Refuse a quarantine the record declares nothing about

CONTRIBUTING.md

@@ -125,18 +125,23 @@ borrows nothing writes no such line.
 Some of that a run refuses and some of it it does not, and the difference is
 worth knowing before you lean on any of it. A `borrowed/` directory with no
 `LICENSE` beside it is refused. So is a record declaring `Borrowed:` in an
-experiment that holds no such directory. So is a directory named `borrowed`
+experiment that holds no such directory, and so is the other direction of the
+same disagreement, a `borrowed/` directory in an experiment whose record
+declares no `Borrowed:` at all. So is a directory named `borrowed`
 anywhere else inside an experiment, since `experiments/<slug>/borrowed` is the
 one place a quarantine lives and one is all record `0019` allows. A directory
 of that name inside the quarantine is not refused: what is in there is somebody
 else's code laid out somebody else's way, and this board's rules stop at that
 edge.
 
-What still passes is a `borrowed/` directory in an experiment whose record
-declares nothing, because a field added to the format after
+The direction that reads an undeclared quarantine is refused on the directory
+and never on the absent field, and that is the reason it is allowed to exist.
 [docs/decisions/0013-how-the-record-format-changes.md](docs/decisions/0013-how-the-record-format-changes.md)
-is never refused for being absent. That one is yours to keep rather than the
-gate's.
+says a field added to the format after it is optional and that an absent field
+is never a refusal, and nothing here reads an absence: the subject is a
+directory that is present, and a tree carrying one has already said it borrows
+before any header is opened. An experiment that borrows nothing still writes
+nothing and is still never asked about the field.
 
 Nothing opens the licence file. A green run says the layout and the declaration
 do not contradict each other, and it says nothing about which licence the code

docs/experiment-template.md

@@ -33,7 +33,8 @@ field filled in teaches every new record to declare a value it does not have, an
 almost every experiment borrows nothing. The code itself goes in
 `experiments/<slug>/borrowed/`, which carries its own `LICENSE` naming those
 terms, and a record declaring the field with no such directory is refused, as is
-a borrowed directory with no licence file in it.
+a borrowed directory with no licence file in it and a borrowed directory in an
+experiment whose record declares the field nowhere.
 
 That directory is the only place a quarantine may be, and one is all record
 `0019` allows, so a directory named `borrowed` anywhere else in the experiment
@@ -43,8 +44,10 @@ by whoever wrote it and this board does not rearrange it.
 What that refusal does not do is worth knowing before you rely on it. Nothing
 reads the licence file, so a green run says the layout and the declaration agree
 and says nothing about which licence the code is actually under or whether the
-result may be promoted anywhere. A borrowed directory in an experiment whose
-record declares nothing passes, because an absent field is never refused.
+result may be promoted anywhere. The undeclared quarantine is refused on the
+directory rather than on the missing field, so an experiment that borrows
+nothing is still never asked for one: an absent field is refused nowhere here,
+and what is read is a directory that is there.
 
 Add `Held-back` where the experiment is held back under
 `docs/decisions/0010-a-flaw-in-shipped-software.md`, with the date of the report

internal/check/borrowed.go

@@ -69,6 +69,31 @@ const (
 	// quarantine is undeclared by construction however carefully the header
 	// was written.
 	AQuarantineOutsideThePlaceQuarantinesLive = "quarantine-outside-the-place-quarantines-live"
+
+	// BorrowedDirectoryTheRecordDoesNotDeclare refuses an experiment that holds
+	// a quarantine while its record declares no Borrowed field. That is the
+	// second direction of the disagreement above: the tree says the experiment
+	// borrows and the record says nothing, so the person promoting the work
+	// reads a boundary and finds no source and no licence named anywhere they
+	// would look for one.
+	//
+	// IT IS KEYED ON THE DIRECTORY AND NOT ON THE ABSENT FIELD, and the
+	// difference is the whole reason it may exist. Record 0013 says a field
+	// added to the format after it is optional and that an absent field is
+	// never a refusal, which is why refuseHardware declines the identical shape
+	// one field over. Nothing here reads an absence and refuses it: what is
+	// refused is a directory that is present, and a tree carrying one has
+	// already said it borrows without the header being consulted at all. So
+	// every experiment that borrows nothing goes on writing nothing, which is
+	// the property record 0013 bought and this does not spend.
+	//
+	// WHERE IT DOES NOT REACH. A quarantine somewhere other than
+	// experiments/<slug>/borrowed is not this arm's subject - it is refused by
+	// the arm above, whose repair is to move it, and this one then reads the
+	// moved directory. So an experiment whose only borrowed directory is in the
+	// wrong place is refused once rather than twice, and the second refusal
+	// arrives with the repair rather than beside the defect.
+	BorrowedDirectoryTheRecordDoesNotDeclare = "borrowed-directory-the-record-does-not-declare"
 )
 
