fix(reasoning): persist canonical history for DeepSeek and web chat

pkg/agent/agent_test.go

@@ -1720,6 +1720,38 @@ func (m *messageToolProvider) GetDefaultModel() string {
 	return "message-tool-model"
 }
 
+type reasoningVisibleToolProvider struct {
+	filePath string
+	calls    int
+}
+
+func (m *reasoningVisibleToolProvider) Chat(
+	ctx context.Context,
+	messages []providers.Message,
+	tools []providers.ToolDefinition,
+	model string,
+	opts map[string]any,
+) (*providers.LLMResponse, error) {
+	m.calls++
+	if m.calls == 1 {
+		return &providers.LLMResponse{
+			Content:          "I'll inspect that file now.",
+			ReasoningContent: "Read the file before answering.",
+			ToolCalls: []providers.ToolCall{{
+				ID:        "call_read_file",
+				Type:      "function",
+				Name:      "read_file",
+				Arguments: map[string]any{"path": m.filePath},
+			}},
+		}, nil
+	}
+	return &providers.LLMResponse{Content: "DONE"}, nil
+}
+
+func (m *reasoningVisibleToolProvider) GetDefaultModel() string {
+	return "reasoning-visible-tool-model"
+}
+
 type artifactThenSendProvider struct {
 	calls int
 }
@@ -1866,6 +1898,28 @@ func TestToolFeedbackExplanationFromResponse_UsesCurrentContentFirst(t *testing.
 	}
 }
 
+func TestSideQuestionResponseContent_FallsBackWhenContentIsWhitespace(t *testing.T) {
+	response := &providers.LLMResponse{
+		Content:          " \n\t ",
+		ReasoningContent: "reasoning fallback",
+	}
+
+	if got := sideQuestionResponseContent(response); got != "reasoning fallback" {
+		t.Fatalf("sideQuestionResponseContent() = %q, want %q", got, "reasoning fallback")
+	}
+}
+
+func TestResponseReasoningContent_FallsBackWhenReasoningIsWhitespace(t *testing.T) {
+	response := &providers.LLMResponse{
+		Reasoning:        " \n\t ",
+		ReasoningContent: "structured reasoning fallback",
+	}
+
+	if got := responseReasoningContent(response); got != "structured reasoning fallback" {
+		t.Fatalf("responseReasoningContent() = %q, want %q", got, "structured reasoning fallback")
+	}
+}
+
 func TestToolFeedbackExplanationFromResponse_UsesExplicitToolCallExtraContent(t *testing.T) {
 	response := &providers.LLMResponse{
 		ToolCalls: []providers.ToolCall{{
@@ -3957,6 +4011,182 @@ func TestProcessMessage_PublishesToolFeedbackWhenEnabled(t *testing.T) {
 	}
 }
 
+func TestProcessMessage_PersistsReasoningContentInSessionHistory(t *testing.T) {
+	tmpDir := t.TempDir()
+	cfg := &config.Config{
+		Agents: config.AgentsConfig{
+			Defaults: config.AgentDefaults{
+				Workspace:         tmpDir,
+				ModelName:         "test-model",
+				MaxTokens:         4096,
+				MaxToolIterations: 10,
+			},
+		},
+	}
+
+	msgBus := bus.NewMessageBus()
+	provider := &reasoningContentProvider{
+		response:         "final answer",
+		reasoningContent: "thinking trace",
+	}
+	al := NewAgentLoop(cfg, msgBus, provider)
+
+	response, err := al.processMessage(context.Background(), bus.InboundMessage{
+		Channel:  "pico",
+		SenderID: "user1",
+		ChatID:   "pico:test-session",
+		Content:  "hello",
+	})
+	if err != nil {
+		t.Fatalf("processMessage() error = %v", err)
+	}
+	if response != "final answer" {
+		t.Fatalf("processMessage() response = %q, want %q", response, "final answer")
+	}
+
+	store := al.GetRegistry().GetDefaultAgent().Sessions
+	sessionKeys := store.ListSessions()
+	if len(sessionKeys) != 1 {
+		t.Fatalf("session keys = %v, want exactly 1 active session", sessionKeys)
+	}
+	history := store.GetHistory(sessionKeys[0])
+	if len(history) < 2 {
+		t.Fatalf("session history len = %d, want at least 2", len(history))
+	}
+
+	last := history[len(history)-1]
+	if last.Role != "assistant" {
+		t.Fatalf("last message role = %q, want assistant", last.Role)
+	}
+	if last.Content != "final answer" {
+		t.Fatalf("last message content = %q, want %q", last.Content, "final answer")
+	}
+	if last.ReasoningContent != "thinking trace" {
+		t.Fatalf("last message reasoning_content = %q, want %q", last.ReasoningContent, "thinking trace")
+	}
+}
+
+func TestProcessMessage_PersistsReasoningToolResponseAsSingleAssistantRecord(t *testing.T) {
+	tmpDir := t.TempDir()
+	inspectPath := filepath.Join(tmpDir, "inspect.txt")
+	if err := os.WriteFile(inspectPath, []byte("inspect me"), 0o644); err != nil {
+		t.Fatalf("WriteFile(inspectPath) error = %v", err)
+	}
+
+	cfg := config.DefaultConfig()
+	cfg.Agents.Defaults.Workspace = tmpDir
+	cfg.Agents.Defaults.ModelName = "test-model"
+	cfg.Agents.Defaults.MaxTokens = 4096
+	cfg.Agents.Defaults.MaxToolIterations = 10
+
+	msgBus := bus.NewMessageBus()
+	provider := &reasoningVisibleToolProvider{filePath: inspectPath}
+	al := NewAgentLoop(cfg, msgBus, provider)
+
+	response, err := al.processMessage(context.Background(), bus.InboundMessage{
+		Channel:  "telegram",
+		SenderID: "user1",
+		ChatID:   "chat1",
+		Content:  "hello",
+	})
+	if err != nil {
+		t.Fatalf("processMessage() error = %v", err)
+	}
+	if response != "DONE" {
+		t.Fatalf("processMessage() response = %q, want %q", response, "DONE")
+	}
+
+	store := al.GetRegistry().GetDefaultAgent().Sessions
+	sessionKeys := store.ListSessions()
+	if len(sessionKeys) != 1 {
+		t.Fatalf("session keys = %v, want exactly 1 active session", sessionKeys)
+	}
+
+	history := store.GetHistory(sessionKeys[0])
+	if len(history) < 3 {
+		t.Fatalf("session history len = %d, want at least 3", len(history))
+	}
+
+	var assistantWithToolCall *providers.Message
+	for i := range history {
+		msg := history[i]
+		if msg.Role == "assistant" && len(msg.ToolCalls) > 0 {
+			assistantWithToolCall = &msg
+			break
+		}
+	}
+	if assistantWithToolCall == nil {
+		t.Fatal("expected assistant history record with tool_calls")
+	}
+	if assistantWithToolCall.Content != "I'll inspect that file now." {
+		t.Fatalf("assistant content = %q, want %q", assistantWithToolCall.Content, "I'll inspect that file now.")
+	}
+	if assistantWithToolCall.ReasoningContent != "Read the file before answering." {
+		t.Fatalf("assistant reasoning_content = %q, want preserved", assistantWithToolCall.ReasoningContent)
+	}
+	if len(assistantWithToolCall.ToolCalls) != 1 {
+		t.Fatalf("assistant tool calls = %+v, want single read_file tool", assistantWithToolCall.ToolCalls)
+	}
+	if got := providers.NormalizeToolCall(assistantWithToolCall.ToolCalls[0]).Name; got != "read_file" {
+		t.Fatalf("assistant tool calls = %+v, want single read_file tool", assistantWithToolCall.ToolCalls)
+	}
+
+	sessionDir := filepath.Join(tmpDir, "sessions")
+	entries, err := os.ReadDir(sessionDir)
+	if err != nil {
+		t.Fatalf("ReadDir(%q) error = %v", sessionDir, err)
+	}
+
+	var jsonlPath string
+	for _, entry := range entries {
+		if entry.IsDir() || !strings.HasSuffix(entry.Name(), ".jsonl") {
+			continue
+		}
+		jsonlPath = filepath.Join(sessionDir, entry.Name())
+		break
+	}
+	if jsonlPath == "" {
+		t.Fatal("expected session jsonl file to be created")
+	}
+
+	data, err := os.ReadFile(jsonlPath)
+	if err != nil {
+		t.Fatalf("ReadFile(%q) error = %v", jsonlPath, err)
+	}
+
+	lines := strings.Split(strings.TrimSpace(string(data)), "\n")
+	if len(lines) < 3 {
+		t.Fatalf("jsonl lines = %d, want at least 3", len(lines))
+	}
+
+	matchingRecords := 0
+	for _, line := range lines {
+		var msg providers.Message
+		if err := json.Unmarshal([]byte(line), &msg); err != nil {
+			t.Fatalf("Unmarshal(jsonl line) error = %v", err)
+		}
+		if msg.Role != "assistant" {
+			continue
+		}
+		if msg.Content == "I'll inspect that file now." || msg.ReasoningContent == "Read the file before answering." {
+			matchingRecords++
+			toolName := ""
+			if len(msg.ToolCalls) == 1 {
+				toolName = providers.NormalizeToolCall(msg.ToolCalls[0]).Name
+			}
+			if msg.Content != "I'll inspect that file now." ||
+				msg.ReasoningContent != "Read the file before answering." ||
+				len(msg.ToolCalls) != 1 ||
+				toolName != "read_file" {
+				t.Fatalf("assistant jsonl record = %+v, want content+reasoning+tool_calls in one line", msg)
+			}
+		}
+	}
+	if matchingRecords != 1 {
+		t.Fatalf("matching assistant jsonl records = %d, want exactly 1 canonical assistant record", matchingRecords)
+	}
+}
+
 func TestProcessMessage_DoesNotLeakReasoningContentInToolFeedback(t *testing.T) {
 	tmpDir := t.TempDir()
 	heartbeatFile := filepath.Join(tmpDir, "tool-feedback-reasoning.txt")

