diff --git a/bb.edn b/bb.edn
index e9bf3f7..e48548a 100644
--- a/bb.edn
+++ b/bb.edn
@@ -14,7 +14,7 @@
 
   test {:doc "Run all server tests"
         :task (let [expr (str "(require 'pocketbook.db-test 'pocketbook.transit-test"
-                              " 'pocketbook.server-test)"
+                              " 'pocketbook.server-test 'pocketbook.core-test)"
                               " (let [r (clojure.test/run-all-tests #\"pocketbook\\..*\")]"
                               " (System/exit (if (and (zero? (:fail r)) (zero? (:error r))) 0 1)))")]
                 (shell "clj" "-M:dev" "-e" expr))}
diff --git a/deps.edn b/deps.edn
index 48726ec..78ac008 100644
--- a/deps.edn
+++ b/deps.edn
@@ -1,5 +1,6 @@
 {:paths ["src"]
  :deps  {org.clojure/clojure          {:mvn/version "1.12.0"}
+         org.clojure/core.async        {:mvn/version "1.7.701"}
          http-kit/http-kit             {:mvn/version "2.8.0"}
          com.cognitect/transit-clj     {:mvn/version "1.0.333"}
          com.taoensso/nippy            {:mvn/version "3.4.2"}
diff --git a/example/todomvc/pocketbook/todomvc.cljs b/example/todomvc/pocketbook/todomvc.cljs
index aa240e2..e8b65e8 100644
--- a/example/todomvc/pocketbook/todomvc.cljs
+++ b/example/todomvc/pocketbook/todomvc.cljs
@@ -1,6 +1,7 @@
 (ns pocketbook.todomvc
   "TodoMVC built on Pocketbook — offline-first, synced, Clojure-native."
   (:require [pocketbook.core :as pb]
+            [pocketbook.store.idb :as idb]
             [cljs.core.async :refer [go <!]]
             [clojure.string :as str]))
 
@@ -241,11 +242,11 @@
 
 (defn ^:export init []
   (go
-    (let [conn  (<! (pb/open "pocketbook-todomvc"))
-          todos (pb/synced-atom conn "todo"
+    (let [store (<! (idb/open "pocketbook-todomvc"))
+          todos (pb/synced-atom store "todo"
                   {:server "http://localhost:8090/sync"
                    :interval 15000})]
-      (reset! !conn conn)
+      (reset! !conn store)
       (reset! !todos todos)
       ;; Render + bind immediately (empty or stale is fine)
       (render!)
diff --git a/src/pocketbook/core.cljs b/src/pocketbook/core.cljc
similarity index 63%
rename from src/pocketbook/core.cljs
rename to src/pocketbook/core.cljc
index 769fafd..31cfc9e 100644
--- a/src/pocketbook/core.cljs
+++ b/src/pocketbook/core.cljc
@@ -2,48 +2,63 @@
   "Pocketbook: a Clojure-native synced atom.
 
    Usage:
-     (def conn (pocketbook/open \"my-app\"))
-     (def todos (pocketbook/synced-atom conn \"todo\"
+     (def store (<! (idb/open \"my-app\")))   ;; or (memory/create)
+     (def todos (pb/synced-atom store \"todo\"
                   {:server \"http://localhost:8090/sync\"}))
      (go (<! (ready? todos))
          (swap! todos assoc \"todo:1\" {:text \"Buy milk\"}))
      @todos  ;=> {\"todo:1\" {:text \"Buy milk\"}}
   "
-  (:require [pocketbook.idb :as idb]
+  (:require [pocketbook.store :as store]
             [pocketbook.sync :as sync]
             [clojure.string :as str]
-            [cljs.core.async :as async :refer [go go-loop <! >! chan put! timeout alts!]]))
+            #?(:clj  [clojure.core.async :as async :refer [go go-loop <! >! chan put! timeout alts!]]
+               :cljs [cljs.core.async :as async :refer [go go-loop <! >! chan put! timeout alts!]])))
 
 ;; ---------------------------------------------------------------------------
-;; Connection (IDB handle)
+;; Internal helpers
 ;; ---------------------------------------------------------------------------
 
-(defn open
-  "Open a Pocketbook connection (IndexedDB database).
-   Returns a channel yielding the connection map."
-  [db-name]
-  (let [ch (chan 1)]
-    (go
-      (let [db (<! (idb/open db-name))]
-        (>! ch {:db db :db-name db-name})
-        (async/close! ch)))
-    ch))
+(defn- now-ms []
+  #?(:clj  (System/currentTimeMillis)
+     :cljs (.now js/Date)))
 
-(defn shutdown!
-  "Close a Pocketbook connection."
-  [{:keys [db atoms]}]
-  ;; Stop all sync loops
-  (doseq [[_ sa] @(or atoms (atom {}))]
-    (when-let [stop (:stop-fn sa)]
-      (stop)))
-  (idb/close-db! db))
+(defn- prefix-str [group]
+  (str group ":"))
 
 ;; ---------------------------------------------------------------------------
-;; Synced Atom — implements IAtom semantics
+;; Shared reset logic
+;; ---------------------------------------------------------------------------
+
+(defn- do-reset!*
+  "Shared reset implementation. Updates cache, tracks pending, writes to store, kicks sync."
+  [store cache versions pending kick-ch new-val]
+  (let [old @cache]
+    (reset! cache new-val)
+    (let [all-keys (into (set (keys old)) (keys new-val))
+          changed? (volatile! false)]
+      (doseq [k all-keys]
+        (when (not= (get old k) (get new-val k))
+          (vreset! changed? true)
+          (swap! pending conj k)
+          (let [v (get new-val k)]
+            (if (nil? v)
+              (store/put-doc! store
+                {:id k :value nil :version (get @versions k 0)
+                 :updated (now-ms) :deleted true :synced false})
+              (store/put-doc! store
+                {:id k :value v :version (get @versions k 0)
+                 :updated (now-ms) :deleted false :synced false})))))
+      (when @changed?
+        (put! kick-ch :kick)))
+    new-val))
+
+;; ---------------------------------------------------------------------------
+;; Synced Atom
 ;; ---------------------------------------------------------------------------
 
 (deftype SyncedAtom [group         ;; string prefix, e.g. "todo"
-                     conn          ;; {:db idb, ...}
+                     store         ;; PStore implementation
                      cache         ;; atom containing {id -> value}
                      versions      ;; atom containing {id -> version}
                      pending       ;; atom containing #{id} — unsynced ids
@@ -56,93 +71,83 @@
                      sync-interval ;; ms
                      _meta]        ;; metadata atom
 
-  IAtom
+  #?@(:clj
+      [clojure.lang.IDeref
+       (deref [_] @cache)
 
-  IDeref
-  (-deref [_]
-    @cache)
+       clojure.lang.IRef
+       (addWatch [this key f] (add-watch cache key f) this)
+       (removeWatch [this key] (remove-watch cache key) this)
+       (getWatches [_] (.getWatches ^clojure.lang.IRef cache))
+       (getValidator [_] nil)
+       (setValidator [_ _vf] nil)
 
