Add support python 3.15

[p-r-a-v-i-n]

blocked until cryptography 50.0.3 or 51 ships

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Please explain the changes you are proposing.

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Related issue(s): #issue-number
Branch: python315

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[oberstet]

pls see #1963

[p-r-a-v-i-n]

I would need some time to get back on this, may be till 10th oct.

[oberstet]

rgd the CI fails: this is more likely a PyPy ABI/compatibility issue in the cryptography binary than a bug in Autobahn or Twisted. The key clue is the undefined symbol PyPy_DecRef.

Suspect	Likelihood	Reason
cryptography build or packaging	High	The failing component is its compiled Rust extension, which must link correctly against the PyPy runtime.
PyPy 3.12 runtime / ABI	High	The missing symbol belongs to the PyPy runtime interface. A runtime change or missing export could explain the failure.
Rust/PyO3 compatibility	Plausible	cryptography uses Rust, so its extension's interaction with PyPy's C API is another potential source of incompatibility.
Autobahn / Twisted	Very low	Neither appears to be the source of the native-extension loading error.

[p-r-a-v-i-n]

should we keep the pypy312 configuration in this PR but exclude it from required CI/release targets until upstream support is available, or defer pypy312 entirely and merge only CPython 3.15?

[oberstet]

my view: as good OSS citizens, we should track down this issue properly (is it cryptography or pypy?), and inform upstream, file an issue that reproduces the issue with minimal venv (without autobahn), and wait for upstream to fix.

until then, I don't want to introduce even more complexity into our CI just to have cpy315 and not pypy312. that's just my personal view and judgement, one might very well disagree!

but we're dealing with such stuff all the time:( call it unfortunate, call it business as usual, call it that's just how the world is;)

eg here is another example (unrelated to autobahn-python, but related to crossbar): crossbario/wamp-xbr#209

[p-r-a-v-i-n]

I respect what you said and I totally agree with you and actually this how i reached here for solving similar problem in other project.

we should track down this issue properly (is it cryptography or pypy?),

I reproduced this without Autobahn or Twisted using only PyPy 3.12 and cryptography 50.0.2. The cryptography extension builds with PyO3 0.29.2, but it references old PyPy symbols such as PyPy_DecRef and PyPyExc_ValueError.
PyPy 3.12 exports the new CPython-compatible symbol names instead, so this looks like a PyO3 compatibility issue.
I reported it to PyO3 here If they confirm it is a PyPy runtime issue, I will follow up with PyPy.

[p-r-a-v-i-n]

@oberstet Pyo3 closes that issue, what we should do now next ? I used AI for writing that Issue. Bcs reproducing that issue is not a brainy work, it a friction work and AI is useful to reduce this friction.

[oberstet]

@p-r-a-v-i-n here is my view:

• first, don't take it personal being brushed off wrt "wall of AI text" - it depends on the audience, for an expert / project owner, the full picture with text is additional unnecessary load to process, for a 3rd party developer it might very well be useful - but then, a "3rd party" developer, user of this, might not be interested to understand those details as well. so;)
• second, the note to first seek updated deps is very reasonable: you need to dig deeper;) two levels more. like below.

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tldr

• we need pyo3 0.29.3 - which has this fixed
• cryptography 50.0.2 (30 Sep 2026) is at pyo3 0.29.2. The 0.29.3 bump landed one day after this release. and 50.0.1 and 50.0.0 is at pyo3 0.29.0.
• cryptography head of master already has that
• => we need to wait for next release of cryptography, until 50.0.3 or 51 ships

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digging deeper, level 1

The fix is already released — it shipped in PyO3 0.29.3 (tagged 30 Sep 2026), not in 0.29.4. The maintainer's version number looks slightly off.

