Leash SDK for Ruby

Server-side Ruby SDK for the Leash platform. One client gives you:

the authenticated user off the request
runtime env-var resolution from the Leash secret-source registry
typed integrations (Gmail, Google Calendar, Google Drive, Linear)
a generic escape hatch for any provider on the platform

Framework-agnostic: works with Rails, Sinatra, Hanami, or plain Rack — no framework gems required.

Installation

Add to your Gemfile:

gem "leash-sdk"

…or install directly:

gem install leash-sdk

Requires Ruby >= 2.7 (Ruby 3.0+ recommended — 2.7 is EOL since 2023-03; system macOS Ruby 2.6.x is below the floor and will need a newer Ruby via rbenv/asdf/homebrew). The only runtime dependency is jwt.

Setup

Set the platform API key in your environment:

export LEASH_API_KEY=lsk_live_...

The constructor reads LEASH_API_KEY automatically; you can also pass api_key: explicitly.

Usage

Rails

# app/controllers/inbox_controller.rb
class InboxController < ApplicationController
  def index
    leash = Leash.new(request: request)

    if leash.auth.authenticated?
      @user = leash.auth.user                           # Leash::User or nil
      @messages = leash.integrations.gmail.list_messages(max_results: 10)
    else
      redirect_to "/login"
    end
  end
end

Sinatra

require "sinatra"
require "leash"

get "/me" do
  leash = Leash.new(request: request)
  user = leash.auth.user
  halt 401 unless user
  user.to_h.to_json
end

Plain Rack

class MyApp
  def call(env)
    leash = Leash.new(request: env)        # Rack `env` hash works directly
    secret = leash.env.get("OPENAI_API_KEY")
    [200, {}, [secret ? "ok" : "missing"]]
  end
end

What you get

`leash.auth`

user = leash.auth.user                     # Leash::User or nil — never raises
leash.auth.authenticated?                  # Boolean

`leash.env`

key = leash.env.get("OPENAI_API_KEY")      # String or nil (nil = not declared)
fresh = leash.env.get("STRIPE_KEY", fresh: true)
many = leash.env.get_many(["A", "B"])      # { "A" => "...", "B" => nil }

Per-instance TTL cache: 60 seconds. Pass fresh: true to bypass the cache for one read.

`leash.integrations`

Typed providers:

# Gmail
leash.integrations.gmail.list_messages(max_results: 5)
leash.integrations.gmail.get_message("msg-id")
leash.integrations.gmail.send_message(to: "a@b.com", subject: "Hi", body: "Hello")
leash.integrations.gmail.search_messages("from:x@y.com")
leash.integrations.gmail.list_labels
leash.integrations.gmail.get_profile

# Google Calendar (also addressable as leash.integrations.google_calendar)
leash.integrations.calendar.list_calendars
leash.integrations.calendar.list_events(time_min: "2026-01-01T00:00:00Z")
leash.integrations.calendar.create_event(
  summary: "Standup",
  start: { "dateTime" => "2026-05-15T10:00:00Z" },
  end_time: { "dateTime" => "2026-05-15T10:30:00Z" }
)
leash.integrations.calendar.get_event("evt-1")

# Google Drive (also addressable as leash.integrations.google_drive)
leash.integrations.drive.list_files(query: "name contains 'q'")
leash.integrations.drive.get_file("file-id")
leash.integrations.drive.download_file("file-id")
leash.integrations.drive.create_folder("Receipts", parent_id: "p-1")
leash.integrations.drive.upload_file(name: "x.txt", content: "data", mime_type: "text/plain")
leash.integrations.drive.delete_file("file-id")
leash.integrations.drive.search_files("invoice")

# Linear
leash.integrations.linear.list_issues(state_type: "started")
leash.integrations.linear.get_issue("LEA-123")
leash.integrations.linear.create_issue(team_id: "t-1", title: "Build it")
leash.integrations.linear.update_issue("LEA-123", priority: 1)
leash.integrations.linear.add_comment("LEA-123", "ship it")
leash.integrations.linear.list_teams
leash.integrations.linear.list_projects

Generic escape hatch for any platform-registered provider (Slack, GitHub, HubSpot, Jira, …):

leash.integrations.provider("slack").call("post_message",
                                            body: { "channel" => "#general", "text" => "hi" })

Errors

Every call raises a Leash::Error (or one of its subclasses) on failure:

Class	Raised when
`Leash::UnauthorizedError`	platform returned 401 (missing/invalid creds)
`Leash::ConnectionRequiredError`	403 (provider not connected for this user)
`Leash::UpgradeRequiredError`	402 (feature gated behind a higher plan)
`Leash::KeyNotDeclaredError`	manually raised for env mis-declarations
`Leash::NetworkError`	transport-level failures (DNS, refused, timeout)
`Leash::Error`	base class — also raised for generic 4xx/5xx

Every error carries code, message, action, see_also, status, and (where present) connect_url.

For convenience, the 0.3 aliases Leash::NotConnectedError and Leash::PlanBlockError are still available.

Authentication precedence

The constructor inspects the request in this order:

LEASH_API_KEY env var (or explicit api_key: constructor arg) — server-only, never request-bound.
Authorization: Bearer <jwt> header on the request — used by auth.user and as an env-read fallback when no API key is present. Never forwarded on integration POSTs.
leash-auth cookie on the request — the standard browser → deployed-app session.

The Bearer-token → env fallback is intentional so CLI/agent flows can read env-vars with a user JWT when no app key is provisioned. The same JWT is never sent on integration POSTs because the platform's verifyToken() rejects it before the API-key check runs, producing a misleading 401.

What's NOT in 0.4 yet

create_dev_auth_handler / attach_local_dev_handler — there's no Rack-side equivalent shipped in 0.4. (The TS SDK has a Leash.createDevAuthHandler for Next.js routes.) If you need a Ruby local-dev cookie-exchange flow, open an issue.
Legacy LeashIntegrations class — the 0.3 Leash::Integrations.new(auth_token: ..., api_key: ...) constructor and its gmail / calendar / drive accessors have been replaced by Leash.new(request: ...) + the namespaced .integrations accessor. The TS SDK dropped the equivalent class in 0.4 too.
Browser-mode usage — server-only in 0.4.

If you're upgrading from 0.3.x, the Leash::Auth.get_user(request) helper and the Leash::User / Leash::Error / Leash::NotConnectedError / Leash::TokenExpiredError classes are kept for backwards compatibility.

Testing

bundle install
bundle exec rake test

License

Apache 2.0.

leash-sdk

Development

Runtime