gpt-oss integration

includes harmony parser and thinking levels, etc.

api/types.go

@@ -85,10 +85,11 @@ type GenerateRequest struct {
 	Options map[string]any `json:"options"`
 
 	// Think controls whether thinking/reasoning models will think before
-	// responding. Needs to be a pointer so we can distinguish between false
+	// responding. Can be a boolean (true/false) or a string ("high", "medium", "low")
+	// for supported models. Needs to be a pointer so we can distinguish between false
 	// (request that thinking _not_ be used) and unset (use the old behavior
 	// before this option was introduced)
-	Think *bool `json:"think,omitempty"`
+	Think *ThinkValue `json:"think,omitempty"`
 }
 
 // ChatRequest describes a request sent by [Client.Chat].
@@ -116,8 +117,9 @@ type ChatRequest struct {
 	Options map[string]any `json:"options"`
 
 	// Think controls whether thinking/reasoning models will think before
-	// responding
-	Think *bool `json:"think,omitempty"`
+	// responding. Can be a boolean (true/false) or a string ("high", "medium", "low")
+	// for supported models.
+	Think *ThinkValue `json:"think,omitempty"`
 }
 
 type Tools []Tool
@@ -508,6 +510,8 @@ type GenerateResponse struct {
 	Context []int `json:"context,omitempty"`
 
 	Metrics
+
+	ToolCalls []ToolCall `json:"tool_calls,omitempty"`
 }
 
 // ModelDetails provides details about a model.
@@ -677,6 +681,113 @@ func DefaultOptions() Options {
 	}
 }
 
+// ThinkValue represents a value that can be a boolean or a string ("high", "medium", "low")
+type ThinkValue struct {
+	// Value can be a bool or string
+	Value interface{}
+}
+
+// IsValid checks if the ThinkValue is valid
+func (t *ThinkValue) IsValid() bool {
+	if t == nil || t.Value == nil {
+		return true // nil is valid (means not set)
+	}
+
+	switch v := t.Value.(type) {
+	case bool:
+		return true
+	case string:
+		return v == "high" || v == "medium" || v == "low"
+	default:
+		return false
+	}
+}
+
+// IsBool returns true if the value is a boolean
+func (t *ThinkValue) IsBool() bool {
+	if t == nil || t.Value == nil {
+		return false
+	}
+	_, ok := t.Value.(bool)
+	return ok
+}
+
+// IsString returns true if the value is a string
+func (t *ThinkValue) IsString() bool {
+	if t == nil || t.Value == nil {
+		return false
+	}
+	_, ok := t.Value.(string)
+	return ok
+}
+
+// AsBool returns the value as a bool (true if enabled in any way)
+func (t *ThinkValue) AsBool() bool {
+	if t == nil || t.Value == nil {
+		return false
+	}
+
+	switch v := t.Value.(type) {
+	case bool:
+		return v
+	case string:
+		// Any string value ("high", "medium", "low") means thinking is enabled
+		return v == "high" || v == "medium" || v == "low"
+	default:
+		return false
+	}
+}
+
+// AsString returns the value as a string
+func (t *ThinkValue) AsString() string {
+	if t == nil || t.Value == nil {
+		return ""
+	}
+
+	switch v := t.Value.(type) {
+	case string:
+		return v
+	case bool:
+		if v {
+			return "medium" // Default level when just true
+		}
+		return ""
+	default:
+		return ""
+	}
+}
+
+// UnmarshalJSON implements json.Unmarshaler
+func (t *ThinkValue) UnmarshalJSON(data []byte) error {
+	// Try to unmarshal as bool first
+	var b bool
+	if err := json.Unmarshal(data, &b); err == nil {
+		t.Value = b
+		return nil
+	}
+
+	// Try to unmarshal as string
+	var s string
+	if err := json.Unmarshal(data, &s); err == nil {
+		// Validate string values
+		if s != "high" && s != "medium" && s != "low" {
+			return fmt.Errorf("invalid think value: %q (must be \"high\", \"medium\", \"low\", true, or false)", s)
+		}
+		t.Value = s
+		return nil
+	}
+
+	return fmt.Errorf("think must be a boolean or string (\"high\", \"medium\", \"low\")")
+}
+
+// MarshalJSON implements json.Marshaler
+func (t *ThinkValue) MarshalJSON() ([]byte, error) {
+	if t == nil || t.Value == nil {
+		return []byte("null"), nil
+	}
+	return json.Marshal(t.Value)
+}
+
 type Duration struct {
 	time.Duration
 }

api/types_test.go

@@ -374,24 +374,21 @@ func TestPropertyType_MarshalJSON(t *testing.T) {
 }
 
 func TestThinking_UnmarshalJSON(t *testing.T) {
-	trueVal := true
-	falseVal := false
-
 	tests := []struct {
 		name             string
 		input            string
-		expectedThinking *bool
+		expectedThinking *ThinkValue
 		expectedError    bool
 	}{
 		{
 			name:             "true",
 			input:            `{ "think": true }`,
-			expectedThinking: &trueVal,
+			expectedThinking: &ThinkValue{Value: true},
 		},
 		{
 			name:             "false",
 			input:            `{ "think": false }`,
-			expectedThinking: &falseVal,
+			expectedThinking: &ThinkValue{Value: false},
 		},
 		{
 			name:             "unset",
@@ -399,8 +396,23 @@ func TestThinking_UnmarshalJSON(t *testing.T) {
 			expectedThinking: nil,
 		},
 		{
-			name:             "invalid",
-			input:            `{ "think": "true" }`,
+			name:             "string_high",
+			input:            `{ "think": "high" }`,
+			expectedThinking: &ThinkValue{Value: "high"},
+		},
+		{
+			name:             "string_medium",
+			input:            `{ "think": "medium" }`,
+			expectedThinking: &ThinkValue{Value: "medium"},
+		},
+		{
+			name:             "string_low",
+			input:            `{ "think": "low" }`,
+			expectedThinking: &ThinkValue{Value: "low"},
+		},
+		{
+			name:             "invalid_string",
+			input:            `{ "think": "invalid" }`,
 			expectedThinking: nil,
 			expectedError:    true,
 		},
@@ -414,7 +426,12 @@ func TestThinking_UnmarshalJSON(t *testing.T) {
 				require.Error(t, err)
 			} else {
 				require.NoError(t, err)
-				assert.Equal(t, test.expectedThinking, req.Think)
+				if test.expectedThinking == nil {
+					assert.Nil(t, req.Think)
+				} else {
+					require.NotNil(t, req.Think)
+					assert.Equal(t, test.expectedThinking.Value, req.Think.Value)
+				}
 			}
 		})
 	}

cmd/cmd.go

@@ -322,11 +322,23 @@ func RunHandler(cmd *cobra.Command, args []string) error {
 
 	thinkFlag := cmd.Flags().Lookup("think")
 	if thinkFlag.Changed {
-		think, err := cmd.Flags().GetBool("think")
+		thinkStr, err := cmd.Flags().GetString("think")
 		if err != nil {
 			return err
 		}
-		opts.Think = &think
+
+		// Handle different values for --think
+		switch thinkStr {
+		case "", "true":
+			// --think or --think=true
+			opts.Think = &api.ThinkValue{Value: true}
+		case "false":
+			opts.Think = &api.ThinkValue{Value: false}
+		case "high", "medium", "low":
+			opts.Think = &api.ThinkValue{Value: thinkStr}
+		default:
+			return fmt.Errorf("invalid value for --think: %q (must be true, false, high, medium, or low)", thinkStr)
+		}
 	} else {
 		opts.Think = nil
 	}
@@ -977,7 +989,7 @@ type runOptions struct {
 	Options      map[string]any
 	MultiModal   bool
 	KeepAlive    *api.Duration
-	Think        *bool
+	Think        *api.ThinkValue
 	HideThinking bool
 }
 
