diff --git a/.build/generate-icons-comment.mjs b/.build/generate-icons-comment.mjs
index db7a7ac53..5c26730c9 100644
--- a/.build/generate-icons-comment.mjs
+++ b/.build/generate-icons-comment.mjs
@@ -2,10 +2,12 @@ import { execSync } from 'child_process'
 import { basename, join } from 'path'
 import { ICONS_SRC_DIR, parseMatter } from './helpers.mjs'
 
-// Check icon files added relative to main branch (for PR)
+// Check icon files added relative to base branch (for PR)
 function getAddedIconsFromMain() {
   try {
-    const output = execSync('git diff origin/main...HEAD --name-status', { encoding: 'utf-8' })
+    // Use BASE_SHA or BASE_REF from environment, fallback to origin/main
+    const baseRef = process.env.BASE_SHA || process.env.BASE_REF || 'origin/main'
+    const output = execSync(`git diff ${baseRef}...HEAD --name-status`, { encoding: 'utf-8' })
     const addedIcons = []
 
     output.split('\n').forEach(line => {
@@ -21,7 +23,7 @@ function getAddedIconsFromMain() {
 
     return addedIcons
   } catch (error) {
-    // Fallback: check relative to HEAD if origin/main doesn't exist
+    // Fallback: check relative to HEAD if base ref doesn't exist
     try {
       const output = execSync('git diff --diff-filter=A --name-only', { encoding: 'utf-8' })
       const addedIcons = []
diff --git a/.build/validate-icons.mjs b/.build/validate-icons.mjs
index 3d060ad18..c557f8513 100644
--- a/.build/validate-icons.mjs
+++ b/.build/validate-icons.mjs
@@ -25,7 +25,9 @@ const getIconName = (icon) => {
 
 function getAddedIconsFromMain() {
   try {
-    const output = execSync('git diff origin/main...HEAD --name-status', { encoding: 'utf-8' })
+    // Use BASE_SHA or BASE_REF from environment, fallback to origin/main
+    const baseRef = process.env.BASE_SHA || process.env.BASE_REF || 'origin/main'
+    const output = execSync(`git diff ${baseRef}...HEAD --name-status`, { encoding: 'utf-8' })
     const addedIcons = []
 
     output.split('\n').forEach(line => {
diff --git a/.github/workflows/validate-pr.yml b/.github/workflows/validate-pr.yml
index a802b439e..a471aec76 100644
--- a/.github/workflows/validate-pr.yml
+++ b/.github/workflows/validate-pr.yml
@@ -16,6 +16,16 @@ jobs:
       - uses: actions/checkout@v4
         with:
           fetch-depth: 0
+          ref: ${{ github.event.pull_request.head.sha }}
+      
+      - name: Set base branch
+        run: |
+          BASE_REF="${{ github.event.pull_request.base.ref }}"
+          BASE_SHA="${{ github.event.pull_request.base.sha }}"
+          echo "BASE_REF=${BASE_REF}" >> $GITHUB_ENV
+          echo "BASE_SHA=${BASE_SHA}" >> $GITHUB_ENV
+          # Fetch base branch to ensure it's available
+          git fetch origin ${BASE_REF}:${BASE_REF} || true
 
       - name: Add in progress comment
         id: add-in-progress-comment
@@ -56,6 +66,9 @@ jobs:
 
       - name: Validate icons
         id: validate
+        env:
+          BASE_REF: ${{ env.BASE_REF }}
+          BASE_SHA: ${{ env.BASE_SHA }}
         run: pnpm run --silent validate > ./comment-markup.md
         continue-on-error: true
 
@@ -68,6 +81,9 @@ jobs:
 
       - name: Generate icons comment
         id: generate-icons-comment
+        env:
+          BASE_REF: ${{ env.BASE_REF }}
+          BASE_SHA: ${{ env.BASE_SHA }}
         run: pnpm run --silent generate-icons-comment > ./comment-icons.md || true
         continue-on-error: true