From 9d5e89560cf3d0282e9fcb7d48d32a9db04b1183 Mon Sep 17 00:00:00 2001
From: Pedro Filho <pedro@filho.me>
Date: Fri, 21 Aug 2026 11:27:39 -0300
Subject: [PATCH] codex keeps its shell and apply_patch tools on the gpt-5.6
 models

---
 CHANGELOG.md      |  1 +
 package.json      |  2 +-
 src/proxy.test.ts | 23 +++++++++++++++++++----
 src/proxy.ts      | 10 +++++-----
 4 files changed, 26 insertions(+), 10 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 52ee4e4..246de57 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,4 @@
+- [2026-08-21] codex keeps its shell and apply_patch tools on the gpt-5.6 models
 - [2026-08-18] meter clients that hang up early
 - [2026-08-18] reclaim bare provider tables
 - [2026-08-18] settings shows pi
diff --git a/package.json b/package.json
index 04a0258..7ec8ed3 100644
--- a/package.json
+++ b/package.json
@@ -59,5 +59,5 @@
 		"post-commit": "bun x @rubriclab/package post-commit"
 	},
 	"type": "module",
-	"version": "0.0.65"
+	"version": "0.0.66"
 }
diff --git a/src/proxy.test.ts b/src/proxy.test.ts
index b223a78..2e0d3b6 100644
--- a/src/proxy.test.ts
+++ b/src/proxy.test.ts
@@ -44,13 +44,11 @@ describe('chatgpt dialect adapter', () => {
 		expect(adapted.max_output_tokens).toBeUndefined()
 	})
 
-	test('merges lifted developer messages after existing instructions', () => {
+	test('merges lifted system messages after existing instructions', () => {
 		const adapted = JSON.parse(
 			adaptChatGptRequest(
 				JSON.stringify({
-					input: [
-						{ content: [{ text: 'Prefer short replies.', type: 'input_text' }], role: 'developer' }
-					],
+					input: [{ content: [{ text: 'Prefer short replies.', type: 'input_text' }], role: 'system' }],
 					instructions: 'You are a coding agent.'
 				})
 			)
@@ -59,6 +57,23 @@ describe('chatgpt dialect adapter', () => {
 		expect(adapted.input).toHaveLength(0)
 	})
 
+	test('keeps developer messages in input', () => {
+		const adapted = JSON.parse(
+			adaptChatGptRequest(
+				JSON.stringify({
+					input: [
+						{ content: [{ text: 'You are working inside bb.', type: 'input_text' }], role: 'developer' },
+						{ content: [{ text: 'Drop this one.', type: 'input_text' }], role: 'system' },
+						{ content: [{ text: 'hi', type: 'input_text' }], role: 'user' }
+					],
+					instructions: 'You are Codex.'
+				})
+			)
+		)
+		expect(adapted.instructions).toBe('You are Codex.\n\nDrop this one.')
+		expect(adapted.input.map((item: { role: string }) => item.role)).toEqual(['developer', 'user'])
+	})
+
 	test('leaves codex-shaped requests and non-json bodies alone', () => {
 		const codexShaped = JSON.stringify({
 			input: [{ content: [{ text: 'hi', type: 'input_text' }], role: 'user' }],
diff --git a/src/proxy.ts b/src/proxy.ts
index 6313f19..50ab7cd 100644
--- a/src/proxy.ts
+++ b/src/proxy.ts
@@ -239,7 +239,9 @@ function messageText(item: ResponsesInputMessage): string {
 // The ChatGPT codex backend rejects requests third-party harnesses send to a
 // standard Responses endpoint: system messages must ride in `instructions`
 // ("System messages are not allowed") and `max_output_tokens` is unsupported.
-// Codex's own requests already have that shape, so this is a no-op for them.
+// Developer messages are accepted and must stay in `input`: codex sends its
+// tool contract as developer items, and the gpt-5.6 models drop the shell and
+// apply_patch tools when those items arrive folded into `instructions`.
 export function adaptChatGptRequest(raw: string): string {
 	let parsed: { input?: unknown; instructions?: unknown; [key: string]: unknown }
 	try {
@@ -250,10 +252,8 @@ export function adaptChatGptRequest(raw: string): string {
 	if (typeof parsed !== 'object' || parsed === null || !Array.isArray(parsed.input)) {
 		return raw
 	}
-	const isSystem = (item: unknown): item is ResponsesInputMessage => {
-		const role = (item as ResponsesInputMessage | null)?.role
-		return role === 'system' || role === 'developer'
-	}
+	const isSystem = (item: unknown): item is ResponsesInputMessage =>
+		(item as ResponsesInputMessage | null)?.role === 'system'
 	const lifted = parsed.input.filter(isSystem).map(messageText)
 	const instructions = [
 		...(typeof parsed.instructions === 'string' ? [parsed.instructions] : []),