diff --git a/.github/workflows/check-line-endings.yml b/.github/workflows/check-line-endings.yml
index 793aaa803..3e7040c0c 100644
--- a/.github/workflows/check-line-endings.yml
+++ b/.github/workflows/check-line-endings.yml
@@ -13,7 +13,7 @@ jobs:
   check-line-endings:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@f43a0e5ff2bd294095638e18286ca9a3d1956744 # v3.6.0
 
       - name: Check for CRLF line endings in markdown files
         run: |
diff --git a/.github/workflows/check-plugin-structure.yml b/.github/workflows/check-plugin-structure.yml
index e71b3503d..86bab0be6 100644
--- a/.github/workflows/check-plugin-structure.yml
+++ b/.github/workflows/check-plugin-structure.yml
@@ -15,10 +15,10 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout
-        uses: actions/checkout@v4
+        uses: actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5 # v4.3.1
 
       - name: Check for materialized files in plugin directories
-        uses: actions/github-script@v7
+        uses: actions/github-script@f28e40c7f34bde8b3046d885e986cb6290c5673b # v7.1.0
         with:
           script: |
             const { execSync } = require('child_process');
diff --git a/.github/workflows/check-pr-target.yml b/.github/workflows/check-pr-target.yml
index 38c178e7e..d0e5834cd 100644
--- a/.github/workflows/check-pr-target.yml
+++ b/.github/workflows/check-pr-target.yml
@@ -13,7 +13,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Reject PR targeting main
-        uses: actions/github-script@v7
+        uses: actions/github-script@f28e40c7f34bde8b3046d885e986cb6290c5673b # v7.1.0
         with:
           script: |
             const body = [
diff --git a/.github/workflows/codespell.yml b/.github/workflows/codespell.yml
index 57a89fa90..5c5dae06e 100644
--- a/.github/workflows/codespell.yml
+++ b/.github/workflows/codespell.yml
@@ -13,10 +13,10 @@ jobs:
   codespell:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5 # v4.3.1
       
       - name: Check spelling with codespell
-        uses: codespell-project/actions-codespell@v2
+        uses: codespell-project/actions-codespell@406322ec52dd7b488e48c1c4b82e2a8b3a1bf630 # v2.1
         with:
           check_filenames: true
           check_hidden: false
diff --git a/.github/workflows/contributors.yml b/.github/workflows/contributors.yml
index 7588b8b6e..21913a64d 100644
--- a/.github/workflows/contributors.yml
+++ b/.github/workflows/contributors.yml
@@ -14,7 +14,7 @@ jobs:
       pull-requests: write
     steps:
       - name: Checkout
-        uses: actions/checkout@v6
+        uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
         with:
           fetch-depth: 0
 
@@ -25,7 +25,7 @@ jobs:
           echo "version=${NODE_VERSION}" >> "$GITHUB_OUTPUT"
 
       - name: Setup Node.js
-        uses: actions/setup-node@v6
+        uses: actions/setup-node@53b83947a5a98c8d113130e565377fae1a50d02f # v6.3.0
         with:
           node-version: ${{ steps.node-version.outputs.version }}
 
@@ -71,7 +71,7 @@ jobs:
 
       - name: Create Pull Request
         if: steps.verify-changed-files.outputs.changed == 'true'
-        uses: peter-evans/create-pull-request@v7
+        uses: peter-evans/create-pull-request@22a9089034f40e5a961c8808d113e2c98fb63676 # v7.0.11
         with:
           token: ${{ secrets.GITHUB_TOKEN }}
           commit-message: "docs: update contributors"
diff --git a/.github/workflows/copilot-setup-steps.yml b/.github/workflows/copilot-setup-steps.yml
index d5d988a3f..11f7144da 100644
--- a/.github/workflows/copilot-setup-steps.yml
+++ b/.github/workflows/copilot-setup-steps.yml
@@ -19,7 +19,7 @@ jobs:
 
     steps:
       - name: Checkout repository
-        uses: actions/checkout@v6
+        uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
       - name: Install gh-aw extension
         uses: github/gh-aw/actions/setup-cli@32b3a711a9ee97d38e3989c90af0385aff0066a7 # v0.57.2
         with:
diff --git a/.github/workflows/deploy-website.yml b/.github/workflows/deploy-website.yml
index 35210e7fc..0289addbf 100644
--- a/.github/workflows/deploy-website.yml
+++ b/.github/workflows/deploy-website.yml
@@ -25,12 +25,12 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout
-        uses: actions/checkout@v4
+        uses: actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5 # v4.3.1
         with:
           fetch-depth: 0  # Full history needed for git-based last updated dates
 
