bugfix: fix crash bug in token cache logic

This change fixes a problem in the token cache logic to avoid panics caused by empty token arrays
by ensuring at least one token remains on full cache hits in the relevant function. The happens
if there is an exact match in the cache on subsequent generations.

model/parsers/glm46.go

@@ -32,10 +32,9 @@ const (
 )
 
 type GLM46Parser struct {
-	state     glm46ParserState
-	buffer    strings.Builder
-	tools     []api.Tool
-	callIndex int
+	state  glm46ParserState
+	buffer strings.Builder
+	tools  []api.Tool
 }
 
 func (p *GLM46Parser) HasToolSupport() bool {
@@ -49,7 +48,6 @@ func (p *GLM46Parser) HasThinkingSupport() bool {
 // func (p *GLM46Parser) Init(tools []api.Tool, lastMessage *api.Message) []api.Tool {
 func (p *GLM46Parser) Init(tools []api.Tool, lastMessage *api.Message, thinkValue *api.ThinkValue) []api.Tool {
 	p.tools = tools
-	p.callIndex = 0
 	return tools
 }
 
@@ -91,8 +89,6 @@ func (p *GLM46Parser) Add(s string, done bool) (content string, thinking string,
 				slog.Warn("glm-4.6 tool call parsing failed", "error", err)
 				return "", "", nil, err
 			}
-			toolCall.Function.Index = p.callIndex
-			p.callIndex++
 			toolCalls = append(toolCalls, toolCall)
 		case glm46EventThinkingContent:
 			thinkingSb.WriteString(event.content)

model/parsers/glm47.go

@@ -11,7 +11,6 @@ type GLM47Parser struct {
 
 func (p *GLM47Parser) Init(tools []api.Tool, lastMessage *api.Message, thinkValue *api.ThinkValue) []api.Tool {
 	p.tools = tools
-	p.callIndex = 0
 	// When thinking is enabled (nil or true), the prompt ends with <think>,
 	// so model output starts directly with thinking content (no opening tag).
 	if thinkValue == nil || thinkValue.Bool() {

model/parsers/glm47_test.go

@@ -97,91 +97,3 @@ func TestGLM47ParserToolCallEscaping(t *testing.T) {
 		t.Fatalf("expected %#v, got %#v", expected, toolCall)
 	}
 }
-
-func TestGLM47ParserToolCallIndexing(t *testing.T) {
-	parser := GLM47Parser{}
-	parser.Init(nil, nil, nil)
-
-	input := `plan</think>
-<tool_call>first<arg_key>a</arg_key><arg_value>1</arg_value></tool_call>
-<tool_call>second<arg_key>b</arg_key><arg_value>2</arg_value></tool_call>
-<tool_call>third<arg_key>c</arg_key><arg_value>3</arg_value></tool_call>`
-
-	_, _, calls, err := parser.Add(input, true)
-	if err != nil {
-		t.Fatalf("parse failed: %v", err)
-	}
-
-	want := []api.ToolCall{
-		{Function: api.ToolCallFunction{Name: "first", Arguments: args(`{"a":"1"}`), Index: 0}},
-		{Function: api.ToolCallFunction{Name: "second", Arguments: args(`{"b":"2"}`), Index: 1}},
-		{Function: api.ToolCallFunction{Name: "third", Arguments: args(`{"c":"3"}`), Index: 2}},
-	}
-	if len(calls) != len(want) {
-		t.Fatalf("expected %d calls, got %d", len(want), len(calls))
-	}
-	for i := range want {
-		if !toolCallEqual(calls[i], want[i]) {
-			t.Fatalf("call %d mismatch: got %#v, want %#v", i, calls[i], want[i])
-		}
-	}
-}
-
-func TestGLM47ParserToolCallIndexingStreaming(t *testing.T) {
-	parser := GLM47Parser{}
-	parser.Init(nil, nil, nil)
-
-	var all []api.ToolCall
-
-	_, _, calls, err := parser.Add("plan</think><tool_call>first<arg_key>a</arg_key><arg_value>1</arg_value></tool_call><tool_call>second<arg_key>b</arg_key>", false)
-	if err != nil {
-		t.Fatalf("step 1 parse failed: %v", err)
-	}
-	all = append(all, calls...)
-
-	_, _, calls, err = parser.Add("<arg_value>2</arg_value></tool_call><tool_call>third<arg_key>c</arg_key><arg_value>3</arg_value></tool_call>", true)
-	if err != nil {
-		t.Fatalf("step 2 parse failed: %v", err)
-	}
-	all = append(all, calls...)
-
-	want := []api.ToolCall{
-		{Function: api.ToolCallFunction{Name: "first", Arguments: args(`{"a":"1"}`), Index: 0}},
-		{Function: api.ToolCallFunction{Name: "second", Arguments: args(`{"b":"2"}`), Index: 1}},
-		{Function: api.ToolCallFunction{Name: "third", Arguments: args(`{"c":"3"}`), Index: 2}},
-	}
-	if len(all) != len(want) {
-		t.Fatalf("expected %d calls, got %d", len(want), len(all))
-	}
-	for i := range want {
-		if !toolCallEqual(all[i], want[i]) {
-			t.Fatalf("call %d mismatch: got %#v, want %#v", i, all[i], want[i])
-		}
-	}
-}
-
-func TestGLM47ParserToolCallIndexResetOnInit(t *testing.T) {
-	parser := GLM47Parser{}
-	parser.Init(nil, nil, nil)
-
-	_, _, _, err := parser.Add("plan</think><tool_call>first<arg_key>a</arg_key><arg_value>1</arg_value></tool_call>", true)
-	if err != nil {
-		t.Fatalf("first parse failed: %v", err)
-	}
-
-	parser.Init(nil, nil, nil)
-	_, _, calls, err := parser.Add("plan</think><tool_call>second<arg_key>b</arg_key><arg_value>2</arg_value></tool_call>", true)
-	if err != nil {
-		t.Fatalf("second parse failed: %v", err)
-	}
-
-	want := api.ToolCall{
-		Function: api.ToolCallFunction{Name: "second", Arguments: args(`{"b":"2"}`), Index: 0},
-	}
-	if len(calls) != 1 {
-		t.Fatalf("expected 1 call, got %d", len(calls))
-	}
-	if !toolCallEqual(calls[0], want) {
-		t.Fatalf("got %#v, want %#v", calls[0], want)
-	}
-}