@@ -1017,10 +1029,11 @@ func displayResponse(content string, wordWrap bool, state *displayResponseState)
 				}
 
 				switch ch {
-				case ' ':
+				case ' ', '\t':
 					state.wordBuffer = ""
-				case '\n':
+				case '\n', '\r':
 					state.lineLength = 0
+					state.wordBuffer = ""
 				default:
 					state.wordBuffer += string(ch)
 				}
@@ -1078,6 +1091,7 @@ func chat(cmd *cobra.Command, opts runOptions) (*api.Message, error) {
 	}()
 
 	var state *displayResponseState = &displayResponseState{}
+	var thinkingContent strings.Builder
 	var latest api.ChatResponse
 	var fullResponse strings.Builder
 	var thinkTagOpened bool = false
@@ -1097,14 +1111,21 @@ func chat(cmd *cobra.Command, opts runOptions) (*api.Message, error) {
 			if !thinkTagOpened {
 				fmt.Print(thinkingOutputOpeningText(false))
 				thinkTagOpened = true
+				thinkTagClosed = false
 			}
+			thinkingContent.WriteString(response.Message.Thinking)
 			displayResponse(response.Message.Thinking, opts.WordWrap, state)
 		}
 
 		content := response.Message.Content
-		if thinkTagOpened && !thinkTagClosed && content != "" {
+		if thinkTagOpened && !thinkTagClosed && (content != "" || len(response.Message.ToolCalls) > 0) {
+			if !strings.HasSuffix(thinkingContent.String(), "\n") {
+				fmt.Println()
+			}
 			fmt.Print(thinkingOutputClosingText(false))
+			thinkTagOpened = false
 			thinkTagClosed = true
+			state = &displayResponseState{}
 		}
 		// purposefully not putting thinking blocks in the response, which would
 		// only be needed if we later added tool calling to the cli (they get
@@ -1112,6 +1133,13 @@ func chat(cmd *cobra.Command, opts runOptions) (*api.Message, error) {
 		// about to finish some tool calls)
 		fullResponse.WriteString(content)
 
+		if response.Message.ToolCalls != nil {
+			toolCalls := response.Message.ToolCalls
+			if len(toolCalls) > 0 {
+				fmt.Print(renderToolCalls(toolCalls, false))
+			}
+		}
+
 		displayResponse(content, opts.WordWrap, state)
 
 		return nil
@@ -1196,6 +1224,7 @@ func generate(cmd *cobra.Command, opts runOptions) error {
 	}()
 
 	var state *displayResponseState = &displayResponseState{}
+	var thinkingContent strings.Builder
 	var thinkTagOpened bool = false
 	var thinkTagClosed bool = false
 
@@ -1213,17 +1242,31 @@ func generate(cmd *cobra.Command, opts runOptions) error {
 			if !thinkTagOpened {
 				fmt.Print(thinkingOutputOpeningText(plainText))
 				thinkTagOpened = true
+				thinkTagClosed = false
 			}
+			thinkingContent.WriteString(response.Thinking)
 			displayResponse(response.Thinking, opts.WordWrap, state)
 		}
 
-		if thinkTagOpened && !thinkTagClosed && content != "" {
+		if thinkTagOpened && !thinkTagClosed && (content != "" || len(response.ToolCalls) > 0) {
+			if !strings.HasSuffix(thinkingContent.String(), "\n") {
+				fmt.Println()
+			}
 			fmt.Print(thinkingOutputClosingText(plainText))
+			thinkTagOpened = false
 			thinkTagClosed = true
+			state = &displayResponseState{}
 		}
 
 		displayResponse(content, opts.WordWrap, state)
 
+		if response.ToolCalls != nil {
+			toolCalls := response.ToolCalls
+			if len(toolCalls) > 0 {
+				fmt.Print(renderToolCalls(toolCalls, plainText))
+			}
+		}
+
 		return nil
 	}
 
@@ -1463,7 +1506,8 @@ func NewCLI() *cobra.Command {
 	runCmd.Flags().Bool("insecure", false, "Use an insecure registry")
 	runCmd.Flags().Bool("nowordwrap", false, "Don't wrap words to the next line automatically")
 	runCmd.Flags().String("format", "", "Response format (e.g. json)")
-	runCmd.Flags().Bool("think", false, "Whether to use thinking mode for supported models")
+	runCmd.Flags().String("think", "", "Enable thinking mode: true/false or high/medium/low for supported models")
+	runCmd.Flags().Lookup("think").NoOptDefVal = "true"
 	runCmd.Flags().Bool("hidethinking", false, "Hide thinking output (if provided)")
 
 	stopCmd := &cobra.Command{
@@ -1613,7 +1657,7 @@ func NewCLI() *cobra.Command {
 // to false).
 //
 // If capabilities are not provided, we fetch them from the server.
-func inferThinkingOption(caps *[]model.Capability, runOpts *runOptions, explicitlySetByUser bool) (*bool, error) {
+func inferThinkingOption(caps *[]model.Capability, runOpts *runOptions, explicitlySetByUser bool) (*api.ThinkValue, error) {
 	if explicitlySetByUser {
 		return runOpts.Think, nil
 	}
@@ -1640,9 +1684,34 @@ func inferThinkingOption(caps *[]model.Capability, runOpts *runOptions, explicit
 	}
 
 	if thinkingSupported {
-		thinking := true
-		return &thinking, nil
+		return &api.ThinkValue{Value: true}, nil
 	}
 
 	return nil, nil
 }
+
+func renderToolCalls(toolCalls []api.ToolCall, plainText bool) string {
+	out := ""
+	formatExplanation := ""
+	formatValues := ""
+	if !plainText {
+		formatExplanation = readline.ColorGrey + readline.ColorBold
+		formatValues = readline.ColorDefault
+		out += formatExplanation
+	}
+	for i, toolCall := range toolCalls {
+		argsAsJSON, err := json.Marshal(toolCall.Function.Arguments)
+		if err != nil {
+			return ""
+		}
+		if i > 0 {
+			out += "\n"
+		}
+		// all tool calls are unexpected since we don't currently support registering any in the CLI
+		out += fmt.Sprintf("  Model called a non-existent function '%s()' with arguments: %s", formatValues+toolCall.Function.Name+formatExplanation, formatValues+string(argsAsJSON)+formatExplanation)
+	}
+	if !plainText {
+		out += readline.ColorDefault
+	}
+	return out
+}

cmd/interactive.go

@@ -272,16 +272,29 @@ func generateInteractive(cmd *cobra.Command, opts runOptions) error {
 					}
 					fmt.Println("Set 'quiet' mode.")
 				case "think":
-					think := true
-					opts.Think = &think
+					thinkValue := api.ThinkValue{Value: true}
+					var maybeLevel string
+					if len(args) > 2 {
+						maybeLevel = args[2]
+					}
+					if maybeLevel != "" {
+						// TODO(drifkin): validate the level, could be model dependent
+						// though... It will also be validated on the server once a call is
+						// made.
+						thinkValue.Value = maybeLevel
+					}
+					opts.Think = &thinkValue
 					thinkExplicitlySet = true
 					if client, err := api.ClientFromEnvironment(); err == nil {
 						ensureThinkingSupport(cmd.Context(), client, opts.Model)
 					}
-					fmt.Println("Set 'think' mode.")
+					if maybeLevel != "" {
+						fmt.Printf("Set 'think' mode to '%s'.\n", maybeLevel)
+					} else {
+						fmt.Println("Set 'think' mode.")
+					}
 				case "nothink":
-					think := false
-					opts.Think = &think
+					opts.Think = &api.ThinkValue{Value: false}
 					thinkExplicitlySet = true
 					if client, err := api.ClientFromEnvironment(); err == nil {
 						ensureThinkingSupport(cmd.Context(), client, opts.Model)
@@ -478,7 +491,8 @@ func generateInteractive(cmd *cobra.Command, opts runOptions) error {
 
 			assistant, err := chat(cmd, opts)
 			if err != nil {
-				if strings.Contains(err.Error(), "does not support thinking") {
+				if strings.Contains(err.Error(), "does not support thinking") ||
+					strings.Contains(err.Error(), "invalid think value") {
 					fmt.Printf("error: %v\n", err)
 					sb.Reset()
 					continue

openai/openai.go

@@ -36,6 +36,7 @@ type ErrorResponse struct {
 type Message struct {
 	Role      string     `json:"role"`
 	Content   any        `json:"content"`
+	Reasoning string     `json:"reasoning,omitempty"`
 	ToolCalls []ToolCall `json:"tool_calls,omitempty"`
 }
 
@@ -81,6 +82,10 @@ type StreamOptions struct {
 	IncludeUsage bool `json:"include_usage"`
 }
 