       - name: Setup Node.js
-        uses: actions/setup-node@v4
+        uses: actions/setup-node@49933ea5288caeca8642d1e84afbd3f7d6820020 # v4.4.0
         with:
           node-version: "20"
           cache: "npm"
@@ -50,10 +50,10 @@ jobs:
         working-directory: ./website
 
       - name: Setup Pages
-        uses: actions/configure-pages@v5
+        uses: actions/configure-pages@983d7736d9b0ae728b81ab479565c72886d7745b # v5.0.0
 
       - name: Upload artifact
-        uses: actions/upload-pages-artifact@v3
+        uses: actions/upload-pages-artifact@56afc609e74202658d3ffba0e8f6dda462b719fa # v3.0.1
         with:
           path: "./website/dist"
 
@@ -67,4 +67,4 @@ jobs:
     steps:
       - name: Deploy to GitHub Pages
         id: deployment
-        uses: actions/deploy-pages@v4
+        uses: actions/deploy-pages@d6db90164ac5ed86f2b6aed7e0febac5b3c0c03e # v4.0.5
diff --git a/.github/workflows/publish.yml b/.github/workflows/publish.yml
index ec288decb..32a538091 100644
--- a/.github/workflows/publish.yml
+++ b/.github/workflows/publish.yml
@@ -17,7 +17,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout staged branch
-        uses: actions/checkout@v4
+        uses: actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5 # v4.3.1
         with:
           ref: staged
           fetch-depth: 0
@@ -29,7 +29,7 @@ jobs:
           echo "version=${NODE_VERSION}" >> "$GITHUB_OUTPUT"
 
       - name: Setup Node.js
-        uses: actions/setup-node@v4
+        uses: actions/setup-node@49933ea5288caeca8642d1e84afbd3f7d6820020 # v4.4.0
         with:
           node-version: ${{ steps.node-version.outputs.version }}
 
diff --git a/.github/workflows/validate-agentic-workflows-pr.yml b/.github/workflows/validate-agentic-workflows-pr.yml
index 625b8b0dd..5f90db8ab 100644
--- a/.github/workflows/validate-agentic-workflows-pr.yml
+++ b/.github/workflows/validate-agentic-workflows-pr.yml
@@ -17,7 +17,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout code
-        uses: actions/checkout@v4
+        uses: actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5 # v4.3.1
         with:
           fetch-depth: 0
 
@@ -49,7 +49,7 @@ jobs:
 
       - name: Comment on PR
         if: failure()
-        uses: marocchino/sticky-pull-request-comment@v2
+        uses: marocchino/sticky-pull-request-comment@773744901bac0e8cbb5a0dc842800d45e9b2b405 # v2.9.4
         with:
           header: workflow-forbidden-files
           message: |
@@ -74,10 +74,10 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout code
-        uses: actions/checkout@v4
+        uses: actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5 # v4.3.1
 
       - name: Install gh-aw CLI
-        uses: github/gh-aw/actions/setup-cli@main
+        uses: github/gh-aw/actions/setup-cli@f7437f4f94c2bc86e7e6eca0f374e303e98bd66c # v0.61.1
 
       - name: Compile workflow files
         id: compile
@@ -111,7 +111,7 @@ jobs:
 
       - name: Comment on PR if compilation failed
         if: failure()
-        uses: marocchino/sticky-pull-request-comment@v2
+        uses: marocchino/sticky-pull-request-comment@773744901bac0e8cbb5a0dc842800d45e9b2b405 # v2.9.4
         with:
           header: workflow-validation
           message: |
diff --git a/.github/workflows/validate-readme.yml b/.github/workflows/validate-readme.yml
index e9ae9dfee..f3f81cb4d 100644
--- a/.github/workflows/validate-readme.yml
+++ b/.github/workflows/validate-readme.yml
@@ -23,12 +23,12 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout code
-        uses: actions/checkout@v4
+        uses: actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5 # v4.3.1
         with:
           fetch-depth: 0
 
       - name: Setup Node.js
-        uses: actions/setup-node@v4
+        uses: actions/setup-node@49933ea5288caeca8642d1e84afbd3f7d6820020 # v4.4.0
         with:
           node-version: "20"
 
@@ -66,7 +66,7 @@ jobs:
 
