diff --git a/.github/actions/install-ci-run/action.yml b/.github/actions/install-ci-run/action.yml
index f86ef7105a33..85a1c4fdc358 100644
--- a/.github/actions/install-ci-run/action.yml
+++ b/.github/actions/install-ci-run/action.yml
@@ -7,13 +7,23 @@ name: 'Run Installation CI Tests'
 description: >
   Runs the install_ci suite inside the project's Docker harness via
   tools/run_install_ci.py and uploads the JUnit XML report as an artifact
-  named install-ci-junit-<runner.arch>.
+  named install-ci-junit-<runner.arch>. When a Testmon data dir is provided,
+  the .testmondata database is also uploaded as install-ci-testmon-<runner.arch>
+  for triage.
 
 inputs:
   base-image:
     description: 'Docker base image for the test container'
     required: false
     default: 'ubuntu:24.04'
+  testmon-data-dir:
+    description: 'Host directory for the persisted Testmon dependency database'
+    required: false
+    default: ''
+  testmon-mode:
+    description: 'Testmon mode: select affected tests, collect a full baseline, or off'
+    required: false
+    default: 'off'
   test-filter:
     description: 'pytest -k expression (empty = run everything)'
     required: false
@@ -33,12 +43,28 @@ runs:
       shell: bash
       env:
         BASE_IMAGE: ${{ inputs.base-image }}
+        TESTMON_DATA_DIR: ${{ inputs.testmon-data-dir }}
+        TESTMON_MODE: ${{ inputs.testmon-mode }}
         TEST_FILTER: ${{ inputs.test-filter }}
       run: |
         args=(docker --gpu --base-image "$BASE_IMAGE"
               --build-wheel
+              --testmon-data-dir "$TESTMON_DATA_DIR"
               --results-dir "${{ github.workspace }}/results"
               -- --tb=short -sv)
+        case "$TESTMON_MODE" in
+          select)
+            if [ -s "$TESTMON_DATA_DIR/.testmondata" ]; then
+              args+=(--testmon --testmon-forceselect)
+            else
+              echo "::warning::Testmon data is missing; collecting a full baseline"
+              args+=(--testmon --testmon-noselect)
+            fi
+            ;;
+          collect) args+=(--testmon --testmon-noselect) ;;
+          off) ;;
+          *) echo "Unknown Testmon mode: $TESTMON_MODE"; exit 1 ;;
+        esac
         [ -n "$TEST_FILTER" ] && args+=(-k "$TEST_FILTER")
         # Make `python3` resolve to the uv-managed 3.12 for build.sh's gen_pyproject.py.
         # --seed installs pip/setuptools/wheel into the venv so build.sh's `python3 -m pip install`
@@ -46,6 +72,14 @@ runs:
         uv venv --seed --python 3.12 "${RUNNER_TEMP}/venv-runner"
         source "${RUNNER_TEMP}/venv-runner/bin/activate"
         tools/run_install_ci.py "${args[@]}"
+    - name: Upload Testmon data
+      if: always() && inputs.testmon-data-dir != ''
+      uses: actions/upload-artifact@v7
+      with:
+        name: install-ci-testmon-${{ runner.arch }}
+        path: ${{ inputs.testmon-data-dir }}/.testmondata
+        if-no-files-found: warn
+        retention-days: 7
     - name: Upload JUnit XML report
       if: always()
       id: upload-junit-report
diff --git a/.github/actions/run-package-tests/action.yml b/.github/actions/run-package-tests/action.yml
index 9ee6dcddd9b8..23891e32daab 100644
--- a/.github/actions/run-package-tests/action.yml
+++ b/.github/actions/run-package-tests/action.yml
@@ -67,14 +67,6 @@ inputs:
     description: 'Comma-separated list of specific test files to include'
     default: ''
     required: false
-  test-node-ids-file:
-    description: 'TOML file containing exact pytest node IDs to run'
-    default: ''
-    required: false
-  test-node-ids-key:
-    description: 'Top-level key in test-node-ids-file containing the node IDs for this job'
-    default: ''
-    required: false
   pytest-options:
     description: 'Additional pytest options'
     default: ''
@@ -83,6 +75,10 @@ inputs:
     description: 'Space-separated pip packages to install inside the Docker container before pytest starts'
     default: ''
     required: false
+  testmon-mode:
+    description: 'Override Testmon mode with select, collect, or off'
+    default: ''
+    required: false
   wheelhouse-resource:
     description: 'Optional NGC resource containing wheelhouse/ and manifest.json for offline pip installs'
     default: ''
@@ -158,6 +154,33 @@ runs:
         printf "🔵 Image pull took %dm %ds\n" $((elapsed/60)) $((elapsed%60))
         echo "🔵 Docker Image Pulled in ${elapsed}s" >> "$GITHUB_STEP_SUMMARY"
 
+    - name: Select Testmon Mode
+      id: testmon-mode
+      shell: bash
+      env:
+        GH_TOKEN: ${{ github.token }}
+        PR_NUMBER: ${{ github.event.pull_request.number }}
+        REPO: ${{ github.repository }}
+        REQUESTED_MODE: ${{ inputs.testmon-mode }}
+      run: |
+        mode="${REQUESTED_MODE:-collect}"
+        if [ -z "$REQUESTED_MODE" ] && [ "${{ github.event_name }}" = "pull_request" ]; then
+          if changed_files="$(gh api --paginate "repos/$REPO/pulls/$PR_NUMBER/files" --jq '.[].filename')"; then
+            mode="$(printf '%s\n' "$changed_files" | python3 .github/actions/run-package-tests/select_testmon_mode.py)"
+          else
+            echo "::warning::Could not list changed files; running the full test suite"
+          fi
+        fi
+        echo "mode=$mode" >> "$GITHUB_OUTPUT"
+        echo "Testmon mode: $mode" >> "$GITHUB_STEP_SUMMARY"
+
+    - name: Restore Testmon Data
+      if: steps.testmon-mode.outputs.mode != 'off'
+      uses: actions/cache@v4
+      with:
+        path: .testmon/${{ inputs.container-name }}
+        key: testmon-${{ runner.arch }}-${{ inputs.container-name }}-${{ hashFiles('conftest.py', 'tools/conftest.py', 'tools/testmon_subprocess_coverage.py', 'tools/test_settings.py', '.github/actions/run-tests/action.yml', 'docker/Dockerfile.base', 'docker/Dockerfile.curobo', '.github/workflows/config.yaml') }}-${{ github.sha }}
+        restore-keys: testmon-${{ runner.arch }}-${{ inputs.container-name }}-${{ hashFiles('conftest.py', 'tools/conftest.py', 'tools/testmon_subprocess_coverage.py', 'tools/test_settings.py', '.github/actions/run-tests/action.yml', 'docker/Dockerfile.base', 'docker/Dockerfile.curobo', '.github/workflows/config.yaml') }}-
     - name: Restore NGC CLI cache
       if: inputs.wheelhouse-resource != '' && env.NGC_API_KEY != ''
       uses: actions/cache@v4
@@ -298,10 +321,10 @@ runs:
         curobo-only: ${{ inputs.curobo-only }}
         quarantined-only: ${{ inputs.quarantined-only }}
         include-files: ${{ inputs.include-files }}
-        test-node-ids-file: ${{ inputs.test-node-ids-file }}
-        test-node-ids-key: ${{ inputs.test-node-ids-key }}
         volume-mount-source: ${{ github.workspace }}
         extra-pip-packages: ${{ inputs.extra-pip-packages }}
+        testmon-data-dir: .testmon/${{ inputs.container-name }}
+        testmon-mode: ${{ steps.testmon-mode.outputs.mode }}
         wheelhouse-host-dir: ${{ steps.extract-wheelhouse.outputs.wheelhouse_host_dir }}
         wheelhouse-packages: ${{ inputs.wheelhouse-packages }}
         omni-github-test-type: ${{ inputs.omni-github-test-type }}
diff --git a/.github/actions/run-package-tests/select_testmon_mode.py b/.github/actions/run-package-tests/select_testmon_mode.py
new file mode 100644
index 000000000000..c7b575b75984
--- /dev/null
+++ b/.github/actions/run-package-tests/select_testmon_mode.py
@@ -0,0 +1,39 @@
+# Copyright (c) 2022-2026, The Isaac Lab Project Developers (https://github.com/isaac-sim/IsaacLab/blob/main/CONTRIBUTORS.md).
+# All rights reserved.
+#
+# SPDX-License-Identifier: BSD-3-Clause
+
+"""Choose whether Testmon can safely select affected tests for a change."""
+
+from __future__ import annotations
+
+import re
+import sys
+
+_RELEVANT = re.compile(
+    r"^(?:source|docker|tools|apps|scripts)/"
+    r"|^\.github/(?:workflows/[^/]+\.ya?ml|actions/)"
+    r"|^\.gitmodules$"
+    r"|^[^/]+\.(?:toml|yaml|yml|json|ini|cfg|conf|lock|sh|bat|ps1)$"
+)
+_IGNORED_SUFFIXES = (".md", ".rst", ".skip")
+
+
+def _is_tracked_python(path: str) -> bool:
+    """Return whether ``path`` is a Python source file whose dependencies Testmon tracks.
+
+    Python files under ``.github/`` (e.g. action helper scripts) run outside the pytest
+    process, so Testmon has no dependency data for them; changes to those files must fall
+    back to a full collection rather than the Python-only fast path.
+    """
+    return path.endswith(".py") and not path.startswith(".github/")
+
+
+def select_testmon_mode(paths: list[str]) -> str:
+    """Return ``select`` for tracked Python-only changes, otherwise ``collect``."""
+    relevant = [path for path in paths if _RELEVANT.search(path) and not path.endswith(_IGNORED_SUFFIXES)]
+    return "select" if not relevant or all(_is_tracked_python(path) for path in relevant) else "collect"
+
+
+if __name__ == "__main__":
+    print(select_testmon_mode([line.strip() for line in sys.stdin if line.strip()]))
diff --git a/.github/actions/run-package-tests/test_select_testmon_mode.py b/.github/actions/run-package-tests/test_select_testmon_mode.py
new file mode 100644
index 000000000000..2d33b4d2eb87
--- /dev/null
+++ b/.github/actions/run-package-tests/test_select_testmon_mode.py
@@ -0,0 +1,45 @@
+# Copyright (c) 2022-2026, The Isaac Lab Project Developers (https://github.com/isaac-sim/IsaacLab/blob/main/CONTRIBUTORS.md).
+# All rights reserved.
+#
+# SPDX-License-Identifier: BSD-3-Clause
+
+"""Tests for changed-file Testmon mode selection."""
+
+import importlib.util
+from pathlib import Path
+
+_MODULE_PATH = Path(__file__).with_name("select_testmon_mode.py")
+_SPEC = importlib.util.spec_from_file_location("select_testmon_mode", _MODULE_PATH)
+assert _SPEC and _SPEC.loader
+_MODULE = importlib.util.module_from_spec(_SPEC)
+_SPEC.loader.exec_module(_MODULE)
+select_testmon_mode = _MODULE.select_testmon_mode
+
+
+def test_python_only_relevant_changes_select_affected_tests() -> None:
+    assert select_testmon_mode(["source/isaaclab/isaaclab/app.py", "tools/helper.py"]) == "select"
+
+
+def test_irrelevant_changes_select_no_affected_tests() -> None:
+    assert select_testmon_mode(["docs/guide.md", "source/isaaclab/changelog.d/change.skip"]) == "select"
+
+
+def test_static_relevant_change_collects_full_suite() -> None:
+    assert select_testmon_mode(["source/isaaclab/config/extension.toml"]) == "collect"
+
+
+def test_mixed_change_collects_full_suite() -> None:
+    assert select_testmon_mode(["source/isaaclab/code.py", "docker/Dockerfile.base"]) == "collect"
+
+
+def test_workflow_yaml_change_collects_full_suite() -> None:
+    # A workflow change that testmon cannot reason about must run the full suite,
+    # otherwise a workflow-only PR would trigger a job that deselects every test.
+    assert select_testmon_mode([".github/workflows/install-ci.yml"]) == "collect"
+
+
+def test_action_python_change_collects_full_suite() -> None:
+    # Python helpers under .github/actions/ run outside pytest, so testmon has no
+    # dependency data for them; a change to one must run the full suite rather than
+    # taking the Python-only fast path and deselecting every test.
+    assert select_testmon_mode([".github/actions/run-package-tests/select_testmon_mode.py"]) == "collect"
diff --git a/.github/actions/run-tests/action.yml b/.github/actions/run-tests/action.yml
index fbc7043cdf8f..9f5a51dc8029 100644
--- a/.github/actions/run-tests/action.yml
+++ b/.github/actions/run-tests/action.yml
@@ -61,14 +61,6 @@ inputs:
     description: 'Comma-separated list of specific test file paths to include (e.g., source/pkg/test/test_a.py,source/pkg/test/test_b.py)'
     default: ''
     required: false
-  test-node-ids-file:
-    description: 'TOML file containing exact pytest node IDs to run'
-    default: ''
-    required: false
-  test-node-ids-key:
-    description: 'Top-level key in test-node-ids-file containing the node IDs for this job'
-    default: ''
-    required: false
   shard-index:
     description: 'Zero-based index of this shard (used with shard-count to split tests across parallel jobs)'
     default: ''
@@ -85,6 +77,13 @@ inputs:
     description: 'Space-separated pip packages to install inside the Docker container before pytest starts'
     default: ''
     required: false
+  testmon-data-dir:
+    description: 'Workspace-relative directory for the Testmon dependency database'
+    default: ''
+    required: false
+  testmon-mode:
+    description: 'Testmon mode: select affected tests, collect a full baseline, or off'
+    default: 'off'
   wheelhouse-host-dir:
     description: 'Host directory containing wheelhouse/ and manifest.json for offline pip installs'
     default: ''
@@ -126,10 +125,10 @@ runs:
           local shard_count="${13}"
           local volume_mount_source="${14}"
           local extra_pip_packages="${15}"
-          local test_node_ids_file="${16}"
-          local test_node_ids_key="${17}"
-          local wheelhouse_host_dir="${18}"
-          local wheelhouse_packages="${19}"
+          local wheelhouse_host_dir="${16}"
+          local wheelhouse_packages="${17}"
+          local testmon_data_dir="${18}"
+          local testmon_mode="${19}"
           local test_k_expr="${20}"
           local logs_pid=""
           local wait_pid=""
@@ -156,6 +155,9 @@ runs:
           if [ -n "$extra_pip_packages" ]; then
             echo "With extra pip packages: $extra_pip_packages"
           fi
+          if [ "$testmon_mode" != "off" ]; then
+            echo "Testmon mode: $testmon_mode"
+          fi
           if [ -n "$wheelhouse_host_dir" ]; then
             echo "With wheelhouse host directory: $wheelhouse_host_dir"
           fi
@@ -174,25 +176,10 @@ runs:
           if [ -n "$include_files" ]; then
             echo "Include files: $include_files"
           fi
-          if [ -n "$test_node_ids_file" ]; then
-            echo "Test node IDs file: $test_node_ids_file"
-          fi
-          if [ -n "$test_node_ids_key" ]; then
-            echo "Test node IDs key: $test_node_ids_key"
-          fi
           if [ -n "$shard_index" ] && [ -n "$shard_count" ]; then
             echo "Shard: $shard_index of $shard_count"
           fi
 
-          if [ -n "$test_node_ids_file" ] || [ -n "$test_node_ids_key" ]; then
-            if [ -z "$test_node_ids_file" ] || [ -z "$test_node_ids_key" ]; then
-              echo "Both test-node-ids-file and test-node-ids-key must be set together"
-              return 1
-            fi
-            export TEST_NODE_IDS_FILE="$test_node_ids_file"
-            export TEST_NODE_IDS_KEY="$test_node_ids_key"
-          fi
-
           # Create reports directory
           mkdir -p "$reports_dir"
 
@@ -234,11 +221,6 @@ runs:
             echo "Setting TEST_NODE_IDS"
           fi
 
-          if [ -n "${TEST_NODE_IDS_FILE:-}" ]; then
-            docker_env_vars="$docker_env_vars -e TEST_NODE_IDS_FILE -e TEST_NODE_IDS_KEY"
-            echo "Setting TEST_NODE_IDS_FILE=$TEST_NODE_IDS_FILE TEST_NODE_IDS_KEY=$TEST_NODE_IDS_KEY"
-          fi
-
           if [ -n "$shard_index" ] && [ -n "$shard_count" ]; then
             docker_env_vars="$docker_env_vars -e TEST_SHARD_INDEX=$shard_index -e TEST_SHARD_COUNT=$shard_count"
             echo "Setting TEST_SHARD_INDEX=$shard_index TEST_SHARD_COUNT=$shard_count"
@@ -273,6 +255,24 @@ runs:
             docker_env_vars="$docker_env_vars -e TEST_EXTRA_PIP_PACKAGES"
           fi
 
+          testmon_options=""
+          if [ -n "$testmon_data_dir" ]; then
+            mkdir -p "$testmon_data_dir"
+            docker_env_vars="$docker_env_vars -e TESTMON_DATAFILE=/workspace/isaaclab/$testmon_data_dir/.testmondata"
+            case "$testmon_mode" in
+              select)
+                if [ -s "$testmon_data_dir/.testmondata" ]; then
+                  testmon_options="--testmon --testmon-forceselect"
+                else
+                  echo "::warning::Testmon data is missing; collecting a full baseline"
+                  testmon_options="--testmon --testmon-noselect"
+                fi
+                ;;
+              collect) testmon_options="--testmon --testmon-noselect" ;;
+              off) ;;
+              *) echo "Unknown Testmon mode: $testmon_mode"; return 1 ;;
+            esac
+          fi
           if [ -n "$test_k_expr" ]; then
             export TEST_K_EXPR="$test_k_expr"
             docker_env_vars="$docker_env_vars -e TEST_K_EXPR"
@@ -383,7 +383,7 @@ runs:
               # set this detect-only flag, which makes cold asset downloads
               # fall back to slow repeated retries.
               unset HUB__ARGS__DETECT_ONLY
-              ./isaaclab.sh -p -m pip install pytest pytest-mock junitparser flatdict flaky \"coverage>=7.6.1\"
+              ./isaaclab.sh -p -m pip install pytest pytest-mock \"pytest-testmon>=2.2,<3\" junitparser flatdict flaky \"coverage>=7.6.1\"
               if [ -n \"\${TEST_WHEELHOUSE_PACKAGES:-}\" ]; then
                 if [ ! -d \"\${TEST_WHEELHOUSE_PATH:-}\" ]; then
                   echo \"Wheelhouse path is missing: \${TEST_WHEELHOUSE_PATH:-}\"
@@ -415,7 +415,7 @@ runs:
                 esac
               fi
               echo 'Starting pytest with path: $test_path'
-              ./isaaclab.sh -p -m pytest --ignore=tools/conftest.py $test_path $pytest_options -v --junitxml=tests/$result_file
+              ./isaaclab.sh -p -m pytest --ignore=tools/conftest.py $test_path $pytest_options $testmon_options -v --junitxml=tests/$result_file
             "
 
           # Stream container logs in background.
@@ -512,7 +512,7 @@ runs:
         }
 
         # Call the function with provided parameters
-        run_tests "${{ inputs.test-path }}" "${{ inputs.result-file }}" "${{ inputs.container-name }}" "${{ inputs.image-tag }}" "${{ inputs.reports-dir }}" "$PYTEST_OPTIONS" "${{ inputs.filter-pattern }}" "${{ inputs.exclude-pattern }}" "${{ inputs.curobo-only }}" "${{ inputs.include-files }}" "${{ inputs.quarantined-only }}" "${{ inputs.shard-index }}" "${{ inputs.shard-count }}" "${{ inputs.volume-mount-source }}" "${{ inputs.extra-pip-packages }}" "${{ inputs.test-node-ids-file }}" "${{ inputs.test-node-ids-key }}" "${{ inputs.wheelhouse-host-dir }}" "${{ inputs.wheelhouse-packages }}" "$TEST_K_EXPR_INPUT"
+        run_tests "${{ inputs.test-path }}" "${{ inputs.result-file }}" "${{ inputs.container-name }}" "${{ inputs.image-tag }}" "${{ inputs.reports-dir }}" "$PYTEST_OPTIONS" "${{ inputs.filter-pattern }}" "${{ inputs.exclude-pattern }}" "${{ inputs.curobo-only }}" "${{ inputs.include-files }}" "${{ inputs.quarantined-only }}" "${{ inputs.shard-index }}" "${{ inputs.shard-count }}" "${{ inputs.volume-mount-source }}" "${{ inputs.extra-pip-packages }}" "${{ inputs.wheelhouse-host-dir }}" "${{ inputs.wheelhouse-packages }}" "${{ inputs.testmon-data-dir }}" "${{ inputs.testmon-mode }}" "$TEST_K_EXPR_INPUT"
 
     - name: Kill container on cancellation
       if: cancelled()
diff --git a/.github/test-subsets/postmerge-rendering.toml b/.github/test-subsets/postmerge-rendering.toml
deleted file mode 100644
index ee52d8f1f548..000000000000
--- a/.github/test-subsets/postmerge-rendering.toml
+++ /dev/null
@@ -1,34 +0,0 @@
-# Copyright (c) 2022-2026, The Isaac Lab Project Developers (https://github.com/isaac-sim/IsaacLab/blob/main/CONTRIBUTORS.md).
-# All rights reserved.
-#
-# SPDX-License-Identifier: BSD-3-Clause
-
-# Stable rendering correctness tests used by post-merge CI.
-rendering-correctness = [
-  "source/isaaclab_tasks/test/core/test_rendering_cartpole.py::test_rendering_cartpole[newton-isaacsim_rtx-albedo]",
-  "source/isaaclab_tasks/test/core/test_rendering_cartpole.py::test_rendering_cartpole[newton-isaacsim_rtx-depth]",
-  "source/isaaclab_tasks/test/core/test_rendering_cartpole.py::test_rendering_cartpole[newton-isaacsim_rtx-rgb]",
-  "source/isaaclab_tasks/test/core/test_rendering_cartpole.py::test_rendering_cartpole[newton-isaacsim_rtx-semantic_segmentation]",
-  "source/isaaclab_tasks/test/core/test_rendering_cartpole.py::test_rendering_cartpole[physx-isaacsim_rtx-albedo]",
-  "source/isaaclab_tasks/test/core/test_rendering_cartpole.py::test_rendering_cartpole[physx-isaacsim_rtx-depth]",
-  "source/isaaclab_tasks/test/core/test_rendering_cartpole.py::test_rendering_cartpole[physx-isaacsim_rtx-rgb]",
-  "source/isaaclab_tasks/test/core/test_rendering_cartpole.py::test_rendering_cartpole[physx-isaacsim_rtx-semantic_segmentation]",
-  "source/isaaclab_tasks/test/core/test_rendering_cartpole.py::test_rendering_cartpole[physx-newton_warp-depth]",
-  "source/isaaclab_tasks/test/core/test_rendering_cartpole.py::test_rendering_cartpole[physx-newton_warp-rgb]",
-  "source/isaaclab_tasks/test/core/test_rendering_registered_tasks.py::test_rendering_registered_tasks[Isaac-Cartpole-Camera-Direct-albedo-cartpole]",
-  "source/isaaclab_tasks/test/core/test_rendering_registered_tasks.py::test_rendering_registered_tasks[Isaac-Cartpole-Camera-Direct-depth-cartpole]",
-  "source/isaaclab_tasks/test/core/test_rendering_registered_tasks.py::test_rendering_registered_tasks[Isaac-Cartpole-Camera-Direct-None-cartpole]",
-  "source/isaaclab_tasks/test/core/test_rendering_registered_tasks.py::test_rendering_registered_tasks[Isaac-Cartpole-Camera-Direct-rgb-cartpole]",
-]
-
-rendering-correctness-kitless = [
-  "source/isaaclab_tasks/test/core/test_rendering_cartpole_kitless.py::test_rendering_cartpole_kitless[newton-newton_warp-depth]",
-  "source/isaaclab_tasks/test/core/test_rendering_cartpole_kitless.py::test_rendering_cartpole_kitless[newton-newton_warp-rgb]",
-  "source/isaaclab_tasks/test/core/test_rendering_cartpole_kitless.py::test_rendering_cartpole_kitless[newton-ovrtx-albedo]",
-  "source/isaaclab_tasks/test/core/test_rendering_cartpole_kitless.py::test_rendering_cartpole_kitless[newton-ovrtx-depth]",
-  "source/isaaclab_tasks/test/core/test_rendering_cartpole_kitless.py::test_rendering_cartpole_kitless[ovphysx-newton_warp-depth]",
-  "source/isaaclab_tasks/test/core/test_rendering_cartpole_kitless.py::test_rendering_cartpole_kitless[ovphysx-newton_warp-rgb]",
-  "source/isaaclab_tasks/test/core/test_rendering_cartpole_kitless.py::test_rendering_cartpole_kitless[ovphysx-ovrtx-albedo]",
-  "source/isaaclab_tasks/test/core/test_rendering_cartpole_kitless.py::test_rendering_cartpole_kitless[ovphysx-ovrtx-rgb]",
-  "source/isaaclab_tasks/test/core/test_rendering_cartpole_kitless.py::test_rendering_cartpole_kitless[ovphysx-ovrtx-semantic_segmentation]",
-]
diff --git a/.github/workflows/build.yaml b/.github/workflows/build.yaml
index 39f9ffab1b2c..2750e8851195 100644
--- a/.github/workflows/build.yaml
+++ b/.github/workflows/build.yaml
@@ -105,12 +105,11 @@ jobs:
           $'^\\.github/workflows/build\\.yaml$\tThis workflow file'
           $'^\\.github/workflows/config\\.yaml$\tBase image config'
           $'^\\.github/actions/\tCI actions'
-          $'^\\.github/test-subsets/\tCI test subset config'
         )
         if [ "$EVENT_NAME" = "push" ]; then
-          triggered_jobs="Docker base build job + rendering-correctness + rendering-correctness-kitless"
+          triggered_jobs="Docker build jobs + all test-* matrix jobs (full suite via Testmon collect)"
         else
-          triggered_jobs="Docker build jobs + all test-* matrix jobs"
+          triggered_jobs="Docker build jobs + all test-* matrix jobs (Testmon-selected subset)"
         fi
 
