Bittensor Conviction System v2

Technical Explainer — Based on subtensor PRs #2658 and #2687

Last updated: 2026-05-27 (post PR #2696 60-day rates + pending PR #2695 no-default-auto-lock).

Mainnet vs devnet-ready right now

Mainnet deploy PR #2643 is open but blocked on the breaking-change review gate. None of the v2 behavior is live on mainnet yet.

What changed in this update

Three PRs reshaped conviction v2 between 2026-05-25 and 2026-05-27, all landing on devnet-ready:

• PR #2687 "Conviction updates" — merged 2026-05-25. Decaying is now the default lock mode, perpetual is opt-in via set_perpetual_lock(true). Anyone locking to the subnet owner's hotkey gets immediate conviction. One ConvictionModel struct with 4 aggregates. New RPC get_coldkey_lock(coldkey, netuid) -> Option<LockState>. Deprecated conviction maps removed. Testnet state wiped by migrate_reset_tnet_conviction_locks.
• PR #2696 "60 day unlock and maturity rate" — merged 2026-05-26 (commit cee0eda). DefaultUnlockRate and DefaultMaturityRate both changed from 311_622 (~30-day half-life) to 648_000 blocks (~60-day half-life). spec_version 408 → 409.
• PR #2695 "No default auto-lock" — open, mergeable but blocked on review approvals. DefaultOwnerCutAutoLockEnabled flips from true to false. spec_version 409 → 410. Subnets must opt in via sudo_set_owner_cut_auto_lock_enabled(netuid, true) once this ships.

The rest of this document reflects the post-#2696 / pending-#2695 picture (defaults: 60-day half-life, decaying mode, owner-cut auto-lock OFF by default).

1. What Is Conviction?

Conviction is Bittensor's governance mechanism that ties voting power to long-term commitment. When you lock alpha tokens to a subnet, you earn conviction — a measure of your stake's weight in governance decisions and subnet ownership.

Conviction exists to:

• Reward long-term alignment over short-term speculation
• Provide subnet governance stability
• Enable subnet ownership transitions through the "subnet king" mechanism
• Create skin-in-the-game for validators and subnet owners

Version 2 fundamentally redesigned the system: locks are now decaying by default (opt-in to perpetual via set_perpetual_lock(true)), anyone locking to the subnet owner's hotkey receives instant conviction, and the unlock queue was eliminated in favor of exponential decay.

2. How Locking Works

To earn conviction, you lock alpha tokens using the lock_stake(hotkey, netuid, amount) extrinsic:

• One lock per coldkey per subnet — You can only have a single active lock targeting one hotkey on each subnet.
• Lock to a hotkey — Your locked alpha is associated with a specific hotkey on that subnet. This is typically the subnet owner's hotkey, or the hotkey of someone building conviction to challenge for subnet ownership.
• Top-ups must match — Additional locks to the same subnet must target the same hotkey; you can't split locks across multiple hotkeys.
• Decaying by default — New locks decay automatically. locked_mass shrinks exponentially over time, and the difference between original lock and current mass can be unstaked.
• Optional perpetual — Call set_perpetual_lock(netuid, true) to freeze locked_mass and let conviction grow toward 100%.

3. Lock Types and Storage Buckets

Conviction v2 uses one individual lock state per locking coldkey plus four aggregate buckets based on two dimensions: who you lock TO (owner hotkey vs non-owner hotkey) and lock mode (perpetual vs decaying).

The Four Aggregate Buckets

The individual lock state (per coldkey, per subnet) is rolled forward into one of these 4 aggregates depending on the lock target and mode. The ConvictionModel struct in staking/lock.rs maintains all 5 states (1 individual + 4 aggregates) and updates them atomically on every operation.

Key rule: Locking to the subnet owner's hotkey gives instant conviction

Anyone — not just the subnet owner — who locks alpha to the subnet owner's hotkey receives instant conviction. This applies regardless of whether the lock is perpetual or decaying. The conviction equals locked_mass immediately with no growth period.

Locking to any other hotkey follows the standard maturity curve (1-month half-life under the new defaults, ~95% conviction at ~4.3 months).

Decaying Locks (Default)

When you call lock_stake without first opting into perpetual mode, your lock is decaying:

• locked_mass decays exponentially with UnlockRate (default 648,000 blocks = ~60-day half-life)
• conviction follows a coupled decay/growth formula driven by ConvictionMaturityRate (default 648,000 blocks = ~60-day half-life) — unless locked to the owner hotkey, in which case conviction tracks locked_mass directly
• After ~60 days, half of locked mass has decayed
• You can unstake the difference between your original lock and current locked_mass

The fact that both timescales are equal (648,000) under the new defaults means the coupling factor between locked_mass decay and conviction decay simplifies considerably — they track each other much more closely than they did under the v2 pre-update defaults.

