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--- a/CHANGELOG.md
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@@ -3,6 +3,12 @@
 
 ## [Unreleased]
 
+## [v0.51.548] — 2026-06-21 — Release TG (extension load diagnostics)
+
+### Added
+
+- **A read-only diagnostics endpoint that reports why an extension didn't load (#4561 follow-up).** When the extension manifest or asset URLs are configured but something isn't showing up, `GET /api/extensions/status` now reports the cause (extension dir missing/invalid, manifest rejected, an asset URL rejected for not being same-origin, final asset counts) using stable diagnostic codes and coarse sources only — it never exposes the configured filesystem path, raw environment values, or rejected URL strings. Authenticated, GET-only, and observational (it doesn't change what loads). Thanks @santastabber.
+
 ## [v0.51.547] — 2026-06-21 — Release TF (re-auth required before disabling password authentication)
 
 ### Added