The commits that fix #6498:

• #6389, "ci: update ffi-check for PyPy symbol mangling change" by David Hewitt. On main it is 49a9e4e3. The 0.29.3 backport is 02832a30. This is the main fix. Its newsfragment says it fixes "many unresolved symbols when linking for PyPy due to incorrect link names in pyo3-ffi". It changes every #[cfg_attr(PyPy, link_name = "PyPy…")] to #[cfg_attr(all(PyPy, not(Py_3_12)), …)], so PyPy 3.12 links against the plain CPython names (Py_DecRef, PyExc_ValueError). That includes PyPy_DecRef.
• #6421, "check static addresses match in pyo3-ffi-check". On main it is cdd70b43, and the backport is e62a5eb3. It finishes the job for exported statics. PyExc_ValueError is exactly the symbol in your traceback, and its link name was switched here.
• Related 0.29.3 commits: #6374 (preliminary PyPy 3.12 fixes), #6410 (raw-dylib/PyPy link names), and #6422 (functions PyPy turned into macros). #6429, which adds the PyPy 3.12 DLL to the pyo3-ffi list, is on main only.

Here is the before and after for the symbol in your traceback:

v0.29.2: #[cfg_attr(PyPy, link_name = "PyPyExc_ValueError")]
v0.29.3: #[cfg_attr(all(PyPy, not(Py_3_12)), link_name = "PyPyExc_ValueError")]

There is a release-0.29.4 branch, but it adds only three commits on top of 0.29.3: a fix for a global-allocator stack overflow, plus two CI fixes. None of them touch PyPy.

What this means for autobahn-python: your build used cryptography 50.0.2, which pulled in pyo3 0.29.2 from its lockfile. The fix is to build cryptography against pyo3 ≥ 0.29.3. You can wait for a cryptography release that bumps it, or patch its Cargo.lock for a local source build.

Sources:

• [PyO3 issue #6498](PyPy 3.12/pp80 extension references legacy mangled PyPy symbols PyO3/pyo3#6498)
• [Commit 02832a30 (#6389 backport)](PyO3/pyo3@02832a3)
• [PyO3 PR #6389](ci: update ffi-check for PyPy symbol mangling change PyO3/pyo3#6389)
• [PyO3 PR #6421](check static addresses match in pyo3-ffi-check PyO3/pyo3#6421)

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digging deeper, level 2

I'll trace the pyo3 bump in cryptography's lockfile and check which tags contain it.

It isn't in any release yet. The bump is only on main.

• The bump commit is f93d90158, "chore(deps): bump pyo3 from 0.29.2 to 0.29.3 (#15736)". It was merged on 1 Oct 2026 and is a Dependabot PR that changes only Cargo.lock.
• Which tags contain it: none. git tag --contains f93d90158 comes back empty, and it is reachable only from origin/main.
• What each release locks:
  • 50.0.2 (30 Sep 2026): pyo3 0.29.2. The 0.29.3 bump landed one day after this release.
  • 50.0.1 and 50.0.0: pyo3 0.29.0.

One correction to "lower floor": Cargo.toml still just says pyo3 = { version = "0.29", ... }, so the floor wasn't raised. Only the lockfile pin changed. The lockfile still matters, because the sdist ships Cargo.lock and a from-source build uses it. That's why your build compiled 0.29.2.

Until cryptography 50.0.3 or 51 ships, you have two ways to build on PyPy 3.12:

• Build from a main checkout, which locks pyo3 0.29.3.
• Unpack the 50.0.2 sdist, run cargo update -p pyo3 --precise 0.29.3 (this also moves pyo3-ffi, pyo3-build-config and the macros), and build from that tree. This works because 0.29.3 satisfies ^0.29.

I checked release tags in the repo rather than PyPI directly, because PyPI blocked the fetch. cryptography tags every release, so 50.0.2 should be the latest.

Sources:

• [cryptography commit f93d90158 (#15736)](pyca/cryptography@f93d90158)
• [cryptography Cargo.lock at head](https://github.com/pyca/cryptography/blob/874145c30c2143546ce30c38eccd88f3bae3425c/Cargo.lock#L256)

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[p-r-a-v-i-n]

@oberstet

irst, don't take it personal being brushed off wrt "wall of AI text" - it depends on the audience, for an expert / project owner,

Thanks, I really like your attitude. Initially i thought this work is just changing the versions from previous references but it is more than that. I think I rushed in the process too much. I should have invest time in digging.

I will go through your suggestions slowly. thank you!