diff --git a/AGENTS.md b/AGENTS.md
index f8033bc..b10cd85 100644
--- a/AGENTS.md
+++ b/AGENTS.md
@@ -139,6 +139,7 @@ The only bytes it writes of its own are the two generated pages and
 | `pull [--project KEY] [--dry-run]` | **the laptop leg** — pull every active project through its own `sync_cli`, then run its `jobs` verb where it has one and show the output verbatim. It writes nothing. It runs on the laptop only: a project's `local_path` exists on one machine, so where none is present it exits **2**, names each missing root and says "this is not the laptop — run `checkin` here and `pull` on the laptop"; where some are present it pulls those and lists the rest as skipped. `--dry-run` reaches nothing |
 | `checkin [--dry-run \| --apply] [--push \| --no-push] [--project KEY]` | **the check-in** — the one door, on any surface: stamp `checkin.yaml`, re-render the board, push the ledger where the rule allows, and summarise **by project** (Now, the runs as the ledger holds them, the last five entries, the commands you are likely to type next). It shells out to no sync CLI. `--dry-run` is the default and writes nothing; `--skip-pull` is accepted and ignored with a notice |
 | `census [--json]` | what the Cortex is holding, by project — the one-screen answer |
+| `drift [--science-root PATH] [--json]` | **the laptop leg** — where `projects.yaml` and the Science tree disagree: unregistered project folders, rows whose folder is gone, category vs status, `ral_root` category. Reads, never writes; exit **1** on an error-severity finding; a one-line skip off the laptop. `census` and `checkin` print its summary line |
 | `dashboard --check` \| `--apply` | render `dashboard.md` + `dashboard.html`; `--check` exits **1 on drift**, **2 on bad args**, anything else = the renderer could not run |
 | `issue [--project KEY] [--apply]` | the concise ledger block for each project's GitHub issue; `--apply` writes it into the issue body between the markers (needs `gh`) |
 
diff --git a/REFERENCE.md b/REFERENCE.md
index 517aa7d..dad0813 100644
--- a/REFERENCE.md
+++ b/REFERENCE.md
@@ -189,6 +189,22 @@ five entries, and the `cortex.py` lines the human is likely to type next. It
 flips no state and writes no entry of its own — the jobs output is read by
 the human or the agent in the session and recorded with `running` / `done`.
 
+### Drift
+
+`pyauto-brain cortex drift` checks the body map against the laptop Science
+tree, `<root>/<category>/<project>` with categories `active`, `development`,
+`complete`, `archive` (the root is derived from the rows' `local_path`s;
+`--science-root` overrides). Errors: a folder in `active/` or `development/`
+with no row; a non-retired row whose `local_path` is gone; a folder whose
+category disagrees with its status (`active`/`development` hold
+`active|dormant|planned`, `complete`/`archive` hold `retired|dormant`); a
+derived root that does not exist while other rows' folders do. Warnings: an
+unregistered folder in `complete/` or `archive/` (storage), a non-retired
+row whose `ral_root` category differs from its `local_path` category. Rows
+outside the Science tree (repo-backed roots under the workspace) are exempt
+from the category rules. It writes nothing; `census` and `checkin` print one
+summary line, off the laptop a skip.
+
 ### `checkin.yaml`
 
 ```yaml
diff --git a/docs/schema_decisions.md b/docs/schema_decisions.md
index ff7e008..286efa0 100644
--- a/docs/schema_decisions.md
+++ b/docs/schema_decisions.md
@@ -475,3 +475,18 @@ Choices made in phase 2 — the conductor, the board and the workflows
     is registered `active` by human decision, the one exception to 52(a): an
     active project needs a ledger, and git is not what makes it science.
     Why: one layout on both machines means a path is derived, never looked up.
+
+62. **`development/` is a Science category, and drift is checked, not
+    hoped for** (2026-10-29, PyAutoBrain#543). The laptop Science tree gained
+    `development/` beside `active/` for projects that develop or validate the
+    software (`analytic_gaussian`, `ep_toy_gaussian`, `ic50_workspace`,
+    `slope_hierarchy_scale`); like `active/` it holds `active`, `dormant` or
+    `planned` rows. The conductor's `drift` verb compares `projects.yaml`
+    with the tree — unregistered folders, vanished `local_path`s, category
+    against status, `ral_root` category — and `census`/`checkin` print its
+    summary line on the laptop. It writes nothing and stays out of
+    `census()`, so the board rendered in CI does not depend on the machine.
+    Why: when Science moved from `C:\Users\Jammy\Science` to
+    `Workspace\Science`, every `local_path` went stale and `pull` quietly
+    reached 3 of 12 active projects for weeks; nothing in the organism
+    compared the map with the territory.