fukuii-pos-node-health

name	fukuii-pos-node-health
description	Produce a PoS-specific health verdict for an ETH/Sepolia Fukuii node — the CL↔EL Engine API liveness check, EL sync state, CL attestation participation (if validating), post-Cancun blob gossip peer count, and Engine API latency. Use when checking an ETH/Sepolia node's consensus-side health, after attaching a CL, when attestations are missed, or when blob sidecars seem to be dropped. ETH/Sepolia only — for the general/ETC health verdict use fukuii-node-health-check; for Engine API faults use fukuii-engine-api-debug.
disable-model-invocation	true
user-invokable	true

Fukuii PoS node health — ETH/Sepolia

Read ../CONVENTIONS.md first. This skill is read-only (🟢). It covers the PoS/consensus-side dimensions specific to ETH/Sepolia. For the general verdict (client version, sync, EL peer count, log scan, disk), run fukuii-node-health-check first — this skill adds the four checks below, it does not repeat them. ETC/Mordor operators: use fukuii-node-health-check only.

When to use

• Routine health of an ETH/Sepolia EL paired with a CL.
• After attaching/replacing a CL, or when attestations are being missed.
• When blob sidecars appear to be dropped (post-Cancun).

Checks (all 🟢)

1. CL↔EL Engine API liveness

   curl -s -o /dev/null -w "%{http_code}" http://localhost:8551/
   

   401 = live and correctly requiring JWT auth (expected, healthy). A bare curl carries no JWT, so 401 is the right answer. 000 / connection-refused = Engine API not bound → EL down, wrong port, or engine-api.enabled=false (→ fukuii-engine-api-setup).

2. EL sync status

   cast rpc eth_syncing --rpc-url http://localhost:8545      # false = synced
   

   false = at the tip. An object = still catching up; confirm eth_blockNumber is advancing. If stuck, identify the sync phase via fukuii-sepolia-sync.

3. CL attestation participation (validators only) Attestation/proposal effectiveness lives on the CL, not the EL — the EL exposes none of it. Check the CL's metrics/REST endpoint:

   • Beacon node: curl http://localhost:5052/eth/v1/node/syncing (Lighthouse REST shape; port/path vary by client).
   • Validator/CL metrics (Prometheus) for attestation hit-rate and missed duties. A healthy validator attests every epoch. Missed duties with a SYNCING EL → the EL isn't ready (→ fukuii-engine-api-debug Case 4).

4. Blob gossip peer count (post-Cancun) After Cancun, blob sidecars (EIP-4844) propagate on a separate gossip network managed by the CL — they are not visible in the EL's net_peerCount. A low CL peer count → missed blob sidecars → the EL receives payloads it can't fully validate. Check both:

   cast rpc net_peerCount --rpc-url http://localhost:8545    # EL peers (hex)
   

   and the CL's peer count (e.g. curl http://localhost:5052/eth/v1/node/peer_count). Low CL peers is the usual root cause of "blob sidecar not found" — fix on the CL side.

5. Engine API latency Target < 2s for engine_newPayloadV* and engine_forkchoiceUpdated*. Sample the round-trip from Fukuii's Engine API logs (request → response timestamps). Sustained high latency → the CL marks the EL slow and may withhold timely head updates; on a validator this costs attestation effectiveness. High latency usually means the EL host is I/O- or CPU-bound (datadir on HDD, swapping, or under load) — check uptime and datadir disk type, and see fukuii-engine-api-debug Case 2.

Decision guide

Check	Healthy	Degraded → action
:8551 curl	401	refused → fukuii-engine-api-setup
eth_syncing	false	object & flat → fukuii-sepolia-sync
CL attestations	every epoch	missed + EL SYNCING → fukuii-engine-api-debug C4
Blob/CL peers	CL peers healthy	low CL peers → fix CL peering
Engine API latency	< 2s	sustained > 2s → check host I/O/load (C2)

Deep reference

• fukuii-node-health-check — general/ETC health verdict (run first).
• fukuii-cl-setup, fukuii-engine-api-setup, fukuii-engine-api-debug, fukuii-sepolia-sync.
• ops/grafana/Sepolia Consensus/fukuii-sepolia-staking.json — staking dashboard.

Output

CONVENTIONS §4 block. Verdict (HEALTHY / DEGRADED / ACTION REQUIRED). Evidence = the :8551 status code, eth_syncing, EL and CL peer counts, attestation state, and observed Engine API latency. Actions taken: none (read-only).