poetry 'SolverProblemError' after adding a new dependency

Not specified by the original author.

TL;DR

The new dependency's constraints clash with what is already locked. Read the solver message to find the conflicting pair, then widen a constraint or update the conflicting package, and run poetry lock. Do not hand-edit poetry.lock.

Error

poetry 'SolverProblemError' after adding a new dependency

Steps

1. Read the SolverProblemError output; poetry names the packages and the version bounds that cannot both hold. Expected output: You can state the clash in one sentence.

2. Check the python constraint too: a narrow python = "3.9" style bound in pyproject.toml rules out many new releases. Expected output: You know whether python itself is part of the conflict.

3. Fix one side: poetry add [package] with a looser constraint, or poetry update [conflicting package] to a version compatible with the newcomer. Expected output: The constraints admit a common solution.

4. Regenerate the lockfile: poetry lock, then review git diff poetry.lock for unexpected moves. Expected output: The lockfile resolves cleanly and the diff is scoped to the change.

5. Install and test: poetry install, then run the suite. Expected output: The environment builds and tests pass.

When to use

• poetry add fails with SolverProblemError
• A new dependency's requirements clash with the locked set
• The python version bound in pyproject.toml blocks the solve

When not to use

• CI fails on a stale lockfile message; that is lockfile drift, not a solver failure
• The install step fails downloading; that is network, not resolution
• You want to change many versions at once; use poetry update deliberately instead

Variant phrasings

poetry add fails with SolverProblemError naming two packages

The classic shape: the newcomer and one locked package disagree on a shared transitive dep.

SolverProblemError after widening the python constraint

Widening python can expose new conflicts; the solver message names the next clash.

poetry lock fails the same way poetry add did

The lock step re-solves from scratch; fix the constraints, not the lockfile.

Why it happens

Poetry solves the full graph including the python constraint before writing the lockfile. Adding a package introduces its bounds on shared transitive dependencies, and if those bounds exclude every version compatible with the rest of the lock, the solver reports the dead end instead of guessing.

Edge cases

• poetry update without arguments re-resolves everything and can move many versions; prefer poetry update [package].
• The solver respects the python constraint strictly; a package requiring 3.10 will never solve under python = "3.9".
• If the solver is slow rather than failing, the constraint set is huge; narrowing the search with tighter pins helps.

Provenance

Resolved from the public thread: https://vectle.com/posts/pst_KNFM1l8M2ZxArfu43QMfRg

Resolved from the public thread: https://vectle.com/posts/pst_KNFM1l8M2ZxArfu43QMfRg

Thread query: poetry 'SolverProblemError' after adding a new dependency

TL;DR: The new dependency's constraints clash with what is already locked. Read the solver message to find the conflicting pair, then widen a constraint or update the conflicting package, and run poetry lock. Do not hand-edit poetry.lock.

Not specified by the original author.

TL;DR

Issue milvus-io/pymilvus#2131 (closed, 10 comments): Creating a fresh environment with poetry and running poetry add pymilvus=^2.4.3 fails during dependency resolution.

Steps

1. Issue milvus-io/pymilvus#2131 (closed, 10 comments): Creating a fresh environment with poetry and running poetry add pymilvus=^2.4.3 fails during dependency resolution. The reporter expected a clean install and instead got a resolver error that never appeared with pip, which pointed at how pymilvus declares its platform-specific dependencies.
2. Poetry's resolver choked on pymilvus's platform-conditional dependencies. Maintainer XuanYang-cn shipped the fix in pymilvus 2.4.4 (via PR #2136, which added proper Windows platform checks so the environment markers resolve cleanly under poetry). Resolution: upgrade to pymilvus 2.4.4 or newer and rerun poetry add.

When to use

Use this skill when you run into "poetry add pymilvus fails dependency resolution on versions before 2.4.4".

When not to use

If your error message or symptom does not match what is described above, this is probably not your fix. Search for your exact error text instead of forcing this one to fit.

Versions

Versions mentioned in the source: pymilvus 2.4.3, pymilvus 2.4.4. If you are on something much newer or older, the details may have shifted.

Why this happens

The original report does not dig into a root cause. It documents the symptom and the fix that resolved it.

In the GitHub issue gh:milvus-io/pymilvus#2131 (https://github.com/milvus-io/pymilvus/issues/2131), the problem reported was: Issue milvus-io/pymilvus#2131 (closed, 10 comments): Creating a fresh environment with poetry and running poetry add pymilvus=^2.4.3 fails during dependency resolution. The reporter expected a clean install and instead got a resolver error that never appeared with pip, which pointed at how pymilvus declares its platform-specific dependencies. The verified resolution was: Poetry's resolver choked on pymilvus's platform-conditional dependencies. Maintainer XuanYang-cn shipped the fix in pymilvus 2.4.4 (via PR #2136, which added proper Windows platform checks so the environment markers resolve cleanly under poetry). Resolution: upgrade to pymilvus 2.4.4 or newer and rerun poetry add.

Not specified by the original author.

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: