tweak: adjust codex plugin logic so that codex instruction isn't always added (oauth plan no longer enforces instruction whitelisting) (#18337)

packages/opencode/src/session/llm.ts

@@ -63,14 +63,14 @@ export namespace LLM {
       Provider.getProvider(input.model.providerID),
       Auth.get(input.model.providerID),
     ])
-    const isCodex = provider.id === "openai" && auth?.type === "oauth"
+    // TODO: move this to a proper hook
+    const isOpenaiOauth = provider.id === "openai" && auth?.type === "oauth"
 
-    const system = []
+    const system: string[] = []
     system.push(
       [
         // use agent prompt otherwise provider prompt
-        // For Codex sessions, skip SystemPrompt.provider() since it's sent via options.instructions
-        ...(input.agent.prompt ? [input.agent.prompt] : isCodex ? [] : SystemPrompt.provider(input.model)),
+        ...(input.agent.prompt ? [input.agent.prompt] : SystemPrompt.provider(input.model)),
         // any custom prompt passed into this call
         ...input.system,
         // any custom prompt from last user message
@@ -108,10 +108,22 @@ export namespace LLM {
       mergeDeep(input.agent.options),
       mergeDeep(variant),
     )
-    if (isCodex) {
-      options.instructions = SystemPrompt.instructions()
+    if (isOpenaiOauth) {
+      options.instructions = system.join("\n")
     }
 
+    const messages = isOpenaiOauth
+      ? input.messages
+      : [
+          ...system.map(
+            (x): ModelMessage => ({
+              role: "system",
+              content: x,
+            }),
+          ),
+          ...input.messages,
+        ]
+
     const params = await Plugin.trigger(
       "chat.params",
       {
@@ -146,7 +158,9 @@ export namespace LLM {
     )
 
     const maxOutputTokens =
-      isCodex || provider.id.includes("github-copilot") ? undefined : ProviderTransform.maxOutputTokens(input.model)
+      isOpenaiOauth || provider.id.includes("github-copilot")
+        ? undefined
+        : ProviderTransform.maxOutputTokens(input.model)
 
     const tools = await resolveTools(input)
 
@@ -217,15 +231,7 @@ export namespace LLM {
         ...headers,
       },
       maxRetries: input.retries ?? 0,
-      messages: [
-        ...system.map(
-          (x): ModelMessage => ({
-            role: "system",
-            content: x,
-          }),
-        ),
-        ...input.messages,
-      ],
+      messages,
       model: wrapLanguageModel({
         model: language,
         middleware: [