-  IReset
-  (-reset! [_ new-val]
-    ;; Replace the entire cache (all docs in group)
-    (let [old @cache]
-      (reset! cache new-val)
-      ;; Track which docs changed/added/removed
-      (let [all-keys (into (set (keys old)) (keys new-val))
-            changed? (volatile! false)]
-        (doseq [k all-keys]
-          (when (not= (get old k) (get new-val k))
-            (vreset! changed? true)
-            (swap! pending conj k)
-            ;; Write to IDB
-            (let [v (get new-val k)]
-              (if (nil? v)
-                ;; Doc was dissoc'd — mark deleted
-                (idb/put-doc! (:db conn)
-                  {:id k :value nil :version (get @versions k 0)
-                   :updated (.now js/Date) :deleted true :synced false})
-                (idb/put-doc! (:db conn)
-                  {:id k :value v :version (get @versions k 0)
-                   :updated (.now js/Date) :deleted false :synced false})))))
-        ;; Kick the sync loop to push immediately
-        (when @changed?
-          (put! kick-ch :kick)))
-      new-val))
+       clojure.lang.IAtom
+       (reset [_ newval]
+         (do-reset!* store cache versions pending kick-ch newval))
+       (swap [this f]
+         (.reset this (f @cache)))
+       (swap [this f arg]
+         (.reset this (f @cache arg)))
+       (swap [this f arg1 arg2]
+         (.reset this (f @cache arg1 arg2)))
+       (swap [this f x y args]
+         (.reset this (apply f @cache x y args)))
+       (compareAndSet [this old new]
+         (if (= @cache old)
+           (do (.reset this new) true)
+           false))]
 
-  ISwap
-  (-swap! [o f]
-    (-reset! o (f @cache)))
-  (-swap! [o f a]
-    (-reset! o (f @cache a)))
-  (-swap! [o f a b]
-    (-reset! o (f @cache a b)))
-  (-swap! [o f a b xs]
-    (-reset! o (apply f @cache a b xs)))
+      :cljs
+      [IAtom
 
-  IWatchable
-  (-add-watch [_ key f]
-    (add-watch cache key f))
-  (-remove-watch [_ key]
-    (remove-watch cache key))
-  (-notify-watches [_ old new]
-    ;; Delegated to the inner atom
-    nil)
+       IDeref
+       (-deref [_] @cache)
 
-  IMeta
-  (-meta [_] @_meta)
+       IReset
+       (-reset! [_ new-val]
+         (do-reset!* store cache versions pending kick-ch new-val))
 
-  IWithMeta
-  (-with-meta [_ m] (reset! _meta m))
+       ISwap
+       (-swap! [o f]
+         (-reset! o (f @cache)))
+       (-swap! [o f a]
+         (-reset! o (f @cache a)))
+       (-swap! [o f a b]
+         (-reset! o (f @cache a b)))
+       (-swap! [o f a b xs]
+         (-reset! o (apply f @cache a b xs)))
 
-  IPrintWithWriter
-  (-pr-writer [_ writer opts]
-    (-write writer (str "#<SyncedAtom[" group "] " (count @cache) " docs>"))))
+       IWatchable
+       (-add-watch [_ key f]
+         (add-watch cache key f))
+       (-remove-watch [_ key]
+         (remove-watch cache key))
+       (-notify-watches [_ _old _new]
+         nil)
+
+       IMeta
+       (-meta [_] @_meta)
+
+       IWithMeta
+       (-with-meta [_ m] (reset! _meta m))
+
+       IPrintWithWriter
+       (-pr-writer [_ writer _opts]
+         (-write writer (str "#<SyncedAtom[" group "] " (count @cache) " docs>")))]))
 
 ;; ---------------------------------------------------------------------------
-;; Internal helpers
+;; Store ↔ Atom sync
 ;; ---------------------------------------------------------------------------
 
-(defn- prefix-str [group]
-  (str group ":"))
-
-(defn- now-ms []
-  (.now js/Date))
-
-(defn- doc-in-group? [group id]
-  (str/starts-with? id (prefix-str group)))
-
-;; ---------------------------------------------------------------------------
-;; IDB ↔ Atom sync
-;; ---------------------------------------------------------------------------
-
-(defn- load-from-idb!
-  "Load all docs for the group from IndexedDB into the atom.
+(defn- load-from-store!
+  "Load all docs for the group from the store into the atom.
    Returns a channel that closes when done."
   [sa]
   (let [ch (chan 1)]
     (go
       (let [prefix (prefix-str (.-group sa))
-            docs   (<! (idb/get-all-by-prefix (:db (.-conn sa)) prefix))
+            docs   (<! (store/docs-by-prefix (.-store sa) prefix))
             state  (into {}
                      (comp
                        (remove :deleted)
@@ -153,32 +158,20 @@
                      docs)]
         (reset! (.-cache sa) state)
         (reset! (.-versions sa) vers)
-        ;; Load last-sync from IDB meta
-        (let [ls (<! (idb/get-meta (:db (.-conn sa))
+        (let [ls (<! (store/get-meta (.-store sa)
                        (str "last-sync:" (.-group sa))))]
           (reset! (.-last_sync sa) (or ls 0)))
         (put! ch true)
         (async/close! ch)))
     ch))
 
-(defn- write-doc-to-idb!
-  "Persist a single doc to IDB. Returns a channel."
-  [sa id value deleted?]
-  (idb/put-doc! (:db (.-conn sa))
-    {:id      id
-     :value   value
-     :version (get @(.-versions sa) id 0)
-     :updated (now-ms)
-     :deleted (boolean deleted?)
-     :synced  false}))
-
 (defn- mark-synced!
-  "Mark a doc as synced in IDB and update its version."
+  "Mark a doc as synced in the store and update its version."
   [sa id version]
   (swap! (.-versions sa) assoc id version)
   (swap! (.-pending sa) disj id)
   (let [value (get @(.-cache sa) id)]
-    (idb/put-doc! (:db (.-conn sa))
+    (store/put-doc! (.-store sa)
       {:id      id
        :value   value
        :version version
@@ -191,7 +184,7 @@
 ;; ---------------------------------------------------------------------------
 
 (defn- do-pull!
-  "Pull changes from server, merge into atom + IDB."
+  "Pull changes from server, merge into atom + store."
   [sa]
   (go
     (when-let [opts (.-server_opts sa)]
@@ -201,27 +194,24 @@
           (let [docs   (:docs result)
                 max-ts (reduce max @(.-last_sync sa)
                          (map :updated docs))]
-            ;; Merge each doc into cache
             (doseq [doc docs]
               (let [id (:id doc)]
-                ;; Only apply if server version > local version
                 (when (> (:version doc) (get @(.-versions sa) id 0))
                   (if (:deleted doc)
                     (do
                       (swap! (.-cache sa) dissoc id)
                       (swap! (.-versions sa) assoc id (:version doc))
-                      (idb/put-doc! (:db (.-conn sa))
+                      (store/put-doc! (.-store sa)
                         {:id id :value nil :version (:version doc)
                          :updated (:updated doc) :deleted true :synced true}))
                     (do
                       (swap! (.-cache sa) assoc id (:value doc))
                       (swap! (.-versions sa) assoc id (:version doc))
-                      (idb/put-doc! (:db (.-conn sa))
+                      (store/put-doc! (.-store sa)
                         {:id id :value (:value doc) :version (:version doc)
                          :updated (:updated doc) :deleted false :synced true}))))))
-            ;; Update last-sync
             (reset! (.-last_sync sa) max-ts)
-            (idb/set-meta! (:db (.-conn sa))
+            (store/set-meta! (.-store sa)
               (str "last-sync:" (.-group sa)) max-ts))
           true)))))
 
@@ -248,13 +238,12 @@
                   (<! (mark-synced! sa (:id r) (:version r)))
 
