fix: ACK-accelerated delivery — immediate on ACK, retry once, abort on double fail

Delays 1.5-2.5s (was 3-5s, only for broadcasts now).
DMs: send → ACK → next immediately. No ACK → retry once → abort.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

meshai/config.py

@@ -35,8 +35,8 @@ class ConnectionConfig:
 class ResponseConfig:
     """Response behavior settings."""
 
-    delay_min: float = 3.0
-    delay_max: float = 5.0
+    delay_min: float = 1.5
+    delay_max: float = 2.5
     max_length: int = 200
     max_messages: int = 3
 

meshai/responder.py

@@ -24,10 +24,11 @@ class Responder:
         destination: Optional[str] = None,
         channel: int = 0,
     ) -> bool:
-        """Send response messages with ACK waiting and retry.
+        """Send response messages with ACK-accelerated delivery.
 
-        For DMs: waits for ACK before sending next message, retries once on failure.
-        For broadcasts: uses delay-based pacing (no ACK for broadcasts).
+        DMs: Send -> wait for ACK -> if ACK, send next immediately.
+             If no ACK, retry once -> if still no ACK, abort.
+        Broadcasts: delay-based pacing (no ACK available).
         """
         if isinstance(messages, str):
             messages = [messages]
@@ -39,36 +40,44 @@ class Responder:
         is_dm = destination is not None
 
         for i, msg in enumerate(messages):
-            # Randomized delay before sending (except first message)
-            if i > 0:
-                delay = random.uniform(self.config.delay_min, self.config.delay_max)
-                await asyncio.sleep(delay)
-
             if is_dm and hasattr(self.connector, 'send_and_wait_ack'):
-                # DMs: send and wait for ACK
+                # Send and wait for ACK
                 ack = await asyncio.get_event_loop().run_in_executor(
                     None,
                     self.connector.send_and_wait_ack,
                     msg, destination, channel, 30.0,
                 )
 
-                if not ack:
-                    # Retry once
-                    logger.warning(f"No ACK for msg {i+1}/{len(messages)}, retrying...")
-                    await asyncio.sleep(random.uniform(3.0, 5.0))
-                    ack = await asyncio.get_event_loop().run_in_executor(
-                        None,
-                        self.connector.send_and_wait_ack,
-                        msg, destination, channel, 30.0,
-                    )
-                    if not ack:
-                        logger.error(f"No ACK after retry for msg {i+1}/{len(messages)}, skipping remaining")
-                        success = False
-                        break
+                if ack:
+                    # ACK received - next message sends immediately (no delay)
+                    logger.debug(f"ACK msg {i+1}/{len(messages)}: {msg[:50]}...")
+                    continue
+
+                # No ACK - retry same message once after short pause
+                logger.warning(f"No ACK for msg {i+1}/{len(messages)}, retrying...")
+                await asyncio.sleep(2.0)
+
+                ack = await asyncio.get_event_loop().run_in_executor(
+                    None,
+                    self.connector.send_and_wait_ack,
+                    msg, destination, channel, 30.0,
+                )
+
+                if ack:
+                    logger.debug(f"ACK on retry msg {i+1}/{len(messages)}")
+                    continue
+
+                # Double failure - abort
+                logger.error(f"No ACK after retry msg {i+1}/{len(messages)}, aborting remaining")
+                success = False
+                break
 
-                logger.debug(f"Sent+ACK msg {i+1}/{len(messages)}: {msg[:50]}...")
             else:
-                # Broadcasts or fallback: fire and delay
+                # Broadcasts or fallback: delay-based pacing
+                if i > 0:
+                    delay = random.uniform(self.config.delay_min, self.config.delay_max)
+                    await asyncio.sleep(delay)
+
                 sent = self.connector.send_message(
                     text=msg,
                     destination=destination,
@@ -82,4 +91,3 @@ class Responder:
                 logger.debug(f"Sent msg {i+1}/{len(messages)}: {msg[:50]}...")
 
         return success
-