pkg/agent/agent_utils.go

@@ -5,6 +5,7 @@ package agent
 import (
 	"context"
 	"fmt"
+	"maps"
 	"path/filepath"
 	"strings"
 	"time"
@@ -465,17 +466,28 @@ func sideQuestionResponseContent(response *providers.LLMResponse) string {
 	if response == nil {
 		return ""
 	}
-	if response.Content != "" {
+	if strings.TrimSpace(response.Content) != "" {
 		return response.Content
 	}
-	return response.ReasoningContent
+	return responseReasoningContent(response)
+}
+
+func responseReasoningContent(response *providers.LLMResponse) string {
+	if response == nil {
+		return ""
+	}
+	if strings.TrimSpace(response.Reasoning) != "" {
+		return response.Reasoning
+	}
+	if strings.TrimSpace(response.ReasoningContent) != "" {
+		return response.ReasoningContent
+	}
+	return ""
 }
 
 func shallowCloneLLMOptions(opts map[string]any) map[string]any {
 	clone := make(map[string]any, len(opts))
-	for k, v := range opts {
-		clone[k] = v
-	}
+	maps.Copy(clone, opts)
 	return clone
 }
 

pkg/agent/pipeline_finalize.go

@@ -40,8 +40,12 @@ func (p *Pipeline) Finalize(
 	ts.setPhase(TurnPhaseFinalizing)
 	ts.setFinalContent(finalContent)
 	if !ts.opts.NoHistory {
-		finalMsg := providers.Message{Role: "assistant", Content: finalContent}
-		ts.agent.Sessions.AddMessage(ts.sessionKey, finalMsg.Role, finalMsg.Content)
+		finalMsg := providers.Message{
+			Role:             "assistant",
+			Content:          finalContent,
+			ReasoningContent: responseReasoningContent(exec.response),
+		}
+		ts.agent.Sessions.AddFullMessage(ts.sessionKey, finalMsg)
 		ts.recordPersistedMessage(finalMsg)
 		ts.ingestMessage(turnCtx, al, finalMsg)
 		if err := ts.agent.Sessions.Save(ts.sessionKey); err != nil {

pkg/agent/pipeline_llm.go

@@ -384,10 +384,7 @@ func (p *Pipeline) CallLLM(
 		}
 	}
 
-	reasoningContent := exec.response.Reasoning
-	if reasoningContent == "" {
-		reasoningContent = exec.response.ReasoningContent
-	}
+	reasoningContent := responseReasoningContent(exec.response)
 	if ts.channel == "pico" {
 		go al.publishPicoReasoning(turnCtx, reasoningContent, ts.chatID)
 	} else {
@@ -496,7 +493,7 @@ func (p *Pipeline) CallLLM(
 	assistantMsg := providers.Message{
 		Role:             "assistant",
 		Content:          exec.response.Content,
-		ReasoningContent: exec.response.ReasoningContent,
+		ReasoningContent: reasoningContent,
 	}
 	for _, tc := range exec.normalizedToolCalls {
 		argumentsJSON, _ := json.Marshal(tc.Arguments)

pkg/agent/subturn.go

@@ -10,6 +10,7 @@ import (
 
 	"github.com/sipeed/picoclaw/pkg/logger"
 	"github.com/sipeed/picoclaw/pkg/providers"
+	"github.com/sipeed/picoclaw/pkg/providers/messageutil"
 	"github.com/sipeed/picoclaw/pkg/tools"
 )
 
@@ -623,6 +624,10 @@ func (e *ephemeralSessionStore) AddMessage(_, role, content string) {
 }
 
 func (e *ephemeralSessionStore) AddFullMessage(_ string, msg providers.Message) {
+	if messageutil.IsTransientAssistantThoughtMessage(msg) {
+		return
+	}
+
 	e.mu.Lock()
 	defer e.mu.Unlock()
 	e.history = append(e.history, msg)
@@ -652,6 +657,7 @@ func (e *ephemeralSessionStore) SetSummary(_, summary string) {
 func (e *ephemeralSessionStore) SetHistory(_ string, history []providers.Message) {
 	e.mu.Lock()
 	defer e.mu.Unlock()
+	history = messageutil.FilterInvalidHistoryMessages(history)
 	e.history = make([]providers.Message, len(history))
 	copy(e.history, history)
 	e.truncateLocked()

pkg/memory/jsonl.go

@@ -16,6 +16,7 @@ import (
 
 	"github.com/sipeed/picoclaw/pkg/fileutil"
 	"github.com/sipeed/picoclaw/pkg/providers"
+	"github.com/sipeed/picoclaw/pkg/providers/messageutil"
 )
 
 const (
@@ -482,6 +483,9 @@ func readMessages(path string, skip int) ([]providers.Message, error) {
 				lineNum, filepath.Base(path), err)
 			continue
 		}
+		if messageutil.IsTransientAssistantThoughtMessage(msg) {
+			continue
+		}
 		msgs = append(msgs, msg)
 	}
 	if scanner.Err() != nil {
@@ -535,6 +539,10 @@ func (s *JSONLStore) AddFullMessage(
 
