feat(model): Top5#1 结构化流事件 + WS 事件体系（对齐 OpenClaw AssistantMessageEvent）

- 新增 model/stream.go：StreamKind(text/thinking/tool_call 各 start/delta/end + tool_execution)
  + StreamEvent{Kind,Delta,Index,ID}。
- ChatStream 签名 onChunk func(delta string)→onEvent func(StreamEvent)；loop OnStream 同改；
  streamStep 转发结构化事件。
- openai：text_delta + text_start/text_end（正文三段式）；anthropic：文本块 text_*/tool_call_*
  按块 Index（content_block_stop 分支）真分段；fallback：有事件即交付。
- ws_hub：wsEvent 壳补 turnId/seq；新增 broadcastStream；streamChat 每帧打 turnId+seq；
  stream.go 把事件 publish 到 bus ws.stream。
- ws_bridge：streamEventData 映射 text_*→message.start/delta/end、thinking_*→thinking.*、
  tool_call_*→tool_call.*、tool_execution_update→tool_execution.update，未知回退 stream_chunk。
- 前端 ws.ts：解析 message.start/delta/end、thinking.start/delta/end(pendingThinking)、
  tool_call.start/end→addTool、tool_execution.update；保留旧 stream_chunk/thinking/tool_used 兼容；
  types.ts 补 turnId/seq。Docs/api-client.md 增 §3.1 v0.4。

已知限制（注释/文档标注）：turnId 在 OnStream→bus→relay 路径暂为空（StreamEvent 无 turnId 字段，
bus ws.stream 载荷不带 turn）；OpenAI adapter 未解析 tool_call 段；thinking 段两 adapter 暂不发；
tool_execution.update 是保留项（随工具循环钩子后置）。go build/vet/test + 前端 tsc 全绿。

internal/runtime/agent/agent_test.go

@@ -32,7 +32,7 @@ func (m *mockAdapter) Chat(_ context.Context, req model.Request, _ model.Options
 	return m.resp, m.err
 }
 
-func (m *mockAdapter) ChatStream(_ context.Context, _ model.Request, _ func(string)) (model.Response, error) {
+func (m *mockAdapter) ChatStream(_ context.Context, _ model.Request, _ func(model.StreamEvent)) (model.Response, error) {
 	return m.resp, m.err
 }
 

internal/runtime/loop/loop.go

@@ -20,6 +20,7 @@ import (
 	"git.yeij.top/AskaEth/Cyrene_v2/internal/runtime/agent"
 	"git.yeij.top/AskaEth/Cyrene_v2/internal/runtime/guardrail"
 	"git.yeij.top/AskaEth/Cyrene_v2/internal/runtime/memory"
+	"git.yeij.top/AskaEth/Cyrene_v2/internal/runtime/model"
 	"git.yeij.top/AskaEth/Cyrene_v2/internal/runtime/persist"
 	"git.yeij.top/AskaEth/Cyrene_v2/internal/runtime/tool"
 	"git.yeij.top/AskaEth/Cyrene_v2/internal/runtime/trace"
@@ -79,7 +80,7 @@ type Loop struct {
 	guards     *guardrail.Pipeline
 	personaID  string
 	maxRounds  int
-	onStream   func(delta string)
+	onStream   func(model.StreamEvent)
 	log        *slog.Logger
 }
 

internal/runtime/loop/loop_test.go

@@ -281,7 +281,7 @@ func TestRun_StreamDeltas(t *testing.T) {
 	var deltas []string
 	l := New(Options{
 		Agent:     a,
-		OnStream:  func(d string) { mu.Lock(); deltas = append(deltas, d); mu.Unlock() },
+		OnStream:  func(ev model.StreamEvent) { mu.Lock(); deltas = append(deltas, ev.Delta); mu.Unlock() },
 		MaxRounds: 8,
 	})
 
