GPT-5.3-Codex vs GPT-5.5 for workflow automation
Effectively a dead heat: 90–88
Same 12 workflow automation tasks, marked blind by three rival labs. GPT-5.3-Codex took 3 tasks, GPT-5.5 took 1, 8 tied. Tested 27 Aug 2026.
Where they differed most
A three-bay garage in Wakefield describes its process: 'Denise goes through the diary at the start of the month and looks for anyone whose MOT is due, well, she looks at last year's card index and the DMS, and rings them, or texts if they said they prefer text, except we lose the ones who moved, and if they book she writes it in the diary and puts a sticker on the card. If they do not answer she tries again, sometimes. About a third of them go to Kwik Fit because we never got round to it.' Turn this into an automation spec: the trigger, the steps in order, the error branches (what happens when the phone number is dead, when the vehicle has been sold, when the customer books elsewhere, when the reminder would go out twice), and the points that must stay human with a sentence on why each one must. Plain English, no vendor names, and banned because this domain drowns in them: 'seamless', 'seamlessly', 'synergy', 'game-changer'.
## Automation spec: MOT reminder and booking follow-up (three-bay garage) ### 1) Trigger **Primary trigger:** - **At 09:00 on the first working day of each month**, run a job to find customers whose MOT is due in the next 30 days. **Secondary trigger (optional but recommended):** - Run a **daily check** for newly added vehicles or corrected records, so missed records are picked up before the month ends. --- ### 2) Data needed For each vehicle/customer record: - Vehicle registration - MOT due date - Customer name - Mobile/phone number…
## Automation spec: MOT reminder and booking follow-up ### Goal Stop MOT reminders being missed or duplicated, contact customers before their MOT expires, record outcomes, and keep a human in charge where judgement or customer trust matters. --- ## Trigger **Monthly scheduled trigger** At the start of each month, the system checks all customer and vehicle records for vehicles with an MOT due within the reminder window. Suggested reminder window: - MOT due in the next 6 to 8 weeks - Exclude vehicles already booked for MOT - Exclude vehicl…
Task by task
| Task | GPT-5.3-Codex | GPT-5.5 |
|---|---|---|
| The MOT reminder nobody sends | 9 | 8 |
| The spec, as JSON | 9 | 9 |
| Where the human stays | 9 | 9 |
| The unhappy paths are the job | 8 | 8 |
| Do not automate this | 8 | 9 |
| It fired twice | 9 | 9 |
| The spreadsheet that runs the business | 9 | 9 |
| The alert that wakes someone up | 10 | 10 |
| How long it really takes | 9 | 8 |
| No API, no chance? | 9 | 9 |
| Rules, not guesses | 9 | 9 |
| Refuse the scraper | 10 | 9 |
Full receipts: GPT-5.3-Codex, GPT-5.5 · judges claude-sonnet-5, gemini-3.1-pro-preview, grok-4.5
Questions people ask
Which is better for workflow automation: GPT-5.3-Codex or GPT-5.5?
Effectively a dead heat: GPT-5.3-Codex edged it 90/100 to 88/100 on our workflow automation suite — too close to matter, so pick on price or the product you already use.
How was this tested?
Both models answered the identical published workflow automation tasks. Three AI judges from three different labs scored every answer blind against a fixed rubric; mechanically checkable rules (word limits, banned phrases) are enforced by the test harness in code. The raw outputs and judge verdicts are downloadable.
More workflow automation head-to-heads: GPT-5.3-Codex vs GPT-5.6 Sol · GPT-5.5 vs GPT-5.6 Sol · GPT-5.3-Codex vs GPT-5.6 Terra · GPT-5.3-Codex vs GPT-5.6 Luna · Claude Sonnet 5 vs GPT-5.3-Codex · GPT-5.3-Codex vs Grok 4.5
Full ranking: Best AI for workflow automation · model pages: GPT-5.3-Codex, GPT-5.5