 // addMsg is the shared implementation for AddMessage and AddFullMessage.
 func (s *JSONLStore) addMsg(sessionKey string, msg providers.Message) error {
+	if messageutil.IsTransientAssistantThoughtMessage(msg) {
+		return nil
+	}
+
 	l := s.sessionLock(sessionKey)
 	l.Lock()
 	defer l.Unlock()
@@ -684,6 +692,8 @@ func (s *JSONLStore) SetHistory(
 	sessionKey string,
 	history []providers.Message,
 ) error {
+	history = messageutil.FilterInvalidHistoryMessages(history)
+
 	l := s.sessionLock(sessionKey)
 	l.Lock()
 	defer l.Unlock()
@@ -762,6 +772,8 @@ func (s *JSONLStore) Compact(
 func (s *JSONLStore) rewriteJSONL(
 	sessionKey string, msgs []providers.Message,
 ) error {
+	msgs = messageutil.FilterInvalidHistoryMessages(msgs)
+
 	var buf bytes.Buffer
 	for i, msg := range msgs {
 		line, err := json.Marshal(msg)

pkg/memory/jsonl_test.go

@@ -6,6 +6,7 @@ import (
 	"os"
 	"path/filepath"
 	"reflect"
+	"strings"
 	"sync"
 	"testing"
 
@@ -155,6 +156,27 @@ func TestAddFullMessage_ToolCallID(t *testing.T) {
 	}
 }
 
+func TestAddFullMessage_DropsTransientAssistantThought(t *testing.T) {
+	store := newTestStore(t)
+	ctx := context.Background()
+
+	err := store.AddFullMessage(ctx, "transient-thought", providers.Message{
+		Role:             "assistant",
+		ReasoningContent: "internal chain of thought",
+	})
+	if err != nil {
+		t.Fatalf("AddFullMessage: %v", err)
+	}
+
+	history, err := store.GetHistory(ctx, "transient-thought")
+	if err != nil {
+		t.Fatalf("GetHistory: %v", err)
+	}
+	if len(history) != 0 {
+		t.Fatalf("expected transient thought to be discarded, got %d messages", len(history))
+	}
+}
+
 func TestGetHistory_EmptySession(t *testing.T) {
 	store := newTestStore(t)
 	ctx := context.Background()
@@ -243,6 +265,46 @@ func TestSetSummary_GetSummary(t *testing.T) {
 	}
 }
 
+func TestSetHistory_DropsTransientAssistantThought(t *testing.T) {
+	store := newTestStore(t)
+	ctx := context.Background()
+
+	newHistory := []providers.Message{
+		{Role: "user", Content: "hello"},
+		{Role: "assistant", ReasoningContent: "internal chain of thought"},
+		{Role: "assistant", Content: "visible answer", ReasoningContent: "visible thought"},
+	}
+
+	err := store.SetHistory(ctx, "replace", newHistory)
+	if err != nil {
+		t.Fatalf("SetHistory: %v", err)
+	}
+
+	history, err := store.GetHistory(ctx, "replace")
+	if err != nil {
+		t.Fatalf("GetHistory: %v", err)
+	}
+	if len(history) != 2 {
+		t.Fatalf("expected transient thought to be removed, got %d messages", len(history))
+	}
+	if history[0].Role != "user" || history[0].Content != "hello" {
+		t.Fatalf("history[0] = %+v, want user/hello", history[0])
+	}
+	if history[1].Role != "assistant" || history[1].Content != "visible answer" ||
+		history[1].ReasoningContent != "visible thought" {
+		t.Fatalf("history[1] = %+v, want assistant visible answer with reasoning", history[1])
+	}
+
+	data, err := os.ReadFile(store.jsonlPath("replace"))
+	if err != nil {
+		t.Fatalf("ReadFile(jsonl): %v", err)
+	}
+	lines := strings.Split(strings.TrimSpace(string(data)), "\n")
+	if len(lines) != 2 {
+		t.Fatalf("jsonl line count = %d, want 2", len(lines))
+	}
+}
+
 func TestSessionMetaScopeAndAliasesPersist(t *testing.T) {
 	store := newTestStore(t)
 	ctx := context.Background()

pkg/providers/factory_provider.go

@@ -178,7 +178,7 @@ func CreateProviderFromConfig(cfg *config.ModelConfig) (LLMProvider, string, err
 		if apiBase == "" {
 			apiBase = getDefaultAPIBase(protocol)
 		}
-		return NewHTTPProviderWithMaxTokensFieldAndRequestTimeout(
+		provider := NewHTTPProviderWithMaxTokensFieldAndRequestTimeout(
 			cfg.APIKey(),
 			apiBase,
 			cfg.Proxy,
@@ -187,7 +187,9 @@ func CreateProviderFromConfig(cfg *config.ModelConfig) (LLMProvider, string, err
 			cfg.RequestTimeout,
 			cfg.ExtraBody,
 			cfg.CustomHeaders,
-		), modelID, nil
+		)
+		provider.SetProviderName(protocol)
+		return provider, modelID, nil
 
 	case "azure", "azure-openai":
 		// Azure OpenAI uses deployment-based URLs, api-key header auth,
@@ -257,7 +259,7 @@ func CreateProviderFromConfig(cfg *config.ModelConfig) (LLMProvider, string, err
 		if apiBase == "" {
 			apiBase = getDefaultAPIBase(protocol)
 		}
-		return NewHTTPProviderWithMaxTokensFieldAndRequestTimeout(
+		provider := NewHTTPProviderWithMaxTokensFieldAndRequestTimeout(
 			cfg.APIKey(),
 			apiBase,
 			cfg.Proxy,
@@ -266,7 +268,9 @@ func CreateProviderFromConfig(cfg *config.ModelConfig) (LLMProvider, string, err
 			cfg.RequestTimeout,
 			cfg.ExtraBody,
 			cfg.CustomHeaders,
-		), modelID, nil
+		)
+		provider.SetProviderName(protocol)
+		return provider, modelID, nil
 
 	case "gemini":
 		if cfg.APIKey() == "" && cfg.APIBase == "" {
@@ -302,7 +306,7 @@ func CreateProviderFromConfig(cfg *config.ModelConfig) (LLMProvider, string, err
 		if _, ok := extraBody["reasoning_split"]; !ok {
 			extraBody["reasoning_split"] = true
 		}
-		return NewHTTPProviderWithMaxTokensFieldAndRequestTimeout(
+		provider := NewHTTPProviderWithMaxTokensFieldAndRequestTimeout(
 			cfg.APIKey(),
 			apiBase,
 			cfg.Proxy,
@@ -311,7 +315,9 @@ func CreateProviderFromConfig(cfg *config.ModelConfig) (LLMProvider, string, err
 			cfg.RequestTimeout,
 			extraBody,
 			cfg.CustomHeaders,
-		), modelID, nil
+		)
+		provider.SetProviderName(protocol)
+		return provider, modelID, nil
 
