[codex] strip codex responses max_output_tokens (#399)

* strip codex responses max_output_tokens

* address codex responses review comments

src/server/routes/proxy/architecture-boundaries.test.ts

@@ -98,6 +98,15 @@ describe('proxy route architecture boundaries', () => {
     expect(source).not.toContain('shouldInjectDerivedPromptCacheKey');
   });
 
+  it('keeps codex responses normalization behind transformer helpers', () => {
+    const source = readSource('./upstreamEndpoint.ts');
+    expect(source).toContain("from '../../transformers/openai/responses/codexCompatibility.js'");
+    expect(source).not.toContain('function ensureCodexResponsesInstructions(');
+    expect(source).not.toContain('function ensureCodexResponsesStoreFalse(');
+    expect(source).not.toContain('function stripCodexUnsupportedResponsesFields(');
+    expect(source).not.toContain('function applyCodexResponsesCompatibility(');
+  });
+
   it('keeps endpoint runtime snapshot helper out of the route layer', () => {
     const source = readSource('./upstreamEndpoint.ts');
     expect(source).not.toContain('function getUpstreamEndpointRuntimeStateSnapshot(');

src/server/routes/proxy/chat.codex-oauth.test.ts

@@ -210,7 +210,8 @@ describe('chat proxy codex oauth compatibility', () => {
     expect(forwardedBody.store).toBe(false);
     expect(forwardedBody.parallel_tool_calls).toBeUndefined();
     expect(forwardedBody.include).toBeUndefined();
-    expect(forwardedBody.max_output_tokens).toBe(256);
+    expect(forwardedBody.max_output_tokens).toBeUndefined();
+    expect(forwardedBody.max_tokens).toBeUndefined();
     expect(forwardedBody.max_completion_tokens).toBeUndefined();
 
     const body = response.json();

src/server/routes/proxy/upstreamEndpoint.test.ts

@@ -736,7 +736,9 @@ describe('buildUpstreamEndpointRequest', () => {
     expect(request.body.store).toBe(false);
     expect(request.body.parallel_tool_calls).toBeUndefined();
     expect(request.body.include).toBeUndefined();
-    expect(request.body.max_output_tokens).toBe(4096);
+    expect(request.body.max_output_tokens).toBeUndefined();
+    expect(request.body.max_tokens).toBeUndefined();
+    expect(request.body.max_completion_tokens).toBeUndefined();
     expect(request.body.temperature).toBe(0.2);
     expect(request.body.top_p).toBe(0.9);
     expect(request.body.user).toBe('drop-me');
@@ -834,7 +836,7 @@ describe('buildUpstreamEndpointRequest', () => {
     expect(request.body.prompt_cache_key).toBe('codex-cache-123');
   });
 
-  it('preserves native codex responses continuity and request fields without compatibility rewrites', () => {
+  it('preserves native codex responses continuity while stripping unsupported token limit fields', () => {
     const request = buildUpstreamEndpointRequest({
       endpoint: 'responses',
       modelName: 'gpt-5.4',
@@ -854,6 +856,8 @@ describe('buildUpstreamEndpointRequest', () => {
         previous_response_id: 'resp_prev_123',
         temperature: 0.3,
         top_p: 0.8,
+        max_completion_tokens: 256,
+        max_tokens: 128,
         max_output_tokens: 512,
       },
       providerHeaders: {
@@ -873,7 +877,9 @@ describe('buildUpstreamEndpointRequest', () => {
     expect(request.body.previous_response_id).toBe('resp_prev_123');
     expect(request.body.temperature).toBe(0.3);
     expect(request.body.top_p).toBe(0.8);
-    expect(request.body.max_output_tokens).toBe(512);
+    expect(request.body.max_completion_tokens).toBeUndefined();
+    expect(request.body.max_tokens).toBeUndefined();
+    expect(request.body.max_output_tokens).toBeUndefined();
   });
 
