diff --git a/.gitea/workflows/ci.yml b/.gitea/workflows/ci.yml
new file mode 100644
index 0000000..a5e2115
--- /dev/null
+++ b/.gitea/workflows/ci.yml
@@ -0,0 +1,68 @@
+name: ci
+
+# Runs on the ubuntu24.04-x64-lean4.35 runner: jobs execute on the host, Lean 4.35
+# comes from /root/.elan, and there is no Node, so the commit is cloned with git
+# instead of actions/checkout.
+
+on:
+  push:
+    branches: [main, "ci/**"]
+  pull_request:
+  workflow_dispatch:
+
+jobs:
+  test:
+    runs-on: ubuntu24.04-x64-lean4.35
+    timeout-minutes: 20
+    steps:
+      - name: Check out
+        run: |
+          set -eu
+          git init -q . && git remote add origin "${{ github.server_url }}/${{ github.repository }}.git"
+          git -c http.extraHeader="Authorization: token ${{ github.token }}" fetch -q --depth 1 origin "${{ github.sha }}"
+          git checkout -q FETCH_HEAD && git log --oneline -1
+
+      - name: Lean
+        run: |
+          lean --version
+          echo "project toolchain: $(cat lean-toolchain)"
+
+      - name: Install
+        run: |
+          set -eu
+          python3 -m venv .venv 2>/dev/null || { apt-get update -qq && apt-get install -y -qq python3-venv && python3 -m venv .venv; }
+          .venv/bin/python -m pip install --quiet --disable-pip-version-check -e .
+          .venv/bin/lean-agent --help > /dev/null
+
+      - name: Unit tests (real Lean verifier)
+        run: .venv/bin/python -m unittest discover -s tests -v
+
+      - name: CLI end to end (scripted provider, real Lean)
+        run: |
+          set -eu
+          printf '%s\n' '{"id":"refl","statement":"∀ n : Nat, n + 0 = n"}' > task.json
+          cat > provider.py <<'PY'
+          import sys
+          sys.stdin.read()
+          print("intro n\nrfl")
+          PY
+          .venv/bin/lean-agent task.json --provider-command '["python3","provider.py"]' --attempts 2 | tee out.json
+          grep -q '"success": true' out.json
+
+      - name: With Mathlib (uses lean-bench's host cache, if present)
+        run: |
+          set -eu
+          dir="$(ls -d /opt/lean-cache/leanbench-*/ 2>/dev/null | while read d; do [ -f "$d/.ready" ] && echo "$d"; done | tail -1)"
+          if [ -z "$dir" ]; then
+            echo "No ready Mathlib project on this host yet (lean-bench CI builds it); skipping."
+            exit 0
+          fi
+          printf '%s\n' '{"id":"m","statement":"(2 : ℕ) + 2 = 4","prelude":"import Mathlib"}' > mtask.json
+          cat > mprovider.py <<'PY'
+          import sys
+          sys.stdin.read()
+          print("norm_num")
+          PY
+          .venv/bin/lean-agent mtask.json --provider-command '["python3","mprovider.py"]' \
+            --lean-project "$dir" --lean-command '["lake","env","lean"]' --lean-timeout 300 | tee mout.json
+          grep -q '"success": true' mout.json
diff --git a/lean-toolchain b/lean-toolchain
index a8afa7d..a6aff06 100644
--- a/lean-toolchain
+++ b/lean-toolchain
@@ -1 +1 @@
-leanprover/lean4:v4.33.1
+leanprover/lean4:v4.35.0