# Architecture

```mermaid
flowchart TB
  APP[Caller / agent_session_manager]
  SDK[AntigravityCliSdk]
  OPT[Options + GovernedLaunch]
  RT[Runtime.CLI]
  CORE[cli_subprocess_core Session]
  PROFILE[ProviderProfiles.Antigravity]
  AGY[agy binary]

  APP --> SDK
  SDK --> OPT
  SDK --> RT
  RT --> CORE
  CORE --> PROFILE
  PROFILE --> AGY
```

`AntigravityCliSdk` is not a second subprocess runtime. It is a typed SDK layer
over `cli_subprocess_core`:

1. `Options` validates caller input and resolves the core model payload.
2. `ArgBuilder` renders `agy --print <prompt>` and supported flags.
3. `Runtime.CLI.Profile` delegates decode/exit handling to the core
   Antigravity provider profile.
4. `Stream` converts normalized core events into SDK event structs.
5. `agent_session_manager` can use `AntigravityCliSdk.Runtime.CLI` as the SDK
   runtime for the `:antigravity` provider.

The core lane and SDK lane intentionally share the same parser behavior:
Antigravity stdout is plain text and non-empty lines become assistant deltas.
Core terminal result fields remain authoritative; accumulated text is only a
missing-result fallback. Total run deadline, stream idle wait, and transport
orphan reaping are separate lifecycle controls.