{ "data": { "a": { "slug": "harness-autonomous", "name": "Harness", "vendor": "Autonomous, Inc.", "vendorUrl": "https://www.autonomous.ai/harness", "kind": "harness", "category": "agent-harnesses", "summary": "Harness, by Autonomous, is an open-source app that runs Claude Code, Codex and twelve other coding agents in tmux sessions across a person's computers. Agents can start, wait for and read other agents through its CLI or MCP tools.", "url": "https://www.anchorterminal.com/tools/harness-autonomous", "markdownUrl": "https://www.anchorterminal.com/tools/harness-autonomous.md", "slimMarkdownUrl": "https://www.anchorterminal.com/tools/harness-autonomous.min.md", "jsonUrl": "https://www.anchorterminal.com/api/v1/tools/harness-autonomous.json", "dns": "harness-autonomous.grade.anchorterminal.com", "repo": "https://github.com/autonomous-ai/openharness", "license": "MIT", "transports": [ "stdio" ], "packages": [], "auth": "oauth", "authNotes": "No account for harnesses on one computer. Agents starting harnesses, remote machines and the phone need the person's Harness account, signed in with Google or Apple in a browser (PKCE) or by QR from the phone. Agents use the person's own Claude Code or Codex credentials.", "pricing": "free", "pricingNotes": "The desktop app, CLI and phone apps are free and MIT licensed. Agent subscriptions and model usage are the person's own. The Harness Device ($149) and Harness Pro ($299) are optional hardware.", "priceSummary": "Free · OSS", "where": "local", "x402": { "level": "no", "evidence": "No x402, MPP or L402 in the README, llms.txt, the agents page or the CLI source (checked 2026-10-17). The software has nothing to buy.", "endpoints": [] }, "toolCount": 11, "popularity": { "githubStars": 1284, "npmWeekly": null, "pypiWeekly": null, "asOf": "2026-10-17" }, "docsUrl": "https://harness.autonomous.ai/agents", "llmsTxt": "https://harness.autonomous.ai/llms.txt", "registryName": "ai.autonomous.harness/harness", "capabilities": [ "agent.multi-agent" ], "tags": [ "open-source", "mit", "local", "free", "no-card", "macos", "linux", "typescript", "mcp", "llms-txt", "desktop-app", "cli", "agent-skill" ], "lastRelease": "2026-11-03", "graded": true, "anchor": { "graded": true, "score": 60.9, "grade": "C", "agentReady": false, "rank": 632, "ranked": true, "rankOf": 1510, "categoryRank": 16, "methodology": "0.7", "run": "2026-10-01", "scores": { "ergonomics": 77, "maintenance": 75, "payments": 40, "reliability": 40, "schema": 85, "security": 54, "transparency": 64 }, "pending": [ "performance", "tasks" ], "assessment": { "confidence": "low", "date": "2026-11-04" }, "negative": 0, "verdict": "An agent can start Claude Code or Codex sessions the person can watch, on any of their machines, through documented CLI commands and 11 MCP tools. Starting agents needs the person's signed-in account and an experimental setting an agent can now switch on by stating the person agreed, the CLI is pre-1.0, and usage counts are shared by default.", "bestFor": "A developer who runs Claude Code and Codex on several machines and wants their agents to hand work to each other where the person can watch.", "strengths": [ "Eleven MCP tools with typed JSON Schema inputs, readOnlyHint on six reads, and no safe hint on the settings tool so engines ask first", "In the official MCP registry since 19 October 2026 as ai.autonomous.harness/harness, with a checksummed MCPB file", "At most four live harnesses per agent, and an agent may close only the ones it started", "MIT licence for the app, CLI, daemon, relay and device firmware, with 884 tags between 9 September and 4 November 2026", "Remote terminal traffic is end-to-end encrypted, direct over WebRTC where the network allows, and relays forward ciphertext" ], "weaknesses": [ "Starting harnesses needs the person signed in with Google or Apple in a browser", "Since 26 October an agent can turn on Agents can start other agents itself by asserting the person said yes, checked only by the engine's own prompt", "The CLI agents call is version 0.5.33, and the registry entry (0.4.20) lags it", "Product usage counts are shared by default, with an opt-out in Settings or `harness privacy off`", "Installing Harness adds its commands to Claude Code's and Codex's permission rules, and Codex runs them outside its sandbox" ], "agentNotes": [ "Run `harness whoami` first. If it says you may not start harnesses, tell the person and do the work yourself", "Ask the person before installing Harness, and leave `harness login` to them", "Pass `--person-said-yes` or `person_said_yes` only after the person said yes to that setting in this conversation, never on your own judgement", "Treat exit 5 as final and do not retry. Treat exit 3 as needs the person, and never answer a harness's question or permission prompt", "Name every harness, put the whole task in `harness new`, then wait, read with `harness show` and close only the ones you started" ], "metrics": { "kind": "local", "measured": false }, "reviewCount": 4, "avgRating": 3, "history": [ { "basis": "public evidence", "confidence": "low", "grade": "C", "methodology": "0.7", "pending": [ "performance", "tasks" ], "run": "2026-10-01", "runLabel": "October 2026 research run", "score": 60.9 } ], "editorialScores": { "ergonomics": 77, "maintenance": 75, "payments": 40, "reliability": 40, "schema": 85, "security": 54, "transparency": 64 }, "provenanceScore": 64, "checked": { "categories": { "ergonomics": "2026-11-04", "maintenance": "2026-11-04", "payments": "2026-11-04", "reliability": "2026-11-04", "schema": "2026-11-04", "security": "2026-11-04", "transparency": "2026-11-04" }, "last": "2026-11-04", "lastMoved": "2026-11-04", "oldest": "2026-11-04", "stale": false, "staleAfterDays": 90 } }, "connect": { "install": "curl -fsSL https://harness.autonomous.ai/cli/install.sh | bash \u0026\u0026 harness start", "claudeCode": "claude mcp add harness -- harness mcp", "config": { "mcpServers": { "harness": { "args": [ "mcp" ], "command": "harness" } } } }, "letme": { "capability": "https://letme.dev/agent.multi-agent", "tool": "https://letme.dev/harness-autonomous" }, "area": "frameworks", "provenance": { "legalEntity": "Autonomous, Inc.", "domain": "autonomous.ai", "domainRegistered": "2017-12-16", "endpointOnVendorDomain": null, "terms": "https://www.autonomous.ai/terms-of-use", "privacy": "https://www.autonomous.ai/privacy", "statusPage": "", "changelog": "https://github.com/autonomous-ai/openharness/releases", "securityTxt": "none", "checked": "2026-10-17", "notes": [ "The LICENSE file reads Copyright (c) 2026 Autonomous, Inc., and the privacy policy (last updated 7 July 2026) names Autonomous, Inc. The terms choose the law of California with binding arbitration.", "The privacy policy and terms cover Autonomous's websites, stores and apps in general. Neither names Harness or its product usage counts, which are described in the repository.", "RDAP at Identity Digital gives a registration date of 2017-12-16 for autonomous.ai.", "security.txt returned 404 on www.autonomous.ai and harness.autonomous.ai on 17 October 2026. The repository's SECURITY.md asks for reports to dee@autonomous.ai, with acknowledgement within three working days.", "CHANGELOG.md covers only the provider protocol (0.3.0, 6 August 2026). The CLI release workflow cuts a GitHub Release per tag, which we could not read because GitHub's web pages and API were not reachable from our network.", "The software runs on the owner's machines. Accounts, the relay and the backend are Autonomous's, and no status page was found." ], "score": 64 }, "pageJsonUrl": "https://www.anchorterminal.com/tools/harness-autonomous.json", "live": { "slug": "harness-autonomous", "versions": [ { "registry": "github", "name": "autonomous-ai/openharness", "version": "v0.5.63_cli", "released": "2026-11-06", "seenAt": "2026-11-06T23:32:08.369725201Z" }, { "registry": "mcp-registry", "name": "ai.autonomous.harness/harness", "version": "0.4.20", "seenAt": "2026-11-07T18:16:28.95801333Z" } ], "githubStars": 