Local mode vs Testnet mode

The simulator explicitly supports two modes (spec section 31). They serve different jobs and must never be confused:

Local simulation                     Testnet integration
--------------------------           --------------------------
Crucible Simulator                   Crucible Simulator
      |                                    |
      v                                    v
Local deterministic environment      Soroban adapter
      |                                    |
      v                                    v
Fast, reproducible, offline          Stellar Testnet (optional)

Local mode (default)

The whole repository — every crate, every test suite, the CLI, the examples, the benchmarks — runs against the local deterministic environment. It requires no network, no accounts, no SDK.

• Deterministic: same configuration + state + operations + seed ⇒ the same result, bit for bit, on any machine.
• Fast: confidential transfers run in tens of microseconds.
• Inspectable: private simulation state is visible to the harness through the labeled inspect_private_* APIs.

This is where scenarios are designed, fixtures are built, and bugs are reproduced.

Testnet mode (optional, on the roadmap)

Testnet execution routes normalized operations through the Soroban adapter (crates/adapters/soroban) toward actual Stellar infrastructure. Today the TestnetAdapter is an explicit unimplemented boundary: it exists so callers and scenario code can target the interface, and it fails with a structured unimplemented error rather than pretending to work.

When the SDK wiring lands, testnet execution will be:

• Slower and optional — never part of the deterministic suites.
• Separately gated — run explicitly, outside cargo test, against a live network.
• Cross-checked — the same AdapterRequest shapes drive both modes, so a scenario passing locally and failing on testnet pinpoints a real semantic divergence rather than an interface mismatch.

Guarantee

Local simulation never depends on Testnet access: the deterministic test suite, CLI, examples, and benchmarks run offline, in CI, on every push.