diff --git a/control_plane/src/pageserver.rs b/control_plane/src/pageserver.rs
index 6309494b71..149cfd00cb 100644
--- a/control_plane/src/pageserver.rs
+++ b/control_plane/src/pageserver.rs
@@ -370,6 +370,10 @@ impl PageServerNode {
                 .remove("evictions_low_residence_duration_metric_threshold")
                 .map(|x| x.to_string()),
         };
+
+        // If tenant ID was not specified, generate one
+        let new_tenant_id = new_tenant_id.unwrap_or(TenantId::generate());
+
         let request = models::TenantCreateRequest {
             new_tenant_id,
             config,
@@ -495,6 +499,9 @@ impl PageServerNode {
         ancestor_timeline_id: Option<TimelineId>,
         pg_version: Option<u32>,
     ) -> anyhow::Result<TimelineInfo> {
+        // If timeline ID was not specified, generate one
+        let new_timeline_id = new_timeline_id.unwrap_or(TimelineId::generate());
+
         self.http_request(
             Method::POST,
             format!("{}/tenant/{}/timeline", self.http_base_url, tenant_id),
diff --git a/docker-compose/compute_wrapper/shell/compute.sh b/docker-compose/compute_wrapper/shell/compute.sh
index cef2b485f3..22660a63ce 100755
--- a/docker-compose/compute_wrapper/shell/compute.sh
+++ b/docker-compose/compute_wrapper/shell/compute.sh
@@ -1,6 +1,14 @@
 #!/bin/bash
 set -eux
 
+# Generate a random tenant or timeline ID
+#
+# Takes a variable name as argument. The result is stored in that variable.
+generate_id() {
+    local -n resvar=$1
+    printf -v resvar '%08x%08x%08x%08x' $SRANDOM $SRANDOM $SRANDOM $SRANDOM
+}
+
 PG_VERSION=${PG_VERSION:-14}
 
 SPEC_FILE_ORG=/var/db/postgres/specs/spec.json
@@ -13,29 +21,29 @@ done
 echo "Page server is ready."
 
 echo "Create a tenant and timeline"
+generate_id tenant_id
 PARAMS=(
      -sb 
      -X POST
      -H "Content-Type: application/json"
-     -d "{}"
+     -d "{\"new_tenant_id\": \"${tenant_id}\"}"
      http://pageserver:9898/v1/tenant/
 )
-tenant_id=$(curl "${PARAMS[@]}" | sed 's/"//g')
+result=$(curl "${PARAMS[@]}")
+echo $result | jq .
 
+generate_id timeline_id
 PARAMS=(
      -sb 
      -X POST
      -H "Content-Type: application/json"
-     -d "{\"tenant_id\":\"${tenant_id}\", \"pg_version\": ${PG_VERSION}}"
+     -d "{\"new_timeline_id\": \"${timeline_id}\", \"pg_version\": ${PG_VERSION}}"
      "http://pageserver:9898/v1/tenant/${tenant_id}/timeline/"
 )
 result=$(curl "${PARAMS[@]}")
 echo $result | jq .
 
 echo "Overwrite tenant id and timeline id in spec file"
-tenant_id=$(echo ${result} | jq -r .tenant_id)
-timeline_id=$(echo ${result} | jq -r .timeline_id)
-
 sed "s/TENANT_ID/${tenant_id}/" ${SPEC_FILE_ORG} > ${SPEC_FILE}
 sed -i "s/TIMELINE_ID/${timeline_id}/" ${SPEC_FILE}
 
diff --git a/libs/pageserver_api/src/models.rs b/libs/pageserver_api/src/models.rs
index 3927ba3dad..540633d113 100644
--- a/libs/pageserver_api/src/models.rs
+++ b/libs/pageserver_api/src/models.rs
@@ -118,9 +118,8 @@ pub enum TimelineState {
 #[serde_as]
 #[derive(Serialize, Deserialize)]
 pub struct TimelineCreateRequest {
-    #[serde(default)]
-    #[serde_as(as = "Option<DisplayFromStr>")]
-    pub new_timeline_id: Option<TimelineId>,
+    #[serde_as(as = "DisplayFromStr")]
+    pub new_timeline_id: TimelineId,
     #[serde(default)]
     #[serde_as(as = "Option<DisplayFromStr>")]
     pub ancestor_timeline_id: Option<TimelineId>,
@@ -131,12 +130,11 @@ pub struct TimelineCreateRequest {
 }
 