       - name: Comment on PR if files need updating
         if: steps.check-diff.outputs.status == 'failure' && github.event.pull_request.head.repo.permissions.push == true
-        uses: marocchino/sticky-pull-request-comment@v2
+        uses: marocchino/sticky-pull-request-comment@773744901bac0e8cbb5a0dc842800d45e9b2b405 # v2.9.4
         with:
           header: readme-validation
           message: |
diff --git a/agents/github-actions-expert.agent.md b/agents/github-actions-expert.agent.md
index 943867476..9ad33d993 100644
--- a/agents/github-actions-expert.agent.md
+++ b/agents/github-actions-expert.agent.md
@@ -41,10 +41,12 @@ Before creating or modifying workflows:
 - Grant minimal necessary permissions
 
 **Action Pinning**:
-- Pin to specific versions for stability
-- Use major version tags (`@v4`) for balance of security and maintenance
-- Consider full commit SHA for maximum security (requires more maintenance)
-- Never use `@main` or `@latest`
+- Always pin actions to a full-length commit SHA for maximum security and immutability (e.g., `actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5 # v4.3.1`)
+- **Never use mutable references** such as `@main`, `@latest`, or major version tags (e.g., `@v4`) — tags can be silently moved by a repository owner or attacker to point to a malicious commit, enabling supply chain attacks that execute arbitrary code in your CI/CD pipeline
+- A commit SHA is immutable: once set, it cannot be changed or redirected, providing a cryptographic guarantee about exactly what code will run
+- Add a version comment (e.g., `# v4.3.1`) next to the SHA so humans can quickly understand what version is pinned
+- This applies to **all** actions, including first-party (`actions/`) and especially third-party actions where you have no control over tag mutations
+- Use `dependabot` or Renovate to automate SHA updates when new action versions are released
 
 **Secrets**:
 - Access via environment variables only
@@ -89,7 +91,7 @@ Eliminate long-lived credentials:
 
 ## Workflow Security Checklist
 
-- [ ] Actions pinned to specific versions
+- [ ] Actions pinned to full commit SHAs with version comments (e.g., `uses: actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5 # v4.3.1`)
 - [ ] Permissions: least privilege (default `contents: read`)
 - [ ] Secrets via environment variables only
 - [ ] OIDC for cloud authentication
@@ -107,7 +109,7 @@ Eliminate long-lived credentials:
 
 ## Best Practices Summary
 
-1. Pin actions to specific versions
+1. Pin actions to full commit SHAs with version comments (e.g., `@<sha> # vX.Y.Z`) — never use mutable tags or branches
 2. Use least privilege permissions
 3. Never log secrets
 4. Prefer OIDC for cloud access
diff --git a/agents/se-gitops-ci-specialist.agent.md b/agents/se-gitops-ci-specialist.agent.md
index 338a3c0ca..520618637 100644
--- a/agents/se-gitops-ci-specialist.agent.md
+++ b/agents/se-gitops-ci-specialist.agent.md
@@ -59,7 +59,7 @@ Build reliable CI/CD pipelines, debug deployment failures quickly, and ensure ev
 18.16.0
 
 # CI config (.github/workflows/deploy.yml)
-- uses: actions/setup-node@v3
+- uses: actions/setup-node@3235b876344d2a9aa001b8d1453c930bba69e610 # v3.9.1
   with:
     node-version-file: '.node-version'
 ```
@@ -112,7 +112,7 @@ main:
   run: npm audit --audit-level=high
 
 - name: Secret scanning
-  uses: trufflesecurity/trufflehog@main
+  uses: trufflesecurity/trufflehog@6c05c4a00b91aa542267d8e32a8254774799d68d # v3.93.8
 ```
 
 ## Step 4: Debugging Methodology
@@ -209,7 +209,7 @@ jobs:
   test:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@f43a0e5ff2bd294095638e18286ca9a3d1956744 # v3.6.0
       - run: npm ci
       - run: npm test
 