   it('applies configured codex header defaults with CLIProxyAPI-compatible precedence', () => {
@@ -1002,6 +1008,9 @@ describe('buildUpstreamEndpointRequest', () => {
           models: [{ name: 'gpt-5.4', protocol: 'codex' }],
           params: {
             'text.verbosity': 'low',
+            max_completion_tokens: 48,
+            max_tokens: 32,
+            max_output_tokens: 64,
             store: true,
           },
         },
@@ -1038,6 +1047,9 @@ describe('buildUpstreamEndpointRequest', () => {
     expect(request.body.reasoning).toEqual({ effort: 'high' });
     expect(request.body.text).toEqual({ verbosity: 'low' });
     expect(request.body.safety_identifier).toBeUndefined();
+    expect(request.body.max_completion_tokens).toBeUndefined();
+    expect(request.body.max_tokens).toBeUndefined();
+    expect(request.body.max_output_tokens).toBeUndefined();
     expect(request.body.store).toBe(false);
   });
 

src/server/routes/proxy/upstreamEndpoint.ts

@@ -17,6 +17,7 @@ import {
   convertOpenAiBodyToResponsesBody as convertOpenAiBodyToResponsesBodyViaTransformer,
   sanitizeResponsesBodyForProxy as sanitizeResponsesBodyForProxyViaTransformer,
 } from '../../transformers/openai/responses/conversion.js';
+import { normalizeCodexResponsesBodyForProxy } from '../../transformers/openai/responses/codexCompatibility.js';
 import {
   convertOpenAiBodyToAnthropicMessagesBody,
   sanitizeAnthropicMessagesBody,
@@ -370,61 +371,6 @@ function toFiniteNumber(value: unknown): number | null {
   return typeof value === 'number' && Number.isFinite(value) ? value : null;
 }
 
-function ensureCodexResponsesInstructions(
-  body: Record<string, unknown>,
-  sitePlatform: string,
-): Record<string, unknown> {
-  if (sitePlatform !== 'codex') return body;
-  if (typeof body.instructions === 'string') return body;
-  return {
-    ...body,
-    instructions: '',
-  };
-}
-
-function ensureCodexResponsesStoreFalse(
-  body: Record<string, unknown>,
-  sitePlatform: string,
-): Record<string, unknown> {
-  if (sitePlatform !== 'codex') return body;
-  return {
-    ...body,
-    store: false,
-  };
-}
-
-function convertCodexSystemRoleToDeveloper(input: unknown): unknown {
-  if (!Array.isArray(input)) return input;
-  return input.map((item) => {
-    if (!isRecord(item)) return item;
-    if (asTrimmedString(item.type).toLowerCase() !== 'message') return item;
-    if (asTrimmedString(item.role).toLowerCase() !== 'system') return item;
-    return {
-      ...item,
-      role: 'developer',
-    };
-  });
-}
-
-function applyCodexResponsesCompatibility(
-  body: Record<string, unknown>,
-  sitePlatform: string,
-): Record<string, unknown> {
-  if (sitePlatform !== 'codex') return body;
-
-  const next: Record<string, unknown> = {
-    ...body,
-    input: convertCodexSystemRoleToDeveloper(body.input),
-  };
-
-  if (typeof next.instructions !== 'string') {
-    next.instructions = '';
-  }
-
-  return next;
-}
-
-
 function normalizeEndpointTypes(value: unknown): UpstreamEndpoint[] {
   const raw = asTrimmedString(value).toLowerCase();
   if (!raw) return [];
@@ -957,17 +903,11 @@ export function buildUpstreamEndpointRequest(input: {
     if (preserveWebsocketIncrementalMode && rawBody.generate === false) {
       sanitizedResponsesBody.generate = false;
     }
-    const body = ensureCodexResponsesStoreFalse(
+    const body = normalizeCodexResponsesBodyForProxy(
-      ensureCodexResponsesInstructions(
-        applyCodexResponsesCompatibility(
       sanitizedResponsesBody,
       sitePlatform,
-        ),
-        sitePlatform,
-      ),
-      sitePlatform,
     );
-    const configuredResponsesBody = ensureCodexResponsesStoreFalse(
+    const configuredResponsesBody = normalizeCodexResponsesBodyForProxy(
       applyConfiguredPayloadRules(body),
       sitePlatform,
     );

