GPT-5.5 Quick Report: Should You Move from 5.4?¶
For / Key Points
Audience: Developers using Codex, the OpenAI API, or AI coding agents in production workflows
Key Points:
- GPT-5.5 is not a blanket replacement; route harder jobs there first
- Judge it by fewer retries and less rework, not by raw "smartness"
- Start with three lanes: keep on 5.4, move to 5.5, reserve for 5.5 Pro
GPT-5.5 became available in the API on 2026-04-24, so Codex/API teams now need to revisit model routing.1 The answer is not "move everything to 5.5." Move the jobs where a failed attempt is expensive.
Read GPT-5.5 not as a new strongest model, but as a decision point: which workloads should leave 5.4 first?
The Change Is About Longer Work¶
The important signal in GPT-5.5 is not short-answer quality. It is whether the model can keep working through a longer task without falling apart. OpenAI highlights gains in agentic coding, computer use, and professional knowledge work.1
That matters for jobs that require the model to re-read context. Examples include code changes, screen operations, investigation, log review, and test-failure repair. These are not single prompts; they are chains of observation and correction.
The API shape points in the same direction. GPT-5.5 supports a 1,050,000-token context window and 128,000 max output tokens.2 It also supports image input, function calling, structured outputs, web search, hosted shell, apply patch, Skills, computer use, and MCP.2
So GPT-5.5 should be evaluated as a long-running tool-using worker. If you treat it as a better text generator for every request, cost will rise before value appears.
Read Benchmarks by Use Case¶
The official benchmarks do not prove that GPT-5.5 wins everywhere. Claude Opus 4.7 leads on SWE-Bench Pro, and Gemini 3.1 Pro remains strong on BrowseComp.1 For Codex users, the most relevant signal is the Terminal-Bench 2.0 jump.
| Evaluation | How to read it | Meaning for Codex/API |
|---|---|---|
| Terminal-Bench 2.0 | GPT-5.5 scores 82.7%; 5.4 scores 75.1% | Strong signal for command, check, fix loops |
| SWE-Bench Pro | GPT-5.5 scores 58.6%; Opus 4.7 scores 64.3% | Opus still matters for issue resolution |
| OSWorld-Verified | GPT-5.5 scores 78.7%; 5.4 scores 75.0% | Useful signal for computer-use workflows |
| BrowseComp | GPT-5.5 scores 84.4%; Gemini 3.1 Pro scores 85.9% | Gemini remains a browsing candidate |
| GDPval | GPT-5.5 scores 84.9%; 5.4 scores 83.0% | Useful for professional work evaluation |
Terminal-Bench 2.0 is close to how CLI agents work. The model executes commands, reads output, decides what changed, then continues. That is why GPT-5.5 should first be tested on development jobs that require intermediate judgment.
Price Makes This a Retry-Rate Decision¶
Price is the strongest argument against blanket migration. GPT-5.5 costs $5.00 input, $0.50 cached input, and $30.00 output per 1M tokens. GPT-5.4 costs $2.50 input, $0.25 cached input, and $15.00 output.23
| Model | Price (input/output) | Role |
|---|---|---|
| GPT-5.4 | $2.50 / $15.00 | Default production baseline |
| GPT-5.5 | $5.00 / $30.00 | Upper route for hard development jobs |
| GPT-5.5 Pro | $30.00 / $180.00 | Exception route for slow high-accuracy review |
For a 10M input / 3M output monthly workload, GPT-5.4 is about $70 and GPT-5.5 is about $140. Moving the same workload to 5.5 simply doubles the bill. It pays off only when retries, manual edits, review fixes, or rollback work fall enough.
OpenAI says GPT-5.5 tends to complete Codex tasks with fewer tokens while matching GPT-5.4 per-token latency.1 That is useful, but you still need to measure it on your own repository. Adopting 5.5 is an economic retry-rate question, not a leaderboard question.
Start with Three Lanes¶
Do not change the default model first. Split your existing jobs into three lanes: keep on 5.4, move to 5.5, reserve for 5.5 Pro.
| Lane | Workloads | Why |
|---|---|---|
| Keep on 5.4 | Short summaries, routine writing, bulk classification, light transforms | Unit cost dominates |
| Move to 5.5 | Multi-file edits, CI failure investigation, long log analysis, refactors | Failure is expensive |
| Reserve for 5.5 Pro | Final review of important PRs, design decisions, slow high-accuracy checks | Latency and price are acceptable |
This keeps GPT-5.5 where its strengths matter. In Codex, the natural first tests are multi-file edits and CI failure diagnosis. Bulk short prompts should not be the first migration target.
Measure Before You Switch Defaults¶
Start with shadow comparison. Run the same task through 5.4 and 5.5, then compare diffs, test results, review edits, and retry count. One success is not enough.
- Run the same job twice: compare 5.4 and 5.5 on the same task.
- Measure failure cost: check retries, manual fixes, and review churn.
- Lock routing: move only the job categories where 5.5 clearly helps.
Security workflows need a separate check. OpenAI says GPT-5.5 includes stronger cyber safeguards, and some users may initially find the stricter classifiers annoying while tuning continues.14 For vulnerability reproduction, internal red-team support, or security automation, measure block rate as well as output quality.
Summary¶
The useful GPT-5.5 headline is not "5.4 is obsolete." It is this: 5.5 is worth using where it reduces rework enough to beat its price premium.
Create a routing table first. Keep short stable work on 5.4. Move long, judgment-heavy, high-cost-to-fail work to 5.5. Reserve GPT-5.5 Pro for slow checks where accuracy is worth the price.
That turns launch news into an operating rule.