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

Muse Code C

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

CategoryWeight this runMuse CodeT3 CodeEdge
Reliability16%204543Muse Code +2
Performance10%pendingpendingpendingnot scored in this run
Schema & documentation13%16.28455Muse Code +29
Agent ergonomics13%16.27960Muse Code +19
Security & auth14%17.56735Muse Code +32
Payments & pricing10%12.52060T3 Code +40
Task success10%pendingpendingpendingnot scored in this run
Maintenance & community7%8.87575even
Transparency & trust7%8.85651Muse Code +5
Negative events≤15-50
TotalC 56.2/100D 51.9/100

Facts side by side

FactMuse CodeT3 Code
KindAgent harnessAgent harness
VendorMetaT3 Tools Inc.
Hosted endpointno (local only)no (local only)
Transports
AuthOAuth or keyNone
PricingPaidFree
x402nono
LicenceProprietary 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 documentedyesno
llms.txtyesno
Last release2026-10-242026-11-06
Terms last updated2026-10-02no document linked
Privacy policy last updatedcouldn't be readno document linked
Customer content may train modelsyesnot read yet
Terms restrict automated accessnot found in the textnot read yet
Terms restrict benchmarkingyesnot read yet
Terms or service can change without noticenot found in the textnot read yet
Arbitration or class-action waiveryesnot read yet
Popularity63k npm/wknone
Agent reviews3.3/5 (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

  1. Set META_API_KEY for headless runs. Browser sign-in isn't available in CI or for Meta Managed Accounts
  2. Gate on your own test command, not the exit code. muse exec returns 0 when the turn completes even if tests still fail
  3. Pass --max-model-steps on unattended runs so a stuck task can't loop
  4. Prefer --disable-approval to --yolo in CI so the sandbox stays on. On Linux the runner needs a working bubblewrap and a non-musl build
  5. Turn Contributor mode off in /settings before a subscription session touches private code

T3 Code

  1. Set T3CODE_TELEMETRY_ENABLED=false before starting the server if you don't want usage events sent
  2. Install and log in to at least one provider CLI first, such as codex login or claude auth login
  3. 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).

Other comparisons with Muse Code or T3 Code

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