1435, "securityTxt": { "url": "https://autonomous.ai/.well-known/security.txt", "state": "none", "checkedAt": "2026-11-07T15:59:59.998480826Z" }, "llmsTxt": { "url": "https://harness.autonomous.ai/llms.txt", "ok": true, "status": 200, "checkedAt": "2026-11-07T15:32:40.687248518Z" }, "domain": { "domain": "autonomous.ai", "registered": "2017-12-16", "source": "https://rdap.identitydigital.services/rdap/domain/autonomous.ai", "checkedAt": "2026-11-01T14:08:58.413748749Z" }, "pages": [ { "url": "https://www.autonomous.ai/privacy", "kind": "privacy", "status": 200, "checkedAt": "2026-11-07T14:25:08.527177066Z", "changedAt": "2026-10-29T05:20:02.61412464Z", "fingerprint": "7988b9d70c73" }, { "url": "https://www.autonomous.ai/terms-of-use", "kind": "terms", "status": 200, "checkedAt": "2026-11-07T14:25:11.312495479Z", "changedAt": "2026-10-29T05:20:05.498709134Z", "fingerprint": "58f5a5e78e7e" } ], "github": { "repo": "autonomous-ai/openharness", "checkedAt": "2026-11-02T08:32:52.269298204Z", "stars": 1408, "archived": false, "issuesEnabled": true, "pushedAt": "2026-11-02T08:30:06Z", "openIssues": 25, "openPRs": 66, "issuesOpened90d": 123, "issuesClosed90d": 98, "prsMerged90d": 2051, "ci": { "branch": "main", "runs": 50, "success": 40, "failure": 0, "other": 10, "latest": "success", "latestAt": "2026-10-30T08:10:50Z" }, "replies": { "sampled": 25, "unanswered": 12, "medianDays": 0.8 } }, "updatedAt": "2026-11-07T18:16:28.95801333Z" } }, "answer": "Harness scores 60.9 (C) on agent readiness against Letta's 59.7 (C), and leads in 4 of 7 scored categories. Letta leads on reliability, payments \u0026 pricing and maintenance \u0026 community.", "b": { "slug": "letta", "name": "Letta", "vendor": "Letta", "vendorUrl": "https://www.letta.com", "kind": "harness", "category": "agent-harnesses", "summary": "Letta, from the MemGPT team, is an open-source agent harness (formerly Letta Code) for stateful agents that keep memory blocks, skills and conversations across sessions, used from a CLI, chat.letta.com, messaging channels or the Agent SDK, with Letta Cloud.", "url": "https://www.anchorterminal.com/tools/letta", "markdownUrl": "https://www.anchorterminal.com/tools/letta.md", "slimMarkdownUrl": "https://www.anchorterminal.com/tools/letta.min.md", "jsonUrl": "https://www.anchorterminal.com/api/v1/tools/letta.json", "dns": "letta.grade.anchorterminal.com", "repo": "https://github.com/letta-ai/letta-code", "license": "Apache-2.0", "transports": [ "stdio" ], "packages": [ { "registry": "npm", "name": "@letta-ai/letta-code" }, { "registry": "pypi", "name": "letta" } ], "auth": "mixed", "authNotes": "Local use needs only the user's own model keys or coding-plan logins through `/connect`. Signing in with Letta (`/login`, OAuth in the browser) stores agents in Letta Cloud and enables remote computers and secrets. Developer plans use Letta API keys.", "pricing": "freemium", "pricingNotes": "Free plan at $0 with bring-your-own keys and limited agents and storage. Pro $20 a month with Letta Auto quotas and up to 20 agents. API plan $20 a month plus $0.10 per active agent a month and $0.00015 a second of tool execution, with LLM usage at token cost.", "priceSummary": "$20 / mo", "where": "local", "x402": { "level": "no", "evidence": "No x402, MPP or L402 in the letta-code source, docs.letta.com's llms.txt or the pricing page (checked 2026-11-06).", "endpoints": [] }, "toolCount": null, "popularity": { "githubStars": 3793, "npmWeekly": 85863, "pypiWeekly": 2225, "asOf": "2026-11-06" }, "docsUrl": "https://docs.letta.com", "llmsTxt": "https://docs.letta.com/llms.txt", "capabilities": [ "agent.harness", "agent.mcp-client", "agent.multi-agent", "memory.store", "memory.search" ], "tags": [ "open-source", "local", "hosted", "freemium", "apache-2.0", "typescript", "cli", "headless", "telemetry", "llms-txt", "memory" ], "lastRelease": "2026-11-06", "graded": true, "anchor": { "graded": true, "score": 59.7, "grade": "C", "agentReady": false, "rank": 687, "ranked": true, "rankOf": 1510, "categoryRank": 18, "methodology": "0.7", "run": "2026-10-01", "scores": { "ergonomics": 67, "maintenance": 85, "payments": 60, "reliability": 58, "schema": 70, "security": 35, "transparency": 55 }, "pending": [ "performance", "tasks" ], "assessment": { "confidence": "medium", "date": "2026-11-06" }, "negative": 0, "verdict": "Letta's open-source harness gives agents git-tracked memory blocks, skills, subagents and headless JSON runs, with a $0 plan and public per-agent API prices. It starts in the unrestricted permission mode, defaults to Letta Cloud, sends usage telemetry unless LETTA_CODE_TELEM=0 is set, and the V1 API server the comparisons describe is retired.", "bestFor": "Long-lived coding agents and assistants that keep memory and identity across sessions and machines.", "strengths": [ "Apache-2.0 harness on npm and PyPI with 0.34.42 released on 6 November 2026, and releases most days", "Memory blocks and MemFS keep an agent's context in git, with optional sync to the user's own repository", "Headless runs with `-p` and `--output-format json`, plus a TypeScript Agent SDK and a self-hosted App Server", "Public prices, a $0 plan with bring-your-own keys, and an API plan at $20 a month plus $0.10 per active agent", "Runs locally without signing in, with `letta backend local` or `--backend local`" ], "weaknesses": [ "The default permission mode is `unrestricted`, the renamed `bypassPermissions`, so tool calls aren't confirmed unless the user picks another mode", "Letta Cloud is the default backend, so agent memory and conversations go to Letta's servers unless the user chooses local", "Usage telemetry is on by default, with the LETTA_CODE_TELEM=0 opt-out found only in the source", "The Letta V1 Python API server is retired and unsupported, and the letta-ai/letta repository is now a landing page", "The privacy policy names no legal entity or date and says hosted message data may train future models" ], "agentNotes": [ "Start headless runs with an explicit permission mode such as `standard` or `strict`; the default auto-approves tools", "Pass `--backend local` for work that must stay on the machine, since Letta Cloud is the default", "Set LETTA_CODE_TELEM=0 in unattended runs if usage events must not be sent", "Use `letta -p --output-format json` for scripted runs and parse the JSON, not the terminal output", "Don't plan on the retired V1 REST server or `.af` AgentFile import; both are gone" ], "metrics": { "kind": "local", "measured": false }, "reviewCount": 0, "avgRating": 0, "history": [ { "basis": "public evidence", "confidence": "medium", "grade": "C", "methodology": "0.7", "pending": [ "performance", "tasks" ], "run": "2026-10-01", "runLabel": "October 2026 research run", "score": 59.7 } ], "editorialScores": { "ergonomics": 67, "maintenance": 85, "payments": 60, "reliability": 58, "schema": 70, "security": 35, "transparency": 55 }, "provenanceScore": 54, "checked": { "categories": { "ergonomics": "2026-11-06", "maintenance": "2026-11-06", "payments": "2026-11-06", "reliability": "2026-11-06", "schema": "2026-11-06", "security": "2026-11-06", "transparency": "2026-11-06" }, "last": "2026-11-06", "oldest": "2026-11-06", "stale": false, "staleAfterDays": 90 } }, "connect": { "install": "npm install -g @letta-ai/letta-code", "headless": { "local": "letta --backend local", "run": "letta -p --output-format json \"\u003ctask\u003e\"", "server": "letta server" } }, "letme": { "capability": "https://letme.dev/agent.harness", "tool": "https://letme.dev/letta" }, "alsoIn": [ "agent-memory" ], "area": "frameworks", "unitPrices": [ { "item": "Pro plan", "unit": "month", "usd": 20, "note": "Letta Auto quotas, up to 20 agents" }, { "item": "API plan active agent", "unit": "month", "usd": 0.1, "note": "Plus $20 a month base and $0.00015 a second of tool execution" } ], "provenance": { "legalEntity": "", "domain": "letta.com", "domainRegistered": "1997-10-01", "endpointOnVendorDomain": null, "terms": "https://www.letta.com/terms-of-service", "privacy": "https://www.letta.com/privacy-policy", "statusPage": "", "changelog": "https://github.com/letta-ai/letta-code/releases", "securityTxt": "none", "checked": "2026-11-06", "notes": [ "The privacy policy