diff --git a/.github/scripts/start-dev-node.sh b/.github/scripts/start-dev-node.sh
new file mode 100755
index 0000000..d31e265
--- /dev/null
+++ b/.github/scripts/start-dev-node.sh
@@ -0,0 +1,24 @@
+#!/usr/bin/env bash
+# Starts a bizinikiwi dev node for the .slow. specs, with its RPC on the port
+# the specs connect to (test-support BIZINIKIWI_PORT, 30333), and waits until
+# it answers. Fails if it never does, so a spec run cannot start without it.
+set -euo pipefail
+
+# pinned by digest: a tag can move under a run
+IMAGE=pezkuwi/bizinikiwi@sha256:130e8ddd1ec36b00422fcfe565fb596d6a81889e3aeb5f45d13bd92993d09a19
+PORT=${TEST_BIZINIKIWI_PORT:-30333}
+
+docker run -d --name dev-node -p "$PORT:9944" "$IMAGE" --dev --rpc-external --rpc-cors all
+
+for _ in $(seq 1 60); do
+  if curl -sf -H 'Content-Type: application/json' \
+      -d '{"id":1,"jsonrpc":"2.0","method":"system_chain"}' "http://127.0.0.1:$PORT" > /dev/null; then
+    echo "dev node answers on $PORT"
+    exit 0
+  fi
+  sleep 2
+done
+
+echo "dev node did not answer on $PORT within 120s"
+docker logs dev-node 2>&1 | tail -40
+exit 1
diff --git a/.github/workflows/pr-any.yml b/.github/workflows/pr-any.yml
index 6c449c2..b751dbe 100644
--- a/.github/workflows/pr-any.yml
+++ b/.github/workflows/pr-any.yml
@@ -24,3 +24,22 @@ jobs:
     # tree it changed. The committed tree must already be what they produce.
     - name: tree unchanged
       run: git diff --exit-code --stat
+
+  # The .slow. specs drive the UI against a live dev node; `yarn test` leaves
+  # them out, so they run here with one.
+  slow:
+    name: pr (test:slow)
+    runs-on: ubuntu-latest
+    timeout-minutes: 20
+    steps:
+    - uses: actions/checkout@v4
+    - uses: actions/setup-node@v4
+      with:
+        node-version: 'lts/*'
+    - name: dev node
+      run: .github/scripts/start-dev-node.sh
+    - name: test:slow
+      run: |
+        corepack enable
+        yarn install --immutable
+        yarn test:slow
diff --git a/.github/workflows/test-nightly.yml b/.github/workflows/test-nightly.yml
index c3add97..d7d2ea3 100644
--- a/.github/workflows/test-nightly.yml
+++ b/.github/workflows/test-nightly.yml
@@ -20,6 +20,9 @@ jobs:
     - uses: actions/setup-node@v4
       with:
         node-version: 'lts/*'
+    # test:all includes the .slow. specs, which need a live dev node
+    - name: dev node
+      run: .github/scripts/start-dev-node.sh
     - name: ${{ matrix.step }}
       run: |
         yarn install --immutable