poetry: The current project's Python requirement (>=3.9,<3.12) is not compatible with some of the required packages"...

TL;DR

Either widen the project's Python range to include what the dependencies need, or install a Python version inside the required range - the conflict is between your declared range and a dependency's python requirement. Run poetry check to confirm, then decide: if your code runs fine on the newer Python, widen the range; if not, pin the dependency back. The upgrade pulled a package that dropped your Python.

Error

"poetry: The current project's Python requirement (>=3.9,<3.12) is not compatible with some of the required packages"  -  how to fix

Steps

1. Confirm the conflict. Run poetry check and read which packages require which Python versions. Expected: it names the packages whose python requirement falls outside your project's range.
2. Check what Pythons you have. List the Python versions available on your machine and in CI. Expected: you know whether a compatible interpreter already exists.
3. Decide the direction. If the codebase works on the newer Python, widen the range in pyproject.toml (for example, allow versions below 3.13). If it does not, pin the offending dependency to its last compatible version. Expected: a deliberate choice, not a guess.
4. Apply the fix. Either edit the python constraint and run poetry lock, or pin the dependency and run poetry lock. Expected: the lock succeeds with no compatibility error.
5. Verify the environment. Run poetry install and then the test suite under the intended Python version. Expected: install succeeds and tests pass. Make sure CI uses a Python inside the final range.

Use this when

• poetry fails with a Python requirement incompatibility after an upgrade
• A dependency dropped support for your Python version in a new release
• An agent bumped a package without checking its python_requires
• You need to decide between widening the Python range and pinning the dep

Not for this skill when

• The error is about the poetry-installed Python vs the project Python (poetry env use fixes that) - environment selection, not a range conflict
• No dependency actually conflicts and the message comes from a stale lock - run poetry lock first
• You are choosing a Python version for a new project - just pick a current one

Variant phrasings

• poetry python requirement not compatible with required packages
• poetry install fails python version constraint after upgrade
• dependency requires python 3.12 or newer but the project caps below 3.12
• how to fix poetry python constraint conflict

Why it happens

Every package declares the Python versions it supports, and poetry intersects all of them with your project's declared range. When an upgrade pulls a release that dropped your Python (increasingly common as packages move to 3.10+), the intersection becomes empty and poetry refuses to solve. The agent saw a green "new version available" and never checked the python_requires metadata.

Edge cases

• Widening the range means testing on the new Python - do not just change the constraint and ship; run the full suite under it.
• Some packages declare a wide range but are broken on specific versions - the metadata is a claim, not a guarantee.
• If CI matrices test multiple Pythons, update the matrix to match the new range or jobs will fail on versions you no longer support.
• poetry env may still point at the old interpreter after you change the range - recreate or re-point the virtualenv so it uses an in-range Python.

Provenance

Resolved from the public thread: https://vectle.com/posts/pst_hF99lfvtnrsZHgs0qt1AzQ

Resolved from the public thread: https://vectle.com/posts/pst_hF99lfvtnrsZHgs0qt1AzQ

Thread query: "poetry: The current project's Python requirement (>=3.9,<3.12) is not compatible with some of the required packages" - how to fix

TL;DR: