diff --git a/.github/workflows/docs-ci.yml b/.github/workflows/docs-ci.yml
index 023b36a..d6e2ca4 100644
--- a/.github/workflows/docs-ci.yml
+++ b/.github/workflows/docs-ci.yml
@@ -37,3 +37,17 @@ jobs:
         run: python -m pip install --disable-pip-version-check pyyaml
       - name: README project table matches repos.yml
         run: python scripts/generate_project_table.py --check README.md
+
+  project-table-unit-tests:
+    name: Project table generator unit tests
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - name: Set up Python
+        uses: actions/setup-python@v5
+        with:
+          python-version: "3.x"
+      - name: Install PyYAML
+        run: python -m pip install --disable-pip-version-check pyyaml
+      - name: Run generator unit tests
+        run: python3 -m unittest discover -s tests
diff --git a/.gitignore b/.gitignore
index fafff2e..ebe4d7f 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,2 +1,7 @@
 .DS_Store
 Thumbs.db
+
+# Python bytecode
+__pycache__/
+*.py[cod]
+*.pyo
diff --git a/scripts/generate_project_table.py b/scripts/generate_project_table.py
index 4cf463a..d8b1298 100755
--- a/scripts/generate_project_table.py
+++ b/scripts/generate_project_table.py
@@ -58,9 +58,36 @@ def load_repositories(manifest_path: Path = MANIFEST) -> list[dict]:
 
 
 def public_repositories(manifest_path: Path = MANIFEST) -> list[dict]:
-    """Return only repositories that should appear in the public table."""
+    """Return only repositories that should appear in the public table.
+
+    Repositories are first filtered by the ``public_product`` flag, then two
+    defence-in-depth guards keep internal tooling out of the public table even
+    when that flag is misconfigured:
+
+    1. Category-based: a repository whose ``category`` is ``internal-tool`` is
+       never surfaced. ``category`` is the org-wide metadata that distinguishes
+       internal tools from public products, so a contradictory
+       ``public_product: true`` on an internal-tool repo is treated as a hard
+       error rather than silently rendered as a public product row.
+    2. Name-based: ``FORBIDDEN_PUBLIC`` hard-codes known-sensitive internal
+       repos that must never appear regardless of any other field.
+    """
     repos = load_repositories(manifest_path)
     surfaced = [r for r in repos if r.get("public_product") is True]
+
+    # Guard 1 (category-based): internal tooling must never be surfaced as a
+    # public product, even if public_product was set to true by mistake. This
+    # is self-maintaining -- new internal tools are excluded by their category
+    # without needing to be added to FORBIDDEN_PUBLIC.
+    for repo in surfaced:
+        if repo.get("category") == "internal-tool":
+            raise ValueError(
+                f"{repo.get('name')!r} has category 'internal-tool' but is "
+                f"flagged public_product: true in {manifest_path.name}; "
+                f"internal tooling must set public_product: false"
+            )
+
+    # Guard 2 (name-based defence-in-depth) for known-sensitive repos.
     names = {r["name"] for r in surfaced}
     for forbidden in FORBIDDEN_PUBLIC:
         if forbidden in names:
diff --git a/tests/test_generate_project_table.py b/tests/test_generate_project_table.py
new file mode 100644
index 0000000..d974648
--- /dev/null
+++ b/tests/test_generate_project_table.py
@@ -0,0 +1,137 @@
+"""Tests for the WasmAgent public project-table generator.
+
+Stdlib-only (``unittest``) so no extra dependencies are required. Run with::
+
+    python3 -m unittest discover -s tests
+    # or
+    python3 tests/test_generate_project_table.py
+"""
+from __future__ import annotations
+
+import sys
+import tempfile
+import unittest
+from pathlib import Path
+
+# Make the generator importable regardless of the current working directory.
+SCRIPTS_DIR = Path(__file__).resolve().parent.parent / "scripts"
+sys.path.insert(0, str(SCRIPTS_DIR))
+
+import generate_project_table as gpt  # noqa: E402
+
+
+def _write_manifest(text: str) -> Path:
+    """Write ``text`` to a temporary manifest file and return its path."""
