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Normative spec: the Karst specification is the canonical definition of this upgrade. This page records activation data and operational pointers; it does not restate the spec.
Karst (Upgrade 19) introduced the L2 Contract Manager, activated a subset of Osaka EIPs on L2, promoted CANNON_KONA to the respected game type, and reduced the bn256Pairing precompile input limit as a preemptive Glamsterdam defense. op-geth and op-program do not support Karst — see the end-of-support notice. Minimum component versions (from Upgrade 19 notice):

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What changed

Per the spec overview and the Upgrade 19 notice:
  • L2 Contract Manager (L2CM): governance-approved L2 predeploy upgrades through a consensus-layer mechanism.
  • Osaka EIPs on L2, including EIP-7825 (transaction gas limit cap, not applied to deposits), EIP-7823 and EIP-7883 (MODEXP bounds and gas), EIP-7910 (eth_config), EIP-7939 (CLZ opcode), and EIP-7951 (secp256r1 gas cost alignment).
  • Reduced the bn256Pairing precompile maximum input size from 427 to 300 pairs (Glamsterdam defense).
  • Promoted CANNON_KONA (game type 8) to the respected game type, making kona-client the primary fault proof program used for withdrawals.
  • Consensus layer: network upgrade transactions applied during derivation.