diff --git a/.github/workflows/test.yaml b/.github/workflows/test.yaml
index 88e39d364..cec7384a0 100644
--- a/.github/workflows/test.yaml
+++ b/.github/workflows/test.yaml
@@ -10,7 +10,7 @@ jobs:
       fail-fast: true
       matrix:
         os:  [ubuntu, macos]
-        version: ["3.10", "3.11", "3.12", "3.13"]
+        version: ["3.11", "3.12", "3.13"]
     runs-on: ${{ matrix.os }}-latest
     steps:
       - uses: answerdotai/workflows/nbdev3-ci@master
@@ -20,7 +20,7 @@ jobs:
       - name: test Python modules
         run: pytest -q
       - name: test docs build
-        if: ${{ (github.event_name == 'pull_request' || github.event_name == 'workflow_dispatch') && matrix.version == '3.10' && matrix.os == 'ubuntu' }}
+        if: ${{ (github.event_name == 'pull_request' || github.event_name == 'workflow_dispatch') && matrix.version == '3.11' && matrix.os == 'ubuntu' }}
         run: |
           set -ux
           wget -q $(curl https://latest.fast.ai/pre/quarto-dev/quarto-cli/linux-amd64.deb)
diff --git a/nbdev/config.py b/nbdev/config.py
index dcce9eb9a..c42278e2e 100644
--- a/nbdev/config.py
+++ b/nbdev/config.py
@@ -22,8 +22,7 @@
 from IPython.display import Markdown
 from fastcore.nbio import read_nb,NbCell
 
-try: import tomllib
-except ImportError: import tomli as tomllib
+import tomllib
 
 # %% ../nbs/api/01_config.ipynb #117128e6
 pyproject_nm = 'pyproject.toml'
diff --git a/nbdev/serve.py b/nbdev/serve.py
index 91626b29c..bc5b6217a 100644
--- a/nbdev/serve.py
+++ b/nbdev/serve.py
@@ -8,13 +8,12 @@
 __all__ = ['proc_nbs']
 
 # %% ../nbs/api/17_serve.ipynb #6899a335
-import ast,subprocess,threading,sys
+import ast
 from shutil import rmtree,copy2
 from fnmatch import fnmatch
 
 from fastcore.utils import *
 from fastcore.parallel import parallel
-from fastcore.script import call_parse
 from fastcore.meta import delegates
 
 from .config import get_config
@@ -95,7 +94,6 @@ def proc_nbs(
     _rm_stale(cache, path)
 
     files = files.map(_proc_file, cache=cache, path=path).filter()
-    kw = {} if in_notebook() else {'method':'spawn'}
-    parallel(nbdev.serve_drv.main, files, n_workers=n_workers, pause=0.01, **kw)
+    parallel(nbdev.serve_drv.main, files, n_workers=n_workers, pause=0.01, max_tasks_per_child=1)
     if cache.exists(): cache.touch()
     return cache
diff --git a/nbdev/test.py b/nbdev/test.py
index 490020dec..f276c577e 100644
--- a/nbdev/test.py
+++ b/nbdev/test.py
@@ -156,7 +156,7 @@ def nbdev_test(
     cell_timing_min:float=None, # Print cells slower than this many seconds (default `cell_timing_min` config, else none)
     **kwargs
 ):
-    "Test in parallel notebooks matching `path`, passing along `flags`"
+    "Test in parallel notebooks matching `path`, each in a process of its own, passing along `flags`"
     if path and not Path(path).exists(): kwargs['path_glob'],path = os.path.abspath(path),Path.cwd()
     cfg = get_config(Path(path).resolve() if path else None)
     cell_timeout,cell_timing_min = ifnone(cell_timeout, cfg.cell_timeout),ifnone(cell_timing_min, cfg.get('cell_timing_min'))
@@ -168,8 +168,6 @@ def nbdev_test(
     if len(files)==0: return print('No files were eligible for testing')
 