                   :conflict
-                  ;; On conflict, accept server value and mark synced
                   (do
                     (when (:value r)
                       (swap! (.-cache sa) assoc (:id r) (:value r)))
                     (swap! (.-versions sa) assoc (:id r) (:current-version r))
                     (swap! (.-pending sa) disj (:id r))
-                    (idb/put-doc! (:db (.-conn sa))
+                    (store/put-doc! (.-store sa)
                       {:id      (:id r)
                        :value   (or (:value r) (get @(.-cache sa) (:id r)))
                        :version (:current-version r)
@@ -262,8 +251,9 @@
                        :deleted false
                        :synced  true}))
 
-                  ;; Unknown status, log
-                  (js/console.warn "Unknown push result:" (pr-str r))))
+                  ;; Unknown status
+                  #?(:clj  (println "Unknown push result:" (pr-str r))
+                     :cljs (js/console.warn "Unknown push result:" (pr-str r)))))
               true)))))))
 
 (defn- do-sync!
@@ -279,7 +269,7 @@
 ;; ---------------------------------------------------------------------------
 
 (defn- start-sync-loop!
-  "Start the background sync loop. Returns a stop function."
+  "Start the background sync loop."
   [sa]
   (let [stop-ch  (.-stop_ch sa)
         kick-ch  (.-kick_ch sa)
@@ -290,25 +280,22 @@
       (let [[_ ch] (alts! [stop-ch kick-ch (timeout interval)])]
         (when-not (= ch stop-ch)
           (if (= ch kick-ch)
-            (<! (do-push! sa))   ;; kick = local write, just push
-            (<! (do-sync! sa)))  ;; timeout = full pull+push
+            (<! (do-push! sa))
+            (<! (do-sync! sa)))
           (recur))))
     ;; Online/offline handler
     (swap! cleanups conj
       (sync/on-connectivity-change
         (fn [] (go (<! (do-sync! sa))))
         (fn [] nil)))
-    ;; SSE — live pull on server push
-    (when-let [opts (.-server_opts sa)]
-      (swap! cleanups conj
-        (sync/listen-events opts (.-group sa)
-          (fn [_group]
-            (go (<! (do-pull! sa)))))))
-    (reset! (.-cleanup_fn sa) cleanups)
-    ;; Return stop function
-    (fn []
-      (put! stop-ch :stop)
-      (doseq [f @(.-cleanup_fn sa)] (f)))))
+    ;; SSE — live pull on server push (CLJS only)
+    #?(:cljs
+       (when-let [opts (.-server_opts sa)]
+         (swap! cleanups conj
+           (sync/listen-events opts (.-group sa)
+             (fn [_group]
+               (go (<! (do-pull! sa))))))))
+    (reset! (.-cleanup_fn sa) @cleanups)))
 
 ;; ---------------------------------------------------------------------------
 ;; Public API
@@ -321,7 +308,7 @@
      :server   — server URL (e.g. \"http://localhost:8090/sync\")
      :cache    — custom atom to use (e.g. reagent/atom). Default: cljs.core/atom
      :interval — sync interval in ms (default 30000)"
-  [conn group & [{:keys [server cache interval]
+  [store group & [{:keys [server cache interval]
                    :or   {interval 30000}}]]
   (let [cache-atom  (or cache (atom {}))
         versions    (atom {})
@@ -333,22 +320,20 @@
         kick-ch     (chan (async/sliding-buffer 1))
         cleanup-fn  (atom nil)
         meta-atom   (atom nil)
-        sa          (SyncedAtom. group conn cache-atom versions pending
+        sa          (SyncedAtom. group store cache-atom versions pending
                       server-opts last-sync ready-ch stop-ch kick-ch
                       cleanup-fn interval meta-atom)]
-    ;; Load from IDB, then start sync
     (go
-      (<! (load-from-idb! sa))
+      (<! (load-from-store! sa))
       (put! ready-ch true)
       (async/close! ready-ch)
-      ;; Initial sync
       (when server-opts
         (<! (do-sync! sa))
         (start-sync-loop! sa)))
     sa))
 
 (defn ready?
-  "Returns a channel that yields true when the atom has finished loading from IDB."
+  "Returns a channel that yields true when the atom has finished loading from the store."
   [sa]
   (.-ready_ch sa))
 
@@ -363,7 +348,7 @@
   (count @(.-pending sa)))
 
