diff --git a/options/locale/locale_en-US.json b/options/locale/locale_en-US.json
index 93ac046612..5b36c92a53 100644
--- a/options/locale/locale_en-US.json
+++ b/options/locale/locale_en-US.json
@@ -2562,6 +2562,8 @@
   "repo.diff.load": "Load Diff",
   "repo.diff.generated": "Generated",
   "repo.diff.vendored": "Vendored",
+  "repo.diff.expand_all": "Expand all",
+  "repo.diff.collapse_expanded": "Collapse expanded",
   "repo.diff.comment.add_line_comment": "Add line comment",
   "repo.diff.comment.placeholder": "Leave a comment",
   "repo.diff.comment.add_single_comment": "Add single comment",
diff --git a/services/gitdiff/gitdiff.go b/services/gitdiff/gitdiff.go
index 7777cf4a1c..aacddf3856 100644
--- a/services/gitdiff/gitdiff.go
+++ b/services/gitdiff/gitdiff.go
@@ -228,7 +228,7 @@ func (d *DiffLine) RenderBlobExcerptButtons(fileNameHash string, data *DiffBlobE
 			link += fmt.Sprintf("&pull_issue_index=%d", data.PullIssueIndex)
 		}
 		return htmlutil.HTMLFormat(
-			`<button class="code-expander-button" hx-target="closest tr" hx-get="%s" data-hidden-comment-ids=",%s,">%s</button>`,
+			`<button class="code-expander-button" data-url="%s" data-hidden-comment-ids=",%s,">%s</button>`,
 			link, dataHiddenCommentIDs, svg.RenderHTML(svgName),
 		)
 	}
diff --git a/templates/repo/diff/box.tmpl b/templates/repo/diff/box.tmpl
index 41a8268cb3..2a69fcbc99 100644
--- a/templates/repo/diff/box.tmpl
+++ b/templates/repo/diff/box.tmpl
@@ -98,6 +98,9 @@
 									</a>
 								</div>
 								<button class="btn interact-fg tw-p-2 tw-shrink-0" data-clipboard-text="{{$file.Name}}" data-tooltip-content="{{ctx.Locale.Tr "copy_path"}}">{{svg "octicon-copy" 14}}</button>
+								{{if and $.DiffBlobExcerptData (not $file.IsSubmodule) (not $file.IsBin) (not $file.IsIncomplete)}}
+									<button class="btn interact-fg tw-p-2 tw-shrink-0 diff-expand-all" data-tooltip-content="{{ctx.Locale.Tr "repo.diff.expand_all"}}" data-expand-tooltip="{{ctx.Locale.Tr "repo.diff.expand_all"}}" data-collapse-tooltip="{{ctx.Locale.Tr "repo.diff.collapse_expanded"}}">{{svg "octicon-unfold" 14}}</button>
+								{{end}}
 								{{if $file.IsLFSFile}}
 									<span class="ui label">LFS</span>
 								{{end}}
diff --git a/tests/integration/compare_test.go b/tests/integration/compare_test.go
index a3cb538d5b..f70ab4473b 100644
--- a/tests/integration/compare_test.go
+++ b/tests/integration/compare_test.go
@@ -147,12 +147,12 @@ func TestCompareCodeExpand(t *testing.T) {
 		req := NewRequest(t, "GET", "/user1/test_blob_excerpt/compare/main...user2/test_blob_excerpt-fork:forked-branch")
 		resp := session.MakeRequest(t, req, http.StatusOK)
 		htmlDoc := NewHTMLParser(t, resp.Body)
-		els := htmlDoc.Find(`button.code-expander-button[hx-get]`)
+		els := htmlDoc.Find(`button.code-expander-button[data-url]`)
 
 		// all the links in the comparison should be to the forked repo&branch
 		assert.NotZero(t, els.Length())
 		for i := 0; i < els.Length(); i++ {
-			link := els.Eq(i).AttrOr("hx-get", "")
+			link := els.Eq(i).AttrOr("data-url", "")
 			assert.True(t, strings.HasPrefix(link, "/user2/test_blob_excerpt-fork/blob_excerpt/"))
 		}
 	})
diff --git a/web_src/js/features/repo-diff.ts b/web_src/js/features/repo-diff.ts
index 0c8b1357b0..fe1325c6ac 100644
--- a/web_src/js/features/repo-diff.ts
+++ b/web_src/js/features/repo-diff.ts
@@ -9,8 +9,9 @@ import {submitEventSubmitter, queryElemSiblings, hideElem, showElem, animateOnce
 import {POST, GET} from '../modules/fetch.ts';
 import {createTippy} from '../modules/tippy.ts';
 import {invertFileFolding} from './file-fold.ts';
-import {parseDom, sleep} from '../utils.ts';
+import {parseDom} from '../utils.ts';
 import {registerGlobalSelectorFunc} from '../modules/observer.ts';
+import {svg} from '../svg.ts';
 
