fix: forward subagent events to parent event bus in core spawn_subagent tool

The spawner closure in generate() called m.Subagent() without setting
OnEvent, so child events (tool calls, text streaming, reasoning deltas)
were silently discarded. Wire OnEvent to re-emit on the parent's bus,
matching the behavior already present in the extension SpawnSubagent path.

cmd/root.go

@@ -926,13 +926,23 @@ func runNormalMode(ctx context.Context) error {
 			},
 			SpawnSubagent: func(config extensions.SubagentConfig) (*extensions.SubagentHandle, *extensions.SubagentResult, error) {
 				// In-process subagent via SDK.
-				result, err := kitInstance.Subagent(ctx, kit.SubagentConfig{
+				sdkCfg := kit.SubagentConfig{
 					Prompt:       config.Prompt,
 					Model:        config.Model,
 					SystemPrompt: config.SystemPrompt,
 					Timeout:      config.Timeout,
 					NoSession:    config.NoSession,
-				})
+				}
+				// Bridge SDK events to extension SubagentEvents.
+				if config.OnEvent != nil {
+					sdkCfg.OnEvent = func(e kit.Event) {
+						se := sdkEventToSubagentEvent(e)
+						if se.Type != "" {
+							config.OnEvent(se)
+						}
+					}
+				}
+				result, err := kitInstance.Subagent(ctx, sdkCfg)
 				if result == nil {
 					return nil, &extensions.SubagentResult{Error: err}, err
 				}
@@ -1232,3 +1242,42 @@ func runInteractiveModeBubbleTea(_ context.Context, appInstance *app.App, modelN
 	_, runErr := program.Run()
 	return runErr
 }
+
+// sdkEventToSubagentEvent converts an SDK event to an extension-facing
+// SubagentEvent. Returns a zero-value event (Type=="") for events that
+// don't map to anything useful.
+func sdkEventToSubagentEvent(e kit.Event) extensions.SubagentEvent {
+	switch ev := e.(type) {
+	case kit.MessageUpdateEvent:
+		return extensions.SubagentEvent{Type: "text", Content: ev.Chunk}
+	case kit.ReasoningDeltaEvent:
+		return extensions.SubagentEvent{Type: "reasoning", Content: ev.Delta}
+	case kit.ToolCallEvent:
+		return extensions.SubagentEvent{
+			Type: "tool_call", ToolCallID: ev.ToolCallID,
+			ToolName: ev.ToolName, ToolKind: ev.ToolKind, ToolArgs: ev.ToolArgs,
+		}
+	case kit.ToolExecutionStartEvent:
+		return extensions.SubagentEvent{
+			Type: "tool_execution_start", ToolCallID: ev.ToolCallID,
+			ToolName: ev.ToolName, ToolKind: ev.ToolKind,
+		}
+	case kit.ToolExecutionEndEvent:
+		return extensions.SubagentEvent{
+			Type: "tool_execution_end", ToolCallID: ev.ToolCallID,
+			ToolName: ev.ToolName, ToolKind: ev.ToolKind,
+		}
+	case kit.ToolResultEvent:
+		return extensions.SubagentEvent{
+			Type: "tool_result", ToolCallID: ev.ToolCallID,
+			ToolName: ev.ToolName, ToolKind: ev.ToolKind,
+			ToolResult: ev.Result, IsError: ev.IsError,
+		}
+	case kit.TurnStartEvent:
+		return extensions.SubagentEvent{Type: "turn_start"}
+	case kit.TurnEndEvent:
+		return extensions.SubagentEvent{Type: "turn_end"}
+	default:
+		return extensions.SubagentEvent{}
+	}
+}

