## MODIFIED Requirements

### Requirement: Supervisor is opt-in and disabled by default
The Host Agent SHALL NOT start, adopt-check, or supervise Appium unless
`HOST_AGENT_DEPENDENCY_SUPERVISOR_ENABLED` is explicitly set to true. Appium
supervision SHALL additionally require `HOST_AGENT_APPIUM_SUPERVISED=true`
and SHALL default to false.

#### Scenario: Default configuration behaves exactly as before
- **WHEN** a Host Agent starts with no
  `HOST_AGENT_DEPENDENCY_SUPERVISOR_ENABLED` or related Appium environment
  variable set
- **THEN** the Host Agent does not attempt to connect to, probe, or spawn
  Appium, and its heartbeat/claim behavior is unchanged

#### Scenario: Top-level flag on and Appium flag off
- **WHEN** `HOST_AGENT_DEPENDENCY_SUPERVISOR_ENABLED=true` and
  `HOST_AGENT_APPIUM_SUPERVISED=false`
- **THEN** the Host Agent does not probe, adopt, or spawn Appium

### Requirement: Spawn supervised dependencies that are not already running
The Host Agent SHALL spawn Appium as a child process when Appium supervision is
enabled and no healthy Appium instance is adopted, via
`appium --address <host> --port <port>` and SHALL forward the child
process's stdout/stderr into the Host Agent's own logging, tagged by dependency
name.

#### Scenario: Appium is not running at Host Agent startup
- **WHEN** Appium supervision is enabled and no healthy Appium instance is
  already listening
- **THEN** the Host Agent spawns Appium before proceeding to its first
  device-connect attempt, and its output is visible in Host Agent logs

#### Scenario: Spawn fails because the executable is missing
- **WHEN** the Host Agent attempts to spawn Appium but `appium` is not found
  on `PATH`
- **THEN** the Host Agent logs a dependency-supervisor-specific startup error
  naming the missing dependency, distinct from a runtime crash of an
  already-started process

## ADDED Requirements

### Requirement: Runtime supervision settings are retired
The Host Agent SHALL reject `HOST_AGENT_RUNTIME_SUPERVISED`,
`HOST_AGENT_RUNTIME_HOST`, and `HOST_AGENT_RUNTIME_PORT` because the
standalone Runtime service no longer exists.

#### Scenario: A legacy Runtime supervision variable is set
- **WHEN** startup configuration includes any removed Runtime supervision
  variable
- **THEN** configuration fails with an actionable migration error