         render_table() {
@@ -255,7 +254,6 @@ jobs:
     runs-on: [self-hosted, gpu]
     needs: [changes, config]
     if: >-
-      github.event_name != 'push' &&
       needs.changes.outputs.run_docker_tests == 'true'
     steps:
     - name: Checkout Code
@@ -283,7 +281,6 @@ jobs:
     continue-on-error: true
     needs: [build, config]
     if: >-
-      github.event_name != 'push' &&
       needs.build.result == 'success'
     steps:
     - uses: actions/checkout@v6
@@ -308,7 +305,6 @@ jobs:
     continue-on-error: true
     needs: [build, config]
     if: >-
-      github.event_name != 'push' &&
       needs.build.result == 'success'
     steps:
     - uses: actions/checkout@v6
@@ -333,7 +329,6 @@ jobs:
     continue-on-error: true
     needs: [build, config]
     if: >-
-      github.event_name != 'push' &&
       needs.build.result == 'success'
     steps:
     - uses: actions/checkout@v6
@@ -357,7 +352,6 @@ jobs:
     timeout-minutes: 180
     needs: [build, config]
     if: >-
-      github.event_name != 'push' &&
       needs.build.result == 'success'
     steps:
     - uses: actions/checkout@v6
@@ -380,7 +374,6 @@ jobs:
     timeout-minutes: 180
     needs: [build, config]
     if: >-
-      github.event_name != 'push' &&
       needs.build.result == 'success'
     steps:
     - uses: actions/checkout@v6
@@ -403,7 +396,6 @@ jobs:
     timeout-minutes: 180
     needs: [build, config]
     if: >-
-      github.event_name != 'push' &&
       needs.build.result == 'success'
     steps:
     - uses: actions/checkout@v6
@@ -426,7 +418,6 @@ jobs:
     timeout-minutes: 180
     needs: [build, config]
     if: >-
-      github.event_name != 'push' &&
       needs.build.result == 'success'
     steps:
     - uses: actions/checkout@v6
@@ -448,7 +439,6 @@ jobs:
     timeout-minutes: 180
     needs: [build, config]
     if: >-
-      github.event_name != 'push' &&
       needs.build.result == 'success'
     steps:
     - uses: actions/checkout@v6
@@ -469,7 +459,6 @@ jobs:
     timeout-minutes: 180
     needs: [build, config]
     if: >-
-      github.event_name != 'push' &&
       needs.build.result == 'success'
     steps:
     - uses: actions/checkout@v6
@@ -490,7 +479,6 @@ jobs:
     timeout-minutes: 180
     needs: [build, config]
     if: >-
-      github.event_name != 'push' &&
       needs.build.result == 'success'
     steps:
     - uses: actions/checkout@v6
@@ -511,7 +499,6 @@ jobs:
     timeout-minutes: 180
     needs: [build, config]
     if: >-
-      github.event_name != 'push' &&
       needs.build.result == 'success'
     steps:
     - uses: actions/checkout@v6
@@ -532,7 +519,6 @@ jobs:
     timeout-minutes: 180
     needs: [build, config]
     if: >-
-      github.event_name != 'push' &&
       needs.build.result == 'success'
     steps:
     - uses: actions/checkout@v6
@@ -553,7 +539,6 @@ jobs:
     timeout-minutes: 180
     needs: [build, config]
     if: >-
-      github.event_name != 'push' &&
       needs.build.result == 'success'
     steps:
     - uses: actions/checkout@v6
@@ -574,7 +559,6 @@ jobs:
     timeout-minutes: 180
     needs: [build, config]
     if: >-
-      github.event_name != 'push' &&
       needs.build.result == 'success'
     steps:
     - uses: actions/checkout@v6
@@ -595,7 +579,6 @@ jobs:
     timeout-minutes: 180
     needs: [build, config]
     if: >-
-      github.event_name != 'push' &&
       needs.build.result == 'success'
     env:
       USE_OVPHYSX_WHEELHOUSE: ${{ needs.config.outputs.ovphysx_wheelhouse_resource != '' && ((github.event_name == 'pull_request' && github.base_ref == 'develop' && github.event.pull_request.head.repo.full_name == github.repository) || (github.event_name != 'pull_request' && github.ref_name == 'develop')) }}
@@ -652,7 +635,6 @@ jobs:
     continue-on-error: true
     needs: [build-curobo, config]
     if: >-
-      github.event_name != 'push' &&
       needs.build-curobo.result == 'success'
     steps:
     - uses: actions/checkout@v6
@@ -702,7 +684,6 @@ jobs:
     continue-on-error: true
     needs: [build-curobo, config]
     if: >-
-      github.event_name != 'push' &&
       needs.build-curobo.result == 'success'
     steps:
     - uses: actions/checkout@v6
@@ -726,7 +707,6 @@ jobs:
     continue-on-error: true
     needs: [build, config]
     if: >-
-      github.event_name != 'push' &&
       needs.build.result == 'success'
     steps:
     - uses: actions/checkout@v6
@@ -767,8 +747,6 @@ jobs:
           test_rendering_dexsuite_kuka_hetero.py,
           test_rendering_registered_tasks.py,
           test_rendering_shadow_hand.py
-        test-node-ids-file: ${{ github.event_name == 'push' && '.github/test-subsets/postmerge-rendering.toml' || '' }}
-        test-node-ids-key: ${{ github.event_name == 'push' && 'rendering-correctness' || '' }}
         container-name: isaac-lab-rendering-correctness-test
         omni-github-test-type: rendering-correctness
 
@@ -804,8 +782,6 @@ jobs:
           test_rendering_dexsuite_kuka_homo_kitless.py,
           test_rendering_dexsuite_kuka_hetero_kitless.py,
           test_rendering_shadow_hand_kitless.py
-        test-node-ids-file: ${{ github.event_name == 'push' && '.github/test-subsets/postmerge-rendering.toml' || '' }}
-        test-node-ids-key: ${{ github.event_name == 'push' && 'rendering-correctness-kitless' || '' }}
         container-name: isaac-lab-rendering-correctness-kitless-test
         omni-github-test-type: rendering-correctness-kitless
   #endregion
diff --git a/.github/workflows/install-ci.yml b/.github/workflows/install-ci.yml
index 226222d425bd..c21d3fcc4e27 100644
--- a/.github/workflows/install-ci.yml
+++ b/.github/workflows/install-ci.yml
@@ -37,7 +37,9 @@ jobs:
     runs-on: ubuntu-latest
     outputs:
       run_install_tests: ${{ steps.detect.outputs.run_install_tests }}
+      testmon_mode: ${{ steps.detect.outputs.testmon_mode }}
     steps:
+      - uses: actions/checkout@v6
       - id: detect
         env:
           GH_TOKEN: ${{ github.token }}
@@ -94,9 +96,10 @@ jobs:
           }
 
           decide() {
-            local decision="$1" reason="$2" files="${3:-}"
+            local decision="$1" reason="$2" files="${3:-}" testmon_mode="${4:-collect}"
             echo "Decision: run_install_tests=$decision ($reason)"
             echo "run_install_tests=$decision" >> "$GITHUB_OUTPUT"
+            echo "testmon_mode=$testmon_mode" >> "$GITHUB_OUTPUT"
             {
               if [ -n "$files" ]; then
                 render_table "$files"
@@ -119,7 +122,8 @@ jobs:
           printf '%s\n' "$changed_files"
 