+type Reasoning struct {
+	Effort *string `json:"effort,omitempty"`
+}
+
 type ChatCompletionRequest struct {
 	Model            string          `json:"model"`
 	Messages         []Message       `json:"messages"`
@@ -95,6 +100,7 @@ type ChatCompletionRequest struct {
 	TopP             *float64        `json:"top_p"`
 	ResponseFormat   *ResponseFormat `json:"response_format"`
 	Tools            []api.Tool      `json:"tools"`
+	Reasoning        *Reasoning      `json:"reasoning,omitempty"`
 }
 
 type ChatCompletion struct {
@@ -253,7 +259,7 @@ func toChatCompletion(id string, r api.ChatResponse) ChatCompletion {
 		SystemFingerprint: "fp_ollama",
 		Choices: []Choice{{
 			Index:   0,
-			Message: Message{Role: r.Message.Role, Content: r.Message.Content, ToolCalls: toolCalls},
+			Message: Message{Role: r.Message.Role, Content: r.Message.Content, ToolCalls: toolCalls, Reasoning: r.Message.Thinking},
 			FinishReason: func(reason string) *string {
 				if len(toolCalls) > 0 {
 					reason = "tool_calls"
@@ -278,10 +284,10 @@ func toChunk(id string, r api.ChatResponse, toolCallSent bool) ChatCompletionChu
 		SystemFingerprint: "fp_ollama",
 		Choices: []ChunkChoice{{
 			Index: 0,
-			Delta: Message{Role: "assistant", Content: r.Message.Content, ToolCalls: toolCalls},
+			Delta: Message{Role: "assistant", Content: r.Message.Content, ToolCalls: toolCalls, Reasoning: r.Message.Thinking},
 			FinishReason: func(reason string) *string {
 				if len(reason) > 0 {
-					if toolCallSent {
+					if toolCallSent || len(toolCalls) > 0 {
 						return &finishReasonToolCalls
 					}
 					return &reason
@@ -397,7 +403,7 @@ func fromChatRequest(r ChatCompletionRequest) (*api.ChatRequest, error) {
 	for _, msg := range r.Messages {
 		switch content := msg.Content.(type) {
 		case string:
-			messages = append(messages, api.Message{Role: msg.Role, Content: content})
+			messages = append(messages, api.Message{Role: msg.Role, Content: content, Thinking: msg.Reasoning})
 		case []any:
 			for _, c := range content {
 				data, ok := c.(map[string]any)
@@ -508,6 +514,10 @@ func fromChatRequest(r ChatCompletionRequest) (*api.ChatRequest, error) {
 		options["top_p"] = 1.0
 	}
 
+	if r.Reasoning != nil {
+		options["reasoning"] = *r.Reasoning.Effort
+	}
+
 	var format json.RawMessage
 	if r.ResponseFormat != nil {
 		switch strings.ToLower(strings.TrimSpace(r.ResponseFormat.Type)) {
@@ -521,6 +531,13 @@ func fromChatRequest(r ChatCompletionRequest) (*api.ChatRequest, error) {
 		}
 	}
 
+	var think *api.ThinkValue
+	if r.Reasoning != nil {
+		think = &api.ThinkValue{
+			Value: *r.Reasoning.Effort,
+		}
+	}
+
 	return &api.ChatRequest{
 		Model:    r.Model,
 		Messages: messages,
@@ -528,6 +545,7 @@ func fromChatRequest(r ChatCompletionRequest) (*api.ChatRequest, error) {
 		Options:  options,
 		Stream:   &r.Stream,
 		Tools:    r.Tools,
+		Think:    think,
 	}, nil
 }
 

