diff --git a/agents/researcher/work/queue-216/BUILD.md b/agents/researcher/work/queue-216/BUILD.md
index 22579ca70..b6dda17f3 100644
--- a/agents/researcher/work/queue-216/BUILD.md
+++ b/agents/researcher/work/queue-216/BUILD.md
@@ -182,3 +182,24 @@ has been thrown; the kill claims are unverified until CLEAR):
 Built, not run. `node --check` has not been run on this round's files (no node before the CLEAR); the
 phase A pass above covered the earlier text only. The commit is local and waits for no gate under Sage's
 sage-2716 instruction, which allows git and docs work only; push and claim wait for Sage's go.
+
+## Round 3: rebase onto 45dca69f6, drift check, hash-pin grep (2026-10-23T18:53:43Z, sage-3576)
+
+Appended; nothing above is edited. Git only; nothing run, nothing pushed. Branch researcher/row216-r4 holds the
+one row 216 commit on 45dca69f6 (origin/refactor, 10-23). Earlier base: 48e450ce8 (row 253).
+
+- Rebase: clean. `git range-diff 48e450ce8..038089e5f 45dca69f6..researcher/row216-r4` shows the commit as `=`.
+- Landed in 48e450ce8..45dca69f6: 1175 files. Path overlap with this row's 7 paths: none. packages/library: no
+  landed file. packages/harness/src/tools.mjs (imported by query-fixture.mjs or the tests): not landed.
+- Hash-pin grep (the item 216 owed): 64-hex in packages/library: none. Positive control: 364 files in
+  packages/*/tests and scripts match 64-hex. Tests and scripts that name library files by path:
+  bus/tests/library.test.mjs and library-sync.test.mjs and bus/src/runtime.mjs import library/src/index.mjs;
+  business/src/business.mjs and its test import library/src/mapping.mjs (unchanged by this row);
+  cli/tests/stack-copy.test.mjs, stack-release-fixture.mjs:310 and stack-release.test.mjs:1991 copy
+  packages/library/src as a tree; scripts/stack-copy.sh:37 copies it; scripts/mosaic:41 runs survey.mjs. None pins
+  a hash of index.mjs, index-build.mjs or query.mjs.
+- bus/src/runtime.mjs landed changes after 48e450ce8 and uses libraryModule by named members (ensureMirror, SLOT,
+  readLibraryFile, libraryStatus, sync, LibraryError, SYNC_INTERVAL_MS) only; the landed diff touches none of them,
+  and this row's two new index.mjs exports (query and index build) are not iterated by any caller.
+- Gate additions for phase B: run bus library.test.mjs and library-sync.test.mjs whole (they import index.mjs), and
+  the cli stack-copy and stack-release tests that copy packages/library/src.