diff --git a/tools/pull_request_hooks/autoLabel.js b/tools/pull_request_hooks/autoLabel.js
index 90109849f8e..809e81f49c0 100644
--- a/tools/pull_request_hooks/autoLabel.js
+++ b/tools/pull_request_hooks/autoLabel.js
@@ -1,110 +1,177 @@
 import * as autoLabelConfig from "./autoLabelConfig.js";
 
-function keyword_to_cl_label() {
-  const keyword_to_cl_label = {};
-  for (const label in autoLabelConfig.changelog_labels) {
-    for (const keyword of autoLabelConfig.changelog_labels[label].keywords) {
-      keyword_to_cl_label[keyword] = label;
+/**
+ * Precompute a lowercase keyword → changelog label map
+ */
+const keywordToClLabel = (() => {
+  const map = {};
+  for (const [label, { keywords }] of Object.entries(
+    autoLabelConfig.changelog_labels
+  )) {
+    for (const keyword of keywords) {
+      map[keyword.toLowerCase()] = label;
     }
   }
-  return keyword_to_cl_label;
-}
+  return map;
+})();
 
-// Checks the body (primarily the changelog) for labels to add
+/**
+ * Precompute title keyword Sets per label for O(1) lookup
+ */
+const titleKeywordSets = (() => {
+  const map = {};
+  for (const [label, { keywords }] of Object.entries(
+    autoLabelConfig.title_labels
+  )) {
+    map[label] = new Set(keywords.map((k) => k.toLowerCase()));
+  }
+  return map;
+})();
+
+/**
+ * Precompute filepaths Sets per label for O(1) lookup
+ */
+const fileLabelFilepathSets = (() => {
+  const map = {};
+  for (const [label, { filepaths = [], file_extensions = [], add_only }] of Object.entries(
+    autoLabelConfig.file_labels
+  )) {
+    map[label] = { filepaths: new Set(filepaths), file_extensions: new Set(file_extensions), add_only };
+  }
+  return map;
+})();
+
+/**
+ * Checks the body (primarily the changelog) for labels to add
+ */
 function check_body_for_labels(body) {
   const labels_to_add = [];
 
-  // if the body contains a github "fixes #1234" line, add the Fix tag
-  const fix_regex = new RegExp(`(fix[des]*|resolve[sd]*)\s*#\d+`, "gmi");
+  // detect "fixes #1234" or "resolves #1234" in body
+  const fix_regex = /\b(?:fix(?:es|ed)?|resolve[sd]?)\s*#\d+\b/gim;
   if (fix_regex.test(body)) {
     labels_to_add.push("Fix");
   }
 
-  const keywords = keyword_to_cl_label();
+  const lines = body.split("\n");
+  let inChangelog = false;
 
-  let found_cl = false;
-  for (const line of body.split("\n")) {
+  for (const line of lines) {
     if (line.startsWith(":cl:")) {
-      found_cl = true;
-      continue;
-    } else if (line.startsWith("/:cl:")) {
-      break;
-    } else if (!found_cl) {
+      inChangelog = true;
       continue;
     }
+    if (line.startsWith("/:cl:")) break;
+    if (!inChangelog) continue;
+
     // see if the first segment of the line is one of the keywords
-    const found_label = keywords[line.split(":")[0]?.toLowerCase()];
-    if (found_label) {
-      // don't add a billion tags if they forgot to clear all the default ones
-      const line_text = line.split(":")[1].trim();
-      const cl_label = autoLabelConfig.changelog_labels[found_label];
-      if (
-        line_text !== cl_label.default_text &&
-        line_text !== cl_label.alt_default_text
-      ) {
-        labels_to_add.push(found_label);
-      }
+    const keyword = line.split(":")[0]?.toLowerCase();
+    const found_label = keywordToClLabel[keyword];
+    if (!found_label) continue;
+
+    // don't add a billion tags if they forgot to clear all the default ones
+    const line_text = line.split(":")[1]?.trim();
+    const { default_text, alt_default_text } =
+      autoLabelConfig.changelog_labels[found_label];
+
+    if (line_text !== default_text && line_text !== alt_default_text) {
+      labels_to_add.push(found_label);
     }
   }
+
   return labels_to_add;
 }
 
