diff --git a/AGENTS.md b/AGENTS.md
index ff5f0493..4bcba0f8 100644
--- a/AGENTS.md
+++ b/AGENTS.md
@@ -1,8 +1,11 @@
 # AGENTS.md — OpenStrap `edge`
 
-Reviewer context, verified against code at `kAlgoVersion 47`, schema `v25`,
-`0.9.19+50`. Where a source comment disagrees with an implementation, **the
-implementation wins** — header comments here go stale (e.g.
+Reviewer context. This doc drifts from code between edits — check
+`kAlgoVersion` (`lib/compute/derivation_engine.dart`), `schemaVersion`
+(`lib/data/db.dart`), and the `version:` line in `pubspec.yaml` directly
+rather than trusting a number written here. Where a source comment disagrees
+with an implementation, **the implementation wins** — header comments here go
+stale (e.g.
 `lib/compute/substrate.dart:10-12` still describes a wake-to-wake day model that
 `calendarDays()` at `:429` no longer implements; it walks local midnight to
 local midnight).
@@ -48,8 +51,10 @@ unless it is pure orchestration.
 - `notify/` — `notification_center.dart` is the **single emitter**;
   `fired_keys.dart` is the persistent fire-once guard.
 - `coach/` — read-only SQL over allow-listed `v_*` views behind a deny-list guard.
-- `ui/` — ~120 files: `ui/design` (design system), `ui/kit/charts.dart`,
-  `ui/screens/` (shared metric/trend IA).
+- `ui2/` — 66 files (`lib/ui` was deleted in the UI rebuild): `ui2/theme.dart`
+  and `ui2/grammar.dart` (design system), `ui2/charts.dart`, `ui2/screens/`
+  (shared metric/trend IA), plus `ui2/onboarding/`, `ui2/activity/`,
+  `ui2/profile/`.
 - Also `ai/` (BYOK), `gps/`, `health/` (HealthKit/Health Connect export),
   `telemetry/` (opt-in), `widget/` (App-Group snapshot for WidgetKit/watch).
 
diff --git a/README.md b/README.md
index 93d2c88c..f6442b68 100644
--- a/README.md
+++ b/README.md
@@ -221,13 +221,22 @@ lib/ble/       Bluetooth + sync
 lib/data/      local storage + the repository seam the UI reads from
 lib/compute/   runs the analytics pipeline, writes results
 lib/state/     AppState, the one source of truth
-lib/ui/        every screen
+lib/ui2/       every screen
 ```
 
 Protocol decoding and analytics live in their own repos —
 [protocol](https://github.com/OpenStrap/protocol),
 [analytics](https://github.com/OpenStrap/analytics).
 
+## Guides
+
+- [`guides/IOS_INSTALLATION.md`](guides/IOS_INSTALLATION.md) — building and installing on an iPhone.
+- [`guides/IOS_SIDELOAD.md`](guides/IOS_SIDELOAD.md) — sideloading without a paid developer account.
+- [`guides/WATCH_SETUP.md`](guides/WATCH_SETUP.md) — the Apple Watch companion app.
+- [`guides/AI_COACH.md`](guides/AI_COACH.md) — bring-your-own-key AI coach, briefings, and journal.
+- [`guides/TASKER_INTEGRATION.md`](guides/TASKER_INTEGRATION.md) — buzzing the strap from Tasker/automation.
+- [`guides/BUZZ_MEANINGS.md`](guides/BUZZ_MEANINGS.md) — what each buzz pattern means.
+
 ## Contributing
 
 Found something broken? Open an issue. Found something broken and fixed it? Even better,
diff --git a/lib/gps/route_math.dart b/lib/gps/route_math.dart
index 8de0af88..eb7a4825 100644
--- a/lib/gps/route_math.dart
+++ b/lib/gps/route_math.dart
@@ -2,14 +2,17 @@
 //
 // Everything here is a pure function of its inputs (no DB, no I/O, no clock),
 // so it is directly unit-testable and shared by the repository (splits) and the
-// UI (zone-coloured polylines). Distances use the haversine great-circle
-// formula on WGS84 mean radius; good to well under a metre at running scale.
+// UI (zone-coloured polylines). Distance is latlong2's haversine great-circle
+// calculator (WGS84 equatorial radius, not our old mean-radius constant — a
+// ~0.1% difference, well under GPS fix noise); good to well under a metre at
+// running scale.
 
 import 'dart:math' as math;
 
+import 'package:latlong2/latlong.dart';
+
 import 'route_models.dart';
 
-const double kEarthRadiusM = 6371008.8; // WGS84 mean radius
 const double kMetersPerKm = 1000.0;
 const double kMetersPerMile = 1609.344;
 
@@ -65,18 +68,9 @@ double? fallbackSpeedMps(RoutePoint? prev, RoutePoint cur) {
 }
 
 /// Great-circle distance in metres between two lat/lng points.
-double haversineMeters(double lat1, double lng1, double lat2, double lng2) {
-  const deg2rad = math.pi / 180.0;
-  final dLat = (lat2 - lat1) * deg2rad;
-  final dLng = (lng2 - lng1) * deg2rad;
-  final a = math.sin(dLat / 2) * math.sin(dLat / 2) +
-      math.cos(lat1 * deg2rad) *
-          math.cos(lat2 * deg2rad) *
-          math.sin(dLng / 2) *
-          math.sin(dLng / 2);
-  final c = 2 * math.atan2(math.sqrt(a), math.sqrt(1 - a));
-  return kEarthRadiusM * c;
-}
+const _distance = DistanceHaversine(roundResult: false);
+double haversineMeters(double lat1, double lng1, double lat2, double lng2) =>
+    _distance.distance(LatLng(lat1, lng1), LatLng(lat2, lng2));
 
 /// Total path length in metres over an ordered list of route points.
 /// Implausible segments (a teleport across a recording gap — see