feat(issue): add attachment read downloads (#218)

- Add a read-only `attachment_read` tool for issue and issue comment attachments.
- Use the existing Gitea SDK attachment metadata APIs for `list` and `get`.
- Add authenticated `/attachments/{uuid}` downloads in the MCP server for `download`, with small image inline results and streamed file downloads for larger content.
- Add `-max-inline-attachment-bytes` / `GITEA_MAX_INLINE_ATTACHMENT_BYTES` to configure inline image limits.
- Update the tool tables in all README variants.

Refs: #209

Reviewed-on: https://gitea.com/gitea/gitea-mcp/pulls/218
Reviewed-by: Lunny Xiao <xiaolunwen@gmail.com>
Co-authored-by: yp05327 <576951401@qq.com>

README.md

@@ -151,6 +151,7 @@ Once configured, try `list all my repositories` in the chat box.
 | package_read                 | Packages     | Read   | Read package registry: list packages, list versions, or get a version                      |
 | package_write                | Packages     | Write  | Delete a package version (irreversible)                                                    |
 | list_issues                  | Issue        | Read   | List repository issues                                                                     |
+| attachment_read              | Issue        | Read   | Read issue/comment attachments: list metadata, get metadata, or download content           |
 | issue_read                   | Issue        | Read   | Read issue: details, comments, or labels                                                   |
 | issue_write                  | Issue        | Write  | Write issues: create, update, manage comments and labels                                   |
 | list_pull_requests           | Pull Request | Read   | List repository pull requests                                                              |

README.zh-cn.md

@@ -151,6 +151,7 @@ Cursor 等客户端可使用 stdio 命令：
 | package_read                 | 软件包   | 读取 | 读取软件包注册表：列出软件包、列出版本或获取某个版本                 |
 | package_write                | 软件包   | 写入 | 删除软件包版本（不可恢复）                                           |
 | list_issues                  | 问题     | 读取 | 列出仓库问题                                                         |
+| attachment_read              | 问题     | 读取 | 读取问题/评论附件：列出元数据、获取元数据或下载内容                 |
 | issue_read                   | 问题     | 读取 | 读取问题：详情、评论或标签                                           |
 | issue_write                  | 问题     | 写入 | 写入问题：创建、更新、管理评论和标签                                 |
 | list_pull_requests           | 拉取请求 | 读取 | 列出仓库拉取请求                                                     |

README.zh-tw.md

@@ -151,6 +151,7 @@ Cursor 等客戶端可使用 stdio 命令：
 | package_read                 | 軟體套件 | 讀取 | 讀取軟體套件註冊表：列出套件、列出版本或取得某個版本                 |
 | package_write                | 軟體套件 | 寫入 | 刪除軟體套件版本（不可復原）                                         |
 | list_issues                  | 問題     | 讀取 | 列出倉庫問題                                                         |
+| attachment_read              | 問題     | 讀取 | 讀取問題/評論附件：列出中繼資料、取得中繼資料或下載內容             |
 | issue_read                   | 問題     | 讀取 | 讀取問題：詳情、評論或標籤                                           |
 | issue_write                  | 問題     | 寫入 | 寫入問題：創建、更新、管理評論和標籤                                 |
 | list_pull_requests           | 拉取請求 | 讀取 | 列出倉庫拉取請求                                                     |

cmd/cmd.go

@@ -4,7 +4,9 @@ import (
 	"context"
 	"flag"
 	"fmt"
+	"io"
 	"os"
+	"strconv"
 	"strings"
 	"text/tabwriter"
 
@@ -19,34 +21,51 @@ var (
 	token                           string
 	tools                           string
 	version                         bool
+	maxInlineAttachmentBytes        int
+	maxInlineAttachmentBytesFlagSet bool
+	osExit                          = os.Exit
 )
 
 func init() {
-	flag.StringVar(&flagPkg.Mode, "t", "stdio", "")
-	flag.StringVar(&flagPkg.Mode, "transport", "stdio", "")
-	flag.StringVar(&host, "H", os.Getenv("GITEA_HOST"), "")
-	flag.StringVar(&host, "host", os.Getenv("GITEA_HOST"), "")
-	flag.IntVar(&port, "p", 8080, "")
-	flag.IntVar(&port, "port", 8080, "")
-	flag.StringVar(&token, "T", "", "")
-	flag.StringVar(&token, "token", "", "")
-	flag.BoolVar(&flagPkg.ReadOnly, "r", false, "")
-	flag.BoolVar(&flagPkg.ReadOnly, "read-only", false, "")
-	defaultTools := os.Getenv("GITEA_TOOLS")
-	flag.StringVar(&tools, "O", defaultTools, "")
-	flag.StringVar(&tools, "tools", defaultTools, "")
-	flag.BoolVar(&flagPkg.Debug, "d", false, "")
-	flag.BoolVar(&flagPkg.Debug, "debug", false, "")
-	flag.BoolVar(&flagPkg.Insecure, "k", false, "")
-	flag.BoolVar(&flagPkg.Insecure, "insecure", false, "")
-	flag.BoolVar(&version, "v", false, "")
-	flag.BoolVar(&version, "version", false, "")
+	initFlagSet(flag.CommandLine, os.Args[1:], os.Getenv, os.ReadFile, os.Stderr)
+}
 
