Pyodide updates: pyemscripten platform tag (PEP 783), 314.0a1, `pyodide-eol` flag, and maintenance updates by agriyakhetarpal · Pull Request #2812 · pypa/cibuildwheel

agriyakhetarpal · 2026-04-06T13:52:04Z

As stated in the PR title. Through this PR:

We now use pyodide config get emscripten_dir to get the Emscripten installation location (and always with --force to ensure a fresh, unmodified toolchain on every run)
Since PEP 783 has been accepted, I have updated the wheel platform tag to pyemscripten_year_number for all supported versions – Pyodide 0.29.4 (the first release on the 0.29.x patch line with pyemscripten wheel support) introduces this for the 2025 ABI, and our new 314.0.0a1 prerelease (enabled under pyodide-prerelease) does so for the 2026 ABI
We now have a pyodide-eol enable group (analogous to pypy-eol`) to keep cp312/Pyodide 0.27.7 available behind an opt-in flag
I've introduced a short Pyodide maintainer guide encompassing the recurring tasks around Pyodide releases in cibuildwheel
Lastly, new dependency updates via the constraints updater split out from [Bot] Update dependencies #2810 and other recent bot PRs

This reverts commit 4bd785d.

henryiii · 2026-04-07T06:05:02Z

It has been accepted. :D

agriyakhetarpal · 2026-04-07T06:28:59Z

One question: should we rename Pyodide to Pyemscripten in most other places as well?

hoodmane · 2026-04-07T16:57:46Z

We should keep calling it Pyodide, nobody knows what pyemscripten is.

henryiii · 2026-04-07T17:09:40Z

If we wanted to match everything else, then the platform would be emscripten (like linux), the identifier would be pyemscripten (like manylinux) or maybe even pyodide. I don't think it's important enough to change now, though now would be the time to do it when this is about to make a fairly big change to the wheel name.

ryanking13

One question: should we rename Pyodide to Pyemscripten in most other places as well?

+1 for keeping it as Pyodide.

agriyakhetarpal · 2026-04-07T18:52:05Z

Alright, I think Pyodide stays as the name, then. We can always create an alias and add both Pyodide and pyemscripten at a time when the latter gains popularity.

hoodmane · 2026-04-08T14:03:05Z

            platform_tags = {
-                "cp312-cp312": ["pyodide_2024_0_wasm32"],
-                "cp313-cp313": ["pyodide_2025_0_wasm32"],
+                "cp312-cp312": ["pyemscripten_2024_0_wasm32"],


The existing tags should stay the same right? There is no version of Pyodide that accepts a wheel tagged pyemscripten_2024_0 so if we're going to make them we might as well just delete support for versions older than 314. But it'd be better not to change the existing behavior.

I believe this is a regression, then. @ryanking13, were we too early in changing to the pyemscripten platform tag in pyodide-build? Ideally the previous xbuildenvs (0.27.7, 0.29.3, etc.) should have set USE_LEGACY_PLATFORM, but then that's not possible to fix retroactively as we didn't know that at the time. So maybe we should yank pyodide-build==0.34.1, set USE_LEGACY_PLATFORM to 1 and create a new release with it (0.35.0 because semver), and then ensure that the upcoming 314.0 xbuildenv(s) will set USE_LEGACY_PLATFORM to 0 in Makefile.envs. I would like to support both 0.29.3 and 314.0 releases at the same time, to allow users extra time to switch ABIs.

Well, I am not sure to be honest. If we keep the pyodide tag, then the package will not be uploadable to PyPI, if we change it to pyemscripten, old versions of micropip will deny the package. So both choices have downsides.

I am personally +1 for using the pyemscripten name for even older versions for consistency. Older Pyodide versions can still either 1) install newer micropip from PyPI, or 2) install it directly through pyodide.loadPackage. I think it is less confusing than outputting different platform names for differenet Python versions.

Hmm, given that users do have an option to update micropip, and now that the first alpha of 314.0 is out (thanks to you!), I will add it in this PR and drop Pyodide 0.27.7.

Will that resolve your concerns, @hoodmane? Or, do you think that cibuildwheel should work around it now, and rename 2024_0 and 2025_0 ABI wheels that contain pyemscripten in the platform tag string back to pyodide for them?. We do have some time until this PR is merged and released, and it brings pyodide-build 0.34.1, so it's better that we do things right in the first go.

If a patch release of pyodide 3.13 with updated micropip was possible, then I'd go:

drop 3.12

switch 3.13 to pyemscripten_2025

keep 3.14 as "pre-release" until pyemscripten_2026 is declared stable.

If a patch release is hard to do... Well, that's uglier. Are these "normal" enough that wheel tag can re-tag?

There is now a v0.29.4 patch release: https://github.com/pyodide/pyodide/releases/tag/0.29.4. Updating to it!

agriyakhetarpal · 2026-05-07T13:08:40Z

Ready for one more look!

joerick

I think we might be missing docs on the new enable option in docs/options.md.

also, I think it might be time for pyodide to lose its 'experimental' status in cibuildwheel? I noticed a note in docs/platforms.md.

