Revert "fix: explicitly pass model provider on session resume (#139)"

This reverts commit 5e99c28.

Author: xiatg

src/CodexAcpClient.ts

@@ -205,7 +205,7 @@ export class CodexAcpClient {
         const response = await this.codexClient.threadResume({
             config: await this.createSessionConfig(request.cwd, request.mcpServers ?? []),
             cwd: request.cwd,
-            modelProvider: this.getResumeModelProvider(),
+            modelProvider: this.getModelProvider(),
             threadId: request.sessionId,
         });
         const codexModels = await this.fetchAvailableModels();
@@ -222,7 +222,7 @@ export class CodexAcpClient {
         const response = await this.codexClient.threadResume({
             config: await this.createSessionConfig(request.cwd, request.mcpServers ?? []),
             cwd: request.cwd,
-            modelProvider: this.getResumeModelProvider(),
+            modelProvider: this.getModelProvider(),
             threadId: request.sessionId,
         });
         const codexModels = await this.fetchAvailableModels();
@@ -306,12 +306,6 @@ export class CodexAcpClient {
         return this.gatewayConfig?.modelProvider ?? this.modelProvider;
     }
 
-    private getResumeModelProvider(): string {
-        // Passing `null` forces codex to use the persisted provider for resumed session instead of default one
-        // Explicit fallback to "openai" fixes error `Model provider not found` at least for ChatGPT authentication
-        return this.getModelProvider() ?? "openai";
-    }
-
     private async refreshSkills(cwd: string, meta?: Record<string, unknown> | null): Promise<void> {
         if (!cwd) {
             return;