diff --git a/.github/CONTRIBUTING.md b/.github/CONTRIBUTING.md
index 021c674d08..a716b2f648 100644
--- a/.github/CONTRIBUTING.md
+++ b/.github/CONTRIBUTING.md
@@ -82,7 +82,7 @@ See [`?test`](https://rdatatable.gitlab.io/data.table/reference/test.html).
 
 #### Performance testing
 
-If your PR may have an effect on time/memory usage, please consider adding a performance test, either in the same PR, or a follow-up PR. Note that first-time contributors _must_ do so in a follow-up PR, since the tests are only run on PRs from branches created directly in the Rdatatable/data.table repo. See the [Performance testing](https://github.com/Rdatatable/data.table/wiki/Performance-testing) wiki page for details.
+If your PR may have an effect on time/memory usage, please consider adding a performance test, either in the same PR, or a follow-up PR. On PRs opened from a fork, the `atime` results and comparison plots will be published to the GitHub Actions job summary (and downloadable artifact) rather than posted as a PR comment. See the [Performance testing](https://github.com/Rdatatable/data.table/wiki/Performance-testing) wiki page for details.
 
 Minimal first time PR
 ---------------------
diff --git a/.github/workflows/performance-tests.yml b/.github/workflows/performance-tests.yml
index 7c76af6981..8b3204f6fc 100644
--- a/.github/workflows/performance-tests.yml
+++ b/.github/workflows/performance-tests.yml
@@ -2,140 +2,111 @@ name: atime performance tests
 
 on:
   pull_request:
-    types:
-      - opened
-      - reopened
-      - synchronize
     paths:
       - 'R/**'
       - 'src/**'
       - '.ci/atime/**'
       - '.github/workflows/performance-tests.yml'
 
