From d82cda1f5000b6e83b3de2aed4992843f07791e6 Mon Sep 17 00:00:00 2001
From: Maarten Zuidhoorn <maarten@zuidhoorn.com>
Date: Wed, 17 Dec 2025 13:56:54 +0100
Subject: [PATCH 01/10] Add action to validate changelog diffs after merging

---
 .../check-merge-queue-changelogs/action.yml   | 77 +++++++++++++++
 .../check-changelog-diff.cjs                  | 94 +++++++++++++++++++
 .github/workflows/lint-build-test.yml         | 15 +++
 3 files changed, 186 insertions(+)
 create mode 100644 .github/actions/check-merge-queue-changelogs/action.yml
 create mode 100644 .github/actions/check-merge-queue-changelogs/check-changelog-diff.cjs

diff --git a/.github/actions/check-merge-queue-changelogs/action.yml b/.github/actions/check-merge-queue-changelogs/action.yml
new file mode 100644
index 00000000000..4bd2a027dcc
--- /dev/null
+++ b/.github/actions/check-merge-queue-changelogs/action.yml
@@ -0,0 +1,77 @@
+name: Check merge queue changelogs
+description: Check if the changelog was incorrectly merged in a merge queue
+  pull request.
+
+inputs:
+  head-ref:
+    description: The head ref of the pull request.
+    required: true
+  base-ref:
+    description: The base ref to compare against.
+    required: true
+  github-token:
+    description: The GitHub token to use for authentication.
+    required: true
+
+runs:
+  using: composite
+  steps:
+    - name: Checkout repository
+      uses: MetaMask/action-checkout-and-setup@v2
+      with:
+        is-high-risk-environment: false
+        fetch-depth: 0
+
+    - name: Get pull request number
+      id: pr-number
+      uses: actions/github-script@v8
+      env:
+        HEAD_REF: ${{ inputs.head-ref }}
+      with:
+        github-token: ${{ inputs.github-token }}
+        script: |
+          const { HEAD_REF } = process.env;
+          const match = HEAD_REF.match(/\/pr-([0-9]+)-/u);
+          if (!match) {
+            return core.setFailed(`Could not extract pull request number from head ref: "${HEAD_REF}".`);
+          }
+
+          const number = parseInt(match[1], 10);
+          core.setOutput('pr-number', number);
+
+    - name: Get pull request branch
+      id: pr-branch
+      shell: bash
+      env:
+        REPOSITORY: ${{ github.repository }}
+        PR_NUMBER: ${{ steps.pr-number.outputs.pr-number }}
+      run: |
+        BRANCH=$(gh api "/repos/${REPOSITORY}/pulls/${PR_NUMBER} --jq=.head.ref")
+        echo "pr-branch=$BRANCH" >> "$GITHUB_OUTPUT"
+
+    - name: Check changelog changes
+      id: changelog-check
+      shell: bash
+      env:
+        REF: ${{ inputs.ref }}
+        BASE_REF: ${{ inputs.base-ref }}
+        PR_BRANCH: ${{ steps.pr-branch.outputs.pr-branch }}
+        REPOSITORY: ${{ github.repository }}
+        ACTION_PATH: ${{ github.action_path }}
+      run: |
+        set -euo pipefail
+
+        UPDATED_CHANGELOGS=$(git diff origin/"$BASE_REF"...origin/"$PR_BRANCH" --name-only | grep -E 'CHANGELOG\.md$' || true)
+        if [ -n "$UPDATED_CHANGELOGS" ]; then
+          for FILE in $UPDATED_CHANGELOGS; do
+            git show origin/"$BASE_REF":"$FILE" > /tmp/base-changelog.md
+            git show origin/"$PR_BRANCH":"$FILE" > /tmp/pr-changelog.md
+
+            node "${ACTION_PATH}/check-changelog-diff.cjs" \
+              /tmp/base-changelog.md \
+              /tmp/pr-changelog.md \
+              "$FILE"
+          done
+        else
+          echo "No CHANGELOG.md files were modified in this PR."
+        fi