 (defn destroy!
-  "Stop the sync loop and clean up. Does not close the IDB connection."
+  "Stop the sync loop and clean up. Does not close the store."
   [sa]
   (put! (.-stop_ch sa) :stop)
   (doseq [f @(.-cleanup_fn sa)] (f)))
diff --git a/src/pocketbook/idb.cljs b/src/pocketbook/idb.cljs
deleted file mode 100644
index 80eacb8..0000000
--- a/src/pocketbook/idb.cljs
+++ /dev/null
@@ -1,225 +0,0 @@
-(ns pocketbook.idb
-  "IndexedDB wrapper with Transit serialization.
-   Stores documents as Transit-encoded strings preserving all Clojure types."
-  (:require [cognitect.transit :as t]
-            [cljs.core.async :as async :refer [chan put!]]))
-
-;; ---------------------------------------------------------------------------
-;; Transit
-;; ---------------------------------------------------------------------------
-
-(def ^:private writer (t/writer :json))
-(def ^:private reader (t/reader :json))
-
-(defn- encode [v]
-  (t/write writer v))
-
-(defn- decode [s]
-  (when s (t/read reader s)))
-
-;; ---------------------------------------------------------------------------
-;; IDB operations
-;; ---------------------------------------------------------------------------
-
-(defn open
-  "Open an IndexedDB database. Returns a channel that yields the db."
-  [db-name]
-  (let [ch  (chan 1)
-        req (.open js/indexedDB db-name 1)]
-    (set! (.-onupgradeneeded req)
-      (fn [e]
-        (let [db (.-result (.-target e))]
-          ;; Main document store
-          (when-not (.contains (.-objectStoreNames db) "docs")
-            (let [store (.createObjectStore db "docs" #js {:keyPath "id"})]
-              (.createIndex store "synced" "synced" #js {:unique false})
-              (.createIndex store "updated" "updated" #js {:unique false})))
-          ;; Metadata store (last-sync timestamps, etc.)
-          (when-not (.contains (.-objectStoreNames db) "meta")
-            (.createObjectStore db "meta" #js {:keyPath "key"})))))
-    (set! (.-onsuccess req)
-      (fn [e]
-        (put! ch (.-result (.-target e)))
-        (async/close! ch)))
-    (set! (.-onerror req)
-      (fn [e]
-        (js/console.error "IDB open error:" e)
-        (async/close! ch)))
-    ch))
-
-(defn- tx
-  "Start an IDB transaction. mode is :readonly or :readwrite."
-  [db store-name mode]
-  (let [mode-str (case mode :readonly "readonly" :readwrite "readwrite")]
-    (.transaction db #js [store-name] mode-str)))
-
-(defn put-doc!
-  "Write a document to IDB. Returns a channel that closes on success.
-   doc should be: {:id str :value any :version int :updated int :deleted bool :synced bool}"
-  [db doc]
-  (let [ch    (chan 1)
-        txn   (tx db "docs" :readwrite)
-        store (.objectStore txn "docs")
-        ;; Serialize the value to Transit, keep metadata as-is
-        obj   #js {:id      (:id doc)
-                   :value   (encode (:value doc))
-                   :version (:version doc 0)
-                   :updated (:updated doc 0)
-                   :deleted (boolean (:deleted doc false))
-                   :synced  (boolean (:synced doc false))}
-        req   (.put store obj)]
-    (set! (.-onsuccess req) (fn [_] (put! ch true) (async/close! ch)))
-    (set! (.-onerror req) (fn [e] (js/console.error "IDB put error:" e) (async/close! ch)))
-    ch))
-
-(defn put-docs!
-  "Write multiple documents in a single transaction. Returns a channel."
-  [db docs]
-  (let [ch    (chan 1)
-        txn   (tx db "docs" :readwrite)
-        store (.objectStore txn "docs")]
-    (doseq [doc docs]
-      (let [obj #js {:id      (:id doc)
-                     :value   (encode (:value doc))
-                     :version (:version doc 0)
-                     :updated (:updated doc 0)
-                     :deleted (boolean (:deleted doc false))
-                     :synced  (boolean (:synced doc false))}]
-        (.put store obj)))
-    (set! (.-oncomplete txn) (fn [_] (put! ch true) (async/close! ch)))
-    (set! (.-onerror txn) (fn [e] (js/console.error "IDB batch put error:" e) (async/close! ch)))
-    ch))
-
-(defn get-doc
-  "Read a single document by id. Returns a channel yielding the doc or nil."
-  [db id]
-  (let [ch    (chan 1)
-        txn   (tx db "docs" :readonly)
-        store (.objectStore txn "docs")
-        req   (.get store id)]
-    (set! (.-onsuccess req)
-      (fn [e]
-        (let [result (.-result (.-target e))]
-          (if result
-            (do (put! ch {:id      (.-id result)
-                          :value   (decode (.-value result))
-                          :version (.-version result)
-                          :updated (.-updated result)
-                          :deleted (.-deleted result)
-                          :synced  (.-synced result)})
-                (async/close! ch))
-            (async/close! ch)))))
-    (set! (.-onerror req)
-      (fn [e] (js/console.error "IDB get error:" e) (async/close! ch)))
-    ch))
-
-(defn get-all-by-prefix
-  "Get all documents whose id starts with prefix (e.g., 'todo:').
-   Returns a channel yielding a vector of docs."
-  [db prefix]
-  (let [ch    (chan 1)
-        txn   (tx db "docs" :readonly)
-        store (.objectStore txn "docs")
-        range (.bound js/IDBKeyRange prefix (str prefix "\uffff"))
-        req   (.openCursor store range)
-        docs  (atom [])]
-    (set! (.-onsuccess req)
-      (fn [e]
-        (let [cursor (.-result (.-target e))]
-          (if cursor
-            (let [val (.-value cursor)]
-              (swap! docs conj
-                {:id      (.-id val)
-                 :value   (decode (.-value val))
-                 :version (.-version val)
-                 :updated (.-updated val)
-                 :deleted (.-deleted val)
-                 :synced  (.-synced val)})
-              (.continue cursor))
-            (do
-              (put! ch @docs)
-              (async/close! ch))))))
-    (set! (.-onerror req)
-      (fn [e] (js/console.error "IDB cursor error:" e) (async/close! ch)))
-    ch))
-
-(defn get-unsynced
-  "Get all documents with synced=false. Returns a channel yielding a vector."
-  [db]
-  (let [ch    (chan 1)
-        txn   (tx db "docs" :readonly)
-        store (.objectStore txn "docs")
-        idx   (.index store "synced")
-        req   (.openCursor idx (.only js/IDBKeyRange false))
-        docs  (atom [])]
-    (set! (.-onsuccess req)
-      (fn [e]
-        (let [cursor (.-result (.-target e))]
-          (if cursor
-            (let [val (.-value cursor)]
-              (swap! docs conj
-                {:id      (.-id val)
-                 :value   (decode (.-value val))
-                 :version (.-version val)
-                 :updated (.-updated val)
-                 :deleted (.-deleted val)
-                 :synced  false})
-              (.continue cursor))
-            (do
-              (put! ch @docs)
-              (async/close! ch))))))
-    (set! (.-onerror req)
-      (fn [e] (js/console.error "IDB unsynced error:" e) (async/close! ch)))
-    ch))
-
-(defn delete-doc!
-  "Delete a document from IDB by id. Returns a channel."
-  [db id]
-  (let [ch    (chan 1)
-        txn   (tx db "docs" :readwrite)
-        store (.objectStore txn "docs")
-        req   (.delete store id)]
-    (set! (.-onsuccess req) (fn [_] (put! ch true) (async/close! ch)))
-    (set! (.-onerror req) (fn [e] (js/console.error "IDB delete error:" e) (async/close! ch)))
-    ch))
-
-;; ---------------------------------------------------------------------------
-;; Metadata
-;; ---------------------------------------------------------------------------
-
-(defn get-meta
-  "Get a metadata value by key. Returns a channel."
-  [db key]
-  (let [ch    (chan 1)
-        txn   (tx db "meta" :readonly)
-        store (.objectStore txn "meta")
-        req   (.get store key)]
-    (set! (.-onsuccess req)
-      (fn [e]
-        (let [result (.-result (.-target e))]
-          (if result
-            (do (put! ch (.-value result))
-                (async/close! ch))
-            (async/close! ch)))))
-    (set! (.-onerror req) (fn [_] (async/close! ch)))
-    ch))
-
-(defn set-meta!
-  "Set a metadata value. Returns a channel."
-  [db key value]
-  (let [ch    (chan 1)
-        txn   (tx db "meta" :readwrite)
-        store (.objectStore txn "meta")
-        req   (.put store #js {:key key :value value})]
-    (set! (.-onsuccess req) (fn [_] (put! ch true) (async/close! ch)))
-    (set! (.-onerror req) (fn [_] (async/close! ch)))
-    ch))
-
-;; ---------------------------------------------------------------------------
-;; Close
-;; ---------------------------------------------------------------------------
-
-(defn close-db!
-  "Close the IDB connection."
-  [db]
-  (when db (.close db)))
diff --git a/src/pocketbook/store.cljc b/src/pocketbook/store.cljc
new file mode 100644
index 0000000..883f17f
--- /dev/null
+++ b/src/pocketbook/store.cljc
@@ -0,0 +1,23 @@
+(ns pocketbook.store
+  "Storage protocol for Pocketbook.
+   All methods return core.async channels.")
+
+(defprotocol PStore
+  (put-doc! [store doc]
+    "Write a document to the store. doc is a map:
+       {:id str, :value any, :version int, :updated int, :deleted bool, :synced bool}
+     Returns a channel that closes on success.")
+
+  (docs-by-prefix [store prefix]
+    "Get all documents whose id starts with prefix.
+     Returns a channel yielding a vector of doc maps.")
+
+  (get-meta [store key]
+    "Get a metadata value by key.
+     Returns a channel yielding the value, or nil if not found.")
