diff --git a/routers/web/repo/commit.go b/routers/web/repo/commit.go
index 1a86a62fae..0383e4ca9e 100644
--- a/routers/web/repo/commit.go
+++ b/routers/web/repo/commit.go
@@ -276,20 +276,24 @@ func Diff(ctx *context.Context) {
 	userName := ctx.Repo.Owner.Name
 	repoName := ctx.Repo.Repository.Name
 	commitID := ctx.PathParam("sha")
-	var (
-		gitRepo *git.Repository
-		err     error
-	)
+
+	diffBlobExcerptData := &gitdiff.DiffBlobExcerptData{
+		BaseLink:      ctx.Repo.RepoLink + "/blob_excerpt",
+		DiffStyle:     ctx.FormString("style"),
+		AfterCommitID: commitID,
+	}
+	gitRepo := ctx.Repo.GitRepo
+	var gitRepoStore gitrepo.Repository = ctx.Repo.Repository
 
 	if ctx.Data["PageIsWiki"] != nil {
-		gitRepo, err = gitrepo.OpenRepository(ctx, ctx.Repo.Repository.WikiStorageRepo())
+		var err error
+		gitRepoStore = ctx.Repo.Repository.WikiStorageRepo()
+		gitRepo, err = gitrepo.RepositoryFromRequestContextOrOpen(ctx, gitRepoStore)
 		if err != nil {
 			ctx.ServerError("Repo.GitRepo.GetCommit", err)
 			return
 		}
-		defer gitRepo.Close()
-	} else {
-		gitRepo = ctx.Repo.GitRepo
+		diffBlobExcerptData.BaseLink = ctx.Repo.RepoLink + "/wiki/blob_excerpt"
 	}
 
 	commit, err := gitRepo.GetCommit(commitID)
@@ -324,7 +328,7 @@ func Diff(ctx *context.Context) {
 		ctx.NotFound(err)
 		return
 	}
-	diffShortStat, err := gitdiff.GetDiffShortStat(ctx, ctx.Repo.Repository, gitRepo, "", commitID)
+	diffShortStat, err := gitdiff.GetDiffShortStat(ctx, gitRepoStore, gitRepo, "", commitID)
 	if err != nil {
 		ctx.ServerError("GetDiffShortStat", err)
 		return
@@ -360,6 +364,7 @@ func Diff(ctx *context.Context) {
 	ctx.Data["Title"] = commit.Summary() + " · " + base.ShortSha(commitID)
 	ctx.Data["Commit"] = commit
 	ctx.Data["Diff"] = diff
+	ctx.Data["DiffBlobExcerptData"] = diffBlobExcerptData
 
 	if !fileOnly {
 		diffTree, err := gitdiff.GetDiffTree(ctx, gitRepo, false, parentCommitID, commitID)
diff --git a/routers/web/repo/compare.go b/routers/web/repo/compare.go
index 9262703078..08bd0a7e74 100644
--- a/routers/web/repo/compare.go
+++ b/routers/web/repo/compare.go
@@ -14,6 +14,7 @@ import (
 	"net/http"
 	"net/url"
 	"path/filepath"
+	"sort"
 	"strings"
 
 	"code.gitea.io/gitea/models/db"
@@ -43,6 +44,7 @@ import (
 	"code.gitea.io/gitea/services/context/upload"
 	"code.gitea.io/gitea/services/gitdiff"
 	pull_service "code.gitea.io/gitea/services/pull"
+	user_service "code.gitea.io/gitea/services/user"
 )
 
 const (
@@ -638,6 +640,11 @@ func PrepareCompareDiff(
 	}
 	ctx.Data["DiffShortStat"] = diffShortStat
 	ctx.Data["Diff"] = diff
+	ctx.Data["DiffBlobExcerptData"] = &gitdiff.DiffBlobExcerptData{
+		BaseLink:      ci.HeadRepo.Link() + "/blob_excerpt",
+		DiffStyle:     ctx.FormString("style"),
+		AfterCommitID: headCommitID,
+	}
 	ctx.Data["DiffNotAvailable"] = diffShortStat.NumFiles == 0
 
 	if !fileOnly {
@@ -865,6 +872,28 @@ func CompareDiff(ctx *context.Context) {
 	ctx.HTML(http.StatusOK, tplCompare)
 }
 
+// attachCommentsToLines attaches comments to their corresponding diff lines
+func attachCommentsToLines(section *gitdiff.DiffSection, lineComments map[int64][]*issues_model.Comment) {
+	for _, line := range section.Lines {
+		if comments, ok := lineComments[int64(line.LeftIdx*-1)]; ok {
+			line.Comments = append(line.Comments, comments...)
+		}
+		if comments, ok := lineComments[int64(line.RightIdx)]; ok {
+			line.Comments = append(line.Comments, comments...)
+		}
+		sort.SliceStable(line.Comments, func(i, j int) bool {
+			return line.Comments[i].CreatedUnix < line.Comments[j].CreatedUnix
+		})
+	}
+}
+
+// attachHiddenCommentIDs calculates and attaches hidden comment IDs to expand buttons
+func attachHiddenCommentIDs(section *gitdiff.DiffSection, lineComments map[int64][]*issues_model.Comment) {
+	for _, line := range section.Lines {
+		gitdiff.FillHiddenCommentIDsForDiffLine(line, lineComments)
+	}
+}
+
 // ExcerptBlob render blob excerpt contents
 func ExcerptBlob(ctx *context.Context) {
 	commitID := ctx.PathParam("sha")
@@ -874,19 +903,26 @@ func ExcerptBlob(ctx *context.Context) {
 	idxRight := ctx.FormInt("right")
 	leftHunkSize := ctx.FormInt("left_hunk_size")
 	rightHunkSize := ctx.FormInt("right_hunk_size")
-	anchor := ctx.FormString("anchor")
 	direction := ctx.FormString("direction")
 	filePath := ctx.FormString("path")
 	gitRepo := ctx.Repo.GitRepo
+
+	diffBlobExcerptData := &gitdiff.DiffBlobExcerptData{
+		BaseLink:      ctx.Repo.RepoLink + "/blob_excerpt",
+		DiffStyle:     ctx.FormString("style"),
+		AfterCommitID: commitID,
+	}
+
 	if ctx.Data["PageIsWiki"] == true {
 		var err error
-		gitRepo, err = gitrepo.OpenRepository(ctx, ctx.Repo.Repository.WikiStorageRepo())
+		gitRepo, err = gitrepo.RepositoryFromRequestContextOrOpen(ctx, ctx.Repo.Repository.WikiStorageRepo())
 		if err != nil {
 			ctx.ServerError("OpenRepository", err)
 			return
 		}
-		defer gitRepo.Close()
+		diffBlobExcerptData.BaseLink = ctx.Repo.RepoLink + "/wiki/blob_excerpt"
 	}
+
 	chunkSize := gitdiff.BlobExcerptChunkSize
 	commit, err := gitRepo.GetCommit(commitID)
 	if err != nil {
@@ -947,10 +983,43 @@ func ExcerptBlob(ctx *context.Context) {
 			section.Lines = append(section.Lines, lineSection)
 		}
 	}
+
+	diffBlobExcerptData.PullIssueIndex = ctx.FormInt64("pull_issue_index")
+	if diffBlobExcerptData.PullIssueIndex > 0 {
+		if !ctx.Repo.CanRead(unit.TypePullRequests) {
+			ctx.NotFound(nil)
+			return
+		}
+
+		issue, err := issues_model.GetIssueByIndex(ctx, ctx.Repo.Repository.ID, diffBlobExcerptData.PullIssueIndex)
+		if err != nil {
+			log.Error("GetIssueByIndex error: %v", err)
+		} else if issue.IsPull {
+			// FIXME: DIFF-CONVERSATION-DATA: the following data assignment is fragile
+			ctx.Data["Issue"] = issue
+			ctx.Data["CanBlockUser"] = func(blocker, blockee *user_model.User) bool {
+				return user_service.CanBlockUser(ctx, ctx.Doer, blocker, blockee)
+			}
+			// and "diff/comment_form.tmpl" (reply comment) needs them
+			ctx.Data["PageIsPullFiles"] = true
+			ctx.Data["AfterCommitID"] = diffBlobExcerptData.AfterCommitID
+
+			allComments, err := issues_model.FetchCodeComments(ctx, issue, ctx.Doer, ctx.FormBool("show_outdated"))
+			if err != nil {
+				log.Error("FetchCodeComments error: %v", err)
+			} else {
+				if lineComments, ok := allComments[filePath]; ok {
+					attachCommentsToLines(section, lineComments)
+					attachHiddenCommentIDs(section, lineComments)
+				}
+			}
+		}
+	}
+
 	ctx.Data["section"] = section
 	ctx.Data["FileNameHash"] = git.HashFilePathForWebUI(filePath)
-	ctx.Data["AfterCommitID"] = commitID
-	ctx.Data["Anchor"] = anchor
+	ctx.Data["DiffBlobExcerptData"] = diffBlobExcerptData
+
 	ctx.HTML(http.StatusOK, tplBlobExcerpt)
 }
 
