diff --git a/src/broker/broker.c b/src/broker/broker.c
index 031e7fbd333b..528d186f8cc8 100644
--- a/src/broker/broker.c
+++ b/src/broker/broker.c
@@ -112,6 +112,8 @@ static int handle_event (broker_ctx_t *ctx, const flux_msg_t *msg);
 
 static void init_attrs (attr_t *attrs, pid_t pid, struct flux_msg_cred *cred);
 
+static void init_attrs_post_boot (attr_t *attrs);
+
 static void init_attrs_starttime (attr_t *attrs, double starttime);
 
 static int init_local_uri_attr (struct overlay *ov, attr_t *attrs);
@@ -365,6 +367,8 @@ int main (int argc, char *argv[])
         }
     }
 
+    init_attrs_post_boot (ctx.attrs);
+
     ctx.rank = overlay_get_rank (ctx.overlay);
     ctx.size = overlay_get_size (ctx.overlay);
 
@@ -601,15 +605,27 @@ static void init_attrs_starttime (attr_t *attrs, double starttime)
         log_err_exit ("error setting broker.starttime attribute");
 }
 
-static void init_attrs (attr_t *attrs, pid_t pid, struct flux_msg_cred *cred)
+/* Initialize attributes after bootstrap since these attributes may depend
+ * on whether this instance is a job or not.
+ */
+static void init_attrs_post_boot (attr_t *attrs)
 {
     const char *val;
+    bool instance_is_job;
+
+    /* Use the jobid attribute instead of FLUX_JOB_ID in the current
+     * environment to determine if this instance was run as a job. This
+     * is because the jobid attribute is only set by PMI, whereas
+     * FLUX_JOB_ID could leak from the calling environment, e.g.
+     * `flux run flux start --test-size=2`.
+     */
+    instance_is_job = attr_get (attrs, "jobid", NULL, NULL) == 0;
 
     /* Set the parent-uri attribute IFF this instance was run as a job
      * in the enclosing instance.  "parent" in this context reflects
      * a hierarchy of resource allocation.
      */
-    if (getenv ("FLUX_JOB_ID"))
+    if (instance_is_job)
         val = getenv ("FLUX_URI");
     else
         val = NULL;
@@ -622,11 +638,16 @@ static void init_attrs (attr_t *attrs, pid_t pid, struct flux_msg_cred *cred)
      */
     unsetenv ("FLUX_PROXY_REMOTE");
 
-    val = getenv ("FLUX_KVS_NAMESPACE");
-    if (attr_add (attrs, "parent-kvs-namespace", val, ATTR_IMMUTABLE) < 0)
-        log_err_exit ("setattr parent-kvs-namespace");
+    if (instance_is_job) {
+        val = getenv ("FLUX_KVS_NAMESPACE");
+        if (attr_add (attrs, "parent-kvs-namespace", val, ATTR_IMMUTABLE) < 0)
+            log_err_exit ("setattr parent-kvs-namespace");
+    }
     unsetenv ("FLUX_KVS_NAMESPACE");
+}
 
+static void init_attrs (attr_t *attrs, pid_t pid, struct flux_msg_cred *cred)
+{
     init_attrs_broker_pid (attrs, pid);
     init_attrs_rc_paths (attrs);
     init_attrs_shell_paths (attrs);
diff --git a/t/t0001-basic.t b/t/t0001-basic.t
index 299d01a3633f..dbfe29b8e40e 100755
--- a/t/t0001-basic.t
+++ b/t/t0001-basic.t
@@ -557,7 +557,17 @@ test_expect_success 'broker broker.pid attribute is readable' '
 	test -n "$BROKERPID" &&
 	test "$BROKERPID" -eq "$BROKERPID"
 '
-
+test_expect_success 'broker sets parent-uri attribute only for jobs' '
+	flux start flux run flux start flux getattr parent-uri &&
+	test_must_fail \
+		flux start flux run flux start -s1 flux getattr parent-uri
+'
+test_expect_success 'broker sets parent-kvs-namespace attribute only for jobs' '
+	flux start flux run flux start flux getattr parent-kvs-namespace &&
+	test_must_fail \
+		flux start flux run \
+			flux start -s1 flux getattr parent-kvs-namespace
+'
 test_expect_success 'local-uri override works' '
 	sockdir=$(mktemp -d) &&
 	newsock=local://$sockdir/meep &&