+
+  (set-meta! [store key value]
+    "Set a metadata value. Returns a channel that closes on success.")
+
+  (close-store! [store]
+    "Close the store and release resources."))
diff --git a/src/pocketbook/store/idb.cljs b/src/pocketbook/store/idb.cljs
new file mode 100644
index 0000000..6e390e4
--- /dev/null
+++ b/src/pocketbook/store/idb.cljs
@@ -0,0 +1,118 @@
+(ns pocketbook.store.idb
+  "IndexedDB store implementing the PStore protocol."
+  (:require [pocketbook.store :as store]
+            [pocketbook.transit :as transit]
+            [cljs.core.async :as async :refer [chan put!]]))
+
+;; ---------------------------------------------------------------------------
+;; IDB operations
+;; ---------------------------------------------------------------------------
+
+(defn- tx
+  "Start an IDB transaction. mode is :readonly or :readwrite."
+  [db store-name mode]
+  (let [mode-str (case mode :readonly "readonly" :readwrite "readwrite")]
+    (.transaction db #js [store-name] mode-str)))
+
+;; ---------------------------------------------------------------------------
+;; IDBStore
+;; ---------------------------------------------------------------------------
+
+(deftype IDBStore [db]
+  store/PStore
+  (put-doc! [_ doc]
+    (let [ch    (chan 1)
+          txn   (tx db "docs" :readwrite)
+          store (.objectStore txn "docs")
+          obj   #js {:id      (:id doc)
+                     :value   (transit/encode (:value doc))
+                     :version (:version doc 0)
+                     :updated (:updated doc 0)
+                     :deleted (boolean (:deleted doc false))
+                     :synced  (boolean (:synced doc false))}
+          req   (.put store obj)]
+      (set! (.-onsuccess req) (fn [_] (put! ch true) (async/close! ch)))
+      (set! (.-onerror req) (fn [e] (js/console.error "IDB put error:" e) (async/close! ch)))
+      ch))
+
+  (docs-by-prefix [_ prefix]
+    (let [ch    (chan 1)
+          txn   (tx db "docs" :readonly)
+          store (.objectStore txn "docs")
+          range (.bound js/IDBKeyRange prefix (str prefix "\uffff"))
+          req   (.openCursor store range)
+          docs  (atom [])]
+      (set! (.-onsuccess req)
+        (fn [e]
+          (let [cursor (.-result (.-target e))]
+            (if cursor
+              (let [val (.-value cursor)]
+                (swap! docs conj
+                  {:id      (.-id val)
+                   :value   (transit/decode (.-value val))
+                   :version (.-version val)
+                   :updated (.-updated val)
+                   :deleted (.-deleted val)
+                   :synced  (.-synced val)})
+                (.continue cursor))
+              (do
+                (put! ch @docs)
+                (async/close! ch))))))
+      (set! (.-onerror req)
+        (fn [e] (js/console.error "IDB cursor error:" e) (async/close! ch)))
+      ch))
+
+  (get-meta [_ key]
+    (let [ch    (chan 1)
+          txn   (tx db "meta" :readonly)
+          store (.objectStore txn "meta")
+          req   (.get store key)]
+      (set! (.-onsuccess req)
+        (fn [e]
+          (let [result (.-result (.-target e))]
+            (if result
+              (do (put! ch (.-value result))
+                  (async/close! ch))
+              (async/close! ch)))))
+      (set! (.-onerror req) (fn [_] (async/close! ch)))
+      ch))
+
+  (set-meta! [_ key value]
+    (let [ch    (chan 1)
+          txn   (tx db "meta" :readwrite)
+          store (.objectStore txn "meta")
+          req   (.put store #js {:key key :value value})]
+      (set! (.-onsuccess req) (fn [_] (put! ch true) (async/close! ch)))
+      (set! (.-onerror req) (fn [_] (async/close! ch)))
+      ch))
+
+  (close-store! [_]
+    (when db (.close db))))
+
+;; ---------------------------------------------------------------------------
+;; Open
+;; ---------------------------------------------------------------------------
+
+(defn open
+  "Open an IndexedDB store. Returns a channel yielding the IDBStore."
+  [db-name]
+  (let [ch  (chan 1)
+        req (.open js/indexedDB db-name 1)]
+    (set! (.-onupgradeneeded req)
+      (fn [e]
+        (let [db (.-result (.-target e))]
+          (when-not (.contains (.-objectStoreNames db) "docs")
+            (let [store (.createObjectStore db "docs" #js {:keyPath "id"})]
+              (.createIndex store "synced" "synced" #js {:unique false})
+              (.createIndex store "updated" "updated" #js {:unique false})))
+          (when-not (.contains (.-objectStoreNames db) "meta")
+            (.createObjectStore db "meta" #js {:keyPath "key"})))))
+    (set! (.-onsuccess req)
+      (fn [e]
+        (put! ch (IDBStore. (.-result (.-target e))))
+        (async/close! ch)))
+    (set! (.-onerror req)
+      (fn [e]
+        (js/console.error "IDB open error:" e)
+        (async/close! ch)))
+    ch))
diff --git a/src/pocketbook/store/memory.cljc b/src/pocketbook/store/memory.cljc
new file mode 100644
index 0000000..1adf828
--- /dev/null
+++ b/src/pocketbook/store/memory.cljc
@@ -0,0 +1,49 @@
+(ns pocketbook.store.memory
+  "In-memory store backed by atoms. Useful for testing and JVM clients."
+  (:require [pocketbook.store :as store]
+            #?(:clj  [clojure.core.async :as async :refer [chan put!]]
+               :cljs [cljs.core.async :as async :refer [chan put!]])
+            [clojure.string :as str]))
+
+(deftype MemoryStore [docs meta-store]
+  store/PStore
+  (put-doc! [_ doc]
+    (let [ch (chan 1)]
+      (swap! docs assoc (:id doc) doc)
+      (put! ch true)
+      (async/close! ch)
+      ch))
+
+  (docs-by-prefix [_ prefix]
+    (let [ch (chan 1)
+          matching (->> @docs
+                        vals
+                        (filter #(str/starts-with? (:id %) prefix))
+                        vec)]
+      (put! ch matching)
+      (async/close! ch)
+      ch))
+
+  (get-meta [_ key]
+    (let [ch (chan 1)
+          v  (get @meta-store key)]
+      (if (some? v)
+        (put! ch v)
+        nil)
+      (async/close! ch)
+      ch))
+
+  (set-meta! [_ key value]
+    (let [ch (chan 1)]
+      (swap! meta-store assoc key value)
+      (put! ch true)
+      (async/close! ch)
+      ch))
+
+  (close-store! [_]
+    nil))
+
+(defn create
+  "Create a new in-memory store."
+  []
+  (MemoryStore. (atom {}) (atom {})))
diff --git a/src/pocketbook/sync.cljc b/src/pocketbook/sync.cljc
new file mode 100644
index 0000000..05b8041
--- /dev/null
+++ b/src/pocketbook/sync.cljc
@@ -0,0 +1,160 @@
+(ns pocketbook.sync
+  "HTTP sync client — pull and push documents to/from the Pocketbook server."
+  (:require [pocketbook.transit :as transit]
+            [clojure.string :as str]
+            #?(:clj  [clojure.core.async :as async :refer [chan put!]]
+               :cljs [cljs.core.async :as async :refer [chan put!]]))
+  #?(:clj (:import [java.net URI]
+                    [java.net.http HttpClient HttpRequest HttpRequest$BodyPublishers
+                                   HttpResponse$BodyHandlers])))
+
+;; ---------------------------------------------------------------------------
+;; HTTP helpers
+;; ---------------------------------------------------------------------------
+
+#?(:clj
+   (def ^:private http-client (HttpClient/newHttpClient)))
+
+#?(:clj
+   (defn- http-request
+     "Make an HTTP request with Transit encoding (JVM).
+      Returns {:ok bool :body decoded-value :status int}."
+     [{:keys [url method body]}]
+     (try
+       (let [builder (-> (HttpRequest/newBuilder)
+                         (.uri (URI. url))
+                         (.header "Content-Type" "application/transit+json")
+                         (.header "Accept" "application/transit+json"))
+             req     (case method
+                       :get  (.build (.GET builder))
+                       :post (.build (.POST builder
+                               (HttpRequest$BodyPublishers/ofString
+                                 (transit/encode body)))))
+             resp    (.send http-client req (HttpResponse$BodyHandlers/ofString))]
+         (if (<= 200 (.statusCode resp) 299)
+           {:ok true :body (transit/decode (.body resp))}
+           {:ok false :status (.statusCode resp) :error (.body resp)}))
+       (catch Exception e
+         {:ok false :status 0 :error (str e)}))))
+
+#?(:cljs
+   (defn- fetch-transit
+     "Make an HTTP request with Transit encoding (browser).
+      Returns a channel yielding {:ok bool :body decoded :status int}."
+     [{:keys [url method body]}]
+     (let [ch   (chan 1)
+           opts (clj->js
+                  (cond-> {:method  (or method "GET")
+                           :headers {"Content-Type" "application/transit+json"
+                                     "Accept"       "application/transit+json"}}
+                    body (assoc :body (transit/encode body))))]
+       (-> (js/fetch url opts)
+           (.then (fn [resp]
+                    (-> (.text resp)
+                        (.then (fn [text]
+                                 (if (.-ok resp)
+                                   (put! ch {:ok true :body (transit/decode text)})
+                                   (put! ch {:ok false
+                                             :status (.-status resp)
+                                             :error  text}))
+                                 (async/close! ch))))))
+           (.catch (fn [err]
+                     (put! ch {:ok false :status 0 :error (str err)})
