diff --git a/.planning/STATE.md b/.planning/STATE.md
index 83f851a..880ee3a 100644
--- a/.planning/STATE.md
+++ b/.planning/STATE.md
@@ -1,3 +1,16 @@
+---
+gsd_state_version: 1.0
+milestone: v1.0
+milestone_name: milestone
+status: Phase 1 complete
+last_updated: "2026-04-01T21:05:00Z"
+progress:
+  total_phases: 7
+  completed_phases: 1
+  total_plans: 3
+  completed_plans: 3
+---
+
 # Project State
 
 ## Project Reference
@@ -5,18 +18,18 @@
 See: .planning/PROJECT.md (updated 2026-04-01)
 
 **Core value:** Flight controller must receive valid MAVLink GPS_INPUT at 5-10Hz with position accuracy ≤50m for 80% of frames — without this, the UAV cannot navigate in GPS-denied airspace.
-**Current focus:** Ready to begin Phase 1 (ESKF Core)
+**Current focus:** Phase 2 — Visual Odometry Pipeline
 
 ## Current Phase
 
-**Phase:** Not started
-**Next action:** Run `/gsd:plan-phase 1` to plan Phase 1 (ESKF Core)
+**Phase:** 1 — ESKF Core (✓ Complete)
+**Next action:** Run `/gsd:plan-phase 2` to plan Phase 2 (Visual Odometry Pipeline)
 
 ## Roadmap Summary
 
 | Phase | Name | Status |
 |-------|------|--------|
-| 1 | ESKF Core | Pending |
+| 1 | ESKF Core | ✓ Complete |
 | 2 | Visual Odometry Pipeline | Pending |
 | 3 | Satellite Matching + GPR | Pending |
 | 4 | MAVLink I/O | Pending |
@@ -39,3 +52,20 @@ See: .planning/PROJECT.md (updated 2026-04-01)
 - Brownfield: scaffold exists (~2800 lines), critical algorithms missing (ESKF, MAVLink, real TRT/cuVSLAM)
 - cuVSLAM + TRT available only on Jetson; dev/CI uses OpenCV ORB stub + MockInferenceEngine
 - Pipeline direction: top-down (API → ESKF → VO → satellite → GPS_INPUT)
+
+## Phase 1 Execution Summary (2026-04-01)
+
+**Status:** ✓ Complete — All 3 plans executed, 35 tests passing
+
+**Deliverables:**
+- `src/gps_denied/schemas/eskf.py` (68 lines) — ESKF data contracts (ConfidenceTier, ESKFState, ESKFConfig, IMUMeasurement)
+- `src/gps_denied/core/eskf.py` (359 lines) — 15-state ESKF with IMU prediction, VO/satellite updates, confidence tiers
+- `src/gps_denied/core/coordinates.py` (176 lines added) — Real K-matrix projection, ray-ground intersection, gps_to_pixel inverse
+- `tests/test_eskf.py` (290 lines) — 18 ESKF unit tests
+- `tests/test_coordinates.py` (+200 lines) — 17 coordinate chain tests
+
+**Requirements Covered:** ESKF-01 through ESKF-06 (all 6 Phase 1 requirements)
+
+**Commits:** 4 total (schemas, core ESKF, coordinates, tests, summaries)
+
+**Verification:** pytest 35/35 passing (100% success)