fix: decode zstd responses while restoring claude encoding

src/server/proxy-core/providers/claudeProviderProfile.ts

@@ -83,7 +83,7 @@ function buildClaudeRuntimeHeaders(input: {
     'User-Agent': getInputHeader(input.claudeHeaders, 'user-agent') || CLAUDE_DEFAULT_USER_AGENT,
     Connection: 'keep-alive',
     Accept: input.stream ? 'text/event-stream' : 'application/json',
-    'Accept-Encoding': 'identity',
+    'Accept-Encoding': 'gzip, deflate, br, zstd',
   };
   if (input.isClaudeOauthUpstream) {
     headers.Authorization = `Bearer ${input.tokenValue}`;

src/server/proxy-core/providers/registry.test.ts

@@ -70,7 +70,7 @@ describe('resolveProviderProfile', () => {
     expect(result.headers.Authorization).toBe('Bearer oauth-access-token');
     expect(result.headers['x-api-key']).toBeUndefined();
     expect(result.headers['anthropic-version']).toBe('2023-06-01');
-    expect(result.headers['Accept-Encoding']).toBe('identity');
+    expect(result.headers['Accept-Encoding']).toBe('gzip, deflate, br, zstd');
     expect(result.runtime).toMatchObject({
       executor: 'claude',
       modelName: 'claude-opus-4-6',