diff --git a/CHANGELOG.md b/CHANGELOG.md
index 5cdb02e..443e62d 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -4,6 +4,10 @@
 
 ### Added
 
+- `sp.reset()`, for test suites: it forgets the configuration and what was recorded but keeps the
+  instrumentation, so a library's `@sp.profile` functions record again after the next `setup()`.
+  Before, the private `ProfileManager._reset()` dropped them for good, and calling one before the
+  next `setup()` raised `AttributeError`.
 - Opt-in region tags, so a library can ship its own instrumentation switched off by default:
   it calls `sp.register_opt_in_tag("mylib")` and tags its regions (`region`, `profile`,
   `define_region` and `instrument` take `tags=`). A run records them only when it enables the
@@ -97,6 +101,16 @@
 
 ### Changed
 
+- A decorated function whose region is disabled (before `setup()`, or behind an opt-in tag that is
+  off) calls straight through: it skips `metadata` and no longer starts recursive tracing.
+- `register_opt_in_tag()` also re-resolves the regions and decorated functions that already exist,
+  so a library may call it after its own imports.
+- `sp.profile` keeps the decorated function's signature for type checkers, and `with sp.region(...)`
+  type-checks (`BaseProfileRegion` declares `__enter__`/`__exit__`).
+- `import scope_profiler` no longer imports h5py or `importlib.metadata`, about half its import
+  time on top of NumPy.
+- The docs no longer claim that disabled instrumentation costs nothing: it costs one Python call.
+- The `pproc` extra takes any `maxplotlibx >= 0.1.9` instead of pinning 0.1.9.
 - The documentation site moved from Sphinx to Astro + Starlight with the shared
   [starlight-theme](https://github.com/max-models/starlight-theme): the pages
   are Markdown/MDX in `docs/src/content/docs/`, the tutorials Jupyter
diff --git a/CMakeLists.txt b/CMakeLists.txt
index aabdac1..e534694 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -1,6 +1,6 @@
 cmake_minimum_required(VERSION 3.15)
 
-project(scope-profiler VERSION 0.7.4 LANGUAGES C CXX)
+project(scope-profiler VERSION 0.7.5 LANGUAGES C CXX)
 
 include(GNUInstallDirs)
 include(CMakePackageConfigHelpers)
diff --git a/configuration.md b/configuration.md
index ebcdbb9..8c60730 100644
--- a/configuration.md
+++ b/configuration.md
@@ -403,8 +403,9 @@ ProfileManager.setup(
 ## Library regions that are off by default
 
 A library can ship its own regions without them showing up in every
-profile of the code that uses it. It registers an *opt-in tag* once, at
-import time, and tags its regions with it:
+profile of the code that uses it. It registers an *opt-in tag* once, in its
+package `__init__` (before or after its own imports), and tags its regions
+with it:
 
 ```python
 # mylib/__init__.py
@@ -422,9 +423,11 @@ def fft(x):
 ```
 
 `sp.instrument(module, tags=("mylib",))` tags every function it wraps.
-These regions stay disabled, and a decorated function stays unwrapped, until
-the run enables the tag. Untagged regions and regions with other tags are
-unaffected. The application enables it without editing the library, in any
+These regions stay disabled until the run enables the tag; a disabled
+decorated function calls straight through, skipping `metadata` and recursive
+tracing. Either way, instrumentation that is off costs one extra Python call
+(roughly 0.1–0.3 µs), so keep it to operations that take microseconds or
+more. Untagged regions and regions with other tags are unaffected. The application enables it without editing the library, in any
 of these ways (they add up):
 
 - `setup(enable_tags=["mylib"])` or `session(enable_tags=["mylib"])`, or
@@ -438,6 +441,19 @@ of these ways (they add up):
 records when any of them is enabled. Naming an opt-in tag in
 `region_tags` (`--tag`) enables it too.
 
