fix: font stack, sparklines, and DA1 response issues

- Restore terminal.options.fontFamily assignment for proper font stack handling
- Add dynamic service registration to DockerStatsCollector for docker watch mode
- Remove force_redraw on reconnect that caused DA1 responses to display as text

src/webterm/docker_stats.py

@@ -49,6 +49,9 @@ class DockerStatsCollector:
         self._task: asyncio.Task | None = None
         # Track previous CPU values for delta calculation
         self._prev_cpu: dict[str, tuple[int, int]] = {}
+        # Service names to poll (can be modified dynamically)
+        self._service_names: list[str] = []
+        self._service_names_lock = asyncio.Lock()
 
     @property
     def available(self) -> bool:
@@ -248,7 +251,7 @@ class DockerStatsCollector:
                 self._cpu_history[service_name] = deque(maxlen=STATS_HISTORY_SIZE)
             self._cpu_history[service_name].append(cpu_percent)
 
-    async def _poll_loop(self, service_names: list[str]) -> None:
+    async def _poll_loop(self) -> None:
         """Background polling loop."""
         # Discover container IDs on first run and periodically refresh
         service_to_container: dict[str, str] = {}
@@ -256,10 +259,14 @@ class DockerStatsCollector:
         warned_no_containers = False
 
         while self._running:
+            # Get current service names (may change dynamically)
+            service_names = list(self._service_names)
+
             # Refresh container mapping every 30 iterations (~5 minutes at 10s interval)
-            if refresh_counter % 30 == 0:
+            # or immediately if service list changed
+            if refresh_counter % 30 == 0 or set(service_to_container.keys()) != set(service_names):
                 service_to_container = await self._discover_containers(service_names)
-                if not service_to_container and not warned_no_containers:
+                if not service_to_container and service_names and not warned_no_containers:
                     log.warning(
                         "No Docker containers found for CPU stats. "
                         "Ensure Docker socket is mounted (-v /var/run/docker.sock:/var/run/docker.sock)"
@@ -290,10 +297,30 @@ class DockerStatsCollector:
         if self._running:
             return
 
+        self._service_names = list(service_names)
         self._running = True
-        self._task = asyncio.create_task(self._poll_loop(service_names))
+        self._task = asyncio.create_task(self._poll_loop())
         log.info("Started Docker stats collection for %d services", len(service_names))
 
+    def add_service(self, service_name: str) -> None:
+        """Add a service to the polling list dynamically.
+
+        This is safe to call while the collector is running - the poll loop
+        will pick up the new service on its next container discovery cycle.
+        """
+        if service_name not in self._service_names:
+            self._service_names.append(service_name)
+            log.debug("Added service to stats collector: %s", service_name)
+
+    def remove_service(self, service_name: str) -> None:
+        """Remove a service from the polling list."""
+        if service_name in self._service_names:
+            self._service_names.remove(service_name)
+            # Clean up history for removed service
+            self._cpu_history.pop(service_name, None)
+            self._prev_cpu.pop(service_name, None)
+            log.debug("Removed service from stats collector: %s", service_name)
+
     async def stop(self) -> None:
         """Stop collecting stats."""
         self._running = False

src/webterm/local_server.py

@@ -35,7 +35,6 @@ DEFAULT_TERMINAL_SIZE = (132, 45)
 
 SCREENSHOT_CACHE_SECONDS = 0.3
 SCREENSHOT_MAX_CACHE_SECONDS = 20.0
-CLEAR_AND_REDRAW_SEQ = "\x1b[2J\x1b[H\x1b[3J"  # Clear screen and scrollback, move to home
 