The rest looked good to me, although I only skim-read it!

joerick · 2026-05-08T08:12:06Z

Oh, the other place to remove the experimental language would be the table at the top of the readme

agriyakhetarpal · 2026-05-08T12:23:46Z

Good points @joerick, I've made those changes! Thank you!

agriyakhetarpal · 2026-05-08T12:25:49Z

A bit of a note: since we do have pyodide-version/CIBW_PYODIDE_VERSION and it still works for any generalised Pyodide version case, people will be able to build for Pyodide beyond EOL if they would like to, so we'd consider pyodide-eol as more of a helper to do so.

ryanking13

Thanks for working on this @agriyakhetarpal! It looks good to me overall. As you mentioned, probably we need a new alpha, but I think this PR can land without it.

ryanking13 · 2026-05-09T07:13:27Z

@@ -0,0 +1,113 @@
+# Maintaining Pyodide support


Thanks for writing this!

ryanking13 · 2026-05-09T07:14:41Z

+        # compatible version here. delocate is macOS-only and not used on pyodide.
+        tool_versions = {
+            "pip": "23.1.2",
+            "build": "1.4.2",


what happens if we use build 1.4 or 1.5 for all cases?

It now supports 1.4 and 1.5, but it's highly constrained due to worries about it using build's internals. Those are generally okay, I think. I think the reason for 1.2.2 was likely older Python support, but we are dropping 3.9 so hopefully that's better now.

henryiii

Probably needs a followup removing pyodide 3.12.

henryiii · 2026-05-09T16:12:55Z

@copilot resolve the merge conflicts in this pull request

(Edit: GitHub offered this as an option, but I don't think it works on cross-org pull requests)

EditEdit: Used Kimi-K2.6 locally.

agriyakhetarpal added 8 commits April 6, 2026 18:41

Use pyodide config get emscripten_dir

87bcefe

Update constraints

17679b8

Updates for pyemscripten platform tag

2df97d1

Weird constraints stuff...

4bd785d

Revert "Weird constraints stuff..."

499e965

This reverts commit 4bd785d.

Add some special constraints for pyodide

8064a46

Wheel pyemscripten collision

ac56575

Put delocate back in constraints (not needed tho)

52fa455

agriyakhetarpal mentioned this pull request Apr 6, 2026

[Bot] Update dependencies #2810

Merged

agriyakhetarpal changed the title ~~WIP Pyodide updates~~ Pyodide updates: remove hardcoded Emscripten location, pyemscripten platform tag (PEP 783), and update dependencies Apr 6, 2026

agriyakhetarpal marked this pull request as ready for review April 6, 2026 15:39

agriyakhetarpal requested review from hoodmane and ryanking13 as code owners April 6, 2026 15:39

agriyakhetarpal requested review from henryiii and joerick April 6, 2026 15:39

agriyakhetarpal changed the title ~~Pyodide updates: remove hardcoded Emscripten location, pyemscripten platform tag (PEP 783), and update dependencies~~ Pyodide updates: remove hardcoded Emscripten location, switch to pyemscripten platform tag (PEP 783), and update dependencies Apr 6, 2026

henryiii approved these changes Apr 7, 2026

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ryanking13 approved these changes Apr 7, 2026

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Comment thread cibuildwheel/platforms/pyodide.py

Comment thread cibuildwheel/platforms/pyodide.py

hoodmane reviewed Apr 8, 2026

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agriyakhetarpal added 5 commits April 10, 2026 19:15

Drop Pyodide 0.27.7 (cp312-pyodide_wasm32)

46a2627

Add Pyodide 314.0.0a1 (cp314-pyodide_wasm32)

088d6e5

Delete no-longer-needed Pyodide 312 constraints

455e568

Update Pyodide 313 and 314 constraints

9396cae

Add back prerelease stuff and update tests

f0289d8

This was referenced May 5, 2026

pyemscripten/pyodide wheel builds pyca/pynacl#946

Open

Add support for pyemscripten/pyodide wheel builds pydantic/pydantic#13156

Open

Add support for pyemscripten/pyodide wheel builds pydantic/pydantic#13157

Open

agriyakhetarpal added 7 commits May 7, 2026 17:26

Merge main

18ea0fc

Add "Last updated: May 2026" to Pyodide document

e50d138

Add a Pyodide EOL filter

829392f

Fix typo

0a4abb6

Update maintenance docs about EoL Pyodide

1960c6e

Add Pyodide 312 constraints back

44bdfbc

Update Pyodide 313 and 314 constraints

f4255af

agriyakhetarpal changed the title ~~Pyodide updates: pyemscripten platform tag (PEP 783), 314.0 alpha1, pyodide-eol flag, and maintenance updates~~ Pyodide updates: pyemscripten platform tag (PEP 783), 314.0a1, pyodide-eol flag, and maintenance updates May 7, 2026

agriyakhetarpal requested review from henryiii, hoodmane, joerick and ryanking13 May 7, 2026 13:08

joerick reviewed May 8, 2026

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agriyakhetarpal added 3 commits May 8, 2026 17:48

Remove "experimental" note about Pyodide

8fc1e7c

Remove another experimental Pyodide sentence

ff16b28

Add docs about the pyodide-eol enable option

d408f03

agriyakhetarpal requested a review from joerick May 8, 2026 13:25

agriyakhetarpal added the type: enhancement label May 8, 2026

ryanking13 approved these changes May 9, 2026

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henryiii approved these changes May 9, 2026

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Merge upstream/main into pyodide-updates

11490ff

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