@@ -87,6 +87,18 @@ test('runtime snapshot upgrades an absent truncation flag only for producers tha
   }
 });
 
+test('runtime snapshot leaves truncation unknown for a producer this host does not list', async () => {
+  // A plugin built against another release can name a producer this host has no registry row for.
+  const producer = 'future-ios-tree' as IosSnapshotProducer;
+  const device = createSnapshotOnlyDevice({
+    snapshot: { nodes: [], backend: 'xctest', producer, createdAt: 1 },
+  });
+
+  const result = await device.capture.snapshot({ session: 'default' });
+
+  assert.equal(result.truncated, undefined);
+});
+
 test('runtime snapshot recognizes equivalent bounds and still updates its baseline', async () => {
   let stored: Parameters<CommandSessionStore['set']>[0] | undefined;
   let rect = { x: 10, y: 20, width: 100, height: 40 };
 
@@ -254,7 +254,8 @@ function snapshotAppFields(capture: SnapshotCapture): {
 function snapshotTruncationForResult(snapshot: SnapshotState): boolean | undefined {
   if (snapshot.truncated !== undefined) return snapshot.truncated;
   if (snapshot.backend !== 'xctest' || snapshot.producer === undefined) return false;
-  return snapshotProducerFacts(snapshot.producer)?.truncation === 'unavailable' ? undefined : false;
+  // A producer this host does not list cannot vouch for truncation, so it stays unknown too.
+  return snapshotProducerFacts(snapshot.producer)?.truncation === 'available' ? false : undefined;
 }
 
 function buildSnapshotWarnings(params: {
Original file line number	Diff line number	Diff line change
`@@ -254,7 +254,8 @@ function snapshotAppFields(capture: SnapshotCapture): {`
`254`	`254`	`function snapshotTruncationForResult(snapshot: SnapshotState): boolean \| undefined {`
`255`	`255`	`if (snapshot.truncated !== undefined) return snapshot.truncated;`
`256`	`256`	`if (snapshot.backend !== 'xctest' \|\| snapshot.producer === undefined) return false;`
`257`		`- return snapshotProducerFacts(snapshot.producer)?.truncation === 'unavailable' ? undefined : false;`
	`257`	`+ // A producer this host does not list cannot vouch for truncation, so it stays unknown too.`
	`258`	`+ return snapshotProducerFacts(snapshot.producer)?.truncation === 'available' ? false : undefined;`
`258`	`259`	`}`
`259`	`260`
`260`	`261`	`function buildSnapshotWarnings(params: {`