TL;DR: Both families ran in the same test on Aug 25, 2026, and the wins split. GPT-5.6 Luna is the most faithful model we have tested: all 32 questions of a real customer's sign-up form word for word, and the only working scoring grid that saves scores back into your workspace (Aug 3 and Aug 7, 2026). On Aug 25, 2026 Grok 4.6 saved every answer on that form and landed both follow-up edits, but spent dozens of failed build steps getting there, while GPT-5.6 Terra built the best sign-up form of that test and Luna's first submissions failed. Route by task inside Taskade Genesis rather than standardizing on one.
What TSK-1 Found
Both families ran in the same hands-on app test on Aug 25, 2026, and GPT carries earlier results from Jul 30 through Aug 8. The findings split by measure. GPT is strongest at following a detailed request and finishing quickly. Luna preserves exact wording and can build scoring logic that saves results to your workspace. Terra is the fastest in nearly every test it enters. Grok 4.6 landed both follow-up edits in that test and saved every answer on the 32-question form, slowly and at one of the highest costs in it. Grok Build 0.1 produced no app.
- GPT-5.6 Luna: Aug 3, 2026: reproduced all 32 questions of a real customer's client sign-up form word for word, the only model to get all four of its builds word for word across more than one test. Aug 7, 2026: the only model to build a working scoring grid, 33 rows by 5 ratings, with every score saved straight back into the workspace. Aug 8, 2026: test winner on value, and the only model to explain its own design choices. Aug 25, 2026: its match tracker crashed on the first real entry and its sign-up form rejected the first submission, before later tests finished cleanly.
- GPT-5.6 Terra: Aug 7, 2026: the first model to pass all five checks in one run, and the fastest of the test at 8 minutes 26 seconds. Aug 8, 2026: both builds carried all 32 questions word for word after three tests where none of the four came through. Aug 25, 2026: best overall match tracker and best client sign-up build of the test, with form to saved score working on the first try.
- GPT-5.6 Sol: Jul 30, Aug 1, and Aug 25, 2026: added a sign-in screen the brief never asked for, three times in three tests, and did not say so.
- Grok 4.6: Aug 25, 2026: built a working match tracker with every asked piece, saved all 32 sign-up form answers, and landed both follow-up edits. It spread the form data across ten projects where the leader used two, ended one build without saying it was done, and racked up dozens of failed build steps on each app.
- Grok Build 0.1: Aug 25, 2026: described every layer, then repeated the same failed step hundreds of times until the test was stopped.
See the full evidence at /tsk/grok, /tsk/gpt, and the TSK-1 hub.
Grok 4.6 vs GPT-5.6 Luna
Both models took the same 32-question client sign-up form on Aug 25, 2026. Grok saved every answer that day. Luna's form rejected the first submission, and its record rests on the earlier tests. GPT-5.6 Luna reproduced all 32 questions word for word on Aug 3, 2026. On Aug 8, 2026 it won the test on value and was the only model to explain its own design choices. Then came the Aug 25, 2026 miss: its match tracker crashed on the first real entry and its sign-up form rejected the first submission. Later tests finished cleanly.
Grok 4.6 took the full form on Aug 25, 2026 and saved every answer. It spread that data across ten projects where GPT-5.6 Terra, the leader of that test, used two. The answers are there, in ten places instead of two. Grok also ended a working match-tracker build, every asked piece in place, without telling the user it was done.
The finding in Grok's favor is the follow-up edit on the Aug 25, 2026 test. Both of Grok 4.6's follow-up edits landed that day: a ranked heroes page, and a text score field with next-step suggestions. Luna's standing edit record is the automatic-picking baseline of Aug 19, 2026, an app built in about 11 minutes and edited in about 6. Luna is faster and far cheaper. Both of Grok's edits arrived as asked on Aug 25, 2026. That is one test's result, not a verdict on the family.
Then there is the price of getting there. Dozens of failed build steps on each app made Grok 4.6 one of the slowest and most expensive results of the test. Luna was the value pick on every app in a five-model test of identical prompts on Aug 27, 2026. On published rates the gap runs the same way: Luna is $0.20 in and $1.20 out per million tokens, against Grok 4.6 at $2 and $6.
Grok Build 0.1 and the rest of the GPT-5.6 family
Away from Luna, the split becomes finishing versus not finishing. GPT-5.6 Terra is the fastest model in nearly every test it enters. On Aug 7, 2026 it was the first model to pass all five checks in one run: it built the app, took a form submission, put every answer in the right place, ran the automation, and answered questions about the data. It did that in 8 minutes 26 seconds, the fastest of the test.
Terra's weakness was wording, and it fixed it. For three tests, none of its four builds carried all 32 of the customer's questions word for word. On Aug 8, 2026 a change of setting turned that around: both builds carried all 32 questions word for word. The honest miss on the same day was Terra's premium setting, the worst value we have measured on the client sign-up form: a single page rewritten 19 times. Then on Aug 25, 2026, in the test Grok entered, Terra built the best overall match tracker and the best client sign-up build of the test: form to saved score worked on the first try. That is the leader that used two projects where Grok used ten.