           if any_match "$changed_files"; then
-            decide true "relevant paths changed" "$changed_files"
+            testmon_mode="$(printf '%s\n' "$changed_files" | python3 .github/actions/run-package-tests/select_testmon_mode.py)"
+            decide true "relevant paths changed" "$changed_files" "$testmon_mode"
           else
             decide false "no relevant paths changed" "$changed_files"
           fi
@@ -133,6 +137,12 @@ jobs:
     steps:
       - name: Checkout
         uses: actions/checkout@v6
+      - name: Restore Testmon Data
+        uses: actions/cache@v4
+        with:
+          path: .testmon/${{ runner.arch }}
+          key: install-ci-testmon-${{ runner.arch }}-${{ hashFiles('conftest.py', 'tools/run_install_ci.py', 'tools/testmon_subprocess_coverage.py', 'tools/testmon_coverage_context.py', 'source/isaaclab/test/install_ci/conftest.py', 'source/isaaclab/test/install_ci/Dockerfile.installci', 'source/isaaclab/test/install_ci/pytest.ini') }}-${{ github.sha }}
+          restore-keys: install-ci-testmon-${{ runner.arch }}-${{ hashFiles('conftest.py', 'tools/run_install_ci.py', 'tools/testmon_subprocess_coverage.py', 'tools/testmon_coverage_context.py', 'source/isaaclab/test/install_ci/conftest.py', 'source/isaaclab/test/install_ci/Dockerfile.installci', 'source/isaaclab/test/install_ci/pytest.ini') }}-
       - name: Show Collected Tests
         uses: ./.github/actions/install-ci-collect
         with:
@@ -141,6 +151,8 @@ jobs:
         uses: ./.github/actions/install-ci-run
         with:
           base-image: ${{ inputs.base_image || 'ubuntu:24.04' }}
+          testmon-data-dir: ${{ github.workspace }}/.testmon/${{ runner.arch }}
+          testmon-mode: ${{ needs.changes.outputs.testmon_mode }}
           test-filter: ${{ inputs.test_filter }}
 
   install-tests-arm:
@@ -152,6 +164,12 @@ jobs:
     steps:
       - name: Checkout
         uses: actions/checkout@v6
+      - name: Restore Testmon Data
+        uses: actions/cache@v4
+        with:
+          path: .testmon/${{ runner.arch }}
+          key: install-ci-testmon-${{ runner.arch }}-${{ hashFiles('conftest.py', 'tools/run_install_ci.py', 'tools/testmon_subprocess_coverage.py', 'tools/testmon_coverage_context.py', 'source/isaaclab/test/install_ci/conftest.py', 'source/isaaclab/test/install_ci/Dockerfile.installci', 'source/isaaclab/test/install_ci/pytest.ini') }}-${{ github.sha }}
+          restore-keys: install-ci-testmon-${{ runner.arch }}-${{ hashFiles('conftest.py', 'tools/run_install_ci.py', 'tools/testmon_subprocess_coverage.py', 'tools/testmon_coverage_context.py', 'source/isaaclab/test/install_ci/conftest.py', 'source/isaaclab/test/install_ci/Dockerfile.installci', 'source/isaaclab/test/install_ci/pytest.ini') }}-
       - name: Show Collected Tests
         uses: ./.github/actions/install-ci-collect
         with:
@@ -160,4 +178,6 @@ jobs:
         uses: ./.github/actions/install-ci-run
         with:
           base-image: ${{ inputs.base_image || 'ubuntu:24.04' }}
+          testmon-data-dir: ${{ github.workspace }}/.testmon/${{ runner.arch }}
+          testmon-mode: ${{ needs.changes.outputs.testmon_mode }}
           test-filter: ${{ inputs.test_filter }}
diff --git a/.gitignore b/.gitignore
index d78a978c60a2..34b836740b17 100644
--- a/.gitignore
+++ b/.gitignore
@@ -19,6 +19,9 @@
 **/*.egg-info/
 **/__pycache__/
 **/.pytest_cache/
+**/.testmon/
+**/.testmondata
+**/.tmontmp/
 **/*.pyc
 **/*.pb
 
diff --git a/conftest.py b/conftest.py
new file mode 100644
index 000000000000..df668e71d427
--- /dev/null
+++ b/conftest.py
@@ -0,0 +1,47 @@
+# Copyright (c) 2022-2026, The Isaac Lab Project Developers (https://github.com/isaac-sim/IsaacLab/blob/main/CONTRIBUTORS.md).
+# All rights reserved.
+#
+# SPDX-License-Identifier: BSD-3-Clause
+
+"""Shared pytest configuration for repository tests.
+
+Wires the Testmon subprocess-coverage hooks (see :mod:`tools.testmon_subprocess_coverage`)
+into the session so that code executed in child Python processes is attributed to the
+active test. The hooks are no-ops unless pytest-testmon is collecting coverage.
+"""
+
+import contextlib
+import sys
+from collections.abc import Generator
+from pathlib import Path
+
+import pytest
+
+
+@pytest.hookimpl(wrapper=True, tryfirst=True)
+def pytest_collection_modifyitems(config: pytest.Config, items: list[pytest.Item]) -> Generator[None, None, None]:
+    """Keep tests marked ``smoke`` selected when Testmon filters the collection."""
+    always_items = [item for item in items if item.get_closest_marker("smoke") is not None]
+    yield
+
+    if config.getoption("testmon_forceselect", default=False):
+        selected = set(items)
+        items.extend(item for item in always_items if item not in selected)
+
+
+_TOOLS_DIR = Path(__file__).resolve().parent / "tools"
+if _TOOLS_DIR.is_dir():
+    if str(_TOOLS_DIR) not in sys.path:
+        sys.path.insert(0, str(_TOOLS_DIR))
+
+    # Guard the import too: when ``tools/`` is absent (partial checkout, artefact-only
+    # CI image) the hooks should stay unregistered no-ops rather than aborting the whole
+    # test collection with a ``ModuleNotFoundError``.
+    with contextlib.suppress(ImportError):
+        from testmon_subprocess_coverage import (  # noqa: F401
+            pytest_runtest_makereport,
+            pytest_runtest_setup,
+            pytest_runtest_teardown,
+            pytest_sessionfinish,
+            pytest_sessionstart,
+        )
diff --git a/source/isaaclab/changelog.d/mataylor-testmon-subprocess-coverage.skip b/source/isaaclab/changelog.d/mataylor-testmon-subprocess-coverage.skip
new file mode 100644
index 000000000000..71f945ce9f49
--- /dev/null
+++ b/source/isaaclab/changelog.d/mataylor-testmon-subprocess-coverage.skip
@@ -0,0 +1,3 @@
+Test/tooling only: add Testmon subprocess coverage tracking so tests that
+spawn child Python processes get reselected when their subprocess-only
+dependencies change.
diff --git a/source/isaaclab/changelog.d/test-selection-rules.skip b/source/isaaclab/changelog.d/test-selection-rules.skip
new file mode 100644
index 000000000000..9f59b1e1f3f3
--- /dev/null
+++ b/source/isaaclab/changelog.d/test-selection-rules.skip
@@ -0,0 +1 @@
+CI and test-selection changes only.
diff --git a/source/isaaclab/isaaclab/utils/array.py b/source/isaaclab/isaaclab/utils/array.py
index d15fbc275dc7..7d514e4ee49e 100644
--- a/source/isaaclab/isaaclab/utils/array.py
+++ b/source/isaaclab/isaaclab/utils/array.py
@@ -3,7 +3,7 @@
 #
 # SPDX-License-Identifier: BSD-3-Clause
 
-"""Sub-module containing utilities for working with different array backends."""
+"""Utilities for working consistently with different array backends."""
 
