feat: codex auth support (#7537)

packages/opencode/src/session/llm.ts

@@ -1,3 +1,5 @@
+import os from "os"
+import { Installation } from "@/installation"
 import { Provider } from "@/provider/provider"
 import { Log } from "@/util/log"
 import {
@@ -19,6 +21,7 @@ import { Plugin } from "@/plugin"
 import { SystemPrompt } from "./system"
 import { Flag } from "@/flag/flag"
 import { PermissionNext } from "@/permission/next"
+import { Auth } from "@/auth"
 
 export namespace LLM {
   const log = Log.create({ service: "llm" })
@@ -82,12 +85,24 @@ export namespace LLM {
     }
 
     const provider = await Provider.getProvider(input.model.providerID)
+    const auth = await Auth.get(input.model.providerID)
+    const isCodex = provider.id === "openai" && auth?.type === "oauth"
+
     const variant =
       !input.small && input.model.variants && input.user.variant ? input.model.variants[input.user.variant] : {}
     const base = input.small
       ? ProviderTransform.smallOptions(input.model)
       : ProviderTransform.options(input.model, input.sessionID, provider.options)
-    const options = pipe(base, mergeDeep(input.model.options), mergeDeep(input.agent.options), mergeDeep(variant))
+    const options: Record<string, any> = pipe(
+      base,
+      mergeDeep(input.model.options),
+      mergeDeep(input.agent.options),
+      mergeDeep(variant),
+    )
+    if (isCodex) {
+      options.instructions = SystemPrompt.instructions()
+      options.store = false
+    }
 
     const params = await Plugin.trigger(
       "chat.params",
@@ -108,16 +123,14 @@ export namespace LLM {
       },
     )
 
-    l.info("params", {
-      params,
-    })
-
-    const maxOutputTokens = ProviderTransform.maxOutputTokens(
-      input.model.api.npm,
-      params.options,
-      input.model.limit.output,
-      OUTPUT_TOKEN_MAX,
-    )
+    const maxOutputTokens = isCodex
+      ? undefined
+      : ProviderTransform.maxOutputTokens(
+          input.model.api.npm,
+          params.options,
+          input.model.limit.output,
+          OUTPUT_TOKEN_MAX,
+        )
 
     const tools = await resolveTools(input)
 
@@ -157,6 +170,13 @@ export namespace LLM {
       maxOutputTokens,
       abortSignal: input.abort,
       headers: {
+        ...(isCodex
+          ? {
+              originator: "opencode",
+              "User-Agent": `opencode/${Installation.VERSION} (${os.platform()} ${os.release()}; ${os.arch()})`,
+              session_id: input.sessionID,
+            }
+          : undefined),
         ...(input.model.providerID.startsWith("opencode")
           ? {
               "x-opencode-project": Instance.project.id,
@@ -169,12 +189,19 @@ export namespace LLM {
       },
       maxRetries: input.retries ?? 0,
       messages: [
-        ...system.map(
-          (x): ModelMessage => ({
-            role: "system",
-            content: x,
-          }),
-        ),
+        ...(isCodex
+          ? [
+              {
+                role: "user",
+                content: system.join("\n\n"),
+              } as ModelMessage,
+            ]
+          : system.map(
+              (x): ModelMessage => ({
+                role: "system",
+                content: x,
+              }),
+            )),
         ...input.messages,
       ],
       model: wrapLanguageModel({

packages/opencode/src/session/prompt/codex_header.txt

@@ -0,0 +1 @@
+You are a coding agent running in the opencode, a terminal-based coding assistant. opencode is an open source project. You are expected to be precise, safe, and helpful.

packages/opencode/src/session/system.ts

@@ -14,6 +14,7 @@ import PROMPT_GEMINI from "./prompt/gemini.txt"
 import PROMPT_ANTHROPIC_SPOOF from "./prompt/anthropic_spoof.txt"
 
 import PROMPT_CODEX from "./prompt/codex.txt"
+import PROMPT_CODEX_INSTRUCTIONS from "./prompt/codex_header.txt"
 import type { Provider } from "@/provider/provider"
 import { Flag } from "@/flag/flag"
 
@@ -23,6 +24,10 @@ export namespace SystemPrompt {
     return []
   }
 
+  export function instructions() {
+    return PROMPT_CODEX_INSTRUCTIONS.trim()
+  }
+
   export function provider(model: Provider.Model) {
     if (model.api.id.includes("gpt-5")) return [PROMPT_CODEX]
     if (model.api.id.includes("gpt-") || model.api.id.includes("o1") || model.api.id.includes("o3"))