fix(e2e): resolve flaky proposer-not-found in equivocation_offenses duplicate_proposal test

[AztecBot]

Problem

multi-node/slashing/duplicate_proposal › slashes validator who sends duplicate proposals (yarn-project/end-to-end/src/multi-node/slashing/equivocation_offenses.test.ts) flaked in CI on the unrelated PR #24556 with:

Target proposer 0x90f79bf6eb2c4f870365e785982e1f101e93b906 not found in any slot after 20 epoch attempts

Evidence: http://ci.aztec-labs.com/eb0b4e658e28440c (the sibling duplicate_attestation case in the same file passed in the same run).

Root cause

Pure statistics — no logic bug. advanceToEpochBeforeProposer (yarn-project/end-to-end/src/multi-node/slashing/setup.ts on this branch) scans upcoming epochs for one where the target validator is the proposer, giving up after maxAttempts = 20 epochs. The test calls it with the default.

This suite uses a 2-slot epoch with warmupSlots = 1, so each epoch attempt inspects exactly one candidate slot. The proposer for a slot is keccak256(abi.encode(epoch, slot, seed)) % committeeSize, and with the suite's 4-member committee (COMMITTEE_SIZE = NUM_VALIDATORS = 4 in setup.ts) each attempt is an independent 1/4 draw. Miss probability over 20 attempts: (3/4)^20 ≈ 0.32%, i.e. roughly 1 in 315 runs — matching the observed occasional flake.

Fix

Raise the default maxAttempts from 20 to 50, bounding the miss probability at (3/4)^50 ≈ 5.7e-7 (~1 in 1.8M). Each attempt is only a committee query plus an anvil timestamp warp, so the expected attempt count stays ~4 and the extra headroom costs essentially nothing. The raised default also covers this helper's other callers with the same exposure (broadcasted_invalid_block_proposal_slash, broadcasted_invalid_checkpoint_proposal_slash), none of which override maxAttempts.

Relationship to PR #24548

This is the same failure mode fixed by #24548 for the duplicate_attestation flake, but #24548 does not cover this call site: its patch touches yarn-project/end-to-end/src/e2e_p2p/shared.ts, a file that does not exist on merge-train/spartan-v5 (on this branch the helper lives in multi-node/slashing/setup.ts, and there is no e2e_p2p/ directory). #24548's head branch was cut from a next-layout tree while targeting merge-train/spartan-v5, which is why GitHub reports it as dirty with ~4k changed files — it needs a rebase onto the branch it targets, at which point its fix would land in this same file. This PR applies the fix directly to the merge-train/spartan-v5 copy of the helper.

No tracked issue exists for this flake.

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Created by claudebox · group: slackbot

[AztecBot]

Flakey Tests

🤖 says: This CI run detected 1 tests that failed, but were tolerated due to a .test_patterns.yml entry.

\033FLAKED\033 (8;;http://ci.aztec-labs.com/09c2c9cfd6f765ba�09c2c9cfd6f765ba8;;�):  yarn-project/end-to-end/scripts/run_test.sh simple src/multi-node/block-production/multi_validator_node.parallel.test.ts "should attest ONLY with the correct validator keys" (58s) (code: 0) group:e2e-p2p-epoch-flakes