diff --git a/.github/actions/check-merge-queue-changelogs/check-changelog-diff.cjs b/.github/actions/check-merge-queue-changelogs/check-changelog-diff.cjs
new file mode 100644
index 00000000000..d220ea30390
--- /dev/null
+++ b/.github/actions/check-merge-queue-changelogs/check-changelog-diff.cjs
@@ -0,0 +1,94 @@
+// This script checks that any new changelog entries added in a PR
+// remain in the [Unreleased] section after the PR is merged.
+
+const fs = require('fs');
+
+if (process.argv.length < 5) {
+  console.error(
+    'Usage: tsx check-changelog-diff.mts <base-file> <pr-file> <merged-file>',
+  );
+
+  // eslint-disable-next-line n/no-process-exit
+  process.exit(1);
+}
+
+/* eslint-disable n/no-sync */
+const baseContent = fs.readFileSync(process.argv[2], 'utf8');
+const prContent = fs.readFileSync(process.argv[3], 'utf8');
+const mergedContent = fs.readFileSync(process.argv[4], 'utf8');
+/* eslint-enable n/no-sync */
+
+/**
+ * Extract the "[Unreleased]" section from the changelog content.
+ *
+ * This doesn't actually parse the Markdown, it just looks for the section
+ * header and collects lines until the next section header.
+ *
+ * @param {string} content - The changelog content.
+ * @returns {Set<string>} The lines in the "[Unreleased]" section as a
+ * {@link Set}.
+ */
+function getUnreleasedSection(content) {
+  const lines = content.split('\n');
+
+  let inUnreleased = false;
+  const sectionLines = new Set();
+
+  for (const line of lines) {
+    // Find unreleased header.
+    if (line.trim().match(/^##\s+\[Unreleased\]/u)) {
+      inUnreleased = true;
+      continue;
+    }
+
+    // Stop if we hit the next version header (## [x.x.x]).
+    if (inUnreleased && line.trim().match(/^##\s+\[/u)) {
+      break;
+    }
+
+    // If inside the unreleased header, add lines to the set.
+    if (inUnreleased) {
+      sectionLines.add(line.trim());
+    }
+  }
+
+  return sectionLines;
+}
+
+/**
+ * Get the lines that were added in the PR content compared to the base content.
+ *
+ * @param {string} oldContent - The base changelog content.
+ * @param {string} newContent - The PR changelog content.
+ * @returns {string[]} The added lines as an array of strings.
+ */
+function getAddedLines(oldContent, newContent) {
+  const oldLines = new Set(oldContent.split('\n').map((line) => line.trim()));
+  const newLines = newContent.split('\n').map((line) => line.trim());
+
+  return newLines.filter(
+    (line) =>
+      line.length > 0 &&
+      !oldLines.has(line) &&
+      !line.startsWith('#') &&
+      !line.startsWith('['),
+  );
+}
+
+const mergedUnreleased = getUnreleasedSection(mergedContent);
+const addedLines = getAddedLines(baseContent, prContent);
+
+const missingLines = [];
+for (const line of addedLines) {
+  if (!mergedUnreleased.has(line)) {
+    missingLines.push(line);
+  }
+}
+
+if (missingLines.length > 0) {
+  console.error(
+    `The following lines added in the PR are missing from the "Unreleased" section after merge:\n\n- ${missingLines.join('\n- ')}\n\nPlease update your pull request and ensure that new changelog entries remain in the "Unreleased" section.`,
+  );
+
+  process.exitCode = 1;
+}
diff --git a/.github/workflows/lint-build-test.yml b/.github/workflows/lint-build-test.yml
index 70ac9fe5cb7..e7e83888aef 100644
--- a/.github/workflows/lint-build-test.yml
+++ b/.github/workflows/lint-build-test.yml
@@ -70,6 +70,21 @@ jobs:
             exit 1
           fi
 
