diff --git a/modules/mesh-catalog/heard.ts b/modules/mesh-catalog/heard.ts
index daff5043..4dab234f 100644
--- a/modules/mesh-catalog/heard.ts
+++ b/modules/mesh-catalog/heard.ts
@@ -37,6 +37,12 @@ export interface Built {
   /** A pull request's merge check or a branch tried before one (to-be 45 §9, issue 686): nothing merged. */
   "check-outcome"?: unknown;
   check?: unknown;
+  /** The repository's default branch as the build seat read the forge at the build (ADR 0238); empty from a seat older than the rule. */
+  trunk?: string;
+  /** Whether the commit is on `trunk`. */
+  "on-trunk"?: boolean;
+  /** The branches the commit is on. */
+  branches?: string[];
 }
 
 /** The events a build outcome reaches this module on: the build seat's, as it happens, and the control plane's replay. */
@@ -54,9 +60,19 @@ export const BUILD_EVENTS = [
 /**
  * Whether a build outcome is a module-version to place in the graph, and why not when it is not.
  *
- * The same rule the controller keeps when it takes a build in: a merge check, a try and a dry run built
- * nothing that merged, and a failure made nothing. Placing any of them would make an unmerged head the
- * version the catalogue calls current.
+ * It mirrors two of the rules the controller keeps before it registers a build (mesh-controller
+ * cmd/mesh-controller/main.go `builds.Built`, build.go `publishable`): a merge check, a try and a dry run are
+ * never published, and **only a commit on its repository's trunk is** (ADR 0238) — a branch built through
+ * the `build` verb is checked, never a module's version. Where the seat names no trunk (one older than the
+ * rule) it is placed, as the controller lets it through. A failure made nothing and is passed over too.
+ *
+ * Not mirrored, because the catalogue cannot see what they read: the branch a module follows when it is not
+ * the default one (the controller's `follows`; such a module's builds off the default branch are passed over
+ * here and reach the graph by the replay), ADR 0266's rule that a module registers only from the repository
+ * it is built from, a superseded request, a build in the scratch namespace, one that failed its gate, and a
+ * build whose source is unchanged. Each needs the controller's records. This is safe for what the mesh
+ * sends, which is chosen from the controller's own module table and never from this graph; that the graph
+ * can still hold a build the controller refused under those rules is a follow-up (hq issue 712).
  */
 export function placeable(body: Built):
   | { placed: "yes"; module: string; commit: string }
@@ -70,6 +86,9 @@ export function placeable(body: Built):
   if (body.failed) {
     return { placed: "no", why: "a failed build made no module-version", fault: false };
   }
+  if (body.trunk && !body["on-trunk"] && !(body.branches ?? []).includes(body.trunk)) {
+    return { placed: "no", why: `the commit is not on its repository's trunk ${body.trunk}: checked, never published (ADR 0238)`, fault: false };
+  }
   if (!body.module || !body.commit) {
     return { placed: "no", why: "it named no module or no commit", fault: true };
   }
diff --git a/modules/mesh-catalog/test/heard.test.ts b/modules/mesh-catalog/test/heard.test.ts
index c2630f9e..e00daa1b 100644
--- a/modules/mesh-catalog/test/heard.test.ts
+++ b/modules/mesh-catalog/test/heard.test.ts
@@ -11,6 +11,9 @@ const walkBuild = {
   path: "modules/mailu",
   ref: "main",
   on: "shanks",
+  trunk: "main",
+  "on-trunk": true,
+  branches: ["main"],
   module: "mailu",
   commit: "e1c8965ddbf1cf9af9cf1eed7a72ae9ffa6d5a87",
   manifest: { module: "mailu", unhealthy: { severity: "urgent", why: "mail stops" } },
@@ -52,3 +55,18 @@ test("an outcome that names no module or commit is said as the builder's fault",
   assert.equal(placing.placed, "no");
   if (placing.placed === "no") assert.equal(placing.fault, true);
 });
+
+test("a branch built through the build verb is passed over; a commit on the trunk, or from a seat that names none, is placed (ADR 0238)", () => {
+  const branch = { ...walkBuild, ref: "feature", "on-trunk": false, branches: ["feature"] };
+  const placing = placeable(branch);
+  assert.equal(placing.placed, "no");
+  if (placing.placed === "no") {
+    assert.match(placing.why, /not on its repository's trunk main/);
+    assert.equal(placing.fault, false);
+  }
+  // On the trunk by its branches although the seat did not set on-trunk.
+  assert.equal(placeable({ ...branch, branches: ["feature", "main"] }).placed, "yes");
+  // A seat older than the rule says no trunk: placed, as the controller lets it through.
+  const { trunk, "on-trunk": _on, branches, ...older } = walkBuild;
+  assert.equal(placeable(older).placed, "yes");
+});