diff --git a/.github/workflows/llgo-binary-size-pages.yml b/.github/workflows/llgo-binary-size-pages.yml
index 5acc5a0..a5ad057 100644
--- a/.github/workflows/llgo-binary-size-pages.yml
+++ b/.github/workflows/llgo-binary-size-pages.yml
@@ -15,6 +15,9 @@ permissions:
   contents: write
 
 concurrency:
+  # This must not share a group with the benchmark workflow: GitHub keeps only
+  # one pending run per group, so a page-only update could otherwise cancel a
+  # waiting binary-size build.
   group: llgo-binary-size-pages
   cancel-in-progress: false
 
diff --git a/.github/workflows/llgo-binary-size.yml b/.github/workflows/llgo-binary-size.yml
index 8450d51..0a180ce 100644
--- a/.github/workflows/llgo-binary-size.yml
+++ b/.github/workflows/llgo-binary-size.yml
@@ -30,16 +30,22 @@ on:
         type: string
 
 permissions:
-  contents: write
-  actions: write
+  contents: read
+  actions: read
 
 concurrency:
-  group: llgo-binary-size-pages
+  # Keep benchmark builds in their own queue. The Pages-only workflow has a
+  # separate queue; sharing one group would let a newer pending Pages run
+  # replace a pending binary-size run even with cancel-in-progress disabled.
+  group: llgo-binary-size-build
   cancel-in-progress: false
 
 jobs:
   update-pin:
     if: github.event_name == 'repository_dispatch'
+    permissions:
+      contents: write
+      actions: write
     runs-on: ubuntu-24.04
     steps:
       - uses: actions/checkout@v4
@@ -87,8 +93,40 @@ jobs:
             "https://api.github.com/repos/${GITHUB_REPOSITORY}/actions/workflows/llgo-binary-size.yml/dispatches" \
             --data "$payload"
 
+  pr-scope:
+    if: github.event_name == 'pull_request'
+    permissions:
+      contents: read
+    runs-on: ubuntu-24.04
+    outputs:
+      version_changed: ${{ steps.changed.outputs.version_changed }}
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
+
+      - name: Detect a committed LLGo version change
+        id: changed
+        env:
+          BASE_SHA: ${{ github.event.pull_request.base.sha }}
+          PR_SHA: ${{ github.event.pull_request.head.sha }}
+        run: |
+          set -euo pipefail
+          if git diff --name-only "$BASE_SHA" "$PR_SHA" | grep -Fxq 'ci/llgo-size/llgo-version.env'; then
+            echo 'version_changed=true' >> "$GITHUB_OUTPUT"
+            echo 'The PR changes the committed LLGo version; the full matrix will run.'
+          else
+            echo 'version_changed=false' >> "$GITHUB_OUTPUT"
+            echo 'The PR does not change the committed LLGo version; only Go validation will run.'
+          fi
+
   binary-size:
-    if: github.event_name != 'repository_dispatch'
+    if: >-
+      always() && github.event_name != 'repository_dispatch' &&
+      (github.event_name != 'pull_request' || needs.pr-scope.outputs.version_changed == 'true')
+    needs: pr-scope
+    permissions:
+      contents: write
     runs-on: ubuntu-24.04
     timeout-minutes: 120
     steps:
@@ -209,7 +247,7 @@ jobs:
           if-no-files-found: error
 
