being submitted as a decision.
+  successCriteria:
+    - Sending /approve abc constructor replies with the /approve usage text.
+    - The usage reply is produced without a model request.
+    - Sending /approve abc deny still reaches the Gateway approval resolver.
+  docsRefs:
+    - docs/channels/qa-channel.md
+  codeRefs:
+    - src/auto-reply/reply/commands-approve.ts
+    - src/auto-reply/reply/fast-approve.ts
+  execution:
+    kind: flow
+    summary: Send /approve with a prototype-name decision over a DM and verify the usage reply, then send a real decision and verify it is submitted.
+    config:
+      conversationId: approve-prototype-dm
+      prototypeCommandText: /approve abc constructor
+      realCommandText: /approve abc deny
+      usageNeedle: "Usage: /approve"
+
+flow:
+  steps:
+    - name: prototype decision name gets the usage reply
+      actions:
+        - call: waitForGatewayHealthy
+          args: [{ ref: env }, 60000]
+        - call: waitForTransportReady
+          args: [{ ref: env }, 60000]
+        - resetTransport: true
+        - set: requestCursorBefore
+          value:
+            expr: "env.mock ? (await fetchJson(`${env.mock.baseUrl}/debug/request-cursor`)).cursor : 0"
+        - set: startIndex
+          value:
+            expr: "state.getSnapshot().messages.filter((message) => message.direction === 'outbound').length"
+        - sendInbound:
+            conversation: { id: { ref: config.conversationId }, kind: direct }
+            senderId: qa-approver
+            senderName: QA Approver
+            text: { ref: config.prototypeCommandText }
+        - waitForOutbound:
+            conversation: { id: { ref: config.conversationId }, kind: direct }
+            sinceIndex: { ref: startIndex }
+            timeoutMs: 60000
+          saveAs: reply
+        - assert:
+            expr: "reply.text.includes(config.usageNeedle)"
+            message:
+              expr: "`prototype decision was not rejected with usage: ${reply.text}`"
+        - set: scenarioRequests
+          value:
+            expr: "env.mock ? await fetchJson(`${env.mock.baseUrl}/debug/requests?after=${requestCursorBefore}`) : []"
+        - assert:
+            expr: "!env.mock || scenarioRequests.length === 0"
+            message:
+              expr: "`/approve usage reply unexpectedly invoked the model ${String(scenarioRequests.length)} time(s)`"
+      detailsExpr: reply.text
+
+    - name: real decision still reaches the approval resolver
+      actions:
+        - set: realStartIndex
+          value:
+            expr: "state.getSnapshot().messages.filter((message) => message.direction === 'outbound').length"
+        - sendInbound:
+            conversation: { id: { ref: config.conversationId }, kind: direct }
+            senderId: qa-approver
+            senderName: QA Approver
+            text: { ref: config.realCommandText }
+        - waitForOutbound:
+            conversation: { id: { ref: config.conversationId }, kind: direct }
+            sinceIndex: { ref: realStartIndex }
+            textIncludes: Failed to submit approval
+            timeoutMs: 60000
+          saveAs: realReply
+        - assert:
+            expr: "!realReply.text.includes(config.usageNeedle)"
+            message:
+              expr: "`real decision was rejected as usage: ${realReply.text}`"
+      detailsExpr: "formatTransportTranscript(state, { conversationId: config.conversationId })"
diff --git a/src/auto-reply/reply/commands-approve.test.ts b/src/auto-reply/reply/commands-approve.test.ts
index 6af1679e0576..81f7a96840cf 100644
--- a/src/auto-reply/reply/commands-approve.test.ts
+++ b/src/auto-reply/reply/commands-approve.test.ts
@@ -223,6 +223,36 @@ describe("handleApproveCommand", () => {
     expect(result?.reply?.text).toContain("Usage: /approve");
   });
 
+  it.each(["constructor", "__proto__", "toString", "valueOf"])(
+    "rejects Object.prototype decision %s instead of treating it as an approval decision",
+    async (decision) => {
+      const result = await handleApproveCommand(
+        buildApproveParams(`/approve abc ${decision}`, {
+          commands: { text: true },
+          channels: { whatsapp: { allowFrom: ["*"] } },
+        } as OpenClawConfig),
+        true,
+      );
+      expect(result?.shouldContinue).toBe(false);
+      expect(result?.reply?.text).toContain("Usage: /approve");
+      expect(resolveApprovalOverGatewayMock).not.toHaveBeenCalled();
+    },
+  );
+
+  it("still accepts a real own-key decision after prototype names are rejected", async () => {
+    resolveApprovalOverGatewayMock.mockResolvedValue(undefined);
+    const result = await handleApproveCommand(
+      buildApproveParams("/approve abc deny", {
+        commands: { text: true },
+        channels: { whatsapp: { allowFrom: ["*"] } },
+      } as OpenClawConfig),
+      true,
+    );
+    expect(result?.shouldContinue).toBe(false);
+    expect(result?.reply?.text).toContain("Approval deny submitted");
+    expectApprovalResolverCall({ method: "exec.approval.resolve", id: "abc", decision: "deny" });
+  });
+
   it.each([
     {
       name: "submits approval",
diff --git a/src/auto-reply/reply/commands-approve.ts b/src/auto-reply/reply/commands-approve.ts
index 372c61d9c0f2..ac1d64cdfa2d 100644
--- a/src/auto-reply/reply/commands-approve.ts
+++ b/src/auto-reply/reply/commands-approve.ts
@@ -59,17 +59,25 @@ function parseApproveCommand(raw: string): ParsedApproveCommand | null {
   const first = normalizeLowercaseStringOrEmpty(tokens[0]);
   const second = normalizeLowercaseStringOrEmpty(tokens[1]);
 
-  if (DECISION_ALIASES[first]) {
+  // Decision tokens are chat-supplied, so inherited keys such as "constructor"
+  // or "__proto__" must not read through to Object.prototype.
+  const firstDecision = Object.hasOwn(DECISION_ALIASES, first)
+    ? DECISION_ALIASES[first]
+    : undefined;
+  if (firstDecision) {
     return {
       ok: true,
-      decision: DECISION_ALIASES[first],
+      decision: firstDecision,
       id: tokens.slice(1).join(" ").trim(),
     };
   }
-  if (DECISION_ALIASES[second]) {
+  const secondDecision = Object.hasOwn(DECISION_ALIASES, second)
+    ? DECISION_ALIASES[second]
+    : undefined;
+  if (secondDecision) {
     return {
       ok: true,
-      decision: DECISION_ALIASES[second],
+      decision: secondDecision,
       id: expectDefined(tokens[0], "tokens entry at 0"),
     };
   }