Polygon PoS checkpoint finality guarantees during Ethereum mainnet congestion

Context

The Polygon PoS chain achieves probabilistic finality through periodic checkpoint submissions to Ethereum. Each checkpoint represents a state root that becomes immutable once the corresponding Ethereum transaction reaches sufficient confirmations. The research indicates that Ethereum congestion can delay checkpoint inclusion, extending the window where Polygon blocks remain reversible.

Unresolved behavior

Documentation describes the checkpoint mechanism but does not specify whether the Polygon protocol enforces any maximum delay threshold before considering a checkpoint submission failed, or whether validators continue producing blocks on a fork that may never be checkpointed. The slashing conditions reference downtime and double-signing, but the interaction between prolonged checkpoint delays and validator incentives remains ambiguous.

Goal

Determine the exact conditions under which a Polygon PoS block transitions from probabilistic to economic finality when Ethereum mainnet experiences sustained high gas prices or block space contention.

Specific questions:

1. Does the Polygon consensus protocol define a maximum checkpoint submission delay after which validators must halt or fork?
2. How are validator rewards and slashing calculations affected when checkpoints are delayed beyond typical intervals?
3. Is there a documented fallback mechanism for checkpoint submission during extended Ethereum congestion?