diff --git a/.github/workflows/guix-nix-policy.yml b/.github/workflows/guix-nix-policy.yml
index b8e4d6f..09494bf 100644
--- a/.github/workflows/guix-nix-policy.yml
+++ b/.github/workflows/guix-nix-policy.yml
@@ -1,6 +1,15 @@
 # SPDX-License-Identifier: MPL-2.0
 name: Guix/Nix Package Policy
-on: [push, pull_request]
+on:
+  push:
+    branches: [main]
+  pull_request:
+
+# Estate guardrail: scope push to default branches (PR fires once, not
+# push+PR) and cancel superseded runs. Safe — read-only PR check.
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
 jobs:
   check:
     runs-on: ubuntu-latest
diff --git a/.github/workflows/npm-bun-blocker.yml b/.github/workflows/npm-bun-blocker.yml
index bf8d109..a166d11 100644
--- a/.github/workflows/npm-bun-blocker.yml
+++ b/.github/workflows/npm-bun-blocker.yml
@@ -1,6 +1,15 @@
 # SPDX-License-Identifier: MPL-2.0
 name: NPM/Bun Blocker
-on: [push, pull_request]
+on:
+  push:
+    branches: [main]
+  pull_request:
+
+# Estate guardrail: scope push to default branches (PR fires once, not
+# push+PR) and cancel superseded runs. Safe — read-only PR check.
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
 
 jobs:
   check:
diff --git a/.github/workflows/ts-blocker.yml b/.github/workflows/ts-blocker.yml
index 2fdb2c7..80c1ee0 100644
--- a/.github/workflows/ts-blocker.yml
+++ b/.github/workflows/ts-blocker.yml
@@ -1,5 +1,14 @@
 # SPDX-License-Identifier: MPL-2.0
-on: [push, pull_request]
+on:
+  push:
+    branches: [main]
+  pull_request:
+
+# Estate guardrail: scope push to default branches (PR fires once, not
+# push+PR) and cancel superseded runs. Safe — read-only PR check.
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
 
 jobs:
   check: