diff --git a/codex.nim b/codex.nim
index 79e0ef68..4ef01299 100644
--- a/codex.nim
+++ b/codex.nim
@@ -48,7 +48,7 @@ when isMainModule:
   let config = CodexConf.load(
     version = codexFullVersion,
     envVarsPrefix = "codex",
-    secondarySources = proc (config: CodexConf, sources: auto) =
+    secondarySources = proc (config: CodexConf, sources: auto) {.gcsafe, raises: [ConfigurationError].} =
             if configFile =? config.configFile:
               sources.addConfigFile(Toml, configFile)
   )
diff --git a/codex/clock.nim b/codex/clock.nim
index f680ddec..933cd199 100644
--- a/codex/clock.nim
+++ b/codex/clock.nim
@@ -8,7 +8,7 @@ type
   SecondsSince1970* = int64
   Timeout* = object of CatchableError
 
-method now*(clock: Clock): SecondsSince1970 {.base, upraises: [].} =
+method now*(clock: Clock): SecondsSince1970 {.base, gcsafe, upraises: [].} =
   raiseAssert "not implemented"
 
 method waitUntil*(clock: Clock, time: SecondsSince1970) {.base, async.} =
diff --git a/codex/discovery.nim b/codex/discovery.nim
index 47ac950d..277080f5 100644
--- a/codex/discovery.nim
+++ b/codex/discovery.nim
@@ -124,7 +124,7 @@ method provide*(d: Discovery, host: ca.Address) {.async, base.} =
 
 method removeProvider*(
   d: Discovery,
-  peerId: PeerId): Future[void] {.base.} =
+  peerId: PeerId): Future[void] {.base, gcsafe.} =
   ## Remove provider from providers table
   ##
 
diff --git a/codex/erasure/backend.nim b/codex/erasure/backend.nim
index 728c8bed..873d800e 100644
--- a/codex/erasure/backend.nim
+++ b/codex/erasure/backend.nim
@@ -22,7 +22,7 @@ type
   EncoderBackend* = ref object of ErasureBackend
   DecoderBackend* = ref object of ErasureBackend
 
-method release*(self: ErasureBackend) {.base.} =
+method release*(self: ErasureBackend) {.base, gcsafe.} =
   ## release the backend
   ##
   raiseAssert("not implemented!")
@@ -31,7 +31,7 @@ method encode*(
     self: EncoderBackend,
     buffers,
     parity: var openArray[seq[byte]]
-): Result[void, cstring] {.base.} =
+): Result[void, cstring] {.base, gcsafe.} =
   ## encode buffers using a backend
   ##
   raiseAssert("not implemented!")
@@ -41,7 +41,7 @@ method decode*(
     buffers,
     parity,
     recovered: var openArray[seq[byte]]
-): Result[void, cstring] {.base.} =
+): Result[void, cstring] {.base, gcsafe.} =
   ## decode buffers using a backend
   ##
   raiseAssert("not implemented!")
diff --git a/codex/stores/blockstore.nim b/codex/stores/blockstore.nim
index 52f37517..d3eafc06 100644
--- a/codex/stores/blockstore.nim
+++ b/codex/stores/blockstore.nim
@@ -33,13 +33,13 @@ type
   BlockStore* = ref object of RootObj
     onBlockStored*: ?CidCallback
 
-method getBlock*(self: BlockStore, cid: Cid): Future[?!Block] {.base.} =
+method getBlock*(self: BlockStore, cid: Cid): Future[?!Block] {.base, gcsafe.} =
   ## Get a block from the blockstore
   ##
 
   raiseAssert("getBlock by cid not implemented!")
 
-method getBlock*(self: BlockStore, treeCid: Cid, index: Natural): Future[?!Block] {.base.} =
+method getBlock*(self: BlockStore, treeCid: Cid, index: Natural): Future[?!Block] {.base, gcsafe.} =
   ## Get a block from the blockstore
   ##
 
@@ -50,13 +50,13 @@ method getCid*(self: BlockStore, treeCid: Cid, index: Natural): Future[?!Cid] {.
   ##
   raiseAssert("getCid by treecid not implemented!")
 
-method getBlock*(self: BlockStore, address: BlockAddress): Future[?!Block] {.base.} =
+method getBlock*(self: BlockStore, address: BlockAddress): Future[?!Block] {.base, gcsafe.} =
   ## Get a block from the blockstore
   ##
 
   raiseAssert("getBlock by addr not implemented!")
 