server/harmonyparser.go

+package server
+
+import (
+	"context"
+	"log/slog"
+	"strings"
+	"unicode"
+
+	"github.com/ollama/ollama/api"
+	"github.com/ollama/ollama/logutil"
+)
+
+type harmonyParserState int
+
+const (
+	harmonyParserState_LookingForMessageStart harmonyParserState = iota
+	harmonyParserState_ParsingHeader
+	harmonyParserState_ParsingContent
+)
+
+func shouldUseHarmony(model Model) bool {
+	if model.Config.ModelFamily == "gptoss" {
+		// heuristic to check whether the template expects to be parsed via harmony:
+		// search for harmony tags that are nearly always used
+		if model.Template.Contains("<|start|>") && model.Template.Contains("<|end|>") {
+			return true
+		}
+	}
+
+	return false
+}
+
+func (s harmonyParserState) String() string {
+	switch s {
+	// we're looking for the message start tag
+	case harmonyParserState_LookingForMessageStart:
+		return "LookingForMessageStart"
+	case harmonyParserState_ParsingHeader:
+		return "ParsingHeader"
+	case harmonyParserState_ParsingContent:
+		return "ParsingContent"
+	default:
+		return "Unknown"
+	}
+}
+
+type HarmonyParser struct {
+	state           harmonyParserState
+	MessageStartTag string
+	MessageEndTag   string
+	HeaderEndTag    string
+	acc             strings.Builder
+	lifetimeAcc     strings.Builder
+}
+
+type HarmonyEvent interface {
+	isHarmonyEvent()
+}
+
+type HarmonyEventMessageStart struct{}
+
+func (HarmonyEventMessageStart) isHarmonyEvent() {}
+
+type HarmonyEventHeaderComplete struct {
+	Header HarmonyHeader
+}
+
+func (HarmonyEventHeaderComplete) isHarmonyEvent() {}
+
+type HarmonyEventContentEmitted struct {
+	Content string
+}
+
+func (HarmonyEventContentEmitted) isHarmonyEvent() {}
+
+type HarmonyEventMessageEnd struct{}
+
+func (HarmonyEventMessageEnd) isHarmonyEvent() {}
+
+type HarmonyHeader struct {
+	Role      string
+	Channel   string
+	Recipient string
+}
+
+func (s *HarmonyParser) AddImplicitStart() {
+	s.acc.WriteString("<|start|>assistant")
+}
+
+func (s *HarmonyParser) AddImplicitStartOrPrefill(lastMessage *api.Message) {
+	if lastMessage != nil && lastMessage.Role == "assistant" {
+		// handle prefilling conditions
+		if lastMessage.Content != "" {
+			s.acc.WriteString("<|start|>assistant<|channel|>final<|message|>")
+			return
+		} else if lastMessage.Thinking != "" {
+			s.acc.WriteString("<|start|>assistant<|channel|>analysis<|message|>")
+			return
+		}
+	}
+	s.AddImplicitStart()
+}
+
+func (s *HarmonyParser) AddContent(content string) []HarmonyEvent {
+	s.lifetimeAcc.WriteString(content)
+	s.acc.WriteString(content)
+
+	var events []HarmonyEvent
+
+	keepLooping := true
+	// we loop because we might pass through multiple parsing states in a single
+	// call to addContent, and we want to make sure callers don't have to wait for
+	// data that's already unambiguous
+	for keepLooping {
+		var newEvents []HarmonyEvent
+		newEvents, keepLooping = eat(s)
+		events = append(events, newEvents...)
+	}
+
+	return events
+}
+
+// the additional bool return is true iff we should continue eating
+func eat(s *HarmonyParser) ([]HarmonyEvent, bool) {
+	switch s.state {
+	case harmonyParserState_LookingForMessageStart:
+		// does the acc contain the message start tag?
+		if strings.Contains(s.acc.String(), s.MessageStartTag) {
+			// split the acc into the message start tag and the rest
+			split := strings.SplitN(s.acc.String(), s.MessageStartTag, 2)
+			before := split[0]
+			if before != "" {
+				slog.Warn("harmony parser: found message start tag in the middle of the content", "content", s.acc.String())
+			}
+			after := split[1]
+			s.acc.Reset()
+			s.acc.WriteString(after)
+			s.state = harmonyParserState_ParsingHeader
+			return []HarmonyEvent{HarmonyEventMessageStart{}}, true
+		}
+
+		// no match, so we keep accumulating
+		return nil, false
+	case harmonyParserState_ParsingHeader:
+		if strings.Contains(s.acc.String(), s.HeaderEndTag) {
+			split := strings.SplitN(s.acc.String(), s.HeaderEndTag, 2)
+			header := split[0]
+			after := split[1]
+			s.acc.Reset()
+			s.acc.WriteString(after)
+			s.state = harmonyParserState_ParsingContent
+			return []HarmonyEvent{HarmonyEventHeaderComplete{Header: s.parseHeader(header)}}, true
+		}
+		return nil, false
+	case harmonyParserState_ParsingContent:
+		if strings.Contains(s.acc.String(), s.MessageEndTag) {
+			// if we already have the message end tag, we can emit the content up to it
+			split := strings.SplitN(s.acc.String(), s.MessageEndTag, 2)
+			content := split[0]
+			after := split[1]
+			s.acc.Reset()
+			s.acc.WriteString(after)
+			s.state = harmonyParserState_LookingForMessageStart
+			events := []HarmonyEvent{}
+			if content != "" {
+				events = append(events, HarmonyEventContentEmitted{Content: content})
+			}
+			events = append(events, HarmonyEventMessageEnd{})
+			return events, true
+		} else if overlapLen := overlap(s.acc.String(), s.MessageEndTag); overlapLen > 0 {
+			// if our suffix contains the start of the message end tag, we can emit
+			// the content up to the start of the message end tag
+			content := s.acc.String()[:len(s.acc.String())-overlapLen]
+			remaining := s.acc.String()[len(s.acc.String())-overlapLen:]
+			s.acc.Reset()
+			s.acc.WriteString(remaining)
+			// emit the content we know isn't part of the message end tag, and keep
+			// accumulating to disambiguate the rest
+			if content == "" {
+				return nil, false
+			}
+			return []HarmonyEvent{HarmonyEventContentEmitted{Content: content}}, false
+		} else {
+			// no end tag, so it's still normal content that we can immediately emit
+			content := s.acc.String()
+			if content == "" {
+				return nil, false
+			}
+			s.acc.Reset()
+			return []HarmonyEvent{HarmonyEventContentEmitted{Content: content}}, false
+		}
+	}
+
+	return nil, false
+}
+
+func (s *HarmonyParser) parseHeader(raw string) HarmonyHeader {
+	harmonyHeader := HarmonyHeader{}
+
+	// if `<|constrain|>` is present, ensure it has a space before it so it gets
+	// parsed as a separate token, even if the model didn't include the space
+	if strings.Contains(raw, "<|constrain|>") {
+		raw = strings.Replace(raw, "<|constrain|>", " <|constrain|>", 1)
+		raw = strings.TrimSpace(raw)
+	}
+
+	// look for the optional channel tag, which is `<|channel|>` followed by the
+	// channel name, all without any whitespace
+	channelIndex := strings.Index(raw, "<|channel|>")
+	if channelIndex != -1 {
+		before := raw[:channelIndex]
+		after := raw[channelIndex+len("<|channel|>"):]
+		// the channel name is `after` all the way up to the first (if any) whitespace character
+		idx := strings.IndexFunc(after, func(r rune) bool {
+			return unicode.IsSpace(r)
+		})
+		if idx == -1 {
+			idx = len(after)
+		}
+		harmonyHeader.Channel = after[:idx]
+		after = after[idx:]
+		// now we remove the channel tag from the raw string to further process
+		raw = before + after
+		raw = strings.TrimSpace(raw)
+	}
+
+	// split the header into whitespace-separated tokens
+	tokens := strings.Fields(raw)
+
+	// the first token is treated as the role
+	if len(tokens) == 0 {
+		slog.Error("harmony parser: missing role in header", "header", raw)
+		return harmonyHeader
+	}
+	role := tokens[0]
+	tokens = tokens[1:]
+	// special case: if role starts with to= then it's a tool call
+	if strings.HasPrefix(role, "to=") {
+		harmonyHeader.Recipient = role[3:]
+		harmonyHeader.Role = "tool"
+	} else {
+		harmonyHeader.Role = role
+	}
+
+	// the recipient (if any) can be specified before or after the channel tag, so
+	// we check it at the end once we've already parsed the channel and role
+	if harmonyHeader.Recipient == "" && len(tokens) > 0 && strings.HasPrefix(tokens[0], "to=") {
+		harmonyHeader.Recipient = tokens[0][3:]
+	}
+
+	return harmonyHeader
+}
+
+// longest overlap between suffix of s and prefix of delim
+func overlap(s, delim string) int {
+	max := min(len(delim), len(s))
+	for i := max; i > 0; i-- {
+		if strings.HasSuffix(s, delim[:i]) {
+			return i
+		}
+	}
+	return 0
+}
+
+// harmonyMessageState represents the current state of message processing
+type harmonyMessageState int
+
+const (
+	harmonyMessageState_Normal harmonyMessageState = iota
+	harmonyMessageState_Thinking
+	harmonyMessageState_ToolCalling
+)
+
+// HarmonyMessageHandler processes harmony events and accumulates content appropriately.
+// This is a higher level interface that maps harmony concepts into ollama concepts
+type HarmonyMessageHandler struct {
+	state         harmonyMessageState
+	harmonyParser *HarmonyParser
+}
+
+// NewHarmonyMessageHandler creates a new message handler
+func NewHarmonyMessageHandler() *HarmonyMessageHandler {
+	return &HarmonyMessageHandler{
+		state: harmonyMessageState_Normal,
+		harmonyParser: &HarmonyParser{
+			MessageStartTag: "<|start|>",
+			MessageEndTag:   "<|end|>",
+			HeaderEndTag:    "<|message|>",
+		},
+	}
+}
+
+// AddContent processes the content and returns the content, thinking, and tool content.
+// content and thinking are already fully parsed, but tool content still needs to be passed to the tool parser
+func (h *HarmonyMessageHandler) AddContent(content string, toolParser *HarmonyToolCallAccumulator) (string, string, string) {
+	contentSb := strings.Builder{}
+	thinkingSb := strings.Builder{}
+	toolContentSb := strings.Builder{}
+
+	events := h.harmonyParser.AddContent(content)
+	for _, event := range events {
+		switch event := event.(type) {
+		case HarmonyEventHeaderComplete:
+			slog.Log(context.TODO(), logutil.LevelTrace, "harmony event header complete", "header", event.Header)
+			switch event.Header.Channel {
+			case "analysis":
+				if event.Header.Recipient != "" {
+					h.state = harmonyMessageState_ToolCalling
+					// event.Header.Recipient is the tool name, something like
+					// "browser.search" for a built-in, or "functions.calc" for a
+					// custom one
+					toolParser.SetToolName(event.Header.Recipient)
+				} else {
+					h.state = harmonyMessageState_Thinking
+				}
+			case "commentary":
+				if event.Header.Recipient != "" {
+					h.state = harmonyMessageState_ToolCalling
+					toolParser.SetToolName(event.Header.Recipient)
+				} else {
+					h.state = harmonyMessageState_Normal
+				}
+			case "final":
+				h.state = harmonyMessageState_Normal
+			}
+		case HarmonyEventContentEmitted:
+			slog.Log(context.TODO(), logutil.LevelTrace, "harmony event content", "content", event.Content, "state", h.state)
+			if h.state == harmonyMessageState_Normal {
+				contentSb.WriteString(event.Content)
+			} else if h.state == harmonyMessageState_Thinking {
+				thinkingSb.WriteString(event.Content)
+			} else if h.state == harmonyMessageState_ToolCalling {
+				toolContentSb.WriteString(event.Content)
+			}
+		case HarmonyEventMessageEnd:
+			h.state = harmonyMessageState_Normal
+		}
+	}
+	return contentSb.String(), thinkingSb.String(), toolContentSb.String()
+}
+
+func (h *HarmonyMessageHandler) CreateToolParser() *HarmonyToolCallAccumulator {
+	return &HarmonyToolCallAccumulator{
+		state:           harmonyToolCallState_Normal,
+		currentToolName: nil,
+	}
+}
+
+type harmonyToolCallState int
+
+const (
+	harmonyToolCallState_Normal harmonyToolCallState = iota
+	harmonyToolCallState_ToolCalling
+)
+
+type HarmonyToolCallAccumulator struct {
+	state           harmonyToolCallState
+	acc             strings.Builder
+	currentToolName *string
+}
+
+func (a *HarmonyToolCallAccumulator) SetToolName(toolName string) {
+	a.currentToolName = &toolName
+}
+
+func (a *HarmonyToolCallAccumulator) Add(content string) {
+	a.acc.WriteString(content)
+}
+
+func (a *HarmonyToolCallAccumulator) Drain() (*string, string) {
+	str := a.acc.String()
+	a.state = harmonyToolCallState_Normal
+	a.acc.Reset()
+	return a.currentToolName, str
+}
+
+func (a *HarmonyToolCallAccumulator) Content() string {
+	return a.acc.String()
+}

