fix(simulator): rewrite wss/ws RPC URL to https/http for fork backend

[0xfandom]

Problem

The revm-backed fork backend issues one-shot eth_getStorageAt / eth_getBalance requests via AlloyDB's HTTP transport. ETH_RPC_URL, however, is shared with the streaming subscription path (newHeads, logs, pending tx) which requires a wss:// / ws:// scheme for the persistent connection.

Without normalisation, ProviderBuilder::new().connect_http(parsed) on a wss URL fails every detected cycle with:

ERROR aether_simulator: RPC EVM transact error error=database error: Transport error: builder error for url (wss://eth-mainnet.g.alchemy.com/v2/<key>)

Floods the log on every block (10-50 errors/sec when detection is active). Mempool tracking (analytical predictors) is unaffected, but the regular block-by-block arb validation path is silently broken.

This surfaced after ETH_RPC_URL was flipped from https to wss to engage Alchemy alchemy_pendingTransactions + newHeads over WebSocket for the PR #118 mempool work. Pre-existing bug — was lurking the whole time, only visible once the env var changed scheme.

Fix

Add normalize_to_http_scheme(url: &str) -> String which rewrites wss:// -> https:// and ws:// -> http:// literally, leaving host / path / query intact. Apply at the boundary between config.rpc_url and the ProviderBuilder::connect_http call in AetherEngine::new.

let http_url = normalize_to_http_scheme(url_str);
let parsed: url::Url = http_url.parse()?;
let provider = ProviderBuilder::new().connect_http(parsed);

Why HTTP, not WS-backed fork

revm itself is transport-agnostic — it consumes a Database trait and AlloyDB wraps any alloy Provider. WS-backed fork works, but isn't preferred:

Aspect	HTTP fork	WS-backed fork
Concurrent reads	Native parallel	Multiplexed through one socket
Per-sim latency (50-200 slot fetches)	~50ms	~150-300ms
Rate limits	Separate from subscription budget	Shares budget with streaming
Connection state	Stateless, retries cheap	Persistent, needs reconnect plumbing
revm convention	Canonical (Foundry, Anvil, every tutorial)	Atypical
Anvil compatibility	Native	Some versions wonky

Scheme rewrite gives operators a single ETH_RPC_URL env var while routing each consumer to the transport it actually wants.

Why a literal rewrite

Alchemy, Infura, and QuickNode all expose both transports on the same hostname + path differing only in scheme:

• wss://eth-mainnet.g.alchemy.com/v2/<key>
• https://eth-mainnet.g.alchemy.com/v2/<key>

No new env var, no config-file changes, no operator coordination required.

Unknown schemes

IPC paths (ipc:///tmp/reth.ipc), file URLs, anything not ws(s) — pass through unchanged. Downstream parser surfaces a clear error rather than silently miscast.

Side-effect: clippy fix

Develop's crates/grpc-server/src/metrics.rs doc-list continuation lines under sim_evm_fallback_total were indented to 24 spaces. Rust 1.94's clippy::doc_overindented_list_items lint rejects them under -D warnings. Dedented to 4 spaces — required to keep cargo clippy --workspace -- -D warnings green for the new tests.

Tests

6 unit tests covering all scheme cases:

• wss:// -> https://
• ws:// -> http://
• https:// unchanged
• http:// unchanged
• ipc:// (unknown scheme) unchanged
• Query string + path preservation

488 workspace tests pass. cargo clippy --workspace -- -D warnings clean.

Impact

• Unblocks main-detection EVM sim when operator sets ETH_RPC_URL=wss://...
• No behaviour change when ETH_RPC_URL is already https://...
• No env var changes, no config-file changes
• Mempool tracking pipeline unaffected (uses analytical predictors, never touched the fork)

Verification

Before (capture log on PR #118 branch):

ERROR aether_simulator: RPC EVM transact error error=database error: Transport error: builder error for url (wss://...)

... repeated 10-50 times/sec.

After (with this fix on ETH_RPC_URL=wss://...):

INFO aether_rust::engine: RPC provider created for fork simulation original=wss://eth-mainnet.g.alchemy.com/v2/<key> fork_url=https://eth-mainnet.g.alchemy.com/v2/<key>

No Transport error lines.

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Project	Deployment	Actions	Updated (UTC)
aether	Ready	Preview, Comment	May 11, 2026 11:44am
aether-63xv	Ready	Preview, Comment	May 11, 2026 11:44am