diff --git a/internal/auth/claude/anthropic_auth.go b/internal/auth/claude/anthropic_auth.go
index e0f6e3c8..2853e418 100644
--- a/internal/auth/claude/anthropic_auth.go
+++ b/internal/auth/claude/anthropic_auth.go
@@ -20,7 +20,7 @@ import (
 // OAuth configuration constants for Claude/Anthropic
 const (
 	AuthURL     = "https://claude.ai/oauth/authorize"
-	TokenURL    = "https://console.anthropic.com/v1/oauth/token"
+	TokenURL    = "https://api.anthropic.com/v1/oauth/token"
 	ClientID    = "9d1c250a-e61b-44d9-88ed-5944d1962f5e"
 	RedirectURI = "http://localhost:54545/callback"
 )
diff --git a/internal/registry/model_definitions_static_data.go b/internal/registry/model_definitions_static_data.go
index 52a559f9..3252a7fb 100644
--- a/internal/registry/model_definitions_static_data.go
+++ b/internal/registry/model_definitions_static_data.go
@@ -306,6 +306,21 @@ func GetGeminiVertexModels() []*ModelInfo {
 			SupportedGenerationMethods: []string{"generateContent", "countTokens", "createCachedContent", "batchGenerateContent"},
 			Thinking:                   &ThinkingSupport{Min: 128, Max: 32768, ZeroAllowed: false, DynamicAllowed: true, Levels: []string{"minimal", "low", "medium", "high"}},
 		},
+		{
+			ID:                         "gemini-3.1-pro-preview",
+			Object:                     "model",
+			Created:                    1771491385,
+			OwnedBy:                    "google",
+			Type:                       "gemini",
+			Name:                       "models/gemini-3.1-pro-preview",
+			Version:                    "3.1",
+			DisplayName:                "Gemini 3.1 Pro Preview",
+			Description:                "Gemini 3.1 Pro Preview",
+			InputTokenLimit:            1048576,
+			OutputTokenLimit:           65536,
+			SupportedGenerationMethods: []string{"generateContent", "countTokens", "createCachedContent", "batchGenerateContent"},
+			Thinking:                   &ThinkingSupport{Min: 1, Max: 32768, ZeroAllowed: false, DynamicAllowed: true, Levels: []string{"low", "high"}},
+		},
 		{
 			ID:                         "gemini-3-pro-image-preview",
 			Object:                     "model",
diff --git a/internal/translator/codex/claude/codex_claude_response.go b/internal/translator/codex/claude/codex_claude_response.go
index b39494b7..cdcf2e4f 100644
--- a/internal/translator/codex/claude/codex_claude_response.go
+++ b/internal/translator/codex/claude/codex_claude_response.go
@@ -22,8 +22,9 @@ var (
 
 // ConvertCodexResponseToClaudeParams holds parameters for response conversion.
 type ConvertCodexResponseToClaudeParams struct {
-	HasToolCall bool
-	BlockIndex  int
+	HasToolCall              bool
+	BlockIndex               int
+	HasReceivedArgumentsDelta bool
 }
 
 // ConvertCodexResponseToClaude performs sophisticated streaming response format conversion.
@@ -137,6 +138,7 @@ func ConvertCodexResponseToClaude(_ context.Context, _ string, originalRequestRa
 		itemType := itemResult.Get("type").String()
 		if itemType == "function_call" {
 			(*param).(*ConvertCodexResponseToClaudeParams).HasToolCall = true
+			(*param).(*ConvertCodexResponseToClaudeParams).HasReceivedArgumentsDelta = false
 			template = `{"type":"content_block_start","index":0,"content_block":{"type":"tool_use","id":"","name":"","input":{}}}`
 			template, _ = sjson.Set(template, "index", (*param).(*ConvertCodexResponseToClaudeParams).BlockIndex)
 			template, _ = sjson.Set(template, "content_block.id", itemResult.Get("call_id").String())
@@ -171,12 +173,29 @@ func ConvertCodexResponseToClaude(_ context.Context, _ string, originalRequestRa
 			output += fmt.Sprintf("data: %s\n\n", template)
 		}
 	} else if typeStr == "response.function_call_arguments.delta" {
+		(*param).(*ConvertCodexResponseToClaudeParams).HasReceivedArgumentsDelta = true
 		template = `{"type":"content_block_delta","index":0,"delta":{"type":"input_json_delta","partial_json":""}}`
 		template, _ = sjson.Set(template, "index", (*param).(*ConvertCodexResponseToClaudeParams).BlockIndex)
 		template, _ = sjson.Set(template, "delta.partial_json", rootResult.Get("delta").String())
 
 		output += "event: content_block_delta\n"
 		output += fmt.Sprintf("data: %s\n\n", template)
+	} else if typeStr == "response.function_call_arguments.done" {
+		// Some models (e.g. gpt-5.3-codex-spark) send function call arguments
+		// in a single "done" event without preceding "delta" events.
+		// Emit the full arguments as a single input_json_delta so the
+		// downstream Claude client receives the complete tool input.
+		// When delta events were already received, skip to avoid duplicating arguments.
+		if !(*param).(*ConvertCodexResponseToClaudeParams).HasReceivedArgumentsDelta {
+			if args := rootResult.Get("arguments").String(); args != "" {
+				template = `{"type":"content_block_delta","index":0,"delta":{"type":"input_json_delta","partial_json":""}}`
+				template, _ = sjson.Set(template, "index", (*param).(*ConvertCodexResponseToClaudeParams).BlockIndex)
+				template, _ = sjson.Set(template, "delta.partial_json", args)
+
+				output += "event: content_block_delta\n"
+				output += fmt.Sprintf("data: %s\n\n", template)
+			}
+		}
 	}
 
 	return []string{output}