diff --git a/src/cron/isolated-agent/delivery-dispatch.named-agent.test.ts b/src/cron/isolated-agent/delivery-dispatch.named-agent.test.ts
index 690fb711dd2..4400fcb988e 100644
--- a/src/cron/isolated-agent/delivery-dispatch.named-agent.test.ts
+++ b/src/cron/isolated-agent/delivery-dispatch.named-agent.test.ts
@@ -72,15 +72,19 @@ describe("matchesMessagingToolDeliveryTarget", () => {
       ),
     ).toBe(false);
   });
-  it("rejects when delivery has accountId but target omits it (spoof guard)", () => {
-    // Regression guard for CWE-284: an omitted target.accountId must NOT
-    // count as a wildcard match against an account-tied delivery.
+  it("matches when delivery has accountId and target omits it (tool fills accountId at exec)", () => {
+    // message-tool resolves accountId from the agent's bound account at
+    // execution time (message-tool.ts: `accountId ?? agentAccountId`), so
+    // an absent target.accountId is equivalent to the delivery's bound
+    // account. Rejecting this case caused duplicate sends for account-bound
+    // cron jobs (codex review on PR #69940). CWE-284 spoofing is still
+    // prevented by the "accountIds differ" case above.
     expect(
       matchesMessagingToolDeliveryTarget(
         { provider: "message", to: "123456" },
         { channel: "telegram", to: "123456", accountId: "bot-a" },
       ),
-    ).toBe(false);
+    ).toBe(true);
   });
 
   it("matches when delivery and target carry the same accountId", () => {
diff --git a/src/cron/isolated-agent/delivery-dispatch.ts b/src/cron/isolated-agent/delivery-dispatch.ts
index 959b354ea9e..a1bcb8ef567 100644
--- a/src/cron/isolated-agent/delivery-dispatch.ts
+++ b/src/cron/isolated-agent/delivery-dispatch.ts
@@ -80,18 +80,13 @@ export function matchesMessagingToolDeliveryTarget(
   if (provider && provider !== "message" && provider !== channel) {
     return false;
   }
-  // Strict accountId matching when the resolved delivery is tied to a specific
-  // account: require the tool-reported target to carry an equal accountId.
-  // Omitting target.accountId must NOT count as a wildcard match, otherwise a
-  // generic `message` send could spoof attribution to any bot identity in the
-  // cron delivery trace (CWE-284).
-  if (delivery.accountId) {
-    if (!target.accountId) {
-      return false;
-    }
-    if (target.accountId !== delivery.accountId) {
-      return false;
-    }
+  // CWE-284: when the tool-reported target explicitly names a different
+  // accountId than the account-bound delivery, reject so attribution cannot
+  // be spoofed to another bot identity. An omitted target.accountId is
+  // legitimate — message-tool fills accountId from the agent's bound account
+  // at exec time, which equals delivery.accountId for account-bound jobs.
+  if (delivery.accountId && target.accountId && target.accountId !== delivery.accountId) {
+    return false;
   }
   // Strip :topic:NNN from message targets and normalize Feishu/Lark prefixes on
   // both sides so cron duplicate suppression compares canonical IDs.
diff --git a/src/cron/isolated-agent/run.message-tool-policy.test.ts b/src/cron/isolated-agent/run.message-tool-policy.test.ts
index 7dd2affdd9b..877d746f5e0 100644
--- a/src/cron/isolated-agent/run.message-tool-policy.test.ts
+++ b/src/cron/isolated-agent/run.message-tool-policy.test.ts
@@ -535,10 +535,13 @@ describe("runCronIsolatedAgentTurn message tool policy", () => {
     );
   });
 
-  it("does not rewrite generic message provider when accountId is missing on tool send", async () => {
-    // Regression guard: a tool send omitting accountId must NOT be attributed
-    // to a specific account-tied delivery in the trace. Spoofing protection
-    // for CronDeliveryTrace.messageToolSentTo[i].channel (CWE-284).
+  it("rewrites generic message provider when tool send omits accountId (tool fills at exec)", async () => {
+    // message-tool resolves accountId from the agent's bound account at exec
+    // time (message-tool.ts: `accountId ?? agentAccountId`), so a tool call
+    // that omits accountId is the common path for account-bound cron jobs.
+    // The trace rewrite must still happen here, otherwise cron's
+    // delivery-suppression flag is lost and dispatchCronDelivery would
+    // double-send for account-bound jobs (codex review on PR #69940).
     mockRunCronFallbackPassthrough();
     resolveCronDeliveryPlanMock.mockReturnValue({
       requested: true,
@@ -562,6 +565,53 @@ describe("runCronIsolatedAgentTurn message tool policy", () => {
       meta: { agentMeta: { usage: { input: 10, output: 20 } } },
     });
 
+    const result = await runCronIsolatedAgentTurn({
+      ...makeParams(),
+      job: {
+        id: "message-tool-generic-target-account-default",
+        name: "Message Tool Generic Target (accountId default)",
+        schedule: { kind: "every", everyMs: 60_000 },
+        sessionTarget: "isolated",
+        payload: { kind: "agentTurn", message: "send a message" },
+        delivery: { mode: "announce", channel: "telegram", to: "123", accountId: "bot-a" },
+      } as never,
+    });
+
+    expect(result.delivery).toEqual(
+      expect.objectContaining({
+        messageToolSentTo: [{ channel: "telegram", to: "123" }],
+      }),
+    );
+  });
+
+  it("does not rewrite generic message provider when tool names a different accountId (spoof guard)", async () => {
+    // CWE-284: a tool that explicitly sets a foreign accountId must not be
+    // attributed to this account-bound delivery in the trace.
+    mockRunCronFallbackPassthrough();
+    resolveCronDeliveryPlanMock.mockReturnValue({
+      requested: true,
+      mode: "announce",
+      channel: "telegram",
+      to: "123",
+      accountId: "bot-a",
+    });
+    resolveDeliveryTargetMock.mockResolvedValue({
+      ok: true,
+      channel: "telegram",
+      to: "123",
+      accountId: "bot-a",
+      threadId: undefined,
+      mode: "explicit",
+    });
+    runEmbeddedPiAgentMock.mockResolvedValue({
+      payloads: [{ text: "sent" }],
+      didSendViaMessagingTool: true,
+      messagingToolSentTargets: [
+        { tool: "message", provider: "message", to: "123", accountId: "bot-b" },
+      ],
+      meta: { agentMeta: { usage: { input: 10, output: 20 } } },
+    });
+
     const result = await runCronIsolatedAgentTurn({
       ...makeParams(),
       job: {
@@ -576,9 +626,9 @@ describe("runCronIsolatedAgentTurn message tool policy", () => {
 
     expect(result.delivery).toEqual(
       expect.objectContaining({
-        // Channel stays as "message" because the tool-reported target did not
-        // carry an accountId matching the resolved delivery's bot-a binding.
-        messageToolSentTo: [{ channel: "message", to: "123" }],
+        // Channel stays as "message" because the tool named bot-b, which does
+        // not match the resolved delivery's bot-a binding.
+        messageToolSentTo: [{ channel: "message", to: "123", accountId: "bot-b" }],
       }),
     );
   });