{"id":"c84b3fb746bca7a4","repo":"python-poetry/poetry","slug":"because-root-version-solving-failed","errorCode":null,"errorMessage":"Because {root}, version solving failed.","messagePattern":"Because (.+?), version solving failed\\.","errorType":"exception","errorClass":"SolverProblemError","httpStatus":null,"severity":"error","filePath":"src/poetry/puzzle/solver.py","lineNumber":186,"sourceCode":"            new_packages = self._solve()\n            override_packages.append((override, new_packages))\n\n        return merge_override_packages(\n            override_packages, self._package.python_constraint\n        )\n\n    def _solve(self) -> dict[Package, TransitivePackageInfo]:\n        if self._provider._overrides:\n            self._overrides.append(self._provider._overrides)\n\n        try:\n            result = resolve_version(self._package, self._provider)\n\n            packages = result.packages\n        except OverrideNeededError as e:\n            return self._solve_in_compatibility_mode(e.overrides)\n        except SolveFailureError as e:\n            raise SolverProblemError(e)\n\n        return self._aggregate_solved_packages(packages)\n\n    def _aggregate_solved_packages(\n        self, packages: list[Package]\n    ) -> dict[Package, TransitivePackageInfo]:\n        combined_nodes, markers = depth_first_search(\n            PackageNode(self._package, packages)\n        )\n        results = dict(aggregate_package_nodes(nodes) for nodes in combined_nodes)\n        calculate_markers(results, markers)\n\n        # Merging feature packages with base packages\n        solved_packages = {}\n        for package in packages:\n            if package.features:\n                for _package in packages:\n                    if (","sourceCodeStart":168,"sourceCodeEnd":204,"githubUrl":"https://github.com/python-poetry/poetry/blob/92b74dcfe348d0e01e14d40d6c1fa47a4ee04a54/src/poetry/puzzle/solver.py#L168-L204","documentation":"SolverProblemError is the top-level wrapper raised when the mixology version resolver cannot find any consistent assignment of package versions satisfying the full dependency graph (solver.py:185-186). It wraps a SolveFailureError and produces a root-cause message of the form 'Because {root}, version solving failed.' It signals that resolution is genuinely impossible under the current constraints, not a transient/network issue.","triggerScenarios":"Any call path into Solver.solve (poetry lock/install/update) where resolve_version raises SolveFailureError after exploring the full decision tree — e.g. the root project plus all transitive constraints have no joint solution, or python_version constraints exclude every candidate.","commonSituations":"python_version constraint too narrow for available releases; a dependency requires a package that was yanked/removed; conflicting pins across a large dependency tree that are not a simple pairwise conflict (so IncompatibleConstraintsError is not triggered first).","solutions":["Read the full solver failure chain Poetry prints (the 'Because X, Y requires Z...' trace) to locate the root conflict.","Check the root python constraint in [tool.poetry.dependencies] python and the requires_python of involved packages.","Loosen or remove tight pins and run `poetry update` to let the solver pick compatible versions.","If a package was yanked/removed, switch to a maintained fork or pin an older compatible release."],"exampleFix":"// before\n[tool.poetry.dependencies]\npython = \"^3.8\"\nsomelib = \"^3.0\"   # somelib 3.x requires python>=3.10\n// after\n[tool.poetry.dependencies]\npython = \"^3.10\"\nsomelib = \"^3.0\"","handlingStrategy":"try-catch","validationCode":null,"typeGuard":null,"tryCatchPattern":"from poetry.puzzle.exceptions import SolverProblemError\ntry:\n    solved = solver.solve()\nexcept SolverProblemError as e:\n    cause = e.error  # the underlying SolveFailureError\n    log.error(\"version solving failed: %s\", cause)\n    raise SystemExit(2) from e","preventionTips":["Keep the root python constraint wide enough to cover your deps' requires_python.","Pin only what you must; let the solver pick transitively.","Re-lock after upgrading major versions to detect unsatisfiable trees early.","Avoid mixing pre-release and stable pins for the same package."],"tags":["dependency-resolution","solver","unsatisfiable"],"analyzedSha":"92b74dcfe348d0e01e14d40d6c1fa47a4ee04a54","analyzedAt":"2026-08-04T20:33:34.072Z","schemaVersion":2}