diff --git a/knotmirror/xrpc/git_format_patch.go b/knotmirror/xrpc/git_format_patch.go
new file mode 100644
index 00000000..4386dcf0
--- /dev/null
+++ b/knotmirror/xrpc/git_format_patch.go
@@ -0,0 +1,54 @@
+package xrpc
+
+import (
+	"bytes"
+	"fmt"
+	"net/http"
+	"os/exec"
+	"strings"
+
+	"github.com/bluesky-social/indigo/atproto/atclient"
+	"github.com/bluesky-social/indigo/atproto/syntax"
+)
+
+func (x *Xrpc) FormatPatch(w http.ResponseWriter, r *http.Request) {
+	var (
+		repoQuery = r.URL.Query().Get("repo")
+		from      = r.URL.Query().Get("from")
+		to        = r.URL.Query().Get("to")
+	)
+
+	repo, err := syntax.ParseDID(repoQuery)
+	if err != nil {
+		writeJson(w, http.StatusBadRequest, atclient.ErrorBody{Name: "BadRequest", Message: fmt.Sprintf("repo parameter invalid: %s", repoQuery)})
+		return
+	}
+
+	// reject leading dashes so user input can't be parsed as git flags
+	if from == "" || to == "" || strings.HasPrefix(from, "-") || strings.HasPrefix(to, "-") {
+		writeJson(w, http.StatusBadRequest, atclient.ErrorBody{Name: "BadRequest", Message: "missing or invalid from/to parameter"})
+		return
+	}
+
+	l := x.logger.With("method", "git.formatPatch", "repo", repo, "from", from, "to", to)
+	l.Debug("request")
+
+	ctx := r.Context()
+
+	repoPath, err := x.makeRepoPath(ctx, repo)
+	if err != nil {
+		writeJson(w, http.StatusNotFound, atclient.ErrorBody{Name: "RepoNotFound", Message: fmt.Sprintf("unknown repository: %q", repo)})
+		return
+	}
+
+	cmd := exec.CommandContext(ctx, "git", "-C", repoPath, "format-patch", "--stdout", fmt.Sprintf("%s..%s", from, to))
+	stderr := new(bytes.Buffer)
+	cmd.Stderr = stderr
+
+	w.Header().Set("Content-Type", "text/plain; charset=utf-8")
+	cmd.Stdout = w
+	if err := cmd.Run(); err != nil {
+		l.Error("running format-patch", "err", err, "stderr", stderr.String())
+		w.WriteHeader(http.StatusInternalServerError)
+	}
+}
diff --git a/knotmirror/xrpc/xrpc.go b/knotmirror/xrpc/xrpc.go
index aa2ebc6c..b94b015e 100644
--- a/knotmirror/xrpc/xrpc.go
+++ b/knotmirror/xrpc/xrpc.go
@@ -66,6 +66,7 @@ func (x *Xrpc) Router() http.Handler {
 		// r.Get("/"+tangled.GitTempGetCommitNSID, x.GetCommit) // todo
 		// r.Get("/"+tangled.GitTempGetDiffNSID, x.GetDiff) // todo
 		r.Get("/"+tangled.GitTempGetEntryNSID, x.GetEntry) // todo
+		r.Get("/"+tangled.GitTempFormatPatchNSID, x.FormatPatch)
 		// r.Get("/"+tangled.GitTempGetHeadNSID, x.GetHead) // todo
 		r.Get("/"+tangled.GitTempGetMergeBaseNSID, x.GetMergeBase)
 		r.Get("/"+tangled.GitTempGetTagNSID, x.GetTag) // using types.Response