Letta vs Unstoppable

Letta 67

Harness reading. Toolsets switch with /model, skills load per agent, and subagents run in the background (18 of 25). Context is managed through memory blocks, reflection and dreaming (12 of 20). letta -p --output-format json for scripted runs and an App Server for programmatic control (12 of 20). Conversations resume by agent and conversation id, and memory is git-tracked so changes can be reverted (15 of 20). Runs with no account on the local backend, with one SDK language, TypeScript (10 of 15). Total 67.

Unstoppable 5

These lines measure an interface an agent calls, and Unstoppable has none, so context cost, output controls and retries score nothing. For the person, a usage limit shows choices to wait for the reset or continue on credits (2 of 20). Guest use with no account, a first-run page that imports Claude and Codex projects, and few required settings. No SDK (3 of 15). Total 5.

Letta 70

Harness reading. docs.letta.com serves llms.txt and a Markdown version of every page, with an applies_to block saying which backend and interface each page covers (10). TypeScript types for the Agent SDK and a documented App Server WebSocket protocol, but no JSON Schema or OpenAPI for the harness (15 of 25). Pages say when to use local or cloud backends, subagents and channels (14 of 20). Permission modes and options are typed in the SDK (12 of 15). Example applications and a remote client reference (11 of 15). Releases most days but no changelog file (8 of 15). Total 70.

Unstoppable 30

Graded on the interface an outside agent can use, which is none. No API, OpenAPI file, MCP server or documented command (0). unstoppable.ai/llms.txt lists the product, help and policy pages in Markdown (10). Twenty-two dated help articles explain for a person what each part does and when to use it, such as Code and Work modes and approval modes (5 of 20). No typed inputs an agent could call (0). Step-by-step examples for people and named error states such as usage limit reached and update failed, with no error responses for an agent (3 of 15). Numbered versions and a public dated changelog, which lists only four releases from 20 to 23 October 2026 (12 of 15). Total 30.

Letta 60

No x402, MPP or L402 (0 of 40). Per-unit API prices are public, $0.10 per active agent a month and $0.00015 a second of tool execution, plus plan prices (20). A $0 plan with bring-your-own keys; no card is mentioned (20). The CLI runs locally without signing in (20). Total 60.

Unstoppable 30

No x402, MPP or L402 (0). The app is published as free, but AI credit prices appear only after sign-in, and no pricing page exists (unstoppable.ai/pricing redirects to the home page). Plan prices of $19, $29 and $49 appear only in an 11 August 2026 blog post (10). Guest use with no account, and 10 free AI credits a day with no card (20). A person has to download and install the app, so no autonomous onboarding (0). Total 30.

Letta 85

v0.34.42 on 6 November 2026 (30). Dozens of releases in 90 days (20). Pull requests are merged daily; recent issues from users have few replies (15 of 25). npm and PyPI packages and the Agent SDK track the releases (12 of 15). Lock files, CI and nightly smoke tests (8 of 10). Total 85.

Unstoppable 58

Read for a closed product. Version 1.15.0 on 23 October 2026, and iOS 1.1.9 on 27 October (30). Four desktop releases from 20 to 23 October and nine iOS updates since 11 August 2026 (20). A public changelog, a support email, in-app feedback and a Discord server, none tested for replies. Help articles were updated between 19 and 24 October (6 of 15). No SDK and no MCP registry entry (0). Windows updates check signatures per the 1.13.0 notes, with no build pipeline to inspect (2 of 10). Total 58.

Letta 58

Local-software lines, read for the harness. @letta-ai/letta-code on npm with Node.js 22.19 or newer, and PyPI wheels for glibc Linux, macOS 14 and Windows x64 with Python 3.9 or newer stated (20). ci.yml, nightly update smoke tests and Telegram live smoke tests exist, but GitHub's API answered with a rate limit, so run results were unread (15 of 25, unchecked). 332 open issues and pull requests, mostly pull requests; recent bug reports such as recall reading the wrong conversation have no reply yet (15 of 25). 398 tags at 0.34.x with release notes on GitHub, no changelog file, and breaking removals such as AgentFile announced in the README (8 of 15). Pre-1.0 (0). Total 58.

Unstoppable 45

Read as local software, because the product is the desktop app the owner runs, as for the other harnesses. Signed downloads for macOS Apple Silicon, macOS Intel and Windows on the download page, version 1.15.0, plus iOS and Android apps in the stores, with the supported platforms stated. No package registry (20). Closed source with no public CI or test suite (0). No public issue tracker. Bugs go through in-app feedback, email and Discord, none of which shows a record we could read (0). Version numbers and a dated changelog, but only 1.12.0 to 1.15.0 are listed and breaking changes are not marked as such (10). Version 1.15.0 (15). The hosted parts (accounts, AI credits, cloud agents, Remote Control) have no status page. status.unstoppabledomains.com covers the domains business only.