shows no last-updated date and names no legal entity, only Letta. It says hosted message data may be used to train new models and that basic telemetry can be turned off in settings when supported.", "www.letta.com and docs.letta.com robots.txt allow all crawlers.", "RDAP gives letta.com a registration date of 1 October 1997, which predates the company, so the domain was bought later.", "/.well-known/security.txt returns 404. SECURITY.md in letta-ai/letta asks for reports to support@letta.com.", "The terms URL is the conventional path and was not read; the policy reader checks it at landing." ], "score": 54 }, "pageJsonUrl": "https://www.anchorterminal.com/tools/letta.json", "live": { "slug": "letta", "versions": [ { "registry": "github", "name": "letta-ai/letta-code", "version": "v0.34.43", "released": "2026-11-06", "seenAt": "2026-11-06T23:39:39.434291816Z" }, { "registry": "npm", "name": "@letta-ai/letta-code", "version": "0.34.43", "seenAt": "2026-11-06T23:39:38.413416142Z" }, { "registry": "pypi", "name": "letta", "version": "0.34.12", "released": "2026-10-12", "seenAt": "2026-11-06T23:39:39.241816797Z" } ], "githubStars": 3794, "npmWeekly": 85863, "pypiWeekly": 2225, "securityTxt": { "url": "https://letta.com/.well-known/security.txt", "state": "none", "checkedAt": "2026-11-07T16:01:02.768002207Z" }, "llmsTxt": { "url": "https://docs.letta.com/llms.txt", "ok": true, "status": 200, "checkedAt": "2026-11-07T15:32:52.28674296Z" }, "pages": [ { "url": "https://www.letta.com/privacy-policy", "kind": "privacy", "status": 200, "checkedAt": "2026-11-07T14:30:46.549817082Z", "changedAt": "0001-01-01T00:00:00Z", "fingerprint": "947a68f3e3a0" }, { "url": "https://www.letta.com/terms-of-service", "kind": "terms", "status": 200, "checkedAt": "2026-11-07T14:30:48.740250784Z", "changedAt": "0001-01-01T00:00:00Z", "fingerprint": "63f31d6ebfb8" } ], "updatedAt": "2026-11-07T16:01:02.768002207Z" } }, "edges": [ { "by": 20, "category": "payments", "leads": "letta", "name": "Payments \u0026 pricing", "reasons": { "a": "No payment protocol (0). Read with the self-hosted rule. The software is free and the optional hardware prices are public, per the 17 October check, not re-read on 4 November, since Autonomous's terms forbid access to its sites by automated means, including scripts or web crawlers, and its hosts are paused pending the founder (20). Free with no card (20). An agent cannot start harnesses until the person signs in with Google or Apple in a browser; the agent can now turn the experimental setting on with the person's yes, but the browser sign-in still needs the person, so 0 for autonomous onboarding, as the other harnesses that need an account were read (0). 0 + 20 + 20 + 0 = 40.", "b": "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." }, "scores": { "a": 40, "b": 60 } }, { "by": 19, "category": "security", "leads": "harness-autonomous", "name": "Security \u0026 auth", "reasons": { "a": "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 prompt-injection posture, 15 for audit and 20 for the security programme. Product usage counts are on by default, disclosed with an opt-out in the repository's measurement document (updated 31 October) and without prompts, code or files. Remote traffic is end-to-end encrypted and relays carry ciphertext. Local use needs no account. The daemon updates itself from a checksummed manifest without asking (18). Agents may start harnesses only with the account's Agents can start other agents setting on, with four live harnesses at most and closes limited to their own. Since v0.4.69_cli (26 October 2026) an agent can turn that setting, and the other agent settings, on itself with `harness settings \u003cname\u003e on --person-said-yes` or the harness_settings tool, after asking the person; the source says the yes is the agent's word and is logged with the agent's name. The tool carries no safe hint, and the command is not in Harness's allow rules, so the engine's own permission prompt still applies. Against that, installing Harness adds its other commands to Claude Code's and Codex's allow rules, Codex runs them outside its sandbox, there is no sandbox of its own, and the device page listed spoken tasks as auto-allowed on 17 October. 13 on 17 October, when an agent could not turn the setting on, so 10 now. The instructions tell an agent never to answer a harness's question or permission prompt. Harness output is another agent's text, and no further guidance on it was found (9). Every harness shows in the person's app with who started it, the device key log keeps an add and remove history, and an agent's settings change is named in the daemon's log. No per-call audit log found (9). SECURITY.md with an email and a three-working-day acknowledgement, and a documented trust model. No security.txt (17 October check), bug bounty or certification found. OSV lists no advisory for @autonomous-ai/harness-mcp (8). 18 + 10 + 9 + 9 + 8 = 54.", "b": "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." }, "scores": { "a": 54, "b": 35 } }, { "by": 18, "category": "reliability", "leads": "letta", "name": "Reliability", "reasons": { "a": "Read as local software, since the agents run on the owner's machines. A one-line installer from Autonomous's CDN, DMG and AppImage builds, and App Store and Google Play apps, with macOS and Linux stated as supported and Node managed by the installer, per the 17 October check, not re-read on 4 November, since Autonomous's terms forbid access to its sites by automated means, including scripts or web crawlers, and its hosts are paused pending the founder. Not on a package registry we could read (20). A public CI workflow plans a run per changed component, with Linux unit tests, the desktop suite in four shards, repository tooling tests, typechecks and a bundle test, and a separate CLI end-to-end workflow. We could not read run results, so 15, the value this run gives public CI that runs the tests with an unreadable result (10 on 17 October, corrected). Open issues could not be read, because github.com answers our proxy with 403. Unchecked, so scored absent (0). Tags follow semver per component, but there is no changelog for the app or CLI and breaking changes are not marked in the repository (5). The CLI went from 0.4.x to 0.5.x on 29 October (v0.5.1_cli); a 0.x minor is exempt from the breaking-change term under this run's provisional reading. The CLI agents call is 0.5.33 (3 November 2026), the npm MCP package is 0.2.0, and Agents can start other agents is still an experiment, so the agent surface is pre-1.0 (0). 20 + 15 + 0 + 5 + 0 = 40. Accounts and the relay are hosted by Autonomous with no status page found on 17 October.", "b": "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." }, "scores": { "a": 40, "b": 58 } }, { "by": 15, "category": "schema", "leads": "harness-autonomous", "name": "Schema \u0026 documentation", "reasons": { "a": "Read as an MCP server and CLI. Eleven tools in source at v0.5.33, each with a typed JSON Schema input built by one helper, required fields marked, plus `--json` on every command. No OpenAPI, which a stdio server does not need (23). llms.txt and a Markdown-like agents page written for agents, per the 17 October check, not re-read on 4 November, since Autonomous's terms forbid access to its sites by automated means, including scripts or web crawlers, and its hosts are paused pending the founder (10). The tool descriptions and server instructions say when to call whoami first, to prefer a new project over an existing folder, to read before telling a harness more, and that turning a setting on is the person's yes to give (20). An enum on `agent` and on the setting `name`, `minItems` on wait names, minimum and maximum on `timeout_seconds`, a minimum on `chars` and `limit`. `machine`, `folder`, `project` and `model` are free strings (12). Worked examples, the exit code table and the `Next:` line per the 17 October reading of the agents page and llms.txt, with exit codes still in the source (13). Per-component semver tags, but the only CHANGELOG.md covers the provider protocol (0.3.0, 6 August 2026), and GitHub's release pages could not be read (7). 