Configuration

Mastra Code is configured through project-level files, global settings, and environment variables. Configuration files live in .mastracode/ directories at the project and user levels.

Authentication

Mastra Code authenticates with AI providers through OAuth. Run /login in the TUI to start the flow.

Supported providers

Provider	OAuth flow	What you get
Anthropic	Claude Max subscription	Access to Claude models via your subscription
OpenAI	ChatGPT Plus / Codex	Access to OpenAI models via your subscription

OAuth credentials are stored in auth.json alongside the database in the app data directory.

Model routing

For providers not covered by OAuth, Mastra Code uses Mastra's model router, which auto-detects API keys from environment variables:

export OPENAI_API_KEY=sk-...
export ANTHROPIC_API_KEY=sk-ant-...
export GOOGLE_GENERATIVE_AI_API_KEY=...

MCP servers

Mastra Code can connect to external MCP servers and make their tools available to the agent. Configure servers in JSON files:

Priority	Path	Scope
Highest	.mastracode/mcp.json	Project
	~/.mastracode/mcp.json	Global
Lowest	.claude/settings.local.json	Project (Claude Code compatible)

Project config overrides global config by server name. Claude Code settings are the lowest priority fallback.

MCP config format

.mastracode/mcp.json

{
  "mcpServers": {
    "my-server": {
      "command": "npx",
      "args": ["-y", "@my-org/mcp-server"],
      "env": {
        "API_KEY": "your-key"
      }
    }
  }
}

Each server entry requires a command field. The args and env fields are optional.

On startup, Mastra Code connects to all configured servers and reports the status:

MCP: 2 server(s) connected, 15 tool(s)

Tools from MCP servers are namespaced as serverName_toolName and appear in the agent's tool list alongside built-in tools.

Hooks

Hooks are user-configured shell commands that run at specific lifecycle events. Use hooks for custom validation, logging, notifications, or integration with external systems.

Hook config format

.mastracode/hooks.json

{
  "PreToolUse": [
    {
      "type": "command",
      "command": "node scripts/validate-tool.js",
      "matcher": {
        "tool_name": "execute_command"
      },
      "timeout": 5000,
      "description": "Validate shell commands before execution"
    }
  ],
  "PostToolUse": [
    {
      "type": "command",
      "command": "node scripts/log-tool.js",
      "description": "Log tool usage"
    }
  ]
}

Hook events

Event	When it fires	Can block?
PreToolUse	Before a tool call executes	Yes
PostToolUse	After a tool call completes	No
Stop	When the agent finishes a response	Yes
UserPromptSubmit	When the user sends a message	Yes
SessionStart	When a session begins	No
SessionEnd	When a session ends	No
Notification	When the TUI fires a notification	No

Hook I/O protocol

Hook processes receive a JSON payload on stdin with context about the event:

{
  "session_id": "thread-abc123",
  "cwd": "/path/to/project",
  "hook_event_name": "PreToolUse",
  "tool_name": "execute_command",
  "tool_input": { "command": "npm test" }
}

For blocking events (PreToolUse, Stop, UserPromptSubmit), the hook can respond on stdout with a JSON object:

{
  "decision": "block",
  "reason": "This command is not allowed"
}

Hook config locations

Priority	Path	Scope
Higher	.mastracode/hooks.json	Project (appended after global)
Lower	~/.mastracode/hooks.json	Global (runs first)

Global hooks run before project hooks. For the same event, all hooks execute in order.

Custom slash commands

Define reusable prompt templates as markdown files. Mastra Code scans these directories for .md files:

Priority	Path	Scope
Highest	.mastracode/commands/	Project
	.claude/commands/	Project (Claude Code compatible)
	~/.mastracode/commands/	Global
Lowest	~/.claude/commands/	Global (Claude Code compatible)

Each command file can include YAML frontmatter with name and description fields:

.mastracode/commands/review.md

---
name: review
description: Review the current diff for issues
---
Review my current git diff. Look for bugs, security issues,
and violations of the project's coding standards.

The filename (or directory structure) determines the command name. For example, git/commit.md becomes /git:commit.

Commands support variables like $ARGUMENTS for positional args, @filename for file content injection, and !command for shell command output.

