diff --git a/CHANGES.md b/CHANGES.md
index 7bb2ab5..827962e 100644
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -2,7 +2,15 @@
  
 ## 5.3.2 (unreleased)
 
-<!-- Add future changes here -->
+- Fix: Restore backward compatibility for hook config sections named
+  `[namespace-subsection]`. After 5.3.1 anchored section matching strictly on
+  `:`, downstream hooks (notably `mxmake`) that emit `[mxmake-env]`-style
+  sections broke. The matcher now accepts the historical `-` delimiter too,
+  logging a one-time deprecation warning per offending section. Hook classes
+  that declared a trailing delimiter in their namespace (e.g. `namespace = "mxmake-"`)
+  are normalized: the trailing `-` is stripped and the hook author is warned.
+  Migration: rename `[ns-section]` to `[ns:section]` and set `namespace = "ns"`.
+  [jensens]
 
 
 ## 5.3.1 (2026-05-29)
diff --git a/EXTENDING.md b/EXTENDING.md
index d251da6..ef53238 100644
--- a/EXTENDING.md
+++ b/EXTENDING.md
@@ -17,6 +17,11 @@ The `:` separator is used on purpose: it cannot occur in a package name, so a ho
 can never accidentally claim a package section whose name merely starts with the same letters
 (e.g. a `uv` hook must not swallow a package named `uvst.addon`).
 
