diff --git a/src/tools/call-omo-agent/sync-executor.test.ts b/src/tools/call-omo-agent/sync-executor.test.ts
index 9b8392b93..c0bb0a8d3 100644
--- a/src/tools/call-omo-agent/sync-executor.test.ts
+++ b/src/tools/call-omo-agent/sync-executor.test.ts
@@ -79,11 +79,15 @@ function createToolContext(): ToolContext {
   }
 }
 
-function createContext(promptAsync: ReturnType<typeof mock>) {
+function createContext(
+  promptAsync: ReturnType<typeof mock>,
+  status?: () => Promise<unknown>,
+) {
   return {
     client: {
       session: {
         promptAsync,
+        ...(status ? { status } : {}),
       },
     },
   }
@@ -350,6 +354,41 @@ describe("executeSync", () => {
     expect(deps.processMessages).not.toHaveBeenCalled()
   })
 
+  test("does not send a duplicate sync prompt when a reused session is active", async () => {
+    //#given
+    const executeSync = await importExecuteSync()
+    const deps = createDependencies({
+      createOrGetSession: mock(async () => ({ sessionID: "ses-active-reuse", isNew: false })),
+    })
+    const toolContext = createToolContext()
+    const recorder = createPromptAsyncRecorder()
+    const args = {
+      subagent_type: "explore",
+      description: "active reuse",
+      prompt: "find something",
+      run_in_background: false,
+      session_id: "ses-active-reuse",
+    }
+
+    //#when
+    const result = await executeSync(
+      args,
+      toolContext,
+      createContext(
+        recorder.promptAsync,
+        async () => ({ data: { "ses-active-reuse": { type: "busy" } } }),
+      ) as never,
+      deps,
+    )
+
+    //#then
+    expect(recorder.promptAsync).toHaveBeenCalledTimes(0)
+    expect(result).toContain("Error: Failed to send prompt")
+    expect(result).toContain("session_id: ses-active-reuse")
+    expect(deps.waitForCompletion).not.toHaveBeenCalled()
+    expect(deps.processMessages).not.toHaveBeenCalled()
+  })
+
   test("commits reserved descendant quota after creating a new sync session", async () => {
     //#given
     const { executeSync } = require("./sync-executor")
diff --git a/src/tools/call-omo-agent/sync-executor.ts b/src/tools/call-omo-agent/sync-executor.ts
index 31ae8beb8..85c0c6213 100644
--- a/src/tools/call-omo-agent/sync-executor.ts
+++ b/src/tools/call-omo-agent/sync-executor.ts
@@ -6,6 +6,7 @@ import { applySessionPromptParams } from "../../shared/session-prompt-params-hel
 import type { DelegatedModelConfig } from "../../shared/model-resolution-types"
 import type { FallbackEntry } from "../../shared/model-requirements"
 import { stripAgentListSortPrefix } from "../../shared/agent-display-names"
+import { promptAsyncAfterSessionIdle } from "../../hooks/shared/prompt-async-gate"
 import { waitForCompletion } from "./completion-poller"
 import { processMessages } from "./message-processor"
 import { createOrGetSession } from "./session-creator"
@@ -110,21 +111,34 @@ export async function executeSync(
         return `Error: Failed to send prompt: promptAsync is not available on this OpenCode client.\n\n<task_metadata>\nsession_id: ${sessionID}\n</task_metadata>`
       }
 
-      await ctx.client.session.promptAsync({
-        path: { id: sessionID },
-        body: {
-          agent: normalizedSubagentType,
-          tools: {
-            ...getAgentToolRestrictions(normalizedSubagentType),
-            task: false,
-            question: false,
+      const promptResult = await promptAsyncAfterSessionIdle({
+        client: ctx.client,
+        sessionID,
+        source: "call-omo-agent:sync",
+        settleMs: 0,
+        postDispatchHoldMs: 0,
+        input: {
+          path: { id: sessionID },
+          body: {
+            agent: normalizedSubagentType,
+            tools: {
+              ...getAgentToolRestrictions(normalizedSubagentType),
+              task: false,
+              question: false,
+            },
+            parts: [{ type: "text", text: args.prompt }],
+            ...(model ? { model: { providerID: model.providerID, modelID: model.modelID } } : {}),
+            ...(model?.variant ? { variant: model.variant } : {}),
+            ...buildPromptGenerationParams(model),
           },
-          parts: [{ type: "text", text: args.prompt }],
-          ...(model ? { model: { providerID: model.providerID, modelID: model.modelID } } : {}),
-          ...(model?.variant ? { variant: model.variant } : {}),
-          ...buildPromptGenerationParams(model),
         },
       })
+      if (promptResult.status === "failed") {
+        throw promptResult.error
+      }
+      if (promptResult.status !== "dispatched") {
+        throw new Error(`promptAsync skipped by gate: ${promptResult.status}`)
+      }
     } catch (error) {
       const errorMessage = error instanceof Error ? error.message : String(error)
       log(`[call_omo_agent] Prompt error:`, errorMessage)