 // refuseBorrowed holds an experiment's borrowed quarantine and its record's
@@ -82,13 +107,7 @@ const (
 // record 0019 explicitly leaves undecided. What passes here is a layout and a
 // declaration that do not contradict each other, and nothing further.
 //
-// WHERE IT DOES NOT REACH, in three places rather than one.
-//
-// A borrowed directory in an experiment whose record declares no Borrowed field
-// passes. That is the second direction of the disagreement above and it is a
-// refusal on an absent field, which record 0013 forbids in the words
-// refuseHardware already declines the same shape in. Closing it is a change to
-// that record rather than a wider check here.
+// WHERE IT DOES NOT REACH, in two places rather than three.
 //
 // A Borrowed declaration written with nothing after the colon is a declaration,
 // so the directory half above is read against it, and nothing here asks whether
@@ -141,16 +160,26 @@ func refuseBorrowed(fsys fs.FS, root, inside, record string, data []byte) ([]Ref
 	if err != nil {
 		return refusals, nil
 	}
-	if _, declared := parsed.Field(FieldBorrowed); !declared || held {
-		return refusals, nil
+	_, declared := parsed.Field(FieldBorrowed)
+
+	switch {
+	case declared && !held:
+		refusals = append(refusals, Refusal{
+			Property: RecordBorrowedDeclarationNamesNoDirectory,
+			Subject:  record,
+			Detail: fmt.Sprintf("it declares %s and there is no %s directory in %s, so the record says the experiment borrows and the tree says it does not",
+				FieldBorrowed, BorrowedDir, inside),
+		})
+	case held && !declared:
+		refusals = append(refusals, Refusal{
+			Property: BorrowedDirectoryTheRecordDoesNotDeclare,
+			Subject:  at(root, quarantine),
+			Detail: fmt.Sprintf("it holds code under somebody else's terms and %s declares no %s, so the tree says the experiment borrows and the record says nothing. record 0019 puts the source and the licence in that field",
+				record, FieldBorrowed),
+		})
 	}
 
-	return append(refusals, Refusal{
-		Property: RecordBorrowedDeclarationNamesNoDirectory,
-		Subject:  record,
-		Detail: fmt.Sprintf("it declares %s and there is no %s directory in %s, so the record says the experiment borrows and the tree says it does not",
-			FieldBorrowed, BorrowedDir, inside),
-	}), nil
+	return refusals, nil
 }
 
 // refuseQuarantineElsewhere walks an experiment for a directory named borrowed

testdata/cases/a-borrowed-directory-the-record-does-not-declare/expected

@@ -0,0 +1,4 @@
+directories 1
+records 1
+experiments present
+decisions absent

testdata/cases/a-borrowed-directory-the-record-does-not-declare/expected-refusals

@@ -0,0 +1 @@
+borrowed-directory-the-record-does-not-declare

testdata/cases/a-borrowed-directory-the-record-does-not-declare/near-neighbour

@@ -0,0 +1 @@
+an-experiment-that-borrows-and-declares-it

testdata/cases/a-borrowed-directory-the-record-does-not-declare/tree/experiments/one/EXPERIMENT.md

@@ -0,0 +1,14 @@
+Slug: one
+State: asking
+Question-Written: 2026-01-01
+Needs-Hardware: none
+
+## Question
+
+Does the reference implementation lose a frame when the stream stalls?
+
+## Method
+
+The implementation was read and run from the copy this experiment carries.
+
+## Answer

testdata/cases/a-borrowed-directory-the-record-does-not-declare/tree/experiments/one/borrowed/LICENSE

@@ -0,0 +1,7 @@
+MIT License
+
+Copyright (c) 2026 the author of the borrowed implementation
+
+Permission is hereby granted, free of charge, to any person obtaining a copy of
+this software and associated documentation files, to deal in the software
+without restriction.

testdata/cases/a-borrowed-directory-the-record-does-not-declare/tree/experiments/one/borrowed/source.txt

@@ -0,0 +1 @@
+The borrowed implementation would sit here.