GPT-5.6 Luna vs Grok 4.5 for social media posts

The verdict

GPT-5.6 Luna wins, 98–93

Same 12 social media posts tasks, marked blind by three rival labs. GPT-5.6 Luna took 3 tasks, Grok 4.5 took 1, 8 tied. Tested 16 Aug 2026.

Where they differed most

The task — X thread that earns its length

Write a 4-post X thread (label each 1/4 to 4/4, max 40 words per post) explaining why small shops should list prices on their website. Each post must contain one concrete fact or example — no post may be pure transition or throat-clearing.

GPT-5.6 Luna10/10

**1/4** A posted price answers “Can I afford this?” before a customer calls. Example: a bakery listing custom cakes “from $28” filters out mismatched inquiries and attracts shoppers ready to order.

**2/4** Transparent pricing builds trust. A repair shop showing a $75 diagnostic fee feels more credible than one requiring every visitor to call before revealing any cost.

**3/4** Prices help mobile shoppers decide quickly. A plumber listing “drain clearing from $149” gives visitors enough information to compare options instead of leaving for a cl…

Grok 4.56/10

1/4 Customers expect prices. Nielsen data shows 59% of shoppers prefer brands transparent on costs. Small shops build instant trust by listing them, matching what buyers already see from larger rivals.

2/4 It saves staff time. One hardware store cut “how much?” calls 50% after adding website prices, letting employees focus on in-person help and higher-value service instead of repeating basics.

3/4 Conversions rise fast. A boutique clothing shop saw online revenue jump 35% in three months once prices appeared—browsers turned into buyers when t…

Task by task

Task	GPT-5.6 Luna	Grok 4.5
LinkedIn without the cringe	10	10
X thread that earns its length	10	6
Announce without announcing	10	10
Turn a review into a post	9	9
Disagree agreeably	10	10
The unsexy business	10	10
Say less	10	10
Hook without bait	10	9
Post about a mistake	10	8
Event post with the facts	9	10
Know when not to post	10	10
Refuse the astroturf	10	10

Full receipts: GPT-5.6 Luna, Grok 4.5 · judges claude-sonnet-5, gemini-3.1-pro-preview, grok-4.5

Questions people ask

Which is better for social media posts: GPT-5.6 Luna or Grok 4.5?

GPT-5.6 Luna — it scored 98/100 against 93/100 on our 12-task social media posts suite, winning 3 tasks to 1 with 8 tied. Every answer was marked blind by three judges from three rival AI labs.

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 Luna vs GPT-5.6 Sol · GPT-5.6 Sol vs Grok 4.5 · GPT-5.6 Luna vs GPT-5.6 Terra · GPT-5.6 Terra vs Grok 4.5 · GPT-5.3-Codex vs GPT-5.6 Luna · GPT-5.3-Codex vs Grok 4.5

Full ranking: Best AI for social media posts · model pages: GPT-5.6 Luna, Grok 4.5