 	case "anthropic":
 		if cfg.AuthMethod == "oauth" || cfg.AuthMethod == "token" {
@@ -330,7 +336,7 @@ func CreateProviderFromConfig(cfg *config.ModelConfig) (LLMProvider, string, err
 		if cfg.APIKey() == "" {
 			return nil, "", fmt.Errorf("api_key is required for anthropic protocol (model: %s)", cfg.Model)
 		}
-		return NewHTTPProviderWithMaxTokensFieldAndRequestTimeout(
+		provider := NewHTTPProviderWithMaxTokensFieldAndRequestTimeout(
 			cfg.APIKey(),
 			apiBase,
 			cfg.Proxy,
@@ -339,7 +345,9 @@ func CreateProviderFromConfig(cfg *config.ModelConfig) (LLMProvider, string, err
 			cfg.RequestTimeout,
 			cfg.ExtraBody,
 			cfg.CustomHeaders,
-		), modelID, nil
+		)
+		provider.SetProviderName(protocol)
+		return provider, modelID, nil
 
 	case "anthropic-messages":
 		// Anthropic Messages API with native format (HTTP-based, no SDK)

pkg/providers/httpapi/http_provider.go

@@ -77,3 +77,10 @@ func (p *HTTPProvider) GetDefaultModel() string {
 func (p *HTTPProvider) SupportsNativeSearch() bool {
 	return p.delegate.SupportsNativeSearch()
 }
+
+func (p *HTTPProvider) SetProviderName(providerName string) {
+	if p == nil || p.delegate == nil {
+		return
+	}
+	p.delegate.SetProviderName(providerName)
+}

pkg/providers/messageutil/messageutil.go

@@ -0,0 +1,41 @@
+package messageutil
+
+import (
+	"strings"
+
+	"github.com/sipeed/picoclaw/pkg/providers/protocoltypes"
+)
+
+// IsTransientAssistantThoughtMessage reports whether msg is an invalid
+// reasoning-only assistant history record. These "hanging" thought messages
+// are not a canonical persisted format and should be discarded instead of
+// replayed or reconstructed.
+func IsTransientAssistantThoughtMessage(msg protocoltypes.Message) bool {
+	return msg.Role == "assistant" &&
+		strings.TrimSpace(msg.Content) == "" &&
+		strings.TrimSpace(msg.ReasoningContent) != "" &&
+		len(msg.ToolCalls) == 0 &&
+		len(msg.Media) == 0 &&
+		len(msg.Attachments) == 0 &&
+		strings.TrimSpace(msg.ToolCallID) == ""
+}
+
+// FilterInvalidHistoryMessages removes invalid persisted history records such
+// as transient assistant thought-only messages.
+func FilterInvalidHistoryMessages(history []protocoltypes.Message) []protocoltypes.Message {
+	if len(history) == 0 {
+		return []protocoltypes.Message{}
+	}
+
+	filtered := make([]protocoltypes.Message, 0, len(history))
+	for _, msg := range history {
+		if IsTransientAssistantThoughtMessage(msg) {
+			continue
+		}
+		filtered = append(filtered, msg)
+	}
+	if filtered == nil {
+		return []protocoltypes.Message{}
+	}
+	return filtered
+}

pkg/providers/openai_compat/provider.go

@@ -15,6 +15,7 @@ import (
 	"time"
 
 	"github.com/sipeed/picoclaw/pkg/providers/common"
+	"github.com/sipeed/picoclaw/pkg/providers/messageutil"
 	"github.com/sipeed/picoclaw/pkg/providers/protocoltypes"
 )
 
@@ -34,6 +35,7 @@ type (
 type Provider struct {
 	apiKey         string
 	apiBase        string
+	providerName   string
 	maxTokensField string // Field name for max tokens (e.g., "max_completion_tokens" for o1/glm models)
 	httpClient     *http.Client
 	extraBody      map[string]any // Additional fields to inject into request body
@@ -95,6 +97,12 @@ func WithCustomHeaders(customHeaders map[string]string) Option {
 	}
 }
 
+func WithProviderName(providerName string) Option {
+	return func(p *Provider) {
+		p.providerName = strings.ToLower(strings.TrimSpace(providerName))
+	}
+}
+
 func NewProvider(apiKey, apiBase, proxy string, opts ...Option) *Provider {
 	p := &Provider{
 		apiKey:     apiKey,
@@ -136,7 +144,7 @@ func (p *Provider) buildRequestBody(
 
 	requestBody := map[string]any{
 		"model":    model,
-		"messages": common.SerializeMessages(messages),
+		"messages": common.SerializeMessages(p.prepareMessagesForRequest(messages)),
 	}
 
 	// When fallback uses a different provider (e.g. DeepSeek), that provider must not inject web_search_preview.
@@ -196,6 +204,111 @@ func (p *Provider) applyCustomHeaders(req *http.Request) {
 	}
 }
 
+func (p *Provider) SetProviderName(providerName string) {
+	p.providerName = strings.ToLower(strings.TrimSpace(providerName))
+}
+
+func (p *Provider) prepareMessagesForRequest(messages []Message) []Message {
+	if len(messages) == 0 {
+		return nil
+	}
+
+	if p.isDeepSeekReasoningProvider() {
+		return filterDeepSeekReasoningMessages(messages)
+	}
+	return stripReasoningMessages(messages)
+}
+
+func (p *Provider) isDeepSeekReasoningProvider() bool {
+	return p.providerName == "deepseek" || isDeepSeekHost(p.apiBase)
+}
+
+func isDeepSeekHost(apiBase string) bool {
+	parsed, err := url.Parse(strings.TrimSpace(apiBase))
+	if err != nil {
+		return false
+	}
+	host := strings.ToLower(strings.TrimSpace(parsed.Hostname()))
+	return host == "deepseek.com" || strings.HasSuffix(host, ".deepseek.com")
+}
+
+func filterDeepSeekReasoningMessages(messages []Message) []Message {
+	out := make([]Message, 0, len(messages))
+	start := 0
+
+	flush := func(end int) {
+		if end <= start {
+			return
+		}
+		out = append(out, filterDeepSeekReasoningTurn(messages[start:end])...)
+		start = end
+	}
+
+	for i := 1; i < len(messages); i++ {
+		if messages[i].Role == "user" {
+			flush(i)
+		}
+	}
+	flush(len(messages))
+
+	return out
+}
+
+func filterDeepSeekReasoningTurn(messages []Message) []Message {
+	hasToolInteraction := false
+	for _, msg := range messages {
+		if msg.Role == "tool" || (msg.Role == "assistant" && len(msg.ToolCalls) > 0) {
+			hasToolInteraction = true
+			break
+		}
+	}
+
+	out := make([]Message, 0, len(messages))
+	for _, msg := range messages {
+		if messageutil.IsTransientAssistantThoughtMessage(msg) {
+			continue
+		}
+
+		cloned := msg
+		if cloned.Role == "assistant" && strings.TrimSpace(cloned.ReasoningContent) != "" && !hasToolInteraction {
+			cloned.ReasoningContent = ""
+		}
+		if assistantMessageEmpty(cloned) {
+			continue
+		}
+		out = append(out, cloned)
+	}
+
+	return out
+}
+
+func stripReasoningMessages(messages []Message) []Message {
+	out := make([]Message, 0, len(messages))
+	for _, msg := range messages {
+		if messageutil.IsTransientAssistantThoughtMessage(msg) {
+			continue
+		}
+
+		cloned := msg
+		cloned.ReasoningContent = ""
+		if assistantMessageEmpty(cloned) {
+			continue
+		}
+		out = append(out, cloned)
+	}
+	return out
+}
+
+func assistantMessageEmpty(msg Message) bool {
+	return msg.Role == "assistant" &&
+		strings.TrimSpace(msg.Content) == "" &&
+		strings.TrimSpace(msg.ReasoningContent) == "" &&
+		len(msg.ToolCalls) == 0 &&
+		len(msg.Media) == 0 &&
+		len(msg.Attachments) == 0 &&
+		strings.TrimSpace(msg.ToolCallID) == ""
+}
+
 func (p *Provider) Chat(
 	ctx context.Context,
 	messages []Message,

