[Newton] Avoid repeated model startup work (#7295)

## Summary

This is the model/articulation part of the scoped Newton startup work.
It keeps startup work with the component that owns it:

- each Newton manager declares only the custom builder schema used by
its active solver;
- articulation target modes are resolved for the prototype and copied to
its replicas;
- the base physics manager owns the articulation-view registry;
- articulations create and register their view, while joint-wrench
sensors reuse it or create it when used independently;
- root expressions remain regular expressions instead of taking a lossy
regex-to-glob round trip.

The active-solver and reusable-view findings originated in Chris's
#7269. This PR isolates those model/articulation changes so #7269 can
remain the contact/raycast change under Chris's PR.

This replaces the cloner's unconditional MuJoCo + Kamino registration
and the duplicate joint-wrench view. There is no view scan,
manager-specific cache API, compatibility fallback, or duplicate
registry.

The production diff against the current base is `+57/-60` (net `-3`).

The explicit-global-ownership part is #7292. The contact/raycast part
remains in #7269.

## Startup benchmark

RTX 5090, CUDA device 1, 4096 environments, three fresh processes per
revision/task. Values are median end-to-end startup wall time; raw runs
are included below. Base: `86cf66651bd`. PR: `947869af173`.

| Task | Base | PR | Change |
|---|---:|---:|---:|
| `Isaac-Cartpole` | 8.316 s | 7.655 s | -8.0% |
| `Isaac-Velocity-Rough-UnitreeGo2` | 17.525 s | 14.844 s | -15.3% |
| `Isaac-Lift-KukaAllegro-Camera` | 41.691 s | 36.832 s | -11.7% |

Raw totals:

- Cartpole base: 10.595, 8.190, 8.316 s; PR: 7.655, 7.674, 7.469 s.
- Go2 rough base: 17.568, 17.525, 16.426 s; PR: 14.852, 14.844, 14.724
s.
- Kuka camera base: 47.590, 41.691, 38.724 s; PR: 36.832, 36.666, 37.032
s.

The measured `env_creation` medians improve from 6.473 to 5.801 s for
Cartpole, 15.558 to 12.863 s for Go2 rough, and 37.481 to 32.578 s for
Kuka camera.

## Test plan

- `247 passed` across the physics-manager lifecycle, Newton cloner,
manager abstraction, coupled-manager, and joint-wrench reuse tests.
- `test_rename_builder_labels.py`: `17 passed` after removing obsolete
solver-registration mocks.
- Ruff check and format pass on all changed Python files.
- The three 4096-environment benchmark tasks provide end-to-end Newton
MJWarp startup coverage.

(cherry picked from commit c4a2759)

Author: ooctipus

source/isaaclab/changelog.d/ooctipus-newton-active-solver-attributes.skip

@@ -86,6 +86,7 @@ class PhysicsManager(ABC):
     _sim_time: ClassVar[float] = 0.0
     _callbacks: ClassVar[dict[int, tuple[Any, Callable, int, str | None, Any]]] = {}
     _callback_id: ClassVar[int] = 0
+    views: ClassVar[dict[tuple[type, str], Any]] = {}
 
     @classmethod
     def _prepare_stage_creation(cls) -> None:
@@ -457,6 +458,7 @@ def close(cls) -> None:
             cls.clear_callbacks()
         finally:
             if is_active_manager:
+                PhysicsManager.views.clear()
                 PhysicsManager._sim = None
                 PhysicsManager._cfg = None
                 PhysicsManager._sim_time = 0.0

source/isaaclab/isaaclab/physics/physics_manager.py

@@ -26,6 +26,7 @@ class TestManager(PhysicsManager):
     monkeypatch.setattr(PhysicsManager, "_sim", SimpleNamespace(physics_manager=TestManager))
     monkeypatch.setattr(PhysicsManager, "_cfg", object())
     monkeypatch.setattr(PhysicsManager, "_sim_time", 1.0)
+    monkeypatch.setattr(PhysicsManager, "views", {(TestManager, "/World/Robot"): object()})
 
     TestManager.register_callback(
         lambda _payload: events.append("first"),
@@ -71,6 +72,7 @@ def failing_listener(_payload):
     assert PhysicsManager._sim is None
     assert PhysicsManager._cfg is None
     assert PhysicsManager._sim_time == 0.0
+    assert PhysicsManager.views == {}
 
 
 def test_close_surfaces_stop_errors_stored_by_safe_callback_invoke(monkeypatch):

source/isaaclab/test/sim/test_physics_manager_lifecycle.py

@@ -0,0 +1,4 @@
+Fixed
+^^^^^
+
+* Registered every configured child solver's builder attributes for coupled Newton models.

