feat: improve OpenAI messages compatibility for Claude Code

backend/internal/service/openai_compat_prompt_cache_key.go

@@ -1,7 +1,9 @@
 package service
 
 import (
+	"crypto/sha256"
 	"encoding/json"
+	"fmt"
 	"strings"
 
 	"github.com/Wei-Shaw/sub2api/internal/pkg/apicompat"
@@ -16,12 +18,8 @@ func shouldAutoInjectPromptCacheKeyForCompat(model string) bool {
 	if !strings.Contains(trimmed, "gpt-5") && !strings.Contains(trimmed, "codex") {
 		return false
 	}
-	switch normalizeCodexModel(trimmed) {
-	case "gpt-5.4", "gpt-5.3-codex", "gpt-5.3-codex-spark":
-		return true
-	default:
-		return false
-	}
+	normalized := strings.TrimSpace(strings.ToLower(normalizeCodexModel(trimmed)))
+	return strings.HasPrefix(normalized, "gpt-5") || strings.Contains(normalized, "codex")
 }
 
 func deriveCompatPromptCacheKey(req *apicompat.ChatCompletionsRequest, mappedModel string) string {
@@ -71,6 +69,102 @@ func deriveCompatPromptCacheKey(req *apicompat.ChatCompletionsRequest, mappedMod
 	return compatPromptCacheKeyPrefix + hashSensitiveValueForLog(strings.Join(seedParts, "|"))
 }
 
+func deriveAnthropicCompatPromptCacheKey(req *apicompat.AnthropicRequest, mappedModel string) string {
+	if req == nil {
+		return ""
+	}
+	if anchorKey := deriveAnthropicCacheControlPromptCacheKey(req); anchorKey != "" {
+		return anchorKey
+	}
+
+	normalizedModel := normalizeCodexModel(strings.TrimSpace(mappedModel))
+	if normalizedModel == "" {
+		normalizedModel = normalizeCodexModel(strings.TrimSpace(req.Model))
+	}
+	if normalizedModel == "" {
+		normalizedModel = strings.TrimSpace(req.Model)
+	}
+
+	seedParts := []string{"model=" + normalizedModel}
+	if req.OutputConfig != nil && strings.TrimSpace(req.OutputConfig.Effort) != "" {
+		seedParts = append(seedParts, "effort="+strings.TrimSpace(req.OutputConfig.Effort))
+	}
+	if len(req.ToolChoice) > 0 {
+		seedParts = append(seedParts, "tool_choice="+normalizeCompatSeedJSON(req.ToolChoice))
+	}
+	if len(req.Tools) > 0 {
+		if raw, err := json.Marshal(req.Tools); err == nil {
+			seedParts = append(seedParts, "tools="+normalizeCompatSeedJSON(raw))
+		}
+	}
+	if len(req.System) > 0 {
+		seedParts = append(seedParts, "system="+normalizeCompatSeedJSON(req.System))
+	}
+
+	firstUserCaptured := false
+	for _, msg := range req.Messages {
+		if strings.TrimSpace(msg.Role) != "user" || firstUserCaptured {
+			continue
+		}
+		seedParts = append(seedParts, "first_user="+normalizeCompatSeedJSON(msg.Content))
+		firstUserCaptured = true
+	}
+
+	return compatPromptCacheKeyPrefix + hashSensitiveValueForLog(strings.Join(seedParts, "|"))
+}
+
+func deriveAnthropicCacheControlPromptCacheKey(req *apicompat.AnthropicRequest) string {
+	if req == nil {
+		return ""
+	}
+
+	var parts []string
+	var systemBlocks []apicompat.AnthropicContentBlock
+	if len(req.System) > 0 && json.Unmarshal(req.System, &systemBlocks) == nil {
+		for _, block := range systemBlocks {
+			if block.Type == "text" &&
+				block.CacheControl != nil &&
+				strings.TrimSpace(block.CacheControl.Type) == "ephemeral" &&
+				strings.TrimSpace(block.Text) != "" {
+				parts = append(parts, "system:"+strings.TrimSpace(block.Text))
+			}
+		}
+	}
+
+	firstUserAnchor := ""
+	for _, msg := range req.Messages {
+		var blocks []apicompat.AnthropicContentBlock
+		if len(msg.Content) == 0 || json.Unmarshal(msg.Content, &blocks) != nil {
+			continue
+		}
+		role := strings.TrimSpace(msg.Role)
+		for _, block := range blocks {
+			if block.Type != "text" ||
+				block.CacheControl == nil ||
+				strings.TrimSpace(block.CacheControl.Type) != "ephemeral" ||
+				strings.TrimSpace(block.Text) == "" {
+				continue
+			}
+			switch role {
+			case "user":
+				if firstUserAnchor == "" {
+					firstUserAnchor = strings.TrimSpace(block.Text)
+				}
+			case "assistant":
+				parts = append(parts, "assistant:"+strings.TrimSpace(block.Text))
+			}
+		}
+	}
+	if firstUserAnchor != "" {
+		parts = append(parts, "user_anchor:"+firstUserAnchor)
+	}
+	if len(parts) == 0 {
+		return ""
+	}
+	sum := sha256.Sum256([]byte("anthropic-cache:" + strings.Join(parts, "\n")))
+	return fmt.Sprintf("anthropic-cache-%x", sum[:16])
+}
+
 func normalizeCompatSeedJSON(v json.RawMessage) string {
 	if len(v) == 0 {
 		return ""