iPhone Mirroring Hangs on 'Connecting…' — AWDL Data Stall (27.0 Beta)

Update 2026‑06‑14 — root cause refined (and what is not the cause)

Re‑investigated end‑to‑end on the same OS seed (build 26A5353q, unchanged). The original "AWDL data stall / nothing local was wrong" call was close but mis‑attributed the secondary causes. Corrected understanding below — practical outcome is unchanged: no user‑side fix, wait for a new seed.

Refined root cause — the AWDL bulk‑data path can't hold a 5 GHz channel. Pulled the iPhone's own logs over USB (sudo log collect --device --last 8m --output ~/Desktop/x.logarchive). The kernel Wi‑Fi driver (AppleBCMWLAN, wlan0:com.apple.p2p.awdl0) shows, over 8 min on infra channel 36:

isValidChannel … not match … channel 36 band 0x10 — 238× (vs 32 passes): AWDL rejects the channel for the P2P group.
Disable Steering on Timeout — 159×: can't steer to a better channel.
isInfraRealtimePacketThresholdAllowed allowed:0 — 169/451: bulk realtime packets blocked ~37 % of the time.

Net: the Mac's awdl0 carries ~90 B/s (control keepalive only; real video is hundreds of KB/s–MB/s). The feed is starved, not corrupted — "missing icons" = frame data that never arrived (zero decode/kVT errors logged).

What is NOT the cause (each tested and ruled out):

Tailscale is not a hard RF blocker. With accept‑routes on but no exit node, mirroring connects. Tailscale only intermittently breaks the control plane (QUIC endpoint binding → "Connection Interrupted"); with Tailscale off the session establishes but the bulk video still starves. So the old "disable Tailscale" step lets you connect but does not fix the video. (Mechanism is control‑plane endpoint flapping, not the RF‑layer block the original note implied.)
Not congestion. Router chanim_stats on ch36 = 90 % idle, 86 % txop, 3 % obss; Mac link −39 dBm / −94 dBm noise. Pristine.
Not the channel number — the whole UNII‑1 block is AWDL‑hostile on this seed. ch36 → starved feed (~90 B/s, glitchy). ch44 (same 36–48 block) → worse: times out before media starts (Failed to find endpoint, MediaContinuityKit.TaskTimeoutError, 0 B/s). Both fail → the validator rejects the entire UNII‑1 block, not just primary 36.
ch149 (UNII‑3) untested. It's the iPhone's preferred AWDL anchor and a different block, so it's the one channel that might work — but it's busier and the AiMesh controller resists pinning it (see infra notes). Deferred as not worth the disruption for a beta bug.

Wired workaround (works today, no AWDL): iPhone Mirroring is wireless‑only — there is no USB transport (confirmed: cable connected throughout, every attempt still used awdl0). For a wired view of the screen:

QuickTime Player → File → New Movie Recording → ⌄ next to record → select the iPhone = full‑rate USB‑C screen mirror (view + record). Does not give remote control (tap/type) — that's unique to iPhone Mirroring.

Infra notes (RT‑AX82U, AiMesh controller):

Router SSH is on port 1025 (not 22); creds in Ansible vault (router_username / router_password).
The 5 GHz channel is AiMesh‑coordinated and resists CLI changes — wl chanspec / nvram wl1_chanspec get re‑asserted by acsd2 + AiMesh within seconds, even after restart_wireless. Only setting Control Channel to an explicit value in the Web UI holds mesh‑wide. Left "Auto" → acsd2 picks 36 (the cleanest channel).
Any channel change triggers a mesh re‑sync (~1 min) that drops all Wi‑Fi; during it MajorAir falls back to the iPhone's USB Personal Hotspot (en7 / 172.20.10.x) and won't auto‑rejoin home Wi‑Fi while the hotspot feeds it internet (manual Wi‑Fi‑menu join needed).
Current state: 5 GHz on ch44/80 (same clean UNII‑1 spectrum as 36; left here to avoid another re‑sync — the Deck streams identically on 44).

Revisit checklist — when a new iOS/macOS seed ships:

Confirm the seed changed: sw_vers BuildVersion ≠ 26A5353q (both Mac and iPhone).
Tailscale off; iPhone on home Wi‑Fi, near the Mac, Personal Hotspot off.
Open iPhone Mirroring.
Measure awdl0 RX over a few seconds — target hundreds of KB/s (real video), not ~90 B/s.
Pull the iPhone log (log collect --device) and check isValidChannel now passes for the infra channel.
If still starved → no user fix; re‑file Feedback Assistant and keep waiting.

Symptom

iPhone Mirroring on the Mac sits on "Connecting…" forever and never shows the iPhone screen.

Mac: macOS 27.0 dev beta (build 26A5353q), MajorAir
iPhone: Major16Pro / iPhone17,1, iOS 27.0 dev beta, same Apple ID (maj.linux@gmail.com)

Root cause (conclusion)

A bug in the iPhone Mirroring beta (both devices on the .0 developer seeds). The connection authenticates, the AWDL peer-to-peer link comes up, the TLS handshake starts — then bidirectional data stalls ~2 seconds in and the link is torn down. Deterministic, reproduces every attempt. Nothing in the local configuration was wrong. Filed via Feedback Assistant; expected to clear in a future seed.