@@ -306,7 +306,7 @@ func TestRun_StreamGuardrailBlocks(t *testing.T) {
 	pipe := guardrail.New(guardrail.WithGuard(g))
 	ad := &mockAdapter{}
 	a := newTestAgent(t, ad, nil)
-	l := New(Options{Agent: a, Guards: pipe, OnStream: func(string) {}, MaxRounds: 8})
+	l := New(Options{Agent: a, Guards: pipe, OnStream: func(model.StreamEvent) {}, MaxRounds: 8})
 
 	res, err := l.Run(context.Background(), "sess", []model.Message{model.TextMessage(model.RoleUser, "hi")})
 	if err != nil {

internal/runtime/loop/mocks_test.go

@@ -59,14 +59,14 @@ func (m *mockAdapter) Chat(_ context.Context, req model.Request, _ model.Options
 	return r.resp, r.err
 }
 
-func (m *mockAdapter) ChatStream(_ context.Context, req model.Request, on func(string)) (model.Response, error) {
+func (m *mockAdapter) ChatStream(_ context.Context, req model.Request, on func(model.StreamEvent)) (model.Response, error) {
 	m.streamReqs = append(m.streamReqs, req)
 	i := m.streamCalls
 	m.streamCalls++
 	if i < len(m.chunks) {
 		for _, c := range m.chunks[i] {
 			if on != nil {
-				on(c)
+				on(model.StreamEvent{Kind: model.StreamKindTextDelta, Delta: c})
 			}
 		}
 	}

internal/runtime/loop/options.go

@@ -6,6 +6,7 @@ import (
 	"git.yeij.top/AskaEth/Cyrene_v2/internal/runtime/agent"
 	"git.yeij.top/AskaEth/Cyrene_v2/internal/runtime/guardrail"
 	"git.yeij.top/AskaEth/Cyrene_v2/internal/runtime/memory"
+	"git.yeij.top/AskaEth/Cyrene_v2/internal/runtime/model"
 	"git.yeij.top/AskaEth/Cyrene_v2/internal/runtime/persist"
 	"git.yeij.top/AskaEth/Cyrene_v2/internal/runtime/tool"
 	"git.yeij.top/AskaEth/Cyrene_v2/internal/runtime/trace"
@@ -47,9 +48,10 @@ type Options struct {
 	// DefaultMaxRounds (8).
 	MaxRounds int
 	// OnStream, when non-nil, switches the loop to the streaming path: the model
-	// adapter's ChatStream is driven directly and each token delta is forwarded
-	// to this callback.
-	OnStream func(delta string)
+	// adapter's ChatStream is driven directly and each structured stream event is
+	// forwarded to this callback (model.StreamEvent), so the frontend can render
+	// body text, tool calls and (eventually) reasoning segments independently.
+	OnStream func(model.StreamEvent)
 	// Log is the base logger. Nil is replaced with a discard logger tagged with
 	// source "runtime/loop".
 	Log *slog.Logger

internal/runtime/loop/stream.go

@@ -31,9 +31,9 @@ func (l *Loop) streamStep(ctx context.Context, messages []model.Message) (*stepO
 		}
 	}
 
-	resp, err := adapter.ChatStream(ctx, req, func(delta string) {
+	resp, err := adapter.ChatStream(ctx, req, func(ev model.StreamEvent) {
 		if l.onStream != nil {
-			l.onStream(delta)
+			l.onStream(ev)
 		}
 	})
 	if err != nil {

internal/runtime/memory/llmextractor_test.go

@@ -25,7 +25,7 @@ func (m *mockAdapter) Chat(ctx context.Context, req model.Request, opts model.Op
 	return model.Response{Content: "[]"}, nil
 }
 
-func (m *mockAdapter) ChatStream(ctx context.Context, req model.Request, onChunk func(delta string)) (model.Response, error) {
+func (m *mockAdapter) ChatStream(ctx context.Context, req model.Request, onEvent func(model.StreamEvent)) (model.Response, error) {
 	return model.Response{}, model.ErrStream
 }
 