+  validate-changelog-diffs:
+    name: Validate changelog diffs
+    if: github.event_name == 'pull_request' || github.event_name == 'merge_group'
+    runs-on: ubuntu-latest
+    needs: prepare
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v6
+      - name: Validate changelog diffs
+        uses: ./.github/actions/check-merge-queue-changelogs
+        with:
+          github-token: ${{ secrets.GITHUB_TOKEN }}
+          base-ref: ${{ github.event.pull_request.base.ref || github.event.merge_group.base_ref }}
+          head-ref: ${{ github.event.pull_request.head.ref || github.event.merge_group.head_ref }}
+
   build:
     name: Build
     runs-on: ubuntu-latest

From 959c82895689206459e8a0b1779177b3af727b2f Mon Sep 17 00:00:00 2001
From: Maarten Zuidhoorn <maarten@zuidhoorn.com>
Date: Wed, 17 Dec 2025 14:00:38 +0100
Subject: [PATCH 02/10] Fix getting PR number for pull_request trigger

---
 .../actions/check-merge-queue-changelogs/action.yml  | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/.github/actions/check-merge-queue-changelogs/action.yml b/.github/actions/check-merge-queue-changelogs/action.yml
index 4bd2a027dcc..b4405e404d2 100644
--- a/.github/actions/check-merge-queue-changelogs/action.yml
+++ b/.github/actions/check-merge-queue-changelogs/action.yml
@@ -17,9 +17,8 @@ runs:
   using: composite
   steps:
     - name: Checkout repository
-      uses: MetaMask/action-checkout-and-setup@v2
+      uses: actions/checkout@v6
       with:
-        is-high-risk-environment: false
         fetch-depth: 0
 
     - name: Get pull request number
@@ -27,10 +26,17 @@ runs:
       uses: actions/github-script@v8
       env:
         HEAD_REF: ${{ inputs.head-ref }}
+        EVENT_NAME: ${{ github.event_name }}
       with:
         github-token: ${{ inputs.github-token }}
         script: |
-          const { HEAD_REF } = process.env;
+          const { EVENT_NAME, HEAD_REF } = process.env;
+
+          if (EVENT_NAME === 'pull_request') {
+            const prNumber = github.context.payload.pull_request.number;
+            return core.setOutput('pr-number', prNumber);
+          }
+
           const match = HEAD_REF.match(/\/pr-([0-9]+)-/u);
           if (!match) {
             return core.setFailed(`Could not extract pull request number from head ref: "${HEAD_REF}".`);

From 1bcd40cec78b40c13bc76a50d066c50cc117352d Mon Sep 17 00:00:00 2001
From: Maarten Zuidhoorn <maarten@zuidhoorn.com>
Date: Wed, 17 Dec 2025 14:03:13 +0100
Subject: [PATCH 03/10] Fix logic

---
 .github/actions/check-merge-queue-changelogs/action.yml | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/.github/actions/check-merge-queue-changelogs/action.yml b/.github/actions/check-merge-queue-changelogs/action.yml
index b4405e404d2..fe2984b872c 100644
--- a/.github/actions/check-merge-queue-changelogs/action.yml
+++ b/.github/actions/check-merge-queue-changelogs/action.yml
@@ -26,14 +26,13 @@ runs:
       uses: actions/github-script@v8
       env:
         HEAD_REF: ${{ inputs.head-ref }}
-        EVENT_NAME: ${{ github.event_name }}
       with:
         github-token: ${{ inputs.github-token }}
         script: |
-          const { EVENT_NAME, HEAD_REF } = process.env;
+          const { HEAD_REF } = process.env;
 
-          if (EVENT_NAME === 'pull_request') {
-            const prNumber = github.context.payload.pull_request.number;
+          if (github.event_name === 'pull_request') {
+            const prNumber = github.event.pull_request.number;
             return core.setOutput('pr-number', prNumber);
           }
 

From 057789c3973905783a6682c23ae12d0bb8e4df9f Mon Sep 17 00:00:00 2001
From: Maarten Zuidhoorn <maarten@zuidhoorn.com>
Date: Wed, 17 Dec 2025 14:08:03 +0100
Subject: [PATCH 04/10] Fix logic again

