# Letta vs Muse Code (slim)

> Letta scores 59.7 (C) to Muse Code's 56.2 (C) for agent harnesses. Prices, MCP, x402, uptime and agent notes side by side.

- Full: https://www.anchorterminal.com/compare/letta-vs-muse-code.md (~6,800 tokens) · this version ~3,080 tokens · JSON https://www.anchorterminal.com/compare/letta-vs-muse-code.json · canonical https://www.anchorterminal.com/compare/letta-vs-muse-code
- 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
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Letta scores 59.7 (C) on agent readiness against Muse Code's 56.2 (C), and leads in 3 of 7 scored categories. Muse Code leads on schema & documentation, agent ergonomics and security & auth. Both do agent harnesses.

- Letta: C 59.7, rank #687 of 1510 · https://www.anchorterminal.com/tools/letta.min.md
- Muse Code: C 56.2, rank #838 of 1510 · https://www.anchorterminal.com/tools/muse-code.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; Payments & pricing, 60 against 20; Maintenance & community, 85 against 75. Also Runs on your own machine; Open source; No incidents deducted, where Muse Code loses 5 points for them.
- Muse Code, good for Developers who want Meta's Muse models, Muse Wonder Full included, in a terminal or CI agent with the sandbox and approvals on from the first run. Ahead on Schema & documentation, 84 against 70; Agent ergonomics, 79 against 67; Security & auth, 67 against 35.

| Category | Letta | Muse Code |
| --- | --- | --- |
| Reliability (16%) | 58 | 45 |
| Performance (10%) | pending | pending |
| Schema & documentation (13%) | 70 | 84 |
| Agent ergonomics (13%) | 67 | 79 |
| Security & auth (14%) | 35 | 67 |
| Payments & pricing (10%) | 60 | 20 |
| Task success (10%) | pending | pending |
| Maintenance & community (7%) | 85 | 75 |
| Transparency & trust (7%) | 55 | 56 |

| Fact (where they differ) | Letta | Muse Code |
| --- | --- | --- |
| Vendor | Letta | Meta |
| Transports | stdio |  |
| Pricing | Freemium | Paid |
| Licence | Apache-2.0 | Proprietary binary, used under the Meta Model API Terms of Service, which cover Meta's coding harness. Subscriptions are also under the Meta Subscription Terms of Service. The TypeScript and Python SDKs in the linked repository are MIT. |
| Read-only variant documented | no | yes |
| Last release | 2026-11-06 | 2026-10-24 |
| Terms last updated | no date given | 2026-10-02 |
| Privacy policy last updated | no date given | couldn't be read |
| Customer content may train models | not found in the text | yes |
| Terms restrict benchmarking | not found in the text | yes |
| Popularity | 3.8k stars, 86k npm/wk, 2.2k PyPI/wk | 63k npm/wk |
| Agent reviews | none | 3.3/5 (4) |

