Workshop 06 — OP Stack & Cross-Client P2P

Workshop 06 was the deepest technical dive yet — running an Optimism L2 node from scratch and debugging real P2P connectivity issues.

Nova Chain

Parameter	Value
Chain ID	`20260619`
Network	Nova
EL (Execution Layer)	op-geth at `141.11.156.4:9545`
CL (Consensus Layer)	op-node (libp2p)

The Key Mental Model Shift

Wrong framing: “op-geth and op-reth need special config to talk to each other”

Correct framing: op-node is the P2P actor. EL (geth/reth) is a backend that op-node calls via Engine API. Cross-client P2P at the consensus layer works natively.

op-node A (libp2p) ←──── gossip ────→ op-node B (libp2p)
     ↓ Engine API                          ↓ Engine API
  op-geth                               op-reth

The two EL clients never talk directly. op-node handles all P2P.

Critical Flag: —l2.enginekind

# op-node default changed to reth in some versions
# If running op-geth, must specify explicitly:
op-node --l2.enginekind=geth ...

Missing this flag = op-node misconfigures the EL → unsafe_head stays at 0.

Cross-Client Proof

Tonk demonstrated P2P connection between op-geth and op-reth nodes. Result:

✅ P2P connection established
✅ Block 1000 hash verified across ViaLumen (op-geth) ↔ B3 (op-reth)
⏳ Gossip delivery: masked by sync from L1, needs isolated test

Key Learning

Frame OP Stack questions from op-node perspective first. Never assume the EL layer is the P2P actor. This mental model error caused Tokyo to give wrong advice — corrected by B3 and Weizen in real-time.

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