diff --git a/routers/web/repo/compare_test.go b/routers/web/repo/compare_test.go
new file mode 100644
index 0000000000..61472dc71e
--- /dev/null
+++ b/routers/web/repo/compare_test.go
@@ -0,0 +1,40 @@
+// Copyright 2025 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package repo
+
+import (
+	"testing"
+
+	issues_model "code.gitea.io/gitea/models/issues"
+	"code.gitea.io/gitea/services/gitdiff"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestAttachCommentsToLines(t *testing.T) {
+	section := &gitdiff.DiffSection{
+		Lines: []*gitdiff.DiffLine{
+			{LeftIdx: 5, RightIdx: 10},
+			{LeftIdx: 6, RightIdx: 11},
+		},
+	}
+
+	lineComments := map[int64][]*issues_model.Comment{
+		-5: {{ID: 100, CreatedUnix: 1000}},                               // left side comment
+		10: {{ID: 200, CreatedUnix: 2000}},                               // right side comment
+		11: {{ID: 300, CreatedUnix: 1500}, {ID: 301, CreatedUnix: 2500}}, // multiple comments
+	}
+
+	attachCommentsToLines(section, lineComments)
+
+	// First line should have left and right comments
+	assert.Len(t, section.Lines[0].Comments, 2)
+	assert.Equal(t, int64(100), section.Lines[0].Comments[0].ID)
+	assert.Equal(t, int64(200), section.Lines[0].Comments[1].ID)
+
+	// Second line should have two comments, sorted by creation time
+	assert.Len(t, section.Lines[1].Comments, 2)
+	assert.Equal(t, int64(300), section.Lines[1].Comments[0].ID)
+	assert.Equal(t, int64(301), section.Lines[1].Comments[1].ID)
+}
diff --git a/routers/web/repo/pull.go b/routers/web/repo/pull.go
index f61571231f..cfe9a7ae02 100644
--- a/routers/web/repo/pull.go
+++ b/routers/web/repo/pull.go
@@ -827,6 +827,12 @@ func viewPullFiles(ctx *context.Context, beforeCommitID, afterCommitID string) {
 	}
 
 	ctx.Data["Diff"] = diff
+	ctx.Data["DiffBlobExcerptData"] = &gitdiff.DiffBlobExcerptData{
+		BaseLink:       ctx.Repo.RepoLink + "/blob_excerpt",
+		PullIssueIndex: pull.Index,
+		DiffStyle:      ctx.FormString("style"),
+		AfterCommitID:  afterCommitID,
+	}
 	ctx.Data["DiffNotAvailable"] = diffShortStat.NumFiles == 0
 
 	if ctx.IsSigned && ctx.Doer != nil {
diff --git a/services/gitdiff/gitdiff.go b/services/gitdiff/gitdiff.go
index db0f565b52..96aea8308c 100644
--- a/services/gitdiff/gitdiff.go
+++ b/services/gitdiff/gitdiff.go
@@ -22,19 +22,21 @@ import (
 	git_model "code.gitea.io/gitea/models/git"
 	issues_model "code.gitea.io/gitea/models/issues"
 	pull_model "code.gitea.io/gitea/models/pull"
-	repo_model "code.gitea.io/gitea/models/repo"
 	user_model "code.gitea.io/gitea/models/user"
 	"code.gitea.io/gitea/modules/analyze"
+	"code.gitea.io/gitea/modules/base"
 	"code.gitea.io/gitea/modules/charset"
 	"code.gitea.io/gitea/modules/git"
 	"code.gitea.io/gitea/modules/git/attribute"
 	"code.gitea.io/gitea/modules/git/gitcmd"
 	"code.gitea.io/gitea/modules/gitrepo"
 	"code.gitea.io/gitea/modules/highlight"
+	"code.gitea.io/gitea/modules/htmlutil"
 	"code.gitea.io/gitea/modules/lfs"
 	"code.gitea.io/gitea/modules/log"
 	"code.gitea.io/gitea/modules/optional"
 	"code.gitea.io/gitea/modules/setting"
+	"code.gitea.io/gitea/modules/svg"
 	"code.gitea.io/gitea/modules/translation"
 	"code.gitea.io/gitea/modules/util"
 
@@ -67,18 +69,6 @@ const (
 	DiffFileCopy
 )
 
-// DiffLineExpandDirection represents the DiffLineSection expand direction
-type DiffLineExpandDirection uint8
-
-// DiffLineExpandDirection possible values.
-const (
-	DiffLineExpandNone DiffLineExpandDirection = iota + 1
-	DiffLineExpandSingle
-	DiffLineExpandUpDown
-	DiffLineExpandUp
-	DiffLineExpandDown
-)
-
 // DiffLine represents a line difference in a DiffSection.
 type DiffLine struct {
 	LeftIdx     int // line number, 1-based
@@ -99,6 +89,8 @@ type DiffLineSectionInfo struct {
 	RightIdx      int
 	LeftHunkSize  int
 	RightHunkSize int
+
+	HiddenCommentIDs []int64 // IDs of hidden comments in this section
 }
 
 // DiffHTMLOperation is the HTML version of diffmatchpatch.Diff
@@ -153,8 +145,7 @@ func (d *DiffLine) GetLineTypeMarker() string {
 	return ""
 }
 
-// GetBlobExcerptQuery builds query string to get blob excerpt
-func (d *DiffLine) GetBlobExcerptQuery() string {
+func (d *DiffLine) getBlobExcerptQuery() string {
 	query := fmt.Sprintf(
 		"last_left=%d&last_right=%d&"+
 			"left=%d&right=%d&"+
@@ -167,19 +158,88 @@ func (d *DiffLine) GetBlobExcerptQuery() string {
 	return query
 }
 
