# Letta vs Unstoppable (slim)

> Letta scores 59.7 (C) to Unstoppable's 34.7 (F) for agent harnesses. Prices, MCP, x402, uptime and agent notes side by side.

- Full: https://www.anchorterminal.com/compare/letta-vs-unstoppable.md (~5,750 tokens) · this version ~1,930 tokens · JSON https://www.anchorterminal.com/compare/letta-vs-unstoppable.json · canonical https://www.anchorterminal.com/compare/letta-vs-unstoppable
- Index: https://www.anchorterminal.com/llms.txt · API: https://www.anchorterminal.com/api/v1/index.json · MCP: https://www.anchorterminal.com/mcp · Updated: 2026-11-07
- Licence: CC BY 4.0, credit Anchor Terminal and link this page (https://www.anchorterminal.com/terms/#data)

Letta scores 59.7 (C) on agent readiness against Unstoppable's 34.7 (F), and leads in 5 of 7 scored categories. Both do agent harnesses.

- Letta: C 59.7, rank #687 of 1510 · https://www.anchorterminal.com/tools/letta.min.md
- Unstoppable: F 34.7, rank #1400 of 1510 · https://www.anchorterminal.com/tools/unstoppable.min.md
- Letta, good for Long-lived coding agents and assistants that keep memory and identity across sessions and machines. Ahead on Reliability, 58 against 45; Schema & documentation, 70 against 30; Agent ergonomics, 67 against 5; Payments & pricing, 60 against 30; Maintenance & community, 85 against 58. Also Runs on your own machine; Open source.
- Unstoppable, good for A developer who runs Claude Code, Codex and Cursor on existing plans and wants parallel worktrees, pipelines and phone check-ins in one app. Also No key needed to call it; Free to start without a card.

| Category | Letta | Unstoppable |
| --- | --- | --- |
| Reliability (16%) | 58 | 45 |
| Performance (10%) | pending | pending |
| Schema & documentation (13%) | 70 | 30 |
| Agent ergonomics (13%) | 67 | 5 |
| Security & auth (14%) | 35 | 36 |
| Payments & pricing (10%) | 60 | 30 |
| Task success (10%) | pending | pending |
| Maintenance & community (7%) | 85 | 58 |
| Transparency & trust (7%) | 55 | 56 |

| Fact (where they differ) | Letta | Unstoppable |
| --- | --- | --- |
| Vendor | Letta | Unstoppable Domains, Inc. |
| Transports | stdio |  |
| Auth | OAuth or key | None |
| Licence | Apache-2.0 | Proprietary, under Unstoppable Domains, Inc.'s Terms of Service. No source published |
| Last release | 2026-11-06 | 2026-10-23 |
| Terms last updated | no date given | 2026-10-06 |
| Privacy policy last updated | no date given | 2026-10-08 |
| Terms restrict benchmarking | not found in the text | yes |
| Popularity | 3.8k stars, 86k npm/wk, 2.2k PyPI/wk | none |

Why the edge:
- Agent ergonomics, Letta +62: 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.)
- Schema & documentation, Letta +40: 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.)
- Payments & pricing, Letta +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.)
- Maintenance & community, Letta +27: 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.)
- Reliability, Letta +13: 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.)