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May 11, 2026
Custom PyBaMM model + Li-S support, ECM capacity co-optimization, default project for the Python SDK, structured validation issues

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Custom PyBaMM models with Lithium-Sulfur chemistry

The /models/upload-custom endpoint now accepts a chemistry field (defaulting to lithium_ion), and Li-S models get more accurate and robust initialization when they run. The manage-projects SDK skill documents the full upload workflow — pybamm.Serialise().save_custom_model(filename=...) → multipart upload → client.model.get(id) returns is_custom_model: true.

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ECM fit: capacity co-optimization and per-segment initial SoC

Several interlocking improvements to the project-scoped ECM fit. Supplying an ocv_soc_curve (and optional bounds_capacity) lets you co-optimize cell capacity Q jointly with the fit instead of pinning Q to a single seed; on a 25 °C rate-test trace the fitted capacity now lands within 0.9 % of the coulomb-counting truth across all knot schedules. initial_soc accepts a list (one entry per measurement) so multi-measurement fits reset SoC at each segment boundary instead of integrating coulombs across the gaps; if you omit it, an improved auto-seed routine now estimates each segment’s starting SoC automatically. num_knots, num_knots_r0, knot_schedule, and clamp_max_ratio are now first-class parameters on /fit-from-measurements and /fit-from-file. A boundary-clamp default was also loosened, fixing an issue where it could collapse the R0 fit and cause solver failures on rate-test forward simulations.

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Default project for the Python SDK

The Ionworks client now resolves a default project_id at construction time from a project_id= argument or the new IONWORKS_PROJECT_ID environment variable, so callers no longer have to thread project_id through every call. The previous PROJECT_ID env var still works but emits a DeprecationWarning. All client.study.* methods take project_id as an optional keyword (after the resource ID) defaulting to the client value, and pipelines and optimizations auto-inject it into payloads.

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Structured measurement-validation issues

MeasurementValidationError.errors is now list[ValidationIssue] — a frozen dataclass carrying a stable IssueCode (StrEnum), severity, human-readable message, and JSON-native payload. Downstream code can branch on check identity via e.has_code(IssueCode.CURRENT_SIGN_REVERSED) instead of grepping the message string. ionworksdata’s auto-fix path now keys off the new codes; IssueCode and ValidationIssue are re-exported from the top-level ionworks package.
Improvements
  • Simulation boards now have a dedicated backend API at /projects/{project_id}/studies/{study_id}/simulation_boards, fixing a blank Visualization tab in some cases.
  • Optimization Performance Detail and Performance Summary tabs now surface buried validation_warning / validation_not_supported issues as top-level alerts above the tabs, with info “no data” alerts inside the tabs for the rare empty-but-valid case.
  • Defensive UX in the Visualization tab: the Data/Visualization toggle stays visible even when no board is available, with a warning alert prompting the switch back to Data instead of trapping the user on a blank page.
Fixes
  • The single simulation result page no longer flashes “Simulation not found” before the data loads on a fresh navigation.
Improvements
  • ionworks-schema gained Constraint, Penalty, CMAESOptions, PSOOptions, DEOptions, LatinHypercube, and Uniform schema classes, plus improved documentation across objectives, data fits, parameter estimators, regularizers, and distribution samplers.
Fixes
  • Fixed an issue where a solver failure on a bad parameter combination during a fit could crash the whole datafit instead of being handled gracefully. Cloud fits stay alive and the offending sample just gets a huge cost.
Improvements
  • New client.urls.measurement(measurement_id, project_id) helper returns the web app deep link for a measurement, so callers don’t have to hand-build URLs themselves.
Improvements
  • manage-projects documents the /models/upload-custom multipart workflow and the Model / ParameterizedModel disambiguation.
  • upload-data and other validation-aware skills updated to reference the new IssueCode / ValidationIssue API and the e.has_code(...) pattern instead of substring-matching error strings.