Support steering for remote runtimes

Add SteerSession to the RemoteClient interface and implement it on the
HTTP Client (POST /sessions/:id/steer). RemoteRuntime.Steer() delegates
to the remote server so the TUI works identically regardless of whether
the runtime is local or remote.

App.Steer() now tries GetLocalRuntime first, then falls back to the
Steerer interface so both PersistentRuntime and RemoteRuntime are
handled.

Author: trungutt

pkg/app/app.go

@@ -532,6 +532,27 @@ func (a *App) SubscribeWith(ctx context.Context, send func(tea.Msg)) {
 	}
 }
 
+// Steerer is implemented by runtimes that support mid-turn message injection.
+type Steerer interface {
+	Steer(msg runtime.SteeredMessage) bool
+}
+
+// Steer enqueues a user message for mid-turn injection into the running
+// agent loop. Works with both local runtimes (via the SteerQueue) and
+// remote runtimes (via POST /sessions/:id/steer). Returns false if
+// steering is not supported by the runtime or the queue is full.
+func (a *App) Steer(msg runtime.SteeredMessage) bool {
+	// Try unwrapping PersistentRuntime → LocalRuntime first
+	if lr := runtime.GetLocalRuntime(a.runtime); lr != nil {
+		return lr.Steer(msg)
+	}
+	// Try the Steerer interface (e.g. RemoteRuntime)
+	if s, ok := a.runtime.(Steerer); ok {
+		return s.Steer(msg)
+	}
+	return false
+}
+
 // Resume resumes the runtime with the given confirmation request
 func (a *App) Resume(req runtime.ResumeRequest) {
 	a.runtime.Resume(context.Background(), req)

pkg/runtime/client.go

@@ -266,6 +266,12 @@ func (c *Client) ResumeSession(ctx context.Context, id, confirmation, reason, to
 	return c.doRequest(ctx, http.MethodPost, "/api/sessions/"+id+"/resume", req, nil)
 }
 
+// SteerSession injects user messages into a running session mid-turn.
+func (c *Client) SteerSession(ctx context.Context, sessionID string, messages []api.Message) error {
+	req := api.SteerSessionRequest{Messages: messages}
+	return c.doRequest(ctx, http.MethodPost, "/api/sessions/"+sessionID+"/steer", req, nil)
+}
+
 // DeleteSession deletes a session by ID
 func (c *Client) DeleteSession(ctx context.Context, id string) error {
 	return c.doRequest(ctx, "DELETE", "/api/sessions/"+id, nil, nil)

pkg/runtime/remote_client.go

@@ -30,6 +30,9 @@ type RemoteClient interface {
 	// RunAgentWithAgentName executes an agent with a specific agent name
 	RunAgentWithAgentName(ctx context.Context, sessionID, agent, agentName string, messages []api.Message) (<-chan Event, error)
 
+	// SteerSession injects user messages into a running session mid-turn
+	SteerSession(ctx context.Context, sessionID string, messages []api.Message) error
+
 	// UpdateSessionTitle updates the title of a session
 	UpdateSessionTitle(ctx context.Context, sessionID, title string) error
 

pkg/runtime/remote_runtime.go

@@ -211,6 +211,19 @@ func (r *RemoteRuntime) Run(ctx context.Context, sess *session.Session) ([]sessi
 	return sess.GetAllMessages(), nil
 }
 
+// Steer enqueues a user message for mid-turn injection into the running
+// agent loop on the remote server. Returns false if the session is not
+// active or the steer queue is full.
+func (r *RemoteRuntime) Steer(msg SteeredMessage) bool {
+	if r.sessionID == "" {
+		return false
+	}
+	err := r.client.SteerSession(context.Background(), r.sessionID, []api.Message{
+		{Content: msg.Content, MultiContent: msg.MultiContent},
+	})
+	return err == nil
+}
+
 // Resume allows resuming execution after user confirmation
 func (r *RemoteRuntime) Resume(ctx context.Context, req ResumeRequest) {
 	slog.Debug("Resuming remote runtime", "agent", r.currentAgent, "type", req.Type, "reason", req.Reason, "tool_name", req.ToolName, "session_id", r.sessionID)