internal/acpserver/session.go

@@ -152,13 +152,22 @@ func (r *sessionRegistry) create(ctx context.Context, cwd string) (*acpSession,
 				return kitInstance.ExecuteCompletion(context.Background(), req)
 			},
 			SpawnSubagent: func(config extensions.SubagentConfig) (*extensions.SubagentHandle, *extensions.SubagentResult, error) {
-				result, err := kitInstance.Subagent(context.Background(), kit.SubagentConfig{
+				sdkCfg := kit.SubagentConfig{
 					Prompt:       config.Prompt,
 					Model:        config.Model,
 					SystemPrompt: config.SystemPrompt,
 					Timeout:      config.Timeout,
 					NoSession:    config.NoSession,
-				})
+				}
+				if config.OnEvent != nil {
+					sdkCfg.OnEvent = func(e kit.Event) {
+						se := sdkEventToSubagentEvent(e)
+						if se.Type != "" {
+							config.OnEvent(se)
+						}
+					}
+				}
+				result, err := kitInstance.Subagent(context.Background(), sdkCfg)
 				if result == nil {
 					return nil, &extensions.SubagentResult{Error: err}, err
 				}
@@ -246,3 +255,40 @@ func (s *acpSession) clearCancel() {
 	defer s.cancelMu.Unlock()
 	s.cancelFn = nil
 }
+
+// sdkEventToSubagentEvent converts an SDK event to an extension SubagentEvent.
+func sdkEventToSubagentEvent(e kit.Event) extensions.SubagentEvent {
+	switch ev := e.(type) {
+	case kit.MessageUpdateEvent:
+		return extensions.SubagentEvent{Type: "text", Content: ev.Chunk}
+	case kit.ReasoningDeltaEvent:
+		return extensions.SubagentEvent{Type: "reasoning", Content: ev.Delta}
+	case kit.ToolCallEvent:
+		return extensions.SubagentEvent{
+			Type: "tool_call", ToolCallID: ev.ToolCallID,
+			ToolName: ev.ToolName, ToolKind: ev.ToolKind, ToolArgs: ev.ToolArgs,
+		}
+	case kit.ToolExecutionStartEvent:
+		return extensions.SubagentEvent{
+			Type: "tool_execution_start", ToolCallID: ev.ToolCallID,
+			ToolName: ev.ToolName, ToolKind: ev.ToolKind,
+		}
+	case kit.ToolExecutionEndEvent:
+		return extensions.SubagentEvent{
+			Type: "tool_execution_end", ToolCallID: ev.ToolCallID,
+			ToolName: ev.ToolName, ToolKind: ev.ToolKind,
+		}
+	case kit.ToolResultEvent:
+		return extensions.SubagentEvent{
+			Type: "tool_result", ToolCallID: ev.ToolCallID,
+			ToolName: ev.ToolName, ToolKind: ev.ToolKind,
+			ToolResult: ev.Result, IsError: ev.IsError,
+		}
+	case kit.TurnStartEvent:
+		return extensions.SubagentEvent{Type: "turn_start"}
+	case kit.TurnEndEvent:
+		return extensions.SubagentEvent{Type: "turn_end"}
+	default:
+		return extensions.SubagentEvent{}
+	}
+}

internal/extensions/subagent.go

@@ -38,6 +38,11 @@ type SubagentConfig struct {
 	// Called from a goroutine; must be safe for concurrent use.
 	OnOutput func(chunk string)
 
+	// OnEvent receives real-time events from the subagent's execution:
+	// text chunks, tool calls, tool results, reasoning deltas, etc.
+	// Called synchronously from the subagent's event loop.
+	OnEvent func(SubagentEvent)
+
 	// OnComplete is called when the subagent finishes (success or error).
 	// Called from a goroutine; must be safe for concurrent use.
 	OnComplete func(result SubagentResult)
@@ -59,6 +64,33 @@ type SubagentConfig struct {
 	ParentSessionID string
 }
 
+// SubagentEvent carries a real-time event from a running subagent. Extensions
+// use the Type field to determine what happened and read the relevant fields.
+// This is a concrete struct (not an interface) for Yaegi compatibility.
+type SubagentEvent struct {
+	// Type identifies the event: "text", "reasoning", "tool_call",
+	// "tool_result", "tool_execution_start", "tool_execution_end",
+	// "turn_start", "turn_end".
+	Type string
+
+	// Content carries text for "text" and "reasoning" events.
+	Content string
+
+	// ToolCallID is set on tool_call, tool_result, tool_execution_start,
+	// and tool_execution_end events.
+	ToolCallID string
+	// ToolName is set on tool-related events.
+	ToolName string
+	// ToolKind is set on tool-related events.
+	ToolKind string
+	// ToolArgs is set on tool_call events (JSON-encoded).
+	ToolArgs string
+	// ToolResult is set on tool_result events.
+	ToolResult string
+	// IsError is set on tool_result events.
+	IsError bool
+}
+
 // SubagentResult contains the outcome of a subagent execution.
 type SubagentResult struct {
 	// Response is the subagent's final text response.

