OpenAI recently introduced OAuth authentication for ChatGPT subscriptions, allowing tools like Cline to use your existing subscription instead of managing API keys. Here are the key restrictions: cline
The main restriction is rate limiting tied to your ChatGPT subscription tier: reddit
- Plus users: Around 300–1,500 local messages every 5 hours, or 50–400 cloud tasks depending on complexity
- Pro users: Higher limits but still capped with 5-hour and weekly limits
- Usage counts against your overall ChatGPT subscription quota, not separate API credits github
Many users report hitting limits quickly, especially with intensive agentic coding workflows. community.openai
The models available depend on your subscription tier :
- gpt-5.2-codex: Optimized for agentic coding
- gpt-5.2: General-purpose with strong reasoning
- gpt-5-mini: Fast and cost-effective
- o3 / o4-mini: Advanced and everyday reasoning tasks
| Aspect | OAuth (ChatGPT Subscription) | API Keys |
|---|---|---|
| Pricing | Flat-rate (subscription) cline | Pay-per-token reddit |
| Limits | Time-based (5h/weekly caps) github | Token/request limits platform.openai |
| Setup | One-click sign-in | Manual key management |
| Credential exposure | Tokens handled automatically cline | Risk of accidental commits |
- Shared quota: Usage in Cline draws from the same pool as your ChatGPT web/app usage github
- No separate budget: You cannot add API credits to bypass OAuth limits—they're tied strictly to your subscription tier github
- Security: Your OpenAI credentials never leave OpenAI's servers; Cline only receives access tokens cline
For heavy coding use, some users find the 5-hour and weekly caps frustrating and prefer third-party providers or direct API access for more flexibility. community.openai
The picture is actually more nuanced than a simple "yes" or "no."
What Claude Code Uses Haiku For (Regardless of Your Setting)
Even when you set Opus 4.5 as your model, Claude Code uses Haiku for specific background tasks:[reddit]
Status messages: The "Transforming...", "Analyzing...", "Reading..." text
Command approval: Deciding if a command matches your allow/deny patterns
Reading large files: ~50% of all Claude Code calls reportedly use Haiku for file reading operations[reddit]
Tool call parsing: Processing the structured output from tools
These aren't your "main" coding tasks—they're internal operations where using Opus would be wasteful.[reddit]
Your Primary Tasks Respect Your Model Choice
For actual coding work—writing code, refactoring, answering questions—Claude Code uses whatever model you've set. One video analysis specifically noted: "Claude Code does not intelligently determine which model to use for your request. There's no back-end logic that says 'this is a simple request, so let's use a lightweight model'".[youtube][reddit]
So if you set Opus 4.5, your coding prompts go to Opus 4.5.
The Cost Implication
Why This Still Saves Anthropic Money
The 50% figure is significant. Reading files, checking permissions, and internal routing add up quickly in agentic workflows. By handling these with Haiku, Anthropic dramatically reduces the cost per session—even when your "real" work hits Opus.[reddit]
Third-party tools like Cline don't have this optimization layer. Every API call—including file reads and internal checks—would use whatever expensive model you configured, making the economics unsustainable for a flat-rate subscription.[reddit]
What Claude Code Uses Haiku For (Regardless of Your Setting)
Even when you set Opus 4.5 as your model, Claude Code uses Haiku for specific background tasks: [reddit](https://www.reddit.com/r/ClaudeAI/comments/1lcntv4/claude_code_200_plan_switched_to_35_haiku_even/)
These aren't your "main" coding tasks—they're internal operations where using Opus would be wasteful. [reddit](https://www.reddit.com/r/ClaudeAI/comments/1lcntv4/claude_code_200_plan_switched_to_35_haiku_even/)
Your Primary Tasks Respect Your Model Choice
For actual coding work—writing code, refactoring, answering questions—Claude Code uses whatever model you've set. One video analysis specifically noted: "Claude Code does not intelligently determine which model to use for your request. There's no back-end logic that says 'this is a simple request, so let's use a lightweight model'". [youtube](https://www.youtube.com/watch?v=eP9fA5MHG20)
So if you set Opus 4.5, your coding prompts go to Opus 4.5.
The Cost Implication
Why This Still Saves Anthropic Money
The 50% figure is significant. Reading files, checking permissions, and internal routing add up quickly in agentic workflows. By handling these with Haiku, Anthropic dramatically reduces the cost per session—even when your "real" work hits Opus. [reddit](https://www.reddit.com/r/ClaudeAI/comments/1myw74x/analyzed_months_of_claude_code_usage_logs_tell/)
Third-party tools like Cline don't have this optimization layer. Every API call—including file reads and internal checks—would use whatever expensive model you configured, making the economics unsustainable for a flat-rate subscription. [reddit](https://www.reddit.com/r/ClaudeAI/comments/1myw74x/analyzed_months_of_claude_code_usage_logs_tell/)