diff --git a/hbs2-storage-simple/hbs2-storage-simple.cabal b/hbs2-storage-simple/hbs2-storage-simple.cabal
index 4e72cc19..da62c866 100644
--- a/hbs2-storage-simple/hbs2-storage-simple.cabal
+++ b/hbs2-storage-simple/hbs2-storage-simple.cabal
@@ -76,6 +76,7 @@ library
                     , mtl
                     , prettyprinter
                     , random
+                    , safe
                     , stm
                     , stm-chans
                     , streaming
diff --git a/hbs2-storage-simple/lib/HBS2/Storage/Compact.hs b/hbs2-storage-simple/lib/HBS2/Storage/Compact.hs
index 376e5e96..7e968a54 100644
--- a/hbs2-storage-simple/lib/HBS2/Storage/Compact.hs
+++ b/hbs2-storage-simple/lib/HBS2/Storage/Compact.hs
@@ -26,6 +26,7 @@ import Control.Monad.Except
 import Control.Monad.Trans.Maybe
 import Control.Monad
 import Control.Concurrent.STM.TSem
+import Safe
 import UnliftIO
 
 import Debug.Trace
@@ -75,7 +76,6 @@ data Header =
   , hdrFwdOffset    :: FwdEntryOffset
   , hdrIndexOffset  :: EntryOffset
   , hdrIndexEntries :: EntryNum
-  , hdrGen          :: Word32
   , hdrPrev         :: EntryOffset
   }
   deriving stock (Show,Generic)
@@ -84,7 +84,6 @@ data CompactStorage =
   CompactStorage
   { csHandle     :: MVar Handle
   , csHeaderOff  :: IORef EntryOffset
-  , csHeaderGen  :: IORef Word32
   , csSeq        :: IORef Integer
   , csKeys       :: IORef (HashMap ByteString (Either (IndexEntry,Integer) (ByteString,Integer)))
   }
@@ -96,6 +95,7 @@ data CompactStorageOpenOpt
 data CompactStorageOpenError =
          InvalidHeader
        | BrokenIndex
+       | InvalidFwdSection
   deriving stock (Typeable,Show)
 
 instance Exception CompactStorageOpenError
@@ -114,37 +114,26 @@ compactStorageOpen _ fp = do
   hoff0 <- newIORef 0
   keys0 <- newIORef mempty
   ss    <- newIORef 0
-  gen0  <- newIORef 0
 
   if sz == 0 then
-    pure $ CompactStorage mha hoff0 gen0 ss keys0
+    pure $ CompactStorage mha hoff0 ss keys0
   else do
     (p,header) <- readHeader mha Nothing >>= maybe (throwIO InvalidHeader) pure
     traceM (show ("HEADER",header))
     hoff <- newIORef p
-    let sto = CompactStorage mha hoff gen0 ss keys0
-    updateHeaderGen sto header
+    let sto = CompactStorage mha hoff ss keys0
     readIndex sto (hdrIndexOffset header) (hdrIndexEntries header)
 
     flip fix (hdrPrev header) $ \next -> \case
       0   -> pure ()
       off ->  do
         (_,pHeader) <- readHeader mha (Just off) >>= maybe (throwIO InvalidHeader) pure
-        updateHeaderGen sto pHeader
         traceM (show ("PHEADER",pHeader))
         readIndex sto (hdrIndexOffset pHeader) (hdrIndexEntries pHeader)
         next (hdrPrev pHeader)
 
     pure sto
 
-  where
-
-    updateHeaderGen :: ForCompactStorage m
-                     => CompactStorage
-                     -> Header
-                     -> m ()
-    updateHeaderGen sto hdr = do
-      writeIORef (csHeaderGen sto) (hdrGen hdr)
 
 readIndex :: ForCompactStorage m
           => CompactStorage
@@ -199,7 +188,7 @@ compactStorageCommit sto = liftIO do
       offFwd <- hTell ha
       LBS.hPut ha (toLazyByteString $ word64BE 0)
 