+concurrency:
+  group: ${{ github.workflow }}-${{ github.event.pull_request.number || github.run_id }}
+  cancel-in-progress: true
+
+permissions:
+  contents: read
+  pull-requests: write
+
 jobs:
   comment:
     runs-on: ubuntu-latest
     steps:
-    - name: Start timer
-      run: echo "START_SETUP_TIME=$(date +%s)" >> $GITHUB_ENV
-      shell: bash
-    - name: Checkout
-      uses: actions/checkout@v6
-      with:
-        fetch-depth: 0
-    - name: Retrieve branch references, necessary for perf testing past versions
-      shell: bash
-      run: |
-        git switch "${GITHUB_BASE_REF}"
-        git switch "${GITHUB_HEAD_REF}"
-    - uses: actions/setup-node@v6
-      name: setup-node https://github.com/actions/setup-node?tab=readme-ov-file#usage
-    - name: Safe directory exception
-      run: |
-        git config --global --add safe.directory '*'
-      shell: bash
-    - name: Setup
-      uses: eddelbuettel/github-actions/r-ci@master
-    - name: Dependencies
-      run: ./run.sh install_all
-    - name: Adjust compilation flags for old data.table versions
-      run: sudo sed -i 's|-Werror=format-security||' `Rscript -e 'writeLines(R.home("etc"))'`/Makeconf
-    - name: Install and run atime
-      run: |
-        echo "options(repos = c(CRAN = 'https://cloud.r-project.org'))" >> .Rprofile
-        Rscript -e 'install.packages(c("atime", "ggplot2", "directlabels"))'
-        echo "END_SETUP_START_TESTS_TIME=$(date +%s)" >> $GITHUB_ENV
-        Rscript -e 'atime::atime_pkg(Sys.getenv("GITHUB_WORKSPACE"), tests.dir = ".ci");'
-        echo "END_TESTS_TIME=$(date +%s)" >> $GITHUB_ENV
-      shell: bash
-    - name: Upload artifact
-      id: artifact-upload-step
-      uses: actions/upload-artifact@v4
-      with:
-        name: atime-results
-        path: .ci/atime/
-    - name: comments.json
-      if: ${{ github.event_name == 'pull_request' }}
-      env:
-        PR_NUMBER: ${{ github.event.number }}
-        TAG: atime
-      shell: bash
-      run: |
-        curl --no-progress-meter -L -H "Accept: application/vnd.github+json" -H "X-GitHub-Api-Version: 2026-03-10" https://api.github.com/repos/$GITHUB_REPOSITORY/issues/$PR_NUMBER/comments > comments.json
-        cat comments.json
-        echo > comment-number.txt
-        echo "<!-- automatic comment for $TAG -->" > comment.md
-        cat comment.md
-    - name: comment-number.txt
-      if: ${{ github.event_name == 'pull_request' }}
-      shell: node {0}
-      run: |
-        fs = require('fs');
-        tag = fs.readFileSync('comment.md', 'utf-8');
-        console.log(tag);
-        content = fs.readFileSync('comments.json', 'utf-8').replaceAll("\r", "");
-        console.log(content);
-        prc = JSON.parse(content);
-        flist = prc.filter((o) => { return o.body.startsWith(tag); });
-        console.log(flist);
-        if(flist.length == 0) process.exit(0);
-        comment_id = flist[0].id;
-        console.log(comment_id);
-        fs.writeFileSync('comment-number.txt', comment_id+"");
-    - name: add images
-      shell: bash
-      run: |
-        uploadImage() {
-          local png=$1
-          curl -F "file=@$png" -F "visibility=unlisted" https://picrd.com/api/upload | sed 's/.*image_url":"//' | sed 's/",".*//'
-        }
-        cat comment-number.txt
-        PREVIEW_URL=$(uploadImage .ci/atime/tests_preview_facet.png)
-        ALL_URL=$(uploadImage .ci/atime/tests_all_facet.png)
-        echo $PREVIEW_URL $ALL_URL
-        cat .ci/atime/HEAD_issues.md >> comment.md
-        echo -e "\n[![Comparison Plot]($PREVIEW_URL)]($ALL_URL)" >> comment.md
-        echo -e "\nGenerated via commit ${{ github.event.pull_request.head.sha }}" >> comment.md
-        echo -e "\nDownload link for the artifact containing the test results: [↓ atime-results.zip](${{ github.server_url }}/${{ github.repository }}/actions/runs/${{ github.run_id }}/artifacts/${{ steps.artifact-upload-step.outputs.artifact-id }})" >> comment.md
-    - name: add content to comment.md
-      run: |
-        R_SETUP_DURATION=$((END_SETUP_START_TESTS_TIME - START_SETUP_TIME))
-        VERSION_SETUP_DURATION=$(cut -d '.' -f 1 ./.ci/atime/install_seconds.txt)
-        ATIME_TESTS_DURATION=$((END_TESTS_TIME - END_SETUP_START_TESTS_TIME - VERSION_SETUP_DURATION))
-        formatTime() {
+      - name: Start timer
+        shell: bash
+        run: echo "START_SETUP_TIME=$(date +%s)" >> "$GITHUB_ENV"
+
+      - name: Checkout
+        uses: actions/checkout@v7
+        with:
+          fetch-depth: 0
+
+      - name: Retrieve branch references, necessary for perf testing past versions
+        shell: bash
+        run: |
+          git branch -f "${GITHUB_BASE_REF}" "origin/${GITHUB_BASE_REF}"
+          HEAD_BRANCH="${GITHUB_HEAD_REF}"
+          if [ "$HEAD_BRANCH" = "$GITHUB_BASE_REF" ]; then
+            HEAD_BRANCH="pr-${{ github.event.number }}"
+          fi
+          git switch -C "$HEAD_BRANCH"
+
+      - uses: r-lib/actions/setup-r@v2
