Stage 1: Dry Run

The dry run simulates your Cairo module against live RPC data. It produces the key set that the fetcher later turns into proofs.

Entry point

crates/dry_run/src/lib.rs

Execution flow

Load the compiled Cairo module.
Construct HDPDryRunInput (compiled class, params, injected state).
Run the Cairo VM with CustomHintProcessor.
Syscall handlers call RPC endpoints and collect keys.
Write dry_run_output.json with the serialized handler state.

The dry run uses the all_cairo layout in the Cairo VM.

Output artifacts

dry_run_output.json: serialized SyscallHandler containing key sets for each handler.
Printed output (optional): HDPDryRunOutput with task_hash and output_root fields.

`dry_run_output.json` structure (high level)

The file is a JSON serialization of the Rust SyscallHandler. At a high level it looks like:

{
  "call_contract_handler": {
    "evm_call_contract_handler": { "key_set": [ ... ] },
    "starknet_call_contract_handler": { "key_set": [ ... ] },
    "injected_state_call_contract_handler": { "key_set": { "<label>": [ ... ] } },
    "unconstrained_call_contract_handler": { "key_set": [ ... ] }
  }
}

This file is the only input needed by the fetcher.

If you pass --print_output, the command prints the decoded HDPDryRunOutput struct, which includes task hash and output root values.

Requirements

Dry run requires RPC endpoints for any chain your module queries.

CLI usage

hdp dry-run -m <module.compiled_contract_class.json> --print_output

Important flags:

--output <path>: output path for dry_run_output.json
--inputs <path>: JSON module input parameters
--injected_state <path>: injected state JSON
--print_output: prints the Cairo output segment

HDP Cairo Documentation