server/harmonyparser_test.go

+package server
+
+import (
+	"fmt"
+	"reflect"
+	"testing"
+)
+
+func TestHeaderParsing(t *testing.T) {
+	tests := []struct {
+		in, wantRole, wantChannel, wantRecipient string
+	}{
+		{
+			in:            "assistant<|channel|>analysis",
+			wantRole:      "assistant",
+			wantChannel:   "analysis",
+			wantRecipient: "",
+		},
+		{
+			in:            "assistant<|channel|>analysis to=functions.get_weather",
+			wantRole:      "assistant",
+			wantChannel:   "analysis",
+			wantRecipient: "functions.get_weather",
+		},
+		{
+			in:            "assistant to=functions.get_weather<|channel|>analysis",
+			wantRole:      "assistant",
+			wantChannel:   "analysis",
+			wantRecipient: "functions.get_weather",
+		},
+		// special case where the role is replaced by the recipient (matches reference code)
+		{
+			in:            "to=functions.get_weather<|channel|>analysis",
+			wantRole:      "tool",
+			wantChannel:   "analysis",
+			wantRecipient: "functions.get_weather",
+		},
+		// extra token after the recipient is ignored
+		{
+			in:            "assistant to=functions.get_weather abc<|channel|>analysis",
+			wantRole:      "assistant",
+			wantChannel:   "analysis",
+			wantRecipient: "functions.get_weather",
+		},
+		// with constrain tag, recipient after channel tag
+		{
+			in:            "assistant<|channel|>commentary to=functions.get_weather <|constrain|>json",
+			wantRole:      "assistant",
+			wantChannel:   "commentary",
+			wantRecipient: "functions.get_weather",
+		},
+		// with constrain tag, recipient before channel tag
+		{
+			in:            "assistant to=functions.get_weather<|channel|>commentary <|constrain|>json",
+			wantRole:      "assistant",
+			wantChannel:   "commentary",
+			wantRecipient: "functions.get_weather",
+		},
+		// constrain tag without space
+		{
+			in:            "assistant<|channel|>commentary to=functions.get_weather<|constrain|>json",
+			wantRole:      "assistant",
+			wantChannel:   "commentary",
+			wantRecipient: "functions.get_weather",
+		},
+		// constrain tag without space, different order
+		{
+			in:            "assistant to=functions.get_weather<|channel|>commentary<|constrain|>json",
+			wantRole:      "assistant",
+			wantChannel:   "commentary",
+			wantRecipient: "functions.get_weather",
+		},
+	}
+	for i, tt := range tests {
+		parser := HarmonyParser{
+			MessageStartTag: "<|start|>",
+			MessageEndTag:   "<|end|>",
+			HeaderEndTag:    "<|message|>",
+		}
+		header := parser.parseHeader(tt.in)
+
+		if header.Role != tt.wantRole {
+			t.Errorf("case %d: got role \"%s\", want \"%s\"", i, header.Role, tt.wantRole)
+		}
+		if header.Channel != tt.wantChannel {
+			t.Errorf("case %d: got channel \"%s\", want \"%s\"", i, header.Channel, tt.wantChannel)
+		}
+		if header.Recipient != tt.wantRecipient {
+			t.Errorf("case %d: got recipient \"%s\", want \"%s\"", i, header.Recipient, tt.wantRecipient)
+		}
+	}
+}
+
+func TestHarmonyParserHeaderEvent(t *testing.T) {
+	tests := []struct {
+		in, wantRole, wantChannel, wantRecipient string
+		implicitStart                            bool
+	}{
+		{
+			in:            "<|start|>user<|message|>What is 2 + 2?<|end|>",
+			wantRole:      "user",
+			wantChannel:   "",
+			wantRecipient: "",
+		},
+		{
+			in:            "<|start|>assistant<|channel|>analysis<|message|>What is 2 + 2?<|end|>",
+			wantRole:      "assistant",
+			wantChannel:   "analysis",
+			wantRecipient: "",
+		},
+		{
+			in:            "<|start|>assistant<|channel|>commentary to=functions.get_weather <|constrain|>json<|message|>{\"location\":\"San Francisco\"}<|call|><|start|>functions.get_weather to=assistant<|message|>{\"sunny\": true, \"temperature\": 20}<|end|>",
+			wantRole:      "assistant",
+			wantChannel:   "commentary",
+			wantRecipient: "functions.get_weather",
+		},
+		{
+			in:            "<|channel|>analysis<|message|>User asks weather in SF. We need location. Use get_current_weather with location \"San Francisco, CA\".<|end|><|start|>assistant<|channel|>commentary to=functions.get_current_weather <|constrain|>json<|message|>{\"location\":\"San Francisco, CA\"}<|call|>",
+			wantRole:      "assistant",
+			wantChannel:   "analysis",
+			wantRecipient: "",
+			implicitStart: true,
+		},
+	}
+	for i, tt := range tests {
+		parser := HarmonyParser{
+			MessageStartTag: "<|start|>",
+			MessageEndTag:   "<|end|>",
+			HeaderEndTag:    "<|message|>",
+		}
+		if tt.implicitStart {
+			parser.AddImplicitStart()
+		}
+		gotEvents := parser.AddContent(tt.in)
+		if len(gotEvents) == 0 {
+			t.Errorf("case %d: got no events, want at least one", i)
+		}
+
+		var firstHeaderEvent *HarmonyEventHeaderComplete
+		// print events
+		for _, event := range gotEvents {
+			fmt.Printf("event: %+v\n", event)
+		}
+		for _, event := range gotEvents {
+			if event, ok := event.(HarmonyEventHeaderComplete); ok {
+				firstHeaderEvent = &event
+				break
+			}
+		}
+
+		if firstHeaderEvent == nil {
+			t.Errorf("case %d: got no header complete event, want one", i)
+			continue
+		}
+		gotHeader := firstHeaderEvent.Header
+		if gotHeader.Role != tt.wantRole || gotHeader.Channel != tt.wantChannel || gotHeader.Recipient != tt.wantRecipient {
+			t.Errorf("case %d: got header %+v, want role=%s channel=%s recipient=%s", i, gotHeader, tt.wantRole, tt.wantChannel, tt.wantRecipient)
+		}
+	}
+}
+
+func TestHarmonyParserNonStreaming(t *testing.T) {
+	tests := []struct {
+		in            string
+		implicitStart bool
+		wantEvents    []HarmonyEvent
+	}{
+		{
+			in: "<|start|>user<|message|>What is 2 + 2?<|end|>",
+			wantEvents: []HarmonyEvent{
+				HarmonyEventMessageStart{},
+				HarmonyEventHeaderComplete{Header: HarmonyHeader{Role: "user", Channel: "", Recipient: ""}},
+				HarmonyEventContentEmitted{Content: "What is 2 + 2?"},
+				HarmonyEventMessageEnd{},
+			},
+		},
+		{
+			in: "<|start|>assistant<|channel|>analysis<|message|>The answer is 4<|end|>",
+			wantEvents: []HarmonyEvent{
+				HarmonyEventMessageStart{},
+				HarmonyEventHeaderComplete{Header: HarmonyHeader{Role: "assistant", Channel: "analysis", Recipient: ""}},
+				HarmonyEventContentEmitted{Content: "The answer is 4"},
+				HarmonyEventMessageEnd{},
+			},
+		},
+		{
+			in: "<|start|>assistant<|channel|>commentary to=functions.calc<|message|>Computing...<|end|>",
+			wantEvents: []HarmonyEvent{
+				HarmonyEventMessageStart{},
+				HarmonyEventHeaderComplete{Header: HarmonyHeader{Role: "assistant", Channel: "commentary", Recipient: "functions.calc"}},
+				HarmonyEventContentEmitted{Content: "Computing..."},
+				HarmonyEventMessageEnd{},
+			},
+		},
+		{
+			in: "<|start|>user<|message|><|end|>",
+			wantEvents: []HarmonyEvent{
+				HarmonyEventMessageStart{},
+				HarmonyEventHeaderComplete{Header: HarmonyHeader{Role: "user", Channel: "", Recipient: ""}},
+				HarmonyEventMessageEnd{},
+			},
+		},
+		{
+			in: "<|start|>user<|message|>Hello<|end|><|start|>assistant<|message|>Hi!<|end|>",
+			wantEvents: []HarmonyEvent{
+				HarmonyEventMessageStart{},
+				HarmonyEventHeaderComplete{Header: HarmonyHeader{Role: "user", Channel: "", Recipient: ""}},
+				HarmonyEventContentEmitted{Content: "Hello"},
+				HarmonyEventMessageEnd{},
+				HarmonyEventMessageStart{},
+				HarmonyEventHeaderComplete{Header: HarmonyHeader{Role: "assistant", Channel: "", Recipient: ""}},
