From e1b532d48afa1713946977e821ffc84ec72881d8 Mon Sep 17 00:00:00 2001
From: James Smith <jsmith@Jamess-MacBook-Pro.local>
Date: Wed, 18 Mar 2026 20:40:15 +0000
Subject: [PATCH] Fix SSE first-byte delay in ADS-B and controller streams;
 harden WebSocket init

- Add immediate keepalive to /adsb/stream generator so the Werkzeug dev
  server flushes response headers immediately on tracking start, preventing
  the 30-second delay before the aircraft map begins receiving data
- Same fix for /controller/stream/all used by the ADSB dashboard in agent mode
- Widen WebSocket init exception guards in app.py from ImportError to
  Exception so any startup failure (e.g. RuntimeError from flask-sock on
  an unsupported WSGI server) is caught instead of propagating

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
---
 app.py               | 10 +++++-----
 routes/adsb.py       |  3 +++
 routes/controller.py |  1 +
 3 files changed, 9 insertions(+), 5 deletions(-)

diff --git a/app.py b/app.py
index 7a8f61d..c9a6550 100644
--- a/app.py
+++ b/app.py
@@ -1128,35 +1128,35 @@ def _init_app() -> None:
     try:
         from routes.audio_websocket import init_audio_websocket
         init_audio_websocket(app)
-    except ImportError:
+    except Exception:
         pass
 
     # Initialize KiwiSDR WebSocket audio proxy
     try:
         from routes.websdr import init_websdr_audio
         init_websdr_audio(app)
-    except ImportError:
+    except Exception:
         pass
 
     # Initialize WebSocket for waterfall streaming
     try:
         from routes.waterfall_websocket import init_waterfall_websocket
         init_waterfall_websocket(app)
-    except ImportError:
+    except Exception:
         pass
 
     # Initialize WebSocket for meteor scatter monitoring
     try:
         from routes.meteor_websocket import init_meteor_websocket
         init_meteor_websocket(app)
-    except ImportError:
+    except Exception:
         pass
 
     # Initialize WebSocket for ground station live waterfall
     try:
         from routes.ground_station import init_ground_station_websocket
         init_ground_station_websocket(app)
-    except ImportError:
+    except Exception:
         pass
 
     # Defer heavy/network operations so the worker can serve requests immediately
diff --git a/routes/adsb.py b/routes/adsb.py
index 3b7d8c9..710db27 100644
--- a/routes/adsb.py
+++ b/routes/adsb.py
@@ -1167,6 +1167,9 @@ def stream_adsb():
 
     def generate():
         last_keepalive = time.time()
+        # Send immediate keepalive so Werkzeug dev server flushes response
+        # headers right away (it buffers until first body byte is written).
+        yield format_sse({'type': 'keepalive'})
 
         try:
             while True:
diff --git a/routes/controller.py b/routes/controller.py
index 8d0a9a0..166e312 100644
--- a/routes/controller.py
+++ b/routes/controller.py
@@ -673,6 +673,7 @@ def stream_all_agents():
     def generate() -> Generator[str, None, None]:
         last_keepalive = time.time()
         keepalive_interval = 30.0
+        yield format_sse({'type': 'keepalive'})
 
         try:
             while True: