diff --git a/src/sandbox/index.test.ts b/src/sandbox/index.test.ts
index 7546870..504bd4f 100644
--- a/src/sandbox/index.test.ts
+++ b/src/sandbox/index.test.ts
@@ -445,6 +445,7 @@ describe('streamSandboxPrompt seam', () => {
       harness: 'opencode',
       effort: 'high',
       history: [{ role: 'assistant', content: 'prior' }],
+      requireVisibleAssistantOutput: true,
     })) {
       out.push(e)
     }
@@ -460,6 +461,7 @@ describe('streamSandboxPrompt seam', () => {
       baseUrl: 'https://router',
     })
     expect(opts.backend.profile.extensions.opencode.reasoningEffort).toBe('high')
+    expect(opts.requireVisibleAssistantOutput).toBe(true)
   })
 
   it('omits the model when provider resolution yields nothing', async () => {
diff --git a/src/sandbox/index.ts b/src/sandbox/index.ts
index e1ea10d..5265a4f 100644
--- a/src/sandbox/index.ts
+++ b/src/sandbox/index.ts
@@ -1504,6 +1504,7 @@ export interface StreamSandboxPromptOptions {
   extraMcp?: Record<string, AgentProfileMcpServer>
   signal?: AbortSignal
   timeoutMs?: number
+  requireVisibleAssistantOutput?: boolean
   // When true, an interactive question event throws instead of yielding —
   // detached (cron/mission-step) runs have no consumer to answer it.
   disallowQuestions?: boolean
@@ -1542,6 +1543,9 @@ export async function* streamSandboxPrompt(
     lastEventId: options?.lastEventId,
     ...(options?.signal ? { signal: options.signal } : {}),
     ...(options?.timeoutMs !== undefined ? { timeoutMs: options.timeoutMs } : {}),
+    ...(options?.requireVisibleAssistantOutput !== undefined
+      ? { requireVisibleAssistantOutput: options.requireVisibleAssistantOutput }
+      : {}),
     backend: {
       type: harness,
       profile: profileWithEffort,