Only 8 participants are possible consistently

CHANGELOG.md

@@ -25,7 +25,7 @@ changes.
 
 - **BREAKING** Rewrite of the commit script in aiken:
   - This makes `abort` and `collectCom` transactions more efficient and results
-    in a new maximum number of head participants being `9`.
+    in a new maximum number of head participants being `8`.
   - Changes script hashes in `hydra-plutus`
 
 ## [0.19.0] - 2024-09-13

hydra-node/src/Hydra/Chain.hs

@@ -42,11 +42,12 @@ import Test.QuickCheck.Instances.Time ()
 maxMainnetLovelace :: Coin
 maxMainnetLovelace = Coin 100_000_000
 
--- | Hardcoded limit for maximum number of parties in a head protocol
--- The value is obtained from calculating the costs of running the scripts
--- and on-chan validators (see 'computeCollectComCost' 'computeAbortCost')
+-- | Hardcoded limit for maximum number of parties in a head protocol The value
+-- is obtained from calculating the costs of running the scripts and on-chan
+-- validators (see 'computeCollectComCost' 'computeAbortCost'). A too high
+-- enough number would be detected by property and acceptance tests.
 maximumNumberOfParties :: Int
-maximumNumberOfParties = 9
+maximumNumberOfParties = 8
 
 -- | Data type used to post transactions on chain. It holds everything to
 -- construct corresponding Head protocol transactions.

hydra-node/test/Hydra/Chain/Direct/StateSpec.hs

@@ -488,8 +488,8 @@ prop_splitUTxO utxo =
 
 prop_canCloseFanoutEveryCollect :: Property
 prop_canCloseFanoutEveryCollect = monadicST $ do
-  let maxParties = 10
-  ctx@HydraContext{ctxContestationPeriod} <- pickBlind $ genHydraContext maxParties
+  let moreThanSupported = maximumNumberOfParties * 2
+  ctx@HydraContext{ctxContestationPeriod} <- pickBlind $ genHydraContext moreThanSupported
   cctx <- pickBlind $ pickChainContext ctx
   -- Init
   txInit <- pickBlind $ genInitTx ctx