Perpetual Locks (Opt-In)

After calling set_perpetual_lock(netuid, true), your lock becomes perpetual:

• locked_mass remains constant
• conviction grows exponentially from current value toward locked_mass (non-owner hotkey) OR equals locked_mass instantly (owner hotkey)
• Cannot unstake — perpetual locks stay locked unless you toggle back to decaying mode with set_perpetual_lock(netuid, false)

Subnet Owner's Own Locks

Subnet owners receive additional treatment:

• Auto-locked owner cut — The owner's share of emissions is automatically locked each block, building conviction continuously. Togglable per subnet by the owner via sudo_set_owner_cut_auto_lock_enabled(netuid, enabled). DefaultOwnerCutAutoLockEnabled is currently true on devnet-ready, but PR #2695 (open, blocked on review) flips it to false — once that ships owners must explicitly enable auto-lock per subnet.
• Owner locks follow the same default-decaying behaviour as everyone else; opt into perpetual with set_perpetual_lock(true).
• Since owners lock to their own hotkey, they get instant conviction like anyone else locking to the owner hotkey.

4. The Numbers

System Parameters (Post PR #2687 Defaults)

Both rates can be tuned by root via admin-utils extrinsics. Under the v2 pre-update defaults (UnlockRate 1,142,108 / MaturityRate 216,000) the system had a 5.3x speed gap between unlock and maturity — the new equal defaults remove that gap, making locked_mass and conviction decay/grow at the same fundamental pace.

Conviction Growth Timeline (Perpetual Lock to a Non-Owner Hotkey)

How conviction grows over time when locked_mass stays constant, under the new 60-day half-life:

Locked Mass Decay Timeline (Decaying Lock — the default)

How locked_mass decays under the new 60-day half-life:

So in practice: a lock left in default-decaying mode is down to ~12.5% after 6 months and ~1.5% after a year. To build durable conviction you need to opt into perpetual.

5. Worked Example

Scenario: A validator locks 10,000 alpha on subnet 64 to their own (non-owner) hotkey, then opts into perpetual mode immediately.

Phase 1: Perpetual Lock (after set_perpetual_lock(64, true))

locked_mass = 10,000 alpha (constant while perpetual)

Note: Perpetual locks cannot be unstaked. Locked mass stays at 10,000 alpha until you toggle decay back on.

Phase 2: Toggle to Decaying

At day 365, the validator calls set_perpetual_lock(64, false). Now both locked_mass and conviction decay together with the same 60-day half-life (starting from the day-365 value, ~9,850):

After 1 year of decay, the validator can unstake essentially all of the original 10,000 alpha.

Scenario B: Lock Directly Without Perpetual Opt-In

Same lock but the validator never calls set_perpetual_lock. The lock decays from day 0:

Decaying-mode conviction tracks closely behind locked_mass because both share the same 60-day timescale.

6. Subnet Owner Locks & Instant Conviction

Instant conviction applies to anyone locking to the subnet owner's hotkey, not just the owner themselves:

• Any staker who locks alpha to the owner's hotkey gets conviction = locked_mass immediately.
• Owner cut auto-locked (when OwnerCutAutoLockEnabled[netuid] = true): Each block, the owner's emissions share is automatically locked to their subnet ownership hotkey. PR #2695 (pending) flips the default to false — once merged, subnets won't auto-lock unless the owner explicitly enables it via sudo_set_owner_cut_auto_lock_enabled(netuid, true). Currently default is true on devnet-ready.
• No initial alpha distribution: In v2, subnet registration does not distribute initial alpha to the owner. Conviction builds solely through the auto-locked owner cut from ongoing emissions (if enabled) or via the owner manually locking.
• Decaying by default: Owner locks also default to decaying mode. The owner can opt into perpetual with set_perpetual_lock(netuid, true).
• Aggregate tracking: Owner-targeted locks are split into OwnerLock (perpetual) and DecayingOwnerLock (decaying) storage maps.

Incentive Implications

• Independent validators become less attractive for conviction-focused stakers (they must wait through maturity).
• Subnet owners benefit from a gravitational pull of locks toward their hotkey.
• Owners can disable the owner-cut auto-lock if they want their emission share to remain unlocked/liquid, at the cost of slower personal conviction growth.
• Because decaying is now default, casual lockers will silently lose conviction over time if they never opt into perpetual — a friction point worth highlighting in the UI.

7. Subnet King Mechanism

Note: The subnet king mechanism is currently disabled by design. The code exists but the ownership-transfer call is commented out. When enabled, the rules would be:

After a subnet has been active for 1 year (365.25 days), ownership could transfer via the "subnet king" mechanism:

Eligibility Requirements

• Subnet must be at least 365.25 days old
• Total rolled conviction across the entire subnet (all hotkeys, all coldkeys, including owner) must be at least 10% of SubnetAlphaOut. This is a subnet-wide gate, not per-challenger.
• The hotkey with the highest aggregate conviction wins. Conviction is aggregated per hotkey (from all coldkeys locking to that hotkey), not per coldkey.

