GPT-5.3-Codex vs GPT-5.6 Terra for social media posts

The verdict

Dead heat: 99 each

Same 12 social media posts tasks, marked blind by three rival labs. Tested 16 Aug 2026.

Where they differed most

The task — LinkedIn without the cringe

Write a LinkedIn post (max 120 words) from a plumber who just hired their first apprentice. Warm, specific, zero corporate speak: banned words are 'thrilled', 'delighted', 'game-changer', 'journey'. No exclamation marks. End with a plain question to the reader.

Today I hired my first apprentice, Sam, 17, from the local college.

This morning we loaded the van at 7, sorted copper fittings, and talked through how to leave a customer’s kitchen cleaner than we found it. On the first call, he watched me trace a hidden leak under a sink, then had a go cutting and deburring pipe on his own.

I started out carrying someone else’s toolbox, so it feels good to pass that on properly, with patience and clear standards.

If you’ve trained someone before, what’s one habit worth teaching on day one?
Today I hired my first apprentice.

His name is Sam. He turned up early, asked where the tea bags were, and spent the morning learning why a slow drain is rarely “just a slow drain.”

I remember being the new person on site: carrying tools, watching closely, trying not to flood anything.

This feels like a big step for my little plumbing business. More than extra hands, it’s a chance to pass on the habits that matter: turn up, protect the customer’s home, explain the problem clearly, and do the job properly.

Who gave you your first real break…

Task by task

TaskGPT-5.3-CodexGPT-5.6 Terra
LinkedIn without the cringe1010
X thread that earns its length1010
Announce without announcing1010
Turn a review into a post99
Disagree agreeably1010
The unsexy business1010
Say less1010
Hook without bait1010
Post about a mistake1010
Event post with the facts1010
Know when not to post1010
Refuse the astroturf1010

Full receipts: GPT-5.3-Codex, GPT-5.6 Terra · judges claude-sonnet-5, gemini-3.1-pro-preview, grok-4.5

Questions people ask

Which is better for social media posts: GPT-5.3-Codex or GPT-5.6 Terra?

They tied at 99/100 on our social media posts suite — for this job, pick on price or the product you already use.

How was this tested?

Both models answered the identical published social media posts 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 social media posts head-to-heads: GPT-5.6 Sol vs GPT-5.6 Terra · GPT-5.3-Codex vs GPT-5.6 Sol · GPT-5.6 Luna vs GPT-5.6 Terra · Claude Opus 4.8 vs GPT-5.6 Terra · GPT-5.5 vs GPT-5.6 Terra · DeepSeek V4 Pro vs GPT-5.6 Terra

Full ranking: Best AI for social media posts · model pages: GPT-5.3-Codex, GPT-5.6 Terra