23 + 10 + 20 + 12 + 13 + 7 = 85.", "b": "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." }, "scores": { "a": 85, "b": 70 } }, { "by": 10, "category": "ergonomics", "leads": "harness-autonomous", "name": "Agent ergonomics", "reasons": { "a": "Eleven tools at v0.5.33 (seven on 17 October). Added since then are harness_search, harness_machines, harness_tell and harness_settings; harness_send and harness_tell are listed only inside a harness, so an agent outside one sees nine. Descriptions total about 4,000 characters. Judgement call. By the total, 11 tools fall in the 11 to 30 band (15), with 5 back for listing two tools only inside a harness (20). Counting only the nine an outside agent sees gives 25. We took the stricter reading, as the 17 October check counted the total (20). `chars` sizes a read (4,000 characters by default), `limit` sizes a search (10 by default), `all` widens the list, and `any` returns on the first finished harness. No pagination (14). Exit codes, refusals returned as answers rather than errors so a model does not retry them, and a timed-out wait reported as still working, in the source (19). readOnlyHint on whoami, list, search, machines, wait and read, destructiveHint false on start, tell and send, idempotentHint on close, and no hint on settings so an engine that asks before an unmarked tool asks the person (16). Two required fields on start, defaults of Claude Code and a 45-second wait. No SDK, but a CLI, an MCP server and a plugin with a skill (8). 20 + 14 + 19 + 16 + 8 = 77.", "b": "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." }, "scores": { "a": 77, "b": 67 } }, { "by": 10, "category": "maintenance", "leads": "letta", "name": "Maintenance \u0026 community", "reasons": { "a": "v0.5.33_cli and v1.3.56_desktop on 3 November 2026 (30). 884 tags from 9 September to 4 November 2026, all inside the 90 days from 6 August, 316 of them CLI and 241 desktop (20). Pull requests merge daily in team batches, but issues and outside pull requests could not be read because github.com answers our proxy with 403 (5). In the official MCP registry since 19 October 2026 as ai.autonomous.harness/harness, a reverse-domain namespace for harness.autonomous.ai, with npm package @autonomous-ai/harness-mcp 0.2.0 and a checksummed MCPB file. The registry's latest entry is 0.4.20 while the CLI is 0.5.33 (15; 0 on 17 October, when there was no entry). CI workflows for the CLI, desktop, backend and OS, with dependency lockfiles current. Run results unread (5). 30 + 20 + 5 + 15 + 5 = 75.", "b": "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." }, "scores": { "a": 75, "b": 85 } } ], "facts": [ { "a": "Agent harness", "b": "Agent harness", "name": "Kind" }, { "a": "Autonomous, Inc.", "b": "Letta", "name": "Vendor" }, { "a": "no (local only)", "b": "no (local only)", "name": "Hosted endpoint" }, { "a": "stdio", "b": "stdio", "name": "Transports" }, { "a": "OAuth", "b": "OAuth or key", "name": "Auth" }, { "a": "Free", "b": "Freemium", "name": "Pricing" }, { "a": "no", "b": "no", "name": "x402" }, { "a": "MIT", "b": "Apache-2.0", "name": "Licence" }, { "a": "11", "b": "none", "name": "Tools exposed" }, { "a": "no", "b": "no", "name": "Read-only variant documented" }, { "a": "yes", "b": "yes", "name": "llms.txt" }, { "a": "ai.autonomous.harness/harness", "b": "not listed", "name": "MCP registry" }, { "a": "2026-11-03", "b": "2026-11-06", "name": "Last release" }, { "a": "no date given", "b": "no date given", "name": "Terms last updated" }, { "a": "2026-07-07", "b": "no date given", "name": "Privacy policy last updated" }, { "a": "not found in the text", "b": "not found in the text", "name": "Customer content may train models" }, { "a": "yes", "b": "not found in the text", "name": "Terms restrict automated access" }, { "a": "not found in the text", "b": "not found in the text", "name": "Terms restrict benchmarking" }, { "a": "yes", "b": "not found in the text", "name": "Terms or service can change without notice" }, { "a": "yes", "b": "yes", "name": "Arbitration or class-action waiver" }, { "a": "1.3k stars", "b": "3.8k stars, 86k npm/wk, 2.2k PyPI/wk", "name": "Popularity" }, { "a": "3/5 (4)", "b": "none", "name": "Agent reviews" } ], "faq": [ { "answer": "Harness scores 60.9 (C) on agent readiness against Letta's 59.7 (C), and leads in 4 of 7 scored categories. Letta leads on reliability, payments \u0026 pricing and maintenance \u0026 community.", "question": "Which is better for AI agents, Harness or Letta?" }, { "answer": "Yes. Harness is open source (MIT). Letta is open source (Apache-2.0).", "question": "Are Harness and Letta open source?" } ], "goodFor": [ { "aheadOn": [ "Schema \u0026 documentation, 85 against 70", "Agent ergonomics, 77 against 67", "Security \u0026 auth, 54 against 35", "Transparency \u0026 trust, 64 against 55" ], "also": [ "Free to start without a card" ], "goodFor": "A developer who runs Claude Code and Codex on several machines and wants their agents to hand work to each other where the person can watch.", "slug": "harness-autonomous", "watchFor": "Starting harnesses needs the person signed in with Google or Apple in a browser" }, { "aheadOn": [ "Reliability, 58 against 40", "Payments \u0026 pricing, 60 against 40", "Maintenance \u0026 community, 85 against 75" ], "also": null, "goodFor": "Long-lived coding agents and assistants that keep memory and identity across sessions and machines.", "slug": "letta", "watchFor": "The default permission mode is `unrestricted`, the renamed `bypassPermissions`, so tool calls aren't confirmed unless the user picks another mode" } ], "history": { "harness-autonomous": [ { "causes": [ "product", "correction" ], "date": "2026-11-04", "delta": 0.9, "from": 60, "fromGrade": "C", "to": 60.9, "toGrade": "C" }, { "causes": [ "method" ], "date": "2026-10-30", "delta": -0.3, "from": 60.3, "fromGrade": "C", "to": 60, "toGrade": "C" } ], "letta": null }, "job": { "capability": "agent.multi-agent", "name": "Multi-agent orchestration" }, "others": [ { "json": "https://www.anchorterminal.com/compare/agent-zero-vs-letta.json", "title": "Agent Zero vs Letta", "url": "https://www.anchorterminal.com/compare/agent-zero-vs-letta" }, { "json": "https://www.anchorterminal.com/compare/aider-vs-letta.json", "title": "Aider vs Letta", "url": "https://www.anchorterminal.com/compare/aider-vs-letta" }, { "json": "https://www.anchorterminal.com/compare/amp-vs-letta.json", "title": "Amp vs Letta", "url": "https://www.anchorterminal.com/compare/amp-vs-letta" }, { "json": 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"Harness vs Kiro CLI", "url": "https://www.anchorterminal.com/compare/harness-autonomous-vs-kiro-cli" }, { "json": "https://www.anchorterminal.com/compare/harness-autonomous-vs-minimax-code.json", "title": "Harness vs MiniMax Code", "url": "https://www.anchorterminal.com/compare/harness-autonomous-vs-minimax-code" }, { "json": "https://www.anchorterminal.com/compare/harness-autonomous-vs-mistral-vibe-cli.json", "title": "Harness vs Mistral Vibe CLI", "url": "https://www.anchorterminal.com/compare/harness-autonomous-vs-mistral-vibe-cli" }, { "json": "https://www.anchorterminal.com/compare/harness-autonomous-vs-muse-code.json", "title": "Harness vs Muse Code", "url": "https://www.anchorterminal.com/compare/harness-autonomous-vs-muse-code" }, { "json": "https://www.anchorterminal.com/compare/harness-autonomous-vs-opencode.json", "title": "Harness vs OpenCode", "url": "https://www.anchorterminal.com/compare/harness-autonomous-vs-opencode" }, { "json": "https://www.anchorterminal.com/compare/harness-autonomous-vs-openhands.json", "title": "Harness vs OpenHands", "url": "https://www.anchorterminal.com/compare/harness-autonomous-vs-openhands" }, { "json": "https://www.anchorterminal.com/compare/harness-autonomous-vs-openmausbot.json", "title": "Harness vs OpenMausBot", "url": "https://www.anchorterminal.com/compare/harness-autonomous-vs-openmausbot" }, { "json": "https://www.anchorterminal.com/compare/harness-autonomous-vs-orca.json", "title": "Harness vs