Government cloud configuration

No endpoint is hardcoded. The Settings → "Cloud environment" selector maps:

Environment	Graph host	Sign-in authority
Commercial	`https://graph.microsoft.com`	`https://login.microsoftonline.com`
GCC	`https://graph.microsoft.com`	`https://login.microsoftonline.com`
GCC High	`https://graph.microsoft.us`	`https://login.microsoftonline.us`
DoD	`https://dod-graph.microsoft.us`	`https://login.microsoftonline.us`

Notes:

GCC runs on the commercial endpoints (it is a compliance boundary, not an endpoint boundary); GCC High and DoD use the .us sovereign endpoints.
For GCC High/DoD the Entra app registration must exist in (or be consented into) the sovereign tenant; SPA redirect URIs are cloud-agnostic (GitHub Pages), but agencies that disallow external hosting can serve the static files from any internal HTTPS host — update the manifest URLs, nothing else changes (there is no backend).
Teams tag mention support and Graph feature parity can lag in sovereign clouds; if mentions with mentioned.tag is rejected, the post still succeeds without the mention and the audit row records the response.