Release notes

This release introduces a new SDK preview alongside API and reliability improvements. Version 4.0.0-rc.0 of the SignalWire Browser SDK is available as a release candidate, with customers invited to test it and provide feedback ahead of the stable release. On the API side, outbound calls and messages can now carry custom_variables, making custom context — like customer IDs or workflow identifiers — available to SWML apps and status callbacks throughout the call or message lifecycle. Separately, a bug fix ensures inbound calls and faxes sent to phone numbers without a configured handler now appear in logs with a clear error, rather than failing silently, making misconfigured numbers much easier to catch.

The SWML code editor in the new dashboard now supports Messaging scripts with autocomplete, suggestions, and schema validation — bringing it to parity with the existing Voice script support. The editor auto-detects and applies the correct schema for your script type, flagging mismatches with a one-click fix so type errors get caught before they hit production (new dashboard only). Separately, the REST API now supports custom SIP headers when creating outbound calls, giving finer control over SIP-level metadata for routing, tracing, and system integration — bringing the REST API in line with the connect.headers support already available in SWML.

Assign SWML Scripts and Webhooks to phone numbers to handle inbound messages, with full scripting control. Plus an MMS error code fix and faster AI Agents page loads.

This release focuses on visibility and flexibility improvements across the dashboard and calling API. Message logs now surface error codes and messages directly in the UI, eliminating the need for a separate API call to diagnose failed messages. The Resources UI's Scripts filter has been split into dedicated SWML and CXML filters for easier script management. Additionally, dial requests to calling/calls now accept the codecs parameter as either an array or a comma-separated string, supporting PCMU, PCMA, OPUS, G729, G722, VP8, and H264.

This release adds hold music support for physical SIP endpoints. Admins can now configure a hold music URL for a SIP phone, and that audio will automatically play whenever a call to or from that endpoint is placed on hold — whether the call is inbound or outbound. This closes a gap for customers using physical SIP hardware who previously had no way to customize the hold experience at the device level.

This release deprecates the Conference Audience feature, replaces the Home Dashboard info panel with a cleaner text-based layout, and retires the Bahrain RTC POP effective March 27, 2026, with calls automatically rerouting to the nearest node.