diff --git a/.github/workflows/labeler.yml b/.github/workflows/labeler.yml
index 6ac8f1b69d..09ab98f2ca 100644
--- a/.github/workflows/labeler.yml
+++ b/.github/workflows/labeler.yml
@@ -10,38 +10,12 @@ jobs:
     if: github.event.pull_request.draft == false
     name: Label the PR size
     steps:
-      - uses: mastercactapus/pr-size-labeler@eb6a25f40d6a3327581aca35839b60d419e8019a # https://github.com/CodelyTV/pr-size-labeler/pull/61, updated with latest from main
+      - uses: actions/checkout@v4
         with:
-          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
-          xs_label: 'size/xs'
-          xs_max_size: '15'
-          s_label: 'size/s'
-          s_max_size: '100'
-          m_label: 'size/m'
-          m_max_size: '250'
-          l_label: 'size/l'
-          l_max_size: '500'
-          xl_label: 'size/xl'
-          fail_if_xl: 'true'
-          ignore_deleted: 'true'
-          message_if_xl: >
-            This PR exceeds the recommended size of 500 lines.
-            Please make sure you are NOT addressing multiple issues with one PR.
-            Note this PR might be rejected due to its size.
-          files_to_ignore: |
-            "*.lock"
-            "graphql2/generated.go"
-            "graphql2/maplimit.go"
-            "graphql2/mapconfig.go"
-            "graphql2/models_gen.go"
-            "pkg/sysapi/*.pb.go"
-            "swo/swodb/*.go"
-            "web/src/*.d.ts"
-            "Makefile.binaries.mk"
-            "gadb/*.go"
-            "migrate/schema.sql"
-            "go.mod"
-            "go.sum"
-            ".yarn/releases/*"
-            "devtools/pgdump-lite/pgd/*"
-            "timezone/*.txt"
+          fetch-depth: 0
+      - name: Run labeler script
+        env:
+          GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+          PR_NUMBER: ${{ github.event.number }}
+          FAIL_IF_XL: '1'
+        run: ./devtools/scripts/github-set-pr-label.sh
diff --git a/.labelignore b/.labelignore
new file mode 100644
index 0000000000..27929ea7cf
--- /dev/null
+++ b/.labelignore
@@ -0,0 +1,4 @@
+*.lock
+go.mod
+go.sum
+.yarn/releases/*
diff --git a/devtools/scripts/git-diff-label-calc.sh b/devtools/scripts/git-diff-label-calc.sh
new file mode 100755
index 0000000000..c89d03b5ef
--- /dev/null
+++ b/devtools/scripts/git-diff-label-calc.sh
@@ -0,0 +1,112 @@
+#!/usr/bin/env bash
+set -e
+
+# Outputs a label based on the size of the diff between the current branch and the main branch.
+
+# env setting defaults
+if [ -z "$MAIN_BRANCH" ]; then
+    MAIN_BRANCH=master
+fi
+if [ -z "$FAIL_IF_XL" ]; then
+    FAIL_IF_XL=0
+fi
+
+# const settings
+IGNORE_PATTERN_FILE=.labelignore
+XS_LABEL=size/xs
+XS_MAX=20
+S_LABEL=size/s
+S_MAX=100
+M_LABEL=size/m
+M_MAX=250
+L_LABEL=size/l
+L_MAX=500
+XL_LABEL=size/xl
+
+if [ -z "$DEBUG" ]; then
+    DEBUG=0
+fi
+if [ "$1" = "--debug" ]; then
+    DEBUG=1
+fi
+
+# debug works like echo but only prints when --debug is passed and to stderr
+debug() {
+    if [ $DEBUG -eq 1 ]; then
+        echo "$1" >&2
+    fi
+}
+
+IGNORE_ARGS=()
+
+# Get a list of files including the "generated by" header, then filter them out by only those with DO NOT EDIT on the first line, in case we have code in the repo that does the generation.
