fix(adapters): forward extra_body params and return reasoning_content properly (#75)

* fix(adapters): forward extra_body params and return reasoning_content properly

Request adapters had a KNOWN_FIELDS set that excluded recognized fields
(e.g. response_format, presence_penalty, seed) from extraParams passthrough,
but those fields were never mapped in parse() either — causing them to be
silently dropped when forwarding to upstream providers. Rename to MAPPED_FIELDS
containing only fields actually consumed by parse(), so all other fields
flow through extraParams to the upstream provider.

The response adapter for OpenAI Chat wrapped reasoning_content in <think>
tags inside the content field. This was originally only used for DB logging,
but was incorrectly carried over into client response serialization during
the adapter refactor (09a0ce9). Restore the original behavior: return
reasoning_content as a separate field for client responses, keep <think>
wrapping only for database storage.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* refactor: combine extractTextContent and extractReasoningContent into single pass

Merge two separate functions that iterated over the same content blocks
array into a single extractContent() function that returns both text and
reasoning in one pass.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

Author: pescn

backend/src/adapters/request/anthropic.ts

@@ -70,10 +70,12 @@ interface AnthropicRequest {
 }
 
 // =============================================================================
-// Known Fields (for extracting extra body)
+// Mapped Fields (fields explicitly extracted by parse(), excluded from extraParams)
+// All other fields (e.g. metadata) are passed through via extraParams
+// to the upstream provider.
 // =============================================================================
 
-const KNOWN_FIELDS = new Set([
+const MAPPED_FIELDS = new Set([
   "model",
   "messages",
   "system",
@@ -85,7 +87,6 @@ const KNOWN_FIELDS = new Set([
   "stop_sequences",
   "tools",
   "tool_choice",
-  "metadata",
 ]);
 
 // =============================================================================
@@ -343,7 +344,7 @@ export const anthropicRequestAdapter: RequestAdapter<AnthropicRequest> = {
     let hasExtra = false;
 
     for (const [key, value] of Object.entries(body)) {
-      if (!KNOWN_FIELDS.has(key)) {
+      if (!MAPPED_FIELDS.has(key)) {
         extra[key] = value;
         hasExtra = true;
       }

backend/src/adapters/request/openai-chat.ts

@@ -112,30 +112,22 @@ interface OpenAIChatRequest {
 }
 
 // =============================================================================
-// Known Fields (for extracting extra body)
+// Mapped Fields (fields explicitly extracted by parse(), excluded from extraParams)
+// All other fields (e.g. response_format, presence_penalty, seed, etc.)
+// are passed through via extraParams to the upstream provider.
 // =============================================================================
 
-const KNOWN_FIELDS = new Set([
+const MAPPED_FIELDS = new Set([
   "model",
   "messages",
   "max_tokens",
   "max_completion_tokens",
   "temperature",
   "top_p",
-  "n",
   "stream",
-  "stream_options",
   "stop",
   "tools",
   "tool_choice",
-  "presence_penalty",
-  "frequency_penalty",
-  "logit_bias",
-  "logprobs",
-  "top_logprobs",
-  "user",
-  "seed",
-  "response_format",
 ]);
 
 // =============================================================================
@@ -340,7 +332,7 @@ export const openaiChatRequestAdapter: RequestAdapter<OpenAIChatRequest> = {
     let hasExtra = false;
 
     for (const [key, value] of Object.entries(body)) {
-      if (!KNOWN_FIELDS.has(key)) {
+      if (!MAPPED_FIELDS.has(key)) {
         extra[key] = value;
         hasExtra = true;
       }

backend/src/adapters/request/openai-response.ts

@@ -109,24 +109,21 @@ interface ResponseApiRequest {
 }
 
 // =============================================================================
-// Known Fields (for extracting extra body)
+// Mapped Fields (fields explicitly extracted by parse(), excluded from extraParams)
+// All other fields (e.g. modalities, parallel_tool_calls, store, metadata, etc.)
+// are passed through via extraParams to the upstream provider.
 // =============================================================================
 
-const KNOWN_FIELDS = new Set([
+const MAPPED_FIELDS = new Set([
   "model",
   "input",
   "instructions",
-  "modalities",
   "max_output_tokens",
   "temperature",
   "top_p",
   "stream",
   "tools",
   "tool_choice",
-  "parallel_tool_calls",
-  "previous_response_id",
-  "store",
-  "metadata",
 ]);
 
 // =============================================================================
@@ -298,7 +295,7 @@ export const openaiResponseRequestAdapter: RequestAdapter<ResponseApiRequest> =
       let hasExtra = false;
 
       for (const [key, value] of Object.entries(body)) {
-        if (!KNOWN_FIELDS.has(key)) {
+        if (!MAPPED_FIELDS.has(key)) {
           extra[key] = value;
           hasExtra = true;
         }

backend/src/adapters/response/openai-chat.ts

@@ -35,6 +35,7 @@ interface OpenAIChatChoice {
 interface OpenAIChatMessage {
   role: "assistant";
   content: string | null;
+  reasoning_content?: string | null;
   tool_calls?: OpenAIToolCall[];
   refusal?: string | null;
 }
@@ -113,9 +114,11 @@ function convertStopReason(stopReason: StopReason): string | null {
 }
 
 /**
- * Extract text content from internal content blocks
+ * Extract text and reasoning content from internal content blocks
  */
-function extractTextContent(content: InternalContentBlock[]): string {
+function extractContent(
+  content: InternalContentBlock[],
+): { text: string; reasoning?: string } {
   const textParts: string[] = [];
   const thinkingParts: string[] = [];
 
@@ -127,14 +130,10 @@ function extractTextContent(content: InternalContentBlock[]): string {
     }
   }
 
-  // Prepend thinking content wrapped in <think> tags if present
-  let result = "";
-  if (thinkingParts.length > 0) {
-    result += `<think>${thinkingParts.join("")}</think>\n`;
-  }
-  result += textParts.join("");
-
-  return result;
+  return {
+    text: textParts.join(""),
+    reasoning: thinkingParts.length > 0 ? thinkingParts.join("") : undefined,
+  };
 }
 
 /**
@@ -168,7 +167,8 @@ export const openaiChatResponseAdapter: ResponseAdapter<OpenAIChatCompletion> =
     format: "openai-chat",
 
     serialize(response: InternalResponse): OpenAIChatCompletion {
-      const content = extractTextContent(response.content);
+      const { text: content, reasoning: reasoningContent } =
+        extractContent(response.content);
       const toolCalls = convertToolCalls(response.content);
 
       return {
@@ -182,6 +182,7 @@ export const openaiChatResponseAdapter: ResponseAdapter<OpenAIChatCompletion> =
             message: {
               role: "assistant",
               content: content || null,
+              ...(reasoningContent !== undefined && { reasoning_content: reasoningContent }),
               tool_calls: toolCalls,
             },
             finish_reason: convertStopReason(response.stopReason),