+                     (async/close! ch))))
+       ch)))
+
+;; ---------------------------------------------------------------------------
+;; Pull
+;; ---------------------------------------------------------------------------
+
+(defn pull!
+  "Pull documents from server updated since `since` for `group`.
+   Returns a channel yielding {:ok true :docs [...]} or {:ok false :error str}."
+  [{:keys [server]} group since]
+  (let [url (str server "?group=" #?(:clj (java.net.URLEncoder/encode group "UTF-8")
+                                     :cljs (js/encodeURIComponent group))
+                 "&since=" since)]
+    #?(:clj
+       (async/thread
+         (let [result (http-request {:url url :method :get})]
+           (if (:ok result)
+             {:ok true :docs (:body result)}
+             result)))
+
+       :cljs
+       (let [ch (chan 1)]
+         (async/go
+           (let [result (async/<! (fetch-transit {:url url :method "GET"}))]
+             (if (:ok result)
+               (put! ch {:ok true :docs (:body result)})
+               (put! ch result))
+             (async/close! ch)))
+         ch))))
+
+;; ---------------------------------------------------------------------------
+;; Push
+;; ---------------------------------------------------------------------------
+
+(defn push!
+  "Push a batch of documents to the server.
+   Returns a channel yielding {:ok true :results [...]} or {:ok false :error str}."
+  [{:keys [server]} docs]
+  #?(:clj
+     (async/thread
+       (let [result (http-request {:url server :method :post :body docs})]
+         (if (:ok result)
+           {:ok true :results (:body result)}
+           result)))
+
+     :cljs
+     (let [ch (chan 1)]
+       (async/go
+         (let [result (async/<! (fetch-transit {:url server :method "POST" :body docs}))]
+           (if (:ok result)
+             (put! ch {:ok true :results (:body result)})
+             (put! ch result))
+           (async/close! ch)))
+       ch)))
+
+;; ---------------------------------------------------------------------------
+;; SSE — live change notifications (CLJS only)
+;; ---------------------------------------------------------------------------
+
+#?(:cljs
+   (defn listen-events
+     "Open an SSE connection to /events?group=G. Calls `on-change` when the
+      server signals new data. Returns a cleanup function."
+     [{:keys [server]} group on-change]
+     (let [base-url (-> server
+                        (str/replace #"/sync$" "")
+                        (str/replace #"/$" ""))
+           url      (str base-url "/events?group=" (js/encodeURIComponent group))
+           es       (js/EventSource. url)]
+       (set! (.-onmessage es)
+         (fn [e]
+           (on-change (.-data e))))
+       (set! (.-onerror es)
+         (fn [_e] nil))
+       (fn []
+         (.close es)))))
+
+;; ---------------------------------------------------------------------------
+;; Online detection
+;; ---------------------------------------------------------------------------
+
+(defn online? []
+  #?(:clj  true
+     :cljs (.-onLine js/navigator)))
+
+(defn on-connectivity-change
+  "Register callbacks for online/offline events. Returns a cleanup fn.
+   On JVM, this is a no-op (always online)."
+  [on-online on-offline]
+  #?(:clj  (fn [])
+     :cljs (let [online-handler  (fn [_] (on-online))
+                 offline-handler (fn [_] (on-offline))]
+             (.addEventListener js/window "online" online-handler)
+             (.addEventListener js/window "offline" offline-handler)
+             (fn []
+               (.removeEventListener js/window "online" online-handler)
+               (.removeEventListener js/window "offline" offline-handler)))))
diff --git a/src/pocketbook/sync.cljs b/src/pocketbook/sync.cljs
deleted file mode 100644
index 06538d3..0000000
--- a/src/pocketbook/sync.cljs
+++ /dev/null
@@ -1,137 +0,0 @@
-(ns pocketbook.sync
-  "HTTP sync client — pull and push documents to/from the Pocketbook server."
-  (:require [cognitect.transit :as t]
-            [clojure.string :as str]
-            [cljs.core.async :as async :refer [chan put!]]))
-
-;; ---------------------------------------------------------------------------
-;; Transit over HTTP
-;; ---------------------------------------------------------------------------
-
-(def ^:private writer (t/writer :json))
-(def ^:private reader (t/reader :json))
-
-(defn- encode [v]
-  (t/write writer v))
-
-(defn- decode [s]
-  (when (and s (not= s ""))
-    (t/read reader s)))
-
-;; ---------------------------------------------------------------------------
-;; HTTP helpers
-;; ---------------------------------------------------------------------------
-
-(defn- fetch-transit
-  "Make an HTTP request with Transit encoding. Returns a channel
-   yielding {:ok true :body <decoded>} or {:ok false :status N :error str}."
-  [{:keys [url method body headers]}]
-  (let [ch (chan 1)
-        opts (clj->js
-               (cond-> {:method  (or method "GET")
-                         :headers (merge {"Content-Type" "application/transit+json"
-                                          "Accept"       "application/transit+json"}
-                                         headers)}
-                 body (assoc :body (encode body))))]
-    (-> (js/fetch url opts)
-        (.then (fn [resp]
-                 (-> (.text resp)
-                     (.then (fn [text]
-                              (if (.-ok resp)
-                                (put! ch {:ok true :body (decode text)})
-                                (put! ch {:ok false
-                                          :status (.-status resp)
-                                          :error  text}))
-                              (async/close! ch))))))
-        (.catch (fn [err]
-                  (put! ch {:ok false :status 0 :error (str err)})
-                  (async/close! ch))))
-    ch))
-
-;; ---------------------------------------------------------------------------
-;; Pull
-;; ---------------------------------------------------------------------------
-
-(defn pull!
-  "Pull documents from server updated since `since` for `group`.
-   Returns a channel yielding {:ok true :docs [...]} or {:ok false :error str}."
-  [{:keys [server]} group since]
-  (let [ch  (chan 1)
-        url (str server "?group=" (js/encodeURIComponent group)
-                 "&since=" since)]
-    (async/go
-      (let [result (async/<! (fetch-transit
-                     {:url     url
-                      :method  "GET"}))]
-        (if (:ok result)
-          (put! ch {:ok true :docs (:body result)})
-          (put! ch result))
-        (async/close! ch)))
-    ch))
-
-;; ---------------------------------------------------------------------------
-;; Push
-;; ---------------------------------------------------------------------------
-
-(defn push!
-  "Push a batch of documents to the server.
-   Each doc: {:id str :value any :base-version int} or {:id str :deleted true :base-version int}.
-   Returns a channel yielding {:ok true :results [...]} or {:ok false :error str}."
-  [{:keys [server]} docs]
-  (let [ch (chan 1)]
-    (async/go
-      (let [result (async/<! (fetch-transit
-                     {:url     server
-                      :method  "POST"
-                      :body    docs}))]
-        (if (:ok result)
-          (put! ch {:ok true :results (:body result)})
-          (put! ch result))
-        (async/close! ch)))
-    ch))
-
-;; ---------------------------------------------------------------------------
-;; SSE — live change notifications
-;; ---------------------------------------------------------------------------
-
-(defn listen-events
-  "Open an SSE connection to /events?group=G. Calls `on-change` when the
-   server signals new data. Returns a cleanup function."
-  [{:keys [server]} group on-change]
-  (let [base-url (-> server
-                     (str/replace #"/sync$" "")
-                     (str/replace #"/$" ""))
-        url      (str base-url "/events?group=" (js/encodeURIComponent group))
-        es       (js/EventSource. url)]
-    (set! (.-onmessage es)
-      (fn [e]
-        (let [data (.-data e)]
-          ;; "connected" fires on initial connect AND every reconnect
-          ;; Always trigger a sync — picks up missed changes after reconnect
-          (on-change data))))
-    (set! (.-onerror es)
-      (fn [_e]
-        ;; EventSource auto-reconnects; nothing to do
-        nil))
-    ;; Return cleanup
-    (fn []
-      (.close es))))
-
-;; ---------------------------------------------------------------------------
-;; Online detection
-;; ---------------------------------------------------------------------------
-
-(defn online? []
-  (.-onLine js/navigator))
-
-(defn on-connectivity-change
-  "Register callbacks for online/offline events. Returns a cleanup fn."
-  [on-online on-offline]
-  (let [online-handler  (fn [_] (on-online))
-        offline-handler (fn [_] (on-offline))]
-    (.addEventListener js/window "online" online-handler)
-    (.addEventListener js/window "offline" offline-handler)
-    ;; Return cleanup function
-    (fn []
-      (.removeEventListener js/window "online" online-handler)
-      (.removeEventListener js/window "offline" offline-handler))))
diff --git a/src/pocketbook/transit.clj b/src/pocketbook/transit.clj
deleted file mode 100644
index b19a570..0000000
--- a/src/pocketbook/transit.clj
+++ /dev/null
@@ -1,32 +0,0 @@
-(ns pocketbook.transit
