diff --git a/src/main/claude/claude-structured-dispatch.ts b/src/main/claude/claude-structured-dispatch.ts
index 80585df1323..c7cd733f504 100644
--- a/src/main/claude/claude-structured-dispatch.ts
+++ b/src/main/claude/claude-structured-dispatch.ts
@@ -78,11 +78,36 @@ function isClaudeUserMessageReplay(message: Record<string, unknown>): boolean {
   return message.type === 'user' && message.parent_tool_use_id === null && message.isReplay === true
 }
 
+let warnedAboutMissingReplayMarker = false
+
+/** A CLI that echoes without the marker cannot be told apart at runtime from a
+ *  turn that simply had no boundary inside the ack budget: both just report
+ *  "delivery unconfirmed". Say it once so the cause is diagnosable. */
+function warnIfEchoLacksReplayMarker(message: Record<string, unknown>): void {
+  if (
+    warnedAboutMissingReplayMarker ||
+    message.type !== 'user' ||
+    message.parent_tool_use_id !== null ||
+    message.isReplay !== undefined ||
+    message.tool_use_result !== undefined
+  ) {
+    return
+  }
+  warnedAboutMissingReplayMarker = true
+  console.warn(
+    '[claude-structured] user frame arrived without isReplay while a send was waiting; ' +
+      'sends will report delivery unconfirmed until the CLI stamps the marker'
+  )
+}
+
 export function resolveClaudeReplayWaiter(
   session: ClaudeSession,
   message: Record<string, unknown>
 ): void {
   const isUserReplay = isClaudeUserMessageReplay(message)
+  if (!isUserReplay && session.dispatchWaiters.length > 0) {
+    warnIfEchoLacksReplayMarker(message)
+  }
   const isCompletedCommand = message.type === 'result'
   if (
     (!isUserReplay && !isCompletedCommand) ||
diff --git a/src/main/claude/claude-structured-launch-resolution.test.ts b/src/main/claude/claude-structured-launch-resolution.test.ts
index e04605b4830..cb09b3a1895 100644
--- a/src/main/claude/claude-structured-launch-resolution.test.ts
+++ b/src/main/claude/claude-structured-launch-resolution.test.ts
@@ -60,6 +60,10 @@ describe('claude structured launch resolution', () => {
     expect(first.args).toContain('--setting-sources')
     expect(first.args).toContain(CLAUDE_DEFAULT_SETTING_SOURCES.join(','))
     expect(CLAUDE_STRUCTURED_BASE_ARGS).toContain('--verbose')
+    // Load-bearing: `resolveClaudeReplayWaiter` settles a send only on the
+    // `isReplay` marker this flag asks for. Drop it and every send blocks its
+    // whole ack budget and lands "delivery unconfirmed".
+    expect(CLAUDE_STRUCTURED_BASE_ARGS).toContain('--replay-user-messages')
   })
 
   it('resumes the session and leaf at the durable chain head', async () => {