diff --git a/heart/checks/url_check.sh b/heart/checks/url_check.sh
index a2bf48b..fd14d41 100755
--- a/heart/checks/url_check.sh
+++ b/heart/checks/url_check.sh
@@ -22,7 +22,14 @@ ENTRIES=(
   # --- original three (Binder / wrong-owner / dead-branch) ---
   'mybinder\.org|||mybinder.org URL (Binder is no longer supported — use Colab)'
   'colab\.research\.google\.com/github/Jammy2211/|||Colab URL with Jammy2211 owner (use PyAutoLabs)'
-  'colab\.research\.google\.com/github/[^/]+/[^/]+/blob/release/|||Colab URL pinned to /blob/release/ (use a tagged version or /blob/main/)'
+  'colab\.research\.google\.com/github/[^/]+/[^/]+/blob/release/|||Colab URL pinned to /blob/release/ (use a date-tagged version)'
+
+  # --- Colab URL forms the release bumper cannot maintain ---
+  # bump_colab_urls.sh only rewrites date-tagged PyAutoLabs URLs, so an
+  # unpinned /blob/main/ Colab link silently drifts from the released code.
+  'colab\.research\.google\.com/github/PyAutoLabs/(autofit_workspace|autogalaxy_workspace|autolens_workspace|HowToFit|HowToGalaxy|HowToLens)/blob/main/|||Colab URL pinned to /blob/main/ (use a date-tagged version — the release bumper skips main)'
+  # Chapter tutorials live in the HowTo repos; workspace-repo chapter paths are dead.
+  'colab\.research\.google\.com/github/PyAutoLabs/(autofit|autogalaxy|autolens)_workspace/blob/[^/]+/notebooks/chapter_|||Colab URL to notebooks/chapter_* in a workspace repo (chapters live in HowToFit/HowToGalaxy/HowToLens)'
 
   # --- typo ---
   'hhttps://|||hhttps:// typo (should be https://)'
diff --git a/tests/test_url_check.py b/tests/test_url_check.py
index 944c5cc..4d8eae3 100644
--- a/tests/test_url_check.py
+++ b/tests/test_url_check.py
@@ -79,3 +79,47 @@ def test_ipynb_files_scanned(tmp_path):
     result = run(tmp_path)
     assert result.returncode == 1
     assert "demo.ipynb" in result.stdout
+
+
+def test_blob_main_colab_url_fails(tmp_path):
+    (tmp_path / "README.md").write_text(
+        "https://colab.research.google.com/github/PyAutoLabs/HowToLens/blob/main/notebooks/chapter_1_introduction/tutorial_1_grids_and_galaxies.ipynb"
+    )
+    result = run(tmp_path)
+    assert result.returncode == 1
+    assert "release bumper skips main" in result.stdout
+
+
+def test_blob_main_non_notebook_repo_passes(tmp_path):
+    # /blob/main/ is only forbidden for the six notebook repos — other repos'
+    # Colab links (none exist today) are not the bumper's problem.
+    (tmp_path / "README.md").write_text(
+        "https://colab.research.google.com/github/PyAutoLabs/PyAutoFit/blob/main/example.ipynb"
+    )
+    result = run(tmp_path)
+    assert result.returncode == 0, result.stdout + result.stderr
+
+
+def test_workspace_chapter_colab_url_fails(tmp_path):
+    (tmp_path / "README.md").write_text(
+        "https://colab.research.google.com/github/PyAutoLabs/autogalaxy_workspace/blob/2026.7.6.649/notebooks/chapter_1_introduction/tutorial_0_visualization.ipynb"
+    )
+    result = run(tmp_path)
+    assert result.returncode == 1
+    assert "chapters live in HowToFit/HowToGalaxy/HowToLens" in result.stdout
+
+
+def test_howto_chapter_colab_url_passes(tmp_path):
+    (tmp_path / "README.md").write_text(
+        "https://colab.research.google.com/github/PyAutoLabs/HowToGalaxy/blob/2026.7.6.649/notebooks/chapter_1_introduction/tutorial_0_visualization.ipynb"
+    )
+    result = run(tmp_path)
+    assert result.returncode == 0, result.stdout + result.stderr
+
+
+def test_workspace_non_chapter_notebook_passes(tmp_path):
+    (tmp_path / "README.md").write_text(
+        "https://colab.research.google.com/github/PyAutoLabs/autolens_workspace/blob/2026.7.6.649/notebooks/imaging/start_here.ipynb"
+    )
+    result = run(tmp_path)
+    assert result.returncode == 0, result.stdout + result.stderr