diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index 2716a04..79a1fb6 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -16,6 +16,10 @@ jobs:
   # /usr/bin/python3 and resolves back to it. Containers use their own image.
   linux-containment:
     runs-on: ubuntu-24.04
+    # A normal run takes about 4 minutes. A container engine that wedges
+    # (seen with gVisor on hosted runners) must fail the job, not hold it
+    # for GitHub's 6-hour default.
+    timeout-minutes: 30
     steps:
       - uses: actions/checkout@v4
       - name: Install containment dependencies
@@ -42,8 +46,19 @@ jobs:
         # only). Parsers never get a network, and Docker's --network none
         # alone is refused by runsc on these runners ("cannot run with
         # network enabled in root network namespace").
+        #
+        # gVisor's default platform, systrap, hangs on some hosts: the
+        # sandbox starts, but the container's first process never runs, and
+        # `docker rm -f` cannot remove it. Which hosted runner a job lands on
+        # decides it, so probe it and fall back to ptrace (slower, same
+        # isolation boundary) where it hangs.
         run: |
-          sudo runsc install -- --network=none
+          PLATFORM=systrap
+          if ! sudo timeout -s KILL 60 runsc --network=none --platform=systrap do /bin/true; then
+            echo "::warning::gVisor's systrap platform hangs on this runner; registering runsc with --platform=ptrace"
+            PLATFORM=ptrace
+          fi
+          sudo runsc install -- --network=none --platform="$PLATFORM"
           sudo systemctl restart docker
           docker info --format '{{json .Runtimes}}' | grep -q runsc
       - name: Fetch the pinned parser image (trusted acquisition step)
@@ -57,7 +72,11 @@ jobs:
         # step even though its output is piped through tee.
         shell: bash
         run: |
-          .venv/bin/python -m pytest tests -q -rs | tee pytest.log
+          # --timeout (pytest-timeout): a test stuck longer than this fails
+          # with its name and every thread's stack, and the run goes on, so a
+          # hang in the container engine names the test that hit it.
+          # --durations lists the slowest tests either way.
+          .venv/bin/python -m pytest tests -q -rs --timeout=120 --durations=15 | tee pytest.log
           # Windows-only tests may skip here, and the GPU variant of the OCI
           # backend skips because hosted runners have no GPU; nothing else may.
           if grep "SKIPPED" pytest.log | grep -v "Windows feature" | grep -qv "no usable GPU"; then
diff --git a/docs/containment.md b/docs/containment.md
index da25ac4..50db911 100644
--- a/docs/containment.md
+++ b/docs/containment.md
@@ -102,6 +102,12 @@ as the entrypoint of the image, so it must resolve inside the image (e.g.
   with that reason — it is never replaced by another runtime. Register gVisor
   with `runsc install -- --network=none` so it builds no network stack at all;
   CI does this, and some Docker hosts refuse runsc with `--network none` alone.
+  On some hosts gVisor's default platform, `systrap`, hangs: the sandbox
+  starts but the container's first process never runs, and `docker rm -f`
+  cannot remove it (Stele then reports `ContainmentCleanupError`). Check with
+  `runsc --network=none --platform=systrap do /bin/true`. Where it hangs,
+  register `runsc install -- --network=none --platform=ptrace`: slower, the
+  same isolation boundary. CI probes this on every run.
 - **GPU.** `OciBackend(gpu=True)` passes NVIDIA GPUs through with CDI
   (`--device nvidia.com/gpu=all`) or Docker's `--gpus all`, and is unavailable
   ("no usable GPU") when the engine exposes none. gVisor supports GPUs only via
diff --git a/pyproject.toml b/pyproject.toml
index 29f5857..12137b2 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -13,7 +13,7 @@ dependencies = []
 # Wasm/WASI sandbox backend (stele.containment.wasm). The API used (fuel,
 # epoch interruption, read-only preopens via fs_mutable) needs wasmtime 49+.
 wasm = ["wasmtime>=49"]
-dev = ["pytest>=8", "wasmtime>=49"]
+dev = ["pytest>=8", "pytest-timeout>=2.3", "wasmtime>=49"]
 
 [tool.hatch.build.targets.wheel]
 packages = ["stele"]
diff --git a/uv.lock b/uv.lock
index 0e3c400..0a50c4d 100644
--- a/uv.lock
+++ b/uv.lock
@@ -63,6 +63,18 @@ wheels = [
     { url = "https://files.pythonhosted.org/packages/24/25/1de2678b631f5a49215c6c96fff41ba892b0a34df68d6d80292b1b48aa7f/pytest-9.1.1-py3-none-any.whl", hash = "sha256:37a86b45efb9a47a61a36449063e8e18d0cab3161329fc099eb21783169c4f0c", size = 386536, upload-time = "2026-06-19T10:58:31.347Z" },
 ]
 
+[[package]]
+name = "pytest-timeout"
+version = "2.4.0"
+source = { registry = "https://pypi.org/simple" }
+dependencies = [
+    { name = "pytest" },
+]
+sdist = { url = "https://files.pythonhosted.org/packages/ac/82/4c9ecabab13363e72d880f2fb504c5f750433b2b6f16e99f4ec21ada284c/pytest_timeout-2.4.0.tar.gz", hash = "sha256:7e68e90b01f9eff71332b25001f85c75495fc4e3a836701876183c4bcfd0540a", size = 17973, upload-time = "2025-05-05T19:44:34.99Z" }
+wheels = [
+    { url = "https://files.pythonhosted.org/packages/fa/b6/3127540ecdf1464a00e5a01ee60a1b09175f6913f0644ac748494d9c4b21/pytest_timeout-2.4.0-py3-none-any.whl", hash = "sha256:c42667e5cdadb151aeb5b26d114aff6bdf5a907f176a007a30b940d3d865b5c2", size = 14382, upload-time = "2025-05-05T19:44:33.502Z" },
+]
+
 [[package]]
 name = "stele"
 version = "0.1.0"
@@ -71,6 +83,7 @@ source = { editable = "." }
 [package.optional-dependencies]
 dev = [
     { name = "pytest" },
+    { name = "pytest-timeout" },
     { name = "wasmtime" },
 ]
 wasm = [
@@ -80,6 +93,7 @@ wasm = [
 [package.metadata]
 requires-dist = [
     { name = "pytest", marker = "extra == 'dev'", specifier = ">=8" },
+    { name = "pytest-timeout", marker = "extra == 'dev'", specifier = ">=2.3" },
     { name = "wasmtime", marker = "extra == 'dev'", specifier = ">=49" },
     { name = "wasmtime", marker = "extra == 'wasm'", specifier = ">=49" },
 ]