[cdecker]

Problem

Since the VLS 1.0.0-rc.1 upgrade (6eed32f5), SIGN_PENALTY_TO_US goes through validate_justice_sweep -> validate_sweep -> validate_fee, which compares the sweep tx feerate against SimplePolicy::min_feerate_per_kw — 253 sat/kw (~1 sat/vB) from make_default_simple_policy.

In Greenlight those transactions are built by CLN (lightningd/onchaind), which derives the sweep feerate from its own backend-backed estimates and applies its own floors and worth-it checks before requesting the signature. During quiet-fee periods the estimate drops below 253 sat/kw and the signer hard-fails the signature, e.g. seen in production today:

policy failure: validate_justice_sweep: validate_sweep: validate_fee: feerate below minimum: 226 < 253

The justice sweep then stays unsigned until network feerates recover — the signer's floor contradicts CLN's fee policy instead of protecting against it.

Fix

Set policy.min_feerate_per_kw = 75 (~0.3 sat/vB) in the gl-client signer setup: low enough to never second-guess a CLN-built sweep, while still rejecting zero-fee or absurdly low transactions.

Notes

• Only affects signers built from gl-client (embedded client signer and the server-side runner); the check itself lives in VLS and is untouched.
• The 44bfc34 (fee budgets) branch work keeps the sweep ceiling at 150k and never touches this minimum, so no conflict with it.

Test

cargo check -p gl-client passes. End-to-end: attach a local signer to a node with a pending justice sweep at low feerate and observe the sweep tx now gets signed and broadcast instead of a FailedPrecondition.