diff --git a/bridges/bridge_native_rtp.c b/bridges/bridge_native_rtp.c
index a6addf2711..19c6ab525b 100644
--- a/bridges/bridge_native_rtp.c
+++ b/bridges/bridge_native_rtp.c
@@ -859,7 +859,7 @@ static struct ast_stream_topology *native_rtp_request_stream_topology_update(
 	struct ast_stream_topology *requested_topology)
 {
 	struct ast_stream *stream;
-	struct ast_format_cap *audio_formats = NULL;
+	const struct ast_format_cap *audio_formats = NULL;
 	struct ast_stream_topology *new_topology;
 	int i;
 
@@ -886,6 +886,8 @@ static struct ast_stream_topology *native_rtp_request_stream_topology_update(
 
 	if (audio_formats) {
 		for (i = 0; i < ast_stream_topology_get_count(new_topology); ++i) {
+			struct ast_format_cap *joint;
+
 			stream = ast_stream_topology_get_stream(new_topology, i);
 
 			if (ast_stream_get_type(stream) != AST_MEDIA_TYPE_AUDIO ||
@@ -893,8 +895,16 @@ static struct ast_stream_topology *native_rtp_request_stream_topology_update(
 				continue;
 			}
 
-			ast_format_cap_append_from_cap(ast_stream_get_formats(stream), audio_formats,
+			joint = ast_format_cap_alloc(AST_FORMAT_CAP_FLAG_DEFAULT);
+			if (!joint) {
+				continue;
+			}
+
+			ast_format_cap_append_from_cap(joint, ast_stream_get_formats(stream),
 				AST_MEDIA_TYPE_AUDIO);
+			ast_format_cap_append_from_cap(joint, audio_formats, AST_MEDIA_TYPE_AUDIO);
+			ast_stream_set_formats(stream, joint);
+			ao2_ref(joint, -1);
 		}
 	}
 
diff --git a/bridges/bridge_simple.c b/bridges/bridge_simple.c
index 545b3ad1cb..abda774dd5 100644
--- a/bridges/bridge_simple.c
+++ b/bridges/bridge_simple.c
@@ -63,7 +63,7 @@ static struct ast_stream_topology *simple_bridge_request_stream_topology_update(
 	struct ast_stream_topology *requested_topology)
 {
 	struct ast_stream *stream;
-	struct ast_format_cap *audio_formats = NULL;
+	const struct ast_format_cap *audio_formats = NULL;
 	struct ast_stream_topology *new_topology;
 	int i;
 
@@ -90,6 +90,8 @@ static struct ast_stream_topology *simple_bridge_request_stream_topology_update(
 
 	if (audio_formats) {
 		for (i = 0; i < ast_stream_topology_get_count(new_topology); ++i) {
+			struct ast_format_cap *joint;
+
 			stream = ast_stream_topology_get_stream(new_topology, i);
 
 			if (ast_stream_get_type(stream) != AST_MEDIA_TYPE_AUDIO ||
@@ -97,8 +99,16 @@ static struct ast_stream_topology *simple_bridge_request_stream_topology_update(
 				continue;
 			}
 
-			ast_format_cap_append_from_cap(ast_stream_get_formats(stream), audio_formats,
+			joint = ast_format_cap_alloc(AST_FORMAT_CAP_FLAG_DEFAULT);
+			if (!joint) {
+				continue;
+			}
+
+			ast_format_cap_append_from_cap(joint, ast_stream_get_formats(stream),
 				AST_MEDIA_TYPE_AUDIO);
+			ast_format_cap_append_from_cap(joint, audio_formats, AST_MEDIA_TYPE_AUDIO);
+			ast_stream_set_formats(stream, joint);
+			ao2_ref(joint, -1);
 		}
 	}
 
diff --git a/bridges/bridge_softmix.c b/bridges/bridge_softmix.c
index e1c6734966..09218ce996 100644
--- a/bridges/bridge_softmix.c
+++ b/bridges/bridge_softmix.c
@@ -2575,7 +2575,7 @@ fail:
 static int validate_stream(struct ast_test *test, struct ast_stream *stream,
 	const struct stream_parameters *params)
 {
-	struct ast_format_cap *stream_caps;
+	const struct ast_format_cap *stream_caps;
 	struct ast_format_cap *params_caps;
 
 	if (ast_stream_get_type(stream) != params->type) {
diff --git a/channels/chan_pjsip.c b/channels/chan_pjsip.c
index 5df39c3bd6..99ef6440da 100644
--- a/channels/chan_pjsip.c
+++ b/channels/chan_pjsip.c
@@ -820,7 +820,7 @@ static int is_compatible_format(struct ast_sip_session *session, struct ast_fram
 {
 	struct ast_stream_topology *topology = session->active_media_state->topology;
 	struct ast_stream *stream = ast_stream_topology_get_stream(topology, f->stream_num);
-	struct ast_format_cap *cap = ast_stream_get_formats(stream);
+	const struct ast_format_cap *cap = ast_stream_get_formats(stream);
 
 	return ast_format_cap_iscompatible_format(cap, f->subclass.format) != AST_FORMAT_CMP_NOT_EQUAL;
 }
diff --git a/channels/pjsip/dialplan_functions.c b/channels/pjsip/dialplan_functions.c
index 7cc4506a5e..2ace3ade38 100644
--- a/channels/pjsip/dialplan_functions.c
+++ b/channels/pjsip/dialplan_functions.c
@@ -1235,7 +1235,7 @@ static int media_offer_read_av(struct ast_sip_session *session, char *buf,
 	struct ast_stream_topology *topology;
 	int idx;
 	struct ast_stream *stream = NULL;
-	struct ast_format_cap *caps;
+	const struct ast_format_cap *caps;
 	size_t accum = 0;
 
