fix: don't reject a mining interval of 0, which disables interval mining

[Kropiunig]

Problem

The EDR network config validation rejects any mining.interval below 1000 ms
unless allowBlocksWithSameTimestamp: true is also set. That check exists to
stop block timestamps from running ahead of clock time (#6012).

A scalar interval: 0 does not schedule blocks at all, so it can't cause that
divergence. It is how interval mining is turned off — and it is the value the
config resolution already defaults to. Writing it explicitly makes Hardhat
refuse to load the config:

// hardhat.config.ts
export default {
  networks: {
    dev: {
      type: "edr-simulated",
      mining: {
        auto: false,
        interval: 0, // turn off automatic mining, mine manually with evm_mine
      },
    },
  },
};

$ npx hardhat test
Error in networks.dev.mining.interval: mining.interval is set to less than
1000 ms. To avoid the block timestamp diverging from clock time, please set
allowBlocksWithSameTimestamp: true on the network config

The suggested workaround (allowBlocksWithSameTimestamp: true) changes
unrelated behaviour, and the message describes a risk that cannot occur when no
blocks are mined on a timer.

Root cause

refineEdrNetworkUserConfig in
packages/hardhat/src/internal/builtin-plugins/network-manager/type-validation.ts
runs the minimum-interval check for every numeric interval, including 0:

const interval = network.mining?.interval;
if (typeof interval === "number" || Array.isArray(interval)) {
  const minInterval =
    typeof interval === "number" ? interval : Math.min(...interval);
  if (minInterval < 1000 && network.allowBlocksWithSameTimestamp !== true) {

But 0 is the "interval mining disabled" sentinel elsewhere in the same
plugin:

• hardhatMiningIntervalToEdrMiningInterval
  (edr/utils/convert-to-edr.ts) maps a scalar 0 to undefined with the
  comment // Is interval mining disabled?.
• resolveMiningConfig (config-resolution.ts) resolves the default to
  interval: 0, and the existing default-config test asserts
  mining === { auto: true, interval: 0, mempool: { order: "priority" } }.

So the validation rejects a value the resolver produces by default.

Fix

Skip the check only for a scalar 0. An interval range always enables
interval mining, so [0, 5000] is still an error.

Tests

Added to
packages/hardhat/test/internal/builtin-plugins/network-manager/hook-handlers/config.ts:

• interval: 0 with allowBlocksWithSameTimestamp: false → no validation errors.
• mining: { auto: false, interval: 0 } → no validation errors.
• interval: [0, 5000] → still errors (ranges are unaffected).

Both new assertions fail on main (1 validation error where 0 is expected) and
pass with this change.

[changeset-bot]

🦋 Changeset detected

Latest commit: 2ccd059

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
hardhat	Patch

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[Copilot]

Pull request overview

Fixes EDR simulated-network config validation so that mining.interval: 0 (the sentinel that disables interval mining and is also the resolved default) no longer triggers the “< 1000 ms” timestamp-divergence validation error.

Changes:

• Updated EDR network config refinement to skip the minimum-interval check for scalar interval === 0 while keeping interval-range validation unchanged.
• Added regression tests covering interval: 0 (accepted) and [0, 5000] (still rejected when allowBlocksWithSameTimestamp is false).
• Added a changeset to release the fix as a patch.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
packages/hardhat/src/internal/builtin-plugins/network-manager/type-validation.ts	Adjusts interval validation to treat scalar 0 as “interval mining disabled,” skipping the < 1000 ms guard.
packages/hardhat/test/internal/builtin-plugins/network-manager/hook-handlers/config.ts	Adds test coverage for interval: 0 acceptance and preserves errors for interval ranges with a minimum below 1000.
.changeset/edr-mining-interval-zero.md	Documents the patch release for the validation behavior change.