source/isaaclab_contrib/changelog.d/ooctipus-newton-active-solver-attributes.rst

@@ -188,17 +188,15 @@ def _validate_resolved_entries(
     def _register_builder_attributes(cls, builder: ModelBuilder) -> None:
         """Register custom attributes required by nested coupled entries."""
         super()._register_builder_attributes(builder)
-        solver_cfg = getattr(PhysicsManager._cfg, "solver_cfg", None)
-        if any(isinstance(entry.solver_cfg, MPMSolverCfg) for entry in getattr(solver_cfg, "entries", ())):
-            NewtonMPMManager._register_builder_attributes(builder)
+        for entry in PhysicsManager._cfg.solver_cfg.entries:
+            entry.solver_cfg.class_type._register_builder_attributes(builder)
 
     @classmethod
     def _prepare_builder_for_finalize(cls, builder: ModelBuilder) -> None:
         """Normalize kinematic colliders when a coupled entry uses implicit MPM."""
         super()._prepare_builder_for_finalize(builder)
-        solver_cfg = getattr(PhysicsManager._cfg, "solver_cfg", None)
-        if any(isinstance(entry.solver_cfg, MPMSolverCfg) for entry in getattr(solver_cfg, "entries", ())):
-            NewtonMPMManager._prepare_builder_for_finalize(builder)
+        for entry in PhysicsManager._cfg.solver_cfg.entries:
+            entry.solver_cfg.class_type._prepare_builder_for_finalize(builder)
 
     @classmethod
     def _initialize_contacts(cls) -> None:

source/isaaclab_contrib/isaaclab_contrib/coupling/coupler.py

@@ -13,6 +13,8 @@
 from newton import Contacts, Control, Model, State
 from newton.solvers import SolverBase, SolverMuJoCo, SolverVBD
 
+from isaaclab.physics import PhysicsManager
+
 from .kernels import _kernel_body_particle_reaction
 from .newton_manager_cfg import CoupledMJWarpVBDSolverCfg
 
@@ -27,12 +29,11 @@ class NewtonCoupledMJWarpVBDManager(NewtonVBDManager):
     _rigid_solver: SolverMuJoCo | None = None
     _soft_solver: SolverVBD | None = None
     _coupling_mode: str | None = None
+    _builder_attribute_solvers = (SolverMuJoCo,)
 
     @classmethod
     def step(cls) -> None:
         """Step the physics simulation."""
-        from isaaclab.physics import PhysicsManager
-
         sim = PhysicsManager._sim
         if sim is None or not sim.is_playing():
             return

source/isaaclab_contrib/isaaclab_contrib/custom_coupling/coupled_mjwarp_vbd_manager.py

@@ -30,7 +30,7 @@
     XPBDSolverCfg,
 )
 from isaaclab_newton.physics.newton_manager import NewtonManager
-from newton import ShapeFlags
+from newton import ModelBuilder, ShapeFlags
 from newton.solvers.experimental.coupled import SolverCoupledADMM, SolverCoupledProxy
 
 from isaaclab_contrib.coupling import (
@@ -579,6 +579,23 @@ def test_mpm_entry_reuses_builder_lifecycle_hooks(monkeypatch):
     assert events == [("register", builder), ("finalize", builder)]
 
 
+def test_nested_solvers_register_their_builder_attributes(monkeypatch):
+    """A coupled model declares the schemas consumed by each configured child solver."""
+    builder = ModelBuilder()
+    solver_cfg = CouplerProxyCfg(
+        entries=[
+            CouplerEntryCfg(name="rigid", solver_cfg=MJWarpSolverCfg()),
+            CouplerEntryCfg(name="media", solver_cfg=MPMSolverCfg()),
+        ]
+    )
+    monkeypatch.setattr(coupler.PhysicsManager, "_cfg", SimpleNamespace(solver_cfg=solver_cfg))
+
+    NewtonCouplerManager._register_builder_attributes(builder)
+
+    assert builder.has_custom_attribute("mujoco:condim")
+    assert builder.has_custom_attribute("mpm:young_modulus")
+
+
 def test_contact_initialization_prepares_coupled_solver_buffers(monkeypatch):
     """Entry-local contact buffers are allocated before graph capture."""
     events: list[tuple[str, object | None]] = []

source/isaaclab_contrib/test/coupling/test_coupler.py

@@ -5,16 +5,29 @@
 
 """Unit tests for the custom coupling manager."""
 
