Air is a standalone Rust binary structured around a central gRPC server that receives task delegation from Mountain. It runs as a persistent sidecar process alongside Mountain, offloading resource-intensive operations so the editor remains responsive. Internal modules handle distinct responsibilities: updates, downloads, authentication, and health monitoring.

graph TB
    subgraph "Air - Background Daemon"
        Binary["Binary.rs - Entry Point"]
        VineServer["Vine gRPC Server\nPort 50053"]
        UpdateMgr["Updates/\nUpdate Lifecycle"]
        Downloader["Downloader/\nResilient Downloads"]
        AuthService["Authentication/\nCrypto Signing"]
        HealthCheck["HealthCheck/\nProcess Monitoring"]
        Metrics["Metrics/\nTelemetry Collection"]
        HTTP["HTTP/\nHTTP Client with DNS"]
        Initialize["Initialize/\nStartup Sequence"]
        Logging["Logging/\nStructured Tracing"]
    end

    subgraph "Mountain - Main Application"
        MountainCore["Mountain Core"]
        VineClient["Vine gRPC Client"]
    end

    subgraph "External"
        Cloud["Update Servers / Registry"]
    end

    MountainCore --> VineClient
    VineClient --> VineServer
    VineServer --> UpdateMgr
    VineServer --> Downloader
    VineServer --> AuthService
    VineServer --> HealthCheck
    UpdateMgr --> Cloud
    Downloader --> Cloud
    Binary --> Initialize
    Initialize --> VineServer
    Initialize --> Logging
    Initialize --> Metrics

Key Modules

Path	Description
`Source/Binary.rs`	Binary entry point; bootstraps Tokio runtime and starts daemon
`Source/Initialize/`	Startup sequence: config loading, server binding, state init
`Source/Vine/`	gRPC server implementation using tonic; routes incoming calls
`Source/Updates/`	Update lifecycle: check, download, verify, apply patches
`Source/Downloader/`	Resilient download manager with pause, resume, and retry
`Source/Authentication/`	Cryptographic signing of binaries and secure token storage
`Source/HTTP/`	HTTP client configured to use Mist local DNS resolver
`Source/HealthCheck/`	Self-monitoring and watchdog for process health
`Source/Metrics/`	Telemetry collection and reporting to Mountain
`Source/Logging/`	Structured tracing output via the `tracing` crate
`Source/CLI/`	Command-line argument parsing for daemon startup options
`Source/Resilience/`	Retry logic and circuit breakers for network operations
`Source/Security/`	Signature verification and secure storage utilities
`Source/Configuration/`	Runtime configuration loading and hot-reload support
`Source/Library.rs`	Library root exposing the public API for integration tests

Data Flow

The following sequence shows how Mountain delegates an update task to Air and receives progress notifications.

sequenceDiagram
    participant Mountain as Mountain Core
    participant AirGRPC as Air gRPC Server
    participant Updates as Update Manager
    participant Downloader as Downloader
    participant Cloud as Update Server

    Mountain->>AirGRPC: CheckForUpdate (Vine/Air.proto)
    AirGRPC->>Updates: Dispatch check request
    Updates->>Cloud: HTTP GET /releases/latest
    Cloud->>Updates: Release manifest
    Updates->>AirGRPC: UpdateAvailable response
    AirGRPC->>Mountain: Return update metadata

    Mountain->>AirGRPC: StartDownload (artifact URL)
    AirGRPC->>Downloader: Begin resilient download
    loop Progress events
        Downloader->>AirGRPC: ProgressEvent (bytes/total)
        AirGRPC->>Mountain: Stream progress notification
    end
    Downloader->>AirGRPC: DownloadComplete
    AirGRPC->>Mountain: Ready to apply

Port allocation:

Air listens on [::1]:50053 (reserved for the Air daemon).
Cocoon uses [::1]:50052 (the VS Code extension host).

Integration Points

Connecting Element	Direction	Mechanism	Description
Mountain	Bidirectional	gRPC over Vine/Air.proto	Mountain delegates tasks; Air streams progress events back
Mist	Inbound	Local DNS resolver	Air configures its HTTP client to use Mist’s DNS for secure resolution
Vine	Inbound	Protocol definition	Air.proto defines service contracts; tonic generates Rust server stubs

Configuration

Parameter	Source	Description
Bind address	CLI flag / environment	Default `[::1]:50053`; overridable for testing
Update server URL	Configuration file	Base URL for checking and downloading updates
Download cache directory	Configuration file	Where partial downloads are stored for resume
Health check interval	Configuration file	Frequency of self-monitoring checks
Log level	`RUST_LOG` environment variable	Tracing filter for structured log output

Air is spawned automatically by Mountain at startup. Mountain detects whether an Air process is already running before spawning a new instance.

Air overview
Vine protocol
Mountain deep dive Related: Architecture

Key Modules

Data Flow

Integration Points

Configuration

Related Documentation