Enum Mechanism 

pub enum Mechanism {
    Env(&'static str),
    EnvFile(&'static str),
    FlagDir(ConflictOption),
    FlagFile(ConflictOption),
}

How an adapter points its agent at the profile: the cross product of {variable, flag} x {directory, file}. This is the complete, closed set — it is the same vocabulary the probe harness speaks (sandbox/probes/common.sh, env: / envfile: / flagdir: / flagfile:), so a fifth variant here would be a mechanism no probe can exercise.

Three renderings, one per consumer — do not collapse them

1. std::fmt::Display — the path-free sentence, for error messages. An error message cannot name a path, because check_conflicts refuses an argument before any plan exists and therefore before any path has been chosen. It prints the placeholder <dir> / <file> instead.
2. Mechanism::sentence_for — the concrete sentence that becomes PlannedLaunch::mechanism, for the launch report. A report line should name the exact path it is about to create, so here the placeholder is the real path.
3. Mechanism::probe_token — the machine identifier the evidence pipeline consumes. The human text above may be reworded freely; this token may not.

That (1) and (2) differ in form for flag mechanisms is deliberate, not drift: they answer different questions at different times. For environment mechanisms they coincide, because there is no path in the sentence to differ over.

All three are generated from this one value, and so is the launch itself: Mechanism::plan (crate internal, so not linked here — a public doc comment cannot link a private item) dispatches on the variant and takes the variable name or flag spelling out of the variant’s own payload. An adapter passes no name and no flag, so there is no second string for the first to drift from.

Variants

Env(&'static str)

A variable set to the profile directory.

EnvFile(&'static str)

A variable set to a file inside the profile directory.

FlagDir(ConflictOption)

An option passed the profile directory.

FlagFile(ConflictOption)

An option passed a file inside the profile directory.

Implementations

impl Mechanism

pub fn conflict_option(&self) -> Option<&ConflictOption>

The option this mechanism itself occupies, if it is a flag. check_conflicts scans it alongside the adapter’s declared extra conflicts, so an adapter cannot accept a flag it uses itself.

pub fn sentence_for(&self, target: &Path) -> String

The report sentence naming target, the path this mechanism points at. Environment mechanisms name the variable and ignore target.

pub fn probe_token(&self) -> String

The evidence pipeline’s identifier, e.g. env:CODEX_HOME or flagfile:--config.

impl Mechanism

pub(crate) fn plan( &self, adapter: &dyn Adapter, ctx: &PlanContext<'_>, ) -> Result<PlannedLaunch>

Plans a launch that points the agent at its profile through this mechanism.

The variable name and the flag spelling are read out of the mechanism’s own payload, and the report sentence comes from Mechanism::sentence_for on the very same value. There is no parameter through which an adapter could pass a second name, so declaring Env("A") and launching with "B" is not expressible — the two used to be separate arguments and agreed only because every adapter happened to pass the same constant twice.

It lives here rather than in metadata because planning needs this module’s private machinery — executable discovery, the case-twin check and path materialization state.

Adapter-specific extras stay in the adapter: plan() returns no notes, and an adapter that has one (Codex’s logged-out note, Aider’s layering note) pushes it onto the result.

Trait Implementations

impl Clone for Mechanism

fn clone(&self) -> Mechanism

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Copy for Mechanism

impl Debug for Mechanism

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Display for Mechanism

fn fmt(&self, formatter: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Eq for Mechanism

impl PartialEq for Mechanism

fn eq(&self, other: &Mechanism) -> bool

Equality operator ==.

fn ne(&self, other: &Rhs) -> bool

Inequality operator !=.

impl StructuralPartialEq for Mechanism