diff --git a/nitro.nimble b/nitro.nimble
index 409d9b4..f293951 100644
--- a/nitro.nimble
+++ b/nitro.nimble
@@ -5,9 +5,9 @@ description = "Nitro state channels"
 
 requires "nim >= 1.2.6 & < 2.0.0"
 requires "nimcrypto >= 0.5.4 & < 0.6.0"
-requires "questionable >= 0.9.1 & < 0.10.0"
+requires "questionable >= 0.10.1 & < 0.11.0"
 requires "upraises >= 0.1.0 & < 0.2.0"
-requires "https://github.com/status-im/nim-contract-abi >= 0.1.0 & < 0.2.0"
+requires "https://github.com/status-im/nim-contract-abi >= 0.3.0 & < 0.4.0"
 requires "secp256k1"
 requires "stint"
 requires "stew"
diff --git a/nitro/protocol/channel.nim b/nitro/protocol/channel.nim
index ca95cb8..7f95ccd 100644
--- a/nitro/protocol/channel.nim
+++ b/nitro/protocol/channel.nim
@@ -13,10 +13,6 @@ type
     chainId*: UInt256
 
 func getChannelId*(channel: ChannelDefinition): Destination =
-  var encoder= AbiEncoder.init()
-  encoder.startTuple()
-  encoder.write(channel.chainId)
-  encoder.write(channel.participants)
-  encoder.write(channel.nonce)
-  encoder.finishTuple()
-  Destination(keccak256.digest(encoder.finish()).data)
+  let encoding = AbiEncoder.encode:
+     (channel.chainId, channel.participants, channel.nonce)
+  Destination(keccak256.digest(encoding).data)
diff --git a/nitro/protocol/outcome.nim b/nitro/protocol/outcome.nim
index 069e61a..5ff07fa 100644
--- a/nitro/protocol/outcome.nim
+++ b/nitro/protocol/outcome.nim
@@ -52,46 +52,25 @@ func `==`*(a, b: AssetOutcome): bool =
 proc `==`*(a, b: Outcome): bool {.borrow.}
 
 func encode*(encoder: var AbiEncoder, guarantee: Guarantee) =
-  encoder.startTuple()
-  encoder.startTuple()
-  encoder.write(guarantee.targetChannelId)
-  encoder.write(guarantee.destinations)
-  encoder.finishTuple()
-  encoder.finishTuple()
-
-func encode*(encoder: var AbiEncoder, item: AllocationItem) =
-  encoder.startTuple()
-  encoder.write(item.destination)
-  encoder.write(item.amount)
-  encoder.finishTuple()
+  encoder.write:
+    ( (guarantee.targetChannelId, guarantee.destinations), )
 
 func encode*(encoder: var AbiEncoder, allocation: Allocation) =
-  encoder.startTuple()
-  encoder.write(seq[AllocationItem](allocation))
-  encoder.finishTuple()
+  encoder.write: (seq[AllocationItem](allocation),)
 
 func encode*(encoder: var AbiEncoder, assetOutcome: AssetOutcome) =
-  var content= AbiEncoder.init()
-  content.startTuple()
-  content.startTuple()
-  content.write(assetOutcome.kind)
+  var content: seq[byte]
   case assetOutcome.kind:
   of allocationType:
-    content.write(AbiEncoder.encode(assetOutcome.allocation))
+    content = AbiEncoder.encode:
+      ( (assetOutcome.kind, ABiEncoder.encode(assetOutcome.allocation)), )
   of guaranteeType:
-    content.write(AbiEncoder.encode(assetOutcome.guarantee))
-  content.finishTuple()
-  content.finishTuple()
-
-  encoder.startTuple()
-  encoder.write(assetOutcome.assetHolder)
-  encoder.write(content.finish())
-  encoder.finishTuple()
+    content = AbiEncoder.encode:
+      ( (assetOutcome.kind, AbiEncoder.encode(assetOutcome.guarantee)), )
+  encoder.write( (assetOutcome.assetHolder, content) )
 
 func encode*(encoder: var AbiEncoder, outcome: Outcome) =
-  encoder.startTuple()
-  encoder.write(seq[AssetOutcome](outcome))
-  encoder.finishTuple()
+  encoder.write: (seq[AssetOutcome](outcome),)
 
 func hashOutcome*(outcome: Outcome): array[32, byte] =
   keccak256.digest(AbiEncoder.encode(outcome)).data
diff --git a/nitro/protocol/state.nim b/nitro/protocol/state.nim
index bf431af..d584a0a 100644
--- a/nitro/protocol/state.nim
+++ b/nitro/protocol/state.nim
@@ -45,21 +45,17 @@ func variablePart*(state: State): VariablePart =
   )
 
 func hashAppPart*(state: State): array[32, byte] =
-  var encoder= AbiEncoder.init()
-  encoder.startTuple()
-  encoder.write(state.challengeDuration)
-  encoder.write(state.appDefinition)
-  encoder.write(state.appData)
-  encoder.finishTuple()
-  keccak256.digest(encoder.finish).data
+  let encoding = AbiEncoder.encode:
+    (state.challengeDuration, state.appDefinition, state.appData)
+  keccak256.digest(encoding).data
 
 func hashState*(state: State): array[32, byte] =
-  var encoder= AbiEncoder.init()
-  encoder.startTuple()
-  encoder.write(state.turnNum)
-  encoder.write(state.isFinal)
-  encoder.write(getChannelId(state.channel))
-  encoder.write(hashAppPart(state))
-  encoder.write(hashOutcome(state.outcome))
-  encoder.finishTuple()
-  keccak256.digest(encoder.finish).data
+  let encoding = AbiEncoder.encode:
+    (
+      state.turnNum,
+      state.isFinal,
+      getChannelId(state.channel),
+      hashAppPart(state),
+      hashOutcome(state.outcome)
+    )
+  keccak256.digest(encoding).data
diff --git a/tests/nitro/protocol/testChannel.nim b/tests/nitro/protocol/testChannel.nim
index ae7a402..84c9dd1 100644
--- a/tests/nitro/protocol/testChannel.nim
+++ b/tests/nitro/protocol/testChannel.nim
@@ -7,13 +7,8 @@ suite "channel definition":
   let channel = ChannelDefinition.example
 
   test "calculates channel id":
-    var encoder= AbiEncoder.init()
-    encoder.startTuple()
-    encoder.write(channel.chainId)
-    encoder.write(channel.participants)
-    encoder.write(channel.nonce)
-    encoder.finishTuple()
-    let encoded = encoder.finish()
+    let encoded = AbiEncoder.encode:
+      (channel.chainId, channel.participants, channel.nonce)
     let hashed = keccak256.digest(encoded).data
     check getChannelId(channel) == Destination(hashed)
 
diff --git a/tests/nitro/protocol/testOutcome.nim b/tests/nitro/protocol/testOutcome.nim
index 41e08d3..a89c78c 100644
--- a/tests/nitro/protocol/testOutcome.nim
+++ b/tests/nitro/protocol/testOutcome.nim
@@ -6,31 +6,20 @@ suite "outcome":
 
   test "encodes guarantees":
     let guarantee = Guarantee.example
-    var encoder= AbiEncoder.init()
-    encoder.startTuple()
-    encoder.startTuple()
-    encoder.write(guarantee.targetChannelId)
-    encoder.write(guarantee.destinations)
-    encoder.finishTuple()
-    encoder.finishTuple()
-    check AbiEncoder.encode(guarantee) == encoder.finish()
+    let expected = AbiEncoder.encode:
+      ((guarantee.targetChannelId, guarantee.destinations),)
+    check AbiEncoder.encode(guarantee) == expected
 
   test "encodes allocation items":
     let item = AllocationItem.example
-    var encoder= AbiEncoder.init()
-    encoder.startTuple()
-    encoder.write(item.destination)
-    encoder.write(item.amount)
-    encoder.finishTuple()
-    check AbiEncoder.encode(item) == encoder.finish()
+    let expected = AbiEncoder.encode: (item.destination, item.amount)
+    check AbiEncoder.encode(item) == expected
 
   test "encodes allocation":
     let allocation = Allocation.example
-    var encoder= AbiEncoder.init()
-    encoder.startTuple()
-    encoder.write(seq[AllocationItem](allocation))
-    encoder.finishTuple()
-    check AbiEncoder.encode(allocation) == encoder.finish()
+    let expected = AbiEncoder.encode:
+      (seq[AllocationItem](allocation),)
+    check AbiEncoder.encode(allocation) == expected
 