 # needed to import for allowing type-hinting: torch.device | str | None
 from __future__ import annotations
diff --git a/source/isaaclab/isaaclab/utils/string.py b/source/isaaclab/isaaclab/utils/string.py
index fa83688154d6..dba6104c916f 100644
--- a/source/isaaclab/isaaclab/utils/string.py
+++ b/source/isaaclab/isaaclab/utils/string.py
@@ -3,7 +3,7 @@
 #
 # SPDX-License-Identifier: BSD-3-Clause
 
-"""Sub-module containing utilities for transforming strings and regular expressions."""
+"""Utilities for transforming strings and regular-expression patterns."""
 
 import ast
 import functools
diff --git a/source/isaaclab/test/install_ci/Dockerfile.installci b/source/isaaclab/test/install_ci/Dockerfile.installci
index 68b127df7b34..8178b94621a7 100644
--- a/source/isaaclab/test/install_ci/Dockerfile.installci
+++ b/source/isaaclab/test/install_ci/Dockerfile.installci
@@ -52,7 +52,9 @@ RUN ln -sf /usr/bin/python3 /usr/bin/python
 # Install test runner dependencies into the system Python
 RUN pip install --break-system-packages \
     pytest>=8.0 \
-    pytest-timeout>=2.0
+    "pytest-testmon>=2.2,<3" \
+    pytest-timeout>=2.0 \
+    "coverage>=7.6.1"
 
 # Install uv system-wide so non-root users can invoke it without PATH trickery
 RUN curl -LsSf https://astral.sh/uv/install.sh | UV_INSTALL_DIR=/usr/local/bin sh
diff --git a/source/isaaclab/test/test_testmon_subprocess_coverage.py b/source/isaaclab/test/test_testmon_subprocess_coverage.py
new file mode 100644
index 000000000000..65852d8de04a
--- /dev/null
+++ b/source/isaaclab/test/test_testmon_subprocess_coverage.py
@@ -0,0 +1,151 @@
+# Copyright (c) 2022-2026, The Isaac Lab Project Developers (https://github.com/isaac-sim/IsaacLab/blob/main/CONTRIBUTORS.md).
+# All rights reserved.
+#
+# SPDX-License-Identifier: BSD-3-Clause
+
+"""Regression tests for Testmon subprocess dependency tracking.
+
+Spins up an isolated pytest-in-pytest project whose only link to a helper module
+is a child ``subprocess``. Verifies that :mod:`testmon_subprocess_coverage`
+records the helper as a dependency, so editing it reselects the test.
+"""
+
+from __future__ import annotations
+
+import importlib.util
+import os
+import subprocess
+import sys
+from pathlib import Path
+
+import pytest
+
+
+def _find_tools_dir() -> Path:
+    """Locate the repository ``tools/`` directory that holds the Testmon helpers."""
+    for parent in Path(__file__).resolve().parents:
+        candidate = parent / "tools" / "testmon_subprocess_coverage.py"
+        if candidate.is_file():
+            return candidate.parent
+    raise RuntimeError("could not locate tools/testmon_subprocess_coverage.py")
+
+
+_TOOLS_DIR = _find_tools_dir()
+
+_HELPER_MODULE = "subprocess_only_helper"
+
+# A test whose sole link to the helper is a child ``python -c "..."`` process.
+# The helper is never imported in the pytest process, so only subprocess
+# coverage can register it as a Testmon dependency.
+_TEST_BODY = """\
+import os
+import subprocess
+import sys
+
+
+def test_calls_helper_in_subprocess():
+    # Record that this test actually executed (the harness counts these lines).
+    with open(os.environ["SUBPROC_DEP_RUNS"], "a", encoding="utf-8") as handle:
+        handle.write("run\\n")
+
+    result = subprocess.run(
+        [sys.executable, "-c", "import {module}; assert {module}.contribution() >= 0"],
+        env=os.environ.copy(),
+        capture_output=True,
+        text=True,
+    )
+    assert result.returncode == 0, result.stderr
+"""
+
+_CONFTEST_BODY = """\
+from testmon_subprocess_coverage import (  # noqa: F401
+    pytest_runtest_makereport,
+    pytest_runtest_setup,
+    pytest_runtest_teardown,
+    pytest_sessionfinish,
+    pytest_sessionstart,
+)
+"""
+
+
+def _dependencies_available() -> bool:
+    return all(importlib.util.find_spec(name) is not None for name in ("testmon", "coverage"))
+
+
+def _write_helper(project: Path, value: int) -> None:
+    (project / f"{_HELPER_MODULE}.py").write_text(
+        f"def contribution():\n    return {value}\n",
+        encoding="utf-8",
+    )
+
+
+def _clean_env(project: Path, datafile: Path, runs_file: Path) -> dict[str, str]:
+    """Environment for a nested pytest run, scrubbed of inherited coverage state."""
+    env = os.environ.copy()
+    # Drop any coverage/testmon state leaking in from the outer pytest session so
+    # the child session manages its own coverage lifecycle.
+    for key in ("COVERAGE_PROCESS_START", "COVERAGE_CONTEXT", "COVERAGE_FILE"):
+        env.pop(key, None)
+    env["PYTHONPATH"] = os.pathsep.join([str(_TOOLS_DIR), str(project), env.get("PYTHONPATH", "")]).rstrip(os.pathsep)
+    env["TESTMON_DATAFILE"] = str(datafile)
+    env["SUBPROC_DEP_RUNS"] = str(runs_file)
+    return env
+
+
+def _run_pytest(project: Path, env: dict[str, str], *testmon_args: str) -> subprocess.CompletedProcess[str]:
+    cmd = [
+        sys.executable,
+        "-m",
+        "pytest",
+        "-o",
+        "addopts=",
+        "--testmon",
+        *testmon_args,
+        "-q",
+        str(project),
+    ]
+    return subprocess.run(cmd, cwd=project, env=env, capture_output=True, text=True, timeout=300)
+
+
+def _run_count(runs_file: Path) -> int:
+    if not runs_file.is_file():
+        return 0
+    return len([line for line in runs_file.read_text(encoding="utf-8").splitlines() if line.strip()])
+
+
+@pytest.mark.skipif(not _dependencies_available(), reason="pytest-testmon and coverage are required")
+def test_editing_subprocess_only_dependency_reselects_test(tmp_path: Path) -> None:
+    """Testmon reselects a test when a dependency reached only via a subprocess changes."""
+    project = tmp_path / "proj"
+    project.mkdir()
+    (project / f"test_{_HELPER_MODULE}.py").write_text(_TEST_BODY.format(module=_HELPER_MODULE), encoding="utf-8")
+    (project / "conftest.py").write_text(_CONFTEST_BODY, encoding="utf-8")
+    _write_helper(project, value=1)
+
+    datafile = project / ".testmondata"
+    runs_file = project / "runs.txt"
+    env = _clean_env(project, datafile, runs_file)
+
+    # 1. Prime Testmon: run everything and record dependencies (incl. subprocess).
+    collect = _run_pytest(project, env, "--testmon-noselect")
+    assert collect.returncode == 0, f"collect run failed:\n{collect.stdout}\n{collect.stderr}"
+    assert datafile.is_file(), "Testmon did not create its data file during collection"
+    assert _run_count(runs_file) == 1, f"expected the test to run once during collection:\n{collect.stdout}"
+
+    # 2. Nothing changed -> Testmon must deselect the test (it does not run again).
+    unchanged = _run_pytest(project, env)
+    assert _run_count(runs_file) == 1, (
+        "Testmon reran the test even though nothing changed; deselection is not working.\n"
+        f"{unchanged.stdout}\n{unchanged.stderr}"
+    )
+
+    # 3. Edit the helper that is only reachable through the subprocess.
+    _write_helper(project, value=2)
+
+    # 4. Testmon must notice the subprocess-only dependency changed and reselect.
+    changed = _run_pytest(project, env)
+    assert _run_count(runs_file) == 2, (
+        "Testmon did not reselect the test after its subprocess-only dependency changed; "
+        "subprocess coverage is not being attributed to the test.\n"
+        f"{changed.stdout}\n{changed.stderr}"
+    )
diff --git a/tools/conftest.py b/tools/conftest.py
index 963853194f3d..ea5ff614ca82 100644
--- a/tools/conftest.py
+++ b/tools/conftest.py
@@ -13,7 +13,6 @@
 from dataclasses import dataclass
 
 import pytest
-import tomllib
 from junitparser import Error, JUnitXml, TestCase, TestSuite
 from prettytable import PrettyTable
 