       - name: Publish binary-size history to Pages
-        if: github.event_name != 'pull_request' && github.ref == 'refs/heads/main'
+        if: github.ref == 'refs/heads/main'
         env:
           PAGES_TOKEN: ${{ secrets.GITHUB_TOKEN }}
         run: |
@@ -223,7 +261,7 @@ jobs:
             "$pages_dir" \
             ci/llgo-size/site
   deploy-pages:
-    if: github.event_name != 'pull_request' && github.ref == 'refs/heads/main'
+    if: github.ref == 'refs/heads/main' && github.event_name != 'pull_request'
     needs: binary-size
     runs-on: ubuntu-24.04
     permissions:
@@ -253,3 +291,42 @@ jobs:
       - name: Deploy GitHub Pages
         id: deployment
         uses: actions/deploy-pages@v4
+
+  pr-validation:
+    if: >-
+      always() && github.event_name == 'pull_request' &&
+      needs.pr-scope.result == 'success' && needs.pr-scope.outputs.version_changed != 'true'
+    needs: pr-scope
+    permissions:
+      contents: read
+    runs-on: ubuntu-24.04
+    timeout-minutes: 30
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Read the PR validation Go version
+        run: |
+          set -euo pipefail
+          source ci/llgo-size/llgo-version.env
+          mkdir -p .ci
+          printf '%s\n' "$GO_VERSION" > .ci/go-version
+
+      - uses: actions/setup-go@v5
+        with:
+          go-version-file: .ci/go-version
+
+      - name: Run the LLGo-size benchmark cases with Go
+        env:
+          BENT_BUILD_WORKERS: 4
+        run: |
+          set -euo pipefail
+          go build -o .ci/bent ./cmd/bent
+          mkdir -p .ci/bent-pr
+          (
+            cd .ci/bent-pr
+            "$GITHUB_WORKSPACE/.ci/bent" -I
+            "$GITHUB_WORKSPACE/.ci/bent" -v \
+              -B=benchmarks-llgo-size.toml \
+              -C=configurations-llgo-size.toml \
+              -c=Go -j="$BENT_BUILD_WORKERS"
+          )
diff --git a/ci/llgo-size/README.md b/ci/llgo-size/README.md
index 0ab7b76..322f2ee 100644
--- a/ci/llgo-size/README.md
+++ b/ci/llgo-size/README.md
@@ -49,14 +49,26 @@ The workflow keeps Bent's native benchsize files, the existing Markdown summary,
 For pushes to `main`, LLGo merge dispatches, and manual runs from `main`, the
 workflow copies the structured result into the pages branch. The static page at
 the Pages root lists all published runs and lets you compare any two runs by
-benchmark and configuration. Pull requests still build and upload an artifact
-but do not modify the history.
+benchmark and configuration. Pull requests use the lightweight Go-only
+validation job described below; they do not produce a binary-size artifact or
+modify the history.
 
 Changes that only touch the dashboard source or its publication scripts use the
 separate `llgo-binary-size-pages.yml` workflow. That path publishes the updated
 site directly without rebuilding benchmarks, and its publication jobs are
 restricted to `main`; pull-request builds cannot publish Pages.
 
+The benchmark and page-only workflows use separate concurrency queues. A page
+refresh can therefore wait independently without replacing a pending
+binary-size run.
+
+Pull requests are split by whether they change `llgo-version.env`. A normal PR
+uses a separate Go-only validation job: dependency acquisition, compilation,
+and execution are checked without building LLGo or the four LLGo binary-size
+variants. A PR that changes the committed LLGo version runs the full five-way
+matrix and uploads the `llgo-binary-size` artifact for review, but still does
+not publish history.
+
 ### First-time repository setup
 
 The first publisher run creates the `pages` branch automatically. Before that
diff --git a/docs/llgo-binary-size-handoff.md b/docs/llgo-binary-size-handoff.md
index ab1499a..253d30a 100644
--- a/docs/llgo-binary-size-handoff.md
+++ b/docs/llgo-binary-size-handoff.md
@@ -37,7 +37,10 @@
 
 只修改仪表盘源码或页面发布脚本时，不进入二进制大小构建；独立的
 `llgo-binary-size-pages.yml` 会直接刷新 `pages` 分支并部署站点。该工作流和
-主工作流的发布 job 都限制在 `main`，PR 构建只验证和上传 artifact，不会发布。
+主工作流的发布 job 都限制在 `main`。普通 PR 只运行 Go 配置的用例校验；如果
+PR 修改 `llgo-version.env`，则运行完整的 LLGo 二进制大小矩阵并上传 artifact
+供开发者参考，但两种 PR 都不会发布 Pages。
+两个工作流使用独立的并发队列，页面刷新不会淘汰等待中的二进制大小构建。
 
 核心文件：