What does pip:INSTALLED_PACKAGES_CONFLICT mean?

Your environment is already inconsistent. pip installed or upgraded something, but the full installed set now contains version conflicts.

ERROR: pip's dependency resolver does not currently take into account all the packages that are installed.

Q: How do I prevent pip:INSTALLED_PACKAGES_CONFLICT in CI?

Use a fresh venv for projects and avoid long-lived global Python environments. Use pinned requirements/constraints and update them intentionally. In CI, always build from scratch (or from a clean cache) to avoid hidden drift.

Q: How can I manually validate pip:INSTALLED_PACKAGES_CONFLICT?

Run `python -m pip check` to list all detected conflicts. Run `python -m pip list` and capture the exact versions in the environment. Identify which command introduced the conflict (the last install/upgrade).

Fix it fast

Most likely: The environment already contains packages with incompatible versions. pip completed the requested install, but the full installed set is now inconsistent.

1. Confirm this is your error

ERROR: pip's dependency resolver does not currently take into account all the packages that are installed. This behaviour is the source of the following dependency conflicts.

2. Check the cause

python -m pip check
python -m pip list
python -m pip --version

3. Apply the safe fix

# Fastest clean fix for a project: rebuild the venv from requirements or a lock file.
python3 -m venv .venv
. .venv/bin/activate
python -m pip install --upgrade pip
python -m pip install -r requirements.txt

# If repairing in place, change the conflicting pins, then reinstall the full requirement set.
python -m pip install -r requirements.txt

4. Verify it works

python -m pip check
python -m pip list

Don't use unsafe shortcuts

Do not treat this as a successful install just because the command exited after printing conflicts.
Do not repair a heavily drifted environment one package at a time if a fresh venv is available.
Do not mix OS package manager installs and pip installs in the same project environment.

What Broke in the Dependency Graph

This is pip refusing to continue with a dependency graph that does not make sense. The important detail is which versions or peer requirements disagree, not just the final error code.

Repair the dependency graph

In a project venv, the fastest fix is often to rebuild the environment and reinstall from requirements/lock files.

If you must repair in place, adjust pins so the dependency ranges overlap, then reinstall with python -m pip install -r requirements.txt.

Avoid mixing installers/managers for the same environment, pick one approach per env.

Why Resolution Broke

Usually this comes down to you upgraded one package without upgrading/downgrading its dependencies to compatible versions, multiple tools are managing the same environment (OS packages, pip, other env managers), or a constraints file or pin forced an incompatible version.

Prove the Graph Is Clean Again

Run python -m pip check and confirm it reports no conflicts, and run your application/test suite to confirm runtime compatibility.

Manual environment health checks

Run python -m pip check to list all detected conflicts.

Run python -m pip list and capture the exact versions in the environment.

Identify which command introduced the conflict (the last install/upgrade).

Why pip can leave an environment inconsistent

pip resolves dependencies for the operation you requested, but the environment may already contain packages that conflict with the new requirements. pip warns that the resolver doesn't fully reconcile every already-installed package in all scenarios, and it prints the conflicts it detected.

Keep the Dependency Graph Healthy

To prevent this, use a fresh venv for projects and avoid long-lived global Python environments, use pinned requirements/constraints and update them intentionally, and in CI, always build from scratch (or from a clean cache) to avoid hidden drift.

Docs and source code

github.com/pypa/pip/blob/25.3/src/pip/_internal/commands/install.py

pip prints this warning when the resolver detects conflicts with already-installed packages. - GitHub

parts: list[str] = []
if resolver_variant == "legacy":
    parts.append(
        "pip's legacy dependency resolver does not consider dependency "
        "conflicts when selecting packages. This behaviour is the "
        "source of the following dependency conflicts."
    )
else:
    assert resolver_variant == "resolvelib"
    parts.append(
        "pip's dependency resolver does not currently take into account "
        "all the packages that are installed. This behaviour is the "
        "source of the following dependency conflicts."
    )