-// Checks the title for labels to add
+/**
+ * Checks the title for labels to add (O(1) keyword lookup)
+ */
 function check_title_for_labels(title) {
-  const labels_to_add = [];
   const title_lower = title.toLowerCase();
-  for (const label in autoLabelConfig.title_labels) {
-    let found = false;
-    for (const keyword of autoLabelConfig.title_labels[label].keywords) {
+  const labels_to_add = [];
+
+  for (const [label, keywordSet] of Object.entries(titleKeywordSets)) {
+    for (const keyword of keywordSet) {
       if (title_lower.includes(keyword)) {
-        found = true;
+        labels_to_add.push(label);
         break;
       }
     }
-    if (found) {
-      labels_to_add.push(label);
-    }
   }
   return labels_to_add;
 }
 
-function check_diff_line_for_element(diff, element) {
-  const tag_re = new RegExp(`^diff --git a/${element}/`);
-  return tag_re.test(diff);
-}
-
-// Checks the file diff for labels to add or remove
-async function check_diff_for_labels(diff_url) {
+/**
+ * Checks changed files for labels to add/remove (O(1) filepath lookup)
+ */
+async function check_diff_files_for_labels(github, context) {
   const labels_to_add = [];
   const labels_to_remove = [];
+
   try {
-    const diff = await fetch(diff_url);
-    if (diff.ok) {
-      const diff_txt = await diff.text();
-      for (const label in autoLabelConfig.file_labels) {
-        let found = false;
-        const { filepaths, add_only } = autoLabelConfig.file_labels[label];
-        for (const filepath of filepaths) {
-          if (check_diff_line_for_element(diff_txt, filepath)) {
+    // Use github.paginate to fetch all files (up to ~3000 max)
+    const allFiles = await github.paginate(
+      github.rest.pulls.listFiles,
+      {
+        owner: context.repo.owner,
+        repo: context.repo.repo,
+        pull_number: context.payload.pull_request.number,
+        per_page: 100, // max per request
+      }
+    );
+
+    if (!allFiles?.length) {
+      console.error("No files returned in pagination.");
+      return { labels_to_add, labels_to_remove };
+    }
+
+    // Set of changed filenames for quick lookup
+    const changedFiles = new Set(allFiles.map((f) => f.filename));
+
+    for (const [label, { filepaths = new Set(), file_extensions = new Set(), add_only }] of Object.entries(
+      fileLabelFilepathSets
+    )) {
+      let found = false;
+
+      // Filepath-based matching
+      for (const filename of changedFiles) {
+        for (const path of filepaths) {
+          if (filename.includes(path)) {
             found = true;
             break;
           }
         }
-        if (found) {
-          labels_to_add.push(label);
-        } else if (!add_only) {
-          labels_to_remove.push(label);
+        if (found) break;
+      }
+
+      // File extension-based matching
+      if (!found && file_extensions.size) {
+        for (const filename of changedFiles) {
+          for (const ext of file_extensions) {
+            if (filename.endsWith(ext)) {
+              found = true;
+              break;
+            }
+          }
+          if (found) break;
         }
       }
-    } else {
-      console.error(`Failed to fetch diff: ${diff.status} ${diff.statusText}`);
+
+      if (found) {
+        labels_to_add.push(label);
+      } else if (!add_only) {
+        labels_to_remove.push(label);
+      }
     }
-  } catch (e) {
-    console.error(e);
+  } catch (error) {
+    console.error("Error fetching paginated files:", error);
   }
+
   return { labels_to_add, labels_to_remove };
 }
 
+/**
+ * Main function to get the updated label set
+ */
 export async function get_updated_label_set({ github, context }) {
   const { action, pull_request } = context.payload;
   const {
@@ -115,39 +182,30 @@ export async function get_updated_label_set({ github, context }) {
     title = "",
   } = pull_request;
 
