fix(gpu_test): skip Vast.ai hosts whose driver predates CUDA 12.4

.claude/skills/verify-warpforth/SKILL.md

@@ -8,7 +8,7 @@ description: Drive the real WarpForth toolchain to prove a change works. Compile
 WarpForth is a CLI compiler: the user writes a `.forth` kernel, runs `warpforthc` to get PTX, and runs that PTX on an NVIDIA GPU with `warpforth-runner`. There is no server or UI. This machine (macOS) has no CUDA GPU, no `nvcc`, no `ptxas`, so:
 
 - **Local surface** (free, always available): `warpforthc`, `warpforth-translate`, `warpforth-opt`. Proves parsing, diagnostics, lowering, and that PTX is emitted.
-- **GPU surface** (costs money, needs `VASTAI_API_KEY`): rents one Vast.ai GPU (cap $0.50/hr, `nvidia/cuda:12.4.0-devel-ubuntu22.04`), builds `warpforth-runner` there with `nvcc`, executes PTX, reads back a buffer. This is the only proof that a kernel computes the right values. **Ask the user before each GPU run**: it spends their money.
+- **GPU surface** (costs money, needs `VASTAI_API_KEY`): rents one Vast.ai GPU (cap $0.50/hr, `nvidia/cuda:12.4.0-devel-ubuntu22.04`, host driver must support CUDA 12.4), builds `warpforth-runner` there with `nvcc`, executes PTX, reads back a buffer. This is the only proof that a kernel computes the right values. **Ask the user before each GPU run**: it spends their money.
 
 Other surfaces, not mapped yet: the GPT-2 demo (`demo/`, `docs/demo.md`) needs a PyTorch Vast.ai image and a manual scp.
 

gpu_test/conftest.py

@@ -29,6 +29,8 @@
 RUNNER_SRC = PROJECT_ROOT / "tools" / "warpforth-runner" / "warpforth-runner.cpp"
 
 MAX_COST_PER_HOUR = 0.50
+CUDA_VERSION = "12.4"
+CUDA_IMAGE = f"nvidia/cuda:{CUDA_VERSION}.0-devel-ubuntu22.04"
 POLL_INTERVAL_S = 10
 POLL_TIMEOUT_S = 300
 INSTANCE_LABEL_PREFIX = "warpforth-test-"
@@ -229,6 +231,7 @@ def _launch(self) -> None:
         query = (
             f"num_gpus=1 rentable=True rented=False compute_cap>={minimum_compute_capability}"
             f" reliability>=0.95 inet_up>=100 dph<={MAX_COST_PER_HOUR}"
+            f" cuda_max_good>={CUDA_VERSION}"
         )
         offers = self.sdk.search_offers(query=query, order="dph", limit=5)
 
@@ -237,13 +240,20 @@ def _launch(self) -> None:
             raise RuntimeError(msg)
 
         offer = offers[0] if isinstance(offers, list) else offers
-        offer_id = int(offer["id"]) if isinstance(offer, dict) else int(offer)
-        logger.info("Launching instance from offer %s", offer_id)
+        details = offer if isinstance(offer, dict) else {"id": offer}
+        offer_id = int(details["id"])
+        logger.info(
+            "Launching instance from offer %s: gpu=%s driver=%s cuda_max_good=%s",
+            offer_id,
+            details.get("gpu_name"),
+            details.get("driver_version"),
+            details.get("cuda_max_good"),
+        )
         self._creation_ambiguous = True
         try:
             result = self.sdk.create_instance(
                 id=offer_id,
-                image="nvidia/cuda:12.4.0-devel-ubuntu22.04",
+                image=CUDA_IMAGE,
                 disk=10.0,
                 runtype="ssh_direc ssh_proxy",
                 label=self.instance_label,

gpu_test/test_vast_session.py

@@ -174,6 +174,19 @@ def test_architecture_constrains_gpu_offer_compute_capability(
     assert "compute_cap>=890" in str(sdk.search_calls[0]["query"])
 
 
+def test_offers_require_a_driver_supporting_the_image_cuda_version(
+    monkeypatch: pytest.MonkeyPatch,
+) -> None:
+    sdk = FakeVastAI()
+    configure_session_test(monkeypatch, sdk)
+
+    with VastSession("key"):
+        pass
+
+    assert "cuda_max_good>=12.4" in str(sdk.search_calls[0]["query"])
+    assert str(sdk.create_calls[0]["image"]).startswith("nvidia/cuda:12.4.")
+
+
 def test_rejected_response_reconciles_without_creating_again(
     monkeypatch: pytest.MonkeyPatch,
 ) -> None: