Breaking changes Reverted the "voltage as a state" default back to "false", undoing the v26.7.0.0 change to "true". Promoting voltage to an algebraic state turns SPM/SPMe into DAEs and places voltage under solver error control, which caused IDAKLU error-test failures on solves of discontinuous (pulsed) current profiles at the default tolerances, and lowered voltage-output accuracy. The option remains available ({"voltage as a state": "true"}) and is still enabled automatically for the "explicit power" and "explicit resistance" operating modes. (#5670) Features Exposed the per-value parameter serialisation dispatch publicly as pybamm.serialize_parameter_value/pybamm.deserialize_parameter_value, and convert_parameter_values_to_json now accepts any Mapping (not just a ParameterValues), so a raw {name: value} mapping can be serialised without constructing a throwaway ParameterValues. (#5663)