-method getBlockAndProof*(self: BlockStore, treeCid: Cid, index: Natural): Future[?!(Block, CodexProof)] {.base.} =
+method getBlockAndProof*(self: BlockStore, treeCid: Cid, index: Natural): Future[?!(Block, CodexProof)] {.base, gcsafe.} =
   ## Get a block and associated inclusion proof by Cid of a merkle tree and an index of a leaf in a tree
   ##
 
@@ -65,7 +65,7 @@ method getBlockAndProof*(self: BlockStore, treeCid: Cid, index: Natural): Future
 method putBlock*(
   self: BlockStore,
   blk: Block,
-  ttl = Duration.none): Future[?!void] {.base.} =
+  ttl = Duration.none): Future[?!void] {.base, gcsafe.} =
   ## Put a block to the blockstore
   ##
 
@@ -76,7 +76,7 @@ method putCidAndProof*(
   treeCid: Cid,
   index: Natural,
   blockCid: Cid,
-  proof: CodexProof): Future[?!void] {.base.} =
+  proof: CodexProof): Future[?!void] {.base, gcsafe.} =
   ## Put a block proof to the blockstore
   ##
 
@@ -85,7 +85,7 @@ method putCidAndProof*(
 method getCidAndProof*(
   self: BlockStore,
   treeCid: Cid,
-  index: Natural): Future[?!(Cid, CodexProof)] {.base.} =
+  index: Natural): Future[?!(Cid, CodexProof)] {.base, gcsafe.} =
   ## Get a block proof from the blockstore
   ##
 
@@ -94,7 +94,7 @@ method getCidAndProof*(
 method ensureExpiry*(
   self: BlockStore,
   cid: Cid,
-  expiry: SecondsSince1970): Future[?!void] {.base.} =
+  expiry: SecondsSince1970): Future[?!void] {.base, gcsafe.} =
   ## Ensure that block's assosicated expiry is at least given timestamp
   ## If the current expiry is lower then it is updated to the given one, otherwise it is left intact
   ##
@@ -105,7 +105,7 @@ method ensureExpiry*(
   self: BlockStore,
   treeCid: Cid,
   index: Natural,
-  expiry: SecondsSince1970): Future[?!void] {.base.} =
+  expiry: SecondsSince1970): Future[?!void] {.base, gcsafe.} =
   ## Ensure that block's associated expiry is at least given timestamp
   ## If the current expiry is lower then it is updated to the given one, otherwise it is left intact
   ##
@@ -124,13 +124,13 @@ method delBlock*(self: BlockStore, treeCid: Cid, index: Natural): Future[?!void]
 
   raiseAssert("delBlock not implemented!")
 
-method hasBlock*(self: BlockStore, cid: Cid): Future[?!bool] {.base.} =
+method hasBlock*(self: BlockStore, cid: Cid): Future[?!bool] {.base, gcsafe.} =
   ## Check if the block exists in the blockstore
   ##
 
   raiseAssert("hasBlock not implemented!")
 
-method hasBlock*(self: BlockStore, tree: Cid, index: Natural): Future[?!bool] {.base.} =
+method hasBlock*(self: BlockStore, tree: Cid, index: Natural): Future[?!bool] {.base, gcsafe.} =
   ## Check if the block exists in the blockstore
   ##
 
@@ -138,13 +138,13 @@ method hasBlock*(self: BlockStore, tree: Cid, index: Natural): Future[?!bool] {.
 
 method listBlocks*(
   self: BlockStore,
-  blockType = BlockType.Manifest): Future[?!AsyncIter[?Cid]] {.base.} =
+  blockType = BlockType.Manifest): Future[?!AsyncIter[?Cid]] {.base, gcsafe.} =
   ## Get the list of blocks in the BlockStore. This is an intensive operation
   ##
 
   raiseAssert("listBlocks not implemented!")
 
-method close*(self: BlockStore): Future[void] {.base.} =
+method close*(self: BlockStore): Future[void] {.base, gcsafe.} =
   ## Close the blockstore, cleaning up resources managed by it.
   ## For some implementations this may be a no-op
   ##
diff --git a/codex/utils/timer.nim b/codex/utils/timer.nim
index 9361d07b..b7457038 100644
--- a/codex/utils/timer.nim
+++ b/codex/utils/timer.nim
@@ -40,7 +40,7 @@ proc timerLoop(timer: Timer) {.async.} =
   except CatchableError as exc:
     error "Timer caught unhandled exception: ", name=timer.name, msg=exc.msg
 
-method start*(timer: Timer, callback: TimerCallback, interval: Duration) {.base.} =
+method start*(timer: Timer, callback: TimerCallback, interval: Duration) {.gcsafe, base.} =
   if timer.loopFuture != nil:
     return
   trace "Timer starting: ", name=timer.name