How It Works

• Aggregate calculation: The system sums conviction across all locks for each hotkey using the relevant aggregate (HotkeyLock + DecayingHotkeyLock for non-owner, OwnerLock + DecayingOwnerLock for the current owner).
• Comparison: The hotkey with the highest total conviction becomes the subnet king.
• Transfer: Ownership transfers, and the lock aggregates swap:
  • Old owner's OwnerLock / DecayingOwnerLock → become non-owner HotkeyLock / DecayingHotkeyLock against the old owner's hotkey
  • New owner's non-owner HotkeyLock / DecayingHotkeyLock → become OwnerLock / DecayingOwnerLock
• Instant conviction retained: The new owner keeps their conviction value but now has instant-conviction status for future locks to their hotkey.

Design rationale: This mechanism prevents permanent ownership monopolies while requiring challengers to demonstrate long-term commitment through locked alpha and conviction growth.

8. What You Can and Can't Do

[YES] Allowed Actions

• Top up existing lock: Add more alpha to your existing lock (must target the same hotkey)
• Move lock to a different hotkey: You can move your lock to a different hotkey on the same subnet. If the destination hotkey is owned by the same coldkey, conviction is preserved. If owned by a different coldkey, conviction resets to zero.
• Toggle decay mode: Switch between perpetual and decaying at any time with set_perpetual_lock(netuid, perpetual_flag)
• Partial unstaking (decaying only): Unstake the difference between original lock and current locked_mass
• Owner: disable own-subnet auto-lock: Subnet owner can toggle sudo_set_owner_cut_auto_lock_enabled(netuid, false) to stop the owner cut from being auto-locked.

[NO] Not Allowed

• Unstake perpetual locks: You must first toggle to decaying mode and wait for mass to decay.
• Cross-subnet transfers: Locks are subnet-specific and cannot be moved between subnets.
• Multi-hotkey locks: You cannot have multiple locks to different hotkeys on the same subnet from one coldkey.
• Lock hotkey changes: If you have an active lock on a subnet, you can't lock to a different hotkey without first removing the existing lock.
• Coldkey swap with active locks on destination: A coldkey swap requires the destination coldkey to have no active locks. The source coldkey's locks transfer to the destination, but only if the destination is clean.

9. Technical Reference

Storage Maps

LockState Structure

pub struct LockState {
    pub locked_mass: AlphaBalance,  // Current locked alpha (decays if non-perpetual)
    pub conviction: U64F64,         // Governance weight (grows/decays based on mode)
    pub last_update: u64,           // Block number of last roll-forward
}

Roll-Forward Formula

When reading lock state, the system rolls forward from last_update to the current block:

// Time elapsed in blocks
dt = current_block - last_update

// Decay factors
decay_x = exp(-dt / UnlockRate)              // = exp(-dt / 648,000)
decay_z = exp(-dt / ConvictionMaturityRate)  // = exp(-dt / 648,000)

// Coupling factor — simplifies because rates are equal under new defaults
gamma = UnlockRate * (decay_x - decay_z) / (UnlockRate - MaturityRate)
// When UnlockRate == MaturityRate this reduces to: gamma = dt/UnlockRate * decay_x

// State update
if perpetual:
    locked_mass_new = locked_mass_old              // No decay
else:
    locked_mass_new = locked_mass_old * decay_x    // Exponential decay

conviction_new = decay_z * conviction_old + gamma * locked_mass_old

For locks against the subnet owner's hotkey, the formula simplifies to conviction = locked_mass (instant conviction, no roll-forward growth needed).

Key Extrinsics

• lock_stake(hotkey, netuid, amount) — Lock alpha to a hotkey on a subnet (decaying by default).
• set_perpetual_lock(netuid, perpetual: bool) — Toggle between decaying (false) and perpetual (true) mode.
• sudo_set_owner_cut_auto_lock_enabled(netuid, enabled: bool) — Subnet-owner-only. Toggle whether owner-cut emissions are auto-locked.

Key RPCs

• get_coldkey_lock(coldkey, netuid) -> Option<LockState> — New in PR #2687. Returns the live (rolled-forward) lock state for a given coldkey on a given subnet, including locked_mass, conviction, and last_update block. Single call gives you both balance and accrued conviction.
• get_hotkey_conviction(hotkey, netuid) -> U64F64 — Aggregate conviction for a hotkey on a subnet.
• get_most_convicted_hotkey_on_subnet(netuid) -> Option<AccountId> — Returns the hotkey with the highest total conviction (i.e. the subnet-king candidate).

Migration

Shipped with PR #2687:

• migrate_reset_tnet_conviction_locks — clears Lock, HotkeyLock, DecayingHotkeyLock, OwnerLock, DecayingOwnerLock, and DecayingLock storage on testnet. This wipes any pre-#2687 conviction state. Mainnet has not had v2 conviction live yet, so this migration is testnet-only in practice.

Analysis prepared by Taostats based on subtensor PRs #2658 and #2687 (#2687 merged to devnet-ready 2026-05-25, propagated to testnet same day).

This document is informational only.