+				HarmonyEventContentEmitted{Content: "Hi!"},
+				HarmonyEventMessageEnd{},
+			},
+		},
+		{
+			in:            "<|channel|>analysis<|message|>Thinking about the request<|end|>",
+			implicitStart: true,
+			wantEvents:    []HarmonyEvent{HarmonyEventMessageStart{}, HarmonyEventHeaderComplete{Header: HarmonyHeader{Role: "assistant", Channel: "analysis", Recipient: ""}}, HarmonyEventContentEmitted{Content: "Thinking about the request"}, HarmonyEventMessageEnd{}},
+		},
+	}
+	for i, tt := range tests {
+		parser := HarmonyParser{
+			MessageStartTag: "<|start|>",
+			MessageEndTag:   "<|end|>",
+			HeaderEndTag:    "<|message|>",
+		}
+		if tt.implicitStart {
+			parser.AddImplicitStart()
+		}
+		gotEvents := parser.AddContent(tt.in)
+		if !reflect.DeepEqual(gotEvents, tt.wantEvents) {
+			t.Errorf("case %d: got events %#v, want %#v", i, gotEvents, tt.wantEvents)
+		}
+	}
+}
+
+func TestHarmonyParserStreaming(t *testing.T) {
+	type step struct {
+		input      string
+		wantEvents []HarmonyEvent
+	}
+
+	cases := []struct {
+		desc          string
+		implicitStart bool
+		steps         []step
+	}{
+		{
+			desc: "simple message streamed character by character",
+			steps: []step{
+				{
+					input:      "<",
+					wantEvents: nil,
+				},
+				{
+					input:      "|",
+					wantEvents: nil,
+				},
+				{
+					input:      "start|>u",
+					wantEvents: []HarmonyEvent{HarmonyEventMessageStart{}},
+				},
+				{
+					input:      "ser<|mess",
+					wantEvents: nil,
+				},
+				{
+					input: "age|>Hi",
+					wantEvents: []HarmonyEvent{
+						HarmonyEventHeaderComplete{Header: HarmonyHeader{Role: "user", Channel: "", Recipient: ""}},
+						HarmonyEventContentEmitted{Content: "Hi"},
+					},
+				},
+				{
+					input:      " there",
+					wantEvents: []HarmonyEvent{HarmonyEventContentEmitted{Content: " there"}},
+				},
+				{
+					input:      "<|e",
+					wantEvents: nil,
+				},
+				{
+					input:      "nd|>",
+					wantEvents: []HarmonyEvent{HarmonyEventMessageEnd{}},
+				},
+			},
+		},
+		{
+			desc: "message with channel streamed",
+			steps: []step{
+				{
+					input:      "<|start|>assistant",
+					wantEvents: []HarmonyEvent{HarmonyEventMessageStart{}},
+				},
+				{
+					input:      "<|chan",
+					wantEvents: nil,
+				},
+				{
+					input:      "nel|>analysis",
+					wantEvents: nil,
+				},
+				{
+					input:      "<|message|>",
+					wantEvents: []HarmonyEvent{HarmonyEventHeaderComplete{Header: HarmonyHeader{Role: "assistant", Channel: "analysis", Recipient: ""}}},
+				},
+				{
+					input:      "Thinking",
+					wantEvents: []HarmonyEvent{HarmonyEventContentEmitted{Content: "Thinking"}},
+				},
+				{
+					input:      "...",
+					wantEvents: []HarmonyEvent{HarmonyEventContentEmitted{Content: "..."}},
+				},
+				{
+					input:      "<|end|>",
+					wantEvents: []HarmonyEvent{HarmonyEventMessageEnd{}},
+				},
+			},
+		},
+		{
+			desc: "message with channel and recipient",
+			steps: []step{
+				{
+					input: "<|start|>assistant<|channel|>commentary to=functions.calc<|message|>",
+					wantEvents: []HarmonyEvent{
+						HarmonyEventMessageStart{},
+						HarmonyEventHeaderComplete{Header: HarmonyHeader{Role: "assistant", Channel: "commentary", Recipient: "functions.calc"}},
+					},
+				},
+				{
+					input:      "{\"x\": 5}",
+					wantEvents: []HarmonyEvent{HarmonyEventContentEmitted{Content: "{\"x\": 5}"}},
+				},
+				{
+					input:      "<|end|>",
+					wantEvents: []HarmonyEvent{HarmonyEventMessageEnd{}},
+				},
+			},
+		},
+		{
+			desc: "message with channel and recipient (receipient before channel)",
+			steps: []step{
+				{
+					input: "<|start|>assistant to=functions.calc<|channel|>commentary<|message|>",
+					wantEvents: []HarmonyEvent{
+						HarmonyEventMessageStart{},
+						HarmonyEventHeaderComplete{Header: HarmonyHeader{Role: "assistant", Channel: "commentary", Recipient: "functions.calc"}},
+					},
+				},
+				{
+					input:      "{\"x\": 5}",
+					wantEvents: []HarmonyEvent{HarmonyEventContentEmitted{Content: "{\"x\": 5}"}},
+				},
+				{
+					input:      "<|end|>",
+					wantEvents: []HarmonyEvent{HarmonyEventMessageEnd{}},
+				},
+			},
+		},
+		{
+			desc:          "implicit start with channel",
+			implicitStart: true,
+			steps: []step{
+				{
+					input:      "<|channel|>thinking",
+					wantEvents: []HarmonyEvent{HarmonyEventMessageStart{}},
+				},
+				{
+					input:      "<|message|>",
+					wantEvents: []HarmonyEvent{HarmonyEventHeaderComplete{Header: HarmonyHeader{Role: "assistant", Channel: "thinking", Recipient: ""}}},
+				},
+				{
+					input:      "Processing request",
+					wantEvents: []HarmonyEvent{HarmonyEventContentEmitted{Content: "Processing request"}},
+				},
+				{
+					input:      "<|end|>",
+					wantEvents: []HarmonyEvent{HarmonyEventMessageEnd{}},
+				},
+			},
+		},
+		{
+			desc: "multiple messages streamed",
+			steps: []step{
+				{
+					input: "<|start|>user<|message|>Hello<|end|>",
+					wantEvents: []HarmonyEvent{
+						HarmonyEventMessageStart{},
+						HarmonyEventHeaderComplete{Header: HarmonyHeader{Role: "user", Channel: "", Recipient: ""}},
+						HarmonyEventContentEmitted{Content: "Hello"},
+						HarmonyEventMessageEnd{},
+					},
+				},
+				{
+					input:      "<|start|>",
+					wantEvents: []HarmonyEvent{HarmonyEventMessageStart{}},
+				},
+				{
+					input:      "assistant<|message|>",
+					wantEvents: []HarmonyEvent{HarmonyEventHeaderComplete{Header: HarmonyHeader{Role: "assistant", Channel: "", Recipient: ""}}},
+				},
+				{
+					input:      "Hi!",
+					wantEvents: []HarmonyEvent{HarmonyEventContentEmitted{Content: "Hi!"}},
+				},
+				{
+					input:      "<|end|>",
+					wantEvents: []HarmonyEvent{HarmonyEventMessageEnd{}},
+				},
+			},
+		},
+		{
+			desc: "empty message",
+			steps: []step{
+				{
+					input: "<|start|>system<|message|><|end|>",
+					wantEvents: []HarmonyEvent{
+						HarmonyEventMessageStart{},
+						HarmonyEventHeaderComplete{Header: HarmonyHeader{Role: "system", Channel: "", Recipient: ""}},
+						HarmonyEventMessageEnd{},
+					},
+				},
+			},
+		},
+		{
+			desc: "partial tag that looks like end but isn't",
+			steps: []step{
+				{
+					input: "<|start|>user<|message|>test<|e",
+					wantEvents: []HarmonyEvent{
+						HarmonyEventMessageStart{},
+						HarmonyEventHeaderComplete{Header: HarmonyHeader{Role: "user", Channel: "", Recipient: ""}},
+						HarmonyEventContentEmitted{Content: "test"},
+					},
+				},
+				{
+					input:      "xample|>more",
+					wantEvents: []HarmonyEvent{HarmonyEventContentEmitted{Content: "<|example|>more"}},
+				},
+				{
+					input:      "<|end|>",
+					wantEvents: []HarmonyEvent{HarmonyEventMessageEnd{}},
+				},
+			},
+		},
+	}
+
+	for _, tc := range cases {
+		t.Run(tc.desc, func(t *testing.T) {
+			parser := HarmonyParser{
+				MessageStartTag: "<|start|>",
+				MessageEndTag:   "<|end|>",
+				HeaderEndTag:    "<|message|>",
+			}
+			if tc.implicitStart {
+				parser.AddImplicitStart()
+			}
+
+			for i, step := range tc.steps {
+				gotEvents := parser.AddContent(step.input)
+				if !reflect.DeepEqual(gotEvents, step.wantEvents) {
+					t.Errorf("step %d: input %q: got events %#v, want %#v", i, step.input, gotEvents, step.wantEvents)
+				}
+			}
+		})
+	}
+}

