fix(proxy): rewrite Claude Code compatible requests

open-sse/services/claudeCodeCompatible.ts

@@ -1,6 +1,9 @@
 import { createHash, randomUUID } from "node:crypto";
 
-import { prepareClaudeRequest } from "../translator/helpers/claudeHelper.ts";
+import {
+  applyClaudeOAuthLexicalRewrite,
+  prepareClaudeRequest,
+} from "../translator/helpers/claudeHelper.ts";
 
 export const CLAUDE_CODE_COMPATIBLE_PREFIX = "anthropic-compatible-cc-";
 export const CLAUDE_CODE_COMPATIBLE_DEFAULT_CHAT_PATH = "/v1/messages?beta=true";
@@ -180,11 +183,13 @@ export function buildClaudeCodeCompatibleRequest({
   const toolChoice =
     tools.length > 0
       ? buildClaudeCodeCompatibleToolChoice(
-          normalizedBody?.["tool_choice"] ?? sourceBody?.["tool_choice"]
+          preparedClaudeBody?.tool_choice ??
+            normalizedBody?.["tool_choice"] ??
+            sourceBody?.["tool_choice"]
         )
       : undefined;
 
-  return {
+  const requestBody = {
     model,
     messages,
     system,
@@ -217,6 +222,13 @@ export function buildClaudeCodeCompatibleRequest({
     ...(toolChoice ? { tool_choice: toolChoice } : {}),
     ...(stream ? { stream: true } : {}),
   };
+
+  const lexicalRewrite = applyClaudeOAuthLexicalRewrite(requestBody);
+  if (lexicalRewrite.toolNameMap) {
+    lexicalRewrite.body._toolNameMap = lexicalRewrite.toolNameMap;
+  }
+
+  return lexicalRewrite.body;
 }
 
 export function resolveClaudeCodeCompatibleEffort(
@@ -539,6 +551,7 @@ function prepareClaudeCodeCompatibleBody(
       system: normalizeClaudeSystemInput(claudeBody.system),
       messages: normalizeClaudeMessageInput(claudeBody.messages),
       tools: normalizeClaudeToolInput(claudeBody.tools),
+      tool_choice: readRecord(claudeBody.tool_choice) || claudeBody.tool_choice,
       thinking: readRecord(claudeBody.thinking) || claudeBody.thinking,
     },
     CLAUDE_CODE_COMPATIBLE_PREFIX,

tests/unit/claude-code-compatible-request.test.mjs

@@ -109,16 +109,29 @@ test("buildClaudeCodeCompatibleRequest covers normalized OpenAI-style messages,
 test("buildClaudeCodeCompatibleRequest covers Claude-native bodies and cache-control stripping", () => {
   const stripped = buildClaudeCodeCompatibleRequest({
     claudeBody: {
-      system: [{ type: "text", text: "sys", cache_control: { type: "ephemeral" } }],
+      system: [
+        {
+          type: "text",
+          text: "sys <directories>src/</directories>",
+          cache_control: { type: "ephemeral" },
+        },
+      ],
       messages: [
         {
           role: "assistant",
-          content: [{ type: "text", text: "prefill", cache_control: { type: "ephemeral" } }],
+          content: [
+            { type: "text", text: "prefill", cache_control: { type: "ephemeral" } },
+            { type: "tool_use", id: "call_1", name: "background_output", input: {} },
+          ],
         },
         {
           role: "user",
           content: [
-            { type: "text", text: "ask", cache_control: { type: "ephemeral" } },
+            {
+              type: "text",
+              text: "ask background_cancel",
+              cache_control: { type: "ephemeral" },
+            },
             {
               type: "image",
               source: { type: "base64", media_type: "image/png", data: "abc" },
@@ -132,8 +145,14 @@ test("buildClaudeCodeCompatibleRequest covers Claude-native bodies and cache-con
         },
       ],
       tools: [
-        { name: "toolA", input_schema: { type: "object" }, cache_control: { type: "ephemeral" } },
+        {
+          name: "background_cancel",
+          description: "Cancel background_output work",
+          input_schema: { type: "object" },
+          cache_control: { type: "ephemeral" },
+        },
       ],
+      tool_choice: { type: "tool", name: "background_cancel" },
       thinking: { type: "enabled", budget_tokens: 12 },
     },
     model: "claude-sonnet-4-6",
@@ -171,8 +190,16 @@ test("buildClaudeCodeCompatibleRequest covers Claude-native bodies and cache-con
   assert.equal(JSON.parse(stripped.metadata.user_id).session_id, "explicit-session");
   assert.equal(stripped.messages.at(-1).role, "user");
   assert.equal(stripped.messages[0].content[0].cache_control, undefined);
+  assert.equal(stripped.messages[0].content[1].name, "background_result");
+  assert.equal(stripped.messages[1].content[0].text, "ask background_stop");
   assert.equal(stripped.system.at(-1).cache_control, undefined);
+  assert.equal(stripped.system.at(-1).text, "sys directories:\nsrc/");
   assert.equal(stripped.tools[0].cache_control, undefined);
+  assert.equal(stripped.tools[0].name, "background_stop");
+  assert.equal(stripped.tools[0].description, "Cancel background_result work");
+  assert.deepEqual(stripped.tool_choice, { type: "tool", name: "background_stop" });
+  assert.equal(stripped._toolNameMap.get("background_result"), "background_output");
+  assert.equal(stripped._toolNameMap.get("background_stop"), "background_cancel");
   assert.equal(preserved.messages[0].content[0].cache_control.type, "ephemeral");
   assert.equal(preserved.system.at(-1).cache_control.type, "ephemeral");
   assert.equal(preserved.tools[0].cache_control.type, "ephemeral");