diff --git a/CONTEXT.md b/CONTEXT.md
index f443ea245..5bba9c4d5 100644
--- a/CONTEXT.md
+++ b/CONTEXT.md
@@ -544,6 +544,10 @@ The canonical lint infrastructure adopted in ADR 452 (`docs/adr/452-eslint-lint-
 `DEFECT.INVENTORY-DRIFT.examples=#3309 planner-human-verify-mode.md (caught by tests/inventory-counts.test.cjs + tests/inventory-manifest-sync.test.cjs)`
 `DEFECT.INVENTORY-DRIFT.detect=tests/inventory-* fails with "References (N shipped) disagrees with filesystem" or "New surfaces not in manifest"`
 `DEFECT.INVENTORY-DRIFT.fix-forward=update INVENTORY.md headline count + row entry + footnote count; run node scripts/gen-inventory-manifest.cjs --write to regen INVENTORY-MANIFEST.json; only families.workflows is canonical (top-level workflows key is stale)`
+`DEFECT.INVENTORY-MERGE-UNDERCOUNT.symptom=docs/INVENTORY.md "## CLI Modules (N shipped)" (and the other family headlines) is an ABSOLUTE count of gsd-core/bin/lib/*.cjs, NOT a delta; two branches that each add a module both bump N->N+1, so merging them keeps N+1 while the merged filesystem has N+2`
+`DEFECT.INVENTORY-MERGE-UNDERCOUNT.detect=tests/inventory-counts.test.cjs HARD-FAILS ("CLI Modules (N shipped) matches gsd-core/bin/lib/", "headline counts match the filesystem") on the CI MERGE-COMMIT across ALL platforms (macos/ubuntu/windows) even though the branch passed local gsd-test; gsd-test runs the branch ALONE, CI tests branch MERGED with current next, so concurrent module-adds on next are invisible locally (hit #844, #1059)`
+`DEFECT.INVENTORY-MERGE-UNDERCOUNT.fix-forward=after merging origin/next into ANY branch that adds/removes an inventoried artifact (bin/lib module, references/*, workflows/*), rebuild then RE-DERIVE the count from "ls gsd-core/bin/lib/*.cjs | wc -l" (plus per-family counts), set the INVENTORY.md headline to match, run node scripts/gen-inventory-manifest.cjs --write; NEVER trust the merged headline integer`
+`DEFECT.INVENTORY-MERGE-UNDERCOUNT.prevention=for any module-adding branch, merge origin/next + reconcile INVENTORY BEFORE EVERY push (not only at branch creation); the longer the branch lives the more certain the drift`
 
 `DEFECT.AGENT-FILE-SIZE-CAP-BREACH.symptom=adding to agents/gsd-planner.md (or other large agent files) exceeds the 45K char extraction-evidence threshold`
 `DEFECT.AGENT-FILE-SIZE-CAP-BREACH.state=gsd-planner.md is already 49,121 chars on main (over 45K); test fails on main; net-new content makes it strictly worse`