-	flag.Usage = func() {
-		w := tabwriter.NewWriter(os.Stderr, 0, 0, 3, ' ', 0)
-		fmt.Fprintln(os.Stderr, "Usage: gitea-mcp [options]")
-		fmt.Fprintln(os.Stderr)
-		fmt.Fprintln(os.Stderr, "Options:")
+func initFlagSet(fs *flag.FlagSet, args []string, getenv func(string) string, readFile func(string) ([]byte, error), stderr io.Writer) {
+	fs.StringVar(&flagPkg.Mode, "t", "stdio", "")
+	fs.StringVar(&flagPkg.Mode, "transport", "stdio", "")
+	fs.StringVar(&host, "H", getenv("GITEA_HOST"), "")
+	fs.StringVar(&host, "host", getenv("GITEA_HOST"), "")
+	fs.IntVar(&port, "p", 8080, "")
+	fs.IntVar(&port, "port", 8080, "")
+	fs.StringVar(&token, "T", "", "")
+	fs.StringVar(&token, "token", "", "")
+	fs.BoolVar(&flagPkg.ReadOnly, "r", false, "")
+	fs.BoolVar(&flagPkg.ReadOnly, "read-only", false, "")
+	defaultTools := getenv("GITEA_TOOLS")
+	fs.StringVar(&tools, "O", defaultTools, "")
+	fs.StringVar(&tools, "tools", defaultTools, "")
+	fs.BoolVar(&flagPkg.Debug, "d", false, "")
+	fs.BoolVar(&flagPkg.Debug, "debug", false, "")
+	fs.BoolVar(&flagPkg.Insecure, "k", false, "")
+	fs.BoolVar(&flagPkg.Insecure, "insecure", false, "")
+	fs.BoolVar(&version, "v", false, "")
+	fs.BoolVar(&version, "version", false, "")
+	maxInlineAttachmentBytes = 5 * 1024 * 1024
+	fs.Func("max-inline-attachment-bytes", "", func(val string) error {
+		parsed, err := strconv.Atoi(val)
+		if err != nil || parsed < 0 {
+			return fmt.Errorf("invalid value %q", val)
+		}
+		maxInlineAttachmentBytes = parsed
+		maxInlineAttachmentBytesFlagSet = true
+		return nil
+	})
+
+	fs.Usage = func() {
+		w := tabwriter.NewWriter(stderr, 0, 0, 3, ' ', 0)
+		fmt.Fprintln(stderr, "Usage: gitea-mcp [options]")
+		fmt.Fprintln(stderr)
+		fmt.Fprintln(stderr, "Options:")
 		fmt.Fprintf(w, "  -t, -transport <type>\tTransport type: stdio or http (default: stdio)\n")
 		fmt.Fprintf(w, "  -H, -host <url>\tGitea host URL (default: https://gitea.com)\n")
 		fmt.Fprintf(w, "  -p, -port <number>\tHTTP server port (default: 8080)\n")
@@ -55,6 +74,7 @@ func init() {
 		fmt.Fprintf(w, "  -O, -tools <names>\tComma-separated list of tool names to expose\n")
 		fmt.Fprintf(w, "  -d, -debug\tEnable debug mode\n")
 		fmt.Fprintf(w, "  -k, -insecure\tIgnore TLS certificate errors\n")
+		fmt.Fprintf(w, "  -max-inline-attachment-bytes <bytes>\tInline image attachments up to this size (default: 5242880)\n")
 		fmt.Fprintf(w, "  -v, -version\tPrint version and exit\n")
 		fmt.Fprintln(w)
 		fmt.Fprintln(w, "Environment variables:")
@@ -63,13 +83,14 @@ func init() {
 		fmt.Fprintf(w, "  GITEA_DEBUG\tSet to 'true' for debug mode\n")
 		fmt.Fprintf(w, "  GITEA_HOST\tOverride Gitea host URL\n")
 		fmt.Fprintf(w, "  GITEA_INSECURE\tSet to 'true' to ignore TLS errors\n")
+		fmt.Fprintf(w, "  GITEA_MAX_INLINE_ATTACHMENT_BYTES\tOverride inline image attachment size limit in bytes\n")
 		fmt.Fprintf(w, "  GITEA_READONLY\tSet to 'true' for read-only mode\n")
 		fmt.Fprintf(w, "  GITEA_TOOLS\tComma-separated list of tool names to expose\n")
 		fmt.Fprintf(w, "  MCP_MODE\tOverride transport mode\n")
-		w.Flush()
+		_ = w.Flush()
 	}
 
-	flag.Parse()
+	_ = fs.Parse(args)
 
 	flagPkg.Host = host
 	if flagPkg.Host == "" {
@@ -77,27 +98,27 @@ func init() {
 	}
 
 	flagPkg.Port = port
+	flagPkg.MaxInlineAttachmentBytes = maxInlineAttachmentBytes
 
 	flagPkg.Token = token
 	if flagPkg.Token == "" {
-		flagPkg.Token = os.Getenv("GITEA_ACCESS_TOKEN")
+		flagPkg.Token = getenv("GITEA_ACCESS_TOKEN")
 	}
 	if flagPkg.Token == "" {
-		if tokenFile := os.Getenv("GITEA_ACCESS_TOKEN_FILE"); tokenFile != "" {
-			data, err := os.ReadFile(tokenFile)
+		if tokenFile := getenv("GITEA_ACCESS_TOKEN_FILE"); tokenFile != "" {
+			data, err := readFile(tokenFile)
 			if err != nil {
-				fmt.Fprintf(os.Stderr, "error reading GITEA_ACCESS_TOKEN_FILE: %v\n", err)
-				os.Exit(1)
+				fmt.Fprintf(stderr, "error reading GITEA_ACCESS_TOKEN_FILE: %v\n", err)
+				osExit(1)
 			}
 			flagPkg.Token = strings.TrimRight(string(data), "\r\n")
 		}
 	}
 
-	if os.Getenv("MCP_MODE") != "" {
-		flagPkg.Mode = os.Getenv("MCP_MODE")
+	if getenv("MCP_MODE") != "" {
+		flagPkg.Mode = getenv("MCP_MODE")
 	}
-
-	if os.Getenv("GITEA_READONLY") == "true" {
+	if getenv("GITEA_READONLY") == "true" {
 		flagPkg.ReadOnly = true
 	}
 
@@ -110,15 +131,22 @@ func init() {
 	if len(allowed) > 0 {
 		flagPkg.AllowedTools = allowed
 	}
-
-	if os.Getenv("GITEA_DEBUG") == "true" {
+	if getenv("GITEA_DEBUG") == "true" {
 		flagPkg.Debug = true
 	}
-
-	// Set insecure mode based on environment variable
-	if os.Getenv("GITEA_INSECURE") == "true" {
+	if getenv("GITEA_INSECURE") == "true" {
 		flagPkg.Insecure = true
 	}
+	if !maxInlineAttachmentBytesFlagSet {
+		if val := getenv("GITEA_MAX_INLINE_ATTACHMENT_BYTES"); val != "" {
+			parsed, err := strconv.Atoi(val)
+			if err != nil || parsed < 0 {
+				fmt.Fprintf(stderr, "invalid GITEA_MAX_INLINE_ATTACHMENT_BYTES: %q\n", val)
+				osExit(1)
+			}
+			flagPkg.MaxInlineAttachmentBytes = parsed
+		}
+	}
 }
 
 func Execute() {
@@ -126,12 +154,14 @@ func Execute() {
 		fmt.Fprintln(os.Stdout, flagPkg.Version)
 		return
 	}
-	defer log.Default().Sync() //nolint:errcheck // best-effort flush
 	if err := operation.Run(); err != nil {
 		if err == context.Canceled {
 			log.Info("Server shutdown due to context cancellation")
+			_ = log.Default().Sync() // best-effort flush
 			return
 		}
-		log.Fatalf("Run Gitea MCP Server Error: %v", err) //nolint:gocritic // intentional exit after defer
+		_ = log.Default().Sync() // best-effort flush
+		log.Fatalf("Run Gitea MCP Server Error: %v", err)
 	}
+	_ = log.Default().Sync() // best-effort flush
 }

