Head to head · Agent harnesses · October 2026 research run

Mirror CLI vs T3 Code

Mirror CLI scores 57.2 (C) on agent readiness against T3 Code's 51.9 (D), and leads in 3 of 7 scored categories. T3 Code leads on maintenance & community. Both do agent harnesses.

Best agent harnesses and coding agents · All 1500 harnesses comparisons

Which one, for what

Mirror CLI C

Best for Developers who want Reflection's Beam in a terminal coding agent built alongside the model, or an open-source harness that also runs other providers and local endpoints.

Ahead on

  • Schema & documentation, 75 against 55
  • Security & auth, 58 against 35
  • Transparency & trust, 66 against 51

Also in its favour

  • Free to start without a card

Watch for

Version 0.1.x, labelled early beta, with an undated changelog and no CLI release tags

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

  • Maintenance & community, 75 against 47

Also in its favour

  • No key needed to call it

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.

Maintenance & community T3 Code +28

Mirror CLI 47

0.1.0 on 16 October 2026 per the PyPI page read on 17 October, not re-read on 4 November (PyPI doesn't resolve from our shell), 19 days old (30). The 90-day line needs three dated releases. 0.1.0 (16 October) and the mirror-agent-v0.1.8 tag on the same commit, f938033, are one release day, and 0.1.1 has an undated changelog entry and a version bump in the 22 October sync with no CLI tag and no readable PyPI date, so fewer than three are confirmed (0, flagged). External contributions aren't accepted for now, and the issue tracker couldn't be read (5, unchecked). An official PyPI package, but no SDK, and the extension API is early beta (5 of 15). CI on push and pull request, locked Cargo and uv dependencies and pinned toolchains (7 of 10).

T3 Code 75

Commits and nightly tags on 6 November 2026 (30). More than three releases in 90 days (20). GitHub issues and pull requests weren't read (GitHub's pages refuse these sessions), so that line is scored absent (0). Current official apps and install script (15). CI on push (10). 30 + 20 + 0 + 15 + 10 = 75.

Security & auth Mirror CLI +23

Mirror CLI 58

Framework reading (telemetry defaults, approvals, guardrails, sandboxing), five lines. Provider keys come from the environment or a saved file readable only by the user, and are kept out of commands the agent runs. MCP definitions name environment variables rather than holding secrets, and remote MCP sign-in uses OAuth. Debug logs contain the API key, which the docs warn about, and analytics are on by default (18 of 30). Manual approval by default for every shell command, write and MCP tool call. Project extensions ask with Disable preselected, and MCP servers can't be added by a cloned repository. Auto mode, once chosen, applies in every directory (15 of 20). SECURITY.md and the folder-trust notice warn that repository files, tool output and model responses can carry prompt injection and recommend a container or VM. The microVM sandbox is opt-in and covers file and shell tools only (9 of 15). Conversations with their tool calls are kept in ~/.mirror/state.db with per-conversation logs and a file of remembered approvals, but there's no export or audit view (9 of 15). SECURITY.md gives a private email and a report scope, but there's no security.txt, bug bounty or published advisory (7 of 20). 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 Mirror CLI +20

Mirror CLI 75

Framework reading. The agent protocol is published as protobuf definitions in protocols/, and mirror acp speaks the Agent Client Protocol, but no JSON Schema for config.json or the MCP definition files was found (15 of 25). llms.txt with a Markdown copy of every page (10). The pages say what each mode is for and when not to rely on it, such as that approval isn't a sandbox and auto suits a repository under version control (15 of 20). Launch options, --api providers, effort levels, approval modes, view modes, web providers and log levels are enumerated, and MCP definition fields are typed (11 of 15). Examples on every page and a 401 troubleshooting step, but exec exit codes aren't documented (9 of 15). Versions with a stated tag scheme (reflection-mirror-vX.Y.Z for the CLI, mirror-agent-vX.Y.Z for the agent) and a public CHANGELOG.md in the repository since 22 October 2026 (15).

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).

Transparency & trust Mirror CLI +15

Mirror CLI 66

Apache-2.0, with NOTICE and third-party licences in the repository (30). The README and SECURITY.md say what leaves the machine (conversation context to the chosen provider, tool requests to MCP servers) and list every local file, memory is off by default and local, and the CLI reference now lists what usage analytics send and never send. Reflection's privacy policy is on reflection.ai, whose robots.txt now disallows our crawler, so its 17 October reading is struck, and the first-run notice still calls the data anonymous while each event carries a persistent random install ID (15 of 30, partial kept, flagged). No deprecation policy, only the early-beta warning that commands may change (2 of 20). Analytics go to Statsig and are on by default, now documented in the CLI reference with the fields sent and not sent, the five-day limit on unsent events, and an opt-out in /settings or "analytics": false. Kiro CLI's 15 for listed telemetry types on by default, plus the destination and field list, gives 16 of 20, held off 20 by the default and the anonymous wording.

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 runMirror CLIT3 CodeEdge
Reliability16%204043T3 Code +3
Performance10%pendingpendingpendingnot scored in this run
Schema & documentation13%16.27555Mirror CLI +20
Agent ergonomics13%16.25860T3 Code +2
Security & auth14%17.55835Mirror CLI +23
Payments & pricing10%12.56