---
 .github/actions/check-merge-queue-changelogs/action.yml | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/.github/actions/check-merge-queue-changelogs/action.yml b/.github/actions/check-merge-queue-changelogs/action.yml
index fe2984b872c..fa4cac00c5b 100644
--- a/.github/actions/check-merge-queue-changelogs/action.yml
+++ b/.github/actions/check-merge-queue-changelogs/action.yml
@@ -26,12 +26,13 @@ runs:
       uses: actions/github-script@v8
       env:
         HEAD_REF: ${{ inputs.head-ref }}
+        EVENT_NAME: ${{ github.event_name }}
       with:
         github-token: ${{ inputs.github-token }}
         script: |
-          const { HEAD_REF } = process.env;
+          const { EVENT_NAME, HEAD_REF } = process.env;
 
-          if (github.event_name === 'pull_request') {
+          if (EVENT_NAME === 'pull_request') {
             const prNumber = github.event.pull_request.number;
             return core.setOutput('pr-number', prNumber);
           }

From 245dcb3ac3ea0ce356a19323c8730c98799408bc Mon Sep 17 00:00:00 2001
From: Maarten Zuidhoorn <maarten@zuidhoorn.com>
Date: Wed, 17 Dec 2025 14:11:23 +0100
Subject: [PATCH 05/10] Use `context` instead of `github`

---
 .github/actions/check-merge-queue-changelogs/action.yml | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/.github/actions/check-merge-queue-changelogs/action.yml b/.github/actions/check-merge-queue-changelogs/action.yml
index fa4cac00c5b..6cc26dc70fc 100644
--- a/.github/actions/check-merge-queue-changelogs/action.yml
+++ b/.github/actions/check-merge-queue-changelogs/action.yml
@@ -26,14 +26,13 @@ runs:
       uses: actions/github-script@v8
       env:
         HEAD_REF: ${{ inputs.head-ref }}
-        EVENT_NAME: ${{ github.event_name }}
       with:
         github-token: ${{ inputs.github-token }}
         script: |
           const { EVENT_NAME, HEAD_REF } = process.env;
 
-          if (EVENT_NAME === 'pull_request') {
-            const prNumber = github.event.pull_request.number;
+          if (context.eventName === 'pull_request') {
+            const prNumber = context.payload.pull_request.number;
             return core.setOutput('pr-number', prNumber);
           }
 

From e98e8b0ea118e1dc4ab82e4253800339f51174d3 Mon Sep 17 00:00:00 2001
From: Maarten Zuidhoorn <maarten@zuidhoorn.com>
Date: Wed, 17 Dec 2025 14:14:44 +0100
Subject: [PATCH 06/10] Add missing `GH_TOKEN`

---
 .github/actions/check-merge-queue-changelogs/action.yml | 1 +
 1 file changed, 1 insertion(+)

diff --git a/.github/actions/check-merge-queue-changelogs/action.yml b/.github/actions/check-merge-queue-changelogs/action.yml
index 6cc26dc70fc..101519128cf 100644
--- a/.github/actions/check-merge-queue-changelogs/action.yml
+++ b/.github/actions/check-merge-queue-changelogs/action.yml
@@ -50,6 +50,7 @@ runs:
       env:
         REPOSITORY: ${{ github.repository }}
         PR_NUMBER: ${{ steps.pr-number.outputs.pr-number }}
+        GH_TOKEN: ${{ inputs.github-token }}
       run: |
         BRANCH=$(gh api "/repos/${REPOSITORY}/pulls/${PR_NUMBER} --jq=.head.ref")
         echo "pr-branch=$BRANCH" >> "$GITHUB_OUTPUT"

From cb7cb98d68e5a8f9dc6fbadc3d2f75dd3aa50c60 Mon Sep 17 00:00:00 2001
From: Maarten Zuidhoorn <maarten@zuidhoorn.com>
Date: Wed, 17 Dec 2025 14:21:44 +0100
Subject: [PATCH 07/10] Fix command

---
 .github/actions/check-merge-queue-changelogs/action.yml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/.github/actions/check-merge-queue-changelogs/action.yml b/.github/actions/check-merge-queue-changelogs/action.yml
index 101519128cf..f158cfda3f1 100644
--- a/.github/actions/check-merge-queue-changelogs/action.yml
+++ b/.github/actions/check-merge-queue-changelogs/action.yml
@@ -67,7 +67,7 @@ runs:
       run: |
         set -euo pipefail
 
