larva 0.4.1

PersonaSpec toolkit for LLM agents

larva

PersonaSpec toolkit for LLM agents. Validate, assemble, normalize, register, and resolve canonical persona specifications.

What larva Does

larva manages PersonaSpec — structured JSON definitions for AI agent personas. It provides:

• Validate — schema + semantic checks on PersonaSpec JSON
• Assemble — compose personas from reusable components (prompts, toolsets, constraints, models)
• Register / Resolve — store and retrieve personas from a global registry (~/.larva/)
• Clone / Update / Delete — full lifecycle management
• Export — bulk export for integrations
• MCP server — programmatic access for other tools

Install

pip install larva

Quick Start

# Register a persona
cat <<'EOF' > my-agent.json
{
  "spec_version": "0.1.0",
  "id": "code-reviewer",
  "description": "Reviews code for correctness and style",
  "prompt": "You are a senior code reviewer...",
  "model": "openai/gpt-5.4",
  "can_spawn": false,
  "side_effect_policy": "read_only"
}
EOF

larva validate my-agent.json
larva register my-agent.json
larva resolve code-reviewer

# List all personas
larva list

# Clone and experiment
larva clone code-reviewer code-reviewer-exp
larva update code-reviewer-exp --set model=openai/gpt-5.4-pro

# Export all
larva export --all --json

Interfaces

MCP Server (primary)

larva.validate(spec)              → ValidationReport
larva.assemble(components)        → PersonaSpec
larva.register(spec)              → {id, registered}
larva.resolve(id, overrides?)     → PersonaSpec
larva.list()                      → [{id, spec_digest, model}]
larva.update(id, patches)         → PersonaSpec
larva.clone(source_id, new_id)    → PersonaSpec
larva.delete(id)                  → {id, deleted}
larva.clear(confirm)              → {cleared, count}
larva.export(all?, ids?)          → [PersonaSpec, ...]
larva.component_list()            → {prompts, toolsets, constraints, models}
larva.component_show(type, name)  → component content

CLI

larva validate <spec.json> [--json]
larva register <spec.json> [--json]
larva resolve <id> [--override key=value]... [--json]
larva list [--json]
larva update <id> --set key=value [--set ...]  [--json]
larva clone <source-id> <new-id> [--json]
larva delete <id> [--json]
larva clear --confirm "CLEAR REGISTRY" [--json]
larva export --all [--json]
larva export --id <id> [--id <id>]... [--json]
larva assemble --id <id> [--prompt <name>]... [--toolset <name>]... [--constraints <name>]... [--model <name>] [--override key=value]... [--var key=value]... [-o output.json]
larva component list [--json]
larva component show <type>/<name> [--json]

Python Library

from larva.shell.python_api import (
    validate, assemble, register, resolve, list,
    update, clone, delete, clear,
    export_all, export_ids,
    component_list, component_show,
)

# Register
result = validate({"id": "my-agent", "spec_version": "0.1.0", "prompt": "..."})
register({"id": "my-agent", "spec_version": "0.1.0", "prompt": "..."})

# Resolve
spec = resolve("my-agent")

# Clone + update
clone("my-agent", "my-agent-exp")
updated = update("my-agent-exp", {"model": "openai/gpt-5.4-pro"})

# Export all
all_specs = export_all()

Component Library

~/.larva/
  components/
    prompts/           # Prompt text fragments (.md files)
    toolsets/           # Tool permission maps (.yaml)
    constraints/        # can_spawn + side_effect_policy (.yaml)
    models/             # Model + inference params (.yaml)
  registry/             # Registered PersonaSpec JSON files

# Assemble from components
larva assemble --id code-reviewer \
  --prompt code-reviewer --prompt careful-reasoning \
  --toolset read-only \
  --constraints strict \
  --model claude-opus

# Browse components
larva component list
larva component show prompts/code-reviewer

Web UI

A browser-based persona manager is included in contrib/web/:

pip install fastapi uvicorn
python contrib/web/server.py
# → opens http://localhost:7400

OpenCode Plugin

An OpenCode plugin that registers larva personas as agents:

// .opencode/opencode.json
{
  "plugin": ["file:///path/to/larva/contrib/opencode-plugin/larva.ts"]
}

See contrib/opencode-plugin/README.md for details.

Architecture

larva follows a strict layered architecture enforced by Invar:

Layer	Path	Rules
Core	src/larva/core/	Pure logic, @pre/@post contracts, no I/O
Shell	src/larva/shell/	I/O adapters, returns Result[T, E]
App	src/larva/app/	Orchestration facade

Key Design Decisions

• Composition, not inheritance. No base: field. Components are orthogonal building blocks.
• Error-on-conflict. Two components setting the same scalar field → assembly fails. Use overrides.
• Authority, not runtime. larva owns persona definitions; execution belongs elsewhere.
• No cross-run mutable state. Persona changes require explicit register.

License

AGPL-3.0-or-later