Struct StartArgs 

pub struct StartArgs {

    pub repo: PathBuf,
    pub intent: String,
    pub engine: EngineChoice,
    pub max_iterations: Option<u32>,
    pub state_dir: PathBuf,
    pub project: Option<CoderProject>,
    pub model: Option<String>,
    pub routing_exclusions: Vec<String>,
    pub repair_invokes: Option<u32>,
    pub transient_retries: Option<u32>,
    pub discussion_id: Option<String>,
    pub base: Option<String>,
    pub browser: bool,
    pub distributed: bool,
    pub workers: Vec<String>,
}

Fields

repo: PathBuf

intent: String

engine: EngineChoice

max_iterations: Option<u32>

None falls back to the operator config’s default_max_iterations (~/.car/coder.toml), resolved inside start_session against the config it already loads — so the file is read once per start, and the preference / keep-on-failure / iteration defaults can’t drift.

state_dir: PathBuf

project: Option<CoderProject>

When set, this session works on a CAR-managed project (repo is the project’s repo path). Carries the project metadata needed for commit-to-main delivery and, for Agent projects, draft persistence and rebuild-in-place registration. None = raw-repo session.

model: Option<String>

Per-session native-loop model pin (overrides ~/.car/coder.toml’s model). None/blank falls back to the config, then adaptive routing.

routing_exclusions: Vec<String>

Canonical model names the adaptive native loop must not route to. This is a strict separation boundary when non-empty. Ignored if the effective session model is pinned.

repair_invokes: Option<u32>

External-engine hypothesis budget. None = the engine default.

transient_retries: Option<u32>

External-engine availability budget. None = the engine default.

discussion_id: Option<String>

A coder.discuss conversation this run came out of. Its agreed constraints are folded into contract derivation, so something stated once in the discussion does not have to be restated in the intent, and the session records the provenance. An unknown id is a hard error — a run that silently drops its grounding is worse than one that refuses.

base: Option<String>

Start the worktree at this commit-ish instead of the repository’s HEAD — e.g. another developer’s published branch. Resolved to a full SHA before anything is provisioned; an unknown revision fails the start. None/blank = the discussion’s prior delivered commit, otherwise HEAD. Not valid for project sessions, which deliver straight to the project’s main.

browser: bool

Expose the assistant’s browser tools to this session’s native loop. False unless the caller explicitly opts in.

distributed: bool

Farm this session’s subtasks across reachable CAR instances, not just this machine. Only the foreman engine can use it; every other rung runs here regardless.

OFF by default and never inferred: distribution spends agent quota on other people’s machines, which is a thing to ask for rather than a default that could be wrong. Mirrors foreman.run { distributed }.

workers: Vec<String>

Restrict placement to these instances. Empty = every instance that can serve the repository. Mirrors foreman.run { workers }, which the operator who knows their own fleet already has.