@@ -878,37 +877,9 @@ def _collect_test_files(
     return test_files
 
 
-def _load_test_node_ids_from_toml(workspace_root: str) -> list[str]:
-    """Load exact pytest node IDs from a TOML file configured in the environment."""
-    node_ids_file = os.environ.get("TEST_NODE_IDS_FILE")
-    node_ids_key = os.environ.get("TEST_NODE_IDS_KEY")
-    if not (node_ids_file or node_ids_key):
-        return []
-    if not (node_ids_file and node_ids_key):
-        pytest.exit("Both TEST_NODE_IDS_FILE and TEST_NODE_IDS_KEY must be set together", returncode=1)
-
-    path = node_ids_file if os.path.isabs(node_ids_file) else os.path.join(workspace_root, node_ids_file)
-
-    try:
-        with open(os.path.normpath(path), "rb") as stream:
-            node_ids = tomllib.load(stream).get(node_ids_key)
-    except OSError as exc:
-        pytest.exit(f"Could not read TEST_NODE_IDS_FILE {node_ids_file!r}: {exc}", returncode=1)
-    except tomllib.TOMLDecodeError as exc:
-        pytest.exit(f"{node_ids_file}: invalid TOML: {exc}", returncode=1)
-
-    if not node_ids:
-        pytest.exit(f"{node_ids_key!r} not found or empty in {node_ids_file}", returncode=1)
-    if not isinstance(node_ids, list) or not all(isinstance(node_id, str) for node_id in node_ids):
-        pytest.exit(f"{node_ids_key!r} must be a TOML array of strings in {node_ids_file}", returncode=1)
-
-    return node_ids
-
-
 def _collect_test_node_ids_by_file(workspace_root: str) -> dict[str, list[str]]:
     """Group exact pytest node IDs by absolute test file path."""
     node_ids = [line.strip() for line in os.environ.get("TEST_NODE_IDS", "").splitlines() if line.strip()]
-    node_ids.extend(_load_test_node_ids_from_toml(workspace_root))
     if len(node_ids) != len(set(node_ids)):
         pytest.exit("Configured test node IDs contain duplicates", returncode=1)
 
@@ -989,8 +960,6 @@ def pytest_sessionstart(session):
     print(f"TEST_EXCLUDE_PATTERN env var: '{os.environ.get('TEST_EXCLUDE_PATTERN', 'NOT_SET')}'")
     print(f"TEST_INCLUDE_FILES env var: '{os.environ.get('TEST_INCLUDE_FILES', 'NOT_SET')}'")
     print(f"TEST_NODE_IDS env var: '{'SET' if os.environ.get('TEST_NODE_IDS') else 'NOT_SET'}'")
-    print(f"TEST_NODE_IDS_FILE env var: '{os.environ.get('TEST_NODE_IDS_FILE', 'NOT_SET')}'")
-    print(f"TEST_NODE_IDS_KEY env var: '{os.environ.get('TEST_NODE_IDS_KEY', 'NOT_SET')}'")
     print(f"TEST_QUARANTINED_ONLY env var: '{os.environ.get('TEST_QUARANTINED_ONLY', 'NOT_SET')}'")
     print(f"TEST_CUROBO_ONLY env var: '{os.environ.get('TEST_CUROBO_ONLY', 'NOT_SET')}'")
     print("=" * 50)
diff --git a/tools/run_install_ci.py b/tools/run_install_ci.py
index 5b48dc90ab45..6b67011b70f8 100755
--- a/tools/run_install_ci.py
+++ b/tools/run_install_ci.py
@@ -317,6 +317,25 @@ def _cmd_docker(args: argparse.Namespace) -> int:
     if not args.no_uv_cache:
         docker_run_cmd.extend(["-v", "isaaclab-install-ci-uv-cache:/home/isaaclab/.cache/uv"])
 