+    handle = tempfile.NamedTemporaryFile(
+        mode="w", suffix=".yml", delete=False, encoding="utf-8"
+    )
+    handle.write(text)
+    handle.flush()
+    handle.close()
+    return Path(handle.name)
+
+
+PUBLIC = """\
+schema_version: 1
+repositories:
+  - name: wasmagent-js
+    url: https://github.com/WasmAgent/wasmagent-js
+    category: public-product
+    public_product: true
+    purpose: Core JS/TS runtime and MCP server
+"""
+
+
+class PublicRepositoriesTests(unittest.TestCase):
+    def test_surfaces_public_products(self):
+        path = _write_manifest(PUBLIC)
+        surfaced = gpt.public_repositories(path)
+        self.assertEqual([r["name"] for r in surfaced], ["wasmagent-js"])
+
+    def test_excludes_internal_tool_with_public_product_false(self):
+        """An internal-tool repo with public_product: false is omitted."""
+        path = _write_manifest(
+            PUBLIC
+            + """\
+  - name: wasmagent-ops
+    url: https://github.com/WasmAgent/wasmagent-ops
+    category: internal-tool
+    public_product: false
+    purpose: Internal operations and automation tooling
+"""
+        )
+        surfaced = gpt.public_repositories(path)
+        self.assertEqual([r["name"] for r in surfaced], ["wasmagent-js"])
+
+    def test_rejects_internal_tool_misflagged_as_public(self):
+        """A category=internal-tool repo with public_product: true is a hard
+        error (category-based defence-in-depth, wasmagent#53)."""
+        path = _write_manifest(
+            PUBLIC
+            + """\
+  - name: wasmagent-ops
+    url: https://github.com/WasmAgent/wasmagent-ops
+    category: internal-tool
+    public_product: true
+    purpose: Internal operations and automation tooling
+"""
+        )
+        with self.assertRaises(ValueError) as ctx:
+            gpt.public_repositories(path)
+        self.assertIn("internal-tool", str(ctx.exception))
+        self.assertIn("wasmagent-ops", str(ctx.exception))
+
+    def test_rejects_unknown_internal_tool_misflagged_as_public(self):
+        """The category guard is self-maintaining: an internal tool that is
+        NOT in FORBIDDEN_PUBLIC is still rejected by its category."""
+        path = _write_manifest(
+            PUBLIC
+            + """\
+  - name: some-future-ops-bot
+    url: https://github.com/WasmAgent/some-future-ops-bot
+    category: internal-tool
+    public_product: true
+    purpose: Another internal tool
+"""
+        )
+        with self.assertRaises(ValueError):
+            gpt.public_repositories(path)
+
+    def test_rejects_forbidden_public_name_even_without_category(self):
+        """FORBIDDEN_PUBLIC is a name-based backstop independent of category."""
+        path = _write_manifest(
+            PUBLIC
+            + """\
+  - name: claude-bot
+    url: https://github.com/WasmAgent/claude-bot
+    category: public-product
+    public_product: true
+    purpose: Should not be surfaced
+"""
+        )
+        with self.assertRaises(ValueError) as ctx:
+            gpt.public_repositories(path)
+        self.assertIn("claude-bot", str(ctx.exception))
+
+
+class RenderTableTests(unittest.TestCase):
+    def test_render_excludes_internal_tools(self):
+        repos = gpt.public_repositories(
+            _write_manifest(
+                PUBLIC
+                + """\
+  - name: wasmagent-ops
+    url: https://github.com/WasmAgent/wasmagent-ops
+    category: internal-tool
+    public_product: false
+    purpose: Internal operations and automation tooling
+"""
+            )
+        )
+        table = gpt.render_table(repos)
+        self.assertIn("wasmagent-js", table)
+        self.assertNotIn("wasmagent-ops", table)
+
+
+if __name__ == "__main__":
+    unittest.main()