diff --git a/packages/cli/tests/stack-release.test.mjs b/packages/cli/tests/stack-release.test.mjs
index 8788158c3..a78f52062 100644
--- a/packages/cli/tests/stack-release.test.mjs
+++ b/packages/cli/tests/stack-release.test.mjs
@@ -0,0 +1,2 @@
+import { leasePort } from '../../../scripts/testing/lane-fixtures.mjs';
+import { after as laneAfter } from 'node:test';
@@ -1777 +1779 @@ const TESTER='7499';
-const freePort=async()=>{const s=createServer();s.listen(0,'127.0.0.1');await once(s,'listening');const p=String(s.address().port);await new Promise((r)=>s.close(r));return p};
+const freePort=async()=>String(await leasePort({after:laneAfter},{closed:true}));
diff --git a/packages/webui/tests/service.test.mjs b/packages/webui/tests/service.test.mjs
index a6e66608a..adb460d07 100644
--- a/packages/webui/tests/service.test.mjs
+++ b/packages/webui/tests/service.test.mjs
@@ -0,0 +1,2 @@
+import { leasePort } from '../../../scripts/testing/lane-fixtures.mjs';
+import { after as laneAfter } from 'node:test';
@@ -48,9 +50 @@ function filled(flags, root = REPO) {
-async function closedPort() {
-  const server = createServer();
-  server.listen(0, '127.0.0.1');
-  await once(server, 'listening');
-  const { port } = server.address();
-  server.close();
-  await once(server, 'close');
-  return port;
-}
+async function closedPort() { return leasePort({after:laneAfter}, {closed:true}); }
diff --git a/scripts/test-discord.sh b/scripts/test-discord.sh
index 114994936..4daf0d143 100755
--- a/scripts/test-discord.sh
+++ b/scripts/test-discord.sh
@@ -73,0 +74,2 @@ TOOLS_JSON="{\"roots\":[{\"name\":\"docs\",\"path\":\"$SANDBOX/toolroot\"}],\"ma
+export PI_CODING_AGENT_DIR="$SANDBOX/pi-agent"
+mkdir -p "$PI_CODING_AGENT_DIR"
@@ -145 +147,8 @@ fi
-node_tests() { env -u NODE_TEST_CONTEXT node --test "$@"; }
+node_tests() {
+    local lane_concurrency=()
+    if [ -n "${MOSAIC_TEST_CONCURRENCY:-}" ]; then
+        [ "$MOSAIC_TEST_CONCURRENCY" = 2 ] || return 2
+        lane_concurrency=(--test-concurrency=2)
+    fi
+    env -u NODE_TEST_CONTEXT node --test "${lane_concurrency[@]}" "$@"
+}