+The historical `[namespace-subsection]` form is still accepted for backward compatibility
+but logs a deprecation warning and should be migrated to `[namespace:subsection]`. Hooks
+that declared their namespace with a trailing delimiter (e.g. `namespace = "mxmake-"`) keep
+working — the trailing `-` is stripped — and the hook author is warned to drop it.
+
 This looks like so:
 
 ```INI
diff --git a/src/mxdev/config.py b/src/mxdev/config.py
index 61ec767..33169f7 100644
--- a/src/mxdev/config.py
+++ b/src/mxdev/config.py
@@ -108,15 +108,42 @@ def __init__(
             if line:
                 self.ignore_keys.append(line)
 
+        # Canonical delimiter is ":" (cannot appear in a Python distribution
+        # name, so it never collides with a package section). "-" is the
+        # historical delimiter and is still accepted, but emits a deprecation
+        # warning. Legacy hooks declared their namespace with the trailing
+        # delimiter baked in (e.g. namespace = "mxmake-"); we normalize that
+        # too and warn the hook author.
+        _warned: set[str] = set()
+
+        def _warn_once(key: str, message: str) -> None:
+            if key in _warned:
+                return
+            _warned.add(key)
+            logger.warning(message)
+
         def is_ns_member(name) -> bool:
-            # A section belongs to a hook only when its name is exactly the
-            # hook namespace or is prefixed with "<namespace>:". The colon
-            # cannot occur in a package name, so it unambiguously separates
-            # hook sections from package sections and avoids swallowing
-            # packages that merely start with the namespace (e.g. a "uv" hook
-            # must not claim a package named "uvst.addon").
             for hook in hooks:
-                if name == hook.namespace or name.startswith(f"{hook.namespace}:"):
+                ns = hook.namespace
+                effective_ns = ns.rstrip("-")
+                if effective_ns != ns:
+                    _warn_once(
+                        f"ns:{ns}",
+                        f"Hook '{type(hook).__name__}' declares namespace='{ns}' with a "
+                        f"trailing '-'; this form is deprecated. Use namespace='{effective_ns}' "
+                        f"and the ':' section delimiter (e.g. [{effective_ns}:section]).",
+                    )
+                if name == effective_ns:
+                    return True
+                if name.startswith(f"{effective_ns}:"):
+                    return True
+                if name.startswith(f"{effective_ns}-"):
+                    subsection = name[len(effective_ns) + 1 :]
+                    _warn_once(
+                        f"section:{name}",
+                        f"Hook section '[{name}]' uses the deprecated '-' delimiter; "
+                        f"rename to '[{effective_ns}:{subsection}]'.",
+                    )
                     return True
             return False
 
diff --git a/tests/test_config.py b/tests/test_config.py
index b7a48e0..a1341d9 100644
--- a/tests/test_config.py
+++ b/tests/test_config.py
@@ -374,3 +374,103 @@ class UvHook(Hook):
     assert "uv:sources" in config.hooks
     assert "uv" not in config.packages
     assert "uv:sources" not in config.packages
+
+
+def test_hook_section_with_hyphen_delimiter_is_supported_but_deprecated(tmp_path, caplog):
+    """``[<namespace>-section]`` is still recognized as a hook section, with a deprecation warning.
+
+    Before the colon-as-delimiter fix, the convention was ``[<namespace>-section]``.
+    We keep that working for compatibility but log a deprecation pointing users to
+    the new ``<namespace>:section`` form.
+    """
+    from mxdev.config import Configuration
+    from mxdev.hooks import Hook
+
+    import logging
+
+    class MxmakeHook(Hook):
+        namespace = "mxmake"
+
+    config_content = """
+[settings]
+requirements-in = requirements.txt
+
+[mxmake-env]
+some-setting = value
+"""
+    config_file = tmp_path / "mx.ini"
+    config_file.write_text(config_content)
+
+    with caplog.at_level(logging.WARNING, logger="mxdev"):
+        config = Configuration(str(config_file), hooks=[MxmakeHook()])
+
+    assert "mxmake-env" in config.hooks
+    assert "mxmake-env" not in config.packages
+    assert any(
+        "mxmake-env" in r.message and "deprecated" in r.message.lower() for r in caplog.records
+    ), f"Expected deprecation warning for hyphen-delimited section, got: {[r.message for r in caplog.records]}"
+
+
+def test_legacy_namespace_with_trailing_hyphen_is_normalized(tmp_path, caplog):
+    """A hook declaring ``namespace = 'mxmake-'`` (trailing hyphen baked in) still works.
+
+    Legacy hooks (e.g. mxmake) declared their namespace with the delimiter included.
+    The matcher strips a trailing hyphen so the effective namespace is ``mxmake``,
+    keeping ``[mxmake-env]`` and ``[mxmake:env]`` both recognized.
+    """
+    from mxdev.config import Configuration
+    from mxdev.hooks import Hook
+
+    import logging
+
+    class LegacyMxmakeHook(Hook):
+        namespace = "mxmake-"
+
+    config_content = """
+[settings]
+requirements-in = requirements.txt
+
+[mxmake-env]
+some-setting = value
+
+[mxmake:files]
+other-setting = value
+"""
+    config_file = tmp_path / "mx.ini"
+    config_file.write_text(config_content)
+
+    with caplog.at_level(logging.WARNING, logger="mxdev"):
+        config = Configuration(str(config_file), hooks=[LegacyMxmakeHook()])
+
+    assert "mxmake-env" in config.hooks
+    assert "mxmake:files" in config.hooks
+    assert "mxmake-env" not in config.packages
+    assert "mxmake:files" not in config.packages
+
+
+def test_hyphen_prefix_without_delimiter_is_still_a_package(tmp_path):
+    """The original ``uvst.addon`` bug stays fixed even with hyphen support enabled.
+
+    A package whose name starts with the namespace but has no delimiter
+    (``uvst.addon`` for namespace ``uv``) must remain a package.
+    """
+    from mxdev.config import Configuration
+    from mxdev.hooks import Hook
+
+    class UvHook(Hook):
+        namespace = "uv"
+
+    config_content = """
+[settings]
+requirements-in = requirements.txt
+
+[uvst.addon]
+url = https://github.com/example/uvst.addon.git
+"""
+    config_file = tmp_path / "mx.ini"
+    config_file.write_text(config_content)
+
+    config = Configuration(str(config_file), hooks=[UvHook()])
+
+    assert "uvst.addon" in config.packages
+    assert "uvst.addon" not in config.hooks