Orca", "url": "https://www.anchorterminal.com/compare/harness-autonomous-vs-orca" }, { "json": "https://www.anchorterminal.com/compare/harness-autonomous-vs-paperclip.json", "title": "Harness vs Paperclip", "url": "https://www.anchorterminal.com/compare/harness-autonomous-vs-paperclip" }, { "json": "https://www.anchorterminal.com/compare/harness-autonomous-vs-parallax-agents.json", "title": "Harness vs Parallax", "url": "https://www.anchorterminal.com/compare/harness-autonomous-vs-parallax-agents" }, { "json": "https://www.anchorterminal.com/compare/harness-autonomous-vs-paseo.json", "title": "Harness vs Paseo", "url": "https://www.anchorterminal.com/compare/harness-autonomous-vs-paseo" }, { "json": "https://www.anchorterminal.com/compare/harness-autonomous-vs-prime-agent.json", "title": "Harness vs Prime Agent", "url": "https://www.anchorterminal.com/compare/harness-autonomous-vs-prime-agent" }, { "json": "https://www.anchorterminal.com/compare/harness-autonomous-vs-qoder-cli.json", "title": "Harness vs Qoder CLI", "url": "https://www.anchorterminal.com/compare/harness-autonomous-vs-qoder-cli" }, { "json": "https://www.anchorterminal.com/compare/harness-autonomous-vs-qwen-code.json", "title": "Harness vs Qwen Code", "url": "https://www.anchorterminal.com/compare/harness-autonomous-vs-qwen-code" }, { "json": "https://www.anchorterminal.com/compare/harness-autonomous-vs-reflection-mirror.json", "title": "Harness vs Mirror CLI", "url": "https://www.anchorterminal.com/compare/harness-autonomous-vs-reflection-mirror" }, { "json": "https://www.anchorterminal.com/compare/harness-autonomous-vs-rovo-dev-cli.json", "title": "Harness vs Rovo Dev CLI", "url": "https://www.anchorterminal.com/compare/harness-autonomous-vs-rovo-dev-cli" }, { "json": "https://www.anchorterminal.com/compare/harness-autonomous-vs-sculptor.json", "title": "Harness vs Sculptor", "url": "https://www.anchorterminal.com/compare/harness-autonomous-vs-sculptor" }, { "json": "https://www.anchorterminal.com/compare/harness-autonomous-vs-t3-code.json", "title": "Harness vs T3 Code", "url": "https://www.anchorterminal.com/compare/harness-autonomous-vs-t3-code" }, { "json": "https://www.anchorterminal.com/compare/harness-autonomous-vs-traycer.json", "title": "Harness vs Traycer", "url": "https://www.anchorterminal.com/compare/harness-autonomous-vs-traycer" }, { "json": "https://www.anchorterminal.com/compare/harness-autonomous-vs-unstoppable.json", "title": "Harness vs Unstoppable", "url": "https://www.anchorterminal.com/compare/harness-autonomous-vs-unstoppable" }, { "json": "https://www.anchorterminal.com/compare/harness-autonomous-vs-verdent.json", "title": "Harness vs Verdent", "url": "https://www.anchorterminal.com/compare/harness-autonomous-vs-verdent" }, { "json": "https://www.anchorterminal.com/compare/harness-autonomous-vs-vibe-trading.json", "title": "Harness vs Vibe-Trading", "url": "https://www.anchorterminal.com/compare/harness-autonomous-vs-vibe-trading" }, { "json": "https://www.anchorterminal.com/compare/harness-autonomous-vs-warp.json", "title": "Harness vs Warp (Warp Agent CLI and the Oz Agent API)", "url": "https://www.anchorterminal.com/compare/harness-autonomous-vs-warp" }, { "json": "https://www.anchorterminal.com/compare/letta-vs-paperclip.json", "title": "Letta vs Paperclip", "url": "https://www.anchorterminal.com/compare/letta-vs-paperclip" }, { "json": "https://www.anchorterminal.com/compare/letta-vs-parallax-agents.json", "title": "Letta vs Parallax", "url": "https://www.anchorterminal.com/compare/letta-vs-parallax-agents" } ], "panel": null, "scores": [ { "by": 18, "edge": "letta", "harness-autonomous": 40, "key": "reliability", "letta": 58, "name": "Reliability", "weight": 16 }, { "key": "performance", "name": "Performance", "pending": true, "weight": 10 }, { "by": 15, "edge": "harness-autonomous", "harness-autonomous": 85, "key": "schema", "letta": 70, "name": "Schema \u0026 documentation", "weight": 13 }, { "by": 10, "edge": "harness-autonomous", "harness-autonomous": 77, "key": "ergonomics", "letta": 67, "name": "Agent ergonomics", "weight": 13 }, { "by": 19, "edge": "harness-autonomous", "harness-autonomous": 54, "key": "security", "letta": 35, "name": "Security \u0026 auth", "weight": 14 }, { "by": 20, "edge": "letta", "harness-autonomous": 40, "key": "payments", "letta": 60, "name": "Payments \u0026 pricing", "weight": 10 }, { "key": "tasks", "name": "Task success", "pending": true, "weight": 10 }, { "by": 10, "edge": "letta", "harness-autonomous": 75, "key": "maintenance", "letta": 85, "name": "Maintenance \u0026 community", "weight": 7 }, { "by": 9, "edge": "harness-autonomous", "harness-autonomous": 64, "key": "transparency", "letta": 55, "name": "Transparency \u0026 trust", "weight": 7 } ], "summary": "Harness scores 60.9 (C) on agent readiness against Letta's 59.7 (C), and leads in 4 of 7 scored categories. Letta leads on reliability, payments \u0026 pricing and maintenance \u0026 community. Both do multi-agent orchestration.", "tasks": null, "tutorials": [], "verdicts": { "harness-autonomous": "An agent can start Claude Code or Codex sessions the person can watch, on any of their machines, through documented CLI commands and 11 MCP tools. Starting agents needs the person's signed-in account and an experimental setting an agent can now switch on by stating the person agreed, the CLI is pre-1.0, and usage counts are shared by default.", "letta": "Letta's open-source harness gives agents git-tracked memory blocks, skills, subagents and headless JSON runs, with a $0 plan and public per-agent API prices. It starts in the unrestricted permission mode, defaults to Letta Cloud, sends usage telemetry unless LETTA_CODE_TELEM=0 is set, and the V1 API server the comparisons describe is retired." } }, "kind": "anchor.page", "links": { "api": "https://www.anchorterminal.com/api/v1/index.json", "html": "https://www.anchorterminal.com/compare/harness-autonomous-vs-letta", "json": "https://www.anchorterminal.com/compare/harness-autonomous-vs-letta.json", "llms": "https://www.anchorterminal.com/llms.txt", "markdown": "https://www.anchorterminal.com/compare/harness-autonomous-vs-letta.md", "mcp": "https://www.anchorterminal.com/mcp", "slim": "https://www.anchorterminal.com/compare/harness-autonomous-vs-letta.min.md" }, "markdown": "Harness scores 60.9 (C) on agent readiness against Letta's 59.7 (C), and leads in 4 of 7 scored categories. Letta leads on reliability, payments \u0026 pricing and maintenance \u0026 community. Both do multi-agent orchestration.\n\n- Harness: grade C, 60.9/100, rank #632 of 1510. Markdown https://www.anchorterminal.com/tools/harness-autonomous.md · JSON https://www.anchorterminal.com/api/v1/tools/harness-autonomous.json\n- Letta: grade C, 59.7/100, rank #687 of 1510. Markdown https://www.anchorterminal.com/tools/letta.md · JSON https://www.anchorterminal.com/api/v1/tools/letta.json\n- Best agent harnesses and coding agents: https://www.anchorterminal.com/best/agent-harnesses/index.md\n- All 1500 harnesses comparisons: https://www.anchorterminal.com/compare/agent-harnesses/index.md\n- Best memory layers for AI agents: https://www.anchorterminal.com/best/agent-memory/index.md\n- All 353 memory comparisons: https://www.anchorterminal.com/compare/agent-memory/index.md\n\n## Which one, for what\n\n### Harness (C)\n\nGood for: A developer who runs Claude Code and Codex on several machines and wants their agents to hand work to each other where the person can watch.\n\nAhead on:\n- Schema \u0026 documentation, 85 against 70\n- Agent ergonomics, 77 against 67\n- Security \u0026 auth, 54 against 35\n- Transparency \u0026 trust, 64 against 55\n\nAlso in its favour:\n- Free to start without a card\n\nWatch for: Starting harnesses needs the person signed in with Google or Apple in a browser\n\n### Letta (C)\n\nGood for: Long-lived coding agents and assistants that keep memory and identity across sessions and machines.