[dependabot]

Bumps nanobind from 2.9 to 3.1.0.

Changelog

Sourced from nanobind's changelog.

Version 3.1.0 (Sep 28, 2026)

• Python subclasses can now combine one nanobind base with additional :ref:Python mixins <python_mixins>, including cooperative super() calls on CPython and PyPy. Inheriting from multiple nanobind bases remains unsupported. (discussion [#1436](https://github.com/wjakob/nanobind/issues/1436) <https://github.com/wjakob/nanobind/discussions/1436>__)

• The low-level instance API gained :cpp:func:nb::inst_python_derived() <inst_python_derived>, which reports whether a nanobind instance belongs to a Python subclass of the bound type. (commit c442d7 <https://github.com/wjakob/nanobind/commit/c442d7577f50c01b64b6204e2f55e0f84f60e635>__).

• Added new low-level functions :cpp:func:nb::keep_alive_obj() <keep_alive_obj> and :cpp:func:nb::keep_alive_cb() <keep_alive_cb>, which expose the mechanism behind the :cpp:class:nb::keep_alive <keep_alive> annotation. (commit 25192f <https://github.com/wjakob/nanobind/commit/25192f432f7d4dec4d24227c972226e075274621>__).

• The new function :cpp:func:intrusive_counter::ref_count() returns the reference count of an intrusively reference-counted object while it is owned by C++. (commit 1f26fb <https://github.com/wjakob/nanobind/commit/1f26fb363752decf0cf825039f213fbd1708ee09>__).

• Fixed stale trampoline override caches on PyPy. Changing an attribute of a nanobind type now correctly invalidates the caches of its Python subclasses. (commit 701c89 <https://github.com/wjakob/nanobind/commit/701c896751defe26e9a216e81f0e133339ed3251>__).

• The std::map/std::unordered_map and std::set type casters can now also handle containers like std::flat_map whose iterators return temporary values. (PR [#1434](https://github.com/wjakob/nanobind/issues/1434) <https://github.com/wjakob/nanobind/pull/1434>__).

• The :ref:Bazel documentation <bazel> was rewritten and now presents an approach based on the Bazel Central Registry. (PR [#1435](https://github.com/wjakob/nanobind/issues/1435) <https://github.com/wjakob/nanobind/pull/1435>__).

• Miscellaneous minor improvements. (PRs [#1429](https://github.com/wjakob/nanobind/issues/1429) <https://github.com/wjakob/nanobind/pull/1429>, [#1428](https://github.com/wjakob/nanobind/issues/1428) <https://github.com/wjakob/nanobind/pull/1428>, [#1414](https://github.com/wjakob/nanobind/issues/1414) <https://github.com/wjakob/nanobind/pull/1414>, [#1431](https://github.com/wjakob/nanobind/issues/1431) <https://github.com/wjakob/nanobind/issues/1431>)

Version 3.0.1 (Aug 28, 2026)

• Fixed an issue where the std::chrono::duration caster interpreted a Python float even when implicit conversion was not desired. (PR [#1420](https://github.com/wjakob/nanobind/issues/1420) <https://github.com/wjakob/nanobind/pull/1420>__).

• Minor tweak to the NB_SLOT_ALIAS macro so that clang-cl can compile nanobind 3.0.0 code on Windows. This compiler is now also tested by the CI.

... (truncated)

Commits

• 68480a9 v3.1.0 release
• 32c595d Support Python mixins alongside a nanobind base
• 701c896 Fix trampoline cache invalidation of subclasses on PyPy
• 1f26fb3 Add intrusive_counter::ref_count()
• c1cd12b Overhaul Bazel documentation
• 65b8067 Update nb_set.h
• e3daa99 Fix the reference type in dict_caster's item loop
• 991c73a Expose __doc__ on bound methods via a getset descriptor
• c3ec792 Fix conversion warning with 32-bit Eigen::Index
• 5775550 Remove verbose CMake notification message
• Additional commits viewable in compare view

Dependabot will resolve any conflicts with this PR as long as you don't alter it yourself. You can also trigger a rebase manually by commenting @dependabot rebase.

---

Dependabot commands and options

You can trigger Dependabot actions by commenting on this PR:

• @dependabot rebase will rebase this PR
• @dependabot recreate will recreate this PR, overwriting any edits that have been made to it
• @dependabot show <dependency name> ignore conditions will show all of the ignore conditions of the specified dependency
• @dependabot ignore this major version will close this PR and stop Dependabot creating any more for this major version (unless you reopen the PR or upgrade to it yourself)
• @dependabot ignore this minor version will close this PR and stop Dependabot creating any more for this minor version (unless you reopen the PR or upgrade to it yourself)
• @dependabot ignore this dependency will close this PR and stop Dependabot creating any more for this dependency (unless you reopen the PR or upgrade to it yourself)