+A test suite that profiles in more than one test resets the profiler between
+them with `sp.reset()`. It forgets the configuration and what was recorded
+but keeps the instrumentation, as importing the library left it, so the
+library's decorated functions record again after the next `setup()`:
+
+```python
+@pytest.fixture(autouse=True)
+def _fresh_profiler():
+    sp.reset()
+    yield
+    sp.reset()
+```
+
 ## Recursive profiling of decorated entrypoints
 
 Set `recursive_profile=True` to record Python function calls made inside
diff --git a/docs/src/content/docs/reference/api.mdx b/docs/src/content/docs/reference/api.mdx
index cc1a7da..9fffcf8 100644
--- a/docs/src/content/docs/reference/api.mdx
+++ b/docs/src/content/docs/reference/api.mdx
@@ -42,6 +42,10 @@ and passes `tags=("mylib",)` to `region`, `profile`, `define_region` or
 `SCOPE_PROFILER_ENABLE_TAGS=mylib` or `scope-profiler run --enable-tag mylib`.
 The registry is process-wide and shared by every manager.
 
+Test suites reset the profiler between tests with `sp.reset()`, which keeps
+the instrumentation (decorated functions and `define_region` definitions)
+so that it records again after the next `setup()`.
+
 ## ProfileManager
 
 The main entry point for all profiling operations. Class methods provide the
diff --git a/pyproject.toml b/pyproject.toml
index b2250d9..62628bb 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -5,7 +5,7 @@ requires = [ "setuptools", "wheel" ]
 
 [project]
 name = "scope-profiler"
-version = "0.7.4"
+version = "0.7.5"
 description = "Profile code regions in python, optionally with LIKWID markers."
 readme = "README.md"
 keywords = [ "python" ]
@@ -77,7 +77,7 @@ optional-dependencies.pproc = [
   "ipykernel",
   "jupyterlab",
   "matplotlib",
-  "maxplotlibx == 0.1.9",
+  "maxplotlibx >= 0.1.9",
   "pandas",
   "plotly",
   "pyarrow",
diff --git a/src/scope_profiler/__init__.py b/src/scope_profiler/__init__.py
index 839bfcc..920ee4f 100644
--- a/src/scope_profiler/__init__.py
+++ b/src/scope_profiler/__init__.py
@@ -1,6 +1,5 @@
 """scope-profiler: lightweight region-based profiling for Python and HPC applications."""
 
-from importlib.metadata import PackageNotFoundError, version
 from typing import TYPE_CHECKING, Any
 
 from scope_profiler.call_stack import (
@@ -79,21 +78,19 @@
 recorded_regions = ProfileManager.recorded_regions
 region = ProfileManager.region
 register_opt_in_tag = ProfileManager.register_opt_in_tag
+reset = ProfileManager.reset
 registered_regions = ProfileManager.registered_regions
 session = ProfileManager.session
 setup = ProfileManager.setup
 setup_from_env = ProfileManager.setup_from_env
 run = ProfileManager.run
 
-try:
-    __version__ = version("scope-profiler")
-except PackageNotFoundError:
-    __version__ = "unknown"
-
 # Keep these imports visible to language servers without importing the optional
 # plotting/reporting dependencies at runtime.  Dynamic module attributes are
 # otherwise invisible to hover, completion, and static type checkers.
 if TYPE_CHECKING:
+    __version__: str
+
     from scope_profiler.chrome_trace_export import export_chrome_trace
     from scope_profiler.html_report import create_html_report
     from scope_profiler.inspection import collect_file_metadata, inspect_file
@@ -200,6 +197,7 @@
     "region_factory",
     "register_opt_in_tag",
     "registered_regions",
+    "reset",
     "run",
     "session",
     "setup",
@@ -214,6 +212,15 @@
 
 def __getattr__(name: str) -> Any:
     """Load optional top-level helpers only when they are first used."""
+    if name == "__version__":
+        # Looked up on first use: importlib.metadata is about half the cost of
+        # ``import scope_profiler`` on top of NumPy.
+        from importlib.metadata import PackageNotFoundError, version
+
+        try:
+            return version("scope-profiler")
+        except PackageNotFoundError:
+            return "unknown"
     if name in {
         "collect_region_statistics",
         "collect_roofline_points",
diff --git a/src/scope_profiler/h5reader.py b/src/scope_profiler/h5reader.py
index a9d40e6..734a596 100644
--- a/src/scope_profiler/h5reader.py
+++ b/src/scope_profiler/h5reader.py
@@ -12,7 +12,6 @@
 from copy import copy
 from pathlib import Path
 