 #[serde_as]
-#[derive(Serialize, Deserialize, Debug, Default)]
+#[derive(Serialize, Deserialize, Debug)]
 #[serde(deny_unknown_fields)]
 pub struct TenantCreateRequest {
-    #[serde(default)]
-    #[serde_as(as = "Option<DisplayFromStr>")]
-    pub new_tenant_id: Option<TenantId>,
+    #[serde_as(as = "DisplayFromStr")]
+    pub new_tenant_id: TenantId,
     #[serde(flatten)]
     pub config: TenantConfig, // as we have a flattened field, we should reject all unknown fields in it
 }
@@ -184,10 +182,10 @@ pub struct StatusResponse {
 }
 
 impl TenantCreateRequest {
-    pub fn new(new_tenant_id: Option<TenantId>) -> TenantCreateRequest {
+    pub fn new(new_tenant_id: TenantId) -> TenantCreateRequest {
         TenantCreateRequest {
             new_tenant_id,
-            ..Default::default()
+            config: TenantConfig::default(),
         }
     }
 }
diff --git a/pageserver/src/http/openapi_spec.yml b/pageserver/src/http/openapi_spec.yml
index e23d3f3a20..0d912c95e0 100644
--- a/pageserver/src/http/openapi_spec.yml
+++ b/pageserver/src/http/openapi_spec.yml
@@ -678,6 +678,8 @@ paths:
           application/json:
             schema:
               type: object
+              required:
+                - new_timeline_id
               properties:
                 new_timeline_id:
                   type: string
@@ -936,6 +938,8 @@ components:
       allOf:
         - $ref: '#/components/schemas/TenantConfig'
         - type: object
+          required:
+            - new_tenant_id
           properties:
             new_tenant_id:
               type: string
diff --git a/pageserver/src/http/routes.rs b/pageserver/src/http/routes.rs
index 25e0d88e70..30c219f773 100644
--- a/pageserver/src/http/routes.rs
+++ b/pageserver/src/http/routes.rs
@@ -301,9 +301,7 @@ async fn timeline_create_handler(mut request: Request<Body>) -> Result<Response<
     let request_data: TimelineCreateRequest = json_request(&mut request).await?;
     check_permission(&request, Some(tenant_id))?;
 
-    let new_timeline_id = request_data
-        .new_timeline_id
-        .unwrap_or_else(TimelineId::generate);
+    let new_timeline_id = request_data.new_timeline_id;
 
     let ctx = RequestContext::new(TaskKind::MgmtRequest, DownloadBehavior::Error);
 
@@ -330,7 +328,7 @@ async fn timeline_create_handler(mut request: Request<Body>) -> Result<Response<
             Err(err) => Err(ApiError::InternalServerError(err)),
         }
     }
-    .instrument(info_span!("timeline_create", tenant = %tenant_id, new_timeline = ?request_data.new_timeline_id, timeline_id = %new_timeline_id, lsn=?request_data.ancestor_start_lsn, pg_version=?request_data.pg_version))
+    .instrument(info_span!("timeline_create", tenant = %tenant_id, timeline_id = %new_timeline_id, lsn=?request_data.ancestor_start_lsn, pg_version=?request_data.pg_version))
     .await
 }
 
@@ -764,6 +762,8 @@ pub fn html_response(status: StatusCode, data: String) -> Result<Response<Body>,
 }
 
 async fn tenant_create_handler(mut request: Request<Body>) -> Result<Response<Body>, ApiError> {
+    let request_data: TenantCreateRequest = json_request(&mut request).await?;
+    let target_tenant_id = request_data.new_tenant_id;
     check_permission(&request, None)?;
 
     let _timer = STORAGE_TIME_GLOBAL
@@ -771,17 +771,10 @@ async fn tenant_create_handler(mut request: Request<Body>) -> Result<Response<Bo
         .expect("bug")
         .start_timer();
 
-    let ctx = RequestContext::new(TaskKind::MgmtRequest, DownloadBehavior::Warn);
-
-    let request_data: TenantCreateRequest = json_request(&mut request).await?;
-
     let tenant_conf =
         TenantConfOpt::try_from(&request_data.config).map_err(ApiError::BadRequest)?;
 