-// GetExpandDirection gets DiffLineExpandDirection
-func (d *DiffLine) GetExpandDirection() DiffLineExpandDirection {
+func (d *DiffLine) getExpandDirection() string {
 	if d.Type != DiffLineSection || d.SectionInfo == nil || d.SectionInfo.LeftIdx-d.SectionInfo.LastLeftIdx <= 1 || d.SectionInfo.RightIdx-d.SectionInfo.LastRightIdx <= 1 {
-		return DiffLineExpandNone
+		return ""
 	}
 	if d.SectionInfo.LastLeftIdx <= 0 && d.SectionInfo.LastRightIdx <= 0 {
-		return DiffLineExpandUp
+		return "up"
 	} else if d.SectionInfo.RightIdx-d.SectionInfo.LastRightIdx > BlobExcerptChunkSize && d.SectionInfo.RightHunkSize > 0 {
-		return DiffLineExpandUpDown
+		return "updown"
 	} else if d.SectionInfo.LeftHunkSize <= 0 && d.SectionInfo.RightHunkSize <= 0 {
-		return DiffLineExpandDown
+		return "down"
 	}
-	return DiffLineExpandSingle
+	return "single"
+}
+
+type DiffBlobExcerptData struct {
+	BaseLink       string
+	IsWikiRepo     bool
+	PullIssueIndex int64
+	DiffStyle      string
+	AfterCommitID  string
+}
+
+func (d *DiffLine) RenderBlobExcerptButtons(fileNameHash string, data *DiffBlobExcerptData) template.HTML {
+	dataHiddenCommentIDs := strings.Join(base.Int64sToStrings(d.SectionInfo.HiddenCommentIDs), ",")
+	anchor := fmt.Sprintf("diff-%sK%d", fileNameHash, d.SectionInfo.RightIdx)
+
+	makeButton := func(direction, svgName string) template.HTML {
+		style := util.IfZero(data.DiffStyle, "unified")
+		link := data.BaseLink + "/" + data.AfterCommitID + fmt.Sprintf("?style=%s&direction=%s&anchor=%s", url.QueryEscape(style), direction, url.QueryEscape(anchor)) + "&" + d.getBlobExcerptQuery()
+		if data.PullIssueIndex > 0 {
+			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>`,
+			link, dataHiddenCommentIDs, svg.RenderHTML(svgName),
+		)
+	}
+	var content template.HTML
+
+	if len(d.SectionInfo.HiddenCommentIDs) > 0 {
+		tooltip := fmt.Sprintf("%d hidden comment(s)", len(d.SectionInfo.HiddenCommentIDs))
+		content += htmlutil.HTMLFormat(`<span class="code-comment-more" data-tooltip-content="%s">%d</span>`, tooltip, len(d.SectionInfo.HiddenCommentIDs))
+	}
+
+	expandDirection := d.getExpandDirection()
+	if expandDirection == "up" || expandDirection == "updown" {
+		content += makeButton("up", "octicon-fold-up")
+	}
+	if expandDirection == "updown" || expandDirection == "down" {
+		content += makeButton("down", "octicon-fold-down")
+	}
+	if expandDirection == "single" {
+		content += makeButton("single", "octicon-fold")
+	}
+	return htmlutil.HTMLFormat(`<div class="code-expander-buttons" data-expand-direction="%s">%s</div>`, expandDirection, content)
+}
+
+// FillHiddenCommentIDsForDiffLine finds comment IDs that are in the hidden range of an expand button
+func FillHiddenCommentIDsForDiffLine(line *DiffLine, lineComments map[int64][]*issues_model.Comment) {
+	if line.Type != DiffLineSection {
+		return
+	}
+
+	var hiddenCommentIDs []int64
+	for commentLineNum, comments := range lineComments {
+		if commentLineNum < 0 {
+			// ATTENTION: BLOB-EXCERPT-COMMENT-RIGHT: skip left-side, unchanged lines always use "right (proposed)" side for comments
+			continue
+		}
+		lineNum := int(commentLineNum)
+		isEndOfFileExpansion := line.SectionInfo.RightHunkSize == 0
+		inRange := lineNum > line.SectionInfo.LastRightIdx &&
+			(isEndOfFileExpansion && lineNum <= line.SectionInfo.RightIdx ||
+				!isEndOfFileExpansion && lineNum < line.SectionInfo.RightIdx)
+
+		if inRange {
+			for _, comment := range comments {
+				hiddenCommentIDs = append(hiddenCommentIDs, comment.ID)
+			}
+		}
+	}
+	line.SectionInfo.HiddenCommentIDs = hiddenCommentIDs
 }
 
 func getDiffLineSectionInfo(treePath, line string, lastLeftIdx, lastRightIdx int) *DiffLineSectionInfo {
@@ -485,6 +545,8 @@ func (diff *Diff) LoadComments(ctx context.Context, issue *issues_model.Issue, c
 					sort.SliceStable(line.Comments, func(i, j int) bool {
 						return line.Comments[i].CreatedUnix < line.Comments[j].CreatedUnix
 					})
+					// Mark expand buttons that have comments in hidden lines
+					FillHiddenCommentIDsForDiffLine(line, lineCommits)
 				}
 			}
 		}
@@ -1281,7 +1343,7 @@ type DiffShortStat struct {
 	NumFiles, TotalAddition, TotalDeletion int
 }
 
-func GetDiffShortStat(ctx context.Context, repo *repo_model.Repository, gitRepo *git.Repository, beforeCommitID, afterCommitID string) (*DiffShortStat, error) {
+func GetDiffShortStat(ctx context.Context, repoStorage gitrepo.Repository, gitRepo *git.Repository, beforeCommitID, afterCommitID string) (*DiffShortStat, error) {
 	afterCommit, err := gitRepo.GetCommit(afterCommitID)
 	if err != nil {
 		return nil, err
@@ -1293,7 +1355,7 @@ func GetDiffShortStat(ctx context.Context, repo *repo_model.Repository, gitRepo
 	}
 
 	diff := &DiffShortStat{}
-	diff.NumFiles, diff.TotalAddition, diff.TotalDeletion, err = gitrepo.GetDiffShortStatByCmdArgs(ctx, repo, nil, actualBeforeCommitID.String(), afterCommitID)
+	diff.NumFiles, diff.TotalAddition, diff.TotalDeletion, err = gitrepo.GetDiffShortStatByCmdArgs(ctx, repoStorage, nil, actualBeforeCommitID.String(), afterCommitID)
 	if err != nil {
 		return nil, err
 	}
@@ -1386,6 +1448,75 @@ func CommentAsDiff(ctx context.Context, c *issues_model.Comment) (*Diff, error)
 	return diff, nil
 }
 
