diff --git a/docs/architecture/14-api-contract/openapi.yaml b/docs/architecture/14-api-contract/openapi.yaml
index c0ce041b..ff70302a 100644
--- a/docs/architecture/14-api-contract/openapi.yaml
+++ b/docs/architecture/14-api-contract/openapi.yaml
@@ -1748,10 +1748,33 @@ components:
             - type: string
             - type: 'null'
           description: |
-            Where this book's chapter boundaries came from, passed through from the engine's
-            manifest; `null` while the book is still arriving. ⚠ **Added by the order-form minor
-            (0.11.0)** so a client can tell an order in chapters from an order it must phrase in
-            characters.
+            Where this book's chapter boundaries came from, in the engine's own word, passed through
+            untouched — or `null` when NO MANIFEST HAS BEEN READ FOR THIS BOOK. ⚠ **Added by the
+            order-form minor (0.11.0)** so a client can tell an order in chapters from an order it
+            must phrase in characters.
+
+            ⛔ **`null` IS NOT A VALUE OF THE VOCABULARY AND IT IS NOT `none`.** `none` is a book the
+            engine LOOKED at and found one chapter in — a statement about the book. `null` is the
+            absence of any statement: nobody has asked. The difference is the whole reason a client
+            can tell «there is no provenance» from «there is one, and it is poor», and only the
+            second is a fact about the text.
+
+            ⚠ **And `null` does NOT mean «still arriving».** An earlier edition of this line said so,
+            and it is narrower than the truth. A book reaches `not_started` the moment its parse
+            finishes — and that same transaction leaves it OWING a reading surface, which is what
+            later brings the provenance. So the ordinary state of a freshly parsed book is `cut, and
+            no provenance yet`, and a client that waits for arrival waits for a thing that already
+            happened. Held by `pgstore.TestAParsedBookIsNotStartedBeforeItHasAnyProvenance`.
+
+            ⚠ Two further roads reach the same `null`, and neither is a book in flight: a manifest
+            older than this field leaves the column empty for good, and a book registered from a file
+            already on disk has no manifest at all yet. ⇒ `not_started` says the SOURCE was cut; it
+            does not say a manifest has been read.
+
+            The rendering half — that an absent provenance reaches the client as an explicit `null`
+            rather than a missing member or an invented word, and that a word this build does not
+            know travels VERBATIM — is held separately by
+            `httpapi.TestABooksCutProvenanceIsTheEnginesOwnWordOrAnExplicitNull`.
 
             ⚠ **An OPEN vocabulary that grows additively** — today `declared`, `delimited`, `detected`, `none` (⚠ `delimited` added by the engine 06.09: the file drew a separator — an EPUB spine, a form feed — but calling it a CHAPTER is the engine's assumption, not the format's word).
             A value this build does not know is read as "not recognised" and is never promoted into
@@ -2745,7 +2768,11 @@ components:
             about the book. Held by
             `httpapi.TestABookWhoseCutCannotBeSoldAgainstOffersCharactersAndSaysSo`, which asserts an
             explicit `null` rather than an invented word. ⚠ The sibling `Book.structure` carries the
-            same fact and says the same in its own words; the two cannot disagree.
+            same fact and now says the same in its own words — until 06.09 it did NOT: it called
+            `null` «still arriving» and drew no line between `null` and `none` at all, so the rule
+            lived in the ORDER schema while the field a client reads on the book card was silent
+            about it. «The two cannot disagree» was a statement of intent then; it is a statement
+            about the text now.
 
             ⚠ **An open vocabulary that GROWS additively** — today `declared`, `delimited`, `detected`, `none` (⚠ `delimited` added by the engine 06.09: the file drew a separator — an EPUB spine, a form feed — but calling it a CHAPTER is the engine's assumption, not the format's word).
             A value this build does not know is read as "not recognised" and never promoted into