diff --git a/.github/workflows/lint-workflows.yml b/.github/workflows/lint-workflows.yml
new file mode 100644
index 00000000..9f356256
--- /dev/null
+++ b/.github/workflows/lint-workflows.yml
@@ -0,0 +1,82 @@
+name: Workflow lint
+
+# START OF COMMON SECTION
+on:
+  push:
+    branches: [ 'master', 'main', 'release/**' ]
+  pull_request:
+    branches: [ '**' ]
+    types: [opened, synchronize, reopened, ready_for_review]
+    paths:
+      - '.github/workflows/**'
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+# END OF COMMON SECTION
+
+permissions:
+  contents: read
+
+jobs:
+  reusable-concurrency:
+    if: github.event_name != 'pull_request' || github.event.pull_request.draft == false
+    name: Reusable workflows must not self-cancel
+    runs-on: ubuntu-22.04
+    timeout-minutes: 5
+    steps:
+      - name: Checkout wolfProvider
+        uses: actions/checkout@v4
+
+      - name: Install PyYAML
+        run: pip install --quiet pyyaml
+
+      - name: Check concurrency in reusable workflows
+        run: |
+          python3 - <<'EOF'
+          import glob, sys, yaml
+
+          paths = sorted(glob.glob('.github/workflows/*.yml')
+                         + glob.glob('.github/workflows/*.yaml'))
+          bad = []
+          for path in paths:
+              try:
+                  with open(path) as f:
+                      wf = yaml.safe_load(f)
+              except yaml.YAMLError as e:
+                  print(f'{path}: unparsable: {e}')
+                  sys.exit(1)
+              if not isinstance(wf, dict):
+                  continue
+              # YAML 1.1 parses a bare `on:` key as the boolean True.
+              triggers = wf.get('on', wf.get(True)) or {}
+              # `on:` is legal as a mapping, a list, or a bare string.
+              if isinstance(triggers, str):
+                  names = {triggers}
+              elif isinstance(triggers, list):
+                  names = set(triggers)
+              elif isinstance(triggers, dict):
+                  names = set(triggers)
+              else:
+                  names = set()
+              if 'workflow_call' not in names:
+                  continue
+              conc = wf.get('concurrency') or {}
+              if not isinstance(conc, dict):
+                  continue
+              # Anything not literally false counts: "true"/${{ }} still cancel.
+              cip = conc.get('cancel-in-progress', False)
+              if cip is not False and str(cip).strip().lower() != 'false':
+                  bad.append(f"{path}: cancel-in-progress={cip!r} "
+                             f"group={conc.get('group')!r}")
+
+          if bad:
+              print('Reusable workflow sets cancel-in-progress to something other')
+              print('than false. github.workflow resolves to the CALLER, so sibling')
+              print('calls in one run share a group and cancel each other. Set')
+              print('cancel-in-progress: false, or drop the concurrency block.')
+              for b in bad:
+                  print('  ' + b)
+              sys.exit(1)
+          print('ok: no reusable workflow sets cancel-in-progress')
+          EOF
diff --git a/.github/workflows/nightly-multi-compiler.yml b/.github/workflows/nightly-multi-compiler.yml
index afcc3024..0552f1ef 100644
--- a/.github/workflows/nightly-multi-compiler.yml
+++ b/.github/workflows/nightly-multi-compiler.yml
@@ -12,9 +12,7 @@ on:
   workflow_call: {}
   workflow_dispatch: {}
 
-concurrency:
-  group: ${{ github.workflow }}-${{ github.ref }}
-  cancel-in-progress: true
+# No concurrency group: github.workflow is the caller's here, so any group collides with sibling calls.
 
 jobs:
   build_wolfprovider:
diff --git a/.github/workflows/perf-regression.yml b/.github/workflows/perf-regression.yml
index d218585e..2f44c0e2 100644
--- a/.github/workflows/perf-regression.yml
+++ b/.github/workflows/perf-regression.yml
@@ -6,9 +6,7 @@ on:
   workflow_dispatch:
   workflow_call:
 
-concurrency:
-  group: ${{ github.workflow }}-${{ github.ref }}
-  cancel-in-progress: true
+# No concurrency group: github.workflow is the caller's here, so any group collides with sibling calls.
 
 jobs:
   discover_versions:
diff --git a/.github/workflows/pr-osp-retry.yml b/.github/workflows/pr-osp-retry.yml
new file mode 100644
index 00000000..08ba84f4
--- /dev/null
+++ b/.github/workflows/pr-osp-retry.yml
@@ -0,0 +1,55 @@
+name: PR OSP retry
+
+# No concurrency group: workflow_run reports github.ref as the default branch, so any group self-cancels.
+
+on:
+  workflow_run:
+    workflows: ["PR OSP (label-selected)"]
+    types: [completed]
+
+permissions:
+  actions: write
+
+jobs:
+  retry:
+    name: Rerun failed jobs once
+    runs-on: ubuntu-latest
+    timeout-minutes: 5
+    # 'failure' skips superseded runs (those land as 'cancelled'); attempt 1 bounds this to one retry.
+    if: >
+      github.event.workflow_run.conclusion == 'failure' &&
+      github.event.workflow_run.run_attempt == 1
+    steps:
+      - name: Verify trigger is trusted
+        env:
+          GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+          REPO: ${{ github.repository }}
+          ACTOR: ${{ github.event.workflow_run.actor.login }}
+          WF_PATH: ${{ github.event.workflow_run.path }}
+        run: |
+          # A fork controls both the workflow name and a new file's path, so pin the path.
+          if [ "$WF_PATH" != ".github/workflows/pr-osp-select.yml" ]; then
+            echo "::error::untrusted triggering workflow: $WF_PATH"
+            exit 1
+          fi
+          # Distinguish "not a collaborator" (404) from an API failure; never conflate them.
+          if ! body=$(gh api "/repos/$REPO/collaborators/$ACTOR/permission" 2>&1); then
+            case "$body" in
+              *"Not Found"*) echo "::error::actor $ACTOR is not a collaborator"; exit 1 ;;
+              *) echo "::error::could not verify $ACTOR: $body"; exit 1 ;;
+            esac
+          fi
+          perm=$(printf '%s' "$body" | jq -r '.permission')
+          # triage can add labels, so it can legitimately start a PR OSP run.
+          case "$perm" in
+            admin|write|maintain|triage) echo "actor $ACTOR ok ($perm)" ;;
+            *) echo "::error::actor $ACTOR cannot label ($perm)"; exit 1 ;;
+          esac
+
+      - name: Rerun failed jobs
+        env:
+          GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+          RUN_ID: ${{ github.event.workflow_run.id }}
+        run: |
+          gh api -X POST \
+            "/repos/${{ github.repository }}/actions/runs/$RUN_ID/rerun-failed-jobs"