Poetry does not install greenlet for sqlalchemy[asyncio] on Apple Silicon

[mallhok]

Note

I've used AI to organize and format everything properly in the text below, but this is a real issue I've encountered.
You can skip to the Minimal Reproduction section below.

I'm trying to determine whether this is a Poetry bug or whether I'm misunderstanding how dependency markers and extras are evaluated.

Environment

• Poetry: 2.3.2
• Python (Poetry executable): 3.10.11 (this is globally installed on my machine and is often used by default)
• Project Python: 3.12.13 (need to specify using poetry env use)
• Platform: macOS 26.5.2
• Architecture: Apple Silicon (arm64)

$ poetry debug info

Poetry
Version:    2.3.2
Python:     3.10.11

Virtualenv
Python:     3.12.13

Base
Platform:   darwin
Python:     3.12.13

---

Original issue

In a larger project, my dependency is:

[project]
dependencies = [
    "sqlalchemy[asyncio]>=2.0.45,<3.0.0",
]

Running the application resulted in:

<venv>/lib/python3.12/site-packages/sqlalchemy/util/concurrency.py", line 81, in _not_implemented
    raise ValueError(
ValueError: the greenlet library is required to use this function. No module named 'greenlet'

Checking the environment showed that greenlet was not installed:

$ poetry run pip show greenlet
WARNING: Package(s) not found: greenlet

Adding an explicit dependency on greenlet to pyproject.toml fixed the issue.

---

Initial investigation

I noticed SQLAlchemy publishes this dependency metadata:

greenlet>=1;
platform_machine == "aarch64"
or platform_machine == "ppc64le"
or platform_machine == "x86_64"
or platform_machine == "amd64"
or platform_machine == "AMD64"
or platform_machine == "win32"
or platform_machine == "WIN32"

greenlet>=1; extra == "asyncio"

On my machine:

$ python3 -c "import platform; print(platform.machine())"
arm64

So initially I suspected the missing arm64 platform marker.

---

Minimal reproduction

To isolate the issue, I created a fresh project.

pyproject.toml:

[project]
name = "poetry-greenlet-repro"
version = "0.1.0"
requires-python = ">=3.12"

dependencies = [
    "sqlalchemy[asyncio]>=2.0.51,<3",
]

[tool.poetry]
package-mode = false

[build-system]
requires = ["poetry-core>=2.0.0,<3"]
build-backend = "poetry.core.masonry.api"

Then:

poetry env use python3.12
poetry lock
poetry install

The install output is:

Installing dependencies from lock file

Package operations: 2 installs, 0 updates, 0 removals

- Installing sqlalchemy (2.0.51)
- Installing typing-extensions (4.16.0)

Notice that greenlet is not installed.

---

Verifying the environment

greenlet is not installed:

$ poetry run pip show greenlet
WARNING: Package(s) not found: greenlet

$ poetry run python -c "import greenlet"
ModuleNotFoundError: No module named 'greenlet'

---

However, Poetry still resolves greenlet

$ poetry debug resolve

Resolution results:

greenlet          3.5.4
typing-extensions 4.16.0
sqlalchemy        2.0.51

---

Poetry also reports greenlet as a dependency

$ poetry show sqlalchemy

name         : sqlalchemy
version      : 2.0.51

dependencies
 - greenlet >=1
 - typing-extensions >=4.6.0

Dependency tree:

$ poetry show sqlalchemy --tree

sqlalchemy 2.0.51
├── greenlet >=1
└── typing-extensions >=4.6.0

Or:

$ poetry show --tree --why greenlet

sqlalchemy
└── greenlet >=1

---

Installed SQLAlchemy metadata

The metadata inside the installed wheel contains:

$ poetry run python - <<'PY'
from importlib.metadata import metadata

for req in metadata("SQLAlchemy").get_all("Requires-Dist"):
    if "greenlet" in req:
        print(req)
PY

Output:

greenlet>=1; platform_machine == "aarch64" or (platform_machine == "ppc64le" or (platform_machine == "x86_64" or (platform_machine == "amd64" or (platform_machine == "AMD64" or (platform_machine == "win32" or platform_machine == "WIN32")))))

greenlet>=1; extra == "asyncio"

---

Verbose install

Running

poetry install -vvv

does not mention greenlet at all.

Searching the verbose output:

poetry install -vvv 2>&1 | grep -i greenlet

only prints

Using virtualenv ...

There is no indication that Poetry considered, installed, or skipped greenlet.

---

Platform information

The project is definitely running on Apple Silicon:

$ poetry run python -c "import platform; print(platform.machine())"

arm64

poetry debug tags also reports ARM64-compatible wheel tags.

---

Why I'm confused

These observations seem contradictory:

• greenlet appears in the resolved dependency graph (poetry debug resolve)
• greenlet is listed as a dependency of SQLAlchemy (poetry show sqlalchemy)
• SQLAlchemy's installed metadata contains the greenlet dependency
• Yet poetry install never installs it

---

Related issue

While investigating, I found this SQLAlchemy issue:

sqlalchemy/sqlalchemy#7714

A maintainer commented that this appeared to be a Poetry issue involving dependencies listed in extras with different markers.

That seems similar to what I'm seeing, although I'm not sure if it's the same underlying problem.

---

Questions

1. Is this expected behavior?
2. Why does poetry debug resolve resolve greenlet, and poetry show sqlalchemy list it as a dependency, while poetry install does not install it?
3. Is this related to the combination of:
   • platform-specific markers (platform_machine == "aarch64")
   • extra == "asyncio"
   • Apple Silicon reporting platform.machine() == "arm64"?
4. If this is a bug, is this the correct minimal reproducer?

[dosubot[bot]]

Hi @mallhok! I'm Dosu and I'm helping the Python Poetry team.

This is a confirmed bug, not a misunderstanding on your part. It was recently reported in #10910 with the exact same scenario — sqlalchemy[asyncio] on Mac Darwin arm64 failing to install greenlet [1].

Root cause: When SQLAlchemy declares greenlet with two separate conditions — a platform marker (platform_machine == "aarch64" or ...) and an extras marker (extra == "asyncio") — Poetry's marker exclusion logic in poetry-core incorrectly handles the union of these markers. When it strips the extra == "asyncio" marker during lock file generation, instead of collapsing the result to "always install," it keeps only the platform marker. Since arm64 isn't in the platform list, greenlet gets a marker in the lock file that evaluates to false on your machine [2] [1].

Why poetry debug resolve still shows it: The resolver correctly identifies greenlet as needed, but the marker written into the lock file filters it out at install time [1].

The fix has been merged in poetry-core#943, which corrects BaseMarker.exclude() to return AnyMarker() when a matching marker name is found inside a union, rather than dropping it and rebuilding the union with only the remaining (platform) markers [2].

What you can do now: Until a Poetry release ships with the updated poetry-core, adding greenlet as an explicit dependency (as you've already done) is the correct workaround.

To reply, just mention @dosu.

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