diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 9da72bc..073f7ad 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -9,6 +9,11 @@ on:
     paths-ignore:
       - '*.md'
 
+permissions:
+  contents: read # for checkout repository
+  actions: read # for fetching base branch bundle stats
+  pull-requests: write # for comments
+
 jobs:
   build:
     runs-on: ubuntu-latest
@@ -34,6 +39,10 @@ jobs:
           else
             echo 'clean'
           fi
+      - name: Analyze esbuild bundle size
+        uses: exoego/esbuild-bundle-analyzer@main
+        with:
+          metafiles: "tmp/meta.json"
       - uses: actions/upload-artifact@v4
         with:
           name: dist
diff --git a/.gitignore b/.gitignore
index a162f73..e16cd14 100644
--- a/.gitignore
+++ b/.gitignore
@@ -3,6 +3,7 @@
 node_modules
 out
 .analyzer
+tmp/meta.json
 
 # Allow-list
 !__tests__/__fixtures__/examples-with-base/**/.analyzer/base/bundle/bundle_analysis.json
diff --git a/esbuild.mjs b/esbuild.mjs
index cfa019c..4eced02 100644
--- a/esbuild.mjs
+++ b/esbuild.mjs
@@ -1,5 +1,5 @@
 import * as esbuild from 'esbuild'
-import { readFileSync } from 'node:fs'
+import { readFileSync, writeFileSync } from 'node:fs'
 
 // https://github.com/evanw/esbuild/issues/1685#issuecomment-944916409
 const excludeNodeModulesFromSourceMap = {
@@ -18,7 +18,7 @@ const excludeNodeModulesFromSourceMap = {
   },
 };
 
-await esbuild.build({
+const result = await esbuild.build({
   entryPoints: [`./src/index.ts`],
   outfile: `dist/index.mjs`,
   format: 'esm',
@@ -30,3 +30,5 @@ await esbuild.build({
   bundle: true,
   plugins: [excludeNodeModulesFromSourceMap]
 })
+
+writeFileSync(`tmp/meta.json`, JSON.stringify(result.metafile, null, 2));
diff --git a/tmp/.gitkeep b/tmp/.gitkeep
new file mode 100644
index 0000000..e69de29