koyu — the version line

koyu 1.0

One line declaring which version of the semantics this file is read under. Six versions are accepted, and this order is the order of old to new.

0.1   0.2   0.3   0.4   0.5   1.0

Omitted, the file is read under the newest version, 1.0. Omitting it does not pin the meaning across tool versions — a file whose meaning must stay fixed writes the line.

Newer means later in that list, not later in the alphabet

1.0 is newer than 0.5. Compared as strings, "0.5" > "1.0", so leaving the comparison to the spelling would make the newest version look like the oldest. The order is always decided by the index in the list above.

How the line is written

Exactly two tokens: koyu <version>.

Written	Result
koyu 1.0	accepted
koyu	koyu takes a version: koyu 1.0
koyu 1.0 latest	Extra tokens on the koyu version declaration: latest
koyu 0.6	Unsupported koyu version: 0.6 (this tool supports 0.1, 0.2, 0.3, 0.4, 0.5, 1.0)

It is declared in the base layer only, and only once.

• In any other layer: The koyu version is declared only in the base layer (the entry)
• Twice: The koyu version is declared once (already 1.0) — declaring the same version twice is also an error. The discipline matches grid: it forbids a silent override decided by composition order
• The position in the file is free; it need not be the first line

An older version is accepted only where the meaning is preserved

A file that declares an older version passes only if it means the same building it meant to a processor of that version. Where the same text would mean a different building, check stops and offers two ways out — write the meaning explicitly, or raise the version.

Four diagnostics say this. All four are errors, and check --json carries the code.

VER01 — a default boundary is derived under 0.1

From 0.2 onward, a touching pair of spaces with regions on the same level gets a derived wall boundary when none is declared. In a file declaring 0.1, such a pair means a different building depending on whether the boundary exists.

A koyu 0.1 file has a touching pair with no declared boundary: /L1/a | /L1/b — in 0.2 a
default wall is derived and the meaning changes. Declare the boundary, or raise the
version to koyu 0.2

The fix: declare the boundary, or raise the version to koyu 0.2 or above.

VER02 — daylight scope was inferred from the type before 0.4

Up to 0.3, the types unit, room, ldk, bedroom and living were inferred to be in scope for the daylight check. From 0.4 the scope is the declaration daylight:1 alone, so a space of one of those types with no daylight silently drops out of the check the moment the version is raised.

A koyu 0.3 file has a room with no daylight: /L1/a — 0.4 does not infer the daylight scope
from the type, so it falls out of the check. Write daylight:1 (in scope) or daylight:0
(out of scope), then raise the version to koyu 0.4

The fix: write daylight:1 (in scope) or daylight:0 (out of scope), then raise the version to koyu 0.4 or above.

VER03 — a 0.5 word in a file declaring 0.4 or older

A processor of 0.4 or earlier does not know the words introduced in 0.5. Where it does not know the word, the shape is simply never generated. There are four.

Word	Where it is written
stair: ramp: escalator: lift:	a vertical circulation on a space
line	a drawn line under a boundary
column	a column declaration
underground:	a level below ground

A koyu 0.4 file uses a 0.5 word: /B1/st carries stair: (a vertical circulation) — raise the
version to koyu 0.5

The fix: raise the version to koyu 0.5 or above.

VER04 — a 1.0 word in a file declaring 0.5 or older

A processor of 0.5 or earlier does not know the composition words introduced in 1.0. It cannot read those lines as words at all, so neither the override nor the removal happens — it silently becomes a different building. There are three.

Word	What it does
over	overrides a space, zone, boundary, level or asset
drop	removes a space, a boundary or a column declaration
+ - = under over	adds to, removes from, or replaces a member of a set (openings, seg, area)

A koyu 0.5 file uses a 1.0 word: over /L1/a name:居室 (a composition override) — raise the
version to koyu 1.0

The fix: raise the version to koyu 1.0.

What the version covers

The version belongs to the language, its semantics and the rules of composition. It promises that what could be read under this version stays readable with the same meaning, and it is counted separately from the version of the implementation. Therefore:

• A change to what the language means raises the version. The same text never starts meaning a different building without one
• Adding a judgement does not move it. Rules about architectural validity live on the koyu validate face, and adding one changes the meaning of no existing file
• Drawing is not covered either. The look of the SVG produced from the same shape may change

The bundled examples are always written at the newest version. A change that raises the version brings the examples along in the same change.