+// GeneratePatchForUnchangedLine creates a patch showing code context for an unchanged line
+func GeneratePatchForUnchangedLine(gitRepo *git.Repository, commitID, treePath string, line int64, contextLines int) (string, error) {
+	commit, err := gitRepo.GetCommit(commitID)
+	if err != nil {
+		return "", fmt.Errorf("GetCommit: %w", err)
+	}
+
+	entry, err := commit.GetTreeEntryByPath(treePath)
+	if err != nil {
+		return "", fmt.Errorf("GetTreeEntryByPath: %w", err)
+	}
+
+	blob := entry.Blob()
+	dataRc, err := blob.DataAsync()
+	if err != nil {
+		return "", fmt.Errorf("DataAsync: %w", err)
+	}
+	defer dataRc.Close()
+
+	return generatePatchForUnchangedLineFromReader(dataRc, treePath, line, contextLines)
+}
+
+// generatePatchForUnchangedLineFromReader is the testable core logic that generates a patch from a reader
+func generatePatchForUnchangedLineFromReader(reader io.Reader, treePath string, line int64, contextLines int) (string, error) {
+	// Calculate line range (commented line + lines above it)
+	commentLine := int(line)
+	if line < 0 {
+		commentLine = int(-line)
+	}
+	startLine := max(commentLine-contextLines, 1)
+	endLine := commentLine
+
+	// Read only the needed lines efficiently
+	scanner := bufio.NewScanner(reader)
+	currentLine := 0
+	var lines []string
+	for scanner.Scan() {
+		currentLine++
+		if currentLine >= startLine && currentLine <= endLine {
+			lines = append(lines, scanner.Text())
+		}
+		if currentLine > endLine {
+			break
+		}
+	}
+	if err := scanner.Err(); err != nil {
+		return "", fmt.Errorf("scanner error: %w", err)
+	}
+
+	if len(lines) == 0 {
+		return "", fmt.Errorf("no lines found in range %d-%d", startLine, endLine)
+	}
+
+	// Generate synthetic patch
+	var patchBuilder strings.Builder
+	patchBuilder.WriteString(fmt.Sprintf("diff --git a/%s b/%s\n", treePath, treePath))
+	patchBuilder.WriteString(fmt.Sprintf("--- a/%s\n", treePath))
+	patchBuilder.WriteString(fmt.Sprintf("+++ b/%s\n", treePath))
+	patchBuilder.WriteString(fmt.Sprintf("@@ -%d,%d +%d,%d @@\n", startLine, len(lines), startLine, len(lines)))
+
+	for _, lineContent := range lines {
+		patchBuilder.WriteString(" ")
+		patchBuilder.WriteString(lineContent)
+		patchBuilder.WriteString("\n")
+	}
+
+	return patchBuilder.String(), nil
+}
+
 // CommentMustAsDiff executes AsDiff and logs the error instead of returning
 func CommentMustAsDiff(ctx context.Context, c *issues_model.Comment) *Diff {
 	if c == nil {
diff --git a/services/gitdiff/gitdiff_test.go b/services/gitdiff/gitdiff_test.go
index 7b64b6b5f8..51fb9b58d6 100644
--- a/services/gitdiff/gitdiff_test.go
+++ b/services/gitdiff/gitdiff_test.go
@@ -640,3 +640,346 @@ func TestNoCrashes(t *testing.T) {
 		ParsePatch(t.Context(), setting.Git.MaxGitDiffLines, setting.Git.MaxGitDiffLineCharacters, setting.Git.MaxGitDiffFiles, strings.NewReader(testcase.gitdiff), "")
 	}
 }
+
+func TestGeneratePatchForUnchangedLineFromReader(t *testing.T) {
+	tests := []struct {
+		name         string
+		content      string
+		treePath     string
+		line         int64
+		contextLines int
+		want         string
+		wantErr      bool
+	}{
+		{
+			name:         "single line with context",
+			content:      "line1\nline2\nline3\nline4\nline5\n",
+			treePath:     "test.txt",
+			line:         3,
+			contextLines: 1,
+			want: `diff --git a/test.txt b/test.txt
+--- a/test.txt
++++ b/test.txt
+@@ -2,2 +2,2 @@
+ line2
+ line3
+`,
+		},
+		{
+			name:         "negative line number (left side)",
+			content:      "line1\nline2\nline3\nline4\nline5\n",
+			treePath:     "test.txt",
+			line:         -3,
+			contextLines: 1,
+			want: `diff --git a/test.txt b/test.txt
+--- a/test.txt
++++ b/test.txt
+@@ -2,2 +2,2 @@
+ line2
+ line3
+`,
+		},
+		{
+			name:         "line near start of file",
+			content:      "line1\nline2\nline3\n",
+			treePath:     "test.txt",
+			line:         2,
+			contextLines: 5,
+			want: `diff --git a/test.txt b/test.txt
+--- a/test.txt
++++ b/test.txt
+@@ -1,2 +1,2 @@
+ line1
+ line2
+`,
+		},
+		{
+			name:         "first line with context",
+			content:      "line1\nline2\nline3\n",
+			treePath:     "test.txt",
+			line:         1,
+			contextLines: 3,
+			want: `diff --git a/test.txt b/test.txt
+--- a/test.txt
++++ b/test.txt
+@@ -1,1 +1,1 @@
+ line1
+`,
+		},
+		{
+			name:         "zero context lines",
+			content:      "line1\nline2\nline3\n",
+			treePath:     "test.txt",
+			line:         2,
+			contextLines: 0,
+			want: `diff --git a/test.txt b/test.txt
+--- a/test.txt
++++ b/test.txt
+@@ -2,1 +2,1 @@
+ line2
+`,
+		},
+		{
+			name:         "multi-line context",
+			content:      "package main\n\nfunc main() {\n  fmt.Println(\"Hello\")\n}\n",
+			treePath:     "main.go",
+			line:         4,
+			contextLines: 2,
+			want: `diff --git a/main.go b/main.go
+--- a/main.go
++++ b/main.go
+@@ -2,3 +2,3 @@
+<SP>
+ func main() {
+   fmt.Println("Hello")
+`,
+		},
+		{
+			name:         "empty file",
+			content:      "",
+			treePath:     "empty.txt",
+			line:         1,
+			contextLines: 1,
+			wantErr:      true,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			reader := strings.NewReader(tt.content)
+			got, err := generatePatchForUnchangedLineFromReader(reader, tt.treePath, tt.line, tt.contextLines)
+			if tt.wantErr {
+				assert.Error(t, err)
+			} else {
+				require.NoError(t, err)
+				assert.Equal(t, strings.ReplaceAll(tt.want, "<SP>", " "), got)
+			}
+		})
+	}
+}
+
+func TestCalculateHiddenCommentIDsForLine(t *testing.T) {
+	tests := []struct {
+		name         string
+		line         *DiffLine
+		lineComments map[int64][]*issues_model.Comment
+		expected     []int64
+	}{
+		{
+			name: "comments in hidden range",
+			line: &DiffLine{
+				Type: DiffLineSection,
+				SectionInfo: &DiffLineSectionInfo{
+					LastRightIdx: 10,
+					RightIdx:     20,
+				},
+			},
+			lineComments: map[int64][]*issues_model.Comment{
+				15: {{ID: 100}, {ID: 101}},
+				12: {{ID: 102}},
+			},
+			expected: []int64{100, 101, 102},
+		},
+		{
+			name: "comments outside hidden range",
+			line: &DiffLine{
+				Type: DiffLineSection,
+				SectionInfo: &DiffLineSectionInfo{
+					LastRightIdx: 10,