+from types import SimpleNamespace
 from unittest.mock import MagicMock
 
 import pytest
 from isaaclab_newton.physics import MJWarpSolverCfg, VBDSolverCfg
+from newton import ModelBuilder
 
 import isaaclab_contrib.custom_coupling.coupled_mjwarp_vbd_manager as manager_module
 from isaaclab_contrib.custom_coupling.coupled_mjwarp_vbd_manager import NewtonCoupledMJWarpVBDManager
 from isaaclab_contrib.custom_coupling.newton_manager_cfg import CoupledMJWarpVBDSolverCfg
 
 
+def test_register_builder_attributes_includes_nested_solvers(monkeypatch: pytest.MonkeyPatch) -> None:
+    """The custom coupled manager delegates builder setup to both configured children."""
+    cfg = CoupledMJWarpVBDSolverCfg()
+    monkeypatch.setattr(manager_module.PhysicsManager, "_cfg", SimpleNamespace(solver_cfg=cfg))
+    builder = ModelBuilder()
+
+    NewtonCoupledMJWarpVBDManager._register_builder_attributes(builder)
+
+    assert builder.has_custom_attribute("mujoco:condim")
+
+
 def test_reset_forwards_to_both_subsolvers(monkeypatch: pytest.MonkeyPatch) -> None:
     """Reset the real sub-solvers instead of the dummy solver slot."""
     rigid_solver = MagicMock()

source/isaaclab_contrib/test/custom_coupling/test_manager.py

@@ -0,0 +1,7 @@
+Changed
+^^^^^^^
+
+* Registered builder attributes only for the active Newton solver instead of importing and allocating inactive
+  solver data.
+* Reused target-mode resolution across identical articulation clones and one canonical articulation view between
+  each articulation and its joint-wrench sensor.

source/isaaclab_newton/changelog.d/ooctipus-newton-active-solver-attributes.rst

@@ -9,6 +9,7 @@
 from __future__ import annotations
 
 import logging
+import re
 import warnings
 from collections.abc import Sequence
 from typing import TYPE_CHECKING
@@ -27,7 +28,7 @@
 from isaaclab.assets.articulation import ordering_kernels
 from isaaclab.assets.articulation.base_articulation import BaseArticulation
 from isaaclab.physics import PhysicsEvent
-from isaaclab.sim.utils.queries import path_expr_to_glob, resolve_matching_prims_from_source
+from isaaclab.sim.utils.queries import resolve_matching_prims_from_source
 from isaaclab.utils.string import resolve_matching_names, resolve_matching_names_values
 from isaaclab.utils.version import get_isaac_sim_version, has_kit
 from isaaclab.utils.warp import ProxyArray
@@ -84,10 +85,11 @@ def has_articulation_root_api(prim) -> bool:
 
 def _configure_builder_joint_target_modes(builder, cfg: ArticulationCfg) -> None:
     """Resolve configured actuator gains into Newton builder target modes before finalization."""
-    root_prim_path_regex = path_expr_to_glob(_resolve_articulation_root_prim_path_expr(cfg)).replace("*", ".*")
+    root_prim_path_regex = _resolve_articulation_root_prim_path_expr(cfg)
     articulation_ids, _ = resolve_matching_names(
         root_prim_path_regex, builder.articulation_label, raise_when_no_match=False
     )
+    source_dof_ids = None
     for articulation_id in articulation_ids:
         joint_start = builder.articulation_start[articulation_id]
         joint_end = builder.articulation_end[articulation_id]
@@ -107,6 +109,11 @@ def _configure_builder_joint_target_modes(builder, cfg: ArticulationCfg) -> None
                 dof_ids.append(dof_id)
                 dof_names.append(joint_name if dof_end - dof_start == 1 else f"{joint_name}:{axis_index}")
 
+        if source_dof_ids is not None:
+            for source_dof_id, dof_id in zip(source_dof_ids, dof_ids, strict=True):
+                builder.joint_target_mode[dof_id] = builder.joint_target_mode[source_dof_id]
+            continue
+
         for actuator_cfg in cfg.actuators.values():
             matched_indices, matched_names = resolve_matching_names(
                 actuator_cfg.joint_names_expr, dof_names, raise_when_no_match=False
@@ -130,6 +137,7 @@ def _configure_builder_joint_target_modes(builder, cfg: ArticulationCfg) -> None
                     if _is_implicit_actuator_cfg(actuator_cfg)
                     else JointTargetMode.EFFORT
                 )
+        source_dof_ids = dof_ids
 
 
 class Articulation(BaseArticulation):
@@ -3279,19 +3287,14 @@ def write_spatial_tendon_properties_to_sim_mask(
     """
 
     def _initialize_impl(self):
-        # obtain global simulation view
-        self._physics_sim_view = SimulationManager.get_physics_sim_view()
-
         root_prim_path_expr = _resolve_articulation_root_prim_path_expr(self.cfg)
         # -- articulation
-        self._root_view = ArticulationView(
+        self._root_view = SimulationManager.views[SimulationManager, root_prim_path_expr] = ArticulationView(
             SimulationManager.get_model(),
-            path_expr_to_glob(root_prim_path_expr),
+            re.compile(root_prim_path_expr),
             verbose=False,
             exclude_joint_types=[JointType.FREE, JointType.FIXED],
         )
-        # Register view with Newton manager so sensors (e.g. FrameTransformer) can find it.
-        SimulationManager.get_physics_sim_view().append(self._root_view)
 
         # container for data access
         self._data = ArticulationData(self.root_view, self.device)