diff --git a/doc/user/content/releases/_index.md b/doc/user/content/releases/_index.md
index c146f32eaa67d..2ba28dfa0dbdc 100644
--- a/doc/user/content/releases/_index.md
+++ b/doc/user/content/releases/_index.md
@@ -19,6 +19,16 @@ Starting with the v26.1.0 release, Materialize releases on a weekly schedule for
 both Cloud and Self-Managed. See [Release schedule](/releases/schedule) for details.
 {{</ note >}}
 
+## v26.40.1
+*Released to Materialize Cloud: 2026-09-05* <br>
+*Released to Materialize Self-Managed: 2026-09-06* <br>
+
+### Improvements {#v26.40.1-improvements}
+- **Smaller Prometheus scrape payloads**: `environmentd` no longer exports the unused `mz_timestamp_difference_for_strict_serializable_ms` metric, which accounted for roughly 7% of one large environment's `/metrics` response, and `mz_time_to_first_row_seconds` drops two sub-millisecond buckets that held 12 observations out of 16.1 million in that same environment.
+
+### Bug Fixes {#v26.40.1-bug-fixes}
+- Fixed per-cluster `mz_time_to_first_row_seconds` series accumulating indefinitely for clusters that had already been dropped, which inflated `/metrics` responses in environments with high cluster churn; these series are now reclaimed when the cluster is dropped.
+
 ## v26.40.0
 *Released to Materialize Cloud: 2026-09-02* <br>
 *Released to Materialize Self-Managed: 2026-09-03* <br>
diff --git a/doc/user/data/self_managed/self_managed_operator_compatibility.yml b/doc/user/data/self_managed/self_managed_operator_compatibility.yml
index fa91e90709909..210a2385b7a28 100644
--- a/doc/user/data/self_managed/self_managed_operator_compatibility.yml
+++ b/doc/user/data/self_managed/self_managed_operator_compatibility.yml
@@ -5,6 +5,11 @@ columns:
   - column: Release date
   - column: Notes
 rows:
+  - Materialize Operator: v26.40.1
+    orchestratord version: v26.40.1
+    environmentd version: v26.40.1
+    Release date: "2026-09-06"
+    Notes: "See [v26.40.1 release notes](/releases/#v26401)"
   - Materialize Operator: v26.40
     orchestratord version: v26.40
     environmentd version: v26.40