diff --git a/.github/workflows/client-versions.yaml b/.github/workflows/client-versions.yaml
index 05be514b..f19d4553 100644
--- a/.github/workflows/client-versions.yaml
+++ b/.github/workflows/client-versions.yaml
@@ -4,6 +4,10 @@ on:
   workflow_dispatch:
   workflow_call:
 
+# Least-privilege default: this report only reads the repo to census notebooks.
+permissions:
+  contents: read
+
 jobs:
   analyze-client-versions:
     runs-on: ubuntu-latest
diff --git a/.github/workflows/pr.yaml b/.github/workflows/pr.yaml
index 43efd238..6d24e578 100644
--- a/.github/workflows/pr.yaml
+++ b/.github/workflows/pr.yaml
@@ -6,6 +6,10 @@ on:
     branches:
       - main
 
+# Least-privilege default: lint and notebook tests only read the repo.
+permissions:
+  contents: read
+
 jobs:
   lint:
     uses: './.github/workflows/lint.yaml'
diff --git a/.github/workflows/test-notebooks-all.yaml b/.github/workflows/test-notebooks-all.yaml
index 1ea2ded8..2ec2c192 100644
--- a/.github/workflows/test-notebooks-all.yaml
+++ b/.github/workflows/test-notebooks-all.yaml
@@ -9,6 +9,10 @@ on:
         default: 'docs'
         type: string
 
+# Least-privilege default: notebook validation and execution only read the repo.
+permissions:
+  contents: read
+
 jobs:
   validate-notebooks:
     runs-on: ubuntu-latest
diff --git a/.github/workflows/test-notebooks-changed.yaml b/.github/workflows/test-notebooks-changed.yaml
index 68e1bdef..6355ce09 100644
--- a/.github/workflows/test-notebooks-changed.yaml
+++ b/.github/workflows/test-notebooks-changed.yaml
@@ -8,6 +8,10 @@ on:
         type: string
         default: 'main'
 
+# Least-privilege default: change detection and notebook execution only read the repo.
+permissions:
+  contents: read
+
 jobs:
   validate-notebooks:
     runs-on: ubuntu-latest