Changelog

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v0.5.0 - 2026-09-01

Changes

v0.4.0 - 2026-05-17

Security

  • Harden Legion.Sandbox.ASTChecker against a class of RCE paths. After this release, most (if not all) RCE vectors should be closed. Legion is still vulnerable to DoS kinds of attacks, but we assume that having a system prompt instruction to behave well AND improving sandbox should be enough for now.

Changes

  • Broaden the sandbox surface for common LLM idioms: allow Map.values/1, JSON, URI, :erlang.float_to_binary/2, additional String/Enum/Date/DateTime functions, and the Access protocol (map[:k])
  • Document the sandbox constraints with concrete idioms in the system prompt
  • Fix tool source extraction breaking on heredocs and charlists
  • Correct documentation for telemetry events, source registry, and AgentTool.start_link/2

v0.3.0 - 2026-04-21

Changes

  • Replace share_bindings boolean with binding_scope (:iteration, :turn, :conversation) for fine-grained control over variable lifetime across code executions
  • Add action_types/0 callback to restrict which actions an agent can use (e.g. ~w(return done) for read-only agents)
  • Add max_message_length config with truncation support to prevent unbounded message growth
  • Add multimedia message support: {:image, data, media_type}, {:image_url, url}, and {:multipart, parts}
  • Add Legion.get_messages/1 to retrieve conversation history from a running agent
  • Expand AgentTool with parallel/2, pipeline/1, then/3, and extra_allowed_modules/0 for sub-agent orchestration; sub-agents are auto-aliased in the sandbox
  • Generate dynamic AgentTool.description/0 from sub-agent moduledocs
  • Move system prompt resolution to AgentPrompt, respecting custom system_prompt/0 overrides
  • Validate config keys at startup with warnings for unknown keys
  • Add @moduledoc compile-time validation via __before_compile__
  • Harden sandbox: block def/defp/__ENV__, additional :erlang functions (process_flag, list_to_atom, system_info), catch throws and exits, surface compiler diagnostics on errors
  • Handle executor exceptions gracefully instead of crashing the agent loop
  • Add Calendar to sandbox safe-module list
  • Emit :exception telemetry events for iteration, LLM, and sandbox spans; use System.convert_time_unit/3 for duration reporting
  • Extensive new test coverage for AgentServer, Executor, Sandbox, and ASTChecker

v0.2.1 - 2026-03-24

  • Improve source code extraction for tool definitions
  • Adjust system prompt to better reflect capabilities

v0.2.0 - 2026-03-15

Changes

  • Simplified and refactored internals
  • Improved documentation and general library intent

v0.1.0 - 2025-12-29

New 🔥

  • Initial release of Legion - an Elixir-native agentic AI framework
  • Legion.AIAgent behaviour for building AI agents with customizable tools and configurations
  • Legion.Tool behaviour for defining tools that agents can use
  • Integration with req_llm for LLM communication
  • Legion.Sandbox for secure code evaluation using Dune
  • Legion.call/2 and Legion.cast/2 for synchronous and asynchronous message passing
  • Legion.start_link/2 for spawning long-lived agents
  • Telemetry events for monitoring and debugging agent execution
  • Support for agent-to-agent communication and delegation