fix(serve): split input into literal + Enter keybind

tmux send-keys -l sends LF as a literal character; claude's TUI
treats LF as 'insert newline in multi-line input', not 'submit'.
Split the send into two calls: literal text via -l, then a bare
tmux Enter keybind so the real submit path fires.

Preset 'continue' skips SendKeys entirely (Enter-only).
Handler test assertions updated to verify sendCalls + enterCalls
separately.

Author: aksOps

internal/serve/api/input.go

@@ -26,6 +26,7 @@ type InputSessionSource interface {
 // InputTmux is the narrow slice of *tmux.Client the Input handler needs.
 type InputTmux interface {
 	SendKeys(target, keys string) error
+	SendEnter(target string) error
 }
 
 type inputReq struct {
@@ -95,7 +96,18 @@ func Input(src InputSessionSource, tmux InputTmux) http.HandlerFunc {
 		}
 
 		target := fmt.Sprintf("%s:0.0", sess.Name)
-		if err := tmux.SendKeys(target, keys); err != nil {
+		// `keys` always ends with "\n" by construction (see expandInput).
+		// We split: literal text via -l, then a real tmux Enter key so
+		// claude's TUI treats it as submit rather than "add newline".
+		literal := strings.TrimRight(keys, "\n")
+		if literal != "" {
+			if err := tmux.SendKeys(target, literal); err != nil {
+				slog.Error("input send_failed", "session", name, "err", err.Error())
+				writeInputErr(w, http.StatusInternalServerError, "send_failed", err.Error())
+				return
+			}
+		}
+		if err := tmux.SendEnter(target); err != nil {
 			slog.Error("input send_failed", "session", name, "err", err.Error())
 			writeInputErr(w, http.StatusInternalServerError, "send_failed", err.Error())
 			return

internal/serve/api/input_test.go

@@ -29,14 +29,23 @@ func (f *fakeInputProj) TmuxAlive(name string) bool {
 }
 
 type fakeInputTmux struct {
-	lastTarget string
-	lastKeys   string
-	err        error
+	lastTarget  string
+	lastKeys    string
+	sendCalls   int
+	enterCalls  int
+	err         error
 }
 
 func (f *fakeInputTmux) SendKeys(target, keys string) error {
 	f.lastTarget = target
 	f.lastKeys = keys
+	f.sendCalls++
+	return f.err
+}
+
+func (f *fakeInputTmux) SendEnter(target string) error {
+	f.lastTarget = target
+	f.enterCalls++
 	return f.err
 }
 
@@ -83,8 +92,11 @@ func TestInput_Preset_Yes(t *testing.T) {
 	if tmux.lastTarget != "alpha:0.0" {
 		t.Fatalf("tmux target = %q, want %q", tmux.lastTarget, "alpha:0.0")
 	}
-	if tmux.lastKeys != "y\n" {
-		t.Fatalf("tmux keys = %q, want %q", tmux.lastKeys, "y\n")
+	if tmux.lastKeys != "y" {
+		t.Fatalf("tmux literal = %q, want %q", tmux.lastKeys, "y")
+	}
+	if tmux.enterCalls != 1 {
+		t.Fatalf("SendEnter called %d times, want 1", tmux.enterCalls)
 	}
 }
 
@@ -96,8 +108,8 @@ func TestInput_Preset_No(t *testing.T) {
 	if rec.Code != http.StatusNoContent {
 		t.Fatalf("status = %d, want 204", rec.Code)
 	}
-	if tmux.lastKeys != "n\n" {
-		t.Fatalf("tmux keys = %q, want %q", tmux.lastKeys, "n\n")
+	if tmux.lastKeys != "n" || tmux.enterCalls != 1 {
+		t.Fatalf("tmux literal=%q enters=%d, want %q + 1", tmux.lastKeys, tmux.enterCalls, "n")
 	}
 }
 
@@ -109,8 +121,11 @@ func TestInput_Preset_Continue(t *testing.T) {
 	if rec.Code != http.StatusNoContent {
 		t.Fatalf("status = %d, want 204", rec.Code)
 	}
-	if tmux.lastKeys != "\n" {
-		t.Fatalf("tmux keys = %q, want %q", tmux.lastKeys, "\n")
+	if tmux.sendCalls != 0 {
+		t.Fatalf("SendKeys called %d times for 'continue', want 0 (Enter-only)", tmux.sendCalls)
+	}
+	if tmux.enterCalls != 1 {
+		t.Fatalf("SendEnter called %d times, want 1", tmux.enterCalls)
 	}
 }
 
@@ -122,8 +137,8 @@ func TestInput_FreeText(t *testing.T) {
 	if rec.Code != http.StatusNoContent {
 		t.Fatalf("status = %d, want 204", rec.Code)
 	}
-	if tmux.lastKeys != "approve\n" {
-		t.Fatalf("tmux keys = %q, want %q", tmux.lastKeys, "approve\n")
+	if tmux.lastKeys != "approve" || tmux.enterCalls != 1 {
+		t.Fatalf("tmux literal=%q enters=%d, want %q + 1", tmux.lastKeys, tmux.enterCalls, "approve")
 	}
 }
 

internal/tmux/client.go

@@ -214,6 +214,21 @@ func (c *Client) SendKeys(target, keys string) error {
 	return nil
 }
 
+// SendEnter sends the tmux "Enter" key (without -l) to the given
+// target. A literal `\n` via SendKeys is the LF character, which
+// TUIs like claude interpret as "insert newline", not "submit".
+// Sending the Enter keybind triggers the real submit path.
+func (c *Client) SendEnter(target string) error {
+	if target == "" {
+		return fmt.Errorf("tmux send-keys Enter: empty target")
+	}
+	out, err := c.cmd("tmux", "send-keys", "-t", target, "Enter").CombinedOutput()
+	if err != nil {
+		return fmt.Errorf("tmux send-keys Enter -t %q: %w: %s", target, err, string(out))
+	}
+	return nil
+}
+
 // --- unexported helpers ---
 
 // buildNewSessionArgs constructs args for `tmux new-session`.