Arc mainnet day-0: eth_subscribe for bridge inflow + first-pool launch

Want the right tool for the job. On a new chain’s open day, capital often hits the bridge first, then first pools and first LP land. Chinese CT is already calling Arc mainnet around 9/16 with a bridge-first tape—paraphrased from the thread around TheMaran. This post teaches one recipe: hang bridge netflow + Factory new pairs / first LP on the same eth_subscribe pipe for day-0.

Robinhood already has a bridge-rotation post: Bridge rotation watch (RH-side flow / rotation windows). This piece is a different lane: new-chain day-0—bridge inflow spikes + first-pool launch on one board.

Use	Endpoint (runnable demo)
Public HTTPS	https://robinhood-mainnet-rpc.blockreq.com/v1/rpc/public
Public WSS	wss://robinhood-mainnet-rpc.blockreq.com/v1/rpc/public
Private	Trailing public → {API_KEY} (keys stay local)

Run the demo on Robinhood public WSS first—same recipe; when Arc public endpoints light up day-0, swap the host and port the watch. Free 3M Requests / 30 days · Public endpoints · eth_subscribe · Pricing.

1. Day-0 twin signals: bridge + launch

Tape feel	On-chain signal	Watch
Funds enter bridge	Deposit / Lock / Message-style log	in bucket + token; short-window netflow
Inflow spike	Same bridge: sum(in) − sum(out) steep vs baseline	Tag bridge inflow spike
First pool lands	Factory PairCreated (or kin)	token0 / token1 / pair
First LP	First Mint / add-liquidity Transfer cluster on that pair	Size + LP address

Day-0 = bridge netflow and new pair / first LP on one pipe. The RH bridge-rotation post leans rotation windows on a live chain; this one leans the open-hour “bridge first, then pools” tape.

2. Dual subscribe: bridge logs + Factory (eth_subscribe)

Keep two local tables: bridges[], factories[] (lowercase, deduped). One public WSS, two narrow log subs; bucket on each push.

Step A · Subscribe bridge (inflow)

{
  "jsonrpc": "2.0", "id": 1, "method": "eth_subscribe",
  "params": ["logs", {
    "address": "0xYourBridgeAddress",
    "topics": []
  }]
}

• Always pass bridge address; narrow Deposit / Withdraw topics[0] when you have ABI.
• Decode into in / out; net = sum(in) − sum(out); demo uses 5 / 15m windows.

Step B · Subscribe PairCreated (first pool)

{
  "jsonrpc": "2.0", "id": 2, "method": "eth_subscribe",
  "params": ["logs", {
    "address": "0xYourFactoryAddress",
    "topics": ["0x0d3648bd0f6ba80134a33ba9275ac585d9d315f0ad8355cddefde31afa28d0e9"]
  }]
}

• topics[0] = Uniswap V2-style PairCreated (confirm against Factory ABI).
• Decode token0 / token1 / pair → first-pool hit; add that pair to a hot table.

Step C · Subscribe Mint on the new pair (first LP)

{
  "jsonrpc": "2.0", "id": 3, "method": "eth_subscribe",
  "params": ["logs", {
    "address": "0xNewPairAddress",
    "topics": ["0x4c209b5fc8ad50758f13e2e1088ba56a560dff690a1c6fef26394f4c03821c4f"]
  }]
}

• Common V2 Mint topic0 shown above (confirm against pair ABI). First Mint cluster → first LP; remember adder + size.

3. Preview: Arc bridge + launch watch (StackBlitz)

Defaults to BlockReq Robinhood public WSS as the runnable pattern; paste bridge / Factory addresses, live-refresh inflow windows + first pool / first LP. When Arc endpoints light up, swap the WSS host—same logic ports over. Code lives in StackBlitz; article embeds the preview only:

Repo: blockreq/blog-demos → examples/arc-bridge-launch-watch. For keyed: swap trailing public for {API_KEY}.

4. Alert trio: inflow spike · first pool · first LP

1. Bridge inflow spike → net_5m vs 15m baseline ≥ multiple / absolute floor → push inflow spike.
2. First pool → Factory PairCreated → push first pool (token0/1).
3. First LP → first Mint / add-liquidity cluster on that pair → push first LP (size + adder).
4. Same-window compose → spike then first pool + first LP within T minutes → one day-0 card.

Tune thresholds yourself (demo often: 5m net ≥ 2× baseline; push on PairCreated; dedupe Mint by tx cluster). Tags = interpretation: JSON → board / webhook.

Disconnects: reconnect → re-subscribe; gap-fill with HTTPS eth_getLogs in block segments; replay the same in/out + PairCreated + Mint rules. POST → https://robinhood-mainnet-rpc.blockreq.com/v1/rpc/public (swap host when Arc endpoints light up).

5. Summary

1. Arc day-0 = bridge netflow + first pool / first LP on one pipe; bridge first, pools follow.
2. Recipe: bridge log buckets + Factory PairCreated + pair Mint → spike / first pool / first LP.
3. Runnable demo on Robinhood public WSS; Free 3M covers practice and short day-0 sessions; swap endpoint when Arc public lights up.
4. Series contrast: RH bridge rotation (live-chain rotation windows) · this new-chain day-0 bridge+launch post.

Next: pin bridge / factory tables as JSON → wire the trio to webhooks → persist backfill checkpoints; one host flip when Arc endpoints appear. Public endpoints · Plans & pricing.