operation/issue/attachment.go

@@ -0,0 +1,311 @@
+package issue
+
+import (
+	"bytes"
+	"context"
+	"encoding/base64"
+	"errors"
+	"fmt"
+	"io"
+	"mime"
+	"os"
+	"path/filepath"
+	"strings"
+
+	"gitea.com/gitea/gitea-mcp/pkg/annotation"
+	"gitea.com/gitea/gitea-mcp/pkg/flag"
+	"gitea.com/gitea/gitea-mcp/pkg/gitea"
+	"gitea.com/gitea/gitea-mcp/pkg/params"
+	"gitea.com/gitea/gitea-mcp/pkg/to"
+
+	gitea_sdk "gitea.dev/sdk"
+	"github.com/mark3labs/mcp-go/mcp"
+	"github.com/mark3labs/mcp-go/server"
+)
+
+const AttachmentReadToolName = "attachment_read"
+
+var AttachmentReadTool = mcp.NewTool(
+	AttachmentReadToolName,
+	mcp.WithDescription("Read issue/comment attachments: list metadata, get metadata, or download content."),
+	mcp.WithToolAnnotation(annotation.ReadOnly("Read issue or comment attachments")),
+	mcp.WithString("method", mcp.Required(), mcp.Enum("list", "get", "download")),
+	mcp.WithString("owner", mcp.Required(), mcp.Description(params.OwnerDesc)),
+	mcp.WithString("repo", mcp.Required(), mcp.Description(params.RepoDesc)),
+	mcp.WithNumber("issue_number", mcp.Description("required for issue attachment list/get or issue-scoped metadata lookup")),
+	mcp.WithNumber("comment_id", mcp.Description("required for comment attachment list/get or comment-scoped metadata lookup")),
+	mcp.WithNumber("attachment_id", mcp.Description("required for get and for download when attachment_uuid is not provided")),
+	mcp.WithString("attachment_uuid", mcp.Description("attachment UUID for direct download path lookup")),
+	mcp.WithString("output_path", mcp.Description("write the attachment to this exact path")),
+)
+
+func init() {
+	Tool.RegisterRead(server.ServerTool{Tool: AttachmentReadTool, Handler: attachmentReadFn})
+}
+
+func attachmentReadFn(ctx context.Context, req mcp.CallToolRequest) (*mcp.CallToolResult, error) {
+	method, err := params.GetString(req.GetArguments(), "method")
+	if err != nil {
+		return to.ErrorResult(err)
+	}
+	switch method {
+	case "list":
+		return listAttachmentsFn(ctx, req)
+	case "get":
+		return getAttachmentFn(ctx, req)
+	case "download":
+		return downloadAttachmentFn(ctx, req)
+	default:
+		return to.ErrorResult(fmt.Errorf("unknown method: %s", method))
+	}
+}
+
+func listAttachmentsFn(ctx context.Context, req mcp.CallToolRequest) (*mcp.CallToolResult, error) {
+	owner, repo, issueNumber, commentID, err := attachmentScopeArgs(req)
+	if err != nil {
+		return to.ErrorResult(err)
+	}
+	client, err := gitea.ClientFromContext(ctx)
+	if err != nil {
+		return to.ErrorResult(fmt.Errorf("get gitea client err: %v", err))
+	}
+	var attachments []*gitea_sdk.Attachment
+	if issueNumber > 0 {
+		attachments, _, err = client.Issues.ListIssueAttachments(ctx, owner, repo, issueNumber)
+	} else {
+		attachments, _, err = client.Issues.ListIssueCommentAttachments(ctx, owner, repo, commentID)
+	}
+	if err != nil {
+		return to.ErrorResult(fmt.Errorf("list attachments err: %v", err))
+	}
+	return to.TextResult(slimAttachments(attachments))
+}
+
+func getAttachmentFn(ctx context.Context, req mcp.CallToolRequest) (*mcp.CallToolResult, error) {
+	att, err := lookupAttachment(ctx, req)
+	if err != nil {
+		return to.ErrorResult(err)
+	}
+	return to.TextResult(slimAttachment(att))
+}
+
+func downloadAttachmentFn(ctx context.Context, req mcp.CallToolRequest) (*mcp.CallToolResult, error) {
+	owner, err := params.GetString(req.GetArguments(), "owner")
+	if err != nil {
+		return to.ErrorResult(err)
+	}
+	repo, err := params.GetString(req.GetArguments(), "repo")
+	if err != nil {
+		return to.ErrorResult(err)
+	}
+	explicitOutputPath := params.GetOptionalString(req.GetArguments(), "output_path", "")
+	attachmentUUID := strings.TrimSpace(params.GetOptionalString(req.GetArguments(), "attachment_uuid", ""))
+
+	var att *gitea_sdk.Attachment
+	if attachmentUUID == "" {
+		att, err = lookupAttachment(ctx, req)
+		if err != nil {
+			return to.ErrorResult(err)
+		}
+		attachmentUUID = strings.TrimSpace(att.UUID)
+	}
+	if attachmentUUID == "" {
+		return to.ErrorResult(errors.New("attachment_uuid or attachment metadata with uuid is required"))
+	}
+
+	name := attachmentUUID
+	if att != nil && strings.TrimSpace(att.Name) != "" {
+		name = strings.TrimSpace(att.Name)
+	}
+
+	resp, err := gitea.OpenAttachment(ctx, "/attachments/"+attachmentUUID, "*/*")
+	if err != nil {
+		return to.ErrorResult(fmt.Errorf("download attachment err: %v", err))
+	}
+	defer resp.Body.Close()
+
+	mimeType := normalizeAttachmentContentType(resp.ContentType, name)
+	if explicitOutputPath == "" && shouldInlineAttachment(att, mimeType) {
+		limited, readErr := io.ReadAll(io.LimitReader(resp.Body, int64(flag.MaxInlineAttachmentBytes)+1))
+		if readErr != nil {
+			return to.ErrorResult(fmt.Errorf("read attachment err: %v", readErr))
+		}
+		if len(limited) <= flag.MaxInlineAttachmentBytes {
+			text := fmt.Sprintf("attachment %s (%s, %d bytes, %s)", name, attachmentUUID, len(limited), mimeType)
+			return mcp.NewToolResultImage(text, base64.StdEncoding.EncodeToString(limited), mimeType), nil
+		}
+		outputPath := defaultAttachmentPath(owner, repo, name, attachmentUUID)
+		if err := os.MkdirAll(filepath.Dir(outputPath), 0o700); err != nil {
+			return to.ErrorResult(fmt.Errorf("create output dir err: %v", err))
+		}
+		reader := io.MultiReader(bytes.NewReader(limited), resp.Body)
+		written, err := gitea.WriteAttachment(reader, outputPath)
