diff --git a/README.md b/README.md
index be8bdeb..3831e75 100644
--- a/README.md
+++ b/README.md
@@ -11,7 +11,7 @@ uvx abench --help
 uvx abench experiments.yaml
 ```
 
-For a specific release use `uvx abench@0.1.1 experiments.yaml`; use
+For a specific release use `uvx abench@0.1.2 experiments.yaml`; use
 `uvx abench@latest` to refresh to the latest release. Docker and model data must
 still be available locally. macOS and Linux hosts are supported.
 
@@ -414,6 +414,12 @@ persistent host cache defaults to `~/.cache/abench/flows`. Change it with
 writes with `--no-reuse-flows` (`reuse_flows: false`). `--cache-from` remains an
 explicit seed option with its existing stricter dependency checks.
 
+Containers set `NUMBA_CACHE_DIR` to `/results/cache/flows/.numba`, a writable
+directory included in those snapshots. This covers installed-library helpers
+(such as `sharrow.maths`) as well as generated flows without writing into
+root-owned site-packages or relying on the container user's home directory.
+Warmup may recompile entries from older snapshots that used Numba's default paths.
+
 Compatibility uses the **installed** Sharrow, Numba, llvmlite, and NumPy versions,
 plus their source repository/commit identities when applicable, Python version,
 and container architecture/CPU features. ActivitySim and model settings are
diff --git a/src/abench/__init__.py b/src/abench/__init__.py
index 430437a..eec3576 100644
--- a/src/abench/__init__.py
+++ b/src/abench/__init__.py
@@ -1,3 +1,3 @@
 """Reproducible ActivitySim experiments in Linux containers."""
 
-__version__ = "0.1.1"
+__version__ = "0.1.2"
diff --git a/src/abench/cli.py b/src/abench/cli.py
index e68ed20..c2abda0 100644
--- a/src/abench/cli.py
+++ b/src/abench/cli.py
@@ -187,6 +187,12 @@ def container_phase(spec, output, data, image, phase_name):
         # so outputs and caches remain writable between attempts and experiments.
         "--user",
         f"{os.getuid()}:{os.getgid()}",
+        # Installed packages and the default home are not writable by this UID.
+        # Configure Numba before Python starts, including all spawned workers.
+        # Keep compiled artifacts in the shared flow snapshot so warmup work is
+        # reusable across measured attempts and compatible experiments.
+        "--env",
+        "NUMBA_CACHE_DIR=/results/cache/flows/.numba",
         "--env",
         f"BENCH_SPEC_PATH=/results/{phase_name}/{snapshot_name}",
         "--env",
diff --git a/src/abench/runtime/worker.py b/src/abench/runtime/worker.py
index 16acb5e..fb1d720 100644
--- a/src/abench/runtime/worker.py
+++ b/src/abench/runtime/worker.py
@@ -5,6 +5,7 @@
 import os
 import subprocess
 import sys
+import tempfile
 import time
 from pathlib import Path
 
@@ -255,6 +256,14 @@ def supervise(spec, phase):
     (phase / "output").mkdir()
     for name in ("flows", "model"):
         Path(f"/results/cache/{name}").mkdir(parents=True, exist_ok=True)
+    # Fail before running models if the configured compilation cache is unusable.
+    numba_cache = Path(os.environ["NUMBA_CACHE_DIR"])
+    try:
+        numba_cache.mkdir(parents=True, exist_ok=True)
+        with tempfile.TemporaryFile(dir=numba_cache):
+            pass
+    except OSError as error:
+        raise RuntimeError(f"Numba cache is not writable: {numba_cache}") from error
     env = dict(os.environ, BENCH_MODEL="1", BENCH_PHASE_DIR=str(phase))
     env["BENCH_STRICT_CACHE"] = "0"
     env["BENCH_TRACK_CACHE"] = (
diff --git a/tests/fixtures/tiny/tiny_extension.py b/tests/fixtures/tiny/tiny_extension.py
index c381b6a..6da19e5 100644
--- a/tests/fixtures/tiny/tiny_extension.py
+++ b/tests/fixtures/tiny/tiny_extension.py
@@ -28,6 +28,12 @@ def bench_initialize(state: workflow.State):
 @workflow.step
 def bench_compute(state: workflow.State, households: pd.DataFrame):
     """Exercise compiled overload reuse, including a measured-only test signature."""
+    # Unlike generated modules, installed Sharrow helpers live in root-owned
+    # site-packages. Importing them must work as the unprivileged model user,
+    # including in spawned workers, and their compiled code must load on reuse.
+    from sharrow.maths import piece
+
+    assert piece(3.0, 1.0, 4.0) == 2.0
     sys.path.insert(0, state.settings.sharrow_cache_dir)
     twice = importlib.import_module("tiny_generated").twice
     households = households.copy()
diff --git a/tests/test_docker.py b/tests/test_docker.py
index 01cf5a5..e8cdcda 100644
--- a/tests/test_docker.py
+++ b/tests/test_docker.py
@@ -64,6 +64,7 @@ def test_tiny_model(tmp_path, multiprocess, sharrow, retry):
     assert cli.main(args) == 0
     run = load_run(output)
     assert run["valid"]
+    assert list((output / "cache/flows/.numba").rglob("maths.piece-*.nbc"))
     attempts = run["spec"]["attempts"]
     assert len(attempts) == (2 if retry else 1)
     assert attempts[-1]["status"] == "accepted"