-import h5py
 import numpy as np
 
 from scope_profiler.h5schema import HDF5SchemaError, migrate_schema, read_schema_version
@@ -39,6 +38,10 @@ class CorruptProfileError(OSError):
 
 def _open_h5(file_path):
     """Open a profiling file, reporting an unreadable one in context."""
+    # Imported here, not at module level: ``import scope_profiler`` (and so
+    # every library that ships regions) should not pay for h5py up front.
+    import h5py
+
     try:
         return h5py.File(file_path, "r")
     except OSError as exc:
diff --git a/src/scope_profiler/profile_manager.py b/src/scope_profiler/profile_manager.py
index 8ee28c3..de1a4c5 100644
--- a/src/scope_profiler/profile_manager.py
+++ b/src/scope_profiler/profile_manager.py
@@ -13,13 +13,13 @@
 import sysconfig
 import threading
 import warnings
-from collections.abc import Callable
+from collections.abc import Callable, Iterable
 from contextlib import ContextDecorator, contextmanager
 from contextvars import ContextVar
 from enum import Enum, auto
 from time import perf_counter_ns
 from types import FrameType
-from typing import TYPE_CHECKING, ClassVar, NamedTuple
+from typing import TYPE_CHECKING, ClassVar, NamedTuple, ParamSpec, TypeVar, overload
 
 import numpy as np
 
@@ -63,6 +63,8 @@
 _PAYLOAD_TAG = 0x5C09
 _WRITE_TOKEN_TAG = 0x5C0A
 _UNSET = object()
+_P = ParamSpec("_P")
+_R = TypeVar("_R")
 
 # Tags registered with register_opt_in_tag(). Libraries register them at
 # import time, so this outlives every setup() and reset, and is shared by all
@@ -697,13 +699,29 @@ def solve(): ...
         ``"*"`` enables every opt-in tag. Listing the tag in ``region_tags``
         enables it too.
 
-        A disabled decorated function is left unwrapped, so instrumentation
-        that is off costs nothing per call.
+        Regions and decorated functions that already exist pick the change up,
+        so the call may come after the library's own imports.
+
+        Instrumentation that is off costs one extra Python call (roughly
+        0.1-0.3 µs per call), so keep it to operations that take microseconds
+        or more.
         """
         for tag in tags:
             if not isinstance(tag, str) or not tag:
                 raise TypeError(f"opt-in tags must be non-empty strings, got {tag!r}")
-        _OPT_IN_TAGS.update(tags)
+        new = set(tags) - _OPT_IN_TAGS
+        _OPT_IN_TAGS.update(new)
+        if new and cls._configured:
+            cls._rebind_tagged(new)
+
+    @classmethod
+    def _rebind_tagged(cls, tags) -> None:
+        """Re-resolve the existing regions and decorators that carry ``tags``."""
+        for name in [n for n, r in cls._regions.items() if tags.intersection(r.tags)]:
+            del cls._regions[name]
+        for name, func, _bound, region_tags in cls._decorated_functions():
+            if region_tags and tags.intersection(region_tags):
+                cls._bind_decorated_region(name, func, _bound, region_tags)
 
     #: Original name for :meth:`region`, kept so existing instrumentation
     #: keeps working unchanged. Same object, not a forwarding wrapper: this
@@ -934,8 +952,21 @@ def _bind_decorated_region(
                     )
         _bound[0] = region
         _bound[1] = region.wrap(func)
+        _bound[2] = isinstance(region, DisabledProfileRegion)
         return region
 
+    @classmethod
+    def _decorated_functions(cls):
+        """Yield ``(name, func, _bound, tags)`` for every @profile wrapper."""
+        for name, entries in cls._decorators.items():
+            for entry in entries:
+                yield (name, *entry)
+
+    @overload
+    @classmethod
+    def profile(cls, region_name: Callable[_P, _R]) -> Callable[_P, _R]: ...
+
+    @overload
     @classmethod
     def profile(
         cls,
@@ -943,8 +974,18 @@ def profile(
         recursive: bool | None = None,
         metadata=None,
         record_outcome: bool = False,
+        tags: Iterable[str] | None = None,
+    ) -> Callable[[Callable[_P, _R]], Callable[_P, _R]]: ...
+
+    @classmethod
+    def profile(
+        cls,
+        region_name=None,
+        recursive=None,
+        metadata=None,
+        record_outcome=False,
         tags=None,
-    ) -> Callable:
+    ):
         """
         Decorator factory for profiling a function.
 