internal/runtime/model/adapter.go

@@ -34,8 +34,11 @@ type Adapter interface {
 	Name() string
 	// Chat performs a non-streaming completion and returns the full response.
 	Chat(ctx context.Context, req Request, opts Options) (Response, error)
-	// ChatStream streams token-level deltas via onChunk and returns the
-	// aggregated response (with usage when the provider reports it). onChunk may
-	// be nil to discard deltas while still aggregating.
-	ChatStream(ctx context.Context, req Request, onChunk func(delta string)) (Response, error)
+	// ChatStream streams structured events via onEvent and returns the aggregated
+	// response (with usage when the provider reports it). onEvent may be nil to
+	// discard events while still aggregating. Every provider-supported segment is
+	// bracketed (text_start/delta/end, tool_call_start/delta/end), so the consumer
+	// can render each independently; segments adapters cannot yet distinguish are
+	// delivered as text_delta events.
+	ChatStream(ctx context.Context, req Request, onEvent func(StreamEvent)) (Response, error)
 }

internal/runtime/model/anthropic.go

@@ -169,9 +169,12 @@ func (a *AnthropicChatAdapter) Chat(ctx context.Context, req Request, opts Optio
 	return out, nil
 }
 
-// ChatStream streams content-block deltas via onChunk and returns the aggregated
-// response with usage when the provider reports it.
-func (a *AnthropicChatAdapter) ChatStream(ctx context.Context, req Request, onChunk func(delta string)) (Response, error) {
+// ChatStream streams structured events via onEvent and returns the aggregated
+// response with usage when the provider reports it. Text blocks are delivered as
+// text_start/text_delta/text_end events; tool_use blocks are delivered as
+// tool_call_start/tool_call_delta/tool_call_end so the frontend can render each
+// segment independently.
+func (a *AnthropicChatAdapter) ChatStream(ctx context.Context, req Request, onEvent func(StreamEvent)) (Response, error) {
 	start := time.Now()
 	if a.baseURL == "" {
 		return Response{}, ErrUpstream
@@ -197,7 +200,7 @@ func (a *AnthropicChatAdapter) ChatStream(ctx context.Context, req Request, onCh
 	if resp.StatusCode != http.StatusOK {
 		return Response{}, a.upstreamError(resp)
 	}
-	out, err := scanAnthropicSSE(resp.Body, onChunk)
+	out, err := scanAnthropicSSE(resp.Body, onEvent)
 	if err != nil {
 		return Response{}, err
 	}

