strip out thinking tags in message history for qwen3 & r1 (#10490)

* strip out thinking tags in message history for qwen3 & r1

This is in advance of "proper" support where we'll make reasoning
configurable and we'll parse out thinking/reasoning tags and provide
them to the caller. These models expect there to be no thinking tags in
the message history, so this should improve quality

* parse model names instead of hacky prefix check

server/routes.go

@@ -18,6 +18,7 @@ import (
 	"os"
 	"os/signal"
 	"path/filepath"
+	"regexp"
 	"slices"
 	"strings"
 	"syscall"
@@ -1512,6 +1513,7 @@ func (s *Server) ChatHandler(c *gin.Context) {
 	if req.Messages[0].Role != "system" && m.System != "" {
 		msgs = append([]api.Message{{Role: "system", Content: m.System}}, msgs...)
 	}
+	msgs = filterThinkTags(msgs, m)
 
 	prompt, images, err := chatPrompt(c.Request.Context(), m, r.Tokenize, opts, msgs, req.Tools)
 	if err != nil {
@@ -1640,3 +1642,23 @@ func handleScheduleError(c *gin.Context, name string, err error) {
 		c.JSON(http.StatusInternalServerError, gin.H{"error": err.Error()})
 	}
 }
+
+var thinkTagRegexp = regexp.MustCompile(`<think>(?s).*?</think>(\n)*`)
+
+func filterThinkTags(msgs []api.Message, m *Model) []api.Message {
+	if m.Config.ModelFamily == "qwen3" || model.ParseName(m.Name).Model == "deepseek-r1" {
+		finalUserIndex := -1
+		for i, msg := range msgs {
+			if msg.Role == "user" {
+				finalUserIndex = i
+			}
+		}
+
+		for i, msg := range msgs {
+			if msg.Role == "assistant" && i < finalUserIndex {
+				msgs[i].Content = thinkTagRegexp.ReplaceAllString(msg.Content, "")
+			}
+		}
+	}
+	return msgs
+}

server/routes_test.go

@@ -15,6 +15,7 @@ import (
 	"net/http/httptest"
 	"os"
 	"path/filepath"
+	"reflect"
 	"sort"
 	"strings"
 	"testing"
@@ -746,3 +747,128 @@ func TestNormalize(t *testing.T) {
 		})
 	}
 }
+
+func TestFilterThinkTags(t *testing.T) {
+	type testCase struct {
+		msgs  []api.Message
+		want  []api.Message
+		model *Model
+	}
+	testCases := []testCase{
+		{
+			msgs: []api.Message{
+				{Role: "user", Content: "Hello, world!"},
+				{Role: "assistant", Content: "<think>Thinking... about the answer</think>abc"},
+				{Role: "user", Content: "What is the answer?"},
+			},
+			want: []api.Message{
+				{Role: "user", Content: "Hello, world!"},
+				{Role: "assistant", Content: "abc"},
+				{Role: "user", Content: "What is the answer?"},
+			},
+			model: &Model{
+				Config: ConfigV2{
+					ModelFamily: "qwen3",
+				},
+			},
+		},
+		// with newlines inside the think tag aned newlines after
+		{
+			msgs: []api.Message{
+				{Role: "user", Content: "Hello, world!"},
+				{Role: "assistant", Content: "<think>Thinking... \n\nabout \nthe answer</think>\n\nabc\ndef"},
+				{Role: "user", Content: "What is the answer?"},
+			},
+			want: []api.Message{
+				{Role: "user", Content: "Hello, world!"},
+				{Role: "assistant", Content: "abc\ndef"},
+				{Role: "user", Content: "What is the answer?"},
+			},
+			model: &Model{
+				Config: ConfigV2{
+					ModelFamily: "qwen3",
+				},
+			},
+		},
+		// should leave thinking tags if it's after the last user message
+		{
+			msgs: []api.Message{
+				{Role: "user", Content: "Hello, world!"},
+				{Role: "assistant", Content: "<think>Thinking...</think>after"},
+				{Role: "user", Content: "What is the answer?"},
+				{Role: "assistant", Content: "<think>thinking again</think>hjk"},
+				{Role: "assistant", Content: "<think>thinking yet again</think>hjk"},
+			},
+			want: []api.Message{
+				{Role: "user", Content: "Hello, world!"},
+				{Role: "assistant", Content: "after"},
+				{Role: "user", Content: "What is the answer?"},
+				{Role: "assistant", Content: "<think>thinking again</think>hjk"},
+				{Role: "assistant", Content: "<think>thinking yet again</think>hjk"},
+			},
+			model: &Model{
+				Config: ConfigV2{
+					ModelFamily: "qwen3",
+				},
+			},
+		},
+		{
+			// shouldn't strip anything because the model family isn't one of the hardcoded ones
+			msgs: []api.Message{
+				{Role: "user", Content: "Hello, world!"},
+				{Role: "assistant", Content: "<think>Thinking... about the answer</think>abc"},
+				{Role: "user", Content: "What is the answer?"},
+			},
+			want: []api.Message{
+				{Role: "user", Content: "Hello, world!"},
+				{Role: "assistant", Content: "<think>Thinking... about the answer</think>abc"},
+				{Role: "user", Content: "What is the answer?"},
+			},
+			model: &Model{
+				Config: ConfigV2{
+					ModelFamily: "llama3",
+				},
+			},
+		},
+		{
+			// deepseek-r1:-prefixed model
+			msgs: []api.Message{
+				{Role: "user", Content: "Hello, world!"},
+				{Role: "assistant", Content: "<think>Thinking... about the answer</think>abc"},
+				{Role: "user", Content: "What is the answer?"},
+			},
+			want: []api.Message{
+				{Role: "user", Content: "Hello, world!"},
+				{Role: "assistant", Content: "abc"},
+				{Role: "user", Content: "What is the answer?"},
+			},
+			model: &Model{
+				Name:      "registry.ollama.ai/library/deepseek-r1:latest",
+				ShortName: "deepseek-r1:7b",
+				Config:    ConfigV2{},
+			},
+		},
+	}
+
+	for i, tc := range testCases {
+		filtered := filterThinkTags(tc.msgs, tc.model)
+
+		if !reflect.DeepEqual(filtered, tc.want) {
+			t.Errorf("messages differ for case %d:", i)
+			for i := range tc.want {
+				if i >= len(filtered) {
+					t.Errorf("  missing message %d: %+v", i, tc.want[i])
+					continue
+				}
+				if !reflect.DeepEqual(filtered[i], tc.want[i]) {
+					t.Errorf("  message %d:\n    want: %+v\n    got:  %+v", i, tc.want[i], filtered[i])
+				}
+			}
+			if len(filtered) > len(tc.want) {
+				for i := len(tc.want); i < len(filtered); i++ {
+					t.Errorf("  extra message %d: %+v", i, filtered[i])
+				}
+			}
+		}
+	}
+}