-      off0 <- hTell ha
+      let off0 = offFwd + 8
 
       -- write data
       idxEntries <- flip fix (off0, items, mempty) $ \next (off, what, idx) -> do
@@ -221,15 +210,14 @@ compactStorageCommit sto = liftIO do
 
       offPrev <- readIORef (csHeaderOff sto)
 
-      pver <- atomicModifyIORef' (csHeaderGen sto) (\v -> (v+1, v))
-      -- FIXME: maybe-slow-length-calc
-      appendHeader ha (fromIntegral offFwd) (Just offPrev) pver offIdx0 (fromIntegral $ length idxEntries)
-
       offCommitHead <- hTell ha
 
+      -- FIXME: maybe-slow-length-calc
+      appendHeader ha (fromIntegral offFwd) (Just offPrev) offIdx0 (fromIntegral $ length idxEntries)
+
       hSeek ha AbsoluteSeek offFwd
 
-      LBS.hPut ha (toLazyByteString $ word16BE (fromIntegral offCommitHead))
+      LBS.hPut ha (toLazyByteString $ word64BE (fromIntegral offCommitHead))
 
       hFlush ha
 
@@ -275,23 +263,57 @@ compactStorageClose sto = do
   -- FIXME: hangs-forever-on-io-exception
   liftIO $ withMVar (csHandle sto) hClose
 
+compactStorageFindLiveHeads :: ForCompactStorage m
+                             => FilePath
+                             -> m [(EntryOffset, Header)]
+
+compactStorageFindLiveHeads path = liftIO do
+  withFile path ReadMode $ \ha -> do
+
+    mv <- newMVar ha
+
+    flip fix (mempty :: [(EntryOffset, Header)]) $ \next acc -> do
+
+      what <- runMaybeT do
+
+        fwdOff <- hTell ha
+
+        -- fwd section
+        fwd <- lift (LBS.hGet ha 8)
+                 <&> runGetOrFail getWord64be
+                 >>= either (const mzero) pure
+                 <&> view _3
+
+        traceM $ show ("JOPA1", fwdOff, fwd)
+
+        h@(o,header) <- MaybeT $ readHeader mv (Just $ fromIntegral fwd)
+
+
+        let magicOk = hdrMagic header == headerMagic
+        let fwdOk   = hdrFwdOffset header == fromIntegral fwdOff
+
+        if magicOk && fwdOk then
+          pure h
+        else
+          mzero
+
+      maybe (pure acc) (\h -> next ( h : acc) ) what
+
+
 appendHeader :: ForCompactStorage m
              => Handle
              -> FwdEntryOffset     -- fwd section offset
              -> Maybe EntryOffset  -- prev. header
-             -> Word32             -- prev. header version
              -> EntryOffset
              -> EntryNum
              -> m ()
-appendHeader ha fwdOff poffset v ioffset num = do
+appendHeader ha fwdOff poffset ioffset num = do
   let bs =   word16BE headerMagic                     -- 2
           <> word16BE headerVersion                   -- 4
           <> word64BE (coerce fwdOff)                 -- 12
           <> word64BE (coerce ioffset)                -- 20
           <> word32BE (coerce num)                    -- 24
-          <> word32BE v                               -- 28
-          <> word64BE (coerce $ fromMaybe 0 poffset)  -- 36
-          <> byteString (BS.replicate 4 0)            -- 40
+          <> word64BE (coerce $ fromMaybe 0 poffset)  -- 32
   liftIO $ LBS.hPut ha (B.toLazyByteString bs)
 
 readHeader :: ForCompactStorage m
@@ -317,7 +339,6 @@ readHeader mha moff = do
                        <*> getFwdOffset
                        <*> getOffset
                        <*> getNum
-                       <*> getWord32be
                        <*> getOffset
 
   pure $ either (const Nothing) (fmap (off,) . Just . view _3) what
@@ -334,7 +355,7 @@ headerVersion :: Word16
 headerVersion = 1
 
 headerSize :: Integral a => Word16 -> a
-headerSize 1 = fromIntegral (40 :: Integer)
+headerSize 1 = fromIntegral (32 :: Integer)
 headerSize _ = error "unsupported header version"