Roads and bridges
Cog walks the finished road from one end to the other, every step of it, before telling you it is done.
One unbroken road, with nothing missing and no step you cannot walk up.
Verification
Cog checks their own homework.
A convincing picture is only a start. On supported builds, Cog reads the blocks back, measures the shapes and walks the routes, then tells you what was made, what was checked and what still needs work.
Front wall off. Saying a house is walk-in is easy; Cog walked in, 14 blocks past the wall.
What checking means
Cog reads the world back, block by block
A build can look right from one angle and still be wrong. So Cog reads the actual blocks back out of the world, along with everything standing on them, and checks what a picture cannot show: whether the road is one unbroken shape, whether every gondola sits the same distance from the hub, whether the lamps go dark when the power does. Supported plans get checked before the first block lands too, while problems are still drawings. Each check answers one specific question. None of them proves a build has no faults at all.
What gets checked
What Cog goes back over before saying it is done
The ferris wheel
Every seat gets measured out from the hub, rather than trusted to the drawing. A wheel with one gondola sitting proud of the others is not a wheel.
Every seat true, and it turns without catching.
Anything Cog designed
A design names the block for every place in it before a single one goes down, so Cog can check the whole thing rather than spot-check it.
142,911 of 142,911 blocks read back right across 5 builds. 0 wrong.
Whether you can really go inside
You cannot work this out on paper; we tried. So Cog stops calculating, stands outside, picks the spot deepest inside the building, and walks to it on foot with the same physics you have. Either they are standing in there at the end or they are not.
6 of 8 builds: Cog got in, up to 32 blocks deep. The other 2 had no way in, and the report said so.
A game Cog wrote
Rules with one character wrong load perfectly, report success, and then do nothing at all, forever, without a word. So every rule gets set off on purpose first: a snowball dropped in the goal mouth, a score driven to its winning value, the clock wound to the tick a timer waits for.
6 games, 67 rules, each fired once on purpose. The slowest went live in 1,641 ms.
The hidden door
Cog pulls the lever and watches the wall slide across, then pushes it back and watches the doorway return. Then again, at every width, because a secret door that works once is a hole.
Opening and closing checked at the tested widths.
Redstone
Start with a circuit that has been tested
Redstone is where clever machines fall over: one block out of place and the whole circuit can stop. For supported contraptions, Cog uses a library of circuits that have already been built and checked, then tests the result in the world. That gives Cog a known starting point instead of a fresh guess at the wiring. Read the six wire rules that library is built on.
And if it is not right
Useful answers when a check finds a problem
A broken route, an unexpected block or a rule that did not fire gives Cog a concrete problem to work on, and gives you a clearer picture than a bare “done”.
Cog is instructed to report what they built, which checks ran and what they could not finish. AI can still misunderstand a result or miss a problem. If the world does not match the report, ask a follow-up or send us the details through dashboard Support.
Read next
Where to go next
- How it worksWhat happens between asking and finished.
- What you can ask forThe kinds of job Cog will go and do.
- The six redstone wire rulesThe checks behind the circuit library.