Expose version/build metadata and improve provider error messaging

internal/openai/client.go

@@ -22,6 +22,55 @@ type Client struct {
 	httpClient *http.Client
 }
 
+type contentPart struct {
+	Type string `json:"type"`
+	Text string `json:"text"`
+}
+
+func extractRoleAndContent(raw json.RawMessage) (string, string) {
+	if len(raw) == 0 || string(raw) == "null" {
+		return "", ""
+	}
+
+	var envelope map[string]json.RawMessage
+	if err := json.Unmarshal(raw, &envelope); err != nil {
+		return "", ""
+	}
+
+	var role string
+	if value, ok := envelope["role"]; ok {
+		_ = json.Unmarshal(value, &role)
+	}
+
+	value, ok := envelope["content"]
+	if !ok {
+		return role, ""
+	}
+
+	var text string
+	if err := json.Unmarshal(value, &text); err == nil {
+		return role, text
+	}
+
+	var parts []contentPart
+	if err := json.Unmarshal(value, &parts); err == nil {
+		var builder strings.Builder
+		for _, part := range parts {
+			if part.Text != "" {
+				builder.WriteString(part.Text)
+			}
+		}
+		return role, builder.String()
+	}
+
+	var single contentPart
+	if err := json.Unmarshal(value, &single); err == nil {
+		return role, single.Text
+	}
+
+	return role, ""
+}
+
 // ClientOption customizes client construction.
 type ClientOption func(*Client)
 
@@ -131,10 +180,10 @@ func (c *Client) StreamChatCompletion(ctx context.Context, req ChatCompletionReq
 		ID      string `json:"id"`
 		Object  string `json:"object"`
 		Choices []struct {
-			Index        int         `json:"index"`
-			Message      ChatMessage `json:"message"`
-			Delta        ChatMessage `json:"delta"`
-			FinishReason string      `json:"finish_reason"`
+			Index        int             `json:"index"`
+			Message      json.RawMessage `json:"message"`
+			Delta        json.RawMessage `json:"delta"`
+			FinishReason string          `json:"finish_reason"`
 		} `json:"choices"`
 		Usage Usage `json:"usage"`
 	}
@@ -145,6 +194,7 @@ func (c *Client) StreamChatCompletion(ctx context.Context, req ChatCompletionReq
 	finish := ""
 	var usage Usage
 	usageReceived := false
+	var lastMessageText string
 
 	for scanner.Scan() {
 		line := scanner.Text()
@@ -190,19 +240,22 @@ func (c *Client) StreamChatCompletion(ctx context.Context, req ChatCompletionReq
 		finishReason := ""
 		if len(chunk.Choices) > 0 {
 			choice := chunk.Choices[0]
-			if choice.Message.Role != "" {
-				role = choice.Message.Role
+			choiceRole, choiceContent := extractRoleAndContent(choice.Message)
+			if choiceRole != "" {
+				role = choiceRole
 			}
-			if choice.Delta.Role != "" {
-				role = choice.Delta.Role
+			deltaRole, deltaContent := extractRoleAndContent(choice.Delta)
+			if deltaRole != "" {
+				role = deltaRole
 			}
-			if choice.Delta.Content != "" {
-				chunkText = choice.Delta.Content
-			} else if choice.Message.Content != "" && builder.Len() == 0 {
-				chunkText = choice.Message.Content
+			if deltaContent != "" {
+				chunkText = deltaContent
 			}
-			if choice.Message.Content != "" && builder.Len() == 0 && chunkText == "" {
-				chunkText = choice.Message.Content
+			if chunkText == "" && builder.Len() == 0 && choiceContent != "" {
+				chunkText = choiceContent
+			}
+			if choiceContent != "" {
+				lastMessageText = choiceContent
 			}
 			if choice.FinishReason != "" {
 				finishReason = choice.FinishReason
@@ -237,7 +290,23 @@ func (c *Client) StreamChatCompletion(ctx context.Context, req ChatCompletionReq
 
 	content := strings.TrimSpace(builder.String())
 	if content == "" {
-		return nil, errors.New("stream response contained no content")
+		if trimmed := strings.TrimSpace(lastMessageText); trimmed != "" {
+			content = trimmed
+		}
+	}
+	if content == "" {
+		aggregated.Choices = []ChatCompletionChoice{{
+			Index: 0,
+			Message: ChatMessage{
+				Role:    role,
+				Content: "",
+			},
+			FinishReason: finish,
+		}}
+		if usageReceived {
+			aggregated.Usage = usage
+		}
+		return &aggregated, nil
 	}
 
 	aggregated.Choices = []ChatCompletionChoice{{
@@ -280,8 +349,13 @@ func decodeSuccess(r io.Reader) (*ChatCompletionResponse, error) {
 func decodeError(r io.Reader, status int) error {
 	var apiErr ErrorResponse
 	if err := json.NewDecoder(r).Decode(&apiErr); err != nil {
-		return fmt.Errorf("api error (status %d): failed to decode body: %w", status, err)
+		return &RequestError{
+			Status: status,
+			Response: ErrorResponse{
+				Error: APIError{Message: fmt.Sprintf("failed to decode error body: %v", err)},
+			},
+		}
 	}
 
-	return fmt.Errorf("api error (status %d): %s", status, apiErr.Error.Message)
+	return &RequestError{Status: status, Response: apiErr}
 }

internal/openai/types.go

@@ -1,5 +1,10 @@
 package openai
 
+import (
+	"fmt"
+	"strings"
+)
+
 // ChatMessage represents a single message within a chat completion request or response.
 type ChatMessage struct {
 	Role    string `json:"role"`
@@ -50,6 +55,48 @@ type ChatCompletionStreamEvent struct {
 // ChatCompletionStreamHandler consumes streaming completion events.
 type ChatCompletionStreamHandler func(ChatCompletionStreamEvent) error
 
+// RequestError captures an error response returned by the API together with the HTTP status code.
+type RequestError struct {
+	Status   int
+	Response ErrorResponse
+}
+
+// Error implements the error interface.
+func (e *RequestError) Error() string {
+	if e == nil {
+		return ""
+	}
+	msg := strings.TrimSpace(e.Response.Error.Message)
+	if msg == "" {
+		return fmt.Sprintf("api error (status %d)", e.Status)
+	}
+	return fmt.Sprintf("api error (status %d): %s", e.Status, msg)
+}
+
+// StatusCode returns the originating HTTP status code.
+func (e *RequestError) StatusCode() int {
+	if e == nil {
+		return 0
+	}
+	return e.Status
+}
+
+// Message returns the raw message provided by the API, if any.
+func (e *RequestError) Message() string {
+	if e == nil {
+		return ""
+	}
+	return e.Response.Error.Message
+}
+
+// Type returns the OpenAI error type string, when present.
+func (e *RequestError) Type() string {
+	if e == nil {
+		return ""
+	}
+	return e.Response.Error.Type
+}
+
 // APIError captures structured error responses returned by the API.
 type APIError struct {
 	Message string `json:"message"`