Skills

Skills are structured instruction files that the agent loads automatically based on trigger conditions. They provide domain-specific guidance without manually pasting instructions.

Mastra Code scans these directories for skills:

Priority	Path	Scope
Highest	.mastracode/skills/	Project
	.claude/skills/	Project (Claude Code compatible)
	~/.mastracode/skills/	Global
Lowest	~/.claude/skills/	Global (Claude Code compatible)

Each skill is a directory containing a SKILL.md file with instructions and trigger descriptions. Skills installed via symlinks (e.g., from npx skills add) are automatically resolved.

Agent instructions

Mastra Code loads project-specific instructions from AGENTS.md or CLAUDE.md files and injects them into the agent's system prompt. This is how you can customize the agent's behavior for your project.

Lookup order

For project instructions (first match wins):

1. AGENTS.md or CLAUDE.md in the project root
2. .claude/AGENTS.md or .claude/CLAUDE.md
3. .mastracode/AGENTS.md or .mastracode/CLAUDE.md

For global instructions (first match wins):

1. ~/.claude/AGENTS.md or ~/.claude/CLAUDE.md
2. ~/.mastracode/AGENTS.md or ~/.mastracode/CLAUDE.md
3. ~/.config/claude/AGENTS.md or ~/.config/claude/CLAUDE.md
4. ~/.config/mastracode/AGENTS.md or ~/.config/mastracode/CLAUDE.md

AGENTS.md takes priority over CLAUDE.md when both exist at the same location.

Database

Mastra Code uses LibSQL (SQLite) for persistence. Threads, messages, state, token usage, and observational memory are all stored in the database.

Database location

By default, the database is stored in the platform-specific app data directory:

Platform	Path
macOS	~/Library/Application Support/mastracode/mastra.db
Linux	~/.local/share/mastracode/mastra.db
Windows	%APPDATA%/mastracode/mastra.db

Remote database

Connect to a remote Turso database for cross-device thread sharing:

.mastracode/database.json

{
  "url": "libsql://your-db.turso.io",
  "authToken": "your-auth-token"
}

Database config resolution

Priority	Source
1	MASTRA_DB_URL + MASTRA_DB_AUTH_TOKEN environment variables
2	.mastracode/database.json (project)
3	~/.mastracode/database.json (global)
4	Local file database (default)

Observational memory

Observational memory (OM) uses background agents to maintain a dense log of observations and reflections about the conversation, providing long-term context that persists across sessions.

OM scope

Control whether observations are scoped to individual threads or shared across all threads for a project:

Scope	Behavior
thread (default)	Observations are private to each conversation thread
resource	Observations are shared across all threads for the same project

Configure the scope through:

1. MASTRA_OM_SCOPE environment variable ("thread" or "resource")
2. .mastracode/database.json → omScope field
3. ~/.mastracode/database.json → omScope field

OM model settings

The observer and reflector models default to google/gemini-2.5-flash. Override them per-thread through the /settings panel or in the harness state.

OM thresholds

Threshold	Default	Description
Observation threshold	30,000 tokens	Token count that triggers an observation pass
Reflection threshold	40,000 tokens	Token count that triggers a reflection pass

Environment variables

Variable	Description
MASTRA_DB_URL	LibSQL database URL (e.g., libsql://... or file:./data.db)
MASTRA_DB_AUTH_TOKEN	Auth token for remote LibSQL database
MASTRA_DB_PATH	Override the local database file path
MASTRA_USER_ID	Override the auto-detected user identity
MASTRA_RESOURCE_ID	Override the auto-detected project resource ID
MASTRA_OM_SCOPE	Observational memory scope (thread or resource)
DEFAULT_OM_MODEL_ID	Default model for OM observer and reflector
TAVILY_API_KEY	Enable Tavily-powered web search and extract tools

Resource ID override

Resource IDs determine how threads are grouped. By default, Mastra Code generates one from the Git remote URL or filesystem path. Override it to share threads across repositories or isolate threads within a monorepo:

.mastracode/database.json

{
  "resourceId": "my-custom-project-id"
}

You can also set MASTRA_RESOURCE_ID as an environment variable. Two users who set the same resource ID share threads and observations for that resource.