+    if args.testmon_data_dir:
+        testmon_data_dir = Path(args.testmon_data_dir).resolve()
+        testmon_data_dir.mkdir(parents=True, exist_ok=True)
+        # The container runs as the non-root 'isaaclab' user (uid 1000). SQLite
+        # opens the database in WAL mode, so it must also write the sibling
+        # ``.testmondata-wal``/``.testmondata-shm`` files restored from the cache.
+        # World-write the directory and every file inside it (not just
+        # ``.testmondata``); otherwise a restored sibling with default 0644
+        # perms makes SQLite report "attempt to write a readonly database".
+        try:
+            testmon_data_dir.chmod(0o777)
+            for entry in testmon_data_dir.iterdir():
+                if entry.is_file():
+                    entry.chmod(0o666)
+        except OSError as exc:
+            print(f"Warning: could not chmod testmon data dir {testmon_data_dir}: {exc}", file=sys.stderr)
+        docker_run_cmd.extend(["-v", f"{testmon_data_dir}:/tmp/testmon"])
+        docker_run_cmd.extend(["-e", "TESTMON_DATAFILE=/tmp/testmon/.testmondata"])
+
     # Pass environment variables
     docker_run_cmd.extend(["-e", "OMNI_KIT_ACCEPT_EULA=Y"])
     docker_run_cmd.extend(["-e", "ACCEPT_EULA=Y"])
@@ -408,6 +427,8 @@ def main() -> int:
   --no-pip-cache       Disable persistent pip cache volume
   --no-uv-cache        Disable persistent uv cache volume
   --results-dir DIR    Host directory for test results (auto-adds --junitxml)
+  --testmon-data-dir DIR
+                       Host directory persisted as the Testmon dependency database
   --wheel PATH         Path to pre-built isaaclab wheel file
   --build-wheel        Build the isaaclab wheel and pass it to tests (mutually exclusive with --wheel)
   --debug              Stream wheel-build output live (default: quiet, only dumped on failure)
@@ -453,6 +474,9 @@ def main() -> int:
     docker_p.add_argument(
         "--results-dir", type=str, default=None, help="Host directory for test results (auto-adds --junitxml)"
     )
+    docker_p.add_argument(
+        "--testmon-data-dir", type=str, default=None, help="Host directory for the Testmon dependency database"
+    )
     docker_p.add_argument("--wheel", type=str, default=None, help="Path to pre-built isaaclab wheel file")
     docker_p.add_argument(
         "--build-wheel",
diff --git a/tools/testmon_coverage_context.py b/tools/testmon_coverage_context.py
new file mode 100644
index 000000000000..1ddc27225360
--- /dev/null
+++ b/tools/testmon_coverage_context.py
@@ -0,0 +1,24 @@
+# Copyright (c) 2022-2026, The Isaac Lab Project Developers (https://github.com/isaac-sim/IsaacLab/blob/main/CONTRIBUTORS.md).
+# All rights reserved.
+#
+# SPDX-License-Identifier: BSD-3-Clause
+
+"""Coverage plugin that tags child-process lines with the active pytest node id."""
+
+from __future__ import annotations
+
+import os
+from types import FrameType
+
+from coverage import CoveragePlugin
+
+
+class NodeIdContextPlugin(CoveragePlugin):
+    """Report the active pytest node id as coverage's dynamic context."""
+
+    def dynamic_context(self, frame: FrameType) -> str | None:
+        return os.environ.get("COVERAGE_CONTEXT") or None
+
+
+def coverage_init(reg, options) -> None:
+    reg.add_dynamic_context(NodeIdContextPlugin())
diff --git a/tools/testmon_subprocess_coverage.py b/tools/testmon_subprocess_coverage.py
new file mode 100644
index 000000000000..0d4c91486b61
--- /dev/null
+++ b/tools/testmon_subprocess_coverage.py
@@ -0,0 +1,266 @@
+# Copyright (c) 2022-2026, The Isaac Lab Project Developers (https://github.com/isaac-sim/IsaacLab/blob/main/CONTRIBUTORS.md).
+# All rights reserved.
+#
+# SPDX-License-Identifier: BSD-3-Clause
+
+"""Testmon subprocess coverage helpers.
+
+pytest-testmon 2.x only tracks coverage in the pytest process. Tests that spawn
+child Python processes (for example ``./isaaclab.sh -p scripts/.../train.py``)
+need:
+
+1. A ``sitecustomize.py`` shim on ``PYTHONPATH`` so child interpreters call
+   :func:`coverage.process_startup` at startup. This is written into a
+   repository-local temporary directory rather than ``site-packages`` so it
+   works even when ``site-packages`` is read-only (for example inside CI
+   containers running as a non-root user).
+2. ``COVERAGE_PROCESS_START`` pointing at a config with ``parallel = true`` and
+   the :mod:`testmon_coverage_context` plugin, so lines are tagged with the
+   active test's node id.
+3. Child data merged into Testmon's in-memory coverage via
+   :meth:`coverage.CoverageData.update` before each batch is read.
+
+Import the pytest hook functions into ``conftest.py``.
+"""
+
+from __future__ import annotations
+
+import os
+import shutil
+import sysconfig
+import warnings
+from dataclasses import dataclass
+from pathlib import Path
+
+import pytest
+
+_TMONTMP_DIR = ".tmontmp"
+_COVERAGE_PROCESS_START = "COVERAGE_PROCESS_START"
+_COVERAGE_CONTEXT = "COVERAGE_CONTEXT"
+_STATE_KEY = pytest.StashKey["SubprocessCoverageState"]()
+
+# ``sitecustomize`` is imported unconditionally by :mod:`site` at interpreter
+# startup (unlike ``usercustomize``, which is gated on ``ENABLE_USER_SITE``), so
+# a ``sitecustomize.py`` placed first on ``PYTHONPATH`` reliably runs in every
+# child interpreter. ``coverage.process_startup`` is a no-op unless
+# ``COVERAGE_PROCESS_START`` is set, so the shim is harmless outside collection.
+_SHIM_FILENAME = "sitecustomize.py"
+_SHIM_CONTENT = (
+    "# Auto-generated by testmon_subprocess_coverage to attribute child-process\n"
+    "# coverage back to the active test. No-op unless COVERAGE_PROCESS_START is set.\n"
+    "try:\n"
+    "    import coverage\n"
+    "    coverage.process_startup()\n"
+    "except Exception:\n"
+    "    pass\n"
+)
+
+
+@dataclass(frozen=True)
+class SubprocessCoverageState:
+    """Session state for subprocess coverage collection."""
+
+    rc_path: Path
+    data_prefix: Path
+    shim_dir: Path | None
+    enabled: bool
+    prev_pythonpath: str | None = None
+
+
+def _python_lib_omit_patterns() -> list[str]:
+    return [os.path.join(value, "*") for key, value in sysconfig.get_paths().items() if key.endswith("lib")]
+
+
+def _is_testmon_collecting(config: pytest.Config) -> bool:
+    tm_conf = getattr(config, "testmon_config", None)
+    return tm_conf is not None and tm_conf.collect
+
+
+def _install_subprocess_shim(shim_dir: Path) -> Path | None:
+    """Write a ``sitecustomize.py`` ``process_startup`` shim into ``shim_dir``.
+
+    Returns the shim directory (to be prepended to ``PYTHONPATH``) or ``None``
+    if :mod:`coverage` is unavailable or the directory cannot be written.
+    """
+    try:
+        import coverage  # noqa: F401
+    except ImportError:
+        return None
+
+    try:
+        shim_dir.mkdir(parents=True, exist_ok=True)
+        (shim_dir / _SHIM_FILENAME).write_text(_SHIM_CONTENT, encoding="utf-8")
+    except OSError:
+        return None
+    return shim_dir
+
+
+def setup_subprocess_coverage(config: pytest.Config) -> SubprocessCoverageState | None:
+    """Configure ``COVERAGE_PROCESS_START`` for the pytest session."""
+    if not _is_testmon_collecting(config):
+        return None
+
+    rootdir = Path(config.rootpath)
+    tmontmp = rootdir / _TMONTMP_DIR
+    tmontmp.mkdir(exist_ok=True)
+
+    shim_dir = _install_subprocess_shim(tmontmp / f"shim-{os.getpid()}")
+    if shim_dir is None:
+        warnings.warn(
+            "testmon subprocess coverage: could not install a process_startup sitecustomize shim, "
+            "so code executed in child Python processes will not be tracked.",
+            stacklevel=1,
+        )
+        state = SubprocessCoverageState(rc_path=Path(), data_prefix=Path(), shim_dir=None, enabled=False)
+        config.stash[_STATE_KEY] = state
+        return state
+
+    # Prepend the shim directory (so child interpreters import our
+    # ``sitecustomize``) and ``tools/`` (so the coveragerc can load
+    # :mod:`testmon_coverage_context`).
+    tools_dir = rootdir / "tools"
+    prev_pythonpath = os.environ.get("PYTHONPATH")
+    pythonpath_entries = [str(shim_dir), str(tools_dir)]
+    if prev_pythonpath:
+        pythonpath_entries.append(prev_pythonpath)
+    os.environ["PYTHONPATH"] = os.pathsep.join(pythonpath_entries)
+
+    data_prefix = tmontmp / f"subprocess-{os.getpid()}"
+    rc_path = tmontmp / f"subprocess-{os.getpid()}.coveragerc"
+    rc_path.write_text(
+        "\n".join(
+            [
+                "[run]",
+                f"data_file = {data_prefix}",
+                "parallel = true",
+                "plugins = testmon_coverage_context",
+                "include =",
+                f"    {os.path.join(str(rootdir), '*')}",
+                "omit =",
+                # The Testmon scratch dir (including our sitecustomize shim) lives
+                # under ``rootdir`` but must not be tracked as a test dependency;
+                # its per-PID path changes every run and would force reselection.
+                f"    {os.path.join(str(tmontmp), '*')}",
+                *(f"    {pattern}" for pattern in _python_lib_omit_patterns()),
+                "",
+            ]
+        ),
+        encoding="utf-8",
+    )
+    os.environ[_COVERAGE_PROCESS_START] = str(rc_path.resolve())
+    state = SubprocessCoverageState(
+        rc_path=rc_path,
+        data_prefix=data_prefix,
+        shim_dir=shim_dir,
+        enabled=True,
+        prev_pythonpath=prev_pythonpath,
+    )
+    config.stash[_STATE_KEY] = state
+    return state
+
+
+def _child_data_files(data_prefix: Path) -> list[Path]:
+    if not data_prefix.parent.is_dir():
+        return []
+    return sorted(p for p in data_prefix.parent.glob(f"{data_prefix.name}.*") if p.is_file())
+
+
+def combine_subprocess_coverage(config: pytest.Config) -> None:
+    """Merge child-process coverage into Testmon's in-memory coverage data."""
+    state = config.stash.get(_STATE_KEY, None)
+    if state is None or not state.enabled:
+        return
+
+    child_files = _child_data_files(state.data_prefix)
+    if not child_files:
+        return
+
+    collect_plugin = config.pluginmanager.get_plugin("TestmonCollect")
+    if collect_plugin is None:
+        return
+
+    # ``collect_plugin.testmon.cov`` is a private chain that could change on a
+    # future testmon release; fall back to ``None`` rather than raising
+    # ``AttributeError`` so a rename simply disables merging instead of breaking
+    # the whole test session.
+    testmon = getattr(collect_plugin, "testmon", None)
+    cov = getattr(testmon, "cov", None)
+    if cov is None:
+        return
+
+    from coverage import CoverageData
+
+    # ``Coverage`` exposes no public "is running" flag, so fall back to assuming
+    # it was running (the normal case while testmon collects) if the private
+    # attribute is unavailable, avoiding an ``AttributeError`` that would
+    # silently disable merging on a future coverage release.
+    was_started = getattr(cov, "_started", True)
+    if was_started:
+        cov.stop()
+    # Always restart coverage in ``finally`` so a merge failure cannot leave it
+    # stopped, which would silently record no dependencies for the rest of the
+    # session.
+    try:
+        target = cov.get_data()
+        for child_file in child_files:
+            child = CoverageData(basename=str(child_file))
+            try:
+                child.read()
+            except Exception:
+                continue
+            try:
+                target.update(child)
+            except Exception:
+                continue
+            child_file.unlink(missing_ok=True)
+    finally:
+        if was_started:
+            cov.start()
+
+
+def teardown_subprocess_coverage(config: pytest.Config) -> None:
+    """Remove temporary subprocess coverage configuration."""
+    state = config.stash.get(_STATE_KEY, None)
+    if state is None:
+        return
+
+    os.environ.pop(_COVERAGE_PROCESS_START, None)
+    os.environ.pop(_COVERAGE_CONTEXT, None)
+    if state.enabled:
+        if state.prev_pythonpath is None:
+            os.environ.pop("PYTHONPATH", None)
+        else:
+            os.environ["PYTHONPATH"] = state.prev_pythonpath
+    if state.enabled and state.rc_path.is_file():
+        state.rc_path.unlink(missing_ok=True)
+    if state.enabled:
+        for leftover in _child_data_files(state.data_prefix):
+            leftover.unlink(missing_ok=True)
+    if state.shim_dir is not None and state.shim_dir.is_dir():
+        shutil.rmtree(state.shim_dir, ignore_errors=True)
+    if _STATE_KEY in config.stash:
+        del config.stash[_STATE_KEY]
+
+
+def pytest_sessionstart(session: pytest.Session) -> None:
+    setup_subprocess_coverage(session.config)
+
+
+def pytest_runtest_setup(item: pytest.Item) -> None:
+    if os.environ.get(_COVERAGE_PROCESS_START):
+        os.environ[_COVERAGE_CONTEXT] = item.nodeid
+
+
+def pytest_runtest_teardown(item: pytest.Item) -> None:
+    os.environ.pop(_COVERAGE_CONTEXT, None)
+
+
+@pytest.hookimpl(tryfirst=True, wrapper=True)
+def pytest_runtest_makereport(item: pytest.Item, call: pytest.CallInfo[None]):
+    if call.when == "teardown":
+        combine_subprocess_coverage(item.config)
+    return (yield)
+
+
+def pytest_sessionfinish(session: pytest.Session, exitstatus: int) -> None:
+    teardown_subprocess_coverage(session.config)