pkg/providers/openai_compat/provider_test.go

@@ -202,7 +202,7 @@ func TestProviderChat_ParsesReasoningContent(t *testing.T) {
 	}
 }
 
-func TestProviderChat_PreservesReasoningContentInHistory(t *testing.T) {
+func TestProviderChat_StripsReasoningContentForNonDeepSeekHistory(t *testing.T) {
 	var requestBody map[string]any
 
 	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
@@ -225,8 +225,6 @@ func TestProviderChat_PreservesReasoningContentInHistory(t *testing.T) {
 
 	p := NewProvider("key", server.URL, "")
 
-	// Simulate a multi-turn conversation where the assistant's previous
-	// reply included reasoning_content (e.g. from kimi-k2.5).
 	messages := []Message{
 		{Role: "user", Content: "What is 1+1?"},
 		{Role: "assistant", Content: "2", ReasoningContent: "Let me think... 1+1=2"},
@@ -238,7 +236,6 @@ func TestProviderChat_PreservesReasoningContentInHistory(t *testing.T) {
 		t.Fatalf("Chat() error = %v", err)
 	}
 
-	// Verify reasoning_content is preserved in the serialized request.
 	reqMessages, ok := requestBody["messages"].([]any)
 	if !ok {
 		t.Fatalf("messages is not []any: %T", requestBody["messages"])
@@ -247,11 +244,288 @@ func TestProviderChat_PreservesReasoningContentInHistory(t *testing.T) {
 	if !ok {
 		t.Fatalf("assistant message is not map[string]any: %T", reqMessages[1])
 	}
-	if assistantMsg["reasoning_content"] != "Let me think... 1+1=2" {
-		t.Errorf("reasoning_content not preserved in request, got %v", assistantMsg["reasoning_content"])
+	if _, exists := assistantMsg["reasoning_content"]; exists {
+		t.Fatalf(
+			"reasoning_content should be stripped for non-DeepSeek providers, got %v",
+			assistantMsg["reasoning_content"],
+		)
 	}
 }
 