model/parsers/qwen3.go

@@ -38,7 +38,6 @@ type Qwen3Parser struct {
 	state                  qwen3ParserState
 	buffer                 strings.Builder
 	tools                  []api.Tool
-	callIndex              int
 	hasThinkingSupport     bool
 	defaultThinking        bool
 	maybeThinkingOpenAtBOL bool
@@ -55,7 +54,6 @@ func (p *Qwen3Parser) HasThinkingSupport() bool {
 func (p *Qwen3Parser) Init(tools []api.Tool, lastMessage *api.Message, thinkValue *api.ThinkValue) []api.Tool {
 	p.tools = tools
 	p.buffer.Reset()
-	p.callIndex = 0
 
 	thinkingEnabled := thinkValue != nil && thinkValue.Bool()
 	if thinkValue == nil {
@@ -108,8 +106,6 @@ func (p *Qwen3Parser) Add(s string, done bool) (content string, thinking string,
 				slog.Warn("qwen3 tool call parsing failed", "error", err)
 				return "", "", nil, err
 			}
-			toolCall.Function.Index = p.callIndex
-			p.callIndex++
 			calls = append(calls, toolCall)
 		case qwen3EventThinkingContent:
 			thinkingSb.WriteString(event.content)

model/parsers/qwen3_test.go

@@ -230,89 +230,3 @@ func TestQwen35ParserRespectsNoThink(t *testing.T) {
 		t.Fatalf("expected no tool calls, got %d", len(calls))
 	}
 }
-
-func TestQwen3ParserToolCallIndexing(t *testing.T) {
-	parser := &Qwen3Parser{hasThinkingSupport: false, defaultThinking: false}
-	parser.Init(nil, nil, &api.ThinkValue{Value: false})
-
-	input := `<tool_call>{"name":"first","arguments":{"a":"1"}}</tool_call>
-<tool_call>{"name":"second","arguments":{"b":"2"}}</tool_call>
-<tool_call>{"name":"third","arguments":{"c":"3"}}</tool_call>`
-	_, _, calls, err := parser.Add(input, true)
-	if err != nil {
-		t.Fatalf("parse failed: %v", err)
-	}
-
-	want := []api.ToolCall{
-		{Function: api.ToolCallFunction{Name: "first", Arguments: args(`{"a":"1"}`), Index: 0}},
-		{Function: api.ToolCallFunction{Name: "second", Arguments: args(`{"b":"2"}`), Index: 1}},
-		{Function: api.ToolCallFunction{Name: "third", Arguments: args(`{"c":"3"}`), Index: 2}},
-	}
-	if len(calls) != len(want) {
-		t.Fatalf("expected %d calls, got %d", len(want), len(calls))
-	}
-	for i := range want {
-		if !toolCallEqual(calls[i], want[i]) {
-			t.Fatalf("call %d mismatch: got %#v, want %#v", i, calls[i], want[i])
-		}
-	}
-}
-
-func TestQwen3ParserToolCallIndexingStreaming(t *testing.T) {
-	parser := &Qwen3Parser{hasThinkingSupport: false, defaultThinking: false}
-	parser.Init(nil, nil, &api.ThinkValue{Value: false})
-
-	var all []api.ToolCall
-
-	_, _, calls, err := parser.Add(`<tool_call>{"name":"first","arguments":{"a":"1"}}</tool_call><tool_call>{"name":"second","arguments":{"b":"2"}`, false)
-	if err != nil {
-		t.Fatalf("step 1 parse failed: %v", err)
-	}
