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Merged
jhaynie merged 2 commits into from
May 26, 2026
Merged

Normalize Anthropic system messages #19

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c0890b5
Normalize Anthropic system messages
jhaynie May 25, 2026
aedd784
Fix Anthropic system message edge cases
jhaynie May 26, 2026
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76 changes: 76 additions & 0 deletions autorouter.go
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Original file line number Diff line number Diff line change
Expand Up @@ -1001,12 +1001,88 @@ func normalizeProviderRequest(raw map[string]any, providerName string) {
const defaultAnthropicMaxTokens = 1024

func normalizeAnthropicRequest(raw map[string]any) {
normalizeAnthropicSystemMessages(raw)

if hasPositiveNumber(raw["max_tokens"]) {
return
}
raw["max_tokens"] = defaultAnthropicMaxTokens
}

func normalizeAnthropicSystemMessages(raw map[string]any) {
messages, ok := raw["messages"].([]any)
if !ok || len(messages) == 0 {
return
}

filtered := make([]any, 0, len(messages))
systemParts := make([]any, 0, 1)
for _, item := range messages {
message, ok := item.(map[string]any)
if !ok {
filtered = append(filtered, item)
continue
}
role, _ := message["role"].(string)
if role != "system" {
filtered = append(filtered, item)
continue
}
if content, exists := message["content"]; exists {
systemParts = append(systemParts, content)
}
}

raw["messages"] = filtered
if len(systemParts) > 0 {
raw["system"] = mergeAnthropicSystem(raw["system"], systemParts)
}
}

func mergeAnthropicSystem(existing any, systemParts []any) any {
systemText := joinTextParts(systemParts)
if existing == nil {
if systemText != "" {
return systemText
}
return systemParts[0]
}

existingText := joinTextParts([]any{existing})
if existingText != "" && systemText != "" {
return existingText + "\n\n" + systemText
}
if systemText != "" {
return systemText
}
return existing
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}

func joinTextParts(parts []any) string {
values := make([]string, 0, len(parts))
for _, part := range parts {
switch v := part.(type) {
case string:
if strings.TrimSpace(v) != "" {
values = append(values, v)
}
case []any:
for _, item := range v {
block, ok := item.(map[string]any)
if !ok {
continue
}
blockType, _ := block["type"].(string)
text, _ := block["text"].(string)
if blockType == "text" && strings.TrimSpace(text) != "" {
values = append(values, text)
}
}
}
}
return strings.Join(values, "\n\n")
}

func hasPositiveNumber(value any) bool {
switch v := value.(type) {
case int:
Expand Down
230 changes: 230 additions & 0 deletions autorouter_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -1506,6 +1506,236 @@ func TestAutoRouter_AnthropicPreservesMaxTokens(t *testing.T) {
}
}

func TestAutoRouter_AnthropicMovesSystemMessageToTopLevel(t *testing.T) {
var receivedBody map[string]any
upstream := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
body, _ := io.ReadAll(r.Body)
json.Unmarshal(body, &receivedBody)
w.Header().Set("Content-Type", "application/json")
w.WriteHeader(http.StatusOK)
w.Write([]byte(`{"id":"msg_test","type":"message","model":"claude-3-opus","content":[{"type":"text","text":"Hello"}],"usage":{"input_tokens":8,"output_tokens":1}}`))
}))
defer upstream.Close()

provider := &mockProvider{
name: "anthropic",
parseFn: func(body io.ReadCloser) (BodyMetadata, []byte, error) {
data, _ := io.ReadAll(body)
return BodyMetadata{Model: "claude-3-opus"}, data, nil
},
enrichFn: func(req *http.Request, meta BodyMetadata, body []byte) error { return nil },
resolveFn: func(meta BodyMetadata) (*url.URL, error) {
return url.Parse(upstream.URL)
},
extractFn: func(resp *http.Response) (ResponseMetadata, []byte, error) {
body, _ := io.ReadAll(resp.Body)
return ResponseMetadata{ID: "msg_test"}, body, nil
},
}

router := NewAutoRouter(
WithAutoRouterDetector(ProviderDetectorFunc(func(hint ProviderHint) string { return "anthropic" })),
)
router.RegisterProvider(provider)

req := httptest.NewRequestWithContext(context.Background(), "POST", "/", bytes.NewReader([]byte(`{"model":"claude-3-opus","messages":[{"role":"system","content":"You are terse."},{"role":"user","content":"Hello"}]}`)))
req.Header.Set("Content-Type", "application/json")
w := httptest.NewRecorder()