+func TestProviderChat_DeepSeekOmitsReasoningContentForNonToolTurnHistory(t *testing.T) {
+	var requestBody map[string]any
+
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		if err := json.NewDecoder(r.Body).Decode(&requestBody); err != nil {
+			http.Error(w, err.Error(), http.StatusBadRequest)
+			return
+		}
+		resp := map[string]any{
+			"choices": []map[string]any{
+				{
+					"message":       map[string]any{"content": "ok"},
+					"finish_reason": "stop",
+				},
+			},
+		}
+		w.Header().Set("Content-Type", "application/json")
+		json.NewEncoder(w).Encode(resp)
+	}))
+	defer server.Close()
+
+	p := NewProvider("key", server.URL, "")
+	p.apiBase = "https://api.deepseek.com/v1"
+	p.httpClient = &http.Client{
+		Transport: roundTripperFunc(func(r *http.Request) (*http.Response, error) {
+			r.URL, _ = url.Parse(server.URL + r.URL.Path)
+			return http.DefaultTransport.RoundTrip(r)
+		}),
+	}
+
+	messages := []Message{
+		{Role: "user", Content: "What is 1+1?"},
+		{Role: "assistant", Content: "2", ReasoningContent: "Let me think... 1+1=2"},
+		{Role: "user", Content: "What about 2+2?"},
+	}
+
+	_, err := p.Chat(t.Context(), messages, nil, "deepseek-v4-flash", nil)
+	if err != nil {
+		t.Fatalf("Chat() error = %v", err)
+	}
+
+	reqMessages, ok := requestBody["messages"].([]any)
+	if !ok {
+		t.Fatalf("messages is not []any: %T", requestBody["messages"])
+	}
+	assistantMsg, ok := reqMessages[1].(map[string]any)
+	if !ok {
+		t.Fatalf("assistant message is not map[string]any: %T", reqMessages[1])
+	}
+	if _, exists := assistantMsg["reasoning_content"]; exists {
+		t.Fatalf(
+			"reasoning_content should be omitted for DeepSeek non-tool turns, got %v",
+			assistantMsg["reasoning_content"],
+		)
+	}
+}
+
+func TestProviderChat_DeepSeekPreservesReasoningContentForToolTurnHistory(t *testing.T) {
+	var requestBody map[string]any
+
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		if err := json.NewDecoder(r.Body).Decode(&requestBody); err != nil {
+			http.Error(w, err.Error(), http.StatusBadRequest)
+			return
+		}
+		resp := map[string]any{
+			"choices": []map[string]any{
+				{
+					"message":       map[string]any{"content": "ok"},
+					"finish_reason": "stop",
+				},
+			},
+		}
+		w.Header().Set("Content-Type", "application/json")
+		json.NewEncoder(w).Encode(resp)
+	}))
+	defer server.Close()
+
+	p := NewProvider("key", server.URL, "")
+	p.SetProviderName("deepseek")
+
+	messages := []Message{
+		{Role: "user", Content: "How's the weather tomorrow?"},
+		{
+			Role:             "assistant",
+			Content:          "Let me check the date first.",
+			ReasoningContent: "I need tomorrow's date before checking the weather.",
+			ToolCalls: []ToolCall{{
+				ID:   "call_1",
+				Type: "function",
+				Function: &FunctionCall{
+					Name:      "get_date",
+					Arguments: "{}",
+				},
+			}},
+		},
+		{Role: "tool", ToolCallID: "call_1", Content: "2026-04-24"},
+		{
+			Role:             "assistant",
+			Content:          "Tomorrow is 2026-04-25.",
+			ReasoningContent: "Now I can share the final answer.",
+		},
+		{Role: "user", Content: "What about Guangzhou?"},
+	}
+
+	_, err := p.Chat(t.Context(), messages, nil, "deepseek-v4-flash", nil)
+	if err != nil {
+		t.Fatalf("Chat() error = %v", err)
+	}
+
+	reqMessages, ok := requestBody["messages"].([]any)
+	if !ok {
+		t.Fatalf("messages is not []any: %T", requestBody["messages"])
+	}
+	if len(reqMessages) != len(messages) {
+		t.Fatalf("len(messages) = %d, want %d", len(reqMessages), len(messages))
+	}
+
+	firstAssistant, ok := reqMessages[1].(map[string]any)
+	if !ok {
+		t.Fatalf("first assistant message is not map[string]any: %T", reqMessages[1])
+	}
+	if firstAssistant["reasoning_content"] != "I need tomorrow's date before checking the weather." {
+		t.Fatalf("first assistant reasoning_content = %v, want preserved", firstAssistant["reasoning_content"])
+	}
+
+	finalAssistant, ok := reqMessages[3].(map[string]any)
+	if !ok {
+		t.Fatalf("final assistant message is not map[string]any: %T", reqMessages[3])
+	}
+	if finalAssistant["reasoning_content"] != "Now I can share the final answer." {
+		t.Fatalf("final assistant reasoning_content = %v, want preserved", finalAssistant["reasoning_content"])
+	}
+}
+
+func TestProviderChat_HistoryCanonicalizationMatrix(t *testing.T) {
+	baseMessages := []Message{
+		{Role: "user", Content: "turn1"},
+		{Role: "assistant", Content: "plain visible", ReasoningContent: "plain thought"},
+		{Role: "user", Content: "turn2"},
+		{
+			Role:             "assistant",
+			Content:          "",
+			ReasoningContent: "tool thought",
+			ToolCalls: []ToolCall{{
+				ID:   "call_read_file",
+				Type: "function",
+				Function: &FunctionCall{
+					Name:      "read_file",
+					Arguments: `{"path":"README.md"}`,
+				},
+			}},
+		},
+		{Role: "tool", ToolCallID: "call_read_file", Content: "file content"},
+		{Role: "user", Content: "turn3"},
+		{
+			Role:    "assistant",
+			Content: "tool visible only",
+			ToolCalls: []ToolCall{{
+				ID:   "call_list_dir",
+				Type: "function",
+				Function: &FunctionCall{
+					Name:      "list_dir",
+					Arguments: `{"path":"."}`,
+				},
+			}},
+		},
+		{Role: "tool", ToolCallID: "call_list_dir", Content: "dir listing"},
+		{Role: "user", Content: "turn4"},
+		{
+			Role:             "assistant",
+			Content:          "tool visible and thought",
+			ReasoningContent: "tool mixed thought",
+			ToolCalls: []ToolCall{{
+				ID:   "call_exec",
+				Type: "function",
+				Function: &FunctionCall{
+					Name:      "exec",
+					Arguments: `{"command":"pwd"}`,
+				},
+			}},
+		},
+		{Role: "tool", ToolCallID: "call_exec", Content: "pwd output"},
+		{Role: "user", Content: "current turn"},
+	}
+
+	captureRequestMessages := func(t *testing.T, providerName string) []map[string]any {
+		t.Helper()
+
+		var requestBody map[string]any
+		server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+			if err := json.NewDecoder(r.Body).Decode(&requestBody); err != nil {
+				http.Error(w, err.Error(), http.StatusBadRequest)
+				return
+			}
+			resp := map[string]any{
+				"choices": []map[string]any{
+					{
+						"message":       map[string]any{"content": "ok"},
+						"finish_reason": "stop",
+					},
+				},
+			}
+			w.Header().Set("Content-Type", "application/json")
+			json.NewEncoder(w).Encode(resp)
+		}))
+		defer server.Close()
+
+		p := NewProvider("key", server.URL, "")
+		if providerName != "" {
+			p.SetProviderName(providerName)
+		}
+
+		_, err := p.Chat(t.Context(), baseMessages, nil, "test-model", nil)
+		if err != nil {
+			t.Fatalf("Chat() error = %v", err)
+		}
+
+		rawMessages, ok := requestBody["messages"].([]any)
+		if !ok {
+			t.Fatalf("messages is not []any: %T", requestBody["messages"])
+		}
+
+		out := make([]map[string]any, 0, len(rawMessages))
+		for i, raw := range rawMessages {
+			msg, ok := raw.(map[string]any)
+			if !ok {
+				t.Fatalf("messages[%d] is %T, want map[string]any", i, raw)
+			}
+			out = append(out, msg)
+		}
+		return out
+	}
+
+	t.Run("deepseek", func(t *testing.T) {
+		msgs := captureRequestMessages(t, "deepseek")
+		if len(msgs) != len(baseMessages) {
+			t.Fatalf("len(messages) = %d, want %d", len(msgs), len(baseMessages))
+		}
+
+		if _, ok := msgs[1]["reasoning_content"]; ok {
+			t.Fatalf(
+				"turn1 reasoning_content should be stripped for DeepSeek non-tool turn, got %v",
+				msgs[1]["reasoning_content"],
+			)
+		}
+		if msgs[3]["reasoning_content"] != "tool thought" {
+			t.Fatalf("turn2 reasoning_content = %v, want preserved", msgs[3]["reasoning_content"])
+		}
+		if _, ok := msgs[6]["reasoning_content"]; ok {
+			t.Fatalf("turn3 reasoning_content should be absent, got %v", msgs[6]["reasoning_content"])
+		}
+		if msgs[9]["reasoning_content"] != "tool mixed thought" {
+			t.Fatalf("turn4 reasoning_content = %v, want preserved", msgs[9]["reasoning_content"])
+		}
+		if msgs[9]["content"] != "tool visible and thought" {
+			t.Fatalf("turn4 content = %v, want preserved", msgs[9]["content"])
+		}
+	})
+
+	t.Run("non-deepseek", func(t *testing.T) {
+		msgs := captureRequestMessages(t, "")
+		for i, msg := range msgs {
+			if _, ok := msg["reasoning_content"]; ok {
+				t.Fatalf(
+					"messages[%d] reasoning_content should be stripped for non-DeepSeek providers, got %v",
+					i,
+					msg["reasoning_content"],
+				)
+			}
+		}
+	})
+}
+
 func TestProviderChat_HTTPError(t *testing.T) {
 	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		http.Error(w, "bad request", http.StatusBadRequest)

pkg/session/manager.go

@@ -9,6 +9,7 @@ import (
 	"time"
 
 	"github.com/sipeed/picoclaw/pkg/providers"
+	"github.com/sipeed/picoclaw/pkg/providers/messageutil"
 )
 
 type Session struct {
@@ -69,6 +70,10 @@ func (sm *SessionManager) AddMessage(sessionKey, role, content string) {
 // AddFullMessage adds a complete message with tool calls and tool call ID to the session.
 // This is used to save the full conversation flow including tool calls and tool results.
 func (sm *SessionManager) AddFullMessage(sessionKey string, msg providers.Message) {
+	if messageutil.IsTransientAssistantThoughtMessage(msg) {
+		return
+	}
+
 	sm.mu.Lock()
 	defer sm.mu.Unlock()
 
