What is GPT-5.4 Thinking Mode? (March 2026)
What is GPT-5.4 Thinking Mode? (March 2026)
GPT-5.4 Thinking is OpenAI’s reasoning mode where the model takes extra time to think through problems step-by-step before responding. It scores 94.3% on GPQA Diamond and 77.3% on SWE-bench, making it one of the top coding models in March 2026.
Quick Answer
GPT-5.4 Thinking is the “slow thinking” version of GPT-5.4, similar to what OpenAI previously called “o1” reasoning models. When you enable Thinking mode:
- The model takes longer to respond
- It reasons through the problem internally
- Output quality improves on complex tasks
- Costs slightly more per request
Released March 5, 2026 alongside the base GPT-5.4 model.
What’s New in GPT-5.4
The full GPT-5.4 release (March 5th) included:
| Feature | Details |
|---|---|
| 1M Token Context | Up from 128K in previous versions |
| Native Computer Use | Can control desktop applications |
| Merged Codex | Coding capabilities built into main model |
| 33% Fewer Errors | Compared to GPT-5.2 |
| Thinking Mode | Extended reasoning option |
Thinking Mode vs Standard Mode
| Aspect | GPT-5.4 | GPT-5.4 Thinking |
|---|---|---|
| Response Time | Fast | Slower |
| Best For | Simple tasks | Complex reasoning |
| GPQA Diamond | 91.2% | 94.3% |
| SWE-bench | 74.8% | 77.3% |
| Pricing | $5/$15 per 1M | $7.50/$22.50 per 1M |
How Thinking Mode Works
From the Every.to review:
“GPT-5.4 in the Codex app is my new daily driver for coding. It has a much more human thinking style than previous models.”
When you enable Thinking:
- Model receives your prompt
- Extended “thinking” phase (not visible to you)
- Model reasons through the problem
- Returns more considered response
Unlike Claude’s Thinking (which shows reasoning), GPT-5.4’s thinking process is hidden.
When to Use Thinking Mode
Use Thinking For:
- Complex coding problems
- Mathematical reasoning
- Multi-step logical tasks
- Architecture decisions
- Debugging tricky issues
- Tasks where accuracy > speed
Use Standard For:
- Quick questions
- Simple code generation
- Creative writing
- Chat/conversation
- High-throughput tasks
- Cost-sensitive workloads
Benchmarks (March 2026)
| Benchmark | GPT-5.4 Thinking | Claude Opus 4.6 | Winner |
|---|---|---|---|
| GPQA Diamond | 94.3% | 92.8% | GPT-5.4 |
| SWE-bench | 77.3% | 80.9% | Claude |
| HumanEval | 96.2% | 95.8% | GPT-5.4 |
| Terminal-Bench | 77.3% | 74.8% | GPT-5.4 |
| MMMU Pro | 82.4% | 85.1% | Claude |
GPT-5.4 Thinking leads on math/science (GPQA) and terminal tasks. Claude leads on software engineering (SWE-bench) and visual reasoning (MMMU).
Pricing Comparison
| Model | Input (1M tokens) | Output (1M tokens) |
|---|---|---|
| GPT-5.4 Standard | $5.00 | $15.00 |
| GPT-5.4 Thinking | $7.50 | $22.50 |
| Claude Opus 4.6 | $15.00 | $75.00 |
| Claude Sonnet 4.6 | $3.00 | $15.00 |
GPT-5.4 Thinking is 50% more expensive than standard but still cheaper than Claude Opus.
How to Access
Via ChatGPT
- Open ChatGPT
- Select GPT-5.4 model
- Toggle “High Effort” or “Thinking” mode
- Send your prompt
Via API
from openai import OpenAI
client = OpenAI()
response = client.chat.completions.create(
model="gpt-5.4-thinking",
messages=[{"role": "user", "content": "Your complex problem here"}],
# Extended reasoning enabled by default
)Via OpenAI Codex
The Codex app automatically uses Thinking mode for complex tasks.
User Reviews (First Week)
From Reddit r/AI_Agents:
“On paper it looks impressive — native computer use, 1M token context, 33% fewer errors than 5.2, and they finally merged Codex into the main model.”
From natesnewsletter.substack.com:
“GPT-5.4 is better than Opus 4.6 at some things (genuinely, measurably better) and I’m not going to take a silly example and milk it for outrage.”
Comparison with Claude Thinking
| Feature | GPT-5.4 Thinking | Claude Thinking |
|---|---|---|
| Shows reasoning | No (hidden) | Yes (visible) |
| Speed | Moderate | Slower |
| Best at | Math, science | Software engineering |
| Pricing | Cheaper | More expensive |
FAQ
How much slower is Thinking mode?
Typically 2-5x longer than standard mode. Complex problems may take 30-60 seconds.
Can I see what GPT-5.4 is thinking?
No, unlike Claude’s visible thinking, GPT-5.4’s reasoning process is hidden.
Is Thinking mode worth the extra cost?
For complex tasks, yes. The 50% price increase often yields better results. For simple tasks, standard mode is more efficient.
Does Thinking mode work with the 1M context window?
Yes, both features work together. You can have extended context AND extended reasoning.
Last verified: March 13, 2026