+while IFS= read -r file; do
+    # include only files where DO NOT EDIT appears on the very first line
+    if head -n 1 "$file" | grep -q "DO NOT EDIT"; then
+        debug "IGNORE: generated file: $file"
+        IGNORE_ARGS+=(":(exclude)$file")
+    fi
+done < <(git grep -l -e 'generated by .* DO NOT EDIT')
+
+# Read the .labelignore file and add the resolved files to the IGNORE_ARGS array.
+while IFS= read -r pattern; do
+    # Skip empty lines and comments
+    case "$pattern" in
+    '' | \#*) continue ;;
+    esac
+
+    # Use git ls-files with the pattern
+    while IFS= read -r file; do
+        debug "IGNORE: pattern '$pattern': $file"
+        IGNORE_ARGS+=(":(exclude)$file")
+    done < <(git ls-files "$pattern")
+done < <(cat "$IGNORE_PATTERN_FILE" 2>/dev/null)
+
+# Perform diff for merging to the main branch:
+# --ignore-blank-lines: ignore changes that only involve blank lines
+# --numstat: output only the number of changes (per file)
+# -w: ignore whitespace
+# --diff-filter=d: exclude deleted files
+# --minimal: produce the smallest diff possible
+# --merge-base: find the common ancestor of the current branch and the main branch
+# $IGNORE_ARGS[@]: list of `:(exclude)file` patterns to ignore
+OUTPUT=$(
+    if [ "$DEBUG" = "1" ]; then set -x; fi
+    git diff --ignore-blank-lines --numstat -w --diff-filter=d --minimal --merge-base "origin/$MAIN_BRANCH" -- "${IGNORE_ARGS[@]}"
+)
+
+debug
+debug "DIFF FILE STATS"
+debug "==============="
+debug "$OUTPUT"
+debug
+
+sum=$(
+    echo "$OUTPUT" | awk '{ total += $1 + $2 } END { print total }'
+)
+
+debug "TOTAL: $sum"
+
+LABEL=""
+if [ $sum -le $XS_MAX ]; then
+    LABEL=$XS_LABEL
+elif [ $sum -le $S_MAX ]; then
+    LABEL=$S_LABEL
+elif [ $sum -le $M_MAX ]; then
+    LABEL=$M_LABEL
+elif [ $sum -le $L_MAX ]; then
+    LABEL=$L_LABEL
+else
+    LABEL=$XL_LABEL
+fi
+
+debug "LABEL: $LABEL"
+
+if [ $FAIL_IF_XL -eq 1 ] && [ "$LABEL" = "$XL_LABEL" ]; then
+    echo ""
+    echo "ERROR: This PR exceeds the maximum size of $L_MAX lines."
+    echo "Please make sure you are NOT addressing multiple issues with one PR."
+    exit 1
+fi
+
+echo "$LABEL"
diff --git a/devtools/scripts/github-set-pr-label.sh b/devtools/scripts/github-set-pr-label.sh
new file mode 100755
index 0000000000..7c1f1c3249
--- /dev/null
+++ b/devtools/scripts/github-set-pr-label.sh
@@ -0,0 +1,19 @@
+#!/usr/bin/env bash
+set -e
+
+if [ -z "PR_NUMBER" ]; then
+    echo "PR_NUMBER is not set"
+    exit 1
+fi
+
+LABEL=$(./devtools/scripts/git-diff-label-calc.sh --debug)
+
+# Remove any existing test/* labels
+for label in $(gh pr view "$PR_NUMBER" --json labels --jq '.labels[] | select(.name | startswith("size/")) | .name'); do
+    if [ "$label" == "$LABEL" ]; then
+        continue # Skip the label we want to add
+    fi
+    gh pr edit "$PR_NUMBER" --remove-label "$label"
+done
+
+gh pr edit "$PR_NUMBER" --add-label "$LABEL"