Crate echo_core 

echo-core

Core traits, types, and error definitions for the echo-agent framework.

This crate provides the shared interfaces that all other workspace crates build on:

Module	Contents
agent	Agent trait, AgentEvent, AgentCallback, CancellationToken
llm	LlmClient trait, ChatRequest/ChatResponse/ChatChunk types
tools	Tool trait, ToolResult, ToolPermission, permission model
error	Unified Error enum covering all failure modes
guard	Guard trait, GuardResult, GuardManager
audit	AuditEvent, AuditLogger trait
retry	RetryPolicy with exponential backoff
tokenizer	Token counting interface

Most users should depend on echo_agent (the facade crate) instead of depending on echo_core directly.

Modules

agent

Agent core trait, events, and callback interfaces

audit

Audit logging core trait and event types

circuit_breaker

LLM Circuit Breaker

error

Unified error types

guard

Guard system core trait and types

llm

LLM client core trait and request/response types

project_rules

Project-level rules file loading

retry

Unified retry policy

tokenizer

Token estimation trait, usage tracking, and cost estimation

tools

Tool system core trait and types