Runtime 445 (release v445)

The Bittensor mainnet runtime upgraded to spec version 445. Unlike the single-feature explainers elsewhere in this section, v445 is a bundled release: it reworks transaction-fee handling, restores miner-burn emission scaling, expands the EVM precompiles, and adds Ledger-style signatures for limit orders, alongside a set of storage-hygiene and proxy/multisig fixes.

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Live on mainnet (spec 445)

Confirmed on-chain: runtime version 445 activated at block 8,831,003 (2026-08-12 21:06 UTC on Finney), read from the Taostats runtime version index. Mainnet went straight from 443 to 445 — spec 444 was never a live mainnet runtime.

The short version

• Transaction fees are recycled, not paid to block authors. v445 reverts the earlier "reward the block author" behaviour: the fee is removed from issuance (recycled) instead of being handed to whoever built the block. Alpha-denominated fees are sold and the resulting TAO is recycled the same way.
• Miner-burn emission scaling is back. The (1 − miner_burned) discount on a subnet's emission share — removed earlier — was restored.
• The EVM precompile surface grew. New readers/getters, a root-claim precompile plus getters for unclaimed value, and runtime-constant exposure. A new rule bars root-privileged calls from being implemented in precompiles.
• Limit orders accept Ledger signatures. The limit-orders pallet now validates Ledger-style signatures alongside standard formats, and rejects invalid signatures during transaction validation.

Transaction fees: recycled, not burned, not paid to authors

This is the highest-impact user-facing change, and the wording matters.

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"Burn" is the wrong word here — it's a recycle

v445 removes the transaction fee from pallet_subtensor::TotalIssuance (TransactionFeeHandler::on_nonzero_unbalanced does TotalIssuance.saturating_sub(amount)). On Bittensor, subtracting from TotalIssuance is recycling — the TAO is removed from circulation now and re-enters the emission pool later, pushing the halving further out. It is not a permanent burn; nothing is destroyed. See the glossary entry on burn vs recycle.

What actually changed:

• Before: an earlier runtime routed transaction fees to the block author (block builder).
• v445: that is reverted. The fee is recycled — the block author receives nothing. The pallet's own test, tao_transaction_fees_are_recycled, asserts the block-builder balance is unchanged and that total issuance drops by exactly the fee charged.

Alpha-denominated fees follow the same fate by a different path: the pallet sells the alpha for TAO directly from the subnet account and recycles that TAO (recycle_tao), in a single storage transaction so a failed recycle rolls back the alpha withdrawal.

What this means: any model that assumed transaction fees accrued to validators/block authors as income is now wrong. Fee revenue does not flow to a participant — it leaves circulation and defers the halving, exactly like registration recycle.

Emissions: miner-burn scaling restored

v445 restores the miner-burn emission scaling in subnet emission shares (PR #3071) after it had been removed. Net effect: the prior behaviour is back — a subnet's demand share is again discounted by (1 − miner_burned) before it competes for emission.

This is the same first-stage filter described on the emission gate page: a subnet that burns 100% of its miner emission is zeroed out before the gate even sees it. With the scaling restored, any emission/APY estimate that ignores miner burn will again misplace which subnets actually earn.

See The emission gate and Price-based emission shares for how this discount feeds into the full emission calculation.

EVM precompiles: expanded and hardened

The precompile layer (precompiles/src) saw a large expansion:

• New readers and getters across existing precompiles that were missing them.
• A root-claim precompile, plus getters that expose unclaimed value, so EVM contracts can read and act on root-claim state.
• Runtime-constant exposure to the EVM, and no-std import fixes.
• A new invariant: root-privileged calls must not be implemented in precompiles. This is a security boundary, not a feature — it keeps root authority out of the EVM call surface.

The EVM interface artifacts were regenerated to match. See EVM contracts for how the precompiles fit the wider EVM story.

Limit orders: Ledger signatures

The limit-orders pallet now supports Ledger-style signatures alongside the standard signature formats. Ledger produces human-friendly signatures and signs a hash of the payload when it exceeds 256 bytes; v445 validates these correctly. Invalid signatures are now rejected during transaction validation rather than slipping through, and new test vectors cover the added formats.

Lower-impact fixes

Bundled in the release, less likely to be user-visible but worth noting for anyone indexing chain state:

• Commitments / storage hygiene — prevalidate commitment failures (#3040); purge neuron commitments when trimming UIDs and on deregistration (#3062); a storage-bloat reduction migration (#3061, #3076). Voting-power state is cleared on subnet dissolution, and TotalVotingPower was added to SDK metadata.
• Proxy / multisig — preserve intent safety and wrapper order through multisig dispatch, and propagate/refund inner post-dispatch weight for proxy calls (#3063).
• SDK / generated docs — refreshed Python SDK metadata, generated transaction links, error pages, and query docs for the new spec.

Source provenance

• Release: RaoFoundation/subtensor v445. The release body itself is deployment/multisig boilerplate; the changes above are reconstructed from the v443...v445 commit range and merged PRs, then verified against source at the v445 tag.
• On-chain confirmation: runtime version 445 at block 8,831,003 (2026-08-12 21:06 UTC), Finney, via the Taostats runtime-version index.
• Transaction fees (verified at v445): pallets/transaction-fee/src/lib.rs — TransactionFeeHandler::on_nonzero_unbalanced subtracts the fee from pallet_subtensor::TotalIssuance (recycle); the alpha path calls recycle_tao. Confirmed by the pallet test tao_transaction_fees_are_recycled (pallets/transaction-fee/src/tests/recycling.rs), which asserts the block author is not paid.
• Emissions: miner-burn scaling restored via PR #3071.

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The v445 release train lives on the RaoFoundation/subtensor repository (the former opentensor/subtensor, now redirected). PR numbers reference that repository.

See also: Recycling ·
Burning ·
The emission gate ·
EVM contracts