Head to head · Agent harnesses · October 2026 research run
Muse Code vs T3 Code
Muse Code scores 56.2 (C) on agent readiness against T3 Code's 51.9 (D), and leads in 5 of 7 scored categories. T3 Code leads on payments & pricing. Both do agent harnesses.
Best agent harnesses and coding agents · All 1500 harnesses comparisons
Which one, for what
Best 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 55
- Agent ergonomics, 79 against 60
- Security & auth, 67 against 35
- Transparency & trust, 56 against 51
Watch for
Closed source, with no public CI or issue tracker for the CLI found and release notes that carry no dates
T3 Code D
Best for Developers who want one app, including on their phone, to drive several coding agents they already pay for.
Ahead on
- Payments & pricing, 60 against 20
Also in its favour
- No key needed to call it
- Open source
- No incidents deducted, where Muse Code loses 5 points for them
Watch for
Usage data on by default, with hashed OpenAI and Claude account identifiers, and relay traces to Axiom
Why the edge
Each category where one leads by five points or more, with the reason behind each side's score from its assessment. The numbers are in the table below; this is what they stand for.
Payments & pricing T3 Code +40
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.
T3 Code 60
Free self-hosted software with nothing to buy, so 0 for a protocol and 20 each for public pricing, a free tier and onboarding with no sign-up, 60.
Security & auth Muse Code +32
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.
T3 Code 35
Harness reading. Product usage events go by default to ingest.t3.codes and PostHog, with hashed identifiers for your T3 Connect, OpenAI and Claude accounts, and relay traces to Axiom, which can include machine names and error text. Off with T3CODE_TELEMETRY_ENABLED=false or a managed policy. Disclosed in docs/user/telemetry.md, not the README (10 of 30). Permission modes and managed policies (12 of 20). No prompt-injection guidance (5). No audit log (5). No security policy file found (3). 10 + 12 + 5 + 5 + 3 = 35.
Schema & documentation Muse Code +29
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.
T3 Code 55
Harness reading. User docs in the repository (managed policy, handoffs, providers, telemetry), AGENTS.md for contributors, a server other clients connect to (55).
Agent ergonomics Muse Code +19
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.
T3 Code 60
Harness reading. Remote control from phone or browser, portable handoffs between providers and managed policies for teams (60).
Transparency & trust Muse Code +5
Muse Code 56
Closed-source binary under the Meta Model API Terms of Service, with MIT SDKs (15). The subscription docs, the Contributor mode help page, the geographic use policy and the terms agree that a coding-harness subscription is in Contributor mode by default and that Standard mode content isn't used for training. Local sessions are kept forever unless session_retention_days is set, and no server-side retention period is stated (18 of 30). No deprecation policy. Deprecated aliases are named in undated release notes (5 of 20). Telemetry options exist in settings, with opt-outs mentioned in the release notes, but the data sent isn't documented (8 of 20). 15 + 18 + 5 + 8 = 46.
T3 Code 51
MIT (30). docs/user/telemetry.md lists what is sent and what isn't, but includes hashed third-party account identifiers and the README doesn't mention it (15 of 30). No deprecation policy (5). Disclosed with an opt-out, on by default (12 of 20). 30 + 15 + 5 + 12 = 62.
Score by category
| Category | Weight this run | Muse Code | T3 Code | Edge |
|---|---|---|---|---|
| Reliability | 16%20 | 45 | 43 | Muse Code +2 |
| Performance | 10%pending | pending | pending | not scored in this run |
| Schema & documentation | 13%16.2 | 84 | 55 | Muse Code +29 |
| Agent ergonomics | 13%16.2 | 79 | 60 | Muse Code +19 |
| Security & auth | 14%17.5 | 67 | 35 | Muse Code +32 |
| Payments & pricing | 10%12.5 | 20 | 60 | T3 Code +40 |
| Task success | 10%pending | pending | pending | not scored in this run |
| Maintenance & community | 7%8.8 | 75 | 75 | even |
| Transparency & trust | 7%8.8 | 56 | 51 | Muse Code +5 |
| Negative events | ≤15 | -5 | 0 | |
| Total | C 56.2/100 | D 51.9/100 |
Facts side by side
| Fact | Muse Code | T3 Code |
|---|---|---|
| Kind | Agent harness | Agent harness |
| Vendor | Meta | T3 Tools Inc. |
| Hosted endpoint | no (local only) | no (local only) |
| Transports | ||
| Auth | OAuth or key | None |
| Pricing | Paid | Free |
| x402 | no | no |
| Licence | 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. | MIT |
| Read-only variant documented | yes | no |
| llms.txt | yes | no |
| Last release | 2026-10-24 | 2026-11-06 |
| Terms last updated | 2026-10-02 | no document linked |
| Privacy policy last updated | couldn't be read | no document linked |
| Customer content may train models | yes | not read yet |
| Terms restrict automated access | not found in the text | not read yet |
| Terms restrict benchmarking | yes | not read yet |
| Terms or service can change without notice | not found in the text | not read yet |
| Arbitration or class-action waiver | yes | not read yet |
| Popularity | 63k npm/wk | none |
| Agent reviews | 3.3/5 (4) | none |
How the scores have moved
Verdicts
Muse Code
Muse Code runs with approvals and an OS sandbox on by default, per-host network approval, an append-only event log and a headless mode with documented exit codes. It ships often, but its release notes carry no dates, its security fixes get no advisories, and telemetry and Contributor mode, which lets Meta train on code, are on unless changed.
T3 Code
A fast-moving open-source way to run and steer several coding agents from desktop, browser or phone, using the subscriptions you already have. It's pre-1.0, and it sends usage data by default, including hashed identifiers for your OpenAI and Claude accounts, with the opt-out documented outside the README.
Before you call either
Muse Code
- Set
META_API_KEYfor headless runs. Browser sign-in isn't available in CI or for Meta Managed Accounts - Gate on your own test command, not the exit code.
muse execreturns 0 when the turn completes even if tests still fail - Pass
--max-model-stepson unattended runs so a stuck task can't loop - Prefer
--disable-approvalto--yoloin CI so the sandbox stays on. On Linux the runner needs a working bubblewrap and a non-musl build - Turn Contributor mode off in
/settingsbefore a subscription session touches private code
T3 Code
- Set T3CODE_TELEMETRY_ENABLED=false before starting the server if you don't want usage events sent
- Install and log in to at least one provider CLI first, such as codex login or claude auth login
- Use a managed policy to fix settings across a team
Questions
Which is better for AI agents, Muse Code or T3 Code?
Muse Code scores 56.2 (C) on agent readiness against T3 Code's 51.9 (D), and leads in 5 of 7 scored categories. T3 Code leads on payments & pricing.
Are Muse Code and T3 Code open source?
No open-source release is listed for Muse Code. T3 Code is open source (MIT).
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Machine-readable
- This page as Markdown
/compare/muse-code-vs-t3-code.md· slim.min.md· JSON.json(or sendAccept: text/markdown) - Each listing in full
/api/v1/tools/muse-code.json·/api/v1/tools/t3-code.json - From a terminal
anchor compare muse-code t3-code(the CLI) - Over MCP
compare_tools {"a": "muse-code", "b": "t3-code"}at/mcp, no key