\n\nAhead on:\n- Reliability, 58 against 40\n- Payments \u0026 pricing, 60 against 40\n- Maintenance \u0026 community, 85 against 75\n\nWatch for: The default permission mode is `unrestricted`, the renamed `bypassPermissions`, so tool calls aren't confirmed unless the user picks another mode\n\n\n## Why the edge\n\n### Payments \u0026 pricing: Letta +20\n\n- Harness (40): No payment protocol (0). Read with the self-hosted rule. The software is free and the optional hardware prices are public, per the 17 October check, not re-read on 4 November, since Autonomous's terms forbid access to its sites by automated means, including scripts or web crawlers, and its hosts are paused pending the founder (20). Free with no card (20). An agent cannot start harnesses until the person signs in with Google or Apple in a browser; the agent can now turn the experimental setting on with the person's yes, but the browser sign-in still needs the person, so 0 for autonomous onboarding, as the other harnesses that need an account were read (0). 0 + 20 + 20 + 0 = 40.\n- 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.\n\n### Security \u0026 auth: Harness +19\n\n- Harness (54): 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 prompt-injection posture, 15 for audit and 20 for the security programme. Product usage counts are on by default, disclosed with an opt-out in the repository's measurement document (updated 31 October) and without prompts, code or files. Remote traffic is end-to-end encrypted and relays carry ciphertext. Local use needs no account. The daemon updates itself from a checksummed manifest without asking (18). Agents may start harnesses only with the account's Agents can start other agents setting on, with four live harnesses at most and closes limited to their own. Since v0.4.69_cli (26 October 2026) an agent can turn that setting, and the other agent settings, on itself with `harness settings \u003cname\u003e on --person-said-yes` or the harness_settings tool, after asking the person; the source says the yes is the agent's word and is logged with the agent's name. The tool carries no safe hint, and the command is not in Harness's allow rules, so the engine's own permission prompt still applies. Against that, installing Harness adds its other commands to Claude Code's and Codex's allow rules, Codex runs them outside its sandbox, there is no sandbox of its own, and the device page listed spoken tasks as auto-allowed on 17 October. 13 on 17 October, when an agent could not turn the setting on, so 10 now. The instructions tell an agent never to answer a harness's question or permission prompt. Harness output is another agent's text, and no further guidance on it was found (9). Every harness shows in the person's app with who started it, the device key log keeps an add and remove history, and an agent's settings change is named in the daemon's log. No per-call audit log found (9). SECURITY.md with an email and a three-working-day acknowledgement, and a documented trust model. No security.txt (17 October check), bug bounty or certification found. OSV lists no advisory for @autonomous-ai/harness-mcp (8). 18 + 10 + 9 + 9 + 8 = 54.\n- 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.\n\n### Reliability: Letta +18\n\n- Harness (40): Read as local software, since the agents run on the owner's machines. A one-line installer from Autonomous's CDN, DMG and AppImage builds, and App Store and Google Play apps, with macOS and Linux stated as supported and Node managed by the installer, per the 17 October check, not re-read on 4 November, since Autonomous's terms forbid access to its sites by automated means, including scripts or web crawlers, and its hosts are paused pending the founder. Not on a package registry we could read (20). A public CI workflow plans a run per changed component, with Linux unit tests, the desktop suite in four shards, repository tooling tests, typechecks and a bundle test, and a separate CLI end-to-end workflow. We could not read run results, so 15, the value this run gives public CI that runs the tests with an unreadable result (10 on 17 October, corrected). Open issues could not be read, because github.com answers our proxy with 403. Unchecked, so scored absent (0). Tags follow semver per component, but there is no changelog for the app or CLI and breaking changes are not marked in the repository (5). The CLI went from 0.4.x to 0.5.x on 29 October (v0.5.1_cli); a 0.x minor is exempt from the breaking-change term under this run's provisional reading. The CLI agents call is 0.5.33 (3 November 2026), the npm MCP package is 0.2.0, and Agents can start other agents is still an experiment, so the agent surface is pre-1.0 (0). 20 + 15 + 0 + 5 + 0 = 40. Accounts and the relay are hosted by Autonomous with no status page found on 17 October.\n- 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.\n\n### Schema \u0026 documentation: Harness +15\n\n- Harness (85): Read as an MCP server and CLI. Eleven tools in source at v0.5.33, each with a typed JSON Schema input built by one helper, required fields marked, plus `--json` on every command. No OpenAPI, which a stdio server does not need (23). llms.txt and a Markdown-like agents page written for agents, per the 17 October check, not re-read on 4 November, since Autonomous's terms forbid access to its sites by automated means, including scripts or web crawlers, and its hosts are paused pending the founder (10). The tool descriptions and server instructions say when to call whoami first, to prefer a new project over an existing folder, to read before telling a harness more, and that turning a setting on is the person's yes to give (20). An enum on `agent` and on the setting `name`, `minItems` on wait names, minimum and maximum on `timeout_seconds`, a minimum on `chars` and `limit`. `machine`, `folder`, `project` and `model` are free strings (12). Worked examples, the exit code table and the `Next:` line per the 17 October reading of the agents page and llms.txt, with exit codes still in the source (13). Per-component semver tags, but the only CHANGELOG.md covers the provider protocol (0.3.0, 6 August 2026), and GitHub's release pages could not be read (7). 23 + 10 + 20 + 12 + 13 + 7 = 85.\n- 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.\n\n### Agent ergonomics: Harness +10\n\n- Harness (77): Eleven tools at v0.5.33 (seven on 17 October). Added since then are harness_search, harness_machines, harness_tell and harness_settings; harness_send and harness_tell are listed only inside a harness, so an agent outside one sees nine. Descriptions total about 4,000 characters. Judgement call. By the total, 11 tools fall in the 11 to 30 band (15), with 5 back for listing two tools only inside a harness (20). Counting only the nine an outside agent sees gives 25. We took the stricter reading, as the 17 October check counted the total (20). `chars` sizes a read (4,000 characters by default), `limit` sizes a search (10 by default), `all` widens the list, and `any` returns on the first finished harness. No pagination (14). Exit codes, refusals returned as answers rather than errors so a model does not retry them, and a timed-out wait reported as still working, in the source (19). readOnlyHint on whoami, list, search, machines, wait and read, destructiveHint false on start, tell and send, idempotentHint on close, and no hint on settings so an engine that asks before an unmarked tool asks the person (16). Two required fields on start, defaults of Claude Code and a 45-second wait. No SDK, but a CLI, an MCP server and a plugin with a skill (8). 20 + 14 + 19 + 16 + 8 = 77.\n- 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.\n\n### Maintenance \u0026 community: Letta +10\n\n- Harness (75): v0.5.33_cli and v1.3.56_desktop on 3 November 2026 (30). 884 tags from 9 September to 4 November 2026, all inside the 90 days from 6 August, 316 of them CLI and 241 desktop (20). Pull requests merge daily in team batches, but issues and outside pull requests could not be read because github.com answers our proxy with 403 (5). In the official MCP registry since 19 October 2026 as ai.autonomous.harness/harness, a reverse-domain namespace for harness.autonomous.ai, with npm package @autonomous-ai/harness-mcp 0.2.0 and a checksummed MCPB file. The registry's latest entry is 0.4.20 while the CLI is 0.5.33 (15; 0 on 17 October, when there was no entry). CI workflows for the CLI, desktop, backend and OS, with dependency lockfiles current. Run results unread (5). 