-    let target_tenant_id = request_data
-        .new_tenant_id
-        .map(TenantId::from)
-        .unwrap_or_else(TenantId::generate);
+    let ctx = RequestContext::new(TaskKind::MgmtRequest, DownloadBehavior::Warn);
 
     let state = get_state(&request);
 
diff --git a/test_runner/fixtures/pageserver/http.py b/test_runner/fixtures/pageserver/http.py
index 1272047881..f258a3a24d 100644
--- a/test_runner/fixtures/pageserver/http.py
+++ b/test_runner/fixtures/pageserver/http.py
@@ -155,14 +155,14 @@ class PageserverHttpClient(requests.Session):
         return res_json
 
     def tenant_create(
-        self, new_tenant_id: Optional[TenantId] = None, conf: Optional[Dict[str, Any]] = None
+        self, new_tenant_id: TenantId, conf: Optional[Dict[str, Any]] = None
     ) -> TenantId:
         if conf is not None:
             assert "new_tenant_id" not in conf.keys()
         res = self.post(
             f"http://localhost:{self.port}/v1/tenant",
             json={
-                "new_tenant_id": str(new_tenant_id) if new_tenant_id else None,
+                "new_tenant_id": str(new_tenant_id),
                 **(conf or {}),
             },
         )
@@ -293,13 +293,13 @@ class PageserverHttpClient(requests.Session):
         self,
         pg_version: PgVersion,
         tenant_id: TenantId,
-        new_timeline_id: Optional[TimelineId] = None,
+        new_timeline_id: TimelineId,
         ancestor_timeline_id: Optional[TimelineId] = None,
         ancestor_start_lsn: Optional[Lsn] = None,
         **kwargs,
     ) -> Dict[Any, Any]:
         body: Dict[str, Any] = {
-            "new_timeline_id": str(new_timeline_id) if new_timeline_id else None,
+            "new_timeline_id": str(new_timeline_id),
             "ancestor_start_lsn": str(ancestor_start_lsn) if ancestor_start_lsn else None,
             "ancestor_timeline_id": str(ancestor_timeline_id) if ancestor_timeline_id else None,
         }
diff --git a/test_runner/regress/test_auth.py b/test_runner/regress/test_auth.py
index 3e4a0bfbbb..fb79748832 100644
--- a/test_runner/regress/test_auth.py
+++ b/test_runner/regress/test_auth.py
@@ -3,7 +3,7 @@ from contextlib import closing
 import pytest
 from fixtures.neon_fixtures import NeonEnvBuilder, PgProtocol
 from fixtures.pageserver.http import PageserverApiException
-from fixtures.types import TenantId
+from fixtures.types import TenantId, TimelineId
 
 
 def test_pageserver_auth(neon_env_builder: NeonEnvBuilder):
@@ -25,21 +25,19 @@ def test_pageserver_auth(neon_env_builder: NeonEnvBuilder):
     ps.safe_psql("set FOO", password=tenant_token)
     ps.safe_psql("set FOO", password=pageserver_token)
 
-    new_timeline_id = env.neon_cli.create_branch(
-        "test_pageserver_auth", tenant_id=env.initial_tenant
-    )
-
     # tenant can create branches
     tenant_http_client.timeline_create(
         pg_version=env.pg_version,
         tenant_id=env.initial_tenant,
-        ancestor_timeline_id=new_timeline_id,
+        new_timeline_id=TimelineId.generate(),
+        ancestor_timeline_id=env.initial_timeline,
     )
     # console can create branches for tenant
     pageserver_http_client.timeline_create(
         pg_version=env.pg_version,
         tenant_id=env.initial_tenant,
-        ancestor_timeline_id=new_timeline_id,
+        new_timeline_id=TimelineId.generate(),
+        ancestor_timeline_id=env.initial_timeline,
     )
 
     # fail to create branch using token with different tenant_id
@@ -49,18 +47,19 @@ def test_pageserver_auth(neon_env_builder: NeonEnvBuilder):
         invalid_tenant_http_client.timeline_create(
             pg_version=env.pg_version,
             tenant_id=env.initial_tenant,
-            ancestor_timeline_id=new_timeline_id,
+            new_timeline_id=TimelineId.generate(),
+            ancestor_timeline_id=env.initial_timeline,
         )
 
