diff --git a/internal/server/artifact_download_test.go b/internal/server/artifact_download_test.go
new file mode 100644
index 0000000..ee8bef6
--- /dev/null
+++ b/internal/server/artifact_download_test.go
@@ -0,0 +1,64 @@
+package server
+
+import (
+	"net/http"
+	"net/http/httptest"
+	"strings"
+	"testing"
+
+	"agent-system-backend/internal/store"
+	core "agent-system-core"
+)
+
+// TestArtifactContentDisposition：?download=1 切换 attachment；中文名走 RFC 5987
+// filename* 权威编码；默认 inline 便于浏览器内预览。
+func TestArtifactContentDisposition(t *testing.T) {
+	srv, st := newTestServer(t)
+	h := srv.Handler()
+	a := &core.Artifact{ProjectID: "p1", Owner: store.OwnerDefault, Name: "会议纪要.docx", Kind: "document"}
+	if err := st.CreateArtifact(a, []byte("PK\x03\x04 docx bytes")); err != nil {
+		t.Fatal(err)
+	}
+
+	get := func(query string) *httptest.ResponseRecorder {
+		req := httptest.NewRequest(http.MethodGet, "/api/artifacts/"+a.ID+"/content"+query, nil)
+		rec := httptest.NewRecorder()
+		h.ServeHTTP(rec, req)
+		return rec
+	}
+
+	inline := get("")
+	if cd := inline.Header().Get("Content-Disposition"); !strings.HasPrefix(cd, "inline") ||
+		!strings.Contains(cd, `filename*=UTF-8''%E4%BC%9A%E8%AE%AE%E7%BA%AA%E8%A6%81.docx`) {
+		t.Errorf("inline disposition mismatch: %s", cd)
+	}
+	if ct := inline.Header().Get("Content-Type"); ct != "application/vnd.openxmlformats-officedocument.wordprocessingml.document" {
+		t.Errorf("docx content-type fallback mismatch: %s", ct)
+	}
+
+	dl := get("?download=1")
+	if cd := dl.Header().Get("Content-Disposition"); !strings.HasPrefix(cd, "attachment") ||
+		!strings.Contains(cd, `filename="____.docx"`) { // ASCII 兜底：4 个汉字 → 4 个下划线
+		t.Errorf("attachment disposition mismatch: %s", cd)
+	}
+}
+
+// TestContentTypeByExtension：MIME 为空时按扩展名回退（docx 显式表 + csv 显式表），
+// 未知扩展回落 text/plain，image kind 回落二进制流。
+func TestContentTypeByExtension(t *testing.T) {
+	if ct := contentTypeOf(core.Artifact{Name: "a.DOCX"}); ct != "application/vnd.openxmlformats-officedocument.wordprocessingml.document" {
+		t.Errorf("docx ext (uppercase) mismatch: %s", ct)
+	}
+	if ct := contentTypeOf(core.Artifact{Name: "b.csv"}); !strings.HasPrefix(ct, "text/csv") {
+		t.Errorf("csv ext mismatch: %s", ct)
+	}
+	if ct := contentTypeOf(core.Artifact{Name: "c.bin", Kind: "image"}); ct != "application/octet-stream" {
+		t.Errorf("image fallback mismatch: %s", ct)
+	}
+	if ct := contentTypeOf(core.Artifact{Name: "d"}); !strings.HasPrefix(ct, "text/plain") {
+		t.Errorf("plain fallback mismatch: %s", ct)
+	}
+	if ct := contentTypeOf(core.Artifact{Name: "e.md", MIME: "text/x-override"}); ct != "text/x-override" {
+		t.Errorf("explicit mime must win: %s", ct)
+	}
+}
diff --git a/internal/server/server.go b/internal/server/server.go
index 8aad361..7e2f092 100644
--- a/internal/server/server.go
+++ b/internal/server/server.go
@@ -9,7 +9,9 @@ import (
 	"fmt"
 	"io"
 	"io/fs"
+	"mime"
 	"net/http"
+	"net/url"
 	"os"
 	"path/filepath"
 	"strconv"
@@ -852,6 +854,7 @@ func (s *Server) artifactContent(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 	w.Header().Set("Content-Type", contentTypeOf(a))
+	w.Header().Set("Content-Disposition", contentDisposition(a.Name, r.URL.Query().Get("download") == "1"))
 	w.Write(content)
 }
 
@@ -1219,16 +1222,62 @@ func (s *Server) backup(w http.ResponseWriter, r *http.Request) {
 	writeJSON(w, http.StatusOK, map[string]any{"ok": true, "path": dest})
 }
 
+// extMIME：常见文档扩展的显式类型表——系统 mime.types 不保证收录 docx/xlsx 等
+// Office 格式，显式兜底让上传件的下载与浏览器预览拿到正确 Content-Type。
+var extMIME = map[string]string{
+	".docx": "application/vnd.openxmlformats-officedocument.wordprocessingml.document",
+	".xlsx": "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet",
+	".pptx": "application/vnd.openxmlformats-officedocument.presentationml.presentation",
+	".doc":  "application/msword",
+	".xls":  "application/vnd.ms-excel",
+	".ppt":  "application/vnd.ms-powerpoint",
+	".pdf":  "application/pdf",
+	".zip":  "application/zip",
+	".csv":  "text/csv; charset=utf-8",
+	".md":   "text/markdown; charset=utf-8",
+}
+
 func contentTypeOf(a core.Artifact) string {
 	if a.MIME != "" {
 		return a.MIME
 	}
+	ext := strings.ToLower(filepath.Ext(a.Name))
+	if t, ok := extMIME[ext]; ok {
+		return t
+	}
+	if t := mime.TypeByExtension(ext); t != "" {
+		return t
+	}
 	if a.Kind == "image" {
 		return "application/octet-stream"
 	}
 	return "text/plain; charset=utf-8"
 }
 
+// contentDisposition：工件文件名带中文（如 会议纪要.docx）时用 RFC 5987 的
+// filename* 权威编码，另给纯 ASCII 兜底；?download=1 切换 attachment（下载），
+// 默认 inline（浏览器内预览）。
+func contentDisposition(name string, download bool) string {
+	disposition := "inline"
+	if download {
+		disposition = "attachment"
+	}
+	return fmt.Sprintf(`%s; filename="%s"; filename*=UTF-8''%s`, disposition, asciiFallbackName(name), url.PathEscape(name))
+}
+
+// asciiFallbackName：非 ASCII 与引号/反斜杠替换为下划线，仅作 filename 兜底。
+func asciiFallbackName(name string) string {
+	var b strings.Builder
+	for _, r := range name {
+		if r >= 0x20 && r < 0x7f && r != '"' && r != '\\' {
+			b.WriteRune(r)
+		} else {
+			b.WriteRune('_')
+		}
+	}
+	return b.String()
+}
+
 func maskMap(m map[string]any) map[string]any {
 	if m == nil {
 		return map[string]any{}