diff --git a/Dockerfile.agentic-base b/Dockerfile.agentic-base
index 0ac6a688e0..cab089a862 100644
--- a/Dockerfile.agentic-base
+++ b/Dockerfile.agentic-base
@@ -102,7 +102,13 @@ RUN /app/.venv/bin/python -c "import nmp.core.jobs; import nmp.core.entities; pr
 # - nvidia-nat-mcp: mcp_client function type support.
 # - plugins/nemo-agents: exposes `nemo agents ...` commands.
 # - examples/calculator-agent: registers `_type: calculator` function group.
-RUN uv pip install --python /app/.venv/bin/python "nvidia-nat[most]" nvidia-nat-atif nvidia-nat-eval nvidia-nat-mcp && \
+#
+# All nvidia-nat* packages MUST be pinned to the same version. The CLI/meta
+# package historically lagged the plugin packages (e.g. nvidia-nat==1.4.3 vs
+# nvidia-nat-core/eval/langchain==1.7.0), which caused ImportErrors at plugin
+# discovery (e.g. register_dataset_loader) and crashed `nat start fastapi`.
+RUN uv pip install --python /app/.venv/bin/python \
+        "nvidia-nat[most]==1.7.0" nvidia-nat-atif==1.7.0 nvidia-nat-eval==1.7.0 nvidia-nat-mcp==1.7.0 && \
     uv pip install --python /app/.venv/bin/python -e /app/plugins/nemo-agents && \
     uv pip install --python /app/.venv/bin/python -e /app/plugins/nemo-agents/examples/calculator-agent && \
     chown -R harbor:harbor /app/.venv
diff --git a/tests/agentic-use/tests/test_nat_version_consistency.py b/tests/agentic-use/tests/test_nat_version_consistency.py
new file mode 100644
index 0000000000..d7b851dcf7
--- /dev/null
+++ b/tests/agentic-use/tests/test_nat_version_consistency.py
@@ -0,0 +1,58 @@
+# SPDX-FileCopyrightText: Copyright (c) 2025-2026 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
+# SPDX-License-Identifier: Apache-2.0
+
+"""Guard against nvidia-nat package-family version drift.
+
+The agentic-base image installs the NAT family unpinned (see
+Dockerfile.agentic-base / tests/agentic-use/requirements-nat.txt). The CLI/meta
+package historically lagged the plugin packages (e.g. ``nvidia-nat==1.4.3`` vs
+``nvidia-nat-core``/``-eval``/``-langchain==1.7.0``), which silently produced
+``ImportError: cannot import name 'register_dataset_loader'`` at plugin
+discovery and crashed ``nat start fastapi`` with exit code 1 — only surfacing in
+slow, GPU-bound end-to-end runs.
+
+This is the cheapest layer that can catch the mismatch: enumerate the installed
+``nvidia-nat*`` distributions and assert they all report the same version.
+"""
+
+from __future__ import annotations
+
+from importlib import metadata
+
+import pytest
+
+
+def _nat_distributions() -> dict[str, str]:
+    """Return {normalized_name: version} for every installed nvidia-nat* dist."""
+    found: dict[str, str] = {}
+    for dist in metadata.distributions():
+        name = dist.metadata["Name"]
+        if not name:
+            continue
+        normalized = name.lower().replace("_", "-")
+        if normalized == "nvidia-nat" or normalized.startswith("nvidia-nat-"):
+            found[normalized] = dist.version
+    return found
+
+
+def test_nvidia_nat_family_versions_are_aligned() -> None:
+    """All installed nvidia-nat* packages must share the same version.
+
+    Skips when NAT is not installed (NAT lives in an isolated venv and is only
+    present in the agentic-base image / the .venv-nat dev environment).
+    """
+    dists = _nat_distributions()
+    if not dists:
+        pytest.skip("No nvidia-nat* packages installed; NAT runs in an isolated venv.")
+
+    versions = set(dists.values())
+    if len(versions) > 1:
+        detail = "\n".join(f"  {name}=={version}" for name, version in sorted(dists.items()))
+        pytest.fail(
+            "nvidia-nat package family version mismatch — all nvidia-nat* packages "
+            "must be pinned to the same version (a lagging meta/CLI package crashes "
+            "`nat start fastapi` at plugin discovery):\n"
+            f"{detail}\n"
+            "Pin every nvidia-nat* package to one version in Dockerfile.agentic-base "
+            "and tests/agentic-use/requirements-nat.txt."
+        )