     if n_workers is None: n_workers = 0 if len(files)==1 else min(num_cpus(), 8)
-    if in_notebook(): kw = {'method':'spawn'} if os.name=='nt' or sys.platform=='darwin' else {'method':'forkserver'}
-    else: kw = {'method':'spawn'} if sys.platform=='darwin' else {}
     wd_pth = cfg.nbs_path
     with working_directory(wd_pth if (wd_pth and wd_pth.exists()) else os.getcwd()):
         setup = cfg.get('test_setup')
@@ -177,7 +175,7 @@ def nbdev_test(
         try:
             results = parallel(test_nb, files, skip_flags=skip_flags, force_flags=force_flags, n_workers=n_workers,
                 basepath=cfg.config_path, pause=pause, do_print=do_print, verbose=verbose, save=save,
-                cell_timeout=cell_timeout or None, cell_timing_min=cell_timing_min, **kw)
+                cell_timeout=cell_timeout or None, cell_timing_min=cell_timing_min, max_tasks_per_child=1)
         except KeyboardInterrupt:
             sys.stderr.write('\nnbdev-test interrupted; in-flight notebook stacks shown above\n')
             sys.exit(130)
diff --git a/nbs/api/01_config.ipynb b/nbs/api/01_config.ipynb
index 4b4e3ed62..878197e9f 100644
--- a/nbs/api/01_config.ipynb
+++ b/nbs/api/01_config.ipynb
@@ -41,8 +41,7 @@
     "from IPython.display import Markdown\n",
     "from fastcore.nbio import read_nb,NbCell\n",
     "\n",
-    "try: import tomllib\n",
-    "except ImportError: import tomli as tomllib"
+    "import tomllib"
    ]
   },
   {
@@ -1287,10 +1286,13 @@
   "solveit": {
    "default_code": true,
    "mode": "learning",
+   "reasoning_effort": "h",
+   "reasoning_model": "anthropic/claude-opus-5-5",
+   "standard_effort": "m",
+   "standard_model": "openai/gpt-6-luna",
    "use_fence": false,
    "use_thinking": false,
-   "use_tools": true,
-   "ver": 2
+   "use_tools": true
   }
  },
  "nbformat": 4,
diff --git a/nbs/api/12_test.ipynb b/nbs/api/12_test.ipynb
index 951ef4927..8ce38d1f2 100644
--- a/nbs/api/12_test.ipynb
+++ b/nbs/api/12_test.ipynb
@@ -357,7 +357,7 @@
     "    cell_timing_min:float=None, # Print cells slower than this many seconds (default `cell_timing_min` config, else none)\n",
     "    **kwargs\n",
     "):\n",
-    "    \"Test in parallel notebooks matching `path`, passing along `flags`\"\n",
+    "    \"Test in parallel notebooks matching `path`, each in a process of its own, passing along `flags`\"\n",
     "    if path and not Path(path).exists(): kwargs['path_glob'],path = os.path.abspath(path),Path.cwd()\n",
     "    cfg = get_config(Path(path).resolve() if path else None)\n",
     "    cell_timeout,cell_timing_min = ifnone(cell_timeout, cfg.cell_timeout),ifnone(cell_timing_min, cfg.get('cell_timing_min'))\n",
@@ -369,8 +369,6 @@
     "    if len(files)==0: return print('No files were eligible for testing')\n",
     "\n",
     "    if n_workers is None: n_workers = 0 if len(files)==1 else min(num_cpus(), 8)\n",
-    "    if in_notebook(): kw = {'method':'spawn'} if os.name=='nt' or sys.platform=='darwin' else {'method':'forkserver'}\n",
-    "    else: kw = {'method':'spawn'} if sys.platform=='darwin' else {}\n",
     "    wd_pth = cfg.nbs_path\n",
     "    with working_directory(wd_pth if (wd_pth and wd_pth.exists()) else os.getcwd()):\n",
     "        setup = cfg.get('test_setup')\n",
@@ -378,7 +376,7 @@
     "        try:\n",
     "            results = parallel(test_nb, files, skip_flags=skip_flags, force_flags=force_flags, n_workers=n_workers,\n",
     "                basepath=cfg.config_path, pause=pause, do_print=do_print, verbose=verbose, save=save,\n",
-    "                cell_timeout=cell_timeout or None, cell_timing_min=cell_timing_min, **kw)\n",
+    "                cell_timeout=cell_timeout or None, cell_timing_min=cell_timing_min, max_tasks_per_child=1)\n",
     "        except KeyboardInterrupt:\n",
     "            sys.stderr.write('\\nnbdev-test interrupted; in-flight notebook stacks shown above\\n')\n",
     "            sys.exit(130)\n",
@@ -500,10 +498,13 @@
   "solveit": {
    "default_code": false,
    "mode": "concise",
+   "reasoning_effort": "h",
+   "reasoning_model": "anthropic/claude-opus-5-5",
+   "standard_effort": "m",
+   "standard_model": "openai/gpt-6-luna",