router.ServeHTTP(w, req)

if w.Code != http.StatusOK {
t.Fatalf("StatusCode = %d, want 200", w.Code)
}
if got := receivedBody["system"]; got != "You are terse." {
t.Fatalf("system = %v, want %q", got, "You are terse.")
}
messages, ok := receivedBody["messages"].([]any)
if !ok {
t.Fatalf("messages = %T, want []any", receivedBody["messages"])
}
if len(messages) != 1 {
t.Fatalf("len(messages) = %d, want 1", len(messages))
}
message, ok := messages[0].(map[string]any)
if !ok {
t.Fatalf("messages[0] = %T, want map[string]any", messages[0])
}
if got := message["role"]; got != "user" {
t.Fatalf("messages[0].role = %v, want user", got)
}
if got := receivedBody["max_tokens"]; got != float64(defaultAnthropicMaxTokens) {
t.Fatalf("max_tokens = %v, want %d", got, defaultAnthropicMaxTokens)
}
}

func TestAutoRouter_AnthropicMergesSystemMessageWithExistingSystem(t *testing.T) {
var receivedBody map[string]any
upstream := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
body, _ := io.ReadAll(r.Body)
json.Unmarshal(body, &receivedBody)
w.Header().Set("Content-Type", "application/json")
w.WriteHeader(http.StatusOK)
w.Write([]byte(`{"id":"msg_test","type":"message","model":"claude-3-opus","content":[{"type":"text","text":"Hello"}],"usage":{"input_tokens":8,"output_tokens":1}}`))
}))
defer upstream.Close()

provider := &mockProvider{
name: "anthropic",
parseFn: func(body io.ReadCloser) (BodyMetadata, []byte, error) {
data, _ := io.ReadAll(body)
return BodyMetadata{Model: "claude-3-opus"}, data, nil
},
enrichFn: func(req *http.Request, meta BodyMetadata, body []byte) error { return nil },
resolveFn: func(meta BodyMetadata) (*url.URL, error) {
return url.Parse(upstream.URL)
},
extractFn: func(resp *http.Response) (ResponseMetadata, []byte, error) {
body, _ := io.ReadAll(resp.Body)
return ResponseMetadata{ID: "msg_test"}, body, nil
},
}

router := NewAutoRouter(
WithAutoRouterDetector(ProviderDetectorFunc(func(hint ProviderHint) string { return "anthropic" })),
)
router.RegisterProvider(provider)

req := httptest.NewRequestWithContext(context.Background(), "POST", "/", bytes.NewReader([]byte(`{"model":"claude-3-opus","system":"Existing system.","messages":[{"role":"system","content":"Additional system."},{"role":"user","content":"Hello"}]}`)))
req.Header.Set("Content-Type", "application/json")
w := httptest.NewRecorder()

router.ServeHTTP(w, req)

if w.Code != http.StatusOK {
t.Fatalf("StatusCode = %d, want 200", w.Code)
}
if got := receivedBody["system"]; got != "Existing system.\n\nAdditional system." {
t.Fatalf("system = %v, want merged system", got)
}
messages, ok := receivedBody["messages"].([]any)
if !ok || len(messages) != 1 {
t.Fatalf("messages = %#v, want one non-system message", receivedBody["messages"])
}
}

func TestAutoRouter_AnthropicUsesSystemMessageWhenExistingSystemEmpty(t *testing.T) {
var receivedBody map[string]any
upstream := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
body, _ := io.ReadAll(r.Body)
json.Unmarshal(body, &receivedBody)
w.Header().Set("Content-Type", "application/json")
w.WriteHeader(http.StatusOK)
w.Write([]byte(`{"id":"msg_test","type":"message","model":"claude-3-opus","content":[{"type":"text","text":"Hello"}],"usage":{"input_tokens":8,"output_tokens":1}}`))
}))
defer upstream.Close()

provider := &mockProvider{
name: "anthropic",
parseFn: func(body io.ReadCloser) (BodyMetadata, []byte, error) {
data, _ := io.ReadAll(body)
return BodyMetadata{Model: "claude-3-opus"}, data, nil
},
enrichFn: func(req *http.Request, meta BodyMetadata, body []byte) error { return nil },
resolveFn: func(meta BodyMetadata) (*url.URL, error) {
return url.Parse(upstream.URL)
},
extractFn: func(resp *http.Response) (ResponseMetadata, []byte, error) {
body, _ := io.ReadAll(resp.Body)
return ResponseMetadata{ID: "msg_test"}, body, nil
},
}