+		if err != nil {
+			return to.ErrorResult(fmt.Errorf("write attachment file err: %v", err))
+		}
+		return attachmentFileResult(att, outputPath, written, name, attachmentUUID, mimeType)
+	}
+
+	outputPath := explicitOutputPath
+	if outputPath == "" {
+		outputPath = defaultAttachmentPath(owner, repo, name, attachmentUUID)
+	}
+	if err := os.MkdirAll(filepath.Dir(outputPath), 0o700); err != nil {
+		return to.ErrorResult(fmt.Errorf("create output dir err: %v", err))
+	}
+	written, err := gitea.WriteAttachment(resp.Body, outputPath)
+	if err != nil {
+		return to.ErrorResult(fmt.Errorf("write attachment file err: %v", err))
+	}
+	return attachmentFileResult(att, outputPath, written, name, attachmentUUID, mimeType)
+}
+
+func shouldInlineAttachment(att *gitea_sdk.Attachment, mimeType string) bool {
+	if !strings.HasPrefix(mimeType, "image/") || flag.MaxInlineAttachmentBytes <= 0 {
+		return false
+	}
+	if att == nil || att.Size <= 0 {
+		return true
+	}
+	return att.Size <= int64(flag.MaxInlineAttachmentBytes)
+}
+
+func attachmentFileResult(att *gitea_sdk.Attachment, outputPath string, written int64, name, attachmentUUID, mimeType string) (*mcp.CallToolResult, error) {
+	res := map[string]any{
+		"path":         outputPath,
+		"bytes":        written,
+		"name":         name,
+		"uuid":         attachmentUUID,
+		"mime_type":    mimeType,
+		"content_type": mimeType,
+	}
+	if att != nil {
+		res["attachment_id"] = att.ID
+	}
+	return to.TextResult(res)
+}
+
+func attachmentScopeArgs(req mcp.CallToolRequest) (owner, repo string, issueNumber, commentID int64, err error) {
+	owner, err = params.GetString(req.GetArguments(), "owner")
+	if err != nil {
+		return "", "", 0, 0, err
+	}
+	repo, err = params.GetString(req.GetArguments(), "repo")
+	if err != nil {
+		return "", "", 0, 0, err
+	}
+	issueNumber = params.GetOptionalInt(req.GetArguments(), "issue_number", 0)
+	commentID = params.GetOptionalInt(req.GetArguments(), "comment_id", 0)
+	if (issueNumber > 0) == (commentID > 0) {
+		return "", "", 0, 0, errors.New("exactly one of issue_number or comment_id is required")
+	}
+	return owner, repo, issueNumber, commentID, nil
+}
+
+func lookupAttachment(ctx context.Context, req mcp.CallToolRequest) (*gitea_sdk.Attachment, error) {
+	owner, repo, issueNumber, commentID, err := attachmentScopeArgs(req)
+	if err != nil {
+		return nil, err
+	}
+	attachmentID := params.GetOptionalInt(req.GetArguments(), "attachment_id", 0)
+	if attachmentID <= 0 {
+		return nil, errors.New("attachment_id is required")
+	}
+	client, err := gitea.ClientFromContext(ctx)
+	if err != nil {
+		return nil, fmt.Errorf("get gitea client err: %v", err)
+	}
+	if issueNumber > 0 {
+		att, _, err := client.Issues.GetIssueAttachment(ctx, owner, repo, issueNumber, attachmentID)
+		if err != nil {
+			return nil, fmt.Errorf("get issue attachment err: %v", err)
+		}
+		return att, nil
+	}
+	att, _, err := client.Issues.GetIssueCommentAttachment(ctx, owner, repo, commentID, attachmentID)
+	if err != nil {
+		return nil, fmt.Errorf("get issue comment attachment err: %v", err)
+	}
+	return att, nil
+}
+
+func slimAttachments(atts []*gitea_sdk.Attachment) []map[string]any {
+	out := make([]map[string]any, 0, len(atts))
+	for _, att := range atts {
+		out = append(out, slimAttachment(att))
+	}
+	return out
+}
+
+func slimAttachment(att *gitea_sdk.Attachment) map[string]any {
+	if att == nil {
+		return nil
+	}
+	m := map[string]any{
+		"id":             att.ID,
+		"name":           att.Name,
+		"uuid":           att.UUID,
+		"size":           att.Size,
+		"download_count": att.DownloadCount,
+		"created_at":     att.Created,
+		"mime_type":      inferAttachmentMimeType(att.Name),
+	}
+	if att.DownloadURL != "" {
+		m["browser_download_url"] = att.DownloadURL
+	}
+	return m
+}
+
+func inferAttachmentMimeType(name string) string {
+	if ext := strings.ToLower(filepath.Ext(strings.TrimSpace(name))); ext != "" {
+		if mimeType := mime.TypeByExtension(ext); mimeType != "" {
+			return strings.Split(mimeType, ";")[0]
+		}
+	}
+	return "application/octet-stream"
+}
+
+func normalizeAttachmentContentType(contentType, name string) string {
+	mediaType, _, err := mime.ParseMediaType(contentType)
+	if err == nil && mediaType != "" && mediaType != "application/octet-stream" {
+		return mediaType
+	}
+	return inferAttachmentMimeType(name)
+}
+
+func defaultAttachmentPath(owner, repo, name, uuid string) string {
+	home, _ := os.UserHomeDir()
+	if home == "" {
+		home = os.TempDir()
+	}
+	filename := attachmentFilename(name, uuid)
+	ext := filepath.Ext(filename)
+	base := strings.TrimSuffix(filename, ext)
+	if uuid != "" {
+		filename = uuid
+		if base != "" && base != "attachment" {
+			filename = base + "-" + uuid
+		}
+		filename += ext
+	}
+	return filepath.Join(home, ".gitea-mcp", "attachments", safePathPart(owner), safePathPart(repo), filename)
+}
+
+func attachmentFilename(name, uuid string) string {
+	name = strings.TrimSpace(name)
+	if name != "" && !strings.ContainsAny(name, `/\\`) && name != "." && name != ".." {
+		return name
+	}
+	if uuid != "" {
+		return uuid + ".bin"
+	}
+	return "attachment.bin"
+}
+
+func safePathPart(name string) string {
+	name = strings.TrimSpace(name)
+	if name != "" && !strings.ContainsAny(name, `/\\`) && name != "." && name != ".." {
+		return name
+	}
+	return "unknown"
+}

