v2.12.0.dev2

What's Changed

Added

• Added Dx, Dy, and Dz output support to PointCloudFieldMonitor, reconstructing D / epsilon_0 from raw E-field samples and diagonal Yee permittivity; sampled off-diagonal Yee permittivity emits a warning and uses diagonal components only.
• Added gds_precision to Geometry.to_gds_file(), Structure.to_gds_file(), and Simulation.to_gds_file() to control the coordinate precision written to GDS exports.
• Added merge_adjacent to Geometry.from_gds(); set merge_adjacent=True to merge fractured same-layer GDS polygons during import for roundtrip reconstruction.
• HeatSimulation and HeatChargeSimulation cloud runs now create a volume mesh before running the solver; use web.run(), run_async(), Job.run(), Job.step(), Batch.run(), or Batch.step() instead of separate upload/start/monitor calls for these simulations. Uniform Heat/HeatCharge batches advance the mesh and solver workflow automatically, with Batch.run() starting each solver step as soon as that simulation's mesh step completes. Batch.estimate_cost() reports the summed cost of the shared next workflow step for supported uniform batches; after estimating the mesh step, run it first before estimating the solver step. Batch.estimate_cost() raises for mixed or non-uniform multi-step batches; use Job.estimate_cost() per job in those cases. Cache-only batch results may record None in BatchData.task_ids because no server task ID exists. Mixed batches containing both regular simulations and Heat/HeatCharge simulations run those groups separately; split them into separate batches for maximum parallelism.
• Added thermionic Schottky contacts to the accelerated charge solver (DC and small-signal AC). Schottky physics is an opt-in on VoltageBC via model="schottky_mott"; the Mott rule phi_Bn = W - chi, phi_Bp = E_g - phi_Bn is built from per-medium material properties — work_function on the adjacent ChargeConductorMedium and electron_affinity / richardson_electron / richardson_hole on the adjacent SemiconductorMedium. Default model="ohmic" is the standard ohmic contact. Schottky contacts compose with SSACAnalysis / IsothermalSSACAnalysis, enabling Mott-Schottky 1/C^2 extraction on Schottky diodes.
• Native autograd support for FluxMonitor using hidden forward field storage in autograd runs. Set enable_adjoint=True on FluxMonitor objects whose .flux output is used in an autograd objective; this stores hidden surface field data for all requested flux-monitor frequencies.
• Added PalankovskiQuayApproxCarrierLifetime: doping- and temperature-dependent SRH lifetime in the Palankovski–Quay empirical Scharfetter form. Supported by the accelerated charge solver only.
• Added faster adjoint source construction for ModeMonitor, GaussianOverlapMonitor, AstigmaticGaussianOverlapMonitor, and DiffractionMonitor data with many active amplitudes.
• Improved polygon triangulation performance using Shapely constrained Delaunay triangulation.
• LayerRefinementSpec now refines axis-unaligned in-plane metal edges (in_plane_edge_refinement, default "mirror_corner") and resolves small disjoint metal geometries such as vias (min_steps_per_geometry, default 2), with a tunable CornerFinderSpec.axis_aligned_angle_threshold; both are on by default and give existing setups a finer mesh, set them to None to keep the previous mesh.
• ModeTimeMonitor records time-domain modal amplitudes at a waveguide
  cross-section, projecting the running Yee-grid fields onto the mode profiles
  solved at a single frequency (freq_spec, defaulting to the first source's
  central frequency).
• SolidMedium now accepts an optional velocity vector (in um/s; from_si_units takes m/s and converts), enabling a convective transport term in heat simulations for structures using that medium (both capacity and density are required when velocity is nonzero).
• FluxMonitor and FluxTimeMonitor now support staggered Yee-grid surface integration via use_colocated_integration=False, computed on the server with the same scheme as FieldMonitor(colocate=False, use_colocated_integration=False) flux, keeping tangential fields at their native Yee positions to avoid interpolation across material discontinuities.
• ThermalContactResistance boundary condition for heat simulations: an interfacial thermal resistance (thermal contact / Kapitza resistance, in K*um^2/W; from_si_units takes m^2*K/W) placed on a StructureStructureInterface or MediumMediumInterface allows a temperature jump proportional to the heat flux across the interface between two touching solids.
• Added tidy3d.web.refresh_licenses() and tidy3d configure --refresh-licenses to clear cached local license entitlements so the next local license check fetches current server state. Successful API key or API endpoint configuration updates now refresh local license state automatically. Rejected configuration updates do not refresh local license state; when combined with explicit refresh, the command or call reports that the cache was not refreshed. If automatic refresh fails after configuration is saved, tidy3d configure exits nonzero and web.configure(...) raises while leaving the saved configuration in place.
• Schottky contacts (VoltageBC with model="schottky_mott") now support Fermi-Dirac carrier statistics (fermi_dirac=True in the charge analysis spec), enabling Schottky devices with degenerately doped semiconductor regions in DC and small-signal AC analyses.
• Added PointCloudPermittivityMonitor for recording diagonal permittivity components for requested point clouds by sampling each component from its nearest native Ex / Ey / Ez Yee-grid location.
• MeshOverrideStructure accepts a min_steps_per_size field to set the grid size relative to the structure's bounding box (bounding box size divided by the requested number of steps, ignored on axes whose bounding box size is zero or infinite); when both dl and min_steps_per_size are set along a dimension, the finer grid size is used. dl is now optional (defaults to no override) so an override can be specified with min_steps_per_size alone.
• Added tidy3d.web.diagnose_connection() and the tidy3d diagnose-connection CLI for measuring Tidy3D API reachability and storage download throughput.
• Added penetrable to LossyMetalMedium: when True, the metal is solved as a regular conductive medium with subpixel averaging Simulation.subpixel.dielectric, instead of the lossy-metal-specific handling selected by Simulation.subpixel.lossy_metal.

