pip resolver_error ai_generated true

INFO: pip is looking at multiple versions of <package> to determine which version is compatible with other requirements. This could take a while.

ID: pip/backtracking-long

Also available as: JSON · Markdown
82%Fix Rate
85%Confidence
50Evidence
2022-06-01First Seen

Version Compatibility

VersionStatusIntroducedDeprecatedNotes
24 active — — —

Root Cause

Pip's dependency resolver is backtracking through many version combinations to find a compatible set. Can take hours or appear to hang. Usually caused by loose version constraints, packages with many releases, or genuinely conflicting requirements.

generic

Workarounds

  1. 88% success Pin specific versions to reduce the search space: package==X.Y.Z 
    Add explicit version pins for the packages pip is backtracking on, based on known-good combinations
  2. 85% success Use pip-compile (pip-tools) to pre-resolve dependencies offline 
    pip install pip-tools && pip-compile requirements.in -o requirements.txt && pip install -r requirements.txt
  3. 83% success Use constraints file to limit version search space 
    Create constraints.txt with known-good versions, then: pip install -c constraints.txt -r requirements.txt

Dead Ends

Common approaches that don't work:

  1. Wait indefinitely for the resolver to finish 60% fail

    Backtracking can be combinatorial; some dependency sets never resolve and pip will run for hours or days

  2. Use --use-deprecated=legacy-resolver 70% fail

    Legacy resolver was removed in pip 24; even when available it silently installs incompatible versions

Error Chain

Leads to:
Preceded by:
Frequently confused with: