# Agent Zero vs Letta (slim)

> Letta scores 59.7 (C) to Agent Zero's 46 (D) for agent harnesses. Prices, MCP, x402, uptime and agent notes side by side.

- Full: https://www.anchorterminal.com/compare/agent-zero-vs-letta.md (~6,350 tokens) · this version ~2,780 tokens · JSON https://www.anchorterminal.com/compare/agent-zero-vs-letta.json · canonical https://www.anchorterminal.com/compare/agent-zero-vs-letta
- 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 Agent Zero's 46 (D), and leads in 4 of 7 scored categories. Agent Zero leads on security & auth and transparency & trust. Both do agent harnesses.

- Agent Zero: D 46, rank #1168 of 1486 · https://www.anchorterminal.com/tools/agent-zero.min.md
- Letta: C 59.7, rank #684 of 1486 · https://www.anchorterminal.com/tools/letta.min.md
- Agent Zero, good for A technical owner who wants an agent with its own Linux machine, reachable from Telegram, WhatsApp or email, with scheduled tasks and editable memory. Ahead on Security & auth, 54 against 35; Transparency & trust, 64 against 55. Also No key needed to call it.
- Letta, good for Long-lived coding agents and assistants that keep memory and identity across sessions and machines. Ahead on Schema & documentation, 70 against 64; Agent ergonomics, 67 against 62; Maintenance & community, 85 against 75. Also Runs on your own machine; No incidents deducted, where Agent Zero loses 15 points for them.

| Category | Agent Zero | Letta |
| --- | --- | --- |
| Reliability (16%) | 57 | 58 |
| Performance (10%) | pending | pending |
| Schema & documentation (13%) | 64 | 70 |
| Agent ergonomics (13%) | 62 | 67 |
| Security & auth (14%) | 54 | 35 |
| Payments & pricing (10%) | 60 | 60 |
| Task success (10%) | pending | pending |
| Maintenance & community (7%) | 75 | 85 |
| Transparency & trust (7%) | 64 | 55 |

| Fact (where they differ) | Agent Zero | Letta |
| --- | --- | --- |
| Vendor | Agent Zero, s.r.o. | Letta |
| Transports |  | stdio |
| Auth | None | OAuth or key |
| Pricing | Free | Freemium |
| Licence | MIT | Apache-2.0 |
| Last release | 2026-11-01 | 2026-11-06 |
| Terms last updated | no document linked | no date given |
| Privacy policy last updated | no document linked | no date given |
| Customer content may train models | not read yet | not found in the text |
| Terms restrict automated access | not read yet | not found in the text |
| Terms restrict benchmarking | not read yet | not found in the text |
| Terms or service can change without notice | not read yet | not found in the text |
| Arbitration or class-action waiver | not read yet | yes |
| Popularity | 19k stars | 3.8k stars, 86k npm/wk, 2.2k PyPI/wk |

Why the edge:
- Security & auth, Agent Zero +19: Agent Zero 54 (Harness reading of the framework checklist, the one the Goose calibration dossier uses. 30 for what leaves the machine by default, 20 for approvals and sandboxing, 15 for prompt-injection posture, 15 for audit and 20 for the security programme. No usage telemetry was found in the source. An update check, on by default, posts the version and a 20-character SHA-256 hash of a random per-install id to api.agent-zero.ai. The Update Checker settings page says only that ID and the version are sent and has an off switch. Something still leaves the machine by default, so the partial is kept (22). The agent works inside a Docker container built on Kali Linux and runs as root there. Tool Access can block tools by project or profile and defaults to allow, host access through the A0 CLI is scoped by read, write and execute permissions, and no approval step was found before a shell command, a file deletion or an outgoing message. The web interface has no login until a username is set (10). Infection Check audits the agent's reasoning with a second model before each tool call and ships disabled. Scanners check plugins, skills and MCP servers before install. The channel allow-lists accept every sender when empty, and the email filter matches the claimed From address only, which the plugin README states (7). Chat logs, visible tool steps and Time Travel snapshots, with no per-call audit log. Per-process log files were removed in v2.5 (9). No SECURITY.md on 4 November, security.txt answered 404 on 12 October, and none of the eight CVEs published from 17 March to 22 October 2026 came from the vendor (VulDB, VulnCheck, MITRE and CISA assigned them). A security-review ledger in the repository records two findings, and the v2.12 notes name both fixes (6, a partial kept).); Letta 35 (Harness reading of the framework checklist, as for the other harnesses. 30 for what leaves the machine by default, 20 for approvals and sandboxing, 15 for injection posture, 15 for audit and 20 for the security programme. Letta Cloud is the default backend, so agent state and conversations go to Letta's servers, and telemetry is on by default (10 of 30). The default permission mode is `unrestricted`; `standard`, `acceptEdits` and `strict` are opt-in, and cloud sandboxes exist for remote work (4 of 20). No prompt-injection guidance found for fetched pages or channel messages (5 of 15). Conversation search and git history of memory give an operator a record of what the agent saw and changed (10 of 15). SECURITY.md routes reports to support@letta.com and scopes out the retired server; no security.txt, bounty or certification found (6 of 20). Total 35.)
- Maintenance & community, Letta +10: Agent Zero 75 (v2.15 was tagged on 1 November 2026, 3 days before this check (30). Seven releases from 6 August, v2.9 on 12 August to v2.15, read from the clone's tags (20). Of the 40 newest open items read on 12 October, 16 are issues and 14 of those have no comment. Three security reports filed as issues were closed as completed, one in five days and two after three months. GitHub's issue pages weren't read on 4 November, so this is per the 12 October check (10 of 25). The Docker image, the desktop Launcher, the install scripts and the A0 CLI connector come from the same organisation, and the v2.14 notes point the README's Launcher links to v1.9 (10 of 15). A Docker publish workflow builds images from tags, and the v2.14 notes raise dependency security floors for aiohttp, anyio, urllib3, filelock, fsspec and multidict. No public test CI (5 of 10). 30 + 20 + 10 + 10 + 5 = 75.); 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.)
- Transparency & trust, Agent Zero +9: Agent Zero 64 (MIT, copyright Agent Zero, s.r.o. (30). No privacy policy for the software was found. The site's cookie notice covers the website, and its terms (14 May 2026) cover the community platform. The docs say where data lives (chats, memory, secrets and settings under `/a0/usr`) and warn that model providers see what is sent to them only in general terms, with no retention statement (8 of 30). Release notes list breaking changes and removals with the release date, and one deprecated alias is named. No deprecation policy or notice period was found (8 of 20, a partial kept). No usage telemetry was found in the source. The update check is described on its settings page, which says it sends only a randomised, hashed install ID and the version number, and the same page turns it off. The ID is a hash of a random per-install token, a pseudonym under this run's reading, so the statement holds (20). 30 + 8 + 8 + 20 = 66.); Letta 55 (Apache-2.0 (30). The privacy policy has no date, no legal entity and no retention periods, and says hosted message data may train future models (8 of 30). The README and docs mark AgentFile, the Electron app and the V1 server as deprecated or retired, without dated notice periods (12 of 20). Telemetry is described in the privacy policy only as basic and opt-out when supported; the LETTA_CODE_TELEM=0 switch appears only in the source (5 of 20). Total 55.)
- Schema & documentation, Letta +6: Agent Zero 64 (Harness reading of the lines, as the Goose calibration dossier does. No OpenAPI file. The connectivity page lists five external endpoints and the `X-API-KEY` header, then sends readers to the source or DeepWiki for request and response details. Each API handler and tool has a `.dox.md` contract file in the repository, and the MCP client JSON shape is documented (10 of 25). llms.txt at www.agent-zero.ai, and AGENTS.md contract files across the repository (10). Guides say which path to use for a need, with tables that separate the browser, the host connector, MCP and A2A (14 of 20). The v2.12 notes say 15 bundled tools gained argument descriptions in non-strict schemas, and plugin settings are typed YAML with commented examples (8 of 15). Guides carry worked examples and a troubleshooting page, with no documented error responses for the external API (9 of 15). Dated notes on every GitHub release and a release article for each version on the site, with no version prefix on API routes (13 of 15).); 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.)
- Agent ergonomics, Letta +5: Agent Zero 62 (Harness reading, scored on what a person or program driving it must supply. Skills load on demand, blocked tools are removed from the prompt, chats can be compacted, and the v2.12 notes report Codex input falling from about 16.4K to 11.3K tokens, a vendor figure (18 of 25). An MCP tool timeout of 120 seconds, a limit of five consecutive unusable responses and context-window handling are set by default. No turn or spend limit was found in the reviewed docs (11 of 20). Other programs reach it through `POST /api_message`, an optional MCP server, A2A and an ACP bridge, with request and response shapes left to the source (11 of 20). An error-retry plugin, saved chats, a message queue, backups and Time Travel snapshots with diff and revert (14 of 20). One Docker command starts it and a wizard sets the model, but there is no SDK and the default has no login (8 of 15).); 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.)