-	all = append(all, calls...)
-
-	_, _, calls, err = parser.Add(`}</tool_call><tool_call>{"name":"third","arguments":{"c":"3"}}</tool_call>`, true)
-	if err != nil {
-		t.Fatalf("step 2 parse failed: %v", err)
-	}
-	all = append(all, calls...)
-
-	want := []api.ToolCall{
-		{Function: api.ToolCallFunction{Name: "first", Arguments: args(`{"a":"1"}`), Index: 0}},
-		{Function: api.ToolCallFunction{Name: "second", Arguments: args(`{"b":"2"}`), Index: 1}},
-		{Function: api.ToolCallFunction{Name: "third", Arguments: args(`{"c":"3"}`), Index: 2}},
-	}
-	if len(all) != len(want) {
-		t.Fatalf("expected %d calls, got %d", len(want), len(all))
-	}
-	for i := range want {
-		if !toolCallEqual(all[i], want[i]) {
-			t.Fatalf("call %d mismatch: got %#v, want %#v", i, all[i], want[i])
-		}
-	}
-}
-
-func TestQwen3ParserToolCallIndexResetOnInit(t *testing.T) {
-	parser := &Qwen3Parser{hasThinkingSupport: false, defaultThinking: false}
-	parser.Init(nil, nil, &api.ThinkValue{Value: false})
-
-	_, _, _, err := parser.Add(`<tool_call>{"name":"first","arguments":{"a":"1"}}</tool_call>`, true)
-	if err != nil {
-		t.Fatalf("first parse failed: %v", err)
-	}
-
-	parser.Init(nil, nil, &api.ThinkValue{Value: false})
-	_, _, calls, err := parser.Add(`<tool_call>{"name":"second","arguments":{"b":"2"}}</tool_call>`, true)
-	if err != nil {
-		t.Fatalf("second parse failed: %v", err)
-	}
-
-	want := api.ToolCall{
-		Function: api.ToolCallFunction{Name: "second", Arguments: args(`{"b":"2"}`), Index: 0},
-	}
-	if len(calls) != 1 {
-		t.Fatalf("expected 1 call, got %d", len(calls))
-	}
-	if !toolCallEqual(calls[0], want) {
-		t.Fatalf("got %#v, want %#v", calls[0], want)
-	}
-}

model/parsers/qwen3coder.go

@@ -29,10 +29,9 @@ const (
 )
 
 type Qwen3CoderParser struct {
-	state     qwenParserState
-	acc       strings.Builder
-	tools     []api.Tool
-	callIndex int
+	state qwenParserState
+	acc   strings.Builder
+	tools []api.Tool
 }
 
 func (p *Qwen3CoderParser) HasToolSupport() bool {
@@ -45,7 +44,6 @@ func (p *Qwen3CoderParser) HasThinkingSupport() bool {
 
 func (p *Qwen3CoderParser) Init(tools []api.Tool, lastMessage *api.Message, thinkValue *api.ThinkValue) []api.Tool {
 	p.tools = tools
-	p.callIndex = 0
 	return tools // Qwen doesn't modify tools
 }
 
@@ -64,8 +62,6 @@ func (p *Qwen3CoderParser) Add(s string, done bool) (content string, thinking st
 				slog.Warn("qwen tool call parsing failed", "error", err)
 				return "", "", nil, err
 			}
-			toolCall.Function.Index = p.callIndex
-			p.callIndex++
 			toolCalls = append(toolCalls, toolCall)
 		case qwenEventContent:
 			// TODO(drifkin): if the same turn contains multiple interleaved content