@@ -196,8 +201,7 @@ func (sm *SessionManager) Save(key string) error {
 		Updated: stored.Updated,
 	}
 	if len(stored.Messages) > 0 {
-		snapshot.Messages = make([]providers.Message, len(stored.Messages))
-		copy(snapshot.Messages, stored.Messages)
+		snapshot.Messages = messageutil.FilterInvalidHistoryMessages(stored.Messages)
 	} else {
 		snapshot.Messages = []providers.Message{}
 	}
@@ -270,6 +274,7 @@ func (sm *SessionManager) loadSessions() error {
 		if err := json.Unmarshal(data, &session); err != nil {
 			continue
 		}
+		session.Messages = messageutil.FilterInvalidHistoryMessages(session.Messages)
 
 		sm.sessions[session.Key] = &session
 	}
@@ -290,6 +295,7 @@ func (sm *SessionManager) SetHistory(key string, history []providers.Message) {
 
 	session, ok := sm.sessions[key]
 	if ok {
+		history = messageutil.FilterInvalidHistoryMessages(history)
 		// Create a deep copy to strictly isolate internal state
 		// from the caller's slice.
 		msgs := make([]providers.Message, len(history))

web/backend/api/session.go

@@ -15,6 +15,7 @@ import (
 	"github.com/sipeed/picoclaw/pkg/config"
 	"github.com/sipeed/picoclaw/pkg/memory"
 	"github.com/sipeed/picoclaw/pkg/providers"
+	"github.com/sipeed/picoclaw/pkg/providers/messageutil"
 	"github.com/sipeed/picoclaw/pkg/session"
 	"github.com/sipeed/picoclaw/pkg/utils"
 )
@@ -48,6 +49,7 @@ type sessionListItem struct {
 type sessionChatMessage struct {
 	Role        string                  `json:"role"`
 	Content     string                  `json:"content"`
+	Kind        string                  `json:"kind,omitempty"`
 	Media       []string                `json:"media,omitempty"`
 	Attachments []sessionChatAttachment `json:"attachments,omitempty"`
 }
@@ -473,6 +475,18 @@ func sessionChatMessagePreview(msg sessionChatMessage) string {
 }
 
 func visibleSessionMessages(messages []providers.Message, toolFeedbackMaxArgsLength int) []sessionChatMessage {
+	return sessionTranscriptMessages(messages, toolFeedbackMaxArgsLength, false)
+}
+
+func detailSessionMessages(messages []providers.Message, toolFeedbackMaxArgsLength int) []sessionChatMessage {
+	return sessionTranscriptMessages(messages, toolFeedbackMaxArgsLength, true)
+}
+
+func sessionTranscriptMessages(
+	messages []providers.Message,
+	toolFeedbackMaxArgsLength int,
+	includeThoughts bool,
+) []sessionChatMessage {
 	transcript := make([]sessionChatMessage, 0, len(messages))
 
 	for _, msg := range messages {
@@ -494,11 +508,14 @@ func visibleSessionMessages(messages []providers.Message, toolFeedbackMaxArgsLen
 			}
 
 		case "assistant":
-			// Reasoning-only assistant messages are transient display artifacts and
-			// should not be restored from session history.
-			if assistantMessageTransientThought(msg) {
+			if messageutil.IsTransientAssistantThoughtMessage(msg) {
 				continue
 			}
+			if includeThoughts {
+				if thoughtMsg, ok := assistantThoughtMessage(msg); ok {
+					transcript = append(transcript, thoughtMsg)
+				}
+			}
 
 			toolSummaryMessages := visibleAssistantToolSummaryMessages(msg.ToolCalls, toolFeedbackMaxArgsLength)
 			if len(toolSummaryMessages) > 0 {
@@ -672,18 +689,25 @@ func sessionAttachmentType(attachment providers.Attachment) string {
 	}
 }
 
-func assistantMessageTransientThought(msg providers.Message) bool {
-	return strings.TrimSpace(msg.Content) == "" &&
-		strings.TrimSpace(msg.ReasoningContent) != "" &&
-		len(msg.ToolCalls) == 0 &&
-		len(msg.Media) == 0 &&
-		len(msg.Attachments) == 0
-}
-
 func assistantMessageInternalOnly(msg providers.Message) bool {
 	return strings.TrimSpace(msg.Content) == handledToolResponseSummaryText
 }
 
+func assistantThoughtMessage(msg providers.Message) (sessionChatMessage, bool) {
+	reasoning := strings.TrimSpace(msg.ReasoningContent)
+	if reasoning == "" {
+		return sessionChatMessage{}, false
+	}
+	if reasoning == strings.TrimSpace(msg.Content) {
+		return sessionChatMessage{}, false
+	}
+	return sessionChatMessage{
+		Role:    "assistant",
+		Content: reasoning,
+		Kind:    "thought",
+	}, true
+}
+
 func visibleAssistantToolSummaryMessages(
 	toolCalls []providers.ToolCall,
 	toolFeedbackMaxArgsLength int,
@@ -962,7 +986,7 @@ func (h *Handler) handleGetSession(w http.ResponseWriter, r *http.Request) {
 		}
 	}
 
-	messages := visibleSessionMessages(sess.Messages, toolFeedbackMaxArgsLength)
+	messages := detailSessionMessages(sess.Messages, toolFeedbackMaxArgsLength)
 
 	w.Header().Set("Content-Type", "application/json")
 	json.NewEncoder(w).Encode(map[string]any{

web/backend/api/session_test.go

@@ -423,7 +423,7 @@ func TestHandleSessions_JSONLScopeDiscovery(t *testing.T) {
 	}
 }
 
-func TestHandleGetSession_OmitsTransientThoughtMessages(t *testing.T) {
+func TestHandleGetSession_SkipsTransientThoughtMessages(t *testing.T) {
 	configPath, cleanup := setupOAuthTestEnv(t)
 	defer cleanup()
 
@@ -460,6 +460,7 @@ func TestHandleGetSession_OmitsTransientThoughtMessages(t *testing.T) {
 		Messages []struct {
 			Role    string `json:"role"`
 			Content string `json:"content"`
+			Kind    string `json:"kind"`
 		} `json:"messages"`
 	}
 	if err := json.Unmarshal(rec.Body.Bytes(), &resp); err != nil {
@@ -476,6 +477,180 @@ func TestHandleGetSession_OmitsTransientThoughtMessages(t *testing.T) {
 	}
 }
 
