Developer reference

Developer reference

This page describes main, which the nightly build is made from. The latest release is 0.7.0: ✅ is in it, 🌙 is only in the nightly build, 🟡 is being built and ⏳ is planned.

The numbers and lists a plug-in, a host or a tool that reads graph notes is built against.

Versions

Interface	Version	Changes when
Plug-in interface (PLUGIN_API)	1	A plug-in built for another version is refused.
Host interface (HOST_CONTRACT_VERSION)	3	Every change to DisplayHost.

Problem codes

Every problem the reader raises has a stable code, the same in JavaScript and Python, and given as the Language Server Protocol diagnostic code. A code is never reused. Each {name} is filled in by the problem.

Code	Problem	Fix	Spec	Raised by
GN101	the block names no graph	start it with '// graph: <name>' (§3)	§3	JavaScript, Python
GN102	the graph name '{name}' is not one word	use letters, digits and underscores only — reader_choice, not reader-choice (§3)	§3	JavaScript, Python
GN103	a comment must be on a line of its own: // also occurs inside identifiers, such as ni:/// hashes (§3)	put the comment on its own line	§3	JavaScript, Python
GN104	cannot read '{text}'	a data block holds only nodes, relationships and simple values	—	JavaScript, Python
GN105	'{escape}' is not an escape GQL names	double the backslash to write a backslash: \{escape}	—	JavaScript, Python
GN201	expected '{expected}', found '{found}'	keep to the document profile (§3)	§3	JavaScript, Python
GN202	expected a name, found '{found}'	keep to the document profile (§3)	§3	JavaScript, Python
GN203	'{text}' is not a date	write DATE 'YYYY-MM-DD'	—	JavaScript, Python
GN204	'{text}' is not an instant	write DATETIME 'YYYY-MM-DDTHH:MM:SS+HH:MM'	—	JavaScript, Python
GN205	'{text}' has no offset	an instant carries its offset (§9, principle 11)	§9	JavaScript, Python
GN206	'{text}' is not an instant: in UTC it falls outside years 1 to 9999	write DATETIME 'YYYY-MM-DDTHH:MM:SS+HH:MM' within years 1 to 9999	—	Python
GN207	'{token}' is not a value in the profile	use 'text', a number, TRUE, FALSE, DATE '…' or DATETIME '…' — no lists, no expressions	—	JavaScript, Python
GN208	id {written} is not text	write id: {quoted} — a node's id is always text (§3)	§3	JavaScript, Python
GN209	SET would change {var}'s id, and a node's id never changes (§3)	write the right node, then link {var} to it or supersede it (§12)	§3	JavaScript, Python
GN210	unexpected '{token}'	a data block ends after its INSERT and SET (§3)	§3	JavaScript, Python
GN301	[{written}] has no colon, and graph {graph} has no relationship type called {written}	a relationship type is written with its colon: [:{type}]	—	JavaScript, Python
GN302	[{written}] has no colon, and graph {graph} has relationship types {types} and {last}, which differ only by case	write the one meant with its colon, such as [:{type}]	—	JavaScript, Python
GN303	this is a query block	queries ask questions of a graph; they are not data	—	JavaScript, Python
GN304	this is an excerpt	an excerpt illustrates part of a graph; it is not data	—	JavaScript, Python
GN305	MATCH must find a node by its id alone	write MATCH (v:Label {id: '…'})	—	JavaScript, Python
GN306	MATCH finds no {labels} with id '{id}' in graph {graph}	the node must be written earlier — in this document or one loaded before it	—	JavaScript, Python
GN307	{var} is written twice	give each new node its own variable	—	JavaScript, Python
GN308	id '{id}' is already a node in graph {graph}	an id names one node (§10) — MATCH it to add to it, or supersede it (§12)	§10	JavaScript, Python
GN309	{var} is used before it is written	write the node before any relationship that uses it — GQL binds a name only once its node is written (§3)	§3	JavaScript, Python
GN310	no thing called {var} in graph {graph}	check the spelling — or write it here with its kind: ({var}:Kind {…})	—	JavaScript, Python
GN311	SET names {var}, which is no thing in graph {graph}	check the spelling — SET names a thing by its id	—	JavaScript, Python
GN401	a target is named by its id alone	write MATCH (v:Kind {id: '…'}) — a thing by its name, a link by its two ends and its type	—	JavaScript, Python
GN402	a link is named by its type	write [r:TYPE] — a link by its two ends and its type	—	JavaScript, Python
GN403	a link is named by its two ends and its type alone	leave its values to a SET	—	JavaScript, Python
GN404	this names more than one target	a DELETE or SET names exactly one target (§24)	§24	JavaScript, Python
GN405	{var} is not the one target	a DELETE or SET names exactly one target (§24)	§24	JavaScript, Python
GN406	a DELETE needs the target it removes	write MATCH (v:Kind {id: '…'}) DELETE v	—	JavaScript, Python
GN407	DETACH is followed by DELETE	write DETACH DELETE v	—	JavaScript, Python
GN408	this removes more than one target	a DELETE or SET names exactly one target (§24)	§24	JavaScript, Python
GN409	unexpected '{token}'	a DELETE ends after the one target it removes	—	JavaScript, Python
GN410	a link has no links to detach	write DELETE r	—	JavaScript, Python
GN411	a change is a DELETE or a SET	write DELETE or SET after the MATCH	—	JavaScript, Python
GN412	this changes more than one target	a DELETE or SET names exactly one target (§24)	§24	JavaScript, Python
GN413	SET would change {var}'s id, and a node's id never changes (§3)	write the right node, then supersede it (§12)	§3	JavaScript, Python
GN414	{key} is not a name a SET may give a value to	choose another name for the value	—	JavaScript, Python
GN415	unexpected '{token}'	a SET ends after its values	—	JavaScript, Python
GN416	the block names graph {named}, but the base gives it as graph {graph}	give it as graph {named} — a block is loaded into the graph its first line names (§3)	§3	Python
GN501	id '{id}' is already a node	an id names one node (§10) — MATCH it to add to it, or supersede it (§12)	§10	Python
GN502	cannot find where {var} is written	write it as (name:Kind {…})	—	Python
GN503	[{written}] has no colon	an engine is given only corrected text — read the block with its graph and load Store.corrected(block), or write it with its colon: [:{type}]	—	Python

Standard schemas

A graph can name one in its first line, such as // graph: reader · schema decision@1, and needs no schema of its own.

Schema	What it is for
decision@1	The standard schema for a decision: a question, the options that answer it, and the reasons for and against each.

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Made from packages/graph-spec/src/reader/problem-codes.json, the core and its contracts at d0d6f56 on 19 Oct 2026. This page is generated: change the repository, not this page, as edits here are overwritten.