+        with:
+          use-public-rspm: true
+
+      - uses: r-lib/actions/setup-r-dependencies@v2
+        with:
+          cache-version: ${{ hashFiles('.ci/atime/tests.R') }}
+          extra-packages: cran::data.table, any::atime, any::ggplot2, any::directlabels
+
+      - name: Run atime
+        shell: bash
+        run: |
+          echo "END_SETUP_START_TESTS_TIME=$(date +%s)" >> "$GITHUB_ENV"
+          Rscript -e 'atime::atime_pkg(Sys.getenv("GITHUB_WORKSPACE"), tests.dir = ".ci")'
+          echo "END_TESTS_TIME=$(date +%s)" >> "$GITHUB_ENV"
+
+      - name: Upload artifact
+        id: artifact-upload-step
+        uses: actions/upload-artifact@v7
+        with:
+          name: atime-results
+          path: .ci/atime/
+
+      - name: Post or update PR comment
+        env:
+          GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+          PR_NUMBER: ${{ github.event.number }}
+        shell: bash
+        run: |
+          uploadImage() {
+            curl --fail --retry 3 -sS -F "file=@$1" -F "visibility=unlisted" https://picrd.com/api/upload | jq -r '.image_url'
+          }
+          PREVIEW_URL=$(uploadImage .ci/atime/tests_preview_facet.png)
+          ALL_URL=$(uploadImage .ci/atime/tests_all_facet.png)
+
+          R_SETUP_DURATION=$((END_SETUP_START_TESTS_TIME - START_SETUP_TIME))
+          VERSION_SETUP_DURATION=$(cut -d '.' -f 1 ./.ci/atime/install_seconds.txt)
+          ATIME_TESTS_DURATION=$((END_TESTS_TIME - END_SETUP_START_TESTS_TIME - VERSION_SETUP_DURATION))
+          formatTime() {
             local totalSeconds=$1
-            if [ $totalSeconds -lt 0 ]; then
-                echo "Time calculation error: negative duration"
-                return
-            fi
-            if [ $totalSeconds -lt 60 ]; then
-                echo "${totalSeconds} seconds"
+            if [ "$totalSeconds" -lt 0 ]; then
+              echo "Time calculation error: negative duration"
+            elif [ "$totalSeconds" -lt 60 ]; then
+              echo "${totalSeconds} seconds"
             else
-                local minutes=$((totalSeconds / 60))
-                local seconds=$((totalSeconds % 60))
-                echo "${minutes} minutes and ${seconds} seconds"
+              echo "$((totalSeconds / 60)) minutes and $((totalSeconds % 60)) seconds"
             fi
-        }
-        echo -e "\n| Task | Duration |" >> comment.md
-        echo -e "|---|---|" >> comment.md
-        echo -e "| R setup and installing dependencies   | $(formatTime $R_SETUP_DURATION)       |" >> comment.md
-        echo -e "| Installing different package versions | $(formatTime $VERSION_SETUP_DURATION) |" >> comment.md
-        echo -e "| Running and plotting the test cases   | $(formatTime $ATIME_TESTS_DURATION)   |" >> comment.md
-    - name: convert comment to json https://stackoverflow.com/questions/1251999/how-can-i-replace-each-newline-n-with-a-space-using-sed/1252191#1252191 then post
-      if: ${{ github.event_name == 'pull_request' }}
-      env:
-        PR_COMMENT_TOKEN: ${{ secrets.GITHUB_TOKEN }}
-        PR_NUMBER: ${{ github.event.number }}
-      shell: bash
-      run: |
-        ISSUES_API=https://api.github.com/repos/$GITHUB_REPOSITORY/issues
-        PR_API=$ISSUES_API/$PR_NUMBER/comments
-        VERSION=2026-03-10
-        ACCEPT=application/vnd.github+json
-        COMMENT_NUMBER=$(cat comment-number.txt)
-        if [ "$COMMENT_NUMBER" == "" ]; then CMD=$PR_API; else CMD=$ISSUES_API/comments/$COMMENT_NUMBER; fi; echo $CMD
-        cat comment.md
-        MD=$(sed 's/"/\\"/g' comment.md | sed ':a;N;$!ba;s/\n/\\n/g')
-        echo '{"body":"'$MD'"}' > pr-comment.json
-        cat pr-comment.json
-        curl --no-progress-meter -L -H "Accept: $ACCEPT" -H "X-GitHub-Api-Version: $VERSION" -X POST -H "Authorization: Bearer $PR_COMMENT_TOKEN" $CMD -d "@pr-comment.json"
+          }
+
+          ARTIFACT_URL="${{ github.server_url }}/${{ github.repository }}/actions/runs/${{ github.run_id }}/artifacts/${{ steps.artifact-upload-step.outputs.artifact-id }}"
+          cat <<EOF > comment.md
+          $(cat .ci/atime/HEAD_issues.md)
+
+          [![Comparison Plot]($PREVIEW_URL)]($ALL_URL)
+
+          Generated via commit ${{ github.event.pull_request.head.sha }}
+
+          Download link for the artifact containing the test results: [↓ atime-results.zip]($ARTIFACT_URL)
+
+          | Task | Duration |
+          |---|---|
+          | R setup and installing dependencies | $(formatTime "$R_SETUP_DURATION") |
+          | Installing different package versions | $(formatTime "$VERSION_SETUP_DURATION") |
+          | Running and plotting the test cases | $(formatTime "$ATIME_TESTS_DURATION") |
+          EOF
+
+          cat comment.md >> "$GITHUB_STEP_SUMMARY"
+
+          if [ "${{ github.event.pull_request.head.repo.full_name }}" = "$GITHUB_REPOSITORY" ]; then
+            gh pr comment "$PR_NUMBER" --edit-last --create-if-none -F comment.md
+          fi