Core Concepts

These pages explain how Xian behaves as a deterministic application platform, not just how to call one contract function at a time.

Start With These Mental Models

• Transaction Lifecycle for the path from signed payload to finalized block
• Consensus & Finality for the CometBFT boundary and validator agreement
• The ABCI Layer for what xian-abci actually owns
• State Model for how contract data is stored and committed
• Chi & Metering for execution pricing and limits
• Deterministic Execution for the rules that keep every validator aligned

Runtime-Specific Concepts

• The Xian VM for the split between Python authoring and VM-native execution policy
• Parallel Block Execution for speculative serial-equivalent execution
• Time & Block Policy for now, idle blocks, and block-production policy

Privacy and ZK Concepts

• Shielded & ZK Stack for the runtime verifier, zk_registry, xian-zk, shielded-note-token, shielded-commands, and relayer

If you are new to Xian, read this section after the Architecture Overview and before diving into the lower-level API or node docs.