   test "encodes allocation outcome":
     let assetOutcome = AssetOutcome(
@@ -38,19 +27,11 @@ suite "outcome":
       assetHolder: EthAddress.example,
       allocation: Allocation.example
     )
-    var content= AbiEncoder.init()
-    content.startTuple()
-    content.startTuple()
-    content.write(allocationType)
-    content.write(AbiEncoder.encode(assetOutcome.allocation))
-    content.finishTuple()
-    content.finishTuple()
-    var encoder= AbiEncoder.init()
-    encoder.startTuple()
-    encoder.write(assetOutcome.assetHolder)
-    encoder.write(content.finish())
-    encoder.finishTuple()
-    check AbiEncoder.encode(assetOutcome) == encoder.finish()
+    let content = AbiEncoder.encode:
+      ((allocationType, AbiEncoder.encode(assetOutcome.allocation)),)
+    let expected = AbiEncoder.encode:
+      (assetOutcome.assetHolder, content)
+    check AbiEncoder.encode(assetOutcome) == expected
 
   test "encodes guarantee outcome":
     let assetOutcome = AssetOutcome(
@@ -58,27 +39,17 @@ suite "outcome":
       assetHolder: EthAddress.example,
       guarantee: Guarantee.example
     )
-    var content= AbiEncoder.init()
-    content.startTuple()
-    content.startTuple()
-    content.write(guaranteeType)
-    content.write(AbiEncoder.encode(assetOutcome.guarantee))
-    content.finishTuple()
-    content.finishTuple()
-    var encoder= AbiEncoder.init()
-    encoder.startTuple()
-    encoder.write(assetOutcome.assetHolder)
-    encoder.write(content.finish())
-    encoder.finishTuple()
-    check AbiEncoder.encode(assetOutcome) == encoder.finish()
+    let content = AbiEncoder.encode:
+      ((guaranteeType, AbiEncoder.encode(assetOutcome.guarantee)),)
+    let expected = AbiEncoder.encode:
+      (assetOutcome.assetHolder, content)
+    check AbiEncoder.encode(assetOutcome) == expected
 
   test "encodes outcomes":
     let outcome = Outcome.example()
-    var encoder= AbiEncoder.init()
-    encoder.startTuple()
-    encoder.write(seq[AssetOutcome](outcome))
-    encoder.finishTuple()
-    check AbiEncoder.encode(outcome) == encoder.finish()
+    let expected = AbiEncoder.encode:
+      (seq[AssetOutcome](outcome),)
+    check AbiEncoder.encode(outcome) == expected
 
   test "hashes outcomes":
     let outcome = Outcome.example
diff --git a/tests/nitro/protocol/testState.nim b/tests/nitro/protocol/testState.nim
index 3832ce5..b5ec3f8 100644
--- a/tests/nitro/protocol/testState.nim
+++ b/tests/nitro/protocol/testState.nim
@@ -23,26 +23,20 @@ suite "state":
     )
 
   test "hashes app part of state":
-    var encoder= AbiEncoder.init()
-    encoder.startTuple()
-    encoder.write(state.challengeDuration)
-    encoder.write(state.appDefinition)
-    encoder.write(state.appData)
-    encoder.finishTuple()
-    let encoded = encoder.finish()
+    let encoded = AbiEncoder.encode:
+      (state.challengeDuration, state.appDefinition, state.appData)
     let hashed = keccak256.digest(encoded).data
     check hashAppPart(state) == hashed
 
   test "hashes state":
-    var encoder= AbiEncoder.init()
-    encoder.startTuple()
-    encoder.write(state.turnNum)
-    encoder.write(state.isFinal)
-    encoder.write(getChannelId(state.channel))
-    encoder.write(hashAppPart(state))
-    encoder.write(hashOutcome(state.outcome))
-    encoder.finishTuple()
-    let encoded = encoder.finish()
+    let encoded = AbiEncoder.encode:
+      (
+        state.turnNum,
+        state.isFinal,
+        getChannelId(state.channel),
+        hashAppPart(state),
+        hashOutcome(state.outcome)
+      )
     let hashed = keccak256.digest(encoded).data
     check hashState(state) == hashed