diff --git a/instructions/github-actions-ci-cd-best-practices.instructions.md b/instructions/github-actions-ci-cd-best-practices.instructions.md
index 68a0224f7..d3e006833 100644
--- a/instructions/github-actions-ci-cd-best-practices.instructions.md
+++ b/instructions/github-actions-ci-cd-best-practices.instructions.md
@@ -47,9 +47,9 @@ jobs:
       artifact_path: ${{ steps.package_app.outputs.path }}
     steps:
       - name: Checkout code
-        uses: actions/checkout@v4
+        uses: actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5 # v4.3.1
       - name: Setup Node.js
-        uses: actions/setup-node@v3
+        uses: actions/setup-node@3235b876344d2a9aa001b8d1453c930bba69e610 # v3.9.1
         with:
           node-version: 18
       - name: Install dependencies and build
@@ -62,7 +62,7 @@ jobs:
           zip -r dist.zip dist
           echo "path=dist.zip" >> "$GITHUB_OUTPUT"
       - name: Upload build artifact
-        uses: actions/upload-artifact@v3
+        uses: actions/upload-artifact@bbbca2ddaa5d8feaa63e36b76fdaad77386f024f # v7.0.0
         with:
           name: my-app-build
           path: dist.zip
@@ -74,7 +74,7 @@ jobs:
     environment: staging
     steps:
       - name: Download build artifact
-        uses: actions/download-artifact@v3
+        uses: actions/download-artifact@3e5f45b2cfb9172054b4087a40e8e0b5a5461e7c # v8.0.1
         with:
           name: my-app-build
       - name: Deploy to Staging
@@ -87,17 +87,17 @@ jobs:
 ### **3. Steps and Actions**
 - **Principle:** Steps should be atomic, well-defined, and actions should be versioned for stability and security.
 - **Deeper Dive:**
-    - **`uses`:** Referencing marketplace actions (e.g., `actions/checkout@v4`, `actions/setup-node@v3`) or custom actions. Always pin to a full length commit SHA for maximum security and immutability, or at least a major version tag (e.g., `@v4`). Avoid pinning to `main` or `latest`.
+    - **`uses`:** Referencing marketplace actions (e.g., `actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2`) or custom actions. Always pin to a full-length commit SHA for maximum security and immutability. Tags and branches are mutable references — a malicious actor who gains write access to an action's repository can silently move a tag (e.g., `@v4`) to a compromised commit, executing arbitrary code in your workflow (a supply chain attack). A commit SHA is immutable and cannot be redirected. Add the version as a comment (e.g., `# v4.3.1`) for human readability. Avoid mutable references like `@main`, `@latest`, or major version tags (e.g., `@v4`).
     - **`name`:** Essential for clear logging and debugging. Make step names descriptive.
     - **`run`:** For executing shell commands. Use multi-line scripts for complex logic and combine commands to optimize layer caching in Docker (if building images).
     - **`env`:** Define environment variables at the step or job level. Do not hardcode sensitive data here.
     - **`with`:** Provide inputs to actions. Ensure all required inputs are present.
 - **Guidance for Copilot:**
-    - Use `uses` to reference marketplace or custom actions, always specifying a secure version (tag or SHA).
+    - Use `uses` to reference marketplace or custom actions, always pinning to an immutable commit SHA with a human-readable version comment (e.g., `uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2`). This is especially critical for third-party actions where you have no control over whether a tag gets moved.
     - Use `name` for each step for readability in logs and easier debugging.
     - Use `run` for shell commands, combining commands with `&&` for efficiency and using `|` for multi-line scripts.
     - Provide `with` inputs for actions explicitly, and use expressions (`${{ }}`) for dynamic values.
-- **Security Note:** Audit marketplace actions before use. Prefer actions from trusted sources (e.g., `actions/` organization) and review their source code if possible. Use `dependabot` for action version updates.
+- **Security Note:** Audit marketplace actions before use. Prefer actions from trusted sources (e.g., `actions/` organization) and review their source code if possible. Use `dependabot` for action version updates. **Never use mutable tag or branch references** (`@v4`, `@main`, `@latest`) — these are vulnerable to supply chain attacks where a compromised tag can execute malicious code in your CI/CD pipeline.
 
 ## Security Best Practices in GitHub Actions
 
@@ -136,7 +136,7 @@ jobs:
     - **Federated Identity:** This is a key pattern for modern, secure cloud deployments.
 - **Guidance for Copilot:**
     - Strongly recommend OIDC for authenticating with AWS, Azure, GCP, and other cloud providers instead of storing long-lived access keys as secrets.
-    - Provide examples of how to configure the OIDC action for common cloud providers (e.g., `aws-actions/configure-aws-credentials@v4`).
+    - Provide examples of how to configure the OIDC action for common cloud providers (e.g., `aws-actions/configure-aws-credentials@<SHA> # v4.x.x`). Always pin to a full commit SHA.
     - Explain the concept of trust policies and how they relate to OIDC setup.
 - **Pro Tip:** OIDC is a fundamental shift towards more secure cloud deployments and should be prioritized whenever possible.
 
