Deployments failing since ~21:49 UTC 2026-07-28: 'problems communicating with our content server' (1-file uploads and ARM reads also failing)

**Summary**: All deployments to our Static Web App fail since ~21:49 UTC today (2026-07-28) with:

> We are currently experiencing problems communicating with our content server. Please try again later or file an issue if this behavior continues.

**App**: default hostname `agreeable-bay-07c7a8910.6.azurestaticapps.net` (scale unit 6), Standard tier, custom domain, Central US.
**Example DeploymentId**: `8468890c-7466-41e9-8fbc-426df2bfb24d`

**Evidence it is service-side, not client-side** (5 independent failures, 21:49–23:12 UTC):

1. GitHub Actions with `Azure/static-web-apps-deploy@v1` (Docker / StaticSitesClient) — failed twice.
2. GitHub Actions with SWA CLI 2.0.9 (StaticSitesClient binary from Azure Front Door, 3 internal retries) — failed.
3. SWA CLI 2.0.9 from a local Windows machine (different network) — failed at "Preparing deployment".
4. **A single-file (47 byte) HTML upload to a fresh named preview environment failed identically** — rules out bundle size/content (the real bundle is only 12.2 MB / 255 files).
5. An ARM management-plane read (`az staticwebapp environment list`) returned `(GatewayTimeout) The gateway did not receive a response from 'Microsoft.Web'`.

The deployment token is valid (the CLI resolves the site and target environment before the upload step fails). Last successful deploy: 2026-07-26 07:05 UTC via the same workflow, unchanged.

Azure Service Health and status.azure.com show no active events for the subscription.

Similar recent reports: #1772 / #1773 / #1774 (July 21), #1777 (July 23).

Is there an ongoing incident affecting content-server uploads (scale unit 6 / Central US)?

No repository file or test is named. Start by reviewing the Azure/static-web-apps-deploy@v1 and SWA CLI 2.0.9 deployment attempts, then reproduce the management-plane check with `az staticwebapp environment list`; done means establishing whether scale unit 6/Central US has a service incident and recording a confirmed resolution.

Written by the indexing model from the issue text.