operation/issue/attachment_test.go

@@ -0,0 +1,182 @@
+package issue
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"net/http"
+	"net/http/httptest"
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+
+	"gitea.com/gitea/gitea-mcp/pkg/flag"
+	"gitea.com/gitea/gitea-mcp/pkg/gitea"
+
+	"github.com/mark3labs/mcp-go/mcp"
+)
+
+func TestAttachmentFilename(t *testing.T) {
+	tests := []struct {
+		name string
+		file string
+		uuid string
+		want string
+	}{
+		{"uses attachment name", "screenshot.png", "abc", "screenshot.png"},
+		{"falls back for traversal", "../etc/passwd", "abc", "abc.bin"},
+		{"falls back for empty name", "", "abc", "abc.bin"},
+		{"uses generic fallback", "", "", "attachment.bin"},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got := attachmentFilename(tt.file, tt.uuid); got != tt.want {
+				t.Fatalf("attachmentFilename() = %q, want %q", got, tt.want)
+			}
+		})
+	}
+}
+
+func TestInferAttachmentMimeType(t *testing.T) {
+	if got := inferAttachmentMimeType("shot.png"); got != "image/png" {
+		t.Fatalf("inferAttachmentMimeType() = %q, want image/png", got)
+	}
+	if got := inferAttachmentMimeType("archive.unknownext"); got != "application/octet-stream" {
+		t.Fatalf("inferAttachmentMimeType() = %q, want application/octet-stream", got)
+	}
+}
+
+func TestDefaultAttachmentPath(t *testing.T) {
+	got := defaultAttachmentPath("octo", "demo", "shot.png", "uuid-1")
+	want := filepath.Join(".gitea-mcp", "attachments", "octo", "demo", "shot-uuid-1.png")
+	if !strings.HasSuffix(got, want) {
+		t.Fatalf("defaultAttachmentPath() = %q, want suffix %q", got, want)
+	}
+}
+
+func TestAttachmentReadListIssueAttachments(t *testing.T) {
+	const owner = "octo"
+	const repo = "demo"
+	handler := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		switch r.URL.Path {
+		case "/api/v1/version":
+			w.Header().Set("Content-Type", "application/json")
+			_, _ = w.Write([]byte(`{"version":"1.12.0"}`))
+		case fmt.Sprintf("/api/v1/repos/%s/%s", owner, repo):
+			w.Header().Set("Content-Type", "application/json")
+			_, _ = w.Write([]byte(`{"private":false}`))
+		case fmt.Sprintf("/api/v1/repos/%s/%s/issues/42/assets", owner, repo):
+			w.Header().Set("Content-Type", "application/json")
+			_, _ = w.Write([]byte(`[{"id":1,"name":"shot.png","uuid":"uuid-1","size":10,"download_count":2}]`))
+		default:
+			http.NotFound(w, r)
+		}
+	})
+	server := httptest.NewServer(handler)
+	defer server.Close()
+	origHost, origToken, origVersion := flag.Host, flag.Token, flag.Version
+	flag.Host, flag.Token, flag.Version = server.URL, "", "test"
+	defer func() { flag.Host, flag.Token, flag.Version = origHost, origToken, origVersion }()
+
+	res, err := attachmentReadFn(context.Background(), mcp.CallToolRequest{Params: mcp.CallToolParams{Arguments: map[string]any{
+		"method": "list", "owner": owner, "repo": repo, "issue_number": float64(42),
+	}}})
+	if err != nil {
+		t.Fatalf("attachmentReadFn() error = %v", err)
+	}
+	body := res.Content[0].(mcp.TextContent).Text
+	if !strings.Contains(body, `"mime_type":"image/png"`) || !strings.Contains(body, `"uuid":"uuid-1"`) {
+		t.Fatalf("unexpected body: %s", body)
+	}
+}
+
+func TestDownloadAttachmentRejectsRedirectLoopAtHopLimit(t *testing.T) {
+	var serverURL string
+	redirects := 0
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		if r.URL.Path != "/attachments/uuid-1" {
+			t.Fatalf("path = %s", r.URL.Path)
+		}
+		redirects++
+		http.Redirect(w, r, serverURL+"/attachments/uuid-1", http.StatusFound)
+	}))
+	defer server.Close()
+	serverURL = server.URL
+
+	origHost := flag.Host
+	flag.Host = server.URL
+	defer func() { flag.Host = origHost }()
+
+	_, _, _, err := gitea.DownloadAttachment(context.Background(), "/attachments/uuid-1", "*/*")
+	if err == nil {
+		t.Fatal("expected redirect limit error")
+	}
+	if !strings.Contains(err.Error(), "stopped after 10 redirects") {
+		t.Fatalf("unexpected error: %v", err)
+	}
+	if redirects != 10 {
+		t.Fatalf("redirects = %d, want 10", redirects)
+	}
+}
+
+func TestAttachmentReadDownloadSavesLargeAttachmentToDefaultFile(t *testing.T) {
+	const owner = "octo"
+	const repo = "demo"
+	const uuid = "uuid-1"
+	const name = "large.bin"
+	payload := strings.Repeat("a", 32)
+
+	home := t.TempDir()
+	t.Setenv("HOME", home)
+
+	handler := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		switch r.URL.Path {
+		case "/api/v1/version":
+			w.Header().Set("Content-Type", "application/json")
+			_, _ = w.Write([]byte(`{"version":"1.12.0"}`))
+		case fmt.Sprintf("/api/v1/repos/%s/%s", owner, repo):
+			w.Header().Set("Content-Type", "application/json")
+			_, _ = w.Write([]byte(`{"private":false}`))
+		case fmt.Sprintf("/api/v1/repos/%s/%s/issues/42/assets/1", owner, repo):
+			w.Header().Set("Content-Type", "application/json")
+			_ = json.NewEncoder(w).Encode(map[string]any{"id": 1, "name": name, "uuid": uuid, "size": len(payload)})
+		case "/attachments/" + uuid:
+			w.Header().Set("Content-Type", "application/octet-stream")
+			_, _ = w.Write([]byte(payload))
+		default:
+			http.NotFound(w, r)
+		}
+	})
+	server := httptest.NewServer(handler)
+	defer server.Close()
+
+	origHost, origToken, origVersion, origInline := flag.Host, flag.Token, flag.Version, flag.MaxInlineAttachmentBytes
+	flag.Host, flag.Token, flag.Version = server.URL, "", "test"
+	flag.MaxInlineAttachmentBytes = 8
+	defer func() {
+		flag.Host, flag.Token, flag.Version, flag.MaxInlineAttachmentBytes = origHost, origToken, origVersion, origInline
+	}()
+
+	res, err := attachmentReadFn(context.Background(), mcp.CallToolRequest{Params: mcp.CallToolParams{Arguments: map[string]any{
+		"method": "download", "owner": owner, "repo": repo, "issue_number": float64(42), "attachment_id": float64(1),
+	}}})
+	if err != nil {
+		t.Fatalf("attachmentReadFn() error = %v", err)
+	}
+	body := res.Content[0].(mcp.TextContent).Text
+	wantPath := filepath.Join(home, ".gitea-mcp", "attachments", owner, repo, "large-uuid-1.bin")
+	if !strings.Contains(body, wantPath) {
+		t.Fatalf("result missing path %q: %s", wantPath, body)
+	}
+	data, err := os.ReadFile(wantPath)
+	if err != nil {
+		t.Fatalf("ReadFile(%q): %v", wantPath, err)
+	}
+	if string(data) != payload {
+		t.Fatalf("saved payload mismatch")
+	}
+	if !strings.Contains(body, `"bytes":32`) {
+		t.Fatalf("result missing bytes: %s", body)
+	}
+}