@@ -162,7 +162,7 @@ jobs:
     permissions:
       contents: read # This job only needs to read code, override workflow default
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5 # v4.3.1
       - run: npm run lint
 ```
 
@@ -219,13 +219,13 @@ jobs:
     - **Restore Keys:** Use `restore-keys` for fallbacks to older, compatible caches.
     - **Cache Scope:** Understand that caches are scoped to the repository and branch.
 - **Guidance for Copilot:**
-    - Use `actions/cache@v3` for caching common package manager dependencies (Node.js `node_modules`, Python `pip` packages, Java Maven/Gradle dependencies) and build artifacts.
+    - Use `actions/cache` (pinned to a full commit SHA) for caching common package manager dependencies (Node.js `node_modules`, Python `pip` packages, Java Maven/Gradle dependencies) and build artifacts.
     - Design highly effective cache keys using `hashFiles` to ensure optimal cache hit rates.
     - Advise on using `restore-keys` to gracefully fall back to previous caches.
 - **Example (Advanced Caching for Monorepo):**
 ```yaml
 - name: Cache Node.js modules
-  uses: actions/cache@v3
+  uses: actions/cache@668228422ae6a00e4ad889ee87cd7109ec5666a7 # v5.0.4
   with:
     path: |
       ~/.npm
@@ -259,8 +259,8 @@ jobs:
         node-version: [16.x, 18.x, 20.x]
         browser: [chromium, firefox]
     steps:
-      - uses: actions/checkout@v4
-      - uses: actions/setup-node@v3
+      - uses: actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5 # v4.3.1
+      - uses: actions/setup-node@3235b876344d2a9aa001b8d1453c930bba69e610 # v3.9.1
         with:
           node-version: ${{ matrix.node-version }}
       - name: Install Playwright browsers
@@ -289,7 +289,7 @@ jobs:
     - **`lfs`:** Manage Git LFS (Large File Storage) files efficiently. If not needed, set `lfs: false`.
     - **Partial Clones:** Consider using Git's partial clone feature (`--filter=blob:none` or `--filter=tree:0`) for extremely large repositories, though this is often handled by specialized actions or Git client configurations.
 - **Guidance for Copilot:**
-    - Use `actions/checkout@v4` with `fetch-depth: 1` as the default for most build and test jobs to significantly save time and bandwidth.
+    - Use `actions/checkout` (pinned to a full commit SHA, e.g., `actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5 # v4.3.1`) with `fetch-depth: 1` as the default for most build and test jobs to significantly save time and bandwidth.
     - Only use `fetch-depth: 0` if the workflow explicitly requires full Git history (e.g., for release tagging, deep commit analysis, or `git blame` operations).
     - Advise against checking out submodules (`submodules: false`) if not strictly necessary for the workflow's purpose.
     - Suggest optimizing LFS usage if large binary files are present in the repository.
@@ -303,7 +303,7 @@ jobs:
     - **Use Cases:** Build outputs (executables, compiled code, Docker images), test reports (JUnit XML, HTML reports), code coverage reports, security scan results, generated documentation, static website builds.
     - **Limitations:** Artifacts are immutable once uploaded. Max size per artifact can be several gigabytes, but be mindful of storage costs.
 - **Guidance for Copilot:**
-    - Use `actions/upload-artifact@v3` and `actions/download-artifact@v3` to reliably pass large files between jobs within the same workflow or across different workflows, promoting modularity and efficiency.
+    - Use `actions/upload-artifact` and `actions/download-artifact` (both pinned to full commit SHAs) to reliably pass large files between jobs within the same workflow or across different workflows, promoting modularity and efficiency.
     - Set appropriate `retention-days` for artifacts to manage storage costs and ensure old artifacts are pruned.
     - Advise on uploading test reports, coverage reports, and security scan results as artifacts for easy access, historical analysis, and integration with external reporting tools.
     - Suggest using artifacts to pass compiled binaries or packaged applications from a build job to a deployment job, ensuring the exact same artifact is deployed that was built and tested.
@@ -452,7 +452,7 @@ This checklist provides a granular set of criteria for reviewing GitHub Actions
     - Are `needs` dependencies correctly defined between jobs to ensure proper execution order?
     - Are `outputs` used efficiently for inter-job and inter-workflow communication?
     - Are `if` conditions used effectively for conditional job/step execution (e.g., environment-specific deployments, branch-specific actions)?
-    - Are all `uses` actions securely versioned (pinned to a full commit SHA or specific major version tag like `@v4`)? Avoid `main` or `latest` tags.
+    - Are all `uses` actions pinned to a full commit SHA with a human-readable version comment (e.g., `actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5 # v4.3.1`)? Tags (e.g., `@v4`) and branches (e.g., `@main`) are mutable and can be silently redirected to malicious commits — always use immutable SHA references, especially for third-party actions.
     - Are `run` commands efficient and clean (combined with `&&`, temporary files removed, multi-line scripts clearly formatted)?
     - Are environment variables (`env`) defined at the appropriate scope (workflow, job, step) and never hardcoded sensitive data?
     - Is `timeout-minutes` set for long-running jobs to prevent hung workflows?