> ## Documentation Index > Fetch the complete documentation index at: https://docs.ionworks.com/llms.txt > Use this file to discover all available pages before exploring further. # 2026 06 22 ## GITTModel — a first-class diffusion-only model `GITTModel` and `HalfCellGITTModel` are now first-class models in `ionworkspipeline` (with matching `ionworks_schema` siblings). GITT fits overwhelmingly use the same lightweight model rather than SPMe: x-averaged particle diffusion per electrode, a single lumped ohmic resistance, fixed OCPs, and no Butler-Volmer kinetics, electrolyte dynamics, or thermal effects. Until now that model lived as near-identical local copies in per-engagement repos, which meant the API route could not run it. Shipping it as a built-in model unblocks server-side GITT fits and backs the new half-cell GITT fit template. ## Download ionworks-defined models for plain pybamm Users who have only `ionworks-schema` / `ionworks-api` — and not the licensed `ionworkspipeline` package — can now obtain ionworks-defined models (`ECM`, `LumpedSPMR`, the MSMR models, `GITTModel`) in a form they can load and run with plain `pybamm`. A new `POST /discovery/ionworks_models/serialize` endpoint builds the model server-side (where the license lives) and returns a loadable serialisation, exposed through the Python SDK. ## App-URL helpers for every routed resource The SDK's `client.urls` grew from a single `.measurement()` method to a full set of web-app link builders — `project`, `model`, `parameterized_model`, `optimization`, `pipeline`, `study`, `simulation`, `cell_specification`, `cell_instance`, and more — so callers never hand-construct `app.ionworks.com` URLs from IDs. The helpers are environment-aware, deriving the right host for whichever API environment the client is configured against. ## Stricter, clearer pipeline configuration Most user-driven errors in `ionworkspipeline` now raise `UserConfigurationError` (a `ValueError` subclass) instead of bare `ValueError` / `KeyError`, so configuration mistakes — wrong field types, out-of-range values, missing keys — are routed to a clear **Configuration error** for the user instead of paging on-call as an internal error. Alongside this, an in-progress schema-contract hardening effort began validating optimizer configs at the boundary: passing SciPy-only keys to a native optimizer (e.g. `DifferentialEvolution(popsize=5, maxiter=10)`) now hard-errors at submission time instead of being silently swallowed. **Improvements** * A single **calculation structure** — `dict[str, list[str] | None]` mapping each objective to the variables to compute — is now the source of truth for objective- and variable-level cost scoping, replacing the per-cost `objective_names` list. This lets a weighted `Wasserstein` (position-shifting dQ/dV) and a per-variable `SSE` share one `MultiCost` over an objective, with each cost explicitly scoped to the variables it should consume. `ElectrodeBalancing` gained a `dQdU model axis` option that emits dQ/dV on the model's own full-window voltage axis so a weighted Wasserstein can align peaks in voltage rather than on the data grid. * Strict optimizer-option validation: unknown `algorithm_options` keys (and method/options mismatches) are rejected at submission time, and `AskTellOptimizer` rejects unknown constructor kwargs at runtime with an actionable message — the previous behaviour silently ignored them. The typed option wrappers (`CMAESOptions`, `PSOOptions`, `DEOptions`, `XNESOptions`, `BayesianOptimizationOptions`, `SOBEROptions`, `TuRBOOptions`) remain the recommended way to pass options. * Failure sentinels across the cost and design spaces are unified into a single `FAILURE_PENALTY` constant, so the fitting and design-optimization paths can no longer drift apart and the penalty value is better-conditioned for surrogate-GP fits. **Fixes** * ECM coulomb-count capacity reference is now computed per segment. Multi-measurement fits previously accumulated the cumulative integral across concatenated segment boundaries, inflating the capacity estimate to roughly the sum of per-segment throughputs and triggering spurious capacity-sanity-check warnings. * A `geometry` passed through `simulation_kwargs` with symbolic bounds (e.g. a `pybamm.Scalar` min and a `pybamm.Parameter` max) is now deserialised back into pybamm objects before the simulation is built, instead of arriving as raw JSON and choking the solver. * `parse_model` now honours serialised `geometry`, `var_pts`, `spatial_methods`, and `submesh_types` for custom models, attaching them as per-instance defaults instead of letting pybamm rebuild geometry from `model.options`. **Improvements** * `client.model.download` / `serialize` (introduced above) return ionworks-defined models in a plain-pybamm-loadable form. * `client.urls` (introduced above) now builds links for every routed resource, environment-aware.