Changed

• Changed the default cSi material-library variant from Green2008 to Palik_LowLoss. Accessing the cSi default medium implicitly now emits a migration warning. Callers that need pre-change results should request Green2008 explicitly, including in the 1.2 to 1.45 um overlap where both variants are valid. Palik_LowLoss is valid from 1.2 to 250 um. Green2008 covers pre-change results from 0.25 to 1.2 um, and Palik_Lossy is available from 0.1 to 1.4 um when the lossy Palik model is desired.
• Changed the cSi material-library Si_MultiPhysics optical model from Green2008 to Palik_LowLoss, aligning it with the new cSi default optical model.
• Updated tidy3d MCP startup for FastMCP 3.2.4 compatibility and documented exact remote MCP endpoint URLs for custom deployments.
• Mesh override structures with shadow=False now reuse a nearby existing grid line instead of always inserting a new one at their bounding box, so refined regions add fewer grid lines; affected setups may see slightly fewer or shifted grid lines around such overrides.
• Changed adjoint gradients to skip sources whose effective magnitude underflows solver precision and treat those contributions as zero.
• HeatChargeSimulation now raises a setup error when heat-solver features are requested in a non-isothermal charge analysis: solid-medium advection (SolidMedium.velocity) and resistive interfaces (ThermalContactResistance) are applied by the heat solver (including heat coupled with electrical conduction) but were previously ignored silently in non-isothermal charge (coupled charge+heat) runs. Heat, conduction+heat, and isothermal charge analyses are unaffected. ThermalContactResistance is now also listed in the heat boundary-conditions API reference.
• Path integrals with extrapolate_to_endpoints=False (the default for current integrals) now use a centered box-rule treatment at the endpoints instead of linear extrapolation, slightly changing coarse-mesh results for AxisAlignedCurrentIntegral, path_integrals_from_lumped_element, CustomImpedanceSpec.from_bounding_box (used by TerminalWavePort), lumped ports, and TerminalComponentModeler. Voltage integrals (default extrapolate_to_endpoints=True) are unchanged.
• Made Geometry.to_gds_file(), Structure.to_gds_file(), and Simulation.to_gds_file() raise SetupError when the requested precision is too fine for the exported coordinates or when exported coordinates are non-finite.
• EMEModeSpec.precision now defaults to "double"; set precision="auto" to resolve precision per EME cell -- double where that cell's mode solve contains a good conductor, single otherwise.
  EME monitor storage-size estimates now account for the double-precision (complex128) data EME writes (previously about 2x low); simulations near the storage limit may now report a larger size or exceed it.
• Heat and HeatCharge solver tasks are now billed based on their associated computational cost, like other solvers. For Heat and HeatCharge workflow jobs, Job.estimate_cost() and Batch.estimate_cost() now explicitly state when an estimate is for the mesh step only and that Job.step() or Batch.step() should be run before estimating the solver step. For variable-cost charge solves, estimates now show a typical FlexCredit cost separately from the maximum cost when the server provides one. The billed charge-solver cost depends on the solver iterations run to convergence; this is usually much smaller than the maximum allowed iterations, but hard-to-converge cases can reach the maximum cost.

Fixed

• Fixed ModeSimulation.epsilon() when config.simulation.use_local_subpixel enables local subpixel averaging.

• Fixed Simulation GDS exports so vacuum/background cutouts are preserved more reliably, including when exporting holes on the default layer and when mixing mapped and unmapped media in the same layout.

• Corrected the convergence_dv description in SteadyChargeDCAnalysis: the accelerated charge solver applies it only to multi-voltage sweeps (inserting intermediate warm-start bias points), while the from-zero bias ramp it previously described applies to the legacy solver.

  Validation now rejects providing more than one multi-voltage sweep array across VoltageBC sources of any type; previously a swept SSACVoltageSource alongside a swept DCVoltageSource was silently accepted with ambiguous sweep selection.

• Fixed EME coefficient normalization to use absolute real mode flux and leave zero-flux
  modes unscaled. All four interface S-matrix blocks are renormalized with the
  same absolute-real-flux rule, using flux data for both EME cells adjacent to
  each interface. Downsampled EMECoefficientMonitor data must use
  eme_cell_interval_space=1 when requesting normalized interface S matrices.
  Repeated-grid coefficient data must provide flux on the same virtual-cell
  eme_cell_index coordinates before normalizing A/B fields.

• Fixed FieldMonitor and FieldTimeMonitor flux over-counting under periodic and Bloch boundaries for monitors that span or exceed the simulation domain when using the experimental option use_colocated_integration=False; default and colocated monitors were not affected.

• Fixed nonzero diffraction-order adjoint plane waves to use single-frequency injection and avoid broadband grazing-angle artifacts.

• PolySlab now accepts polygons with arc segments (bulges) that enclose a finite area even when their vertices are collinear; previously such polygons were rejected with "The polygon almost collapses to a 1D curve."

• Fixed repeated autograd gradient evaluations so matching cached adjoint results are reused.

• Fixed component modeler FlexCredit cost estimates that could be lower than the real cost when the simulation run_time is a RunTimeSpec; the estimate now resolves the run time from the modeler's port excitation instead of the source-less base simulation.

• Fixed excessive memory retention during DesignSpace.run(fn_pre, fn_post) workflows that run batched simulations.

• A non-penetrable LossyMetalMedium is now rejected as a component of an AnisotropicMedium at construction time.

• Fixed structure_priority_mode being ignored when a WavePort is converted to a mode solver via to_mode_solver/to_mode_simulation.

Full Changelog: v2.12.0.dev1...v2.12.0.dev2