Trait HookFormat 

pub trait HookFormat: Send + Sync {
    // Required methods
    fn parse_input(&self, stdin: &str) -> Result<HookInput, ParseError>;
    fn render_response(&self, verdict: Verdict) -> HookResponse;

    // Provided methods
    fn render_context(&self, _context: &str) -> HookResponse { ... }
    fn gated_policy(&self) -> GatedPolicy { ... }
    fn render_deny(&self, _reason: &str) -> HookResponse { ... }
    fn render_ask(&self, _reason: &str) -> HookResponse { ... }
}

Required Methods

fn parse_input(&self, stdin: &str) -> Result<HookInput, ParseError>

fn render_response(&self, verdict: Verdict) -> HookResponse

Provided Methods

fn render_context(&self, _context: &str) -> HookResponse

Surface explanatory context to the model on a non-approval without changing the permission decision (the command still flows through the tool’s normal approval path, and the user’s own allowlist still applies).

The default abstains silently — same as today’s empty deny body. A target overrides this only when its hook schema has a verified field for injecting model-visible context without a permission decision.

fn gated_policy(&self) -> GatedPolicy

How this harness’s hook must handle a GATED command (one safe-chains does not auto-approve), derived from its capabilities (docs/design/harness-capability-model.md):

• Defer — stay silent; the harness’s own per-command human review is the check (Claude).
• Deny — veto it; the harness has no human review and no escalate (Codex).
• Ask — escalate to an in-the-moment human prompt (Antigravity’s ask).

fn render_deny(&self, _reason: &str) -> HookResponse

The hook output that VETOES a gated command, for a Deny harness. Default abstains (so a stray call can’t fail open). The shape must be exactly what the harness supports, or a harness that “continues on malformed output” (e.g. Codex) fails open.

fn render_ask(&self, _reason: &str) -> HookResponse

The hook output that ESCALATES a gated command to a human prompt, for an Ask harness. Default abstains. (Antigravity fails CLOSED on a malformed/absent decision, so an Ask target must always emit a valid decision.)

Dyn Compatibility

This trait is dyn compatible.

In older versions of Rust, dyn compatibility was called "object safety".

Implementors