+					RightIdx:     20,
+				},
+			},
+			lineComments: map[int64][]*issues_model.Comment{
+				5:  {{ID: 100}},
+				25: {{ID: 101}},
+			},
+			expected: nil,
+		},
+		{
+			name: "negative line numbers (left side)",
+			line: &DiffLine{
+				Type: DiffLineSection,
+				SectionInfo: &DiffLineSectionInfo{
+					LastRightIdx: 10,
+					RightIdx:     20,
+				},
+			},
+			lineComments: map[int64][]*issues_model.Comment{
+				-15: {{ID: 100}}, // Left-side comment, should NOT be counted
+				15:  {{ID: 101}}, // Right-side comment, should be counted
+			},
+			expected: []int64{101}, // Only right-side comment
+		},
+		{
+			name: "boundary conditions - normal expansion (both boundaries exclusive)",
+			line: &DiffLine{
+				Type: DiffLineSection,
+				SectionInfo: &DiffLineSectionInfo{
+					LastRightIdx:  10,
+					RightIdx:      20,
+					RightHunkSize: 5, // Normal case: next section has content
+				},
+			},
+			lineComments: map[int64][]*issues_model.Comment{
+				10: {{ID: 100}}, // at LastRightIdx (visible line), should NOT be included
+				20: {{ID: 101}}, // at RightIdx (visible line), should NOT be included
+				11: {{ID: 102}}, // just inside range, should be included
+				19: {{ID: 103}}, // just inside range, should be included
+			},
+			expected: []int64{102, 103},
+		},
+		{
+			name: "boundary conditions - end of file expansion (RightIdx inclusive)",
+			line: &DiffLine{
+				Type: DiffLineSection,
+				SectionInfo: &DiffLineSectionInfo{
+					LastRightIdx:  54,
+					RightIdx:      70,
+					RightHunkSize: 0, // End of file: no more content after
+				},
+			},
+			lineComments: map[int64][]*issues_model.Comment{
+				54: {{ID: 54}}, // at LastRightIdx (visible line), should NOT be included
+				70: {{ID: 70}}, // at RightIdx (last hidden line), SHOULD be included
+				60: {{ID: 60}}, // inside range, should be included
+			},
+			expected: []int64{60, 70}, // Lines 60 and 70 are hidden
+		},
+		{
+			name: "real-world scenario - start of file with hunk",
+			line: &DiffLine{
+				Type: DiffLineSection,
+				SectionInfo: &DiffLineSectionInfo{
+					LastRightIdx:  0,  // No previous visible section
+					RightIdx:      26, // Line 26 is first visible line of hunk
+					RightHunkSize: 9,  // Normal hunk with content
+				},
+			},
+			lineComments: map[int64][]*issues_model.Comment{
+				1:  {{ID: 1}},  // Line 1 is hidden
+				26: {{ID: 26}}, // Line 26 is visible (hunk start) - should NOT be hidden
+				10: {{ID: 10}}, // Line 10 is hidden
+				15: {{ID: 15}}, // Line 15 is hidden
+			},
+			expected: []int64{1, 10, 15}, // Lines 1, 10, 15 are hidden; line 26 is visible
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			FillHiddenCommentIDsForDiffLine(tt.line, tt.lineComments)
+			assert.ElementsMatch(t, tt.expected, tt.line.SectionInfo.HiddenCommentIDs)
+		})
+	}
+}
+
+func TestDiffLine_RenderBlobExcerptButtons(t *testing.T) {
+	tests := []struct {
+		name             string
+		line             *DiffLine
+		fileNameHash     string
+		data             *DiffBlobExcerptData
+		expectContains   []string
+		expectNotContain []string
+	}{
+		{
+			name: "expand up button with hidden comments",
+			line: &DiffLine{
+				Type: DiffLineSection,
+				SectionInfo: &DiffLineSectionInfo{
+					LastRightIdx:     0,
+					RightIdx:         26,
+					LeftIdx:          26,
+					LastLeftIdx:      0,
+					LeftHunkSize:     0,
+					RightHunkSize:    0,
+					HiddenCommentIDs: []int64{100},
+				},
+			},
+			fileNameHash: "abc123",
+			data: &DiffBlobExcerptData{
+				BaseLink:      "/repo/blob_excerpt",
+				AfterCommitID: "commit123",
+				DiffStyle:     "unified",
+			},
+			expectContains: []string{
+				"octicon-fold-up",
+				"direction=up",
+				"code-comment-more",
+				"1 hidden comment(s)",
+			},
+		},
+		{
+			name: "expand up and down buttons with pull request",
+			line: &DiffLine{
+				Type: DiffLineSection,
+				SectionInfo: &DiffLineSectionInfo{
+					LastRightIdx:     10,
+					RightIdx:         50,
+					LeftIdx:          10,
+					LastLeftIdx:      5,
+					LeftHunkSize:     5,
+					RightHunkSize:    5,
+					HiddenCommentIDs: []int64{200, 201},
+				},
+			},
+			fileNameHash: "def456",
+			data: &DiffBlobExcerptData{
+				BaseLink:       "/repo/blob_excerpt",
+				AfterCommitID:  "commit456",
+				DiffStyle:      "split",
+				PullIssueIndex: 42,
+			},
+			expectContains: []string{
+				"octicon-fold-down",
+				"octicon-fold-up",
+				"direction=down",
+				"direction=up",
+				`data-hidden-comment-ids=",200,201,"`, // use leading and trailing commas to ensure exact match by CSS selector `attr*=",id,"`
+				"pull_issue_index=42",
+				"2 hidden comment(s)",
+			},
+		},
+		{
+			name: "no hidden comments",
+			line: &DiffLine{
+				Type: DiffLineSection,
+				SectionInfo: &DiffLineSectionInfo{
+					LastRightIdx:     10,
+					RightIdx:         20,
+					LeftIdx:          10,
+					LastLeftIdx:      5,
+					LeftHunkSize:     5,
+					RightHunkSize:    5,
+					HiddenCommentIDs: nil,
+				},
+			},
+			fileNameHash: "ghi789",
+			data: &DiffBlobExcerptData{
+				BaseLink:      "/repo/blob_excerpt",
+				AfterCommitID: "commit789",
+			},
+			expectContains: []string{
+				"code-expander-button",
+			},
+			expectNotContain: []string{
+				"code-comment-more",
+			},
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			result := tt.line.RenderBlobExcerptButtons(tt.fileNameHash, tt.data)
+			resultStr := string(result)
+
+			for _, expected := range tt.expectContains {
+				assert.Contains(t, resultStr, expected, "Expected to contain: %s", expected)
+			}
+
+			for _, notExpected := range tt.expectNotContain {
+				assert.NotContains(t, resultStr, notExpected, "Expected NOT to contain: %s", notExpected)
+			}
+		})
+	}
+}
diff --git a/services/pull/review.go b/services/pull/review.go
index 357a816593..3977e351ca 100644
--- a/services/pull/review.go
+++ b/services/pull/review.go
@@ -22,6 +22,7 @@ import (
 	"code.gitea.io/gitea/modules/optional"
 	"code.gitea.io/gitea/modules/setting"
 	"code.gitea.io/gitea/modules/util"
+	"code.gitea.io/gitea/services/gitdiff"
 	notify_service "code.gitea.io/gitea/services/notify"
 )
 
@@ -283,6 +284,15 @@ func createCodeComment(ctx context.Context, doer *user_model.User, repo *repo_mo
 			log.Error("Error whilst generating patch: %v", err)
 			return nil, err
 		}
+
+		// If patch is still empty (unchanged line), generate code context
+		if patch == "" && commitID != "" {
+			patch, err = gitdiff.GeneratePatchForUnchangedLine(gitRepo, commitID, treePath, line, setting.UI.CodeCommentLines)
+			if err != nil {
+				// Log the error but don't fail comment creation
+				log.Debug("Unable to generate patch for unchanged line (file=%s, line=%d, commit=%s): %v", treePath, line, commitID, err)
+			}
+		}
 	}
 	return issues_model.CreateComment(ctx, &issues_model.CreateCommentOptions{
 		Type:        issues_model.CommentTypeCode,
diff --git a/templates/repo/diff/blob_excerpt.tmpl b/templates/repo/diff/blob_excerpt.tmpl
index 4089d8fb33..c9aac6d61d 100644
--- a/templates/repo/diff/blob_excerpt.tmpl
+++ b/templates/repo/diff/blob_excerpt.tmpl
@@ -1,28 +1,10 @@
-{{$blobExcerptLink := print $.RepoLink (Iif $.PageIsWiki "/wiki" "") "/blob_excerpt/" (PathEscape $.AfterCommitID) (QueryBuild "?" "anchor" $.Anchor)}}
+{{$diffBlobExcerptData := .DiffBlobExcerptData}}
+{{$canCreateComment := and ctx.RootData.SignedUserID $diffBlobExcerptData.PullIssueIndex}}
 {{if $.IsSplitStyle}}
 	{{range $k, $line := $.section.Lines}}
-	<tr class="{{.GetHTMLDiffLineType}}-code nl-{{$k}} ol-{{$k}} line-expanded">
+	<tr class="{{.GetHTMLDiffLineType}}-code nl-{{$k}} ol-{{$k}} line-expanded" data-line-type="{{.GetHTMLDiffLineType}}">
 		{{if eq .GetType 4}}
-			{{$expandDirection := $line.GetExpandDirection}}
-			<td class="lines-num lines-num-old" data-line-num="{{if $line.LeftIdx}}{{$line.LeftIdx}}{{end}}">
-				<div class="code-expander-buttons" data-expand-direction="{{$expandDirection}}">
-				{{if or (eq $expandDirection 3) (eq $expandDirection 5)}}
-					<button class="code-expander-button" hx-target="closest tr" hx-get="{{$blobExcerptLink}}&{{$line.GetBlobExcerptQuery}}&style=split&direction=down">
-						{{svg "octicon-fold-down"}}
-					</button>
-				{{end}}
-				{{if or (eq $expandDirection 3) (eq $expandDirection 4)}}
-					<button class="code-expander-button" hx-target="closest tr" hx-get="{{$blobExcerptLink}}&{{$line.GetBlobExcerptQuery}}&style=split&direction=up">
-						{{svg "octicon-fold-up"}}
-					</button>
-				{{end}}
-				{{if eq $expandDirection 2}}
-					<button class="code-expander-button" hx-target="closest tr" hx-get="{{$blobExcerptLink}}&{{$line.GetBlobExcerptQuery}}&style=split">
-						{{svg "octicon-fold"}}
-					</button>
-				{{end}}
-				</div>
-			</td>
+			<td class="lines-num lines-num-old">{{$line.RenderBlobExcerptButtons $.FileNameHash $diffBlobExcerptData}}</td>
 			<td colspan="7" class="lines-code lines-code-old">
 				{{- $inlineDiff := $.section.GetComputedInlineDiffFor $line ctx.Locale -}}
 				{{- template "repo/diff/section_code" dict "diff" $inlineDiff -}}
@@ -33,6 +15,12 @@
 			<td class="lines-escape lines-escape-old">{{if and $line.LeftIdx $inlineDiff.EscapeStatus.Escaped}}<button class="toggle-escape-button btn interact-bg" title="{{template "repo/diff/escape_title" dict "diff" $inlineDiff}}"></button>{{end}}</td>
 			<td class="lines-type-marker lines-type-marker-old">{{if $line.LeftIdx}}<span class="tw-font-mono" data-type-marker=""></span>{{end}}</td>
 			<td class="lines-code lines-code-old">
+				{{/* ATTENTION: BLOB-EXCERPT-COMMENT-RIGHT: here it intentially use "right" side to comment, because the backend code depends on the assumption that the comment only happens on right side*/}}
+				{{- if and $canCreateComment $line.RightIdx -}}
+					<button type="button" aria-label="{{ctx.Locale.Tr "repo.diff.comment.add_line_comment"}}" class="ui primary button add-code-comment add-code-comment-right{{if (not $line.CanComment)}} tw-invisible{{end}}" data-side="right" data-idx="{{$line.RightIdx}}">
+						{{- svg "octicon-plus" -}}
+					</button>
+				{{- end -}}
 				{{- if $line.LeftIdx -}}
 					{{- template "repo/diff/section_code" dict "diff" $inlineDiff -}}
 				{{- else -}}
@@ -43,6 +31,11 @@
 			<td class="lines-escape lines-escape-new">{{if and $line.RightIdx $inlineDiff.EscapeStatus.Escaped}}<button class="toggle-escape-button btn interact-bg" title="{{template "repo/diff/escape_title" dict "diff" $inlineDiff}}"></button>{{end}}</td>
 			<td class="lines-type-marker lines-type-marker-new">{{if $line.RightIdx}}<span class="tw-font-mono" data-type-marker=""></span>{{end}}</td>
 			<td class="lines-code lines-code-new">
+				{{- if and $canCreateComment $line.RightIdx -}}
+					<button type="button" aria-label="{{ctx.Locale.Tr "repo.diff.comment.add_line_comment"}}" class="ui primary button add-code-comment add-code-comment-right{{if (not $line.CanComment)}} tw-invisible{{end}}" data-side="right" data-idx="{{$line.RightIdx}}">
+						{{- svg "octicon-plus" -}}
+					</button>
+				{{- end -}}
 				{{- if $line.RightIdx -}}
 					{{- template "repo/diff/section_code" dict "diff" $inlineDiff -}}
 				{{- else -}}
@@ -51,31 +44,26 @@
 			</td>
 		{{end}}
 	</tr>
+	{{if $line.Comments}}
+		<tr class="add-comment" data-line-type="{{.GetHTMLDiffLineType}}">
+			<td class="add-comment-left" colspan="4">
+				{{if eq $line.GetCommentSide "previous"}}
+					{{template "repo/diff/conversation" dict "." $ "comments" $line.Comments}}
+				{{end}}
+			</td>
+			<td class="add-comment-right" colspan="4">
+				{{if eq $line.GetCommentSide "proposed"}}
+					{{template "repo/diff/conversation" dict "." $ "comments" $line.Comments}}
+				{{end}}
+			</td>
+		</tr>
+	{{end}}
 	{{end}}
 {{else}}
 	{{range $k, $line := $.section.Lines}}
-	<tr class="{{.GetHTMLDiffLineType}}-code nl-{{$k}} ol-{{$k}} line-expanded">
+	<tr class="{{.GetHTMLDiffLineType}}-code nl-{{$k}} ol-{{$k}} line-expanded" data-line-type="{{.GetHTMLDiffLineType}}">
 		{{if eq .GetType 4}}
-			{{$expandDirection := $line.GetExpandDirection}}
-			<td colspan="2" class="lines-num">
-				<div class="code-expander-buttons" data-expand-direction="{{$expandDirection}}">
-					{{if or (eq $expandDirection 3) (eq $expandDirection 5)}}
-						<button class="code-expander-button" hx-target="closest tr" hx-get="{{$blobExcerptLink}}&{{$line.GetBlobExcerptQuery}}&style=unified&direction=down">
-							{{svg "octicon-fold-down"}}
-						</button>
-					{{end}}
-					{{if or (eq $expandDirection 3) (eq $expandDirection 4)}}
-						<button class="code-expander-button" hx-target="closest tr" hx-get="{{$blobExcerptLink}}&{{$line.GetBlobExcerptQuery}}&style=unified&direction=up">
-							{{svg "octicon-fold-up"}}
-						</button>
-					{{end}}
-					{{if eq $expandDirection 2}}
-						<button class="code-expander-button" hx-target="closest tr" hx-get="{{$blobExcerptLink}}&{{$line.GetBlobExcerptQuery}}&style=unified">
-							{{svg "octicon-fold"}}
-						</button>
-					{{end}}
-				</div>
-			</td>
+			<td colspan="2" class="lines-num">{{$line.RenderBlobExcerptButtons $.FileNameHash $diffBlobExcerptData}}</td>
 		{{else}}
 			<td class="lines-num lines-num-old" data-line-num="{{if $line.LeftIdx}}{{$line.LeftIdx}}{{end}}"><span rel="{{if $line.LeftIdx}}diff-{{$.FileNameHash}}L{{$line.LeftIdx}}{{end}}"></span></td>
 			<td class="lines-num lines-num-new" data-line-num="{{if $line.RightIdx}}{{$line.RightIdx}}{{end}}"><span rel="{{if $line.RightIdx}}diff-{{$.FileNameHash}}R{{$line.RightIdx}}{{end}}"></span></td>
@@ -83,7 +71,21 @@
 		{{$inlineDiff := $.section.GetComputedInlineDiffFor $line ctx.Locale}}
 		<td class="lines-escape">{{if $inlineDiff.EscapeStatus.Escaped}}<button class="toggle-escape-button btn interact-bg" title="{{template "repo/diff/escape_title" dict "diff" $inlineDiff}}"></button>{{end}}</td>
 		<td class="lines-type-marker"><span class="tw-font-mono" data-type-marker="{{$line.GetLineTypeMarker}}"></span></td>
-		<td class="lines-code{{if (not $line.RightIdx)}} lines-code-old{{end}}"><code {{if $inlineDiff.EscapeStatus.Escaped}}class="code-inner has-escaped" title="{{template "repo/diff/escape_title" dict "diff" $inlineDiff}}"{{else}}class="code-inner"{{end}}>{{$inlineDiff.Content}}</code></td>
+		<td class="lines-code{{if (not $line.RightIdx)}} lines-code-old{{end}}">
+			{{- if and $canCreateComment -}}
+				<button type="button" aria-label="{{ctx.Locale.Tr "repo.diff.comment.add_line_comment"}}" class="ui primary button add-code-comment add-code-comment-{{if $line.RightIdx}}right{{else}}left{{end}}{{if (not $line.CanComment)}} tw-invisible{{end}}" data-side="{{if $line.RightIdx}}right{{else}}left{{end}}" data-idx="{{if $line.RightIdx}}{{$line.RightIdx}}{{else}}{{$line.LeftIdx}}{{end}}">
+					{{- svg "octicon-plus" -}}
+				</button>
+			{{- end -}}
+			<code {{if $inlineDiff.EscapeStatus.Escaped}}class="code-inner has-escaped" title="{{template "repo/diff/escape_title" dict "diff" $inlineDiff}}"{{else}}class="code-inner"{{end}}>{{$inlineDiff.Content}}</code>
+		</td>
 	</tr>
+	{{if $line.Comments}}
+		<tr class="add-comment" data-line-type="{{.GetHTMLDiffLineType}}">
+			<td class="add-comment-left add-comment-right" colspan="5">
+				{{template "repo/diff/conversation" dict "." $ "comments" $line.Comments}}
+			</td>
+		</tr>
+	{{end}}
 	{{end}}
 {{end}}
diff --git a/templates/repo/diff/section_split.tmpl b/templates/repo/diff/section_split.tmpl
index 9953db5eb2..ab23b1b934 100644
--- a/templates/repo/diff/section_split.tmpl
+++ b/templates/repo/diff/section_split.tmpl
@@ -1,5 +1,5 @@
 {{$file := .file}}
-{{$blobExcerptLink := print (or ctx.RootData.CommitRepoLink ctx.RootData.RepoLink) (Iif $.root.PageIsWiki "/wiki" "") "/blob_excerpt/" (PathEscape $.root.AfterCommitID) "?"}}
+{{$diffBlobExcerptData := $.root.DiffBlobExcerptData}}
 <colgroup>
 	<col width="50">
 	<col width="10">
@@ -16,26 +16,8 @@
 		{{if or (ne .GetType 2) (not $hasmatch)}}
 			<tr class="{{.GetHTMLDiffLineType}}-code nl-{{$k}} ol-{{$k}}" data-line-type="{{.GetHTMLDiffLineType}}">
 				{{if eq .GetType 4}}
-					{{$expandDirection := $line.GetExpandDirection}}
-					<td class="lines-num lines-num-old">
-						<div class="code-expander-buttons" data-expand-direction="{{$expandDirection}}">
-						{{if or (eq $expandDirection 3) (eq $expandDirection 5)}}
-							<button class="code-expander-button" hx-target="closest tr" hx-get="{{$blobExcerptLink}}&{{$line.GetBlobExcerptQuery}}&style=split&direction=down&&anchor=diff-{{$file.NameHash}}K{{$line.SectionInfo.RightIdx}}">
-								{{svg "octicon-fold-down"}}
-							</button>
-						{{end}}
-						{{if or (eq $expandDirection 3) (eq $expandDirection 4)}}
-							<button class="code-expander-button" hx-target="closest tr" hx-get="{{$blobExcerptLink}}&{{$line.GetBlobExcerptQuery}}&style=split&direction=up&anchor=diff-{{$file.NameHash}}K{{$line.SectionInfo.RightIdx}}">
-								{{svg "octicon-fold-up"}}
-							</button>
-						{{end}}
-						{{if eq $expandDirection 2}}
-							<button class="code-expander-button" hx-target="closest tr" hx-get="{{$blobExcerptLink}}&{{$line.GetBlobExcerptQuery}}&style=split&anchor=diff-{{$file.NameHash}}K{{$line.SectionInfo.RightIdx}}">
-								{{svg "octicon-fold"}}
-							</button>
-						{{end}}
-						</div>
-					</td>{{$inlineDiff := $section.GetComputedInlineDiffFor $line ctx.Locale}}
+					{{$inlineDiff := $section.GetComputedInlineDiffFor $line ctx.Locale}}
+					<td class="lines-num lines-num-old">{{$line.RenderBlobExcerptButtons $file.NameHash $diffBlobExcerptData}}</td>
 					<td class="lines-escape lines-escape-old">{{if $inlineDiff.EscapeStatus.Escaped}}<button class="toggle-escape-button btn interact-bg" title="{{template "repo/diff/escape_title" dict "diff" $inlineDiff}}"></button>{{end}}</td>
 					<td colspan="6" class="lines-code lines-code-old">{{template "repo/diff/section_code" dict "diff" $inlineDiff}}</td>
 				{{else if and (eq .GetType 3) $hasmatch}}{{/* DEL */}}
diff --git a/templates/repo/diff/section_unified.tmpl b/templates/repo/diff/section_unified.tmpl
index cb612bc27c..908b14656e 100644
--- a/templates/repo/diff/section_unified.tmpl
+++ b/templates/repo/diff/section_unified.tmpl
@@ -1,7 +1,6 @@
 {{$file := .file}}
-{{$repoLink := or ctx.RootData.CommitRepoLink ctx.RootData.RepoLink}}
-{{$afterCommitID := or $.root.AfterCommitID "no-after-commit-id"}}{{/* this tmpl is also used by the PR Conversation page, so the "AfterCommitID" may not exist */}}
-{{$blobExcerptLink := print $repoLink (Iif $.root.PageIsWiki "/wiki" "") "/blob_excerpt/" (PathEscape $afterCommitID) "?"}}
+{{/* this tmpl is also used by the PR Conversation page, so the "AfterCommitID" and "DiffBlobExcerptData" may not exist */}}
+{{$diffBlobExcerptData := $.root.DiffBlobExcerptData}}
 <colgroup>
 	<col width="50">
 	<col width="50">
@@ -14,26 +13,7 @@
 		<tr class="{{.GetHTMLDiffLineType}}-code nl-{{$k}} ol-{{$k}}" data-line-type="{{.GetHTMLDiffLineType}}">
 			{{if eq .GetType 4}}
 				{{if $.root.AfterCommitID}}
-					{{$expandDirection := $line.GetExpandDirection}}
-					<td colspan="2" class="lines-num">
-						<div class="code-expander-buttons" data-expand-direction="{{$expandDirection}}">
-							{{if or (eq $expandDirection 3) (eq $expandDirection 5)}}
-								<button class="code-expander-button" hx-target="closest tr" hx-get="{{$blobExcerptLink}}&{{$line.GetBlobExcerptQuery}}&style=unified&direction=down&anchor=diff-{{$file.NameHash}}K{{$line.SectionInfo.RightIdx}}">
-									{{svg "octicon-fold-down"}}
-								</button>
-							{{end}}
-							{{if or (eq $expandDirection 3) (eq $expandDirection 4)}}
-								<button class="code-expander-button" hx-target="closest tr" hx-get="{{$blobExcerptLink}}&{{$line.GetBlobExcerptQuery}}&style=unified&direction=up&anchor=diff-{{$file.NameHash}}K{{$line.SectionInfo.RightIdx}}">
-									{{svg "octicon-fold-up"}}
-								</button>
-							{{end}}
-							{{if eq $expandDirection 2}}
-								<button class="code-expander-button" hx-target="closest tr" hx-get="{{$blobExcerptLink}}&{{$line.GetBlobExcerptQuery}}&style=unified&anchor=diff-{{$file.NameHash}}K{{$line.SectionInfo.RightIdx}}">
-									{{svg "octicon-fold"}}
-								</button>
-							{{end}}
-						</div>
-					</td>
+					<td colspan="2" class="lines-num">{{$line.RenderBlobExcerptButtons $file.NameHash $diffBlobExcerptData}}</td>
 				{{else}}
 					{{/* for code file preview page or comment diffs on pull comment pages, do not show the expansion arrows */}}
 					<td colspan="2" class="lines-num"></td>
diff --git a/templates/repo/issue/view_content/conversation.tmpl b/templates/repo/issue/view_content/conversation.tmpl
index 189b9d6259..01261b0a56 100644
--- a/templates/repo/issue/view_content/conversation.tmpl
+++ b/templates/repo/issue/view_content/conversation.tmpl
@@ -1,3 +1,8 @@
+{{/* FIXME: DIFF-CONVERSATION-DATA: in the future this template should be refactor to avoid called by {{... "." $}}
+At the moment, two kinds of request handler call this template:
+* ExcerptBlob -> blob_excerpt.tmpl -> this
+* Other compare and diff pages -> ... -> {section_unified.tmpl|section_split.tmpl} -> this)
+The variables in "ctx.Data" are different in each case, making this template fragile, hard to read and maintain. */}}
 {{if len .comments}}
 	{{$comment := index .comments 0}}
 	{{$invalid := $comment.Invalidated}}
diff --git a/web_src/css/review.css b/web_src/css/review.css
index 23383c051c..39916d1bd8 100644
--- a/web_src/css/review.css
+++ b/web_src/css/review.css
@@ -115,6 +115,23 @@
   color: var(--color-text);
 }
 
