diff --git a/.github/actions/ecr-build-push-pull/README.md b/.github/actions/ecr-build-push-pull/README.md
index 2e306c978b8e..2dea04797126 100644
--- a/.github/actions/ecr-build-push-pull/README.md
+++ b/.github/actions/ecr-build-push-pull/README.md
@@ -16,6 +16,19 @@ ECR is also used as the BuildKit layer cache.
     ecr-url: (optional, complete url for ECR storage)
 ```
 
+## Verifying a freshly built image
+
+Pass `verify-test-path` to assert against the image before it is published:
+
+```yaml
+    verify-test-path: docker/test/test_image_invariants.py
+```
+
+The tests run only on a full build, with `IMAGE_TAG` set, so the caller's job needs `uv`
+(`astral-sh/setup-uv`). A failure fails the action with nothing pushed, so the next run
+rebuilds rather than serving the bad image from the deps cache. Exact-tag and deps-cache hits skip
+them: that image passed when it was built.
+
 ## ECR URL resolution order
 
 1. `ecr-url` input
diff --git a/.github/actions/ecr-build-push-pull/action.yml b/.github/actions/ecr-build-push-pull/action.yml
index b289b4ebb7d8..7c595e7d3407 100644
--- a/.github/actions/ecr-build-push-pull/action.yml
+++ b/.github/actions/ecr-build-push-pull/action.yml
@@ -37,6 +37,16 @@ inputs:
     description: Tag used for the ECR layer cache image (e.g. "cache-base", "cache-curobo").
     required: false
     default: 'cache'
+  verify-test-path:
+    description: >
+      Path to a test file or directory asserted against a freshly built image, before it is
+      tagged or pushed. Tests run with IMAGE_TAG set; a failure fails the action with nothing
+      published, so the next run rebuilds instead of inheriting the bad image from the cache.
+
+      Not run on an exact-tag or deps-cache hit: those serve an image that already passed when it
+      was built.
+    required: false
+    default: ''
   pull-on-deps-hit:
     description: >
       Pull the image locally after a deps-cache hit. Needed by jobs that run
@@ -242,6 +252,23 @@ runs:
         cache-to: ${{ steps.resolve-ecr.outputs.available == 'true' && format('type=registry,ref={0},mode=max', env.CACHE_IMAGE) || '' }}
         deps-hash: ${{ steps.deps-hash.outputs.hash }}
 
+    # Assert against the image while it is only local: the push steps below publish under both
+    # the commit tag and the deps tag, and a deps-cache hit later serves that image without
+    # rebuilding it, so anything published unverified stays unverified.
+    - name: Verify freshly built image
+      if: >
+        inputs.verify-test-path != '' &&
+        steps.pull-exact.outputs.hit != 'true' &&
+        steps.deps-cache.outputs.deps-cache-hit != 'true'
+      shell: bash
+      env:
+        IMAGE_TAG: ${{ inputs.image-tag }}
+        TEST_PATH: ${{ inputs.verify-test-path }}
+      run: |
+        set -euo pipefail
+        uv run --no-project --with pytest \
+          python -m pytest -q "${TEST_PATH}"
+
     - name: Tag built image with ECR-prefixed name
       if: >
         steps.resolve-ecr.outputs.available == 'true' &&
diff --git a/.github/actions/run-tests/run_tests.sh b/.github/actions/run-tests/run_tests.sh
index 3779ab10c562..fbccbfa45dd3 100755
--- a/.github/actions/run-tests/run_tests.sh
+++ b/.github/actions/run-tests/run_tests.sh
@@ -320,8 +320,11 @@ run_tests() {
       set -e
       cd /workspace/isaaclab
       mkdir -p tests
-      rm _isaac_sim || true
-      ln -s /isaac-sim _isaac_sim
+      # The runtime mounts above create /isaac-sim in every image. Link it only where Kit
+      # lives there: in the kit-less image the link would read as a downloaded Isaac Sim,
+      # which isaaclab.sh refuses to combine with the image's VIRTUAL_ENV.
+      rm -f _isaac_sim
+      if [ -x /isaac-sim/python.sh ]; then ln -s /isaac-sim _isaac_sim; fi
       if [ -n \"\${WARP_CACHE_PATH:-}\" ]; then
         ./isaaclab.sh -p tools/verify_warp_cache.py
       fi
diff --git a/.github/workflows/build.yaml b/.github/workflows/build.yaml
index 2ff42e847a07..ce2791c8cf84 100644
--- a/.github/workflows/build.yaml
+++ b/.github/workflows/build.yaml
@@ -182,6 +182,15 @@ jobs:
         fetch-depth: 1
         lfs: true
 
+    # The GPU runners have no uv on PATH; the invariant check below needs it.
+    - name: Set up uv
+      uses: astral-sh/setup-uv@v6
+      with:
+        enable-cache: true
+
+    # #6329 aborts the pip install when it strands a prebundled package's __init__.py
+    # (nvbugs 6343978: 14 Isaac Sim extensions fail to load). The images install with
+    # ``uv sync``, which never runs that guard, so assert the same invariant on the image.