internal/runtime/model/anthropic_stream.go

@@ -52,11 +52,13 @@ type streamBlock struct {
 }
 
 // scanAnthropicSSE incrementally decodes Anthropic's content-block stream. Text
-// deltas are forwarded to onChunk; tool_use input_json_delta fragments are
-// accumulated per block and re-assembled into a structured Args map when the block
-// stops. The stream must terminate with a message_stop event, otherwise ErrStream
-// is returned.
-func scanAnthropicSSE(r io.Reader, onChunk func(string)) (Response, error) {
+// deltas are forwarded as text_delta events (segment bracketed by
+// text_start/text_end); tool_use input_json_delta fragments are forwarded as
+// tool_call_delta events (segment bracketed by tool_call_start/tool_call_end)
+// and accumulated per block so they re-assemble into a structured Args map when
+// the block stops. The stream must terminate with a message_stop event,
+// otherwise ErrStream is returned.
+func scanAnthropicSSE(r io.Reader, onEvent func(StreamEvent)) (Response, error) {
 	scanner := bufio.NewScanner(r)
 	scanner.Buffer(make([]byte, 0, sseBufInit), maxSSELineBytes)
 	agg := Response{}
@@ -78,7 +80,7 @@ func scanAnthropicSSE(r io.Reader, onChunk func(string)) (Response, error) {
 		if err := json.Unmarshal([]byte(data), &evt); err != nil {
 			return Response{}, fmt.Errorf("model: %w: decode stream chunk: %v", ErrUpstream, err)
 		}
-		if err := applyAnthropicEvent(&agg, blocks, &order, &text, evt, onChunk); err != nil {
+		if err := applyAnthropicEvent(&agg, blocks, &order, &text, evt, onEvent); err != nil {
 			return Response{}, err
 		}
 		if evt.Type == "message_stop" {
@@ -102,7 +104,7 @@ func applyAnthropicEvent(
 	order *[]int,
 	text *strings.Builder,
 	evt anthropicStreamEvent,
-	onChunk func(string),
+	onEvent func(StreamEvent),
 ) error {
 	switch evt.Type {
 	case "message_start":
@@ -123,11 +125,21 @@ func applyAnthropicEvent(
 			name:        evt.Content.Name,
 			initialArgs: evt.Content.Input,
 		}
-		if evt.Content.Type == "text" && evt.Content.Text != "" {
-			b.text.WriteString(evt.Content.Text)
-			text.WriteString(evt.Content.Text)
-			if onChunk != nil {
-				onChunk(evt.Content.Text)
+		switch evt.Content.Type {
+		case "text":
+			if onEvent != nil {
+				onEvent(StreamEvent{Kind: StreamKindTextStart, Index: *evt.Index})
+			}
+			if evt.Content.Text != "" {
+				b.text.WriteString(evt.Content.Text)
+				text.WriteString(evt.Content.Text)
+				if onEvent != nil {
+					onEvent(StreamEvent{Kind: StreamKindTextDelta, Delta: evt.Content.Text, Index: *evt.Index})
+				}
+			}
+		case "tool_use":
+			if onEvent != nil {
+				onEvent(StreamEvent{Kind: StreamKindToolCallStart, Index: *evt.Index, ID: evt.Content.ID})
 			}
 		}
 		if _, ok := blocks[*evt.Index]; !ok {
@@ -146,11 +158,31 @@ func applyAnthropicEvent(
 		case "text_delta":
 			b.text.WriteString(evt.Delta.Text)
 			text.WriteString(evt.Delta.Text)
-			if onChunk != nil {
-				onChunk(evt.Delta.Text)
+			if onEvent != nil {
+				onEvent(StreamEvent{Kind: StreamKindTextDelta, Delta: evt.Delta.Text, Index: *evt.Index})
 			}
 		case "input_json_delta":
 			b.input.WriteString(evt.Delta.PartialJSON)
+			if onEvent != nil {
+				onEvent(StreamEvent{Kind: StreamKindToolCallDelta, Delta: evt.Delta.PartialJSON, Index: *evt.Index, ID: b.id})
+			}
+		}
+	case "content_block_stop":
+		if evt.Index == nil {
+			return nil
+		}
+		b := blocks[*evt.Index]
+		if b == nil {
+			return nil
+		}
+		if b.typ == "text" {
+			if onEvent != nil {
+				onEvent(StreamEvent{Kind: StreamKindTextEnd, Index: *evt.Index})
+			}
+		} else if b.typ == "tool_use" {
+			if onEvent != nil {
+				onEvent(StreamEvent{Kind: StreamKindToolCallEnd, Index: *evt.Index, ID: b.id})
+			}
 		}
 	case "message_delta":
 		if evt.Usage != nil {

internal/runtime/model/anthropic_test.go

@@ -323,10 +323,10 @@ func TestAnthropicChat_ChatStream_Text(t *testing.T) {
 	ad := NewAnthropicChat(config.LLMConfig{AnthropicBaseURL: srv.URL, AnthropicModel: "claude-test"},
 		WithAnthropicRecorder(func(cr CallRecord) { recs = append(recs, cr) }))
 
-	var deltas []string
+	var events []StreamEvent
 	resp, err := ad.ChatStream(context.Background(),
 		Request{Messages: []Message{TextMessage(RoleUser, "hi")}, Model: "claude-test", Purpose: "chat"},
-		func(d string) { deltas = append(deltas, d) })
+		func(ev StreamEvent) { events = append(events, ev) })
 	if err != nil {
 		t.Fatalf("ChatStream error: %v", err)
 	}
@@ -348,8 +348,14 @@ func TestAnthropicChat_ChatStream_Text(t *testing.T) {
 	if resp.TotalTokens != 7 {
 		t.Errorf("resp.TotalTokens = %d, want 7", resp.TotalTokens)
 	}
-	if !reflect.DeepEqual(deltas, []string{"Hel", "lo"}) {
-		t.Errorf("deltas = %v, want [Hel lo]", deltas)
+	wantEvents := []StreamEvent{
+		{Kind: StreamKindTextStart, Index: 0},
+		{Kind: StreamKindTextDelta, Index: 0, Delta: "Hel"},
+		{Kind: StreamKindTextDelta, Index: 0, Delta: "lo"},
+		{Kind: StreamKindTextEnd, Index: 0},
+	}
+	if !reflect.DeepEqual(events, wantEvents) {
+		t.Errorf("events = %+v, want %+v", events, wantEvents)
 	}
 	if len(recs) != 1 || recs[0].Tokens != 7 || recs[0].Purpose != "chat" {
 		t.Errorf("records = %+v, want 1 record tokens=7 purpose=chat", recs)
@@ -377,10 +383,10 @@ func TestAnthropicChat_ChatStream_ToolUseReassembly(t *testing.T) {
 	srv := newAnthropicServer(t, http.StatusOK, "text/event-stream", sse, nil)
 	ad := NewAnthropicChat(config.LLMConfig{AnthropicBaseURL: srv.URL, AnthropicModel: "claude-test"})
 
