Glossary¶
Quick reference for all Nexus terminology, acronyms, and technical concepts
A¶
ACE (Agentic Context Engineering)¶
A framework for building self-improving AI agents through structured learning loops. ACE enables agents to learn from experience by recording trajectories, generating reflections, and creating reusable playbooks.
Related: Learning Loops, ACE API
Agent¶
An autonomous AI entity that can perform tasks, make decisions, and interact with the Nexus filesystem. Agents can have their own identity, permissions, and memory.
Related: Agent Permissions
Agent-Tier Skills¶
Personal skills stored in /workspace/.nexus/skills/ that are private to a specific agent or user. These have the highest priority in skill discovery.
Related: Skills System, Skills Management
API Key¶
Authentication credential used to access Nexus in server mode. Format: nxk_... for user keys, nxk_agent_... for agent keys.
Related: Administration & Operations
B¶
Backend¶
Storage layer that handles actual data persistence. Nexus supports multiple backends: local filesystem, S3, GCS, PostgreSQL, Redis, MongoDB.
Related: Mounts & Backends, Multi-Backend Storage
Blob¶
Binary large object - the actual content stored in Nexus, addressed by its SHA-256 hash in the content-addressable storage system.
Related: Content-Addressable Storage
C¶
CAS (Content-Addressable Storage)¶
Storage mechanism where content is identified by its cryptographic hash (SHA-256) rather than location. Enables automatic deduplication and immutable version history.
Related: Content-Addressable Storage
CLI (Command Line Interface)¶
Text-based interface for interacting with Nexus. Commands start with nexus (e.g., nexus read, nexus write).
Related: CLI Reference
Consolidation¶
Process of merging and compressing memory entries to optimize storage and improve retrieval. Can be done synchronously or asynchronously.
Related: Memory Consolidation
D¶
Default Context¶
Automatically set tenant, namespace, and user context for operations. Simplifies API calls by not requiring explicit context parameters.
Related: Configuration
E¶
Embedded Mode¶
Deployment mode where Nexus runs directly within your application process. No separate server required, no authentication needed. Best for development and single-user scenarios.
Related: Deployment Modes
F¶
Feedback¶
User or system input about agent behavior, stored for learning and improvement. Part of the ACE learning loop.
Related: Learning Loops
FUSE (Filesystem in Userspace)¶
Technology that allows mounting Nexus as a regular filesystem directory on Linux/macOS, enabling traditional file operations.
Related: FUSE Mounts
G¶
Group¶
Collection of users or agents that can be granted permissions collectively. Supports hierarchical relationships.
Related: Team Collaboration
H¶
Hook¶
Plugin lifecycle method that intercepts operations. Types: pre_read, post_read, pre_write, post_write, pre_delete, post_delete, on_mount, on_unmount, on_startup, on_shutdown.
Related: Plugin Hooks, Building Plugins
I¶
Identity¶
The authenticated entity (user or agent) performing operations. Determines permissions and memory namespace.
Related: Agent Permissions
L¶
Learning Loop¶
Iterative process where agents record experiences (trajectories), reflect on outcomes, and generate reusable patterns (playbooks).
Related: Learning Loops, ACE
LLM Document Reading¶
Feature that allows querying documents using natural language via LLMs, with citation support showing source locations.
Related: LLM Document Reading
M¶
MCP (Model Context Protocol)¶
Protocol for providing context to AI models. Nexus can serve as an MCP server, exposing filesystem operations to AI assistants.
Related: MCP Integration, MCP Server CLI
Memory¶
Persistent storage of agent knowledge and context. Organized hierarchically: agent > session > namespace.
Related: Memory System, Memory Management
Metadata¶
Structured information about files including size, timestamps, permissions, content type, custom attributes, and version history.
Related: Metadata API
Mount¶
Virtual mapping of a backend storage system to a path in the Nexus filesystem. Enables federation across multiple storage backends.
Related: Mounts, Mounts & Backends
Multi-Tenancy¶
Architecture supporting multiple isolated customer environments (tenants) within a single Nexus deployment.
Related: Multi-Tenancy, Multi-Tenant SaaS
N¶
Namespace¶
Logical container for organizing data and memory. Provides isolation boundary for multi-tenancy.
Related: Multi-Tenancy
O¶
Object¶
Generic term for any entity in Nexus that can have permissions: files, directories, namespaces, groups, workflows, skills.
Related: ReBAC Explained
P¶
Parser¶
Plugin component that processes specific file types (e.g., YAML, JSON, images) and extracts metadata or transforms content.
Related: Building Plugins
Playbook¶
Reusable pattern or template generated from successful agent trajectories. Stored in memory for future reference.
Related: Playbook Management
Plugin¶
Extension that adds custom functionality to Nexus via lifecycle hooks, parsers, or event handlers.
Related: Plugin System, Building Plugins
R¶
ReBAC (Relationship-Based Access Control)¶
Permission system based on relationships between subjects and objects. Inspired by Google Zanzibar. More flexible than traditional ACLs or RBAC.
Related: ReBAC Explained, Permissions API
Reflection¶
Analysis of agent trajectory to extract learnings, identify patterns, and generate playbooks. Part of ACE learning loop.
Related: Learning Loops
Remote Mode¶
See Server Mode.
S¶
Sandbox¶
Isolated execution environment for running untrusted code safely. Supports Docker and E2B backends.
Related: Sandbox Management, Sandbox CLI
SDK (Software Development Kit)¶
Python library for interacting with Nexus programmatically. Install with pip install nexus-ai-fs.
