diff --git a/.changeset/17464-knowledge-source-docblock-runtime-registration.md b/.changeset/17464-knowledge-source-docblock-runtime-registration.md
new file mode 100644
index 0000000000..73f8462695
--- /dev/null
+++ b/.changeset/17464-knowledge-source-docblock-runtime-registration.md
@@ -0,0 +1,51 @@
+---
+'@objectstack/spec': patch
+---
+
+`KnowledgeSourceSchema`'s docblock stops claiming it is stored as metadata "exactly like a view or a flow", and says where a knowledge source actually lives
+
+The docblock above `KnowledgeSourceSchema` declared, verbatim:
+
+> Canonical KnowledgeSource. Stored as metadata, versioned, and
+> environment-scoped exactly like a view or a flow.
+
+None of the three is true, measured on the tree this changeset lands on:
+
+- `listMetadataTypeSchemaTypes()` returns **26** governed metadata types and
+  **none is knowledge-shaped**. Controls that fire: `view`, `flow`, `skill`,
+  `agent` and `tool` are all present; a `zzz_nonsense` dark control is absent.
+- `ObjectStackDefinitionSchema` has **44** top-level keys, none knowledge-shaped
+  (controls present: `skills`, `agents`, `tools`, `views`, `flows`).
+- `defineStack({ knowledgeSources: [...] })` is refused with the **generic**
+  unrecognized-top-level-key message — byte-identical to the message for
+  `zzz_nonsense`. Lit control: `defineStack({ skills: [<valid skill>] })` is
+  accepted on the same base, so the probe does find an authoring route for a
+  type that has one.
+
+So an author who followed the sentence reached for a mounting that does not
+exist and got a rejection that pointed nowhere — the authoring trap, not a
+wrong example.
+
+**The prose was the outlier, not the schema.** No ADR in this repo mentions
+`KnowledgeSource` at all, and the rest of the contract is already consistent:
+`IKnowledgeService` declares `registerSource` / `unregisterSource` /
+`listSources` / `getSource`, `KnowledgeServicePlugin` takes a `sources` option
+at kernel wiring and calls `registerSource` for each, and the implementation
+holds them in a process-lifetime `Map`. The `agent.knowledge` liveness row says
+the same thing from the other side — *"restrict retrieval at the
+knowledge-service/source level; describe grounding in `instructions`"*.
+
+The replacement docblock states what the schema is (the shape of a runtime
+registration), names both routes a source actually arrives by, and says the
+retrieval restriction is per-source at the service level.
+
+⛔ No behaviour, no key and no accept set changes: the diff is one docblock.
+Running `gen:schema` and `gen:docs` afterwards produced no artefact change —
+`content/docs/references/ai/knowledge-source.mdx` mirrors the file-level header
+docblock, not this per-schema one.
+
+**Why this is not `skip-changeset`.** `@objectstack/spec`'s published `files[]`
+ships `dist` *and* `src/**/*.zod.ts`, so this text is published twice over: the
+old sentence was measured in the built `dist/knowledge-document.zod-*.d.ts` and
+`.d.mts` (1 occurrence each) before the edit, and the source file is shipped
+verbatim. Both move.
diff --git a/packages/spec/src/ai/knowledge-source.zod.ts b/packages/spec/src/ai/knowledge-source.zod.ts
index 4d8eb8d1dd..afaebc0824 100644
--- a/packages/spec/src/ai/knowledge-source.zod.ts
+++ b/packages/spec/src/ai/knowledge-source.zod.ts
@@ -102,8 +102,24 @@ export const KnowledgeSourceKindSchema = lazySchema(() => z.discriminatedUnion('
 ]));
 
 /**
- * Canonical KnowledgeSource. Stored as metadata, versioned, and
- * environment-scoped exactly like a view or a flow.
+ * Canonical KnowledgeSource — the shape of a **runtime registration**,
+ * ⛔ not a governed metadata type.
+ *
+ * It is not stored as metadata, not versioned and not
+ * environment-scoped: no knowledge-shaped entry exists in the governed
+ * metadata-type registry (`listMetadataTypeSchemaTypes()`), and
+ * `ObjectStackDefinitionSchema` carries no collection for it — so
+ * `defineStack({ knowledgeSources: [...] })` is refused as an
+ * unrecognized top-level key. `view`, `flow`, `skill`, `agent` and
+ * `tool` are the types that do work that way; this one does not.
+ *
+ * A source reaches the runtime through code, for the life of the
+ * process: `KnowledgeServicePlugin({ sources: [...] })` at kernel
+ * wiring, or `IKnowledgeService.registerSource(source)` afterwards;
+ * `listSources()` / `getSource()` read that in-memory registry back.
+ * Retrieval is restricted at the knowledge-service/source level —
+ * `search_knowledge` takes `sourceIds` — and an agent describes its
+ * grounding in `instructions`.
  */
 export const KnowledgeSourceSchema = lazySchema(() => z.object({
   /** Stable identifier. Snake_case. */