-	var deltas []string
+	var events []StreamEvent
 	resp, err := ad.ChatStream(context.Background(),
 		Request{Messages: []Message{TextMessage(RoleUser, "hi")}, Model: "claude-test"},
-		func(d string) { deltas = append(deltas, d) })
+		func(ev StreamEvent) { events = append(events, ev) })
 	if err != nil {
 		t.Fatalf("ChatStream error: %v", err)
 	}
@@ -401,8 +407,14 @@ func TestAnthropicChat_ChatStream_ToolUseReassembly(t *testing.T) {
 	if resp.TotalTokens != 18 {
 		t.Errorf("resp.TotalTokens = %d, want 18", resp.TotalTokens)
 	}
-	if len(deltas) != 0 {
-		t.Errorf("deltas = %v, want none (only tool_use)", deltas)
+	wantEvents := []StreamEvent{
+		{Kind: StreamKindToolCallStart, Index: 0, ID: "toolu_1"},
+		{Kind: StreamKindToolCallDelta, Index: 0, ID: "toolu_1", Delta: `{"location":`},
+		{Kind: StreamKindToolCallDelta, Index: 0, ID: "toolu_1", Delta: `"Paris"}`},
+		{Kind: StreamKindToolCallEnd, Index: 0, ID: "toolu_1"},
+	}
+	if !reflect.DeepEqual(events, wantEvents) {
+		t.Errorf("events = %+v, want %+v", events, wantEvents)
 	}
 }
 

internal/runtime/model/fallback.go

@@ -60,10 +60,10 @@ func (c *Chain) Chat(ctx context.Context, req Request, opts Options) (Response,
 }
 
 // ChatStream tries each step in order. If a step fails before delivering any
-// delta, the chain moves to the next step; once a step has delivered output it
+// event, the chain moves to the next step; once a step has delivered output it
 // is committed, so a mid-stream failure surfaces as an error rather than mixing
 // content across providers.
-func (c *Chain) ChatStream(ctx context.Context, req Request, onChunk func(delta string)) (Response, error) {
+func (c *Chain) ChatStream(ctx context.Context, req Request, onEvent func(StreamEvent)) (Response, error) {
 	if len(c.steps) == 0 {
 		return Response{}, ErrNoSteps
 	}
@@ -74,10 +74,10 @@ func (c *Chain) ChatStream(ctx context.Context, req Request, onChunk func(delta
 			stepReq.Model = s.Model
 		}
 		delivered := false
-		wrapped := func(delta string) {
+		wrapped := func(ev StreamEvent) {
 			delivered = true
-			if onChunk != nil {
-				onChunk(delta)
+			if onEvent != nil {
+				onEvent(ev)
 			}
 		}
 		resp, err := s.Adapter.ChatStream(ctx, stepReq, wrapped)

internal/runtime/model/openai.go

@@ -194,9 +194,9 @@ func (a *OpenAIChatAdapter) Chat(ctx context.Context, req Request, opts Options)
 	return out, nil
 }
 