    "use_fence": false,
    "use_thinking": true,
-   "use_tools": true,
-   "ver": 2
+   "use_tools": true
   }
  },
  "nbformat": 4,
diff --git a/nbs/api/16_migrate.ipynb b/nbs/api/16_migrate.ipynb
index 51827d18c..2ab25a953 100644
--- a/nbs/api/16_migrate.ipynb
+++ b/nbs/api/16_migrate.ipynb
@@ -1380,8 +1380,7 @@
    "outputs": [],
    "source": [
     "from configparser import ConfigParser\n",
-    "try: import tomllib\n",
-    "except ImportError: import tomli as tomllib"
+    "import tomllib"
    ]
   },
   {
@@ -1542,7 +1541,16 @@
    ]
   }
  ],
- "metadata": {},
+ "metadata": {
+  "solveit": {
+   "mode": "learning",
+   "reasoning_effort": "h",
+   "reasoning_model": "anthropic/claude-opus-5-5",
+   "standard_effort": "m",
+   "standard_model": "openai/gpt-6-luna",
+   "use_thinking": false
+  }
+ },
  "nbformat": 4,
  "nbformat_minor": 5
 }
diff --git a/nbs/api/17_serve.ipynb b/nbs/api/17_serve.ipynb
index 089cc79e7..9b4c1e991 100644
--- a/nbs/api/17_serve.ipynb
+++ b/nbs/api/17_serve.ipynb
@@ -29,13 +29,12 @@
    "outputs": [],
    "source": [
     "#| export\n",
-    "import ast,subprocess,threading,sys\n",
+    "import ast\n",
     "from shutil import rmtree,copy2\n",
     "from fnmatch import fnmatch\n",
     "\n",
     "from fastcore.utils import *\n",
     "from fastcore.parallel import parallel\n",
-    "from fastcore.script import call_parse\n",
     "from fastcore.meta import delegates\n",
     "\n",
     "from nbdev.config import get_config\n",
@@ -223,8 +222,7 @@
     "    _rm_stale(cache, path)\n",
     "\n",
     "    files = files.map(_proc_file, cache=cache, path=path).filter()\n",
-    "    kw = {} if in_notebook() else {'method':'spawn'}\n",
-    "    parallel(nbdev.serve_drv.main, files, n_workers=n_workers, pause=0.01, **kw)\n",
+    "    parallel(nbdev.serve_drv.main, files, n_workers=n_workers, pause=0.01, max_tasks_per_child=1)\n",
     "    if cache.exists(): cache.touch()\n",
     "    return cache"
    ]
@@ -268,7 +266,16 @@
    "source": []
   }
  ],
- "metadata": {},
+ "metadata": {
+  "solveit": {
+   "mode": "learning",
+   "reasoning_effort": "h",
+   "reasoning_model": "anthropic/claude-opus-5-5",
+   "standard_effort": "m",
+   "standard_model": "openai/gpt-6-luna",
+   "use_thinking": false
+  }
+ },
  "nbformat": 4,
  "nbformat_minor": 5
 }
diff --git a/pyproject.toml b/pyproject.toml
index 3c4968e7f..0c06eaa2f 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -6,7 +6,7 @@ build-backend = "setuptools.build_meta"
 name = "nbdev"
 description = "Create delightful software with Jupyter Notebooks"
 readme = "README.md"
-requires-python = ">=3.10"
+requires-python = ">=3.11"
 license = "Apache-2.0"
 authors = [{name = "Jeremy Howard and the fast.ai community", email = "j@fast.ai"}]
 keywords = ["nbdev", "fastai", "jupyter", "notebook", "export"]
@@ -18,8 +18,8 @@ classifiers = [
     "Programming Language :: Python :: 3 :: Only",
 ]
 dynamic = ["version"]
-dependencies = [ "fastcore>=2.2.28", "execnb>=0.3.3", "astunparse", "ghapi>=2.0.2", "watchdog", "asttokens",
-    "setuptools", "build", "fastgit>=0.0.7", "pyyaml", "tomli; python_version < '3.11'", ]
+dependencies = [ "fastcore>=2.2.39", "execnb>=0.3.3", "astunparse", "ghapi>=2.0.2", "watchdog", "asttokens",
+    "setuptools", "build", "fastgit>=0.0.7", "pyyaml", ]
 
 [project.optional-dependencies]
 dev = [ "ipywidgets", "nbdev-numpy", "nbdev-stdlib", "pandas", "matplotlib", "black", "svg.py", "pysym2md>=0.0.6", "llms-txt", "sphinx", "plum-dispatch", "nbclient", "ipykernel", "pytest", ]
diff --git a/tests/test_test.py b/tests/test_test.py
new file mode 100644
index 000000000..2c8f22a78
--- /dev/null
+++ b/tests/test_test.py
@@ -0,0 +1,9 @@
+from fastcore.nbio import new_nb, write_nb, mk_cell
+from nbdev.test import nbdev_test
+
+
+def test_fresh_process_per_notebook(tmp_path):
+    "State one notebook leaves on an imported module never reaches the next, even on a single worker"
+    write_nb(new_nb([mk_cell('import json\njson.leak = 1')]), tmp_path/'a.ipynb')
+    write_nb(new_nb([mk_cell('import json\nassert not hasattr(json, "leak")')]), tmp_path/'b.ipynb')
+    nbdev_test(path=tmp_path, n_workers=1)