pkg/flag/flag.go

@@ -7,6 +7,8 @@ var (
 	Version string
 	Mode    string
 
+	MaxInlineAttachmentBytes int
+
 	Insecure     bool
 	ReadOnly     bool
 	Debug        bool

pkg/gitea/attachment_test.go

@@ -0,0 +1,208 @@
+package gitea
+
+import (
+	"context"
+	"errors"
+	"net/http"
+	"net/http/httptest"
+	"net/url"
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+
+	"gitea.com/gitea/gitea-mcp/pkg/flag"
+)
+
+func TestBuildAttachmentURLRejectsExternalURL(t *testing.T) {
+	origHost := flag.Host
+	flag.Host = "https://example.com"
+	defer func() { flag.Host = origHost }()
+
+	if _, err := buildAttachmentURL("https://evil.example.com/attachments/1"); err == nil {
+		t.Fatal("expected error for full URL attachment path")
+	}
+}
+
+func TestBuildAttachmentURLPreservesHostPathPrefix(t *testing.T) {
+	origHost := flag.Host
+	flag.Host = "https://example.com/gitea"
+	defer func() { flag.Host = origHost }()
+
+	got, err := buildAttachmentURL("/attachments/uuid-1")
+	if err != nil {
+		t.Fatalf("buildAttachmentURL() error = %v", err)
+	}
+	if got != "https://example.com/gitea/attachments/uuid-1" {
+		t.Fatalf("buildAttachmentURL() = %q", got)
+	}
+}
+
+func TestDownloadAttachmentUsesTokenAndReturnsContentType(t *testing.T) {
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		if r.URL.Path != "/attachments/uuid-1" {
+			t.Fatalf("path = %s", r.URL.Path)
+		}
+		if got := r.Header.Get("Authorization"); got != "token secret-token" {
+			t.Fatalf("Authorization = %q", got)
+		}
+		if got := r.Header.Get("Accept"); got != "*/*" {
+			t.Fatalf("Accept = %q", got)
+		}
+		w.Header().Set("Content-Type", "image/png")
+		_, _ = w.Write([]byte("png-bytes"))
+	}))
+	defer server.Close()
+
+	origHost, origToken := flag.Host, flag.Token
+	flag.Host, flag.Token = server.URL, "secret-token"
+	defer func() { flag.Host, flag.Token = origHost, origToken }()
+
+	raw, contentType, status, err := DownloadAttachment(context.Background(), "/attachments/uuid-1", "*/*")
+	if err != nil {
+		t.Fatalf("DownloadAttachment() error = %v", err)
+	}
+	if status != http.StatusOK {
+		t.Fatalf("DownloadAttachment() status = %d, want %d", status, http.StatusOK)
+	}
+	if contentType != "image/png" {
+		t.Fatalf("contentType = %q", contentType)
+	}
+	if string(raw) != "png-bytes" {
+		t.Fatalf("body = %q", string(raw))
+	}
+}
+
+func TestDownloadAttachmentRejectsCrossOriginRedirect(t *testing.T) {
+	redirected := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		t.Fatalf("cross-origin redirect should not be followed: %s", r.URL.String())
+	}))
+	defer redirected.Close()
+
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		http.Redirect(w, r, redirected.URL+"/attachments/uuid-1", http.StatusFound)
+	}))
+	defer server.Close()
+
+	origHost, origToken := flag.Host, flag.Token
+	flag.Host, flag.Token = server.URL, "secret-token"
+	defer func() { flag.Host, flag.Token = origHost, origToken }()
+
+	_, _, _, err := DownloadAttachment(context.Background(), "/attachments/uuid-1", "*/*")
+	if err == nil {
+		t.Fatal("expected error for cross-origin redirect")
+	}
+	want := "do request: Get \"" + redirected.URL + "/attachments/uuid-1\": attachment redirect changed origin"
+	if err.Error() != want {
+		t.Fatalf("unexpected error: %v", err)
+	}
+}
+
+func TestDownloadAttachmentRejectsSameOriginRedirectLoopAtHopLimit(t *testing.T) {
+	var serverURL string
+	redirects := 0
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		redirects++
+		http.Redirect(w, r, serverURL+"/attachments/uuid-1", http.StatusFound)
+	}))
+	defer server.Close()
+	serverURL = server.URL
+
+	origHost := flag.Host
+	flag.Host = server.URL
+	defer func() { flag.Host = origHost }()
+
+	_, _, _, err := DownloadAttachment(context.Background(), "/attachments/uuid-1", "*/*")
+	if err == nil {
+		t.Fatal("expected redirect limit error")
+	}
+	if !strings.Contains(err.Error(), "stopped after 10 redirects") {
+		t.Fatalf("unexpected error: %v", err)
+	}
+	if redirects != 10 {
+		t.Fatalf("redirects = %d, want 10", redirects)
+	}
+}
+
+func TestWriteAttachmentStreamsBodyToFile(t *testing.T) {
+	path := filepath.Join(t.TempDir(), "attachment.bin")
+	written, err := WriteAttachment(strings.NewReader(strings.Repeat("z", 64)), path)
+	if err != nil {
+		t.Fatalf("WriteAttachment() error = %v", err)
+	}
+	if written != 64 {
+		t.Fatalf("written = %d, want 64", written)
+	}
+	data, err := os.ReadFile(path)
+	if err != nil {
+		t.Fatalf("ReadFile() error = %v", err)
+	}
+	if string(data) != strings.Repeat("z", 64) {
+		t.Fatalf("body mismatch")
+	}
+}
+
+func TestWriteAttachmentCreatesPrivateFile(t *testing.T) {
+	path := filepath.Join(t.TempDir(), "attachment.bin")
+
+	if _, err := WriteAttachment(strings.NewReader("secret"), path); err != nil {
+		t.Fatalf("WriteAttachment() error = %v", err)
+	}
+
+	info, err := os.Stat(path)
+	if err != nil {
+		t.Fatalf("Stat() error = %v", err)
+	}
+	if got := info.Mode().Perm() & 0o077; got != 0 {
+		t.Fatalf("permissions = %03o, want no group/other bits", info.Mode().Perm())
+	}
+}
+
+func TestWriteAttachmentTightensExistingFilePermissions(t *testing.T) {
+	path := filepath.Join(t.TempDir(), "attachment.bin")
+	if err := os.WriteFile(path, []byte("public"), 0o644); err != nil {
+		t.Fatalf("WriteFile() error = %v", err)
+	}
+
+	if _, err := WriteAttachment(strings.NewReader("secret"), path); err != nil {
+		t.Fatalf("WriteAttachment() error = %v", err)
+	}
+
+	info, err := os.Stat(path)
+	if err != nil {
+		t.Fatalf("Stat() error = %v", err)
+	}
+	if got := info.Mode().Perm(); got != 0o600 {
+		t.Fatalf("permissions = %03o, want 600", got)
+	}
+}
+
+func TestDownloadAttachmentErrorsOnNon2xx(t *testing.T) {
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		http.Error(w, "nope", http.StatusForbidden)
+	}))
+	defer server.Close()
+
+	origHost := flag.Host
+	flag.Host = server.URL
+	defer func() { flag.Host = origHost }()
+
+	_, _, status, err := DownloadAttachment(context.Background(), "/attachments/uuid-1", "*/*")
+	if status != http.StatusForbidden {
+		t.Fatalf("status = %d, want %d", status, http.StatusForbidden)
+	}
+	var httpErr *HTTPError
+	if !errors.As(err, &httpErr) {
+		t.Fatalf("expected HTTPError, got %T", err)
+	}
+}
+
+func TestAttachmentHTTPClientHasNoTotalTimeout(t *testing.T) {
+	origin := &url.URL{Scheme: "https", Host: "example.com"}
+
+	client := attachmentHTTPClient(origin)
+
+	if client.Timeout != 0 {
+		t.Fatalf("Timeout = %v, want 0", client.Timeout)
+	}
+}