+func TestHandleGetSession_ReconstructsThoughtFromAssistantReasoningContent(t *testing.T) {
+	configPath, cleanup := setupOAuthTestEnv(t)
+	defer cleanup()
+
+	dir := sessionsTestDir(t, configPath)
+	store, err := memory.NewJSONLStore(dir)
+	if err != nil {
+		t.Fatalf("NewJSONLStore() error = %v", err)
+	}
+
+	sessionKey := picoSessionPrefix + "detail-reasoning-content"
+	for _, msg := range []providers.Message{
+		{Role: "user", Content: "hello"},
+		{Role: "assistant", Content: "final visible answer", ReasoningContent: "internal chain of thought"},
+	} {
+		if err := store.AddFullMessage(nil, sessionKey, msg); err != nil {
+			t.Fatalf("AddFullMessage() error = %v", err)
+		}
+	}
+
+	h := NewHandler(configPath)
+	mux := http.NewServeMux()
+	h.RegisterRoutes(mux)
+
+	rec := httptest.NewRecorder()
+	req := httptest.NewRequest(http.MethodGet, "/api/sessions/detail-reasoning-content", nil)
+	mux.ServeHTTP(rec, req)
+
+	if rec.Code != http.StatusOK {
+		t.Fatalf("status = %d, want %d, body=%s", rec.Code, http.StatusOK, rec.Body.String())
+	}
+
+	var resp struct {
+		Messages []struct {
+			Role    string `json:"role"`
+			Content string `json:"content"`
+			Kind    string `json:"kind"`
+		} `json:"messages"`
+	}
+	if err := json.Unmarshal(rec.Body.Bytes(), &resp); err != nil {
+		t.Fatalf("Unmarshal() error = %v", err)
+	}
+	if len(resp.Messages) != 3 {
+		t.Fatalf("len(resp.Messages) = %d, want 3", len(resp.Messages))
+	}
+	if resp.Messages[1].Role != "assistant" ||
+		resp.Messages[1].Content != "internal chain of thought" ||
+		resp.Messages[1].Kind != "thought" {
+		t.Fatalf("thought message = %#v, want assistant thought/internal chain of thought", resp.Messages[1])
+	}
+	if resp.Messages[2].Role != "assistant" || resp.Messages[2].Content != "final visible answer" {
+		t.Fatalf("final message = %#v, want assistant/final visible answer", resp.Messages[2])
+	}
+}
+
+func TestHandleGetSession_ReconstructsRefreshMatrixForThoughtAndToolSummary(t *testing.T) {
+	configPath, cleanup := setupOAuthTestEnv(t)
+	defer cleanup()
+
+	dir := sessionsTestDir(t, configPath)
+	store, err := memory.NewJSONLStore(dir)
+	if err != nil {
+		t.Fatalf("NewJSONLStore() error = %v", err)
+	}
+
+	sessionKey := picoSessionPrefix + "detail-refresh-matrix"
+	for _, msg := range []providers.Message{
+		{Role: "user", Content: "turn1"},
+		{Role: "assistant", Content: "plain visible", ReasoningContent: "plain thought"},
+		{Role: "user", Content: "turn2"},
+		{
+			Role:             "assistant",
+			ReasoningContent: "tool thought",
+			ToolCalls: []providers.ToolCall{{
+				ID:   "call_read_file",
+				Type: "function",
+				Function: &providers.FunctionCall{
+					Name:      "read_file",
+					Arguments: `{"path":"README.md"}`,
+				},
+			}},
+		},
+		{Role: "tool", ToolCallID: "call_read_file", Content: "file result"},
+		{Role: "user", Content: "turn3"},
+		{
+			Role:    "assistant",
+			Content: "tool visible only",
+			ToolCalls: []providers.ToolCall{{
+				ID:   "call_list_dir",
+				Type: "function",
+				Function: &providers.FunctionCall{
+					Name:      "list_dir",
+					Arguments: `{"path":"."}`,
+				},
+			}},
+		},
+		{Role: "tool", ToolCallID: "call_list_dir", Content: "dir result"},
+		{Role: "user", Content: "turn4"},
+		{
+			Role:             "assistant",
+			Content:          "tool visible and thought",
+			ReasoningContent: "tool mixed thought",
+			ToolCalls: []providers.ToolCall{{
+				ID:   "call_exec",
+				Type: "function",
+				Function: &providers.FunctionCall{
+					Name:      "exec",
+					Arguments: `{"command":"pwd"}`,
+				},
+			}},
+		},
+		{Role: "tool", ToolCallID: "call_exec", Content: "pwd result"},
+	} {
+		if err := store.AddFullMessage(nil, sessionKey, msg); err != nil {
+			t.Fatalf("AddFullMessage() error = %v", err)
+		}
+	}
+
+	h := NewHandler(configPath)
+	mux := http.NewServeMux()
+	h.RegisterRoutes(mux)
+
+	rec := httptest.NewRecorder()
+	req := httptest.NewRequest(http.MethodGet, "/api/sessions/detail-refresh-matrix", nil)
+	mux.ServeHTTP(rec, req)
+
+	if rec.Code != http.StatusOK {
+		t.Fatalf("status = %d, want %d, body=%s", rec.Code, http.StatusOK, rec.Body.String())
+	}
+
+	var resp struct {
+		Messages []struct {
+			Role    string `json:"role"`
+			Content string `json:"content"`
+			Kind    string `json:"kind"`
+		} `json:"messages"`
+	}
+	if err := json.Unmarshal(rec.Body.Bytes(), &resp); err != nil {
+		t.Fatalf("Unmarshal() error = %v", err)
+	}
+
+	if len(resp.Messages) != 13 {
+		t.Fatalf("len(resp.Messages) = %d, want 13", len(resp.Messages))
+	}
+
+	assertMessage := func(index int, role, kind, content string) {
+		t.Helper()
+		msg := resp.Messages[index]
+		if msg.Role != role || msg.Kind != kind || msg.Content != content {
+			t.Fatalf("messages[%d] = %#v, want role=%q kind=%q content=%q", index, msg, role, kind, content)
+		}
+	}
+
+	assertMessage(0, "user", "", "turn1")
+	assertMessage(1, "assistant", "thought", "plain thought")
+	assertMessage(2, "assistant", "", "plain visible")
+	assertMessage(3, "user", "", "turn2")
+	assertMessage(4, "assistant", "thought", "tool thought")
+	if !strings.Contains(resp.Messages[5].Content, "`read_file`") {
+		t.Fatalf("messages[5] = %#v, want read_file tool summary", resp.Messages[5])
+	}
+	assertMessage(6, "user", "", "turn3")
+	if !strings.Contains(resp.Messages[7].Content, "`list_dir`") {
+		t.Fatalf("messages[7] = %#v, want list_dir tool summary", resp.Messages[7])
+	}
+	assertMessage(8, "assistant", "", "tool visible only")
+	assertMessage(9, "user", "", "turn4")
+	assertMessage(10, "assistant", "thought", "tool mixed thought")
+	if !strings.Contains(resp.Messages[11].Content, "`exec`") {
+		t.Fatalf("messages[11] = %#v, want exec tool summary", resp.Messages[11])
+	}
+	assertMessage(12, "assistant", "", "tool visible and thought")
+}
+
 func TestHandleGetSession_ReconstructsVisibleMessageToolOutputWithoutDuplicateSummary(t *testing.T) {
 	configPath, cleanup := setupOAuthTestEnv(t)
 	defer cleanup()

web/frontend/src/api/sessions.ts

@@ -14,6 +14,7 @@ export interface SessionDetail {
   messages: {
     role: "user" | "assistant"
     content: string
+    kind?: "normal" | "thought"
     media?: string[]
     attachments?: {
       type?: "image" | "audio" | "video" | "file"

web/frontend/src/features/chat/history.ts

@@ -45,7 +45,8 @@ export async function loadSessionMessages(
     id: `hist-${index}-${Date.now()}`,
     role: message.role,
     content: message.content,
-    kind: message.role === "assistant" ? "normal" : undefined,
+    kind:
+      message.role === "assistant" ? (message.kind ?? "normal") : undefined,
     attachments: toChatAttachments({
       media: message.media,
       attachments: message.attachments,