 function initRepoDiffFileBox(el: HTMLElement) {
   // switch between "rendered" and "source", for image and CSV files
@@ -24,6 +25,12 @@ function initRepoDiffFileBox(el: HTMLElement) {
     hideElem(queryElemSiblings(target));
     showElem(target);
   }));
+
+  // Hide "expand all" button when there are no expandable sections
+  const expandAllBtn = el.querySelector('.diff-expand-all');
+  if (expandAllBtn && !el.querySelector('.code-expander-button')) {
+    hideElem(expandAllBtn);
+  }
 }
 
 function initRepoDiffConversationForm() {
@@ -247,12 +254,13 @@ async function onLocationHashChange() {
       const commentId = currentHash.substring(issueCommentPrefix.length);
       const expandButton = document.querySelector<HTMLElement>(`.code-expander-button[data-hidden-comment-ids*=",${commentId},"]`);
       if (expandButton) {
-        // avoid infinite loop, do not re-click the button if already clicked
+        // avoid infinite loop, do not re-expand the same button
         const attrAutoLoadClicked = 'data-auto-load-clicked';
         if (expandButton.hasAttribute(attrAutoLoadClicked)) return;
         expandButton.setAttribute(attrAutoLoadClicked, 'true');
-        expandButton.click();
-        await sleep(500); // Wait for HTMX to load the content. FIXME: need to drop htmx in the future
+        const tr = expandButton.closest('tr');
+        const url = expandButton.getAttribute('data-url');
+        if (tr && url) await fetchBlobExcerpt(tr, url);
         continue; // Try again to find the element
       }
     }
@@ -274,6 +282,105 @@ function initRepoDiffHashChangeListener() {
   onLocationHashChange();
 }
 
+const expandAllSavedState = new WeakMap<HTMLElement, HTMLElement>();
+
+async function fetchBlobExcerpt(tr: Element, url: string): Promise<void> {
+  const resp = await GET(url);
+  const text = await resp.text();
+  // Parse <tr> elements in proper table context
+  const tempTbody = document.createElement('tbody');
+  tempTbody.innerHTML = text;
+  const nodes = Array.from(tempTbody.children);
+  tr.replaceWith(...nodes);
+}
+
+async function expandAllLines(btn: HTMLElement, fileBox: HTMLElement) {
+  const fileBody = fileBox.querySelector('.diff-file-body');
+  if (!fileBody) return;
+
+  // Save original state for later collapse
+  const tbody = fileBody.querySelector('table.chroma tbody');
+  if (!tbody) return;
+  expandAllSavedState.set(fileBox, tbody.cloneNode(true) as HTMLElement);
+
+  btn.classList.add('disabled');
+  try {
+    // Loop: expand all collapsed sections until none remain.
+    // Each round fetches all current expander URLs in parallel, replaces their
+    // target <tr> rows with the response rows, then rescans for new expanders
+    // that may have appeared in the inserted content.
+    while (true) {
+      const expanders = collectExpanderButtons(fileBody, true);
+      if (expanders.length === 0) break;
+      await Promise.all(expanders.map(({tr, url}) => fetchBlobExcerpt(tr, url)));
+    }
+  } finally {
+    btn.classList.remove('disabled');
+  }
+
+  // Update button to "collapse" state
+  btn.innerHTML = svg('octicon-fold', 14);
+  btn.setAttribute('data-tooltip-content', btn.getAttribute('data-collapse-tooltip') ?? '');
+}
+
+function collapseExpandedLines(btn: HTMLElement, fileBox: HTMLElement) {
+  const savedTbody = expandAllSavedState.get(fileBox);
+  if (!savedTbody) return;
+
+  const tbody = fileBox.querySelector('.diff-file-body table.chroma tbody');
+  if (tbody) {
+    tbody.replaceWith(savedTbody.cloneNode(true));
+  }
+
+  expandAllSavedState.delete(fileBox);
+
+  // Update button to "expand" state
+  btn.innerHTML = svg('octicon-unfold', 14);
+  btn.setAttribute('data-tooltip-content', btn.getAttribute('data-expand-tooltip') ?? '');
+}
+
+// Collect one expander button per <tr> (skip duplicates from "updown" rows
+// that have both up/down buttons targeting the same row).
+// When fullExpand is true, the direction parameter is rewritten so the backend
+// expands the entire gap in a single response instead of chunk-by-chunk.
+function collectExpanderButtons(container: Element, fullExpand?: boolean): {tr: Element, url: string}[] {
+  const seen = new Set<Element>();
+  const expanders: {tr: Element, url: string}[] = [];
+  for (const btn of container.querySelectorAll<HTMLElement>('.code-expander-button')) {
+    const tr = btn.closest('tr');
+    let url = btn.getAttribute('data-url');
+    if (tr && url && !seen.has(tr)) {
+      seen.add(tr);
+      if (fullExpand) url = url.replace(/direction=[^&]*/, 'direction=full');
+      expanders.push({tr, url});
+    }
+  }
+  return expanders;
+}
+
+function initDiffExpandAllLines() {
+  addDelegatedEventListener(document, 'click', '.diff-expand-all', (btn, e) => {
+    e.preventDefault();
+    if (btn.classList.contains('disabled')) return;
+    const fileBox = btn.closest<HTMLElement>('.diff-file-box');
+    if (!fileBox) return;
+
+    if (expandAllSavedState.has(fileBox)) {
+      collapseExpandedLines(btn, fileBox);
+    } else {
+      expandAllLines(btn, fileBox);
+    }
+  });
+
+  // Handle individual expand button clicks
+  addDelegatedEventListener(document, 'click', '.code-expander-button', (btn, e) => {
+    e.preventDefault();
+    const tr = btn.closest('tr');
+    const url = btn.getAttribute('data-url');
+    if (tr && url) fetchBlobExcerpt(tr, url);
+  });
+}
+
 export function initRepoDiffView() {
   initRepoDiffConversationForm(); // such form appears on the "conversation" page and "diff" page
 