     # create tenant using management token
-    pageserver_http_client.tenant_create()
+    pageserver_http_client.tenant_create(TenantId.generate())
 
     # fail to create tenant using tenant token
     with pytest.raises(
         PageserverApiException,
         match="Forbidden: Attempt to access management api with tenant scope. Permission denied",
     ):
-        tenant_http_client.tenant_create()
+        tenant_http_client.tenant_create(TenantId.generate())
 
 
 def test_compute_auth_to_pageserver(neon_env_builder: NeonEnvBuilder):
diff --git a/test_runner/regress/test_tenants.py b/test_runner/regress/test_tenants.py
index 5642449ce6..6599fa7ba5 100644
--- a/test_runner/regress/test_tenants.py
+++ b/test_runner/regress/test_tenants.py
@@ -314,21 +314,22 @@ def test_pageserver_with_empty_tenants(
 
     client = env.pageserver.http_client()
 
-    tenant_with_empty_timelines_dir = client.tenant_create()
-    temp_timelines = client.timeline_list(tenant_with_empty_timelines_dir)
+    tenant_with_empty_timelines = TenantId.generate()
+    client.tenant_create(tenant_with_empty_timelines)
+    temp_timelines = client.timeline_list(tenant_with_empty_timelines)
     for temp_timeline in temp_timelines:
         client.timeline_delete(
-            tenant_with_empty_timelines_dir, TimelineId(temp_timeline["timeline_id"])
+            tenant_with_empty_timelines, TimelineId(temp_timeline["timeline_id"])
         )
     files_in_timelines_dir = sum(
         1
         for _p in Path.iterdir(
-            Path(env.repo_dir) / "tenants" / str(tenant_with_empty_timelines_dir) / "timelines"
+            Path(env.repo_dir) / "tenants" / str(tenant_with_empty_timelines) / "timelines"
         )
     )
     assert (
         files_in_timelines_dir == 0
-    ), f"Tenant {tenant_with_empty_timelines_dir} should have an empty timelines/ directory"
+    ), f"Tenant {tenant_with_empty_timelines} should have an empty timelines/ directory"
 
     # Trigger timeline re-initialization after pageserver restart
     env.endpoints.stop_all()
@@ -356,15 +357,15 @@ def test_pageserver_with_empty_tenants(
 
     assert env.pageserver.log_contains(".*Setting tenant as Broken state, reason:.*")
 
-    [loaded_tenant] = [t for t in tenants if t["id"] == str(tenant_with_empty_timelines_dir)]
+    [loaded_tenant] = [t for t in tenants if t["id"] == str(tenant_with_empty_timelines)]
     assert (
         loaded_tenant["state"]["slug"] == "Active"
-    ), "Tenant {tenant_with_empty_timelines_dir} with empty timelines dir should be active and ready for timeline creation"
+    ), "Tenant {tenant_with_empty_timelines} with empty timelines dir should be active and ready for timeline creation"
 
-    loaded_tenant_status = client.tenant_status(tenant_with_empty_timelines_dir)
+    loaded_tenant_status = client.tenant_status(tenant_with_empty_timelines)
     assert (
         loaded_tenant_status["state"]["slug"] == "Active"
-    ), f"Tenant {tenant_with_empty_timelines_dir} without timelines dir should be active"
+    ), f"Tenant {tenant_with_empty_timelines} without timelines dir should be active"
 
     time.sleep(1)  # to allow metrics propagation
 
@@ -374,7 +375,7 @@ def test_pageserver_with_empty_tenants(
         "state": "Broken",
     }
     active_tenants_metric_filter = {
-        "tenant_id": str(tenant_with_empty_timelines_dir),
+        "tenant_id": str(tenant_with_empty_timelines),
         "state": "Active",
     }
 
@@ -386,7 +387,7 @@ def test_pageserver_with_empty_tenants(
 
     assert (
         tenant_active_count == 1
-    ), f"Tenant {tenant_with_empty_timelines_dir} should have metric as active"
+    ), f"Tenant {tenant_with_empty_timelines} should have metric as active"
 
     tenant_broken_count = int(
         ps_metrics.query_one(