fix: pre-warm Tempo precompile accounts in fork mode to prevent invariant hang #259
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…iant hang In fork mode against a Tempo RPC, precompile addresses (0xDEc0..., 0x20C0...) are Rust-native precompiles with no real EVM bytecode. The RPC returns empty code or sentinel bytecode for these addresses, causing the fork backend to repeatedly fetch them via RPC on every access. During invariant fuzzing, this creates a pathological RPC storm that effectively hangs the test runner. This fix adds warm_tempo_precompile_accounts() which pre-populates sentinel bytecode into the local fork cache for all known precompile and TIP20 token addresses, gated to Tempo chain IDs only. Closes #251 Amp-Thread-ID: https://ampcode.com/threads/T-019c4802-1267-7277-8001-796209967317 Co-authored-by: Amp <amp@ampcode.com>
gakonst
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0xrusowsky,
DaniPopes,
grandizzy,
mattsse,
onbjerg and
zerosnacks
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grandizzy
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Feb 10, 2026
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grandizzy
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nice! let's move these in a common place and reuse across all places
tempo-foundry/crates/anvil/tests/it/tempo.rs
Lines 35 to 38 in 88ef3cf
Move PATH_USD, ALPHA_USD, BETA_USD, THETA_USD constants to foundry-evm-core/src/tempo.rs as the shared source of truth, and reuse them in anvil backend, anvil tests, and the fork warm function. Also fixes rustfmt import ordering. Amp-Thread-ID: https://ampcode.com/threads/T-019c4802-1267-7277-8001-796209967317 Co-authored-by: Amp <amp@ampcode.com>
Contributor
Good call, fixed in 65bff21 |
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grandizzy
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Feb 10, 2026
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Summary
Fixes invariant test runner hanging indefinitely when using
--fork-urlagainst a Tempo RPC.Closes #251
Motivation
Tempo precompile addresses (
0xDEc0...,0x20C0...) are Rust-native precompiles with no real EVM bytecode on-chain. The RPC returns empty code (0x) or sentinel bytecode (0xef) for these addresses.In fork mode, the
SharedBackendsends RPC requests for every uncached account/storage access usingtokio::task::block_in_place()+recv(). During invariant fuzzing — which involves many rapid executor clone + snapshot/revert cycles — the repeated cache misses for precompile addresses create a pathological RPC storm that effectively hangs the test runner.Simple fork tests work because they only touch precompile addresses a few times and the responses are fast enough. Invariant fuzzing amplifies the problem by orders of magnitude.
Changes
crates/evm/evm/src/tempo.rs: addwarm_tempo_precompile_accounts()which pre-populates sentinel bytecode (0xef) into the local fork cache for all known precompile (0xDEc0...) and TIP20 token (0x20C0...) addresses. Gated to known Tempo chain IDs only.crates/forge/src/runner.rs: call the warm function in fork mode (else branch of the existing precompile init guard).Testing
cargo check -p foundry-evm -p forge✓cargo clippy -p foundry-evm -p forge -- -D warnings✓eth_getCodereturns0xfor StablecoinDEX,0xeffor TIP20 tokensThread: https://tempoxyz.slack.com/archives/C0A87C21805/p1770734618130419