server/images.go

@@ -111,7 +111,8 @@ func (m *Model) Capabilities() []model.Capability {
 
 	// Check for thinking capability
 	openingTag, closingTag := thinking.InferTags(m.Template.Template)
-	if openingTag != "" && closingTag != "" {
+	hasTags := openingTag != "" && closingTag != ""
+	if hasTags || m.Config.ModelFamily == "gptoss" {
 		capabilities = append(capabilities, model.CapabilityThinking)
 	}
 

server/prompt.go

@@ -19,7 +19,7 @@ type tokenizeFunc func(context.Context, string) ([]int, error)
 // chatPrompt accepts a list of messages and returns the prompt and images that should be used for the next chat turn.
 // chatPrompt truncates any messages that exceed the context window of the model, making sure to always include 1) the
 // latest message and 2) system messages
-func chatPrompt(ctx context.Context, m *Model, tokenize tokenizeFunc, opts *api.Options, msgs []api.Message, tools []api.Tool, think *bool) (prompt string, images []llm.ImageData, _ error) {
+func chatPrompt(ctx context.Context, m *Model, tokenize tokenizeFunc, opts *api.Options, msgs []api.Message, tools []api.Tool, think *api.ThinkValue) (prompt string, images []llm.ImageData, _ error) {
 	var system []api.Message
 
 	// TODO: Ideally we would compute this from the projector metadata but some pieces are implementation dependent
@@ -42,11 +42,13 @@ func chatPrompt(ctx context.Context, m *Model, tokenize tokenizeFunc, opts *api.
 		}
 
 		thinkVal := false
+		thinkLevel := ""
 		if think != nil {
-			thinkVal = *think
+			thinkVal = think.AsBool()
+			thinkLevel = think.AsString()
 		}
 		var b bytes.Buffer
-		if err := m.Template.Execute(&b, template.Values{Messages: append(system, msgs[i:]...), Tools: tools, Think: thinkVal, IsThinkSet: think != nil}); err != nil {
+		if err := m.Template.Execute(&b, template.Values{Messages: append(system, msgs[i:]...), Tools: tools, Think: thinkVal, ThinkLevel: thinkLevel, IsThinkSet: think != nil}); err != nil {
 			return "", nil, err
 		}
 
@@ -101,10 +103,12 @@ func chatPrompt(ctx context.Context, m *Model, tokenize tokenizeFunc, opts *api.
 	// truncate any messages that do not fit into the context window
 	var b bytes.Buffer
 	thinkVal := false
+	thinkLevel := ""
 	if think != nil {
-		thinkVal = *think
+		thinkVal = think.AsBool()
+		thinkLevel = think.AsString()
 	}
-	if err := m.Template.Execute(&b, template.Values{Messages: append(system, msgs[currMsgIdx:]...), Tools: tools, Think: thinkVal, IsThinkSet: think != nil}); err != nil {
+	if err := m.Template.Execute(&b, template.Values{Messages: append(system, msgs[currMsgIdx:]...), Tools: tools, Think: thinkVal, ThinkLevel: thinkLevel, IsThinkSet: think != nil}); err != nil {
 		return "", nil, err
 	}
 

server/prompt_test.go

@@ -209,7 +209,7 @@ func TestChatPrompt(t *testing.T) {
 			model := tt.model
 			opts := api.Options{Runner: api.Runner{NumCtx: tt.limit}}
 			think := false
-			prompt, images, err := chatPrompt(t.Context(), &model, mockRunner{}.Tokenize, &opts, tt.msgs, nil, &think)
+			prompt, images, err := chatPrompt(t.Context(), &model, mockRunner{}.Tokenize, &opts, tt.msgs, nil, &api.ThinkValue{Value: think})
 			if tt.error == nil && err != nil {
 				t.Fatal(err)
 			} else if tt.error != nil && err != tt.error {

server/routes.go

@@ -187,11 +187,26 @@ func (s *Server) GenerateHandler(c *gin.Context) {
 		return
 	}
 
+	useHarmony := shouldUseHarmony(*m) && !req.Raw
+	var harmonyMessageHandler *HarmonyMessageHandler
+	var harmonyToolParser *HarmonyToolCallAccumulator
+	if useHarmony {
+		harmonyMessageHandler = NewHarmonyMessageHandler()
+		harmonyMessageHandler.harmonyParser.AddImplicitStart()
+		harmonyToolParser = harmonyMessageHandler.CreateToolParser()
+	}
+
+	// Validate Think value: string values currently only allowed for gptoss models
+	if req.Think != nil && req.Think.IsString() && !useHarmony {
+		c.JSON(http.StatusBadRequest, gin.H{"error": fmt.Sprintf("think value %q is not supported for this model", req.Think.AsString())})
+		return
+	}
+
 	caps := []model.Capability{model.CapabilityCompletion}
 	if req.Suffix != "" {
 		caps = append(caps, model.CapabilityInsert)
 	}
-	if req.Think != nil && *req.Think {
+	if req.Think != nil && req.Think.AsBool() {
 		caps = append(caps, model.CapabilityThinking)
 		// TODO(drifkin): consider adding a warning if it's false and the model
 		// doesn't support thinking. It's not strictly required, but it can be a
@@ -266,7 +281,11 @@ func (s *Server) GenerateHandler(c *gin.Context) {
 			values.Messages = append(msgs, api.Message{Role: "user", Content: req.Prompt})
 		}
 
-		values.Think = req.Think != nil && *req.Think
+		values.Think = req.Think != nil && req.Think.AsBool()
+		values.ThinkLevel = ""
+		if req.Think != nil {
+			values.ThinkLevel = req.Think.AsString()
+		}
 		values.IsThinkSet = req.Think != nil
 
 		var b bytes.Buffer
@@ -289,11 +308,13 @@ func (s *Server) GenerateHandler(c *gin.Context) {
 	}
 
 	var thinkingState *thinking.Parser
-	openingTag, closingTag := thinking.InferTags(m.Template.Template)
-	if req.Think != nil && *req.Think && openingTag != "" && closingTag != "" {
-		thinkingState = &thinking.Parser{
-			OpeningTag: openingTag,
-			ClosingTag: closingTag,
+	if !useHarmony {
+		openingTag, closingTag := thinking.InferTags(m.Template.Template)
+		if req.Think != nil && req.Think.AsBool() && openingTag != "" && closingTag != "" {
+			thinkingState = &thinking.Parser{
+				OpeningTag: openingTag,
+				ClosingTag: closingTag,
+			}
 		}
 	}
 
@@ -321,7 +342,12 @@ func (s *Server) GenerateHandler(c *gin.Context) {
 				},
 			}
 
-			if thinkingState != nil {
+			if useHarmony {
+				content, thinking, toolContent := harmonyMessageHandler.AddContent(cr.Content, harmonyToolParser)
+				res.Response = content
+				res.Thinking = thinking
+				harmonyToolParser.Add(toolContent)
+			} else if thinkingState != nil {
 				thinking, content := thinkingState.AddContent(cr.Content)
 				res.Thinking = thinking
 				res.Response = content
@@ -332,6 +358,25 @@ func (s *Server) GenerateHandler(c *gin.Context) {
 			}
 
 			if cr.Done {
+				if useHarmony {
+					toolName, toolContent := harmonyToolParser.Drain()
+					if toolName != nil {
+						*toolName = strings.TrimPrefix(*toolName, "functions.")
+						var args api.ToolCallFunctionArguments
+						if err := json.Unmarshal([]byte(toolContent), &args); err != nil {
+							ch <- gin.H{"error parsing tool call": err.Error()}
+							return
+						}
+
+						res.ToolCalls = append(res.ToolCalls, api.ToolCall{
+							Function: api.ToolCallFunction{
+								Name:      *toolName,
+								Arguments: args,
+							},
+						})
+					}
+				}
+
 				res.DoneReason = cr.DoneReason.String()
 				res.TotalDuration = time.Since(checkpointStart)
 				res.LoadDuration = checkpointLoaded.Sub(checkpointStart)
@@ -346,6 +391,15 @@ func (s *Server) GenerateHandler(c *gin.Context) {
 				}
 			}
 
