Enum SystemPrompt 

pub enum SystemPrompt {
    Replace(String),
    Append(String),
}

What a host says on top of what the workspace says.

basis ships no system prompt of its own and this does not give it one: the text is the host’s, and a build that never names this type behaves exactly as it did. What it removes is the workaround — an embedding host that wanted its product to have a voice, or to say for my runs, answer in Chinese, had to write into the user’s repository’s AGENTS.md, which is the one file that is not the host’s to edit.

One enum rather than two builder methods, because the two are alternatives and not layers: a host either replaces what the workspace said or adds to it, and asking the type system to hold that is cheaper than documenting what happens when both are set.

Both scopes already had their weakest end covered — the global AGENTS.md is a personal append below every workspace file. Neither variant touches the skills block: mentra appends that itself, after whatever basis hands it.

Variants

Replace(String)

The host’s text alone. Discovered context files stay out of the prompt entirely — including the global one — which is what makes this usable for a host whose product is not “an agent that reads your repository”.

They are still reported: run_started names what discovery found, because that question — which files does this workspace have — has one true answer regardless of what the host did with them, and the host that replaced the prompt is the one party that already knows it did.

Replacing with nothing is not an error. It is the way to say no system prompt at all, and it renders as None for the same reason an empty workspace does.

Append(String)

The host’s text after the rendered context, as the strongest block.

Last because the rendered block tells the model that later blocks are more specific and take precedence, and the host’s text is more specific than any file on disk: it is the statement of the program actually running this agent, about this deployment, which no repository can know about — and a knob that a repository could override by writing a file is not a knob. It is appended verbatim, outside the <context> framing, because it did not come from a file and giving it a path would say it did.

Appending nothing is a no-op rather than an error: there is one obvious meaning and it is the one the workspace already had.

Trait Implementations

impl Clone for SystemPrompt

fn clone(&self) -> SystemPrompt

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for SystemPrompt

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

Formats the value using the given formatter.

impl<'de> Deserialize<'de> for SystemPrompt

fn deserialize<__D>(__deserializer: __D) -> Result<Self, __D::Error>

where __D: Deserializer<'de>,

Deserialize this value from the given Serde deserializer.

impl Eq for SystemPrompt

impl PartialEq for SystemPrompt

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

Equality operator ==.

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

Inequality operator !=.

impl Serialize for SystemPrompt

fn serialize<__S>(&self, __serializer: __S) -> Result<__S::Ok, __S::Error>

where __S: Serializer,

Serialize this value into the given Serde serializer.

impl StructuralPartialEq for SystemPrompt