 
 WEBTERM_STATIC_PATH = Path(__file__).parent / "static"
@@ -361,8 +360,10 @@ class LocalServer:
         """Callback when a Docker container is added."""
         log.info("Container added to dashboard: %s -> %s", name, slug)
         # Update slug-to-service mapping for sparklines
-        if self._docker_stats:
         self._slug_to_service[slug] = name
+        # Register new service with stats collector so it starts polling
+        if self._docker_stats:
+            self._docker_stats.add_service(name)
             log.debug("Added sparkline mapping: %s -> %s", slug, name)
         # Notify SSE subscribers about dashboard change
         self._notify_activity("__dashboard__")
@@ -370,9 +371,10 @@ class LocalServer:
     def _on_docker_container_removed(self, slug: str) -> None:
         """Callback when a Docker container is removed."""
         log.info("Container removed from dashboard: %s", slug)
-        # Remove slug-to-service mapping
-        if self._docker_stats and slug in self._slug_to_service:
-            del self._slug_to_service[slug]
+        # Remove from stats collector and slug mapping
+        service_name = self._slug_to_service.pop(slug, None)
+        if self._docker_stats and service_name:
+            self._docker_stats.remove_service(service_name)
         # Invalidate any cached screenshots
         self._screenshot_cache.pop(slug, None)
         self._screenshot_cache_etag.pop(slug, None)
@@ -450,12 +452,6 @@ class LocalServer:
                 self.session_manager.on_session_end(session_id)
                 session_id = None
                 session = None
-            else:
-                # Force terminal redraw on reconnect to avoid blank screen
-                if hasattr(session, "force_redraw"):
-                    await session.force_redraw()
-                if hasattr(session, "send_bytes"):
-                    await session.send_bytes(CLEAR_AND_REDRAW_SEQ.encode("utf-8"))
 
         session_created = session_id is not None
 

src/webterm/static/js/terminal.ts

@@ -515,7 +515,12 @@ class WebTerminal {
     // Wait for fonts to load before fitting to ensure correct measurements
     this.waitForFonts().then(() => {
       console.log("[webterm:init] Fonts loaded, reapplying font family and fitting...");
-      // Use renderer's setFontFamily method to properly update fonts
+      // IMPORTANT: Font updates require BOTH steps to work correctly:
+      // 1. Set terminal.options.fontFamily - stores the font stack for future reference
+      // 2. Call renderer.setFontFamily() + remeasureFont() - applies the font and recalculates metrics
+      // Without step 1, the font stack is lost and defaults are used on re-render.
+      // Without step 2, the renderer doesn't know about the new fonts.
+      this.terminal.options.fontFamily = this.fontFamily;
       const renderer = (this.terminal as unknown as { renderer?: { setFontFamily: (family: string) => void; remeasureFont: () => void } }).renderer;
       if (renderer) {
         renderer.setFontFamily(this.fontFamily);

tests/test_docker_stats.py

@@ -168,6 +168,35 @@ class TestDockerStatsCollector:
 
         assert len(collector._cpu_history["test"]) == STATS_HISTORY_SIZE
 
+    def test_add_service_dynamic(self):
+        """Services can be added dynamically after start."""
+        collector = DockerStatsCollector("/nonexistent")
+        collector._service_names = ["svc1"]
+        
+        collector.add_service("svc2")
+        assert "svc2" in collector._service_names
+        
+        # Adding same service again is a no-op
+        collector.add_service("svc2")
+        assert collector._service_names.count("svc2") == 1
+
+    def test_remove_service_dynamic(self):
+        """Services can be removed dynamically."""
+        from collections import deque
+        
+        collector = DockerStatsCollector("/nonexistent")
+        collector._service_names = ["svc1", "svc2"]
+        collector._cpu_history["svc1"] = deque([10.0, 20.0])
+        collector._prev_cpu["svc1"] = (100, 200)
+        
+        collector.remove_service("svc1")
+        assert "svc1" not in collector._service_names
+        assert "svc1" not in collector._cpu_history
+        assert "svc1" not in collector._prev_cpu
+        
+        # Removing non-existent service is safe
+        collector.remove_service("nonexistent")  # Should not raise
+
 
 class TestLocalServerSparklineEndpoint:
     """Tests for the CPU sparkline endpoint in LocalServer."""

tests/test_local_server_websocket_integration.py

@@ -81,19 +81,12 @@ async def test_websocket_creates_session_on_resize(tmp_path):
         await client.close()
 
     assert created["args"] == ("test", 90, 25)
-    # Reconnect should trigger redraw without creating a new session
-    called = {"redraw": 0, "stdin": 0}
+    # Reconnect to an existing session should reuse it and send replay buffer
 
     class DummySession:
         def is_running(self):
             return True
 
-        async def force_redraw(self):
-            called["redraw"] += 1
-
-        async def send_bytes(self, data: bytes):
-            called["stdin"] += 1
-
     server.session_manager.routes["test"] = "sid"
     server.session_manager.sessions["sid"] = DummySession()
 
@@ -111,9 +104,6 @@ async def test_websocket_creates_session_on_resize(tmp_path):
     finally:
         await client.close()
 
-    assert called["redraw"] == 1
-    assert called["stdin"] == 1
-
 
 @pytest.mark.asyncio
 async def test_websocket_ping_pong(tmp_path):