GPT-5.6 Sol is the login-wall lesson. On Jul 30, 2026 it put a sign-in screen in front of an app nobody asked it to lock, and never mentioned it. On Aug 1, 2026 it did the same again. On Aug 25, 2026 it added a sign-in gate to the match tracker, the third time in three tests. We open every app and use it, which is how that was caught.
Grok Build 0.1 is xAI's dedicated builder, priced below Grok 4.6 at $1 in and $2 out per million tokens. In the Aug 25, 2026 test it produced no app. It described every layer it planned to build, then repeated the same failed step hundreds of times until the test was stopped. For building, route to Grok 4.6.
Choose Grok If…
Grok is the better pick in several common cases.
- The app already exists and you need a change to land. Both of Grok 4.6's follow-up edits arrived as asked in the Aug 25, 2026 test: a ranked heroes page, and a text score field with next-step suggestions.
- Every answer has to be saved, and you can tidy the layout later. Grok 4.6 took the full 32-question form and saved every answer (Aug 25, 2026). The ten-project spread is a cleanup job, not lost data.
- Cost matters less than the edit landing. Grok 4.6 was one of the slowest and most expensive results of the Aug 25, 2026 test. If the edit is the deliverable, that is a price some teams will pay.
Choose GPT If…
- The brief is detailed and the wording matters. GPT-5.6 Luna reproduced all 32 questions of a real customer's form word for word, again and again through August 2026, the only model to do so across more than one test.
- The app has to save scores, not just show them. Luna is the only model that built a working scoring grid, 33 rows by 5 ratings, with every score saved straight back into the workspace (Aug 7, 2026).
- Turnaround is the constraint. Terra passed all five checks in one run in 8 minutes 26 seconds (Aug 7, 2026), and Luna's baseline is an app in about 11 minutes and an edit in about 6 (Aug 19, 2026).
- Value on a budget is the job. Luna won the Aug 8, 2026 test on value and was the value pick again on Aug 27, 2026, and its published rate of $0.20 in and $1.20 out per million tokens is the cheapest on this page by a wide margin.
- You need the longest window. OpenAI lists a 1.05M-token context and 128K max output for every GPT-5.6 variant, more than double Grok 4.6's 500K.
The Taskade Angle: Route, Don't Standardize
Most comparison pages end with "pick one". The evidence for these two closed families points the other way: one owns detailed requests and fast delivery, the other landed both follow-up edits in the Aug 25, 2026 test. Serious teams run both and route between them.
Taskade routes across 15+ frontier models from OpenAI, Anthropic, and open-weight providers inside one workspace, with the AI allowance included in the subscription rather than a separate API account per lab. Paid plans start at Pro $10/mo billed annually, with Business $25, Max $100 and Enterprise $250 per month billed annually. You set the model per agent or per automation step, so a first build on GPT-5.6 Luna, a fast turnaround on Terra, and a follow-up edit on Grok 4.6 can each get the model with the result to back it. Leave a step on TSK-1 Auto and it adapts the depth instead: fast when the step is quick, deeper reasoning when it is not.
Four patterns that hold up:
- Faithful model builds, edit model changes. First builds from a detailed brief on Luna. Follow-up edits to the finished app on Grok 4.6, where both changes landed on Aug 25, 2026.
- Fast model drafts, faithful model checks the wording. A quick first pass on Terra, then a Luna pass on the steps where exact wording is the deliverable.
- Every step lands in the same project graph. Whichever model runs a step, the result becomes shared workspace memory, so the next agent inherits context instead of re-deriving it.
- Scheduled automations read from the same place. Model choice becomes a per-step setting, not a platform decision.
Routing Grok 4.6 to the edit step, where both of its edits landed on Aug 25, 2026, keeps the win and skips the cost of a whole build.
Final Word: Edits That Land vs Every Word Kept
Grok 4.6 is the edit pick from the Aug 25, 2026 test: both follow-up changes arrived as asked and its form saved every answer, at one of the highest costs in that test. GPT-5.6 is the fidelity-and-speed pick: Luna kept all 32 questions word for word and built the only working scoring grid, Terra was the fastest, the first to pass every check in one run, and the leader of the Aug 25, 2026 test, and Sol is the reminder to open every app before you trust it.
Neither is the winner. The winner is the setup that puts fidelity where the brief is detailed and a proven edit where the app already exists.
▲ Memory feeds Intelligence. ■ Intelligence triggers Execution. ● Execution creates Memory. Two closed families. One workspace. No single point of vendor failure.
This is the origin of living software. 🌱
Build with Grok and GPT in one workspace →
Related reading
- 10 Best Open-Source AI LLMs in 2026 - How the closed labs compare with the open-weight field.
- Grok vs Claude - The same xAI family against Anthropic.
- GPT vs Claude - The other closed-family head-to-head.
- DeepSeek vs ChatGPT - Open-weight value against OpenAI.
- Multi-Model AI Access - How Taskade routes across providers.
- TSK-1 Grok profile - Full evidence for the Grok family.
- TSK-1 GPT profile - Full evidence for the GPT family.
- TSK-1 hub - The complete model test dataset.
