feat(mempool): raise MaxUntrustedActorPendingMessages from 10 to 100

[beck-8]

Related Issues

None. The current value has been unchanged since the untrusted push path was introduced in 3c72461 (2020).

Proposed Changes

• Raise MaxUntrustedActorPendingMessages from 10 to 100 in chain/messagepool/messagepool.go.
• Update the corresponding comment on PushUntrusted.
• Add a CHANGELOG.md entry under ## 👌 Improvements.

Additional Info

The per-actor cap on the untrusted push path — used by lotus-gateway and therefore every public RPC relaying MpoolPush from external clients — has been 10 since this path was introduced in 2020.

That value is too tight for normal usage. A sender pushing at modest cadence can easily have more than 10 messages in flight when basefee spikes briefly or block inclusion stalls, after which every subsequent send is rejected with ErrTooManyPendingMessages. The failure surfaces as a hard error on the send path rather than backpressure.

Impact

• Cap raised 10x but still an order of magnitude below the trusted-path cap (MaxActorPendingMessages = 1000), preserving the asymmetry that protects gateway operators from external spam.
• maxNonceGap = 0 for untrusted messages is unchanged — pending messages must still form a contiguous nonce sequence from the on-chain nonce, so an attacker cannot park arbitrary future nonces.
• Worst-case additional per-actor memory: ~90 extra SignedMessage entries, negligible against the existing global pool bounds.
• No API or wire-format changes.

Checklist

Before you mark the PR ready for review, please make sure that:

• Commits have a clear commit message.
• PR title conforms with contribution conventions
• Update CHANGELOG.md or signal that this change does not need it per contribution conventions
• New features have usage guidelines and / or documentation updates in
  • Lotus Documentation
  • Discussion Tutorials
• Tests exist for new functionality or change in behavior (no test references the literal 10; behavior is unchanged apart from the constant)
• CI is green

[beck-8]

The problem I actually encountered was: I often encountered too many pending messages for actor when using glif rpc (run pdp node), regardless of whether it is a paid plan or not. This limit is too low.

[Copilot]

Pull request overview

This PR updates the mempool’s untrusted message push limits (used by lotus-gateway / public RPC paths) to reduce unnecessary ErrTooManyPendingMessages failures for normal senders when inclusion temporarily stalls.

Changes:

• Increase MaxUntrustedActorPendingMessages default from 10 to 100.
• Update the PushUntrusted comment to reflect the new cap.
• Pin the untrusted cap to 10 in relevant integration tests to keep the scenarios bounded and independent of the package default.
• Add an UNRELEASED changelog entry under 👌 Improvements.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated no comments.

File	Description
chain/messagepool/messagepool.go	Raises the default per-actor untrusted pending-message cap and updates the related comment.
itests/mempool_test.go	Pins MaxUntrustedActorPendingMessages to 10 for the test to keep expectations stable after the default changes.
itests/eth_transactions_test.go	Pins MaxUntrustedActorPendingMessages to 10 for the multi-transaction untrusted-path test scenario.
CHANGELOG.md	Documents the behavioral change under UNRELEASED improvements.

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