feat(serve,ui): optional initial prompt on session create

POST /api/sessions now accepts { initial_prompt: string }. When
non-empty, the createSpawner sleeps 3s (so claude has time to boot
and show its prompt) and then sends the text + Enter into the pane
via the existing tmux send-keys seam. Fire-and-forget: errors are
logged, never fail the 201 response.

CreateSpawner interface gains SendInitialPrompt(name, text); tests
update the fake with an initialCalls/initialArgs capture.

NewSessionModal grows a 3-row textarea below the workdir + recents
block, 16px font to avoid iOS zoom, trimmed + omitted when blank.

Author: aksOps

internal/serve/api/create.go

@@ -19,6 +19,10 @@ import (
 // without spawning real tmux + claude.
 type CreateSpawner interface {
 	Spawn(name, workdir string) (session.Session, error)
+	// SendInitialPrompt fires a one-shot prompt into the new session
+	// after claude has had time to boot. Fire-and-forget; errors are
+	// logged but don't fail the create response.
+	SendInitialPrompt(name, text string)
 }
 
 // CreateLookPath is the seam used for the "claude on PATH" check.
@@ -28,8 +32,9 @@ type CreateLookPath interface {
 }
 
 type createReqBody struct {
-	Workdir string `json:"workdir"`
-	Name    string `json:"name,omitempty"`
+	Workdir       string `json:"workdir"`
+	Name          string `json:"name,omitempty"`
+	InitialPrompt string `json:"initial_prompt,omitempty"`
 }
 
 var createNameRe = regexp.MustCompile(`^[A-Za-z0-9._-]{1,64}$`)
@@ -105,6 +110,10 @@ func CreateSession(src InputSessionSource, sp CreateSpawner, lp CreateLookPath)
 			return
 		}
 
+		if prompt := strings.TrimRight(body.InitialPrompt, " \t\n\r"); prompt != "" {
+			sp.SendInitialPrompt(sess.Name, prompt)
+		}
+
 		w.Header().Set("Content-Type", "application/json")
 		w.WriteHeader(http.StatusCreated)
 		_ = json.NewEncoder(w).Encode(sess)

internal/serve/api/create_test.go

@@ -30,10 +30,12 @@ func (f *fakeCreateProj) Get(name string) (session.Session, bool) {
 func (f *fakeCreateProj) TmuxAlive(name string) bool { return true }
 
 type fakeCreateSpawner struct {
-	returnSess session.Session
-	err        error
-	calledWith struct{ name, workdir string }
-	called     int
+	returnSess   session.Session
+	err          error
+	calledWith   struct{ name, workdir string }
+	called       int
+	initialCalls int
+	initialArgs  struct{ name, text string }
 }
 
 func (f *fakeCreateSpawner) Spawn(name, workdir string) (session.Session, error) {
@@ -49,6 +51,12 @@ func (f *fakeCreateSpawner) Spawn(name, workdir string) (session.Session, error)
 	return s, nil
 }
 
+func (f *fakeCreateSpawner) SendInitialPrompt(name, text string) {
+	f.initialCalls++
+	f.initialArgs.name = name
+	f.initialArgs.text = text
+}
+
 type fakeLookPath struct{ ok bool }
 
 func (f fakeLookPath) LookPath(file string) (string, error) {

internal/serve/server.go

@@ -865,6 +865,23 @@ func (c createSpawner) Spawn(name, workdir string) (session.Session, error) {
 	})
 }
 
+// SendInitialPrompt fires `text` into the new session's pane after a
+// short delay so claude has time to boot and show its prompt. Runs
+// in a goroutine — fire-and-forget; errors are logged, not returned.
+func (c createSpawner) SendInitialPrompt(name, text string) {
+	go func() {
+		time.Sleep(3 * time.Second)
+		target := name + ":0.0"
+		if err := c.tmux.SendKeys(target, text); err != nil {
+			slog.Warn("initial prompt send failed", "session", name, "err", err.Error())
+			return
+		}
+		if err := c.tmux.SendEnter(target); err != nil {
+			slog.Warn("initial prompt enter failed", "session", name, "err", err.Error())
+		}
+	}()
+}
+
 // execLookPath is a tiny adapter so api.CreateLookPath can be
 // satisfied by the free function os/exec.LookPath.
 type execLookPath struct{}

ui/src/components/NewSessionModal.tsx

@@ -29,6 +29,7 @@ export function NewSessionModal({ open, onClose, recents }: NewSessionModalProps
   const create = useCreateSession();
   const [workdir, setWorkdir] = useState(recents[0] ?? "");
   const [name, setName] = useState<string>("");
+  const [initialPrompt, setInitialPrompt] = useState<string>("");
   const [collision, setCollision] = useState<CreateConflict | null>(null);
   const [renaming, setRenaming] = useState(false);
   const [errMsg, setErrMsg] = useState<string | null>(null);
@@ -37,6 +38,7 @@ export function NewSessionModal({ open, onClose, recents }: NewSessionModalProps
     if (!open) return;
     setWorkdir(recents[0] ?? "");
     setName("");
+    setInitialPrompt("");
     setCollision(null);
     setRenaming(false);
     setErrMsg(null);
@@ -46,9 +48,11 @@ export function NewSessionModal({ open, onClose, recents }: NewSessionModalProps
   async function handleSubmit() {
     setErrMsg(null);
     try {
+      const trimmedPrompt = initialPrompt.trim();
       const sess = await create.mutateAsync({
         workdir,
         ...(renaming && name ? { name } : {}),
+        ...(trimmedPrompt ? { initial_prompt: trimmedPrompt } : {}),
       });
       navigate(`/s/${encodeURIComponent(sess.name)}`);
       onClose();
@@ -150,6 +154,18 @@ export function NewSessionModal({ open, onClose, recents }: NewSessionModalProps
                 </div>
               )}
 
+              <label className="mb-1 block text-[11px] font-semibold uppercase tracking-[0.18em] text-fg-muted">
+                Initial prompt <span className="font-normal normal-case tracking-normal text-fg-dim">(optional — sent after boot)</span>
+              </label>
+              <textarea
+                aria-label="Initial prompt"
+                value={initialPrompt}
+                onChange={(e) => setInitialPrompt(e.target.value)}
+                placeholder="e.g. review the diff on main and suggest follow-ups"
+                rows={3}
+                className="mb-3 block w-full resize-y rounded border border-border bg-bg px-2 py-1.5 font-mono text-[16px] text-fg placeholder:text-fg-dim focus:outline-none focus:ring-1 focus:ring-accent-gold sm:text-xs"
+              />
+
               {errMsg && (
                 <div
                   role="alert"

ui/src/hooks/useCreateSession.ts

@@ -5,6 +5,7 @@ import type { Session } from "@/hooks/useSessions";
 export interface CreateSessionBody {
   workdir: string;
   name?: string;
+  initial_prompt?: string;
 }
 
 export interface CreateConflict {