src/server/transformers/openai/responses/codexCompatibility.test.ts

@@ -0,0 +1,45 @@
+import { describe, expect, it } from 'vitest';
+import { normalizeCodexResponsesBodyForProxy } from './codexCompatibility.js';
+
+describe('normalizeCodexResponsesBodyForProxy', () => {
+  it('normalizes codex responses bodies before proxying upstream', () => {
+    const body = normalizeCodexResponsesBodyForProxy({
+      input: [
+        {
+          type: 'message',
+          role: 'system',
+          content: [{ type: 'input_text', text: 'be precise' }],
+        },
+      ],
+      max_output_tokens: 512,
+      max_completion_tokens: 256,
+      max_tokens: 128,
+      temperature: 0.3,
+      store: true,
+    }, 'codex');
+
+    expect(body).toEqual({
+      input: [
+        {
+          type: 'message',
+          role: 'developer',
+          content: [{ type: 'input_text', text: 'be precise' }],
+        },
+      ],
+      instructions: '',
+      store: false,
+      temperature: 0.3,
+    });
+  });
+
+  it('leaves non-codex bodies untouched', () => {
+    const source = {
+      input: 'hello',
+      max_output_tokens: 512,
+    };
+
+    const body = normalizeCodexResponsesBodyForProxy(source, 'openai');
+
+    expect(body).toBe(source);
+  });
+});

src/server/transformers/openai/responses/codexCompatibility.ts

@@ -0,0 +1,90 @@
+function isRecord(value: unknown): value is Record<string, unknown> {
+  return !!value && typeof value === 'object';
+}
+
+function asTrimmedString(value: unknown): string {
+  return typeof value === 'string' ? value.trim() : '';
+}
+
+function ensureCodexResponsesInstructions(
+  body: Record<string, unknown>,
+  sitePlatform: string,
+): Record<string, unknown> {
+  if (sitePlatform !== 'codex') return body;
+  if (typeof body.instructions === 'string') return body;
+  return {
+    ...body,
+    instructions: '',
+  };
+}
+
+function ensureCodexResponsesStoreFalse(
+  body: Record<string, unknown>,
+  sitePlatform: string,
+): Record<string, unknown> {
+  if (sitePlatform !== 'codex') return body;
+  return {
+    ...body,
+    store: false,
+  };
+}
+
+function stripCodexUnsupportedResponsesFields(
+  body: Record<string, unknown>,
+  sitePlatform: string,
+): Record<string, unknown> {
+  if (sitePlatform !== 'codex') return body;
+  const next = { ...body };
+  delete next.max_output_tokens;
+  delete next.max_completion_tokens;
+  delete next.max_tokens;
+  return next;
+}
+
+function convertCodexSystemRoleToDeveloper(input: unknown): unknown {
+  if (!Array.isArray(input)) return input;
+  return input.map((item) => {
+    if (!isRecord(item)) return item;
+    if (asTrimmedString(item.type).toLowerCase() !== 'message') return item;
+    if (asTrimmedString(item.role).toLowerCase() !== 'system') return item;
+    return {
+      ...item,
+      role: 'developer',
+    };
+  });
+}
+
+function applyCodexResponsesCompatibility(
+  body: Record<string, unknown>,
+  sitePlatform: string,
+): Record<string, unknown> {
+  if (sitePlatform !== 'codex') return body;
+
+  const next: Record<string, unknown> = {
+    ...body,
+    input: convertCodexSystemRoleToDeveloper(body.input),
+  };
+
+  if (typeof next.instructions !== 'string') {
+    next.instructions = '';
+  }
+
+  return next;
+}
+
+export function normalizeCodexResponsesBodyForProxy(
+  body: Record<string, unknown>,
+  sitePlatform: string,
+): Record<string, unknown> {
+  if (sitePlatform !== 'codex') return body;
+  return ensureCodexResponsesStoreFalse(
+    stripCodexUnsupportedResponsesFields(
+      ensureCodexResponsesInstructions(
+        applyCodexResponsesCompatibility(body, sitePlatform),
+        sitePlatform,
+      ),
+      sitePlatform,
+    ),
+    sitePlatform,
+  );
+}