pkg/gitea/rest.go

@@ -9,6 +9,8 @@ import (
 	"io"
 	"net/http"
 	"net/url"
+	"os"
+	"path"
 	"strings"
 	"sync"
 	"time"
@@ -34,6 +36,12 @@ func (e *HTTPError) Error() string {
 	return fmt.Sprintf("request failed with status %d: %s", e.StatusCode, e.Body)
 }
 
+type AttachmentResponse struct {
+	Body        io.ReadCloser
+	ContentType string
+	StatusCode  int
+}
+
 func tokenFromContext(ctx context.Context) string {
 	if ctx != nil {
 		if token, ok := ctx.Value(mcpContext.TokenContextKey).(string); ok && token != "" {
@@ -75,6 +83,40 @@ func buildAPIURL(path string, query url.Values) (string, error) {
 	return u.String(), nil
 }
 
+func buildAttachmentURL(attachmentPath string) (string, error) {
+	host := strings.TrimRight(flag.Host, "/")
+	if host == "" {
+		return "", errors.New("gitea host is empty")
+	}
+	baseURL, err := url.Parse(host)
+	if err != nil {
+		return "", err
+	}
+	if attachmentPath == "" {
+		return "", errors.New("attachment path is empty")
+	}
+	if strings.Contains(attachmentPath, "://") {
+		return "", errors.New("attachment path must not be a URL")
+	}
+	if !strings.HasPrefix(attachmentPath, "/attachments/") {
+		return "", errors.New("attachment path must start with /attachments/")
+	}
+	cleanPath := path.Clean(attachmentPath)
+	if !strings.HasPrefix(cleanPath, "/attachments/") {
+		return "", errors.New("attachment path must stay within /attachments/")
+	}
+	if cleanPath == "/attachments" || cleanPath == "/attachments/" {
+		return "", errors.New("attachment uuid is required")
+	}
+	joinedPath := strings.TrimRight(baseURL.Path, "/") + cleanPath
+	if joinedPath == "" {
+		joinedPath = cleanPath
+	}
+	baseURL.Path = joinedPath
+	baseURL.RawPath = joinedPath
+	return baseURL.String(), nil
+}
+
 // DoJSON performs an API request and decodes a JSON response into respOut (if non-nil).
 // It returns the HTTP status code.
 func DoJSON(ctx context.Context, method, path string, query url.Values, body, respOut any) (int, error) {
@@ -91,45 +133,142 @@ func DoJSON(ctx context.Context, method, path string, query url.Values, body, re
 	if err != nil {
 		return 0, err
 	}
+
 	req, err := http.NewRequestWithContext(ctx, method, u, bodyReader)
 	if err != nil {
 		return 0, fmt.Errorf("create request: %w", err)
 	}
-
 	token := tokenFromContext(ctx)
 	if token != "" {
 		req.Header.Set("Authorization", "token "+token)
 	}
-	req.Header.Set("Accept", "application/json")
 	if body != nil {
 		req.Header.Set("Content-Type", "application/json")
 	}
+	if respOut != nil {
+		req.Header.Set("Accept", "application/json")
+	}
 
-	client := restHTTPClient()
-	resp, err := client.Do(req)
+	resp, err := restHTTPClient().Do(req)
 	if err != nil {
 		return 0, fmt.Errorf("do request: %w", err)
 	}
 	defer resp.Body.Close()
 
 	if resp.StatusCode < 200 || resp.StatusCode >= 300 {
-		bodySnippet, _ := io.ReadAll(io.LimitReader(resp.Body, errBodySnippetSize))
+		bodySnippet, err := io.ReadAll(io.LimitReader(resp.Body, errBodySnippetSize+1))
+		if err != nil {
+			return resp.StatusCode, fmt.Errorf("read response: %w", err)
+		}
+		if len(bodySnippet) > errBodySnippetSize {
+			bodySnippet = bodySnippet[:errBodySnippetSize]
+		}
 		return resp.StatusCode, &HTTPError{StatusCode: resp.StatusCode, Body: strings.TrimSpace(string(bodySnippet))}
 	}
 
 	if respOut == nil {
-		_, _ = io.Copy(io.Discard, resp.Body) // best-effort
+		_, _ = io.Copy(io.Discard, resp.Body)
 		return resp.StatusCode, nil
 	}
 
 	if err := json.NewDecoder(resp.Body).Decode(respOut); err != nil {
 		return resp.StatusCode, fmt.Errorf("decode response: %w", err)
 	}
+
 	return resp.StatusCode, nil
 }
 