@@ -979,7 +1020,10 @@ def profile(
         ``ProfileManager.setup()`` after decoration re-binds the wrapper to
         the new region class at zero per-call cost.  This means
         ``@ProfileManager.profile`` can be applied at class-definition time
-        even when ``setup()`` is called later.
+        even when ``setup()`` is called later. While its region is disabled
+        (before ``setup()``, or behind an opt-in tag that is off) the wrapper
+        calls the function directly, skipping ``metadata`` and recursive
+        tracing.
         """
 
         region_tags = None if tags is None else tuple(tags)
@@ -989,7 +1033,7 @@ def decorator(func):
             # _bound[1] is the inner callable produced by region.wrap(func).
             # It is replaced (without touching the outer wrapper) whenever
             # set_config() is called, so there is no per-call rebind check.
-            _bound = [None, None]  # [region, wrapped_func]
+            _bound = [None, func, True]  # [region, wrapped_func, disabled]
             recursive_override = recursive
 
             def invoke(*args, **kwargs):
@@ -1024,11 +1068,10 @@ def _invoke_with_metadata(values, args, kwargs):
             cls._bind_decorated_region(name, func, _bound, region_tags)
             cls._decorated_codes.add(func.__code__)
 
-            # Register so set_config() can rebind without a per-call check.
-            cls._decorators.setdefault(name, []).append((func, _bound, region_tags))
-
             @functools.wraps(func)
             def wrapper(*args, **kwargs):
+                if _bound[2]:
+                    return _bound[1](*args, **kwargs)
                 recursive_enabled = cls._config.recursive_profile
                 if recursive_override is not None:
                     recursive_enabled = recursive_override
@@ -1057,6 +1100,8 @@ def wrapper(*args, **kwargs):
                     sys.setprofile(prev_profiler)
                     state.depth -= 1
 
+            # Register so set_config() can rebind without a per-call check.
+            cls._decorators.setdefault(name, []).append((func, _bound, region_tags))
             return wrapper
 
         # Support @ProfileManager.profile without parentheses
@@ -2461,6 +2506,13 @@ def finalize_at_exit():
             if cls._configured:
                 cls.finalize()
 
+        if not cls._config.deactivate_file_output:
+            # The hook writes HDF5 at exit, and h5py must not be imported for
+            # the first time during interpreter shutdown (it crashes). Importing
+            # it now also registers its own exit hook before ours, so ours runs
+            # first.
+            import h5py  # noqa: F401
+
         cls._auto_finalize_callback = finalize_at_exit
         atexit.register(finalize_at_exit)
 
@@ -2856,9 +2908,8 @@ def set_config(cls, config: ProfilingConfig) -> None:
         cls._update_region_cls()  # Set the proper region class
         # Rebind all registered decorator wrappers to the new region class.
         # This is the only place rebinding happens — there is no per-call check.
-        for name, entries in cls._decorators.items():
-            for func, _bound, tags in entries:
-                cls._bind_decorated_region(name, func, _bound, tags)
+        for name, func, _bound, tags in cls._decorated_functions():
+            cls._bind_decorated_region(name, func, _bound, tags)
         for name, (functions, tags) in cls._region_definitions.items():
             cls.region(name, functions=functions, tags=tags)
 
@@ -2922,11 +2973,31 @@ def _reset_config(cls) -> None:
         cls._lifecycle_state = _LifecycleState.INACTIVE
 
     @classmethod
-    def _reset(cls) -> None:
+    def reset(cls) -> None:
+        """Forget the configuration and everything recorded; keep the instrumentation.
+
+        Leaves the manager as importing the instrumented code does: not
+        configured, every region disabled until the next :meth:`setup`.
+        Decorated functions and :meth:`define_region` definitions stay
+        registered, and decorated functions call straight through until then.
+        Meant for test suites that profile in more than one test::
+
+            @pytest.fixture(autouse=True)
+            def _fresh_profiler():
+                sp.reset()
+                yield
+                sp.reset()
+        """
         cls._reset_regions()
         cls._reset_config()
-        # Back to the state a fresh import leaves behind: no configuration,
-        # and regions disabled until setup() or get_config() says otherwise.
         cls._region_cls = DisabledProfileRegion
+        for _name, func, _bound, _tags in cls._decorated_functions():
+            _bound[:] = [None, func, True]
+
+    @classmethod
+    def _reset(cls) -> None:
+        # reset(), and forget every decorator and definition too, so that no
+        # test of scope-profiler itself sees another test's instrumentation.
+        cls.reset()
         cls._decorators.clear()
         cls._region_definitions.clear()
diff --git a/src/scope_profiler/region_profiler.py b/src/scope_profiler/region_profiler.py
index cef7fd1..676697e 100644
--- a/src/scope_profiler/region_profiler.py
+++ b/src/scope_profiler/region_profiler.py
@@ -7,6 +7,7 @@
 import threading
 import types
 from time import perf_counter_ns
+from typing import TYPE_CHECKING
 
 import numpy as np
 
@@ -15,6 +16,9 @@
 from scope_profiler.perf_events import PerfEventGroup, PerfEventTotals
 from scope_profiler.profile_config import ProfilingConfig
 