+			if useHarmony {
+				// only send messages with meaningful content (empty messages confuse clients)
+				if res.Response != "" || res.Thinking != "" || res.Done || len(res.ToolCalls) > 0 {
+					ch <- res
+				}
+
+				return
+			}
+
 			ch <- res
 		}); err != nil {
 			ch <- gin.H{"error": err.Error()}
@@ -1476,7 +1530,7 @@ func (s *Server) ChatHandler(c *gin.Context) {
 	if len(req.Tools) > 0 {
 		caps = append(caps, model.CapabilityTools)
 	}
-	if req.Think != nil && *req.Think {
+	if req.Think != nil && req.Think.AsBool() {
 		caps = append(caps, model.CapabilityThinking)
 	}
 
@@ -1526,9 +1580,30 @@ func (s *Server) ChatHandler(c *gin.Context) {
 		return
 	}
 
+	useHarmony := shouldUseHarmony(*m)
+
+	// Validate Think value: string values currently only allowed for gptoss models
+	if req.Think != nil && req.Think.IsString() && !useHarmony {
+		c.JSON(http.StatusBadRequest, gin.H{"error": fmt.Sprintf("think value %q is not supported for this model", req.Think.AsString())})
+		return
+	}
+
+	var harmonyMessageHandler *HarmonyMessageHandler
+	var harmonyToolParser *HarmonyToolCallAccumulator
+
+	if useHarmony {
+		harmonyMessageHandler = NewHarmonyMessageHandler()
+		var lastMessage *api.Message
+		if len(msgs) > 0 {
+			lastMessage = &msgs[len(msgs)-1]
+		}
+		harmonyMessageHandler.harmonyParser.AddImplicitStartOrPrefill(lastMessage)
+		harmonyToolParser = harmonyMessageHandler.CreateToolParser()
+	}
+
 	var thinkingState *thinking.Parser
 	openingTag, closingTag := thinking.InferTags(m.Template.Template)
-	if req.Think != nil && *req.Think && openingTag != "" && closingTag != "" {
+	if req.Think != nil && req.Think.AsBool() && openingTag != "" && closingTag != "" {
 		thinkingState = &thinking.Parser{
 			OpeningTag: openingTag,
 			ClosingTag: closingTag,
@@ -1536,7 +1611,7 @@ func (s *Server) ChatHandler(c *gin.Context) {
 	}
 
 	var toolParser *tools.Parser
-	if len(req.Tools) > 0 {
+	if len(req.Tools) > 0 && !useHarmony {
 		toolParser = tools.NewParser(m.Template.Template, req.Tools)
 	}
 
@@ -1562,6 +1637,38 @@ func (s *Server) ChatHandler(c *gin.Context) {
 					EvalDuration:       r.EvalDuration,
 				},
 			}
+			if r.Done {
+				res.DoneReason = r.DoneReason.String()
+				res.TotalDuration = time.Since(checkpointStart)
+				res.LoadDuration = checkpointLoaded.Sub(checkpointStart)
+			}
+
+			if useHarmony {
+				content, thinking, toolContent := harmonyMessageHandler.AddContent(r.Content, harmonyToolParser)
+				res.Message.Content = content
+				res.Message.Thinking = thinking
+				harmonyToolParser.Add(toolContent)
+
+				if r.Done {
+					toolName, toolContent := harmonyToolParser.Drain()
+					if toolName != nil {
+						*toolName = strings.TrimPrefix(*toolName, "functions.")
+						var args api.ToolCallFunctionArguments
+						if err := json.Unmarshal([]byte(toolContent), &args); err != nil {
+							ch <- gin.H{"error parsing tool call": err.Error()}
+							return
+						}
+						res.Message.ToolCalls = []api.ToolCall{{Function: api.ToolCallFunction{Name: *toolName, Arguments: args}}}
+					}
+				}
+
+				// only send messages with meaningful content (empty messages confuse clients)
+				if res.Message.Content != "" || res.Message.Thinking != "" || len(res.Message.ToolCalls) > 0 || res.Done {
+					ch <- res
+				}
+
+				return
+			}
 
 			if thinkingState != nil {
 				thinkingContent, remainingContent := thinkingState.AddContent(res.Message.Content)
@@ -1573,12 +1680,6 @@ func (s *Server) ChatHandler(c *gin.Context) {
 				res.Message.Thinking = thinkingContent
 			}
 
-			if r.Done {
-				res.DoneReason = r.DoneReason.String()
-				res.TotalDuration = time.Since(checkpointStart)
-				res.LoadDuration = checkpointLoaded.Sub(checkpointStart)
-			}
-
 			if len(req.Tools) > 0 {
 				toolCalls, content := toolParser.Add(res.Message.Content)
 				if len(content) > 0 {

server/routes_generate_test.go

@@ -150,7 +150,7 @@ func TestGenerateChat(t *testing.T) {
 			Messages: []api.Message{
 				{Role: "user", Content: "Hello!"},
 			},
-			Think: &think,
+			Think: &api.ThinkValue{Value: think},
 		})
 
 		if w.Code != http.StatusBadRequest {

template/template.go

@@ -13,6 +13,7 @@ import (
 	"sync"
 	"text/template"
 	"text/template/parse"
+	"time"
 
 	"github.com/agnivade/levenshtein"
 
@@ -121,6 +122,11 @@ var funcs = template.FuncMap{
 		b, _ := json.Marshal(v)
 		return string(b)
 	},
+	"currentDate": func(args ...string) string {
+		// Currently ignoring the format argument, but accepting it for future use
+		// Default format is YYYY-MM-DD
+		return time.Now().Format("2006-01-02")
+	},
 }
 
 func Parse(s string) (*Template, error) {
@@ -160,12 +166,18 @@ func (t *Template) Vars() []string {
 	return slices.Sorted(maps.Keys(set))
 }
 
+func (t *Template) Contains(s string) bool {
+	return strings.Contains(t.raw, s)
+}
+
 type Values struct {
 	Messages []api.Message
 	api.Tools
 	Prompt string
 	Suffix string
 	Think  bool
+	// ThinkLevel contains the thinking level if Think is true and a string value was provided
+	ThinkLevel string
 	// whether or not the user explicitly set the thinking flag (vs. it being
 	// implicitly false). Templates can't see whether `Think` is nil
 	IsThinkSet bool
@@ -228,6 +240,7 @@ func (t *Template) Execute(w io.Writer, v Values) error {
 			"Suffix":     v.Suffix,
 			"Response":   "",
 			"Think":      v.Think,
+			"ThinkLevel": v.ThinkLevel,
 			"IsThinkSet": v.IsThinkSet,
 		})
 	} else if !v.forceLegacy && slices.Contains(t.Vars(), "messages") {
@@ -237,6 +250,7 @@ func (t *Template) Execute(w io.Writer, v Values) error {
 			"Tools":      v.Tools,
 			"Response":   "",
 			"Think":      v.Think,
+			"ThinkLevel": v.ThinkLevel,
 			"IsThinkSet": v.IsThinkSet,
 		})
 	}
@@ -251,6 +265,7 @@ func (t *Template) Execute(w io.Writer, v Values) error {
 				"Prompt":     prompt,
 				"Response":   response,
 				"Think":      v.Think,
+				"ThinkLevel": v.ThinkLevel,
 				"IsThinkSet": v.IsThinkSet,
 			}); err != nil {
 				return err
@@ -298,6 +313,7 @@ func (t *Template) Execute(w io.Writer, v Values) error {
 		"Prompt":     prompt,
 		"Response":   response,
 		"Think":      v.Think,
+		"ThinkLevel": v.ThinkLevel,
 		"IsThinkSet": v.IsThinkSet,
 	}); err != nil {
 		return err

tools/tools.go

@@ -26,6 +26,10 @@ type Parser struct {
 	n      int
 }
 
+func (p *Parser) GetBuffer() []byte {
+	return p.buffer
+}
+
 // NewParser creates a new tool call parser from a model's chat
 // template and a list of provided tools.
 func NewParser(tmpl *template.Template, tools []api.Tool) *Parser {