-        UPDATED_CHANGELOGS=$(git diff origin/"$BASE_REF"...origin/"$PR_BRANCH" --name-only | grep -E 'CHANGELOG\.md$' || true)
+        UPDATED_CHANGELOGS=$(git diff --name-only origin/"$BASE_REF"...origin/"$PR_BRANCH" | grep -E 'CHANGELOG\.md$' || true)
         if [ -n "$UPDATED_CHANGELOGS" ]; then
           for FILE in $UPDATED_CHANGELOGS; do
             git show origin/"$BASE_REF":"$FILE" > /tmp/base-changelog.md

From f20516b267809367b31c7a581590133ba6e3e249 Mon Sep 17 00:00:00 2001
From: Maarten Zuidhoorn <maarten@zuidhoorn.com>
Date: Wed, 17 Dec 2025 18:56:36 +0100
Subject: [PATCH 08/10] Clean up logic and fix issues

---
 .../check-merge-queue-changelogs/action.yml   | 33 +++++++++++--------
 .../check-changelog-diff.cjs                  |  2 +-
 .github/workflows/lint-build-test.yml         |  4 ---
 3 files changed, 21 insertions(+), 18 deletions(-)

diff --git a/.github/actions/check-merge-queue-changelogs/action.yml b/.github/actions/check-merge-queue-changelogs/action.yml
index f158cfda3f1..f32c7628b52 100644
--- a/.github/actions/check-merge-queue-changelogs/action.yml
+++ b/.github/actions/check-merge-queue-changelogs/action.yml
@@ -3,15 +3,10 @@ description: Check if the changelog was incorrectly merged in a merge queue
   pull request.
 
 inputs:
-  head-ref:
-    description: The head ref of the pull request.
-    required: true
-  base-ref:
-    description: The base ref to compare against.
-    required: true
   github-token:
     description: The GitHub token to use for authentication.
-    required: true
+    required: false
+    default: ${{ github.token }}
 
 runs:
   using: composite
@@ -25,7 +20,7 @@ runs:
       id: pr-number
       uses: actions/github-script@v8
       env:
-        HEAD_REF: ${{ inputs.head-ref }}
+        HEAD_REF: ${{ github.event.pull_request.head.ref || github.event.merge_group.head_ref }}
       with:
         github-token: ${{ inputs.github-token }}
         script: |
@@ -52,25 +47,37 @@ runs:
         PR_NUMBER: ${{ steps.pr-number.outputs.pr-number }}
         GH_TOKEN: ${{ inputs.github-token }}
       run: |
-        BRANCH=$(gh api "/repos/${REPOSITORY}/pulls/${PR_NUMBER} --jq=.head.ref")
+        BRANCH=$(gh api "/repos/${REPOSITORY}/pulls/${PR_NUMBER}" --jq=.head.ref)
         echo "pr-branch=$BRANCH" >> "$GITHUB_OUTPUT"
 
     - name: Check changelog changes
       id: changelog-check
       shell: bash
       env:
-        REF: ${{ inputs.ref }}
-        BASE_REF: ${{ inputs.base-ref }}
+        HEAD_REF: ${{ github.event.pull_request.head.ref || github.event.merge_group.head_ref }}
+        BASE_REF: ${{ github.event.pull_request.base.ref || github.event.merge_group.base_ref }}
         PR_BRANCH: ${{ steps.pr-branch.outputs.pr-branch }}
         REPOSITORY: ${{ github.repository }}
         ACTION_PATH: ${{ github.action_path }}
       run: |
         set -euo pipefail
 