-  const updated_labels = new Set();
-  for (const label of labels) {
-    updated_labels.add(label.name);
-  }
+  const updated_labels = new Set(labels.map((l) => l.name));
 
-  // diff is always checked
+  // Always check file diffs
   if (diff_url) {
-    const diff_tags = await check_diff_for_labels(diff_url);
-    for (const label of diff_tags.labels_to_add) {
-      updated_labels.add(label);
-    }
-    for (const label of diff_tags.labels_to_remove) {
-      updated_labels.delete(label);
-    }
-  }
-  // body and title are only checked on open, not on sync
-  if (action === "opened") {
-    if (title) {
-      for (const label of check_title_for_labels(title)) {
-        updated_labels.add(label);
-      }
-    }
-    if (body) {
-      for (const label of check_body_for_labels(body)) {
-        updated_labels.add(label);
-      }
-    }
+    const { labels_to_add, labels_to_remove } =
+      await check_diff_files_for_labels(github, context);
+    labels_to_add.forEach((label) => updated_labels.add(label));
+    labels_to_remove.forEach((label) => updated_labels.delete(label));
   }
 
-  // this is always removed on updates
+  // Check body/title only when PR is opened, not on sync
+  if (action === "opened") {
+    if (title)
+      check_title_for_labels(title).forEach((label) =>
+        updated_labels.add(label)
+      );
+    if (body)
+      check_body_for_labels(body).forEach((label) => updated_labels.add(label));
+  }
+
+  // Always remove Test Merge Candidate
   updated_labels.delete("Test Merge Candidate");
 
-  // update merge conflict label
+  // Handle merge conflict label
   let merge_conflict = mergeable === false;
   // null means it was not reported yet
   // it is not normally included in the payload - a "get" is needed
@@ -159,6 +217,7 @@ export async function get_updated_label_set({ github, context }) {
         pull_number: pull_request.number,
       });
       // failed to find? still processing? try again in a few seconds
+
       if (response.data.mergeable === null) {
         console.log("Awaiting GitHub response for merge status...");
         await new Promise((r) => setTimeout(r, 10000));
@@ -177,6 +236,7 @@ export async function get_updated_label_set({ github, context }) {
       console.error(e);
     }
   }
+
   if (merge_conflict) {
     updated_labels.add("Merge Conflict");
   } else {
diff --git a/tools/pull_request_hooks/autoLabelConfig.js b/tools/pull_request_hooks/autoLabelConfig.js
index ca5c14b1d76..6d848fa715c 100644
--- a/tools/pull_request_hooks/autoLabelConfig.js
+++ b/tools/pull_request_hooks/autoLabelConfig.js
@@ -7,31 +7,34 @@
 // the label will not be removed
 export const file_labels = {
   GitHub: {
-    filepaths: [".github"],
+    filepaths: [".github/"],
   },
   SQL: {
-    filepaths: ["SQL"],
+    filepaths: ["SQL/"],
   },
   "Map Edit": {
-    filepaths: ["_maps"],
+    filepaths: ["_maps/"],
+    file_extensions: [".dmm"],
   },
   Tools: {
-    filepaths: ["tools"],
+    filepaths: ["tools/"],
   },
   "Config Update": {
-    filepaths: ["config", "code/controllers/configuration/entries"],
+    filepaths: ["config/", "code/controllers/configuration/entries/"],
     add_only: true,
   },
   Sprites: {
-    filepaths: ["icons"],
+    filepaths: ["icons/"],
+    file_extensions: [".dmi"],
     add_only: true,
   },
   Sound: {
-    filepaths: ["sound"],
+    filepaths: ["sound/"],
+    file_extensions: [".ogg"],
     add_only: true,
   },
   UI: {
-    filepaths: ["tgui"],
+    filepaths: ["tgui/"],
     add_only: true,
   },
 };