-  "Transit encoding/decoding helpers for the HTTP wire format."
-  (:require [cognitect.transit :as t])
-  (:import [java.io ByteArrayInputStream ByteArrayOutputStream]))
-
-(defn encode
-  "Encode a Clojure value to a Transit+JSON byte array."
-  [v]
-  (let [out (ByteArrayOutputStream. 4096)
-        w   (t/writer out :json)]
-    (t/write w v)
-    (.toByteArray out)))
-
-(defn encode-str
-  "Encode a Clojure value to a Transit+JSON string."
-  [v]
-  (let [out (ByteArrayOutputStream. 4096)
-        w   (t/writer out :json)]
-    (t/write w v)
-    (.toString out "UTF-8")))
-
-(defn decode
-  "Decode a Transit+JSON byte array or input stream to a Clojure value."
-  [input]
-  (let [in (cond
-             (instance? ByteArrayInputStream input) input
-             (instance? java.io.InputStream input)  input
-             (bytes? input) (ByteArrayInputStream. input)
-             (string? input) (ByteArrayInputStream. (.getBytes ^String input "UTF-8"))
-             :else (throw (ex-info "Cannot decode, unsupported input type"
-                                   {:type (type input)})))]
-    (t/read (t/reader in :json))))
diff --git a/src/pocketbook/transit.cljc b/src/pocketbook/transit.cljc
new file mode 100644
index 0000000..1968051
--- /dev/null
+++ b/src/pocketbook/transit.cljc
@@ -0,0 +1,31 @@
+(ns pocketbook.transit
+  "Transit encoding/decoding helpers for the HTTP wire format."
+  (:require [cognitect.transit :as t])
+  #?(:clj (:import [java.io ByteArrayInputStream ByteArrayOutputStream])))
+
+(defn encode
+  "Encode a Clojure value to a Transit+JSON string."
+  [v]
+  #?(:clj  (let [out (ByteArrayOutputStream. 4096)
+                  w   (t/writer out :json)]
+              (t/write w v)
+              (.toString out "UTF-8"))
+     :cljs (t/write (t/writer :json) v)))
+
+(defn decode
+  "Decode Transit+JSON to a Clojure value.
+   Accepts a string on both platforms; on CLJ also accepts byte arrays and InputStreams."
+  [input]
+  #?(:clj  (cond
+              (nil? input) nil
+              (string? input)
+              (when (not= input "")
+                (t/read (t/reader (ByteArrayInputStream. (.getBytes ^String input "UTF-8")) :json)))
+              (instance? java.io.InputStream input)
+              (t/read (t/reader input :json))
+              (bytes? input)
+              (t/read (t/reader (ByteArrayInputStream. input) :json))
+              :else (throw (ex-info "Cannot decode, unsupported input type"
+                                    {:type (type input)})))
+     :cljs (when (and input (not= input ""))
+              (t/read (t/reader :json) input))))
diff --git a/test/pocketbook/core_test.clj b/test/pocketbook/core_test.clj
new file mode 100644
index 0000000..775abec
--- /dev/null
+++ b/test/pocketbook/core_test.clj
@@ -0,0 +1,185 @@
+(ns pocketbook.core-test
+  (:require [clojure.test :refer [deftest is testing use-fixtures]]
+            [clojure.core.async :as async :refer [<!! go <! timeout]]
+            [pocketbook.core :as pb]
+            [pocketbook.store :as store]
+            [pocketbook.store.memory :as memory]
+            [pocketbook.server :as server])
+  (:import [java.io File]))
+
+;; ---------------------------------------------------------------------------
+;; Fixtures — start a real server for sync tests
+;; ---------------------------------------------------------------------------
+
+(def ^:dynamic *port* nil)
+(def ^:dynamic *server* nil)
+
+(defn- free-port []
+  (with-open [s (java.net.ServerSocket. 0)]
+    (.getLocalPort s)))
+
+(use-fixtures :each
+  (fn [f]
+    (let [port    (free-port)
+          db-path (str (File/createTempFile "pocketbook-core-test" ".db"))
+          srv     (server/start! {:port port :db-path db-path})]
+      (Thread/sleep 200)
+      (try
+        (binding [*server* srv *port* port]
+          (f))
+        (finally
+          (server/stop! srv)
+          (.delete (File. db-path)))))))
+
+(defn- server-url []
+  (str "http://localhost:" *port* "/sync"))
+
+;; ---------------------------------------------------------------------------
+;; Helpers
+;; ---------------------------------------------------------------------------
+
+(defn- <!!timeout
+  "Take from channel with timeout. Returns nil on timeout."
+  [ch ms]
+  (let [[v _] (<!! (go (async/alts! [ch (timeout ms)])))]
+    v))
+
+(defn- wait-synced
+  "Wait until the synced atom has no pending changes."
+  [sa ms]
+  (let [deadline (+ (System/currentTimeMillis) ms)]
+    (loop []
+      (when (and (pos? (pb/pending-count sa))
+                 (< (System/currentTimeMillis) deadline))
+        (Thread/sleep 50)
+        (recur)))))
+
+;; ---------------------------------------------------------------------------
+;; Tests
+;; ---------------------------------------------------------------------------
+
+(deftest synced-atom-local-only
+  (testing "SyncedAtom works without a server (local store only)"
+    (let [store (memory/create)
+          sa    (pb/synced-atom store "todo")]
+      (<!!timeout (pb/ready? sa) 1000)
+      (is (= {} @sa))
+
+      (swap! sa assoc "todo:1" {:text "Buy milk"})
+      (is (= {:text "Buy milk"} (get @sa "todo:1")))
+
+      (swap! sa assoc "todo:2" {:text "Walk dog"})
+      (is (= 2 (count @sa)))
+
+      (swap! sa dissoc "todo:1")
+      (is (= 1 (count @sa)))
+      (is (nil? (get @sa "todo:1")))
+
+      (pb/destroy! sa))))
+
+(deftest synced-atom-persists-to-store
+  (testing "Changes are persisted to the store"
+    (let [store (memory/create)
+          sa    (pb/synced-atom store "todo")]
+      (<!!timeout (pb/ready? sa) 1000)
+
+      (swap! sa assoc "todo:1" {:text "Buy milk"})
+      (Thread/sleep 50) ;; let async store write complete
+
+      ;; Read from store directly
+      (let [docs (<!!timeout (store/docs-by-prefix store "todo:") 1000)]
+        (is (= 1 (count docs)))
+        (is (= "todo:1" (:id (first docs))))
+        (is (= {:text "Buy milk"} (:value (first docs)))))
+
+      (pb/destroy! sa))))
+
+(deftest synced-atom-loads-from-store
+  (testing "SyncedAtom loads existing data from store on creation"
+    (let [store (memory/create)]
+      ;; Pre-populate the store
+      (<!!timeout (store/put-doc! store
+                    {:id "todo:1" :value {:text "Existing"}
+                     :version 1 :updated 1000 :deleted false :synced true})
+                  1000)
+
+      (let [sa (pb/synced-atom store "todo")]
+        (<!!timeout (pb/ready? sa) 1000)
+        (is (= {:text "Existing"} (get @sa "todo:1")))
+        (pb/destroy! sa)))))
+
+(deftest synced-atom-watches
+  (testing "add-watch fires on changes"
+    (let [store   (memory/create)
+          sa      (pb/synced-atom store "todo")
+          changes (atom [])]
+      (<!!timeout (pb/ready? sa) 1000)
+
+      (add-watch sa :test (fn [_ _ old new]
+                            (swap! changes conj {:old old :new new})))
+
+      (swap! sa assoc "todo:1" {:text "Hello"})
+      (Thread/sleep 50)
+
+      (is (= 1 (count @changes)))
+      (is (= {} (:old (first @changes))))
+      (is (= {"todo:1" {:text "Hello"}} (:new (first @changes))))
+
+      (remove-watch sa :test)
+      (pb/destroy! sa))))
+
+(deftest synced-atom-push-to-server
+  (testing "Local changes are pushed to the server"
+    (let [store (memory/create)
+          sa    (pb/synced-atom store "todo"
+                  {:server (server-url)})]
+      (<!!timeout (pb/ready? sa) 2000)
+
+      (swap! sa assoc "todo:push1" {:text "Pushed!"})
+      (Thread/sleep 500) ;; let push complete
+
+      (is (zero? (pb/pending-count sa)))
+      (pb/destroy! sa))))
+
+(deftest synced-atom-pull-from-server
+  (testing "Two clients sync via server"
+    (let [store-a (memory/create)
+          store-b (memory/create)
+          sa-a    (pb/synced-atom store-a "todo"
+                    {:server (server-url) :interval 500})
+          sa-b    (pb/synced-atom store-b "todo"
+                    {:server (server-url) :interval 500})]
+      (<!!timeout (pb/ready? sa-a) 2000)
+      (<!!timeout (pb/ready? sa-b) 2000)
+
+      ;; Client A writes
+      (swap! sa-a assoc "todo:sync1" {:text "From A"})
+      (Thread/sleep 500) ;; let A push
+
+      ;; Trigger a sync on B
+      (<!!timeout (pb/sync-now! sa-b) 2000)
+
+      ;; B should have A's data
+      (is (= {:text "From A"} (get @sa-b "todo:sync1")))
+
+      (pb/destroy! sa-a)
+      (pb/destroy! sa-b))))
+
+(deftest synced-atom-deref-swap-reset
+  (testing "Standard atom operations work"
+    (let [store (memory/create)
+          sa    (pb/synced-atom store "note")]
+      (<!!timeout (pb/ready? sa) 1000)
+
+      ;; reset!
+      (reset! sa {"note:1" {:body "Hello"}})
+      (is (= {"note:1" {:body "Hello"}} @sa))
+
+      ;; swap! with multiple args
+      (swap! sa assoc "note:2" {:body "World"})
+      (is (= 2 (count @sa)))
+
+      (swap! sa update "note:1" assoc :edited true)
+      (is (true? (:edited (get @sa "note:1"))))
+
+      (pb/destroy! sa))))
diff --git a/test/pocketbook/server_test.clj b/test/pocketbook/server_test.clj
index c76f772..fe12215 100644
--- a/test/pocketbook/server_test.clj
+++ b/test/pocketbook/server_test.clj
@@ -41,19 +41,19 @@
                 (.header "Accept" "application/transit+json")
                 (.GET)
                 (.build))
-        resp (.send client req (HttpResponse$BodyHandlers/ofByteArray))]
+        resp (.send client req (HttpResponse$BodyHandlers/ofString))]
     {:status (.statusCode resp)
      :body   (t/decode (.body resp))}))
 