router := NewAutoRouter(
WithAutoRouterDetector(ProviderDetectorFunc(func(hint ProviderHint) string { return "anthropic" })),
)
router.RegisterProvider(provider)

req := httptest.NewRequestWithContext(context.Background(), "POST", "/", bytes.NewReader([]byte(`{"model":"claude-3-opus","system":"","messages":[{"role":"system","content":"Use terse answers."},{"role":"user","content":"Hello"}]}`)))
req.Header.Set("Content-Type", "application/json")
w := httptest.NewRecorder()

router.ServeHTTP(w, req)

if w.Code != http.StatusOK {
t.Fatalf("StatusCode = %d, want 200", w.Code)
}
if got := receivedBody["system"]; got != "Use terse answers." {
t.Fatalf("system = %v, want %q", got, "Use terse answers.")
}
messages, ok := receivedBody["messages"].([]any)
if !ok || len(messages) != 1 {
t.Fatalf("messages = %#v, want one non-system message", receivedBody["messages"])
}
message, ok := messages[0].(map[string]any)
if !ok {
t.Fatalf("messages[0] = %T, want map[string]any", messages[0])
}
if got := message["role"]; got != "user" {
t.Fatalf("messages[0].role = %v, want user", got)
}
if got := receivedBody["max_tokens"]; got != float64(defaultAnthropicMaxTokens) {
t.Fatalf("max_tokens = %v, want %d", got, defaultAnthropicMaxTokens)
}
}

func TestAutoRouter_AnthropicRemovesSystemMessageWithMissingContent(t *testing.T) {
var receivedBody map[string]any
upstream := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
body, _ := io.ReadAll(r.Body)
json.Unmarshal(body, &receivedBody)
w.Header().Set("Content-Type", "application/json")
w.WriteHeader(http.StatusOK)
w.Write([]byte(`{"id":"msg_test","type":"message","model":"claude-3-opus","content":[{"type":"text","text":"Hello"}],"usage":{"input_tokens":8,"output_tokens":1}}`))
}))
defer upstream.Close()

provider := &mockProvider{
name: "anthropic",
parseFn: func(body io.ReadCloser) (BodyMetadata, []byte, error) {
data, _ := io.ReadAll(body)
return BodyMetadata{Model: "claude-3-opus"}, data, nil
},
enrichFn: func(req *http.Request, meta BodyMetadata, body []byte) error { return nil },
resolveFn: func(meta BodyMetadata) (*url.URL, error) {
return url.Parse(upstream.URL)
},
extractFn: func(resp *http.Response) (ResponseMetadata, []byte, error) {
body, _ := io.ReadAll(resp.Body)
return ResponseMetadata{ID: "msg_test"}, body, nil
},
}

router := NewAutoRouter(
WithAutoRouterDetector(ProviderDetectorFunc(func(hint ProviderHint) string { return "anthropic" })),
)
router.RegisterProvider(provider)

req := httptest.NewRequestWithContext(context.Background(), "POST", "/", bytes.NewReader([]byte(`{"model":"claude-3-opus","system":"Existing system.","messages":[{"role":"system"},{"role":"system","content":null},{"role":"user","content":"Hello"}]}`)))
req.Header.Set("Content-Type", "application/json")
w := httptest.NewRecorder()

router.ServeHTTP(w, req)

if w.Code != http.StatusOK {
t.Fatalf("StatusCode = %d, want 200", w.Code)
}
if got := receivedBody["system"]; got != "Existing system." {
t.Fatalf("system = %v, want existing system unchanged", got)
}
messages, ok := receivedBody["messages"].([]any)
if !ok || len(messages) != 1 {
t.Fatalf("messages = %#v, want one non-system message", receivedBody["messages"])
}
message, ok := messages[0].(map[string]any)
if !ok {
t.Fatalf("messages[0] = %T, want map[string]any", messages[0])
}
if got := message["role"]; got != "user" {
t.Fatalf("messages[0].role = %v, want user", got)
}
}

func TestAutoRouter_StreamingWritesGatewayMetadataEvent(t *testing.T) {
upstream := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
w.Header().Set("Content-Type", "text/event-stream")
Expand Down
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