@@ -285,6 +392,7 @@ export function initRepoDiffView() {
   initDiffHeaderPopup();
   initViewedCheckboxListenerFor();
   initExpandAndCollapseFilesButton();
+  initDiffExpandAllLines();
   initRepoDiffHashChangeListener();
 
   registerGlobalSelectorFunc('#diff-file-boxes .diff-file-box', initRepoDiffFileBox);
diff --git a/web_src/js/svg.ts b/web_src/js/svg.ts
index cd19938c99..ee9b6e6dcd 100644
--- a/web_src/js/svg.ts
+++ b/web_src/js/svg.ts
@@ -34,6 +34,7 @@ import octiconFileDirectoryOpenFill from '../../public/assets/img/svg/octicon-fi
 import octiconFileSubmodule from '../../public/assets/img/svg/octicon-file-submodule.svg';
 import octiconFileSymlinkFile from '../../public/assets/img/svg/octicon-file-symlink-file.svg';
 import octiconFilter from '../../public/assets/img/svg/octicon-filter.svg';
+import octiconFold from '../../public/assets/img/svg/octicon-fold.svg';
 import octiconGear from '../../public/assets/img/svg/octicon-gear.svg';
 import octiconGitBranch from '../../public/assets/img/svg/octicon-git-branch.svg';
 import octiconGitCommit from '../../public/assets/img/svg/octicon-git-commit.svg';
@@ -78,6 +79,7 @@ import octiconTable from '../../public/assets/img/svg/octicon-table.svg';
 import octiconTag from '../../public/assets/img/svg/octicon-tag.svg';
 import octiconTrash from '../../public/assets/img/svg/octicon-trash.svg';
 import octiconTriangleDown from '../../public/assets/img/svg/octicon-triangle-down.svg';
+import octiconUnfold from '../../public/assets/img/svg/octicon-unfold.svg';
 import octiconX from '../../public/assets/img/svg/octicon-x.svg';
 import octiconXCircleFill from '../../public/assets/img/svg/octicon-x-circle-fill.svg';
 import octiconZoomIn from '../../public/assets/img/svg/octicon-zoom-in.svg';
@@ -117,6 +119,7 @@ const svgs = {
   'octicon-file-submodule': octiconFileSubmodule,
   'octicon-file-symlink-file': octiconFileSymlinkFile,
   'octicon-filter': octiconFilter,
+  'octicon-fold': octiconFold,
   'octicon-gear': octiconGear,
   'octicon-git-branch': octiconGitBranch,
   'octicon-git-commit': octiconGitCommit,
@@ -161,6 +164,7 @@ const svgs = {
   'octicon-tag': octiconTag,
   'octicon-trash': octiconTrash,
   'octicon-triangle-down': octiconTriangleDown,
+  'octicon-unfold': octiconUnfold,
   'octicon-x': octiconX,
   'octicon-x-circle-fill': octiconXCircleFill,
   'octicon-zoom-in': octiconZoomIn,