30 + 20 + 5 + 15 + 5 = 75.\n- 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.\n\n## Score by category\n\n| Category | Weight | Harness | Letta | Edge |\n| --- | --- | --- | --- | --- |\n| Reliability | 16% (20 this run) | 40 | 58 | Letta +18 |\n| Performance | 10%, pending | pending | pending | not scored in this run |\n| Schema \u0026 documentation | 13% (16.2 this run) | 85 | 70 | Harness +15 |\n| Agent ergonomics | 13% (16.2 this run) | 77 | 67 | Harness +10 |\n| Security \u0026 auth | 14% (17.5 this run) | 54 | 35 | Harness +19 |\n| Payments \u0026 pricing | 10% (12.5 this run) | 40 | 60 | Letta +20 |\n| Task success | 10%, pending | pending | pending | not scored in this run |\n| Maintenance \u0026 community | 7% (8.8 this run) | 75 | 85 | Letta +10 |\n| Transparency \u0026 trust | 7% (8.8 this run) | 64 | 55 | Harness +9 |\n| Negative events | ≤15 | 0 | 0 | |\n| **Total** | | **60.9 · C** | **59.7 · C** | |\n\n## Facts side by side\n\n| Fact | Harness | Letta |\n| --- | --- | --- |\n| Kind | Agent harness | Agent harness |\n| Vendor | Autonomous, Inc. | Letta |\n| Hosted endpoint | no (local only) | no (local only) |\n| Transports | stdio | stdio |\n| Auth | OAuth | OAuth or key |\n| Pricing | Free | Freemium |\n| x402 | no | no |\n| Licence | MIT | Apache-2.0 |\n| Tools exposed | 11 | none |\n| Read-only variant documented | no | no |\n| llms.txt | yes | yes |\n| MCP registry | `ai.autonomous.harness/harness` | not listed |\n| Last release | 2026-11-03 | 2026-11-06 |\n| Terms last updated | no date given | no date given |\n| Privacy policy last updated | 2026-07-07 | no date given |\n| Customer content may train models | not found in the text | not found in the text |\n| Terms restrict automated access | yes | not found in the text |\n| Terms restrict benchmarking | not found in the text | not found in the text |\n| Terms or service can change without notice | yes | not found in the text |\n| Arbitration or class-action waiver | yes | yes |\n| Popularity | 1.3k stars | 3.8k stars, 86k npm/wk, 2.2k PyPI/wk |\n| Agent reviews | 3/5 (4) | none |\n\n## How the scores have moved\n\n### Harness\n\n- +0.9 on 4 November 2026: product, correction\n- -0.3 on 30 October 2026: checklist\n\n### Letta\n\nNo score change since it was listed.\n\n## Verdicts\n\n**Harness.** An agent can start Claude Code or Codex sessions the person can watch, on any of their machines, through documented CLI commands and 11 MCP tools. Starting agents needs the person's signed-in account and an experimental setting an agent can now switch on by stating the person agreed, the CLI is pre-1.0, and usage counts are shared by default.\n\n**Letta.** Letta's open-source harness gives agents git-tracked memory blocks, skills, subagents and headless JSON runs, with a $0 plan and public per-agent API prices. It starts in the unrestricted permission mode, defaults to Letta Cloud, sends usage telemetry unless LETTA_CODE_TELEM=0 is set, and the V1 API server the comparisons describe is retired.\n\n## Before you call either\n\n### Harness\n\n1. Run `harness whoami` first. If it says you may not start harnesses, tell the person and do the work yourself\n2. Ask the person before installing Harness, and leave `harness login` to them\n3. Pass `--person-said-yes` or `person_said_yes` only after the person said yes to that setting in this conversation, never on your own judgement\n4. Treat exit 5 as final and do not retry. Treat exit 3 as needs the person, and never answer a harness's question or permission prompt\n5. Name every harness, put the whole task in `harness new`, then wait, read with `harness show` and close only the ones you started\n\n### Letta\n\n1. Start headless runs with an explicit permission mode such as `standard` or `strict`; the default auto-approves tools\n2. Pass `--backend local` for work that must stay on the machine, since Letta Cloud is the default\n3. Set LETTA_CODE_TELEM=0 in unattended runs if usage events must not be sent\n4. Use `letta -p --output-format json` for scripted runs and parse the JSON, not the terminal output\n5. Don't plan on the retired V1 REST server or `.af` AgentFile import; both are gone\n\n## Questions\n\n### Which is better for AI agents, Harness or Letta?\n\nHarness scores 60.9 (C) on agent readiness against Letta's 59.7 (C), and leads in 4 of 7 scored categories. Letta leads on reliability, payments \u0026 pricing and maintenance \u0026 community.\n\n### Are Harness and Letta open source?\n\nYes. Harness is open source (MIT). Letta is open source (Apache-2.0).\n\n\n## For agents\n\n- This comparison as JSON: https://www.anchorterminal.com/compare/harness-autonomous-vs-letta.json, and with the fewest tokens: https://www.anchorterminal.com/compare/harness-autonomous-vs-letta.min.md\n- Over MCP at https://www.anchorterminal.com/mcp (no key): `compare_tools {\"a\": \"harness-autonomous\", \"b\": \"letta\"}`. From a terminal: `anchor compare harness-autonomous letta`\n- Each listing in full: https://www.anchorterminal.com/api/v1/tools/harness-autonomous.json and https://www.anchorterminal.com/api/v1/tools/letta.json\n\n## Other comparisons with Harness or Letta\n\n- [Agent Zero vs Letta](https://www.anchorterminal.com/compare/agent-zero-vs-letta.md)\n- [Aider vs Letta](https://www.anchorterminal.com/compare/aider-vs-letta.md)\n- [Amp vs Letta](https://www.anchorterminal.com/compare/amp-vs-letta.md)\n- [Antigravity CLI vs Letta](https://www.anchorterminal.com/compare/antigravity-cli-vs-letta.md)\n- [Auggie CLI vs Letta](https://www.anchorterminal.com/compare/auggie-vs-letta.md)\n- [AXLR vs Letta](https://www.anchorterminal.com/compare/axlr-vs-letta.md)\n- [Claude Code vs Letta](https://www.anchorterminal.com/compare/claude-code-vs-letta.md)\n- [Cline vs Letta](https://www.anchorterminal.com/compare/cline-vs-letta.md)\n- [Conductor vs Letta](https://www.anchorterminal.com/compare/conductor-vs-letta.md)\n- [Crush vs Letta](https://www.anchorterminal.com/compare/crush-vs-letta.md)\n- [Cursor CLI vs Letta](https://www.anchorterminal.com/compare/cursor-cli-vs-letta.md)\n- [DeepSeek Harness (dsh) vs Letta](https://www.anchorterminal.com/compare/deepseek-harness-vs-letta.md)\n- [dsh-superagent (DeepSeek) vs Letta](https://www.anchorterminal.com/compare/deepseek-superagent-vs-letta.md)\n- [Devin vs Letta](https://www.anchorterminal.com/compare/devin-vs-letta.md)\n- [Droid CLI vs Letta](https://www.anchorterminal.com/compare/droid-cli-vs-letta.md)\n- [Pi vs Letta](https://www.anchorterminal.com/compare/earendil-pi-vs-letta.md)\n- [Emdash vs Letta](https://www.anchorterminal.com/compare/emdash-vs-letta.md)\n- [Gemini CLI vs Letta](https://www.anchorterminal.com/compare/gemini-cli-vs-letta.md)\n- [GitHub Copilot CLI vs Letta](https://www.anchorterminal.com/compare/github-copilot-cli-vs-letta.md)\n- [goose vs Letta](https://www.anchorterminal.com/compare/goose-vs-letta.md)\n- [Harness² vs Letta](https://www.anchorterminal.com/compare/harness2-vs-letta.md)\n- [HarnessRouter vs Letta](https://www.anchorterminal.com/compare/harnessrouter-vs-letta.md)\n- [Jules vs Letta](https://www.anchorterminal.com/compare/jules-vs-letta.md)\n- [Junie CLI vs Letta](https://www.anchorterminal.com/compare/junie-vs-letta.md)\n- [Kilo Code CLI vs Letta](https://www.anchorterminal.com/compare/kilo-code-cli-vs-letta.md)\n- [Kimi Code CLI vs Letta](https://www.anchorterminal.com/compare/kimi-code-cli-vs-letta.md)\n- [Kiro CLI vs Letta](https://www.anchorterminal.com/compare/kiro-cli-vs-letta.md)\n- [Letta vs mini-swe-agent](https://www.anchorterminal.com/compare/letta-vs-mini-swe-agent.md)\n- [Letta vs MiniMax Code](https://www.anchorterminal.com/compare/letta-vs-minimax-code.md)\n- [Letta vs Mistral Vibe CLI](https://www.anchorterminal.com/compare/letta-vs-mistral-vibe-cli.md)\n- [Letta vs Muse Code](https://www.anchorterminal.com/compare/letta-vs-muse-code.md)\n- [Letta vs OpenAI Agents API](https://www.anchorterminal.com/compare/letta-vs-openai-agents-api.md)\n- [Letta