+func attachmentHTTPClient(origin *url.URL) *http.Client {
+	return &http.Client{
+		Transport: sharedTransport(),
+		CheckRedirect: func(req *http.Request, via []*http.Request) error {
+			if err := checkRedirect(req, via); err != nil {
+				return err
+			}
+			if req.URL.Scheme != origin.Scheme || req.URL.Host != origin.Host {
+				return errors.New("attachment redirect changed origin")
+			}
+			return nil
+		},
+	}
+}
+
+func OpenAttachment(ctx context.Context, attachmentPath, accept string) (*AttachmentResponse, error) {
+	u, err := buildAttachmentURL(attachmentPath)
+	if err != nil {
+		return nil, err
+	}
+	origin, err := url.Parse(u)
+	if err != nil {
+		return nil, err
+	}
+	req, err := http.NewRequestWithContext(ctx, http.MethodGet, u, nil)
+	if err != nil {
+		return nil, fmt.Errorf("create request: %w", err)
+	}
+	token := tokenFromContext(ctx)
+	if token != "" {
+		req.Header.Set("Authorization", "token "+token)
+	}
+	if accept != "" {
+		req.Header.Set("Accept", accept)
+	}
+
+	resp, err := attachmentHTTPClient(origin).Do(req)
+	if err != nil {
+		return nil, fmt.Errorf("do request: %w", err)
+	}
+	if resp.StatusCode < 200 || resp.StatusCode >= 300 {
+		defer resp.Body.Close()
+		bodySnippet, readErr := io.ReadAll(io.LimitReader(resp.Body, errBodySnippetSize+1))
+		if readErr != nil {
+			return nil, fmt.Errorf("read response: %w", readErr)
+		}
+		if len(bodySnippet) > errBodySnippetSize {
+			bodySnippet = bodySnippet[:errBodySnippetSize]
+		}
+		return nil, &HTTPError{StatusCode: resp.StatusCode, Body: strings.TrimSpace(string(bodySnippet))}
+	}
+	return &AttachmentResponse{Body: resp.Body, ContentType: resp.Header.Get("Content-Type"), StatusCode: resp.StatusCode}, nil
+}
+
+// DownloadAttachment downloads attachment bytes from a same-host attachment path.
+func DownloadAttachment(ctx context.Context, attachmentPath, accept string) ([]byte, string, int, error) {
+	resp, err := OpenAttachment(ctx, attachmentPath, accept)
+	if err != nil {
+		var httpErr *HTTPError
+		if errors.As(err, &httpErr) {
+			return nil, "", httpErr.StatusCode, err
+		}
+		return nil, "", 0, err
+	}
+	defer resp.Body.Close()
+
+	respBytes, err := io.ReadAll(resp.Body)
+	if err != nil {
+		return nil, "", resp.StatusCode, fmt.Errorf("read response: %w", err)
+	}
+	return respBytes, resp.ContentType, resp.StatusCode, nil
+}
+
+func WriteAttachment(body io.Reader, outputPath string) (int64, error) {
+	file, err := os.OpenFile(outputPath, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0o600)
+	if err != nil {
+		return 0, err
+	}
+	defer file.Close()
+	if err := file.Chmod(0o600); err != nil {
+		return 0, err
+	}
+
+	written, err := io.Copy(file, body)
+	if err != nil {
+		return written, err
+	}
+	return written, file.Close()
+}
+
 // DoBytes performs an API request and returns the raw response bytes.
-// It returns the HTTP status code.
 func DoBytes(ctx context.Context, method, path string, query url.Values, body any, accept string) ([]byte, int, error) {
 	var bodyReader io.Reader
 	if body != nil {
@@ -144,24 +283,23 @@ func DoBytes(ctx context.Context, method, path string, query url.Values, body an
 	if err != nil {
 		return nil, 0, err
 	}
+
 	req, err := http.NewRequestWithContext(ctx, method, u, bodyReader)
 	if err != nil {
 		return nil, 0, fmt.Errorf("create request: %w", err)
 	}
-
 	token := tokenFromContext(ctx)
 	if token != "" {
 		req.Header.Set("Authorization", "token "+token)
 	}
-	if accept != "" {
-		req.Header.Set("Accept", accept)
-	}
 	if body != nil {
 		req.Header.Set("Content-Type", "application/json")
 	}
+	if accept != "" {
+		req.Header.Set("Accept", accept)
+	}
 
-	client := restHTTPClient()
-	resp, err := client.Do(req)
+	resp, err := restHTTPClient().Do(req)
 	if err != nil {
 		return nil, 0, fmt.Errorf("do request: %w", err)
 	}
@@ -171,7 +309,6 @@ func DoBytes(ctx context.Context, method, path string, query url.Values, body an
 	if err != nil {
 		return nil, resp.StatusCode, fmt.Errorf("read response: %w", err)
 	}
-
 	if resp.StatusCode < 200 || resp.StatusCode >= 300 {
 		bodySnippet := respBytes
 		if len(bodySnippet) > errBodySnippetSize {
@@ -179,6 +316,5 @@ func DoBytes(ctx context.Context, method, path string, query url.Values, body an
 		}
 		return nil, resp.StatusCode, &HTTPError{StatusCode: resp.StatusCode, Body: strings.TrimSpace(string(bodySnippet))}
 	}
-
 	return respBytes, resp.StatusCode, nil
 }

pkg/gitea/rest_test.go

@@ -2,6 +2,11 @@ package gitea
 
 import (
 	"context"
+	"errors"
+	"io"
+	"net/http"
+	"net/http/httptest"
+	"strings"
 	"testing"
 
 	mcpContext "gitea.com/gitea/gitea-mcp/pkg/context"
@@ -28,3 +33,32 @@ func TestTokenFromContext(t *testing.T) {
 		}
 	})
 }
+
+func TestDoJSON_LimitsErrorResponseBody(t *testing.T) {
+	payload := strings.Repeat("x", errBodySnippetSize+100)
+	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.WriteHeader(http.StatusBadRequest)
+		_, _ = io.WriteString(w, payload)
+	}))
+	defer srv.Close()
+
+	origHost := flag.Host
+	defer func() { flag.Host = origHost }()
+	flag.Host = srv.URL
+
+	status, err := DoJSON(context.Background(), http.MethodGet, "repos/owner/repo", nil, nil, nil)
+	if err == nil {
+		t.Fatal("expected error")
+	}
+	if status != http.StatusBadRequest {
+		t.Fatalf("expected status %d, got %d", http.StatusBadRequest, status)
+	}
+
+	var httpErr *HTTPError
+	if !errors.As(err, &httpErr) {
+		t.Fatalf("expected HTTPError, got %T", err)
+	}
+	if len(httpErr.Body) != errBodySnippetSize {
+		t.Fatalf("expected body length %d, got %d", errBodySnippetSize, len(httpErr.Body))
+	}
+}