Two real but secondary network-layer issues were found and fixed along the way (see below) — they can block mirroring independently, but were not the cause of the final 2-second stall.

The smoking gun (unified log)

Per connection attempt the sequence is always:

rapportd: Session start … linkType "AWDL", error "NoError"      # link negotiated OK
iPhone Mirroring: Installing verify block for 1 authorized peer key(s)
boringssl: TLS client read_server_hello                          # iPhone DID respond
quic: path over awdl0 received event established / promoted to primary
nw_flow_connected: Transport protocol connected (socket)
… flow:connect_stalled @2.003s                                  # stalls exactly ~2s in
quic_conn_log_summary: Connection attempts: 6, RETRY received: no, PTOs: 5   # packets sent, zero ACKs
[C1.1.1 … awdl0 … failed socket-flow (unsatisfied (No network route))]      # link dropped (symptom, not cause)

The connection is pinned to AWDL (allowed subtypes: wifi_awdl, prohibit fallback), so once the AWDL data path stalls there is no fallback and it fails. "No network route" is the result of the teardown, not the trigger. The trigger is that after the initial handshake packets, sustained QUIC traffic over AWDL gets no ACKs (PTOs).

Investigation path (what was ruled out)

Discovery / proximity — healthy throughout. BLE + Bonjour resolve the iPhone; rapportd sees it with good RSSI, same iCloud (DF < MyiCloud >), WiFiP2P.
Tailscale (full-tunnel) — with Tailscale connected, the attempt died at "No network route" before even reaching AWDL. Cause: RouteAll: true (accept-routes / a ::/0 advertised route) installs IPv6 default routes via utun (default → fe80::%utun0..3) that black-hole the IPv6 path AWDL needs. tailscale down is NOT enough — it only sets WantRunning=false; the macOS VPN configuration (scutil --nc list showed it still Connected) and the system extension keep reasserting the routes across reboots. Must disable in System Settings → VPN.
Mullvad — mullvad-daemon running; "Local network sharing" was set to block, which blocks LAN/AWDL/multicast. Changed to allow (mullvad lan set allow). Kill-switch was off.
macOS firewall — off. No Little Snitch/LuLu app installed.
Lockdown Mode — off (iPhone).
OS-version mismatch — ruled out; both Mac and iPhone on 27.0 dev beta.
Device trust / re-pairing — there is no local pairing record on the Mac to reset. rapportd lists the iPhone as "PairedSys Conjectured" = trust is derived from the shared Apple ID, not a manual pairing. Forgetting the Mac on the iPhone does not force re-setup; the Mac just re-derives the association from iCloud and reconnects. (App containers ~/Library/Containers/com.apple.ScreenContinuity and the rapport stores held no device record; the "1 authorized peer key" lives in the protected system keychain.)
Reboots / airplane-mode toggle / Mac-side AWDL + rapportd reset — no change.

Secondary issues found & fixed (do these regardless)

Mullvad — set Local network sharing = allow (done). Required for any LAN/AWDL feature.
Tailscale — do not run full-tunnel / accept a ::/0 route while mirroring; it installs IPv6 default routes via utun that kill the local link. Toggle the VPN off in System Settings (not just tailscale down) if it ever needs to be fully out of the path.
Orphaned Little Snitch network extension — the app was uninstalled but its at.obdev.littlesnitch.networkextension is still [activated enabled] (systemextensionsctl list). Remove via System Settings → General → Login Items & Extensions → Network Extensions. A zombie filter extension with no app behind it can black-hole traffic.

Status / next steps

No user-side fix. Filed in Feedback Assistant.
Debug capture saved: ~/Desktop/iPhoneMirroring-debug-20260609-0026.txt (summary + log narrative). For a full report, trigger a sysdiagnose (⌃⌥⇧⌘ + .) right after reproducing and attach it.
VPNs restored after session: Tailscale back up; Mullvad left disconnected with LAN sharing = allow.

Useful diagnostic commands (for next time)

# Connection narrative
log show --last 10m --style compact --predicate \
  '(subsystem == "com.apple.MediaContinuityKit") OR (process == "iPhone Mirroring")' | tail -60
# rapport / AWDL negotiation
log show --last 5m --style compact --predicate 'process == "rapportd"' | grep -iE "AWDL|Pair|Session"
# VPN config really on? (CLI "down" lies)
scutil --nc list ; scutil --nc status "Tailscale"
# IPv6 default routes hijacked by utun?
netstat -rn -f inet6 | awk '$1=="default"{print}'
# Active system extensions (filters/VPNs)
systemextensionsctl list
# Mullvad LAN sharing
mullvad lan get

macos-mirrored-notification-alert-loop.md (other Continuity issue)
Hosts/VPN context: MajorTwin project doc (Tailscale tailnet, 100.x addresses)

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