Record miner burn as TAO outflow in coinbase

[unconst]

Summary

• When the coinbase incentive loop encounters an SN-owner-associated hotkey, it skips the payout and recycles or burns the incentive. The corresponding TAO leaving the pool was not being recorded.
• This PR converts the skipped alpha incentive to its TAO equivalent at the current spot price (no slippage, since no swap occurs) and calls record_tao_outflow(netuid, tao_equivalent) so the subnet's TAO flow accounting stays in sync with what actually leaves circulation on this path.

Code path touched: pallets/subtensor/src/coinbase/run_coinbase.rs, inside the owner_hotkeys.contains(&hotkey) branch of the incentives loop, just before the RecycleOrBurn match.

Test plan

• cargo check -p pallet-subtensor — clean
• Existing coinbase tests still pass: cargo test -p pallet-subtensor --lib tests::coinbase
• Spot-check that SubnetTaoFlow decreases by the expected TAO-equivalent on a subnet where an owner hotkey appears in the incentives list

Made with Cursor

[github-actions]

AI review — see the sticky summary comment for the verdict and the inline comments below for specific findings.

[github-actions]

[MEDIUM] Clamp the synthetic outflow before recording signed flow

record_tao_outflow stores into SubnetTaoFlow<i64> by casting u64::from(tao) as i64. This new path derives tao_equivalent from spot price times incentive and can saturate above i64::MAX; once that happens the cast becomes negative, and saturating_sub(negative) records an inflow instead of an outflow. A subnet owner hotkey can trigger this branch, so this can distort flow-based emission accounting. Bound the synthetic outflow to the signed accumulator range before recording it, or change the recorder to use a checked/clamped conversion.

Suggested change

	let tao_equivalent: TaoBalance = current_price
	.saturating_mul(asfloat!(incentive))
	.saturating_to_num::<u64>()
	.into();
	Self::record_tao_outflow(netuid, tao_equivalent);
	let tao_equivalent: TaoBalance = current_price
	.saturating_mul(asfloat!(incentive))
	.saturating_to_num::<u64>()
	.min(i64::MAX as u64)
	.into();

[github-actions]

🛡️ AI Review — Skeptic (security review)

VERDICT: VULNERABLE

BASELINE scrutiny: established write-permission contributor, long prior subtensor history, no Gittensor allowlist hit; branch unconst/miner-burn-tao-outflow -> devnet-ready.

Findings

Sev	File	Finding
MEDIUM	pallets/subtensor/src/coinbase/run_coinbase.rs:630	Clamp the synthetic outflow before recording signed flow	inline

Conclusion

The PR is small and matches the stated coinbase-accounting path, but it introduces a new synthetic TaoBalance outflow that can exceed the signed SubnetTaoFlow accumulator’s range. Clamp or otherwise bound the value before passing it to record_tao_outflow.

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# 🔍 AI Review — Auditor (domain review) has not yet run on this PR.

[github-actions]

🔄 AI review updated — Skeptic: VULNERABLE