Related: Getting Started
Semantic Search¶
Search capability that finds content by meaning rather than exact keyword matching. Uses vector embeddings.
Related: Semantic Search
Server Mode¶
Deployment mode where Nexus runs as a standalone server with authentication, multi-user support, and remote access.
Related: Deployment Modes, Server Setup
Session¶
Temporary context for a group of related operations. Sessions can have their own memory namespace.
Related: Workspace Management
SHA-256¶
Cryptographic hash function used to generate content addresses in CAS. Produces 256-bit (32-byte) hash values.
Related: Content-Addressable Storage
Skill¶
Reusable AI capability packaged as a Markdown file with YAML frontmatter. Can be discovered and shared across agents.
Related: Skills System, Skills Management
Skill Seekers¶
Plugin that auto-generates skills from documentation URLs using AI enhancement.
Related: Skill Seekers Plugin
Subject¶
Entity that can perform actions: user, agent, or group. The "who" in permission tuples.
Related: ReBAC Explained
System-Tier Skills¶
Global skills stored in /system/skills/ that are available to all users and agents. Lowest priority in skill discovery.
Related: Skills System
T¶
Tenant¶
Isolated customer environment in a multi-tenant deployment. Has its own namespace, users, and data.
Related: Multi-Tenancy
Tenant-Tier Skills¶
Organization-wide skills stored in /shared/skills/ that are available to all members of a tenant.
Related: Skills System
Trajectory¶
Recorded sequence of agent actions, observations, and outcomes. Used for learning and reflection in ACE.
Related: Trajectory Tracking
Trigger¶
Deprecated term. See Workflow.
Related: Workflows vs Triggers
Tuple¶
Permission relationship expressed as (subject, relation, object). Example: (user:alice, can_read, file:/docs/report.pdf).
Related: ReBAC Explained
V¶
Version¶
Immutable snapshot of a file at a specific point in time. Nexus maintains complete version history using CAS.
Related: Versioning API
VFS (Virtual File System)¶
Unified interface that abstracts multiple backend storage systems, presenting them as a single filesystem hierarchy.
Related: What is Nexus?
W¶
Workflow¶
Event-driven automation that executes when files matching specific patterns are created or modified. Replaces the older "trigger" terminology.
Related: Workflows, Workflows vs Triggers, Workflow Automation
Workspace¶
Root directory for user or agent operations. Typically mounted at /workspace/.
Related: Workspace Management
Z¶
Zanzibar¶
Google's relationship-based authorization system that inspired Nexus ReBAC implementation.
Related: ReBAC Explained
Common Abbreviations¶
| Abbreviation | Full Term | Description |
|---|---|---|
| ACE | Agentic Context Engineering | Learning framework for AI agents |
| API | Application Programming Interface | Programmatic interface for Nexus |
| CAS | Content-Addressable Storage | Hash-based storage system |
| CLI | Command Line Interface | Text-based command interface |
| FUSE | Filesystem in Userspace | Mount Nexus as regular filesystem |
| GCS | Google Cloud Storage | Cloud storage backend |
| LLM | Large Language Model | AI model for text processing |
| MCP | Model Context Protocol | AI context protocol |
| POSIX | Portable Operating System Interface | Unix-like filesystem API standard |
| ReBAC | Relationship-Based Access Control | Permission system |
| S3 | Simple Storage Service | AWS object storage |
| SDK | Software Development Kit | Python library for Nexus |
| VFS | Virtual File System | Unified filesystem abstraction |
| YAML | YAML Ain't Markup Language | Human-readable data format |
Quick Reference: File Path Conventions¶
| Path | Purpose | Example |
|---|---|---|
/workspace/ | User/agent working directory | /workspace/my-project/ |
/shared/ | Tenant-wide shared resources | /shared/docs/ |
/system/ | System-wide global resources | /system/skills/ |
/.nexus/ | Nexus metadata and configuration | /workspace/.nexus/skills/ |
/db/ | Database mount point | /db/public/users |
Quick Reference: Permission Relations¶
| Relation | Description | Example Use Case |
|---|---|---|
can_read | Read access to object | View file contents |
can_write | Write/modify access | Edit files, create subdirectories |
can_delete | Delete access | Remove files or directories |
can_execute | Execute access | Run scripts or workflows |
admin | Full administrative access | Manage users, configure system |
member | Group membership | User belongs to team |
owner | Ownership relationship | Creator of resource |
parent | Hierarchical relationship | Directory contains file |
Quick Reference: CLI Commands¶
| Command | Description | Example |
|---|---|---|
nexus read | Read file contents | nexus read /workspace/file.txt |
nexus write | Write file contents | nexus write /workspace/file.txt "content" |
nexus ls | List directory | nexus ls /workspace/ |
nexus mkdir | Create directory | nexus mkdir /workspace/new-dir |
nexus rm | Remove file | nexus rm /workspace/old-file.txt |
nexus cat | Display file contents | nexus cat /workspace/file.txt |
nexus serve | Start server | nexus serve --port 2026 |
nexus memory | Memory operations | nexus memory store "key" "value" |
nexus rebac | Permission management | nexus rebac create --subject user:alice --relation can_read --object file:/docs |
nexus skills | Skill management | nexus skills list |
nexus admin | Admin operations | nexus admin create-user alice |
See Also¶
- Core Concepts - Understand how Nexus works
- Getting Started - Begin using Nexus
- API Reference - Complete API documentation
- Learning Paths - Step-by-step tutorials
Need to add a term? Contribute to this glossary on GitHub.