Enum SystemPromptMode 

#[non_exhaustive]
pub enum SystemPromptMode {
    Append,
    Override,
    Other(String),
}

Available on crate features unstable_protocol_v2 and unstable_session_system_prompt only.

UNSTABLE

This capability is not part of the spec yet, and may be removed or changed at any point.

How the Agent combines a client-provided system prompt with its own instructions.

Unknown modes parse as SystemPromptMode::Other so they can be stored, proxied, or forwarded. An Agent MUST return an error for a mode it does not support rather than treating it as append or override.

Variants (Non-exhaustive)

Non-exhaustive enums could have additional variants added in future. Therefore, when matching against variants of non-exhaustive enums, an extra wildcard arm must be added to account for any future variants.

Append

Add the content to the Agent’s own instructions rather than replacing them.

Every Agent that advertises session.systemPrompt supports this mode. Agents SHOULD give the content system-level precedence, for example in the model’s system prompt or developer instructions rather than in user-turn content. Where it is placed and how it is formatted is implementation-defined.

Override

Replace the Agent’s built-in default instructions with the content.

This does not change tool availability, MCP servers, permissions, or session configuration. Context the Agent supplies from the workspace or environment MAY still be included. Clients that use this mode take responsibility for any tool guidance or safety instructions the Agent’s default instructions provided, and MUST only use it when the Agent advertises session.systemPrompt.mode.override.

Other(String)

Custom or future system prompt mode.

Values beginning with _ are reserved for implementation-specific extensions. Unknown values that do not begin with _ are reserved for future ACP variants.

Trait Implementations

impl Clone for SystemPromptMode

fn clone(&self) -> SystemPromptMode

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for SystemPromptMode

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

Formats the value using the given formatter.

impl Default for SystemPromptMode

fn default() -> SystemPromptMode

Returns the “default value” for a type.

impl<'de> Deserialize<'de> for SystemPromptMode

fn deserialize<__D>( __deserializer: __D, ) -> Result<SystemPromptMode, <__D as Deserializer<'de>>::Error>

where __D: Deserializer<'de>,

Deserialize this value from the given Serde deserializer.

impl Eq for SystemPromptMode

impl JsonSchema for SystemPromptMode

fn schema_name() -> Cow<'static, str>

The name of the generated JSON Schema.

fn schema_id() -> Cow<'static, str>

Returns a string that uniquely identifies the schema produced by this type.

fn json_schema(generator: &mut SchemaGenerator) -> Schema

Generates a JSON Schema for this type.

fn inline_schema() -> bool

Whether JSON Schemas generated for this type should be included directly in parent schemas, rather than being re-used where possible using the $ref keyword.

impl PartialEq for SystemPromptMode

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

Equality operator ==.

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

Inequality operator !=.

impl Serialize for SystemPromptMode

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

where __S: Serializer,

Serialize this value into the given Serde serializer.

impl StructuralPartialEq for SystemPromptMode