Fixed SmallWebRTC data channel silently stalling on networks with a 1280-byte MTU.

env.example

@@ -214,4 +214,26 @@ WHATSAPP_PHONE_NUMBER_ID=...
 WHATSAPP_APP_SECRET=...
 
 # xAI / Grok
-XAI_API_KEY=...
+XAI_API_KEY=...
+
+# SmallWebRTC / aiortc
+#
+# PIPECAT_SCTP_MAX_CHUNK_SIZE controls the maximum SCTP DATA-chunk payload
+# size (bytes) used by aiortc's data channel. The default is 1100.
+#
+# When to change this:
+#   Lower it if the data channel silently stalls on your network. This happens
+#   when aiortc's default (1200) produces UDP datagrams larger than your path
+#   MTU: each chunk adds ~105 bytes of SCTP + DTLS + UDP + IP headers, so
+#   1200 → ~1305-byte datagrams, which exceeds the 1280-byte MTU common on
+#   IPv6 paths, Tailscale overlays, and many consumer VPNs. The kernel drops
+#   the packet with EMSGSIZE; aiortc retransmits at the same size and the
+#   channel stalls indefinitely. A value of 1100 (~1205-byte datagrams) fits
+#   any path with MTU ≥ 1210.
+#   Raise it only if you are on a controlled LAN (MTU 1500) and are sending
+#   large data-channel messages where extra fragmentation matters. Values
+#   above 1200 are unsafe on most internet paths.
+#
+# Note: this is a process-global setting (aiortc limitation) — all
+# SmallWebRTC connections in the same process share the same value.
+#PIPECAT_SCTP_MAX_CHUNK_SIZE=1100