-// ChatStream streams token-level deltas via onChunk and returns the aggregated
+// ChatStream streams structured events via onEvent and returns the aggregated
 // response with usage when the provider reports it in the final chunk.
-func (a *OpenAIChatAdapter) ChatStream(ctx context.Context, req Request, onChunk func(delta string)) (Response, error) {
+func (a *OpenAIChatAdapter) ChatStream(ctx context.Context, req Request, onEvent func(StreamEvent)) (Response, error) {
 	start := time.Now()
 	if a.baseURL == "" {
 		return Response{}, ErrUpstream
@@ -222,7 +222,7 @@ func (a *OpenAIChatAdapter) ChatStream(ctx context.Context, req Request, onChunk
 	if resp.StatusCode != http.StatusOK {
 		return Response{}, a.upstreamError(resp)
 	}
-	out, err := scanSSE(resp.Body, onChunk)
+	out, err := scanSSE(resp.Body, onEvent)
 	if err != nil {
 		return Response{}, err
 	}
@@ -380,12 +380,14 @@ func responseFromWire(wire *openAIChatResponse) Response {
 
 // scanSSE incrementally decodes stream chunks, accumulates the full content
 // with a strings.Builder (never reading the whole body at once) and captures
-// usage from the final chunk.
-func scanSSE(r io.Reader, onChunk func(string)) (Response, error) {
+// usage from the final chunk. Each text delta is delivered as a text_delta
+// StreamEvent with the body-text segment bracketed by text_start/text_end.
+func scanSSE(r io.Reader, onEvent func(StreamEvent)) (Response, error) {
 	scanner := bufio.NewScanner(r)
 	scanner.Buffer(make([]byte, 0, sseBufInit), maxSSELineBytes)
 	agg := Response{}
 	var b strings.Builder
+	started := false
 	for scanner.Scan() {
 		line := strings.TrimSpace(scanner.Text())
 		if line == "" || !strings.HasPrefix(line, sseDataPrefix) {
@@ -412,13 +414,20 @@ func scanSSE(r io.Reader, onChunk func(string)) (Response, error) {
 			continue
 		}
 		b.WriteString(delta)
-		if onChunk != nil {
-			onChunk(delta)
+		if onEvent != nil {
+			if !started {
+				started = true
+				onEvent(StreamEvent{Kind: StreamKindTextStart})
+			}
+			onEvent(StreamEvent{Kind: StreamKindTextDelta, Delta: delta})
 		}
 	}
 	if err := scanner.Err(); err != nil {
 		return Response{}, fmt.Errorf("model: %w: read stream: %v", ErrUpstream, err)
 	}
+	if onEvent != nil && started {
+		onEvent(StreamEvent{Kind: StreamKindTextEnd})
+	}
 	agg.Content = b.String()
 	agg.Message = Message{Role: RoleAssistant, Content: []Content{{Type: ContentTypeText, Text: agg.Content}}}
 	return agg, nil

internal/runtime/model/openai_test.go

@@ -200,10 +200,10 @@ func TestOpenAIChat_ChatStream_SSE(t *testing.T) {
 	ad := NewOpenAIChat(config.LLMConfig{BaseURL: srv.URL, Model: "gpt-test"},
 		WithRecorder(func(cr CallRecord) { recs = append(recs, cr) }))
 
-	var deltas []string
+	var events []StreamEvent
 	resp, err := ad.ChatStream(context.Background(),
 		Request{Messages: []Message{TextMessage(RoleUser, "hi")}, Model: "gpt-test", Purpose: "chat"},
-		func(d string) { deltas = append(deltas, d) })
+		func(ev StreamEvent) { events = append(events, ev) })
 	if err != nil {
 		t.Fatalf("ChatStream error: %v", err)
 	}
@@ -216,8 +216,14 @@ func TestOpenAIChat_ChatStream_SSE(t *testing.T) {
 	if resp.TotalTokens != 7 {
 		t.Errorf("resp.TotalTokens = %d, want 7", resp.TotalTokens)
 	}
-	if !reflect.DeepEqual(deltas, []string{"Hel", "lo"}) {
-		t.Errorf("deltas = %v, want [Hel lo]", deltas)
+	wantEvents := []StreamEvent{
+		{Kind: StreamKindTextStart},
+		{Kind: StreamKindTextDelta, Delta: "Hel"},
+		{Kind: StreamKindTextDelta, Delta: "lo"},
+		{Kind: StreamKindTextEnd},
+	}
+	if !reflect.DeepEqual(events, wantEvents) {
+		t.Errorf("events = %+v, want %+v", events, wantEvents)
 	}
 	if len(recs) != 1 || recs[0].Tokens != 7 || recs[0].Purpose != "chat" {
 		t.Errorf("records = %+v, want 1 record tokens=7 purpose=chat", recs)

