bluez: fix a2dp (cherry-pick patch)

modules/desktop-common.nix

@@ -66,7 +66,26 @@
   };
 
   # cachyos kernel overlay
-  nixpkgs.overlays = [ inputs.nix-cachyos-kernel.overlays.default ];
+  nixpkgs.overlays = [
+    inputs.nix-cachyos-kernel.overlays.default
+    # bluez 5.86 reversed the profile-connect order (regression of cdcd845f87ee).
+    # Dual-role devices that advertise both AudioSource (UUID 0x110a) and
+    # AudioSink (UUID 0x110b) -- e.g. any A2DP headphone with an HFP mic, like
+    # the Bose QC 45 -- now negotiate audio-gateway first and never expose
+    # a2dp-sink, with bluetoothd reporting:
+    #   src/service.c:btd_service_connect() a2dp-sink profile connect failed
+    #   for <addr>: Device or resource busy
+    # Cherry-picks bluez/bluez@066a164 "a2dp: connect source profile after
+    # sink" (slated for 5.87). FIX: drop overlay when nixpkgs ships >= 5.87.
+    # see https://github.com/bluez/bluez/issues/1922
+    (_final: prev: {
+      bluez = prev.bluez.overrideAttrs (old: {
+        patches = (old.patches or [ ]) ++ [
+          ../patches/bluez/0001-a2dp-connect-source-after-sink.patch
+        ];
+      });
+    })
+  ];
 
   # kernel options
   boot = {

patches/bluez/0001-a2dp-connect-source-after-sink.patch

@@ -0,0 +1,32 @@
+From 066a164a524e4983b850f5659b921cb42f84a0e0 Mon Sep 17 00:00:00 2001
+From: Pauli Virtanen <pav@iki.fi>
+Date: Mon, 16 Feb 2026 18:17:08 +0200
+Subject: [PATCH] a2dp: connect source profile after sink
+
+Since cdcd845f87ee the order in which profiles with the same priority
+are connected is the same order as btd_profile_register() is called,
+instead of being the opposite order.  When initiating connections, we
+want to prefer a2dp-sink profile over a2dp-source, as connecting both at
+the same time does not work currently.
+
+Add .after_services to specify the order.
+
+Fixes: https://github.com/bluez/bluez/issues/1898
+---
+ profiles/audio/a2dp.c | 3 +++
+ 1 file changed, 3 insertions(+)
+
+diff --git a/profiles/audio/a2dp.c b/profiles/audio/a2dp.c
+index 7a37003a2b..c7e0fc75c0 100644
+--- a/profiles/audio/a2dp.c
++++ b/profiles/audio/a2dp.c
+@@ -3769,6 +3769,9 @@ static struct btd_profile a2dp_source_profile = {
+ 
+ 	.adapter_probe	= a2dp_sink_server_probe,
+ 	.adapter_remove	= a2dp_sink_server_remove,
++
++	/* Connect source after sink, to prefer sink when conflicting */
++	.after_services = BTD_PROFILE_UUID_CB(NULL, A2DP_SINK_UUID),
+ };
+ 
+ static struct btd_profile a2dp_sink_profile = {