-        UPDATED_CHANGELOGS=$(git diff --name-only origin/"$BASE_REF"...origin/"$PR_BRANCH" | grep -E 'CHANGELOG\.md$' || true)
+        # Strip invalid prefix from `BASE_REF`
+        # It comes prefixed with `refs/heads/`, but the branch is not checked out in this context
+        # We need to express it as a remote branch
+        PREFIXED_REF_REGEX='refs/heads/(.+)'
+        if [[ "$BASE_REF" =~ $PREFIXED_REF_REGEX ]]; then
+          BASE_REF="${BASH_REMATCH[1]}"
+        fi
+
+        TARGET_REF=$(git merge-base "origin/$BASE_REF" "origin/$PR_BRANCH")
+        git fetch origin "$TARGET_REF"
+
+        UPDATED_CHANGELOGS=$(git diff --name-only "$TARGET_REF" "origin/$PR_BRANCH" | grep -E 'CHANGELOG\.md$' || true)
         if [ -n "$UPDATED_CHANGELOGS" ]; then
           for FILE in $UPDATED_CHANGELOGS; do
-            git show origin/"$BASE_REF":"$FILE" > /tmp/base-changelog.md
+            echo "Checking changelog file: $FILE"
+            git show "$TARGET_REF":"$FILE" > /tmp/base-changelog.md
             git show origin/"$PR_BRANCH":"$FILE" > /tmp/pr-changelog.md
 
             node "${ACTION_PATH}/check-changelog-diff.cjs" \
diff --git a/.github/actions/check-merge-queue-changelogs/check-changelog-diff.cjs b/.github/actions/check-merge-queue-changelogs/check-changelog-diff.cjs
index d220ea30390..b32d3881581 100644
--- a/.github/actions/check-merge-queue-changelogs/check-changelog-diff.cjs
+++ b/.github/actions/check-merge-queue-changelogs/check-changelog-diff.cjs
@@ -87,7 +87,7 @@ for (const line of addedLines) {
 
 if (missingLines.length > 0) {
   console.error(
-    `The following lines added in the PR are missing from the "Unreleased" section after merge:\n\n- ${missingLines.join('\n- ')}\n\nPlease update your pull request and ensure that new changelog entries remain in the "Unreleased" section.`,
+    `The following lines added in the PR are missing from the "Unreleased" section after merge:\n\n  ${missingLines.join('\n  ')}\n\nPlease update your pull request and ensure that new changelog entries remain in the "Unreleased" section.`,
   );
 
   process.exitCode = 1;
diff --git a/.github/workflows/lint-build-test.yml b/.github/workflows/lint-build-test.yml
index e7e83888aef..770799adbca 100644
--- a/.github/workflows/lint-build-test.yml
+++ b/.github/workflows/lint-build-test.yml
@@ -80,10 +80,6 @@ jobs:
         uses: actions/checkout@v6
       - name: Validate changelog diffs
         uses: ./.github/actions/check-merge-queue-changelogs
-        with:
-          github-token: ${{ secrets.GITHUB_TOKEN }}
-          base-ref: ${{ github.event.pull_request.base.ref || github.event.merge_group.base_ref }}
-          head-ref: ${{ github.event.pull_request.head.ref || github.event.merge_group.head_ref }}
 
   build:
     name: Build

From 1bcbfc95165108e57adba11b38f99e48d96cc8f8 Mon Sep 17 00:00:00 2001
From: Maarten Zuidhoorn <maarten@zuidhoorn.com>
Date: Thu, 18 Dec 2025 10:47:42 +0100
Subject: [PATCH 09/10] Only check unreleased section for main and PR changelog

---
 .../check-merge-queue-changelogs/check-changelog-diff.cjs    | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/.github/actions/check-merge-queue-changelogs/check-changelog-diff.cjs b/.github/actions/check-merge-queue-changelogs/check-changelog-diff.cjs
index b32d3881581..a81998026c0 100644
--- a/.github/actions/check-merge-queue-changelogs/check-changelog-diff.cjs
+++ b/.github/actions/check-merge-queue-changelogs/check-changelog-diff.cjs
@@ -76,7 +76,10 @@ function getAddedLines(oldContent, newContent) {
 }
 
 const mergedUnreleased = getUnreleasedSection(mergedContent);
-const addedLines = getAddedLines(baseContent, prContent);
+const addedLines = getAddedLines(
+  getUnreleasedSection(baseContent),
+  getUnreleasedSection(prContent),
+);
 
 const missingLines = [];
 for (const line of addedLines) {

From 04224caf2cec224f710e34dbbcd642e2abbb888a Mon Sep 17 00:00:00 2001
From: Maarten Zuidhoorn <maarten@zuidhoorn.com>
Date: Thu, 18 Dec 2025 10:59:14 +0100
Subject: [PATCH 10/10] Check if file exists on target ref and fix diff
 algorithm