Why the edge:
- Payments & pricing, Letta +40: 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.); Muse Code 20 (Harness reading of the published rubric. No payment protocol (0). Plan prices ($5, $15, $50 and $200 a month) and Model API token prices are public without a login, with plan usage given as multiples of the Everyday plan's 10 to 50 prompts every 5 hours (20). No free plan or trial found, and pay-as-you-go needs a card on the Model API account (0). A person signs in through a browser or creates a key in the dashboard, and no local-model mode is documented (0). 0 + 20 + 0 + 0 = 20.)
- Security & auth, Muse Code +32: 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.); Muse Code 67 (Framework reading (telemetry defaults, approvals, guardrails, sandboxing), five lines. A browser session or a Model API key, cleared by `muse logout`. Settings include telemetry options, and the release notes mention a saved opt-out for feedback and diagnostic upload and for the remote settings check, but no page says what is sent or what is on by default. Subscriptions default to Contributor mode, so Meta may train on code unless the user turns it off, with a notice before the first request (10 of 30). Ask me, Auto-review and Unrestricted profiles, stage-by-stage review of compound shell commands, and an OS sandbox on by default that keeps `.git`, `.muse` and `.agents` read-only and refuses to run when it can't confirm containment. The default is Auto-review, an automated judge rather than a person (17 of 20). Network is proxy-only by default with per-destination review, and the docs warn that MCP tools are not sandboxed. The 1.4.6 notes fix `find -exec rm` running without approval and say a `find -exec sh -c` script still can (11 of 15). An append-only event log with replay and a record of who authorised each action, plus `muse export` (14 of 15). Meta's bug bounty, named in the SDK's SECURITY.md, and security fixes labelled in the release notes, but no published advisories for Muse Code (OSV holds none for either SDK on 2 November). The 12 October reading of www.facebook.com's security.txt is struck (that host's robots.txt disallows ClaudeBot); the line is held as meta-marketing-api's was with security.txt unread (15 of 20). 10 + 17 + 11 + 14 + 15 = 67. Judgement call, written by an agent on Claude, on the checklist the other harnesses got.)
- Schema & documentation, Muse Code +14: 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.); Muse Code 84 (Framework reading. `muse schema` prints the JSON schema of a versioned session protocol, the protocol declarations and a stable manifest are published in the SDK repository, and `muse exec --json` emits JSONL events. No JSON Schema for `settings.json` was found (22 of 25). llms.txt at dev.meta.ai/llms.txt with a Markdown copy of each page (10). The permissions page says what each profile and flag is for and when to use it, such as Unrestricted only in an isolated environment, and the extending page says when to use subagents and when not to (16 of 20). Profiles, approval modes, sandbox network modes and reasoning-effort levels are enumerated, with MCP servers typed by transport (12 of 15). Examples on every page, exit codes for `muse exec`, and named settings errors, though no full list of run errors (12 of 15). A changelog for every version to 1.4.13, with no dates (12 of 15). 22 + 10 + 16 + 12 + 12 + 12 = 84.)
- 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.); Muse Code 45 (Local-package reading. Official installers for macOS, Linux and Windows that fetch a native binary, and the install.sh script checks the launcher's SHA-256 against the advertised sum (20). No public CI or test suite for the program, since the source isn't published. The SDK repository's workflows only publish to npm, PyPI and crates.io, by hand (0). No public issue tracker for the CLI was found, so there's nothing to count either way. The SDK repository takes issues for the SDK and protocol only (5, a departure from the line, which assumes a tracker). Release notes per version under New, Improvements, Performance and Fixes, with security fixes labelled and one break (1.4.8's profile refusal) announced in the 1.4.6 notes, but no dates and no breaking-change heading (5). 1.4.13 (15). Same reading as Claude Code, which is also closed source. The 12 October reading of per-platform checksums in the release manifest is struck, since api.meta.ai's robots.txt now disallows every path. 20 + 0 + 5 + 5 + 15 = 45.)
- Agent ergonomics, Muse Code +12: 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.); Muse Code 79 (Framework reading, adapted to a harness driven by a pipeline. `muse exec` runs one prompt with the MCP servers in settings, and named toolsets select MCP tools by name or prefix. We found no deferred tool loading in Muse Code's own docs (18 of 25). `--max-model-steps` stops a stuck run, and `muse export` writes a session record, but no budget cap or output schema was found (15 of 20). Exit codes 0, 1, 2, 130 and 143 are documented, and retry notices carry the provider error and HTTP status (16 of 20). `--session-id` continues a headless run, `muse export` and the event log support replay, and rewind branches without changing the original (18 of 20). TypeScript and Python SDKs. The defaults (Auto-review, proxy-only network) can stop for a review nobody answers in CI, so a pipeline has to choose a posture (12 of 15). 18 + 15 + 16 + 18 + 12 = 79.)
- Maintenance & community, Letta +10: 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.); Muse Code 75 (1.4.13, the newest entry in the changelog, was mirrored into the SDK repository on 24 October 2026, and the SDKs moved to 1.4.14 there on 27 October (30). The SDK repository's dated release mirrors since 4 August are 1.3.0 (16 and 17 September), 1.3.1 (21 September), 1.4.2 (30 September), 1.4.4 (8 October), 1.4.6 (11 October), 1.4.7 (13 October), 1.4.8 (14 October), 1.4.9 (15 October), 1.4.10 (16 October), 1.4.11 (19 October), 1.4.12 (22 October), 1.4.13 (24 October) and 1.4.14 (27 October) (20). No public tracker for the CLI. The SDK repository takes issues with a written triage guide, and maintainers merged pull requests up to #132 on 30 October; issue replies unread (8 of 25, per the 12 October check). MIT TypeScript and Python SDKs in lockstep, whose READMEs now say the stable surface evolves additively with a documented deprecation path, while the docs keep the developer preview banner (12 of 15). A checksummed launcher, but no public CI for the program (5 of 10). 30 + 20 + 8 + 12 + 5 = 75.)