+if TYPE_CHECKING:
+    from typing_extensions import Self  # typing.Self needs Python 3.11
+
 # Parsed module ASTs, memoized by filename. Capturing a region's source only
 # runs once per region name (see BaseProfileRegion.set_source), but a file can
 # define many regions, so the parse itself is cached rather than repeated.
@@ -462,6 +466,16 @@ def wrapper(*args, **kwargs):
 
         return wrapper
 
+    # Declared here, with their types, so that ``with ProfileManager.region(...)``
+    # type-checks; every region class overrides both.
+    def __enter__(self) -> "Self":
+        """Start timing a ``with`` block."""
+        raise NotImplementedError
+
+    def __exit__(self, exc_type, exc_value, traceback) -> None:
+        """Stop timing a ``with`` block."""
+        raise NotImplementedError
+
     def append(self, start: float, end: float) -> None:
         """Append a start/end time pair to the buffer, growing it if needed."""
 
diff --git a/src/scope_profiler/tests/test_opt_in_tags.py b/src/scope_profiler/tests/test_opt_in_tags.py
index b8412a4..c0fd100 100644
--- a/src/scope_profiler/tests/test_opt_in_tags.py
+++ b/src/scope_profiler/tests/test_opt_in_tags.py
@@ -1,5 +1,7 @@
 """Opt-in region tags: library instrumentation that is off unless enabled."""
 
+import sys
+
 import pytest
 
 import scope_profiler as sp
@@ -195,3 +197,70 @@ def test_cli_enable_tag(tmp_path):
 
     assert set(read_h5(off).region_names) == {"user.step"}
     assert set(read_h5(on).region_names) == {"mylib.kernel", "user.step"}
+
+
+def test_reset_keeps_decorated_functions_for_the_next_setup():
+    sp.register_opt_in_tag("mylib")
+
+    @sp.profile("mylib.solve", tags=("mylib",))
+    def solve():
+        return 1
+
+    sp.reset()
+    assert solve() == 1  # calls straight through while nothing is configured
+    ProfileManager.setup(output=None, enable_tags=["mylib"])
+    solve()
+    results = ProfileManager.finalize(verbose=False, return_results=True)
+
+    assert results["mylib.solve"].num_calls == 1
+
+
+def test_private_reset_forgets_decorated_functions():
+    @sp.profile("solve")
+    def solve():
+        pass
+
+    ProfileManager._reset()
+    ProfileManager.setup(output=None)
+
+    assert "solve" not in sp.registered_regions()
+
+
+def test_disabled_decorated_function_skips_metadata_and_tracing():
+    sp.register_opt_in_tag("mylib")
+    metadata_calls = []
+    profilers = []
+
+    def metadata(*args, **kwargs):
+        metadata_calls.append(args)
+        return {"n": 1}
+
+    @sp.profile("mylib.solve", tags=("mylib",), metadata=metadata, recursive=True)
+    def solve():
+        profilers.append(sys.getprofile())
+
+    before = sys.getprofile()
+    ProfileManager.setup(output=None)
+    solve()
+    ProfileManager.finalize(verbose=False)
+
+    assert metadata_calls == []
+    assert profilers == [before]
+
+
+def test_registering_a_tag_late_disables_existing_instrumentation():
+    @sp.profile("mylib.solve", tags=("mylib",))
+    def solve():
+        pass
+
+    ProfileManager.setup(output=None)
+    with sp.region("mylib.kernel", tags=("mylib",)):
+        pass
+    sp.register_opt_in_tag("mylib")
+    solve()
+    with sp.region("mylib.kernel", tags=("mylib",)):
+        pass
+    results = ProfileManager.finalize(verbose=False, return_results=True)
+
+    assert "mylib.solve" not in results.region_names
+    assert "mylib.kernel" not in results.region_names