---
 .../check-merge-queue-changelogs/action.yml   | 10 +++++++
 .../check-changelog-diff.cjs                  | 28 ++++++++++++-------
 2 files changed, 28 insertions(+), 10 deletions(-)

diff --git a/.github/actions/check-merge-queue-changelogs/action.yml b/.github/actions/check-merge-queue-changelogs/action.yml
index f32c7628b52..8d9be178285 100644
--- a/.github/actions/check-merge-queue-changelogs/action.yml
+++ b/.github/actions/check-merge-queue-changelogs/action.yml
@@ -76,6 +76,16 @@ runs:
         UPDATED_CHANGELOGS=$(git diff --name-only "$TARGET_REF" "origin/$PR_BRANCH" | grep -E 'CHANGELOG\.md$' || true)
         if [ -n "$UPDATED_CHANGELOGS" ]; then
           for FILE in $UPDATED_CHANGELOGS; do
+            if [ ! -f "$FILE" ]; then
+              echo "Changelog file \"$FILE\" was deleted in this PR. Skipping."
+              continue
+            fi
+
+            if ! git cat-file -e "$TARGET_REF":"$FILE" 2>/dev/null; then
+              echo "Changelog file \"$FILE\" is new in this PR. Skipping."
+              continue
+            fi
+
             echo "Checking changelog file: $FILE"
             git show "$TARGET_REF":"$FILE" > /tmp/base-changelog.md
             git show origin/"$PR_BRANCH":"$FILE" > /tmp/pr-changelog.md
diff --git a/.github/actions/check-merge-queue-changelogs/check-changelog-diff.cjs b/.github/actions/check-merge-queue-changelogs/check-changelog-diff.cjs
index a81998026c0..857ec8a7510 100644
--- a/.github/actions/check-merge-queue-changelogs/check-changelog-diff.cjs
+++ b/.github/actions/check-merge-queue-changelogs/check-changelog-diff.cjs
@@ -13,9 +13,20 @@ if (process.argv.length < 5) {
 }
 
 /* eslint-disable n/no-sync */
-const baseContent = fs.readFileSync(process.argv[2], 'utf8');
-const prContent = fs.readFileSync(process.argv[3], 'utf8');
-const mergedContent = fs.readFileSync(process.argv[4], 'utf8');
+// The type of these is inferred as `Buffer` when using "utf-8" directly instead
+// of an options object. Even though it's a plain JavaScript file, it's nice to
+// keep the types correct.
+const baseContent = fs.readFileSync(process.argv[2], {
+  encoding: 'utf-8',
+});
+
+const prContent = fs.readFileSync(process.argv[3], {
+  encoding: 'utf-8',
+});
+
+const mergedContent = fs.readFileSync(process.argv[4], {
+  encoding: 'utf-8',
+});
 /* eslint-enable n/no-sync */
 
 /**
@@ -58,15 +69,12 @@ function getUnreleasedSection(content) {
 /**
  * Get the lines that were added in the PR content compared to the base content.
  *
- * @param {string} oldContent - The base changelog content.
- * @param {string} newContent - The PR changelog content.
+ * @param {Set<string>} oldLines - The base changelog content.
+ * @param {Set<string>} newLines - The PR changelog content.
  * @returns {string[]} The added lines as an array of strings.
  */
-function getAddedLines(oldContent, newContent) {
-  const oldLines = new Set(oldContent.split('\n').map((line) => line.trim()));
-  const newLines = newContent.split('\n').map((line) => line.trim());
-
-  return newLines.filter(
+function getAddedLines(oldLines, newLines) {
+  return Array.from(newLines).filter(
     (line) =>
       line.length > 0 &&
       !oldLines.has(line) &&