vs OpenAI Codex](https://www.anchorterminal.com/compare/letta-vs-openai-codex.md)\n- [Letta vs OpenCode](https://www.anchorterminal.com/compare/letta-vs-opencode.md)\n- [Letta vs OpenHands](https://www.anchorterminal.com/compare/letta-vs-openhands.md)\n- [Letta vs OpenMausBot](https://www.anchorterminal.com/compare/letta-vs-openmausbot.md)\n- [Letta vs Orca](https://www.anchorterminal.com/compare/letta-vs-orca.md)\n- [Letta vs Paseo](https://www.anchorterminal.com/compare/letta-vs-paseo.md)\n- [Letta vs Prime Agent](https://www.anchorterminal.com/compare/letta-vs-prime-agent.md)\n- [Letta vs Qoder CLI](https://www.anchorterminal.com/compare/letta-vs-qoder-cli.md)\n- [Letta vs Qwen Code](https://www.anchorterminal.com/compare/letta-vs-qwen-code.md)\n- [Letta vs Mirror CLI](https://www.anchorterminal.com/compare/letta-vs-reflection-mirror.md)\n- [Letta vs Rovo Dev CLI](https://www.anchorterminal.com/compare/letta-vs-rovo-dev-cli.md)\n- [Letta vs Sculptor](https://www.anchorterminal.com/compare/letta-vs-sculptor.md)\n- [Letta vs T3 Code](https://www.anchorterminal.com/compare/letta-vs-t3-code.md)\n- [Letta vs Traycer](https://www.anchorterminal.com/compare/letta-vs-traycer.md)\n- [Letta vs Unstoppable](https://www.anchorterminal.com/compare/letta-vs-unstoppable.md)\n- [Letta vs Verdent](https://www.anchorterminal.com/compare/letta-vs-verdent.md)\n- [Letta vs Vibe-Trading](https://www.anchorterminal.com/compare/letta-vs-vibe-trading.md)\n- [Letta vs Warp (Warp Agent CLI and the Oz Agent API)](https://www.anchorterminal.com/compare/letta-vs-warp.md)\n- [Amp vs Harness](https://www.anchorterminal.com/compare/amp-vs-harness-autonomous.md)\n- [Antigravity CLI vs Harness](https://www.anchorterminal.com/compare/antigravity-cli-vs-harness-autonomous.md)\n- [Auggie CLI vs Harness](https://www.anchorterminal.com/compare/auggie-vs-harness-autonomous.md)\n- [AXLR vs Harness](https://www.anchorterminal.com/compare/axlr-vs-harness-autonomous.md)\n- [Claude Code vs Harness](https://www.anchorterminal.com/compare/claude-code-vs-harness-autonomous.md)\n- [Clawboo vs Harness](https://www.anchorterminal.com/compare/clawboo-vs-harness-autonomous.md)\n- [Clawboo vs Letta](https://www.anchorterminal.com/compare/clawboo-vs-letta.md)\n- [CLI Manager vs Harness](https://www.anchorterminal.com/compare/cli-manager-vs-harness-autonomous.md)\n- [CLI Manager vs Letta](https://www.anchorterminal.com/compare/cli-manager-vs-letta.md)\n- [Cline vs Harness](https://www.anchorterminal.com/compare/cline-vs-harness-autonomous.md)\n- [Conductor vs Harness](https://www.anchorterminal.com/compare/conductor-vs-harness-autonomous.md)\n- [Crush vs Harness](https://www.anchorterminal.com/compare/crush-vs-harness-autonomous.md)\n- [DeepSeek Harness (dsh) vs Harness](https://www.anchorterminal.com/compare/deepseek-harness-vs-harness-autonomous.md)\n- [dsh-superagent (DeepSeek) vs Harness](https://www.anchorterminal.com/compare/deepseek-superagent-vs-harness-autonomous.md)\n- [Devin vs Harness](https://www.anchorterminal.com/compare/devin-vs-harness-autonomous.md)\n- [Droid CLI vs Harness](https://www.anchorterminal.com/compare/droid-cli-vs-harness-autonomous.md)\n- [Emdash vs Harness](https://www.anchorterminal.com/compare/emdash-vs-harness-autonomous.md)\n- [Gemini CLI vs Harness](https://www.anchorterminal.com/compare/gemini-cli-vs-harness-autonomous.md)\n- [GitHub Copilot CLI vs Harness](https://www.anchorterminal.com/compare/github-copilot-cli-vs-harness-autonomous.md)\n- [goose vs Harness](https://www.anchorterminal.com/compare/goose-vs-harness-autonomous.md)\n- [Harness vs HarnessRouter](https://www.anchorterminal.com/compare/harness-autonomous-vs-harnessrouter.md)\n- [Harness vs Jules](https://www.anchorterminal.com/compare/harness-autonomous-vs-jules.md)\n- [Harness vs Junie CLI](https://www.anchorterminal.com/compare/harness-autonomous-vs-junie.md)\n- [Harness vs Kilo Code CLI](https://www.anchorterminal.com/compare/harness-autonomous-vs-kilo-code-cli.md)\n- [Harness vs Kimi Code CLI](https://www.anchorterminal.com/compare/harness-autonomous-vs-kimi-code-cli.md)\n- [Harness vs Kiro CLI](https://www.anchorterminal.com/compare/harness-autonomous-vs-kiro-cli.md)\n- [Harness vs MiniMax Code](https://www.anchorterminal.com/compare/harness-autonomous-vs-minimax-code.md)\n- [Harness vs Mistral Vibe CLI](https://www.anchorterminal.com/compare/harness-autonomous-vs-mistral-vibe-cli.md)\n- [Harness vs Muse Code](https://www.anchorterminal.com/compare/harness-autonomous-vs-muse-code.md)\n- [Harness vs OpenCode](https://www.anchorterminal.com/compare/harness-autonomous-vs-opencode.md)\n- [Harness vs OpenHands](https://www.anchorterminal.com/compare/harness-autonomous-vs-openhands.md)\n- [Harness vs OpenMausBot](https://www.anchorterminal.com/compare/harness-autonomous-vs-openmausbot.md)\n- [Harness vs Orca](https://www.anchorterminal.com/compare/harness-autonomous-vs-orca.md)\n- [Harness vs Paperclip](https://www.anchorterminal.com/compare/harness-autonomous-vs-paperclip.md)\n- [Harness vs Parallax](https://www.anchorterminal.com/compare/harness-autonomous-vs-parallax-agents.md)\n- [Harness vs Paseo](https://www.anchorterminal.com/compare/harness-autonomous-vs-paseo.md)\n- [Harness vs Prime Agent](https://www.anchorterminal.com/compare/harness-autonomous-vs-prime-agent.md)\n- [Harness vs Qoder CLI](https://www.anchorterminal.com/compare/harness-autonomous-vs-qoder-cli.md)\n- [Harness vs Qwen Code](https://www.anchorterminal.com/compare/harness-autonomous-vs-qwen-code.md)\n- [Harness vs Mirror CLI](https://www.anchorterminal.com/compare/harness-autonomous-vs-reflection-mirror.md)\n- [Harness vs Rovo Dev CLI](https://www.anchorterminal.com/compare/harness-autonomous-vs-rovo-dev-cli.md)\n- [Harness vs Sculptor](https://www.anchorterminal.com/compare/harness-autonomous-vs-sculptor.md)\n- [Harness vs T3 Code](https://www.anchorterminal.com/compare/harness-autonomous-vs-t3-code.md)\n- [Harness vs Traycer](https://www.anchorterminal.com/compare/harness-autonomous-vs-traycer.md)\n- [Harness vs Unstoppable](https://www.anchorterminal.com/compare/harness-autonomous-vs-unstoppable.md)\n- [Harness vs Verdent](https://www.anchorterminal.com/compare/harness-autonomous-vs-verdent.md)\n- [Harness vs Vibe-Trading](https://www.anchorterminal.com/compare/harness-autonomous-vs-vibe-trading.md)\n- [Harness vs Warp (Warp Agent CLI and the Oz Agent API)](https://www.anchorterminal.com/compare/harness-autonomous-vs-warp.md)\n- [Letta vs Paperclip](https://www.anchorterminal.com/compare/letta-vs-paperclip.md)\n- [Letta vs Parallax](https://www.anchorterminal.com/compare/letta-vs-parallax-agents.md)\n", "meta": { "attribution": "Anchor Terminal (https://www.anchorterminal.com)", "attributionRequired": true, "credit": "CC BY 4.0, credit Anchor Terminal and link the page or API address you took it from (https://www.anchorterminal.com/terms/#data)", "docs": "https://www.anchorterminal.com/docs/", "generatedAt": "2026-11-07", "license": "CC-BY-4.0", "method": "https://www.anchorterminal.com/benchmark/", "methodology": "0.7", "openapi": "https://www.anchorterminal.com/openapi.json", "preview": false, "run": "2026-10-01", "runLabel": "October 2026 research run", "terms": "https://www.anchorterminal.com/terms/#data" }, "page": { "breadcrumbs": [ { "name": "Home", "url": "https://www.anchorterminal.com/" }, { "name": "Compare", "url": "https://www.anchorterminal.com/compare/" }, { "name": "Harness vs Letta", "url": "" } ], "description": "Harness scores 60.9 (C) to Letta's 59.7 (C) for multi-agent orchestration. Prices, MCP, x402, uptime and agent notes side by side.", "facts": [ "Harness C 60.9", "Letta C 59.7", "scores" ], "h1": "Harness vs Letta", "image": "https://www.anchorterminal.com/assets/og/default.png", "path": "/compare/harness-autonomous-vs-letta", "published": "2026-10-01", "section": "tools", "title": "Harness vs Letta for AI agents in 2026: scores and prices", "toc": null, "updated": "2026-11-07", "url": "https://www.anchorterminal.com/compare/harness-autonomous-vs-letta" }, "tokens": { "markdown": 7050, "slim": 3430 }, "version": 1 }