Added error code 42I67 unsupported language feature

modules/ROOT/content-nav.adoc

@@ -261,6 +261,7 @@
 **** xref:errors/gql-errors/42I64.adoc[]
 **** xref:errors/gql-errors/42I65.adoc[]
 **** xref:errors/gql-errors/42I66.adoc[]
+**** xref:errors/gql-errors/42I67.adoc[]
 **** xref:errors/gql-errors/42N00.adoc[]
 **** xref:errors/gql-errors/42N01.adoc[]
 **** xref:errors/gql-errors/42N02.adoc[]

modules/ROOT/pages/errors/gql-errors/42I67.adoc

@@ -0,0 +1,40 @@
+:page-role: new-2025.09
+= 42I67
+
+== Status description
+error: syntax error or access rule violation - unsupported language feature. The query is a valid `CYPHER { <<feat>>2 }` query, but it is run in `CYPHER { <<feat>>1 }`. Consider changing the database default Cypher version using `ALTER DATABASE SET DEFAULT LANGUAGE` or prefix the query with `CYPHER { <<feat>>2 }`.
+
+== Example scenario
+
+For example, when using `LET` in a Cypher 5 query:
+
+[source,cypher]
+----
+CYPHER 5
+LET x = 1
+RETURN x
+----
+
+You will receive an error with GQLSTATUS xref:errors/gql-errors/42001.adoc[42001].
+This error has a cause detailed in xref:errors/gql-errors/42I67.adoc[42I67] and status description:
+
+
+[source]
+----
+error: syntax error or access rule violation - unsupported language feature. The query is a valid `CYPHER 25` query, but it is run in `CYPHER 5`. Consider changing the database default Cypher version using `ALTER DATABASE SET DEFAULT LANGUAGE` or prefix the query with `CYPHER 25`.
+----
+
+As well as a cause detailed in xref:errors/gql-errors/42I06.adoc[42I06] and status description:
+
+[source]
+----
+error: syntax error or access rule violation - invalid input. Invalid input 'LET', expected: 'ALTER', 'ORDER BY', 'CALL', 'USING PERIODIC COMMIT', 'CREATE', 'LOAD CSV', 'START DATABASE', 'STOP DATABASE', 'DEALLOCATE', 'DELETE', 'DENY', 'DETACH', 'DROP', 'DRYRUN', 'FINISH', 'FOREACH', 'GRANT', 'INSERT', 'LIMIT', 'MATCH', 'MERGE', 'NODETACH', 'OFFSET', 'OPTIONAL', 'REALLOCATE', 'REMOVE', 'RENAME', 'RETURN', 'REVOKE', 'ENABLE SERVER', 'SET', 'SHOW', 'SKIP', 'TERMINATE', 'UNWIND', 'USE' or 'WITH'.
+----
+
+
+ifndef::backend-pdf[]
+[discrete.glossary]
+== Glossary
+
+include::partial$glossary.adoc[]
+endif::[]

modules/ROOT/pages/errors/gql-errors/index.adoc

@@ -1067,6 +1067,11 @@ Status description:: error: syntax error or access rule violation - invalid patt
 
 Status description:: error: syntax error or access rule violation - pattern parsing failed. Pattern parsing failed. Make sure that an even number of escapes are used in the pattern.
 
+[role=label--new-2025.09]
+=== xref:errors/gql-errors/42I67.adoc[42I67]
+
+Status description:: error: syntax error or access rule violation - unsupported language feature. The query is a valid `CYPHER { <<feat>>2 }` query, but it is run in `CYPHER { <<feat>>1 }`. Consider changing the database default Cypher version using `ALTER DATABASE SET DEFAULT LANGUAGE` or prefix the query with `CYPHER { <<feat>>2 }`.
+
 [role=label--changed-2025.03]
 === xref:errors/gql-errors/42N00.adoc[42N00]