Struct SystemPromptSlots 

pub struct SystemPromptSlots {
    pub style: Option<AgentStyle>,
    pub role: Option<String>,
    pub guidelines: Option<String>,
    pub response_style: Option<String>,
    pub extra: Option<String>,
}

Slot-based system prompt customization with intent-based style selection.

Users can customize specific parts of the system prompt without overriding the core agentic capabilities (tool usage, autonomous behavior, completion criteria). The default agentic core is ALWAYS included.

Assembly Order

[role]            ← Custom identity/role (e.g. "You are a Python expert")
[CORE]            ← Always present: Core Behaviour + Tool Usage Strategy + Completion Criteria
[guidelines]      ← Custom coding rules / constraints
[response_style]  ← Custom response format (replaces default Response Format section)
[extra]           ← Freeform additional instructions

Intent-Based Selection

When style is left as AgentStyle::GeneralPurpose (the default), the system will attempt to detect the user’s intent from their first message and automatically select an appropriate style. To override this behavior, explicitly set the style field.

Fields

style: Option<AgentStyle>

Agent style — determines which base prompt template is used.

When None (default), the style is auto-detected from the user’s message. Explicitly set this to force a particular style regardless of message content.

role: Option<String>

Custom role/identity prepended before the core prompt.

Example: “You are a senior Python developer specializing in FastAPI.” When set, replaces the default “You are A3S Code, an expert AI coding agent” line.

guidelines: Option<String>

Custom coding guidelines appended after the core prompt sections.

Example: “Always use type hints. Follow PEP 8. Prefer dataclasses over dicts.”

response_style: Option<String>

Custom response style that replaces the default “Response Format” section.

When None, the default response format is used.

extra: Option<String>

Freeform extra instructions appended at the very end.

This is the backward-compatible slot: setting system_prompt in the old API maps to this field.

Implementations

impl SystemPromptSlots

pub fn build(&self) -> String

Build the final system prompt by assembling slots around the core prompt.

The core agentic behavior (Core Behaviour, Tool Usage Strategy, Completion Criteria) is always preserved. Users can only customize the edges.

Note: This uses AgentStyle::GeneralPurpose as the base. Use build_with_message() to enable automatic intent-based style detection.

pub fn build_with_message(&self, initial_message: &str) -> String

Build the final system prompt, auto-detecting style from the initial message.

If self.style is explicitly set, that style is used regardless of message content. Otherwise, the style is detected from initial_message using keyword analysis.

pub fn from_legacy(prompt: String) -> Self

Create slots from a legacy full system prompt string.

For backward compatibility: the entire string is placed in the extra slot, and the default core prompt is still prepended.

pub fn is_empty(&self) -> bool

Returns true if all slots are empty (use pure default prompt).

pub fn with_style(self, style: AgentStyle) -> Self

Set the agent style explicitly.

pub fn with_role(self, role: impl Into<String>) -> Self

Set the role/identity.

pub fn with_guidelines(self, guidelines: impl Into<String>) -> Self

Set custom guidelines.

pub fn with_response_style(self, style: impl Into<String>) -> Self

Set custom response style.

pub fn with_extra(self, extra: impl Into<String>) -> Self

Set extra instructions (backward-compatible with old system_prompt).

Trait Implementations

impl Clone for SystemPromptSlots

fn clone(&self) -> SystemPromptSlots

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for SystemPromptSlots

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

Formats the value using the given formatter.

impl Default for SystemPromptSlots

fn default() -> SystemPromptSlots

Returns the “default value” for a type.