 	if (session->inv_session->dlg->state == PJSIP_DIALOG_STATE_ESTABLISHED) {
@@ -1352,9 +1352,18 @@ static int media_offer_write_av(void *obj)
 	if (!stream) {
 		return 0;
 	}
-	caps = ast_stream_get_formats(stream);
+
+	caps = ast_format_cap_alloc(AST_FORMAT_CAP_FLAG_DEFAULT);
+	if (!caps) {
+		return -1;
+	}
+
+	ast_format_cap_append_from_cap(caps, ast_stream_get_formats(stream),
+		AST_MEDIA_TYPE_UNKNOWN);
 	ast_format_cap_remove_by_type(caps, data->media_type);
 	ast_format_cap_update_by_allow_disallow(caps, data->value, 1);
+	ast_stream_set_formats(stream, caps);
+	ao2_ref(caps, -1);
 
 	return 0;
 }
diff --git a/doc/UPGRADE-staging/stream_immutable_formats.txt b/doc/UPGRADE-staging/stream_immutable_formats.txt
new file mode 100644
index 0000000000..2af5d9b271
--- /dev/null
+++ b/doc/UPGRADE-staging/stream_immutable_formats.txt
@@ -0,0 +1,9 @@
+Subject: Core
+
+The streams API function ast_stream_get_formats is
+now defined as returning the format capabilities const.
+This has always been the case but was never enforced
+through the API itself. Any consumer of this API that
+is not treating the formats as immutable should update
+their code to create a new format capabilities and set
+it on the stream instead.
diff --git a/include/asterisk/stream.h b/include/asterisk/stream.h
index 17275c58ae..bbeeacb06a 100644
--- a/include/asterisk/stream.h
+++ b/include/asterisk/stream.h
@@ -164,7 +164,7 @@ void ast_stream_set_type(struct ast_stream *stream, enum ast_media_type type);
  *
  * \since 15
  */
-struct ast_format_cap *ast_stream_get_formats(const struct ast_stream *stream);
+const struct ast_format_cap *ast_stream_get_formats(const struct ast_stream *stream);
 
 /*!
  * \brief Get the count of the current negotiated formats of a stream
diff --git a/main/stream.c b/main/stream.c
index 41b7948d3f..5966a86f3a 100644
--- a/main/stream.c
+++ b/main/stream.c
@@ -108,6 +108,12 @@ struct ast_stream *ast_stream_alloc(const char *name, enum ast_media_type type)
 	stream->group = -1;
 	strcpy(stream->name, S_OR(name, "")); /* Safe */
 
+	stream->formats = ast_format_cap_alloc(AST_FORMAT_CAP_FLAG_DEFAULT);
+	if (!stream->formats) {
+		ast_free(stream);
+		return NULL;
+	}
+
 	return stream;
 }
 
@@ -179,7 +185,7 @@ void ast_stream_set_type(struct ast_stream *stream, enum ast_media_type type)
 	stream->type = type;
 }
 
-struct ast_format_cap *ast_stream_get_formats(const struct ast_stream *stream)
+const struct ast_format_cap *ast_stream_get_formats(const struct ast_stream *stream)
 {
 	ast_assert(stream != NULL);
 
diff --git a/res/res_pjsip_session.c b/res/res_pjsip_session.c
index 558e706a0b..67899e4180 100644
--- a/res/res_pjsip_session.c
+++ b/res/res_pjsip_session.c
@@ -1752,9 +1752,11 @@ static int sip_session_refresh(struct ast_sip_session *session,
 							continue;
 						} else {
 							/* However if the stream is otherwise remaining the same we can keep the formats
-							 * that exist on it already which allows media to continue to flow.
+							 * that exist on it already which allows media to continue to flow. We don't modify
+							 * the format capabilities but do need to cast it so that ao2_bump can raise the
+							 * reference count.
 							 */
-							joint_cap = ao2_bump(ast_stream_get_formats(existing_stream));
+							joint_cap = ao2_bump((struct ast_format_cap *)ast_stream_get_formats(existing_stream));
 						}
 					}
 					ast_stream_set_formats(stream, joint_cap);
diff --git a/res/res_pjsip_session/pjsip_session_caps.c b/res/res_pjsip_session/pjsip_session_caps.c
index 7aa4c1fd49..ca7ef44638 100644
--- a/res/res_pjsip_session/pjsip_session_caps.c
+++ b/res/res_pjsip_session/pjsip_session_caps.c
@@ -122,7 +122,7 @@ struct ast_stream *ast_sip_session_create_joint_call_stream(const struct ast_sip
 	struct ast_stream *remote_stream)
 {
 	struct ast_stream *joint_stream = ast_stream_clone(remote_stream, NULL);
-	struct ast_format_cap *remote = ast_stream_get_formats(remote_stream);
+	const struct ast_format_cap *remote = ast_stream_get_formats(remote_stream);
 	enum ast_media_type media_type = ast_stream_get_type(remote_stream);
 
 	struct ast_format_cap *joint = ast_sip_create_joint_call_cap(remote,