model/parsers/qwen3coder_test.go

@@ -1035,92 +1035,6 @@ func TestQwenToolCallValueParsing(t *testing.T) {
 	}
 }
 
-func TestQwen3CoderParserToolCallIndexing(t *testing.T) {
-	parser := Qwen3CoderParser{}
-	parser.Init(nil, nil, nil)
-
-	input := `<tool_call><function=first><parameter=a>1</parameter></function></tool_call>
-<tool_call><function=second><parameter=b>2</parameter></function></tool_call>
-<tool_call><function=third><parameter=c>3</parameter></function></tool_call>`
-	_, _, calls, err := parser.Add(input, true)
-	if err != nil {
-		t.Fatalf("parse failed: %v", err)
-	}
-
-	want := []api.ToolCall{
-		{Function: api.ToolCallFunction{Name: "first", Arguments: testArgs(map[string]any{"a": "1"}), Index: 0}},
-		{Function: api.ToolCallFunction{Name: "second", Arguments: testArgs(map[string]any{"b": "2"}), Index: 1}},
-		{Function: api.ToolCallFunction{Name: "third", Arguments: testArgs(map[string]any{"c": "3"}), Index: 2}},
-	}
-	if len(calls) != len(want) {
-		t.Fatalf("expected %d calls, got %d", len(want), len(calls))
-	}
-	for i := range want {
-		if !toolCallEqual(calls[i], want[i]) {
-			t.Fatalf("call %d mismatch: got %#v, want %#v", i, calls[i], want[i])
-		}
-	}
-}
-
-func TestQwen3CoderParserToolCallIndexingStreaming(t *testing.T) {
-	parser := Qwen3CoderParser{}
-	parser.Init(nil, nil, nil)
-
-	var all []api.ToolCall
-
-	_, _, calls, err := parser.Add("<tool_call><function=first><parameter=a>1</parameter></function></tool_call><tool_call><function=second>", false)
-	if err != nil {
-		t.Fatalf("step 1 parse failed: %v", err)
-	}
-	all = append(all, calls...)
-
-	_, _, calls, err = parser.Add("<parameter=b>2</parameter></function></tool_call><tool_call><function=third><parameter=c>3</parameter></function></tool_call>", true)
-	if err != nil {
-		t.Fatalf("step 2 parse failed: %v", err)
-	}
-	all = append(all, calls...)
-
-	want := []api.ToolCall{
-		{Function: api.ToolCallFunction{Name: "first", Arguments: testArgs(map[string]any{"a": "1"}), Index: 0}},
-		{Function: api.ToolCallFunction{Name: "second", Arguments: testArgs(map[string]any{"b": "2"}), Index: 1}},
-		{Function: api.ToolCallFunction{Name: "third", Arguments: testArgs(map[string]any{"c": "3"}), Index: 2}},
-	}
-	if len(all) != len(want) {
-		t.Fatalf("expected %d calls, got %d", len(want), len(all))
-	}
-	for i := range want {
-		if !toolCallEqual(all[i], want[i]) {
-			t.Fatalf("call %d mismatch: got %#v, want %#v", i, all[i], want[i])
-		}
-	}
-}
-
-func TestQwen3CoderParserToolCallIndexResetOnInit(t *testing.T) {
-	parser := Qwen3CoderParser{}
-	parser.Init(nil, nil, nil)
-
-	_, _, _, err := parser.Add("<tool_call><function=first><parameter=a>1</parameter></function></tool_call>", true)
-	if err != nil {
-		t.Fatalf("first parse failed: %v", err)
-	}
-
-	parser.Init(nil, nil, nil)
-	_, _, calls, err := parser.Add("<tool_call><function=second><parameter=b>2</parameter></function></tool_call>", true)
-	if err != nil {
-		t.Fatalf("second parse failed: %v", err)
-	}
-
-	want := api.ToolCall{
-		Function: api.ToolCallFunction{Name: "second", Arguments: testArgs(map[string]any{"b": "2"}), Index: 0},
-	}
-	if len(calls) != 1 {
-		t.Fatalf("expected 1 call, got %d", len(calls))
-	}
-	if !toolCallEqual(calls[0], want) {
-		t.Fatalf("got %#v, want %#v", calls[0], want)
-	}
-}
-
 func TestQwenXMLTransform(t *testing.T) {
 	cases := []struct {
 		desc string

x/mlxrunner/cache.go

@@ -78,6 +78,11 @@ func (c *kvCache) findRemaining(tokens []int32) []int32 {
 		prefix++
 	}
 
+	if prefix == len(tokens) && prefix > 0 {
+		// Leave one token to run through the model so we can sample a response.
+		prefix--
+	}
+
 	if prefix < len(c.tokens) {
 		trim := len(c.tokens) - prefix
 		for _, kv := range c.caches {