+.code-expander-buttons {
+  position: relative;
+}
+
+.code-expander-buttons .code-comment-more {
+  position: absolute;
+  line-height: 12px;
+  padding: 2px 4px;
+  font-size: 10px;
+  background-color: var(--color-primary);
+  color: var(--color-primary-contrast);
+  border-radius: 8px !important;
+  left: -12px;
+  top: 6px;
+  text-align: center;
+}
+
 .code-expander-button {
   border: none;
   color: var(--color-text-light);
@@ -127,8 +144,8 @@
   flex: 1;
 }
 
-/* expand direction 3 is both ways with two buttons */
-.code-expander-buttons[data-expand-direction="3"] .code-expander-button {
+/* expand direction "updown" is both ways with two buttons */
+.code-expander-buttons[data-expand-direction="updown"] .code-expander-button {
   height: 18px;
 }
 
diff --git a/web_src/js/features/repo-diff.ts b/web_src/js/features/repo-diff.ts
index bde7ec0324..24d937a252 100644
--- a/web_src/js/features/repo-diff.ts
+++ b/web_src/js/features/repo-diff.ts
@@ -9,7 +9,7 @@ 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} from '../utils.ts';
+import {parseDom, sleep} from '../utils.ts';
 import {registerGlobalSelectorFunc} from '../modules/observer.ts';
 
 const {i18n} = window.config;
@@ -218,21 +218,46 @@ function initRepoDiffShowMore() {
   });
 }
 
-async function loadUntilFound() {
-  const hashTargetSelector = window.location.hash;
-  if (!hashTargetSelector.startsWith('#diff-') && !hashTargetSelector.startsWith('#issuecomment-')) {
-    return;
-  }
+async function onLocationHashChange() {
+  // try to scroll to the target element by the current hash
+  const currentHash = window.location.hash;
+  if (!currentHash.startsWith('#diff-') && !currentHash.startsWith('#issuecomment-')) return;
 
-  while (true) {
+  // avoid reentrance when we are changing the hash to scroll and trigger ":target" selection
+  const attrAutoScrollRunning = 'data-auto-scroll-running';
+  if (document.body.hasAttribute(attrAutoScrollRunning)) return;
+
+  const targetElementId = currentHash.substring(1);
+  while (currentHash === window.location.hash) {
     // use getElementById to avoid querySelector throws an error when the hash is invalid
     // eslint-disable-next-line unicorn/prefer-query-selector
-    const targetElement = document.getElementById(hashTargetSelector.substring(1));
+    const targetElement = document.getElementById(targetElementId);
     if (targetElement) {
+      // need to change hash to re-trigger ":target" CSS selector, let's manually scroll to it
       targetElement.scrollIntoView();
+      document.body.setAttribute(attrAutoScrollRunning, 'true');
+      window.location.hash = '';
+      window.location.hash = currentHash;
+      setTimeout(() => document.body.removeAttribute(attrAutoScrollRunning), 0);
       return;
     }
 
+    // If looking for a hidden comment, try to expand the section that contains it
+    const issueCommentPrefix = '#issuecomment-';
+    if (currentHash.startsWith(issueCommentPrefix)) {
+      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
+        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
+        continue; // Try again to find the element
+      }
+    }
+
     // the button will be refreshed after each "load more", so query it every time
     const showMoreButton = document.querySelector('#diff-show-more-files');
     if (!showMoreButton) {
@@ -246,8 +271,8 @@ async function loadUntilFound() {
 }
 
 function initRepoDiffHashChangeListener() {
-  window.addEventListener('hashchange', loadUntilFound);
-  loadUntilFound();
+  window.addEventListener('hashchange', onLocationHashChange);
+  onLocationHashChange();
 }
 
 export function initRepoDiffView() {