internal/extensions/symbols.go

@@ -115,6 +115,7 @@ func Symbols() interp.Exports {
 			"SubagentResult": reflect.ValueOf((*SubagentResult)(nil)),
 			"SubagentUsage":  reflect.ValueOf((*SubagentUsage)(nil)),
 			"SubagentHandle": reflect.ValueOf((*SubagentHandle)(nil)),
+			"SubagentEvent":  reflect.ValueOf((*SubagentEvent)(nil)),
 
 			// Event structs
 			"ToolCallEvent":           reflect.ValueOf((*ToolCallEvent)(nil)),

pkg/kit/events.go

@@ -198,7 +198,8 @@ type ToolResultEvent struct {
 
 // ToolResultMetadata carries structured data from tool executions.
 type ToolResultMetadata struct {
-	FileDiffs []FileDiffInfo `json:"file_diffs,omitempty"` // Present for edit/write tools
+	FileDiffs         []FileDiffInfo `json:"file_diffs,omitempty"`          // Present for edit/write tools
+	SubagentSessionID string         `json:"subagent_session_id,omitempty"` // Present for spawn_subagent tool
 }
 
 // FileDiffInfo describes a file modification from an edit or write tool.

pkg/kit/kit.go

@@ -1300,10 +1300,17 @@ func (m *Kit) Subagent(ctx context.Context, cfg SubagentConfig) (*SubagentResult
 	ctx, cancel := context.WithTimeout(ctx, timeout)
 	defer cancel()
 
-	// Fall back to parent's model.
+	// Resolve model: fall back to parent's model, and inherit the parent's
+	// provider when only a bare model name is given (e.g. "claude-haiku"
+	// instead of "anthropic/claude-haiku"). This avoids provider guessing.
 	model := cfg.Model
 	if model == "" {
 		model = m.modelString
+	} else if !strings.Contains(model, "/") {
+		// Bare model name — prepend parent's provider.
+		if parts := strings.SplitN(m.modelString, "/", 2); len(parts) == 2 {
+			model = parts[0] + "/" + model
+		}
 	}
 
 	// Default system prompt.
@@ -1318,15 +1325,33 @@ func (m *Kit) Subagent(ctx context.Context, cfg SubagentConfig) (*SubagentResult
 		tools = SubagentTools()
 	}
 
-	// Create child Kit instance.
-	child, err := New(ctx, &Options{
+	// Create child Kit instance. If the requested model fails (bad name,
+	// unsupported provider, etc.), fall back to the parent's model so the
+	// agent gets a useful error message instead of a hard failure.
+	childOpts := &Options{
 		Model:        model,
 		SystemPrompt: systemPrompt,
 		Tools:        tools,
 		NoSession:    cfg.NoSession,
 		Quiet:        true,
-	})
-	if err != nil {
+	}
+	child, err := New(ctx, childOpts)
+	if err != nil && model != m.modelString {
+		// Model-specific failure — retry with parent's model.
+		childOpts.Model = m.modelString
+		child, err = New(ctx, childOpts)
+		if err != nil {
+			return &SubagentResult{
+				Error:   fmt.Errorf("failed to create subagent: %w", err),
+				Elapsed: time.Since(start),
+			}, err
+		}
+		// Prepend a note so the agent knows which model is actually running.
+		cfg.Prompt = fmt.Sprintf(
+			"[Note: requested model %q was not available, using %s instead.]\n\n%s",
+			model, m.modelString, cfg.Prompt,
+		)
+	} else if err != nil {
 		return &SubagentResult{
 			Error:   fmt.Errorf("failed to create subagent: %w", err),
 			Elapsed: time.Since(start),
@@ -1383,6 +1408,9 @@ func (m *Kit) generate(ctx context.Context, messages []fantasy.Message) (*agent.
 			Model:        model,
 			SystemPrompt: systemPrompt,
 			Timeout:      timeout,
+			OnEvent: func(e Event) {
+				m.events.emit(e)
+			},
 		})
 		if result == nil {
 			return &core.SubagentSpawnResult{Error: err}, err