diff --git a/CHANGELOG.md b/CHANGELOG.md
index defc04f..5076959 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -4,6 +4,32 @@ All notable changes to seismo-relay are documented here.
 
 ---
 
+## v0.12.1 — 2026-04-16
+
+### Added
+
+- **`sfm/server.py` — `_LiveCache`** — in-memory live device cache that eliminates
+  redundant TCP round-trips between web requests.  Plain Python dict +
+  `threading.Lock`, no extra dependencies.
+
+  Cache strategy per endpoint:
+
+  | Endpoint | Strategy |
+  |---|---|
+  | `GET /device/info` | Indefinite; invalidated by `POST /device/config` |
+  | `GET /device/events` | Count-probe fast path — `poll()+count_events()` (~2 s); returns cached data if event count is unchanged; full download only when new events are detected |
+  | `GET /device/monitor/status` | 30-second TTL; invalidated immediately on monitor start/stop |
+  | `GET /device/event/{idx}/waveform` | Permanent per-index (waveforms are immutable once recorded) |
+
+- **`?force=true`** query param on all cached endpoints — bypasses cache and forces
+  a fresh read from the device.
+
+- **Cache invalidation hooks** — `POST /device/config` marks device info and events
+  stale; `POST /device/monitor/start` and `/stop` evict the monitor status entry
+  immediately so the next status poll reflects the actual device state.
+
+---
+
 ## v0.12.0 — 2026-04-13
 
 ### Added
diff --git a/CLAUDE.md b/CLAUDE.md
index c642602..d98ea38 100644
--- a/CLAUDE.md
+++ b/CLAUDE.md
@@ -2,7 +2,7 @@
 
 Ground-up Python replacement for **Blastware**, Instantel's Windows-only software for
 managing MiniMate Plus seismographs. Connects over direct RS-232 or cellular modem
-(Sierra Wireless RV50 / RV55). Current version: **v0.12.0**.
+(Sierra Wireless RV50 / RV55). Current version: **v0.12.1**.
 
 ---