diff --git a/api_docs/changelog.md b/api_docs/changelog.md
index 3f7a281717..d0a02c2092 100644
--- a/api_docs/changelog.md
+++ b/api_docs/changelog.md
@@ -20,6 +20,17 @@ format used by the Zulip server that they are interacting with.
 
 ## Changes in Zulip 9.0
 
+**Feature level 250**
+
+* [`GET /messages`](/api/get-messages),
+  [`GET /messages/matches_narrow`](/api/check-messages-match-narrow),
+  [`POST /messages/flags/narrow`](/api/update-message-flags-for-narrow),
+  [`POST /register`](/api/register-queue):
+  Added support for two [search/narrow filters](/api/construct-narrow)
+  related to stream messages: `channel` and `channels`. The `channel`
+  operator is an alias for the `stream` operator. The `channels`
+  operator is an alias for the `streams` operator.
+
 **Feature level 249**
 
 * [`GET /messages`](/api/get-messages), [`GET
diff --git a/api_docs/construct-narrow.md b/api_docs/construct-narrow.md
index b7d34d7f72..72c5694381 100644
--- a/api_docs/construct-narrow.md
+++ b/api_docs/construct-narrow.md
@@ -51,6 +51,13 @@ important optimization when fetching messages in certain cases (e.g.
 when [adding the `read` flag to a user's personal
 messages](/api/update-message-flags-for-narrow)).
 
+**Changes**: In Zulip 9.0 (feature level 250), support was added for
+two filters related to stream messages: `channel` and `channels`. The
+`channel` operator is an alias for the `stream` operator. The `channels`
+operator is an alias for the `streams` operator. Both `channel` and
+`channels` return the same exact results as `stream` and `streams`
+respectively.
+
 **Changes**: In Zulip 9.0 (feature level 249), narrows gained support
 for a new filter `has:reaction`. This allows clients to retrieve only
 messages that have at least one reaction.
diff --git a/zerver/openapi/zulip.yaml b/zerver/openapi/zulip.yaml
index 9359cd5ad3..e85d061980 100644
--- a/zerver/openapi/zulip.yaml
+++ b/zerver/openapi/zulip.yaml
@@ -6189,7 +6189,12 @@ paths:
             subscribed to appropriate streams or use a shared history
             search narrow with this endpoint.
 
-            **Changes**: In Zulip 9.0 (feature level 249), added new `has:reaction`
+            **Changes**: In Zulip 9.0 (feature level 250), narrows gained support
+            for two new filters related to stream messages: `channel` and `channels`;
+            which are aliases for (and return the same results as) the `stream` and
+            `streams` filters respectively.
+
+            In Zulip 9.0 (feature level 249), added new `has:reaction`
             filter, matching messages with at least one emoji reaction.
 
             In Zulip 7.0 (feature level 177), narrows gained support
@@ -7062,7 +7067,12 @@ paths:
                     optimization. Including that filter takes advantage of the fact that
                     the server has a database index for unread messages.
 
-                    **Changes**: In Zulip 9.0 (feature level 249), added new `has:reaction`
+                    **Changes**: In Zulip 9.0 (feature level 250), narrows gained support
+                    for two new filters related to stream messages: `channel` and `channels`;
+                    which are aliases for (and return the same results as) the `stream` and
+                    `streams` filters respectively.
+
+                    In Zulip 9.0 (feature level 249), added new `has:reaction`
                     filter, matching messages with at least one emoji reaction.
 
                     In Zulip 7.0 (feature level 177), narrows gained support
@@ -7489,7 +7499,12 @@ paths:
             A structure defining the narrow to check against. See how to
             [construct a narrow](/api/construct-narrow).
 
-            **Changes**: In Zulip 9.0 (feature level 249), added new `has:reaction`
+            **Changes**: In Zulip 9.0 (feature level 250), narrows gained support
+            for two new filters related to stream messages: `channel` and `channels`;
+            which are aliases for (and return the same results as) the `stream` and
+            `streams` filters respectively.
+
+            In Zulip 9.0 (feature level 249), added new `has:reaction`
             filter, matching messages with at least one emoji reaction.
 
             In Zulip 7.0 (feature level 177), narrows gained support
@@ -21368,9 +21383,12 @@ components:
         See the `all_public_streams` parameter for how to process all
         public stream messages in an organization.
 
-        Defaults to `[]`.
+        **Changes**: In Zulip 9.0 (feature level 250), narrows gained support
+        for two new filters related to stream messages: `channel` and `channels`;
+        which are aliases for (and return the same results as) the `stream` and
+        `streams` filters respectively.
 
-        **Changes**: In Zulip 9.0 (feature level 249), added new `has:reaction`
+        In Zulip 9.0 (feature level 249), added new `has:reaction`
         filter, matching messages with at least one emoji reaction.
 
         In Zulip 7.0 (feature level 177), narrows gained support