diff --git a/deploy/lineage-attach/Dockerfile.otel-shim b/deploy/lineage-attach/Dockerfile.otel-shim
index d8a084097..4ff60b452 100644
--- a/deploy/lineage-attach/Dockerfile.otel-shim
+++ b/deploy/lineage-attach/Dockerfile.otel-shim
@@ -67,8 +67,10 @@ COPY --from=ghcr.io/astral-sh/uv:0.9.24@sha256:816fdce3387ed2142e37d2e56e1b1b97c
 # `--system --break-system-packages` lets the install land in a non-venv
 # python too; both flags are inert when --python is a venv.
 ARG OTEL_CONTRIB_VERSION=0.65b0
-RUN pin="$("${VENV_PYTHON}" -c 'from importlib.metadata import version; v = version("opentelemetry-api"); \
-        assert tuple(map(int, v.split(".")[:2])) >= (1, 34); print("opentelemetry-api==" + v)' 2>/dev/null)" \
+# The floor is an expression, not an `assert`: RUN inherits the base image's
+# ENV, and PYTHONOPTIMIZE strips asserts.
+RUN pin="$("${VENV_PYTHON}" -c 'from importlib.metadata import version; import sys; v = version("opentelemetry-api"); \
+        tuple(map(int, v.split(".")[:2])) >= (1, 34) or sys.exit(1); print("opentelemetry-api==" + v)' 2>/dev/null)" \
       || pin="opentelemetry-distro==${OTEL_CONTRIB_VERSION}"; \
     echo "the bake is pinned to ${pin}"; \
     uv pip install --no-cache --python "${VENV_PYTHON}" --system --break-system-packages "${pin}" \
@@ -81,7 +83,7 @@ RUN pin="$("${VENV_PYTHON}" -c 'from importlib.metadata import version; v = vers
       opentelemetry-instrumentation-aiohttp-client \
       opentelemetry-instrumentation-urllib3 \
       opentelemetry-instrumentation-threading \
-      || { echo "REFUSING: the shim could not be installed alongside ${pin} (uv's error is above; if it found no solution, no contrib release is paired with that version)" >&2; exit 1; }
+      || { echo "REFUSING: the shim could not be installed alongside ${pin} (uv's error is above; RECIPE step 2 reads it)" >&2; exit 1; }
 # The install resolves into the app's OWN environment, so it may move a package
 # an app dependency pins (wrapt, deprecated, typing-extensions are the usual
 # suspects) — and the attestations import only OpenTelemetry, never the app.
diff --git a/deploy/lineage-attach/RECIPE.md b/deploy/lineage-attach/RECIPE.md
index aba8b0dce..83273323f 100644
--- a/deploy/lineage-attach/RECIPE.md
+++ b/deploy/lineage-attach/RECIPE.md
@@ -55,8 +55,8 @@ attestation runs before the load and prints nothing when it passes).
 Fail `REFUSING to bake … already instruments …` (exit 3): the app instruments itself — go to step 3 **without** `APP_CONTAINER`/`APP_IMAGE` (capture only).
 Fail `REFUSING to bake … no runnable Python found` (exit 3): outside the shim's envelope (DESIGN "The envelope") — same, capture only; or pass the interpreter as arg 3 if you know it.
 Fail `REFUSING to bake … is not present locally` (exit 3): wrong `IMAGE` — see Inputs; nothing was built.
-Fail `REFUSING: the shim could not be installed alongside …` (the build fails): no contrib release is paired with the app's `opentelemetry-api` (a core newer than its contrib release, or a package index that lags) — uv's own error is above the line.
-Fail `ATTESTATION FAILED` (exit 4): the bake itself is broken (the image was not loaded) — read the assertion it prints; not an app property.
+Fail `REFUSING: the shim could not be installed alongside …` (the build fails): uv's own error is above the line and names the blocker; the two usual cases follow. Alongside `opentelemetry-api==…`: no contrib release is paired with the app's core yet (a core newer than its contrib release, or a package index that lags) — go to step 3 **without** `APP_CONTAINER`/`APP_IMAGE` (capture only) until the paired release reaches the index, then re-bake. Alongside `opentelemetry-distro==…` (the default, when the app carries no `opentelemetry-api` or one older than 1.34.0): the app's environment cannot take that release at all (uv says why, e.g. `depends on Python>=3.10`) — outside the envelope, capture only.
+Fail `ATTESTATION FAILED` (exit 4): the bake itself is broken (the image was not loaded) — read the line it prints; not an app property.
 
 ## 3. Attach (once per Deployment)
 
diff --git a/deploy/lineage-attach/build-otel-shim.sh b/deploy/lineage-attach/build-otel-shim.sh
index d5e0b46ad..e19b97e00 100755
--- a/deploy/lineage-attach/build-otel-shim.sh
+++ b/deploy/lineage-attach/build-otel-shim.sh
@@ -249,7 +249,9 @@ build_image() {
 
 # Attestation: the bake proves itself before anything is loaded. Gate off, not
 # one opentelemetry module may load; gate on, the hook ran, the exporter
-# selection is explicit, and the propagator injects a traceparent.
+# selection is explicit, and the propagator injects a traceparent. No `assert`
+# here: the interpreter runs under the image's own ENV, and PYTHONOPTIMIZE
+# strips asserts.
 verify_inert() {
   if ! "$CONTAINER_TOOL" run --rm --network=none --entrypoint "$VENV_PYTHON" "$WRAPPER_TAG" -c '
 import sys
@@ -263,14 +265,14 @@ raise SystemExit("gate off, yet otel loaded: %s" % loaded if loaded else 0)'; th
 verify_propagates() {
   if ! "$CONTAINER_TOOL" run --rm --network=none -e LINEAGE_PROPAGATE=1 --entrypoint "$VENV_PYTHON" "$WRAPPER_TAG" -c '
 import os, sys
-assert "opentelemetry.instrumentation.auto_instrumentation" in sys.modules, "hook did not run"
-assert os.environ.get("OTEL_TRACES_EXPORTER") is not None, "exporter selection not pinned"
+"opentelemetry.instrumentation.auto_instrumentation" in sys.modules or sys.exit("hook did not run")
+os.environ.get("OTEL_TRACES_EXPORTER") is not None or sys.exit("exporter selection not pinned")
 from opentelemetry import trace
 from opentelemetry.propagate import inject
 with trace.get_tracer("attest").start_as_current_span("attest"):
     carrier = {}
     inject(carrier)
-assert "traceparent" in carrier, "propagator injects nothing: %r" % carrier'; then
+"traceparent" in carrier or sys.exit("propagator injects nothing: %r" % carrier)'; then
     echo "ATTESTATION FAILED for ${WRAPPER_TAG}: gate on, but the hook did not come up." >&2
     exit 4
   fi