diff --git a/docs/ARCHITECTURE.md b/docs/ARCHITECTURE.md
index 0e168bd..a59c6c5 100644
--- a/docs/ARCHITECTURE.md
+++ b/docs/ARCHITECTURE.md
@@ -78,9 +78,15 @@ yukart/nav/guidance       next manoeuvre, distance, street name, retained
 yukart/nav/route          active route geometry, retained
 ```
 
-Payloads: JSON for low-rate signals (readable, debuggable); compact binary or
-CBOR for `can/raw`, since a 500 kbps bus produces far more traffic than JSON
-should carry.
+Payloads: a self-describing JSON envelope for decoded signals; compact binary for
+`can/raw`, since a 500 kbps bus produces far more traffic than JSON should carry.
+
+Every envelope carries **two clocks**. `monotonic` is authoritative for ordering
+and intervals; `timestamp` is the absolute reference and may step, since the car
+boots without network and NTP corrects the clock once LTE connects mid-drive.
+
+Topic names, payload schemas and the signal registry live in
+[contracts](gitea:yukart/contracts).
 
 Topic names and payload schemas are a **contract shared across repos** — Android
 and ESP32 clients depend on them — so they are versioned in their own repo
@@ -308,6 +314,8 @@ rewriting the document.
 | 3 | Listen-only sniffing + active OBD-II, single writer | Accepted | 2026-08-14 |
 | 4 | MQTT as the bus | **Proposed** | 2026-08-14 |
 | 5 | Rust for on-Orin services, Python for off-car tooling, Dart for the display client | Accepted | 2026-09-04 |
+| 21 | Two clocks per envelope; `monotonic` orders, `timestamp` references | Accepted | 2026-09-05 |
+| 22 | `signals.json` is the single source for signal name and unit; both are derived, never authored twice | Accepted | 2026-09-05 |
 | 6 | Local logging first; off-board LTE telemetry deferred | Accepted | 2026-08-14 |
 | 7 | Camera/AI inference is a later, separate task | Accepted | 2026-08-14 |
 | 8 | Self-hosted offline navigation (MapLibre GL + Valhalla + PMTiles) over a cloud maps SDK | Accepted | 2026-09-03 |
diff --git a/docs/REPOS.md b/docs/REPOS.md
index b4092b7..133622c 100644
--- a/docs/REPOS.md
+++ b/docs/REPOS.md
@@ -23,6 +23,7 @@ contracts repo, not copied into each consumer.
 | [project-yukart](gitea:yukart/project-yukart) | Hub: overview, roadmap, architecture |
 | [orin-nano-env-setup](gitea:yukart/orin-nano-env-setup) | Jetson host bring-up |
 | [app-flutter](gitea:yukart/app-flutter) | Flutter display client |
+| [contracts](gitea:yukart/contracts) | Topic namespace, payload schemas, signal registry |
 | [svc-gw](gitea:yukart/svc-gw) | Telemetry gateway — aggregation and the HTTP surface |
 | [svc-nav](gitea:yukart/svc-nav) | Navigation service — routing and guidance |
 | [tool-mapmint](gitea:yukart/tool-mapmint) | Map artifact minting, workstation-side |
@@ -32,7 +33,6 @@ contracts repo, not copied into each consumer.
 
 | Repository | Role | Why separate |
 |---|---|---|
-| `contracts` | Topic namespace, payload schemas, Z27AG DBC | Consumed by every other repo, including non-Jetson clients; must not be duplicated |
 | `svc-core` | Acquisition + processing cluster: `can-bridge`, `obd-poller`, `gnss`, `decoder`, `recorder` | Developed and deployed as one unit on the Orin |
 | `app-esp32` | ESP32 RLCD/e-ink display firmware (Class B) | Embedded toolchain, flashed not deployed |
 | `tool-analysis` | Offline session analysis, reverse-engineering notebooks | Runs off-car, no runtime coupling |