 (defn- post-transit [path body]
-  (let [bytes (t/encode body)
-        req   (-> (HttpRequest/newBuilder)
-                  (.uri (URI. (url path)))
-                  (.header "Content-Type" "application/transit+json")
-                  (.header "Accept" "application/transit+json")
-                  (.POST (HttpRequest$BodyPublishers/ofByteArray bytes))
-                  (.build))
-        resp  (.send client req (HttpResponse$BodyHandlers/ofByteArray))]
+  (let [encoded (t/encode body)
+        req     (-> (HttpRequest/newBuilder)
+                    (.uri (URI. (url path)))
+                    (.header "Content-Type" "application/transit+json")
+                    (.header "Accept" "application/transit+json")
+                    (.POST (HttpRequest$BodyPublishers/ofString encoded))
+                    (.build))
+        resp    (.send client req (HttpResponse$BodyHandlers/ofString))]
     {:status (.statusCode resp)
      :body   (t/decode (.body resp))}))
 
diff --git a/test/pocketbook/transit_test.clj b/test/pocketbook/transit_test.clj
index f98e32a..59e62f4 100644
--- a/test/pocketbook/transit_test.clj
+++ b/test/pocketbook/transit_test.clj
@@ -30,8 +30,8 @@
                :version 5}]]
     (is (= data (t/decode (t/encode data))))))
 
-(deftest encode-str-roundtrip
+(deftest encode-returns-string
   (let [v {:hello "world" :nums [1 2 3]}
-        s (t/encode-str v)]
+        s (t/encode v)]
     (is (string? s))
     (is (= v (t/decode s)))))