internal/runtime/model/stream.go

@@ -0,0 +1,60 @@
+package model
+
+// StreamKind enumerates the kinds of structured events produced while a
+// completion streams. It mirrors OpenClaw's AssistantMessageEvent segments
+// (text / thinking / tool_call) plus a tool-execution progress event, so the
+// frontend can render each segment into its own surface (body, collapsed
+// thinking block, tool card) rather than accumulating a single opaque token
+// stream.
+type StreamKind string
+
+const (
+	// StreamKindTextStart opens the body-text segment. The single text segment
+	// of a response is bracketed by TextStart/TextEnd; deltas fill it.
+	StreamKindTextStart StreamKind = "text_start"
+	// StreamKindTextDelta is one body-text token fragment.
+	StreamKindTextDelta StreamKind = "text_delta"
+	// StreamKindTextEnd closes the body-text segment.
+	StreamKindTextEnd StreamKind = "text_end"
+
+	// StreamKindThinkingStart opens a chain-of-thought segment (frontend
+	// collapsed block). Reserved: adapters that report reasoning emit it.
+	StreamKindThinkingStart StreamKind = "thinking_start"
+	// StreamKindThinkingDelta is one reasoning token fragment.
+	StreamKindThinkingDelta StreamKind = "thinking_delta"
+	// StreamKindThinkingEnd closes a reasoning segment.
+	StreamKindThinkingEnd StreamKind = "thinking_end"
+
+	// StreamKindToolCallStart opens a tool invocation's streaming form.
+	StreamKindToolCallStart StreamKind = "tool_call_start"
+	// StreamKindToolCallDelta is a fragment of the tool arguments (e.g. the
+	// incremental input_json of an Anthropic tool_use block).
+	StreamKindToolCallDelta StreamKind = "tool_call_delta"
+	// StreamKindToolCallEnd closes a tool invocation block.
+	StreamKindToolCallEnd StreamKind = "tool_call_end"
+
+	// StreamKindToolExecution reports intermediate progress while the loop runs
+	// a tool that the model requested (design/04 §1.1 tool_execution_update). It
+	// is emitted by the tool loop, not the model adapter; reserved for a later
+	// milestone, but the wire mapping is defined so the frontend can react.
+	StreamKindToolExecution StreamKind = "tool_execution_update"
+)
+
+// StreamEvent is a single structured event in a streamed completion. It replaces
+// the former plain text delta as the unit delivered by Adapter.ChatStream, so a
+// consumer can distinguish body text from tool calls (and, in time, reasoning
+// segments) and track each by Index/ID.
+type StreamEvent struct {
+	// Kind classifies the event (see StreamKind).
+	Kind StreamKind
+	// Delta carries the incremental payload: body text for TextDelta, reasoning
+	// text for ThinkingDelta, or a partial_argument fragment for ToolCallDelta.
+	Delta string
+	// Index is the zero-based content-block index the event belongs to, when the
+	// provider reports one. The frontend uses it to correlate a segment's
+	// start/delta/end events.
+	Index int
+	// ID is the provider block/index identifier for a tool call (e.g. Anthropic's
+	// tool_use block id). Empty for text segments.
+	ID string
+}

internal/runtime/orchestration/scheduler_test.go

@@ -104,7 +104,7 @@ func (m *mockAdapter) Chat(context.Context, model.Request, model.Options) (model
 	return m.resp, m.err
 }
 
-func (m *mockAdapter) ChatStream(context.Context, model.Request, func(string)) (model.Response, error) {
+func (m *mockAdapter) ChatStream(context.Context, model.Request, func(model.StreamEvent)) (model.Response, error) {
 	return m.resp, m.err
 }