     - name: Build and push to ECR
       uses: ./.github/actions/ecr-build-push-pull
       with:
@@ -190,6 +199,7 @@ jobs:
         isaacsim-version: ${{ needs.config.outputs.isaacsim_image_tag }}
         dockerfile-path: docker/Dockerfile.base
         cache-tag: cache-base
+        verify-test-path: docker/test/test_image_invariants.py
 
   build-curobo:
     name: Build cuRobo Docker Image
diff --git a/docker/test/test_container_profiles.py b/docker/test/test_container_profiles.py
index 39d39c974829..9a17fc87aab7 100644
--- a/docker/test/test_container_profiles.py
+++ b/docker/test/test_container_profiles.py
@@ -15,6 +15,7 @@
 from docker.utils import ContainerInterface, volume_mounts
 
 DOCKER_DIR = Path(__file__).resolve().parents[1]
+REPO_ROOT = DOCKER_DIR.parent
 
 
 @pytest.fixture
@@ -288,6 +289,41 @@ def test_kitless_compose_service_has_no_isaac_sim_mounts():
     assert all("/kit/" not in mount["target"].lower() for mount in mounts)
 
 
+def test_image_is_verified_before_it_is_published():
+    """A published image must be a verified one.
+
+    The push steps publish under both the commit tag and the deps tag, and a later deps-cache hit
+    serves that image without rebuilding it, so anything published unverified stays unverified.
+    """
+    action = yaml.safe_load(
+        (REPO_ROOT / ".github" / "actions" / "ecr-build-push-pull" / "action.yml").read_text(encoding="utf-8")
+    )
+    names = [step["name"] for step in action["runs"]["steps"] if "name" in step]
+
+    assert names.index("Verify freshly built image") < names.index("Push to ECR") < names.index("Push deps tag")
+
+    build = yaml.safe_load((REPO_ROOT / ".github" / "workflows" / "build.yaml").read_text(encoding="utf-8"))
+    (base_build,) = [
+        step for step in build["jobs"]["build"]["steps"] if step.get("uses") == "./.github/actions/ecr-build-push-pull"
+    ]
+
+    assert base_build["with"]["verify-test-path"] == "docker/test/test_image_invariants.py"
+
+
+def test_run_tests_links_isaac_sim_only_where_kit_is_installed():
+    """The kit-less image has no Kit under ``/isaac-sim``, which the runtime mounts create anyway.
+
+    Linking it as ``_isaac_sim`` there reads as a downloaded Isaac Sim, which ``isaaclab.sh``
+    refuses to combine with the image's ``VIRTUAL_ENV``.
+    """
+    script = (REPO_ROOT / ".github" / "actions" / "run-tests" / "run_tests.sh").read_text(encoding="utf-8")
+
+    link_lines = [line.strip() for line in script.splitlines() if "ln -s /isaac-sim _isaac_sim" in line]
+
+    assert link_lines
+    assert all("/isaac-sim/python.sh" in line for line in link_lines), link_lines
+
+
 def test_kitless_volume_key_resolves_owned_image_paths(monkeypatch: pytest.MonkeyPatch):
     """The explicit kit-less volume key resolves the paths prepared by its Dockerfile."""
     monkeypatch.setenv("DOCKER_ISAACLAB_PATH", "/workspace/isaaclab")
diff --git a/docker/test/test_image_invariants.py b/docker/test/test_image_invariants.py
new file mode 100644
index 000000000000..74aea9920244
--- /dev/null
+++ b/docker/test/test_image_invariants.py
@@ -0,0 +1,54 @@
+# Copyright (c) 2022-2026, The Isaac Lab Project Developers (https://github.com/isaac-sim/IsaacLab/blob/main/CONTRIBUTORS.md).
+# All rights reserved.
+#
+# SPDX-License-Identifier: BSD-3-Clause
+
+"""Invariants asserted against a *built* container image.
+
+The image under test is named by ``IMAGE_TAG``; the tests skip when it is unset so a plain
+``pytest docker/test`` stays green on a machine with no image. Run one explicitly with::
+
+    IMAGE_TAG=isaac-lab-base:latest pytest docker/test/test_image_invariants.py
+"""
+
+from __future__ import annotations
+
+import os
+import subprocess
+
+import pytest
+
+IMAGE_TAG = os.environ.get("IMAGE_TAG", "")
+
+
+def _in_image(script: str) -> str:
+    """Run ``script`` with bash inside the image under test and return its stdout."""
+    result = subprocess.run(
+        ["docker", "run", "--rm", "--entrypoint", "bash", IMAGE_TAG, "-lc", script],
+        capture_output=True,
+        text=True,
+        check=True,
+    )
+    return result.stdout
+
+
+@pytest.fixture(autouse=True)
+def _require_image():
+    if not IMAGE_TAG:
+        pytest.skip("IMAGE_TAG is unset; no built image to assert against")
+
+
+def test_no_prebundled_package_lost_its_entry_point():
+    """A dangling ``__init__.py`` in a prebundle stops Isaac Sim extensions loading.
+
+    Isaac Sim shares prebundled packages between extensions as per-file symlinks, so deleting
+    or replacing one strands every symlink into it. #6329 added this invariant to the pip
+    install path after nvbugs 6343978, where it cost 438 error lines and 14 failed extensions.
+    The images now install with ``uv sync``, which never calls that code, so assert it here.
+
+    Only ``__init__.py`` is fatal: the shipped image already carries dangling submodules and
+    ``.pyi`` stubs that no extension imports - 41 of them, against develop's 48 - mostly
+    generated protobuf stubs inside an Omniverse extension's own prebundle.
+    """
+    broken = _in_image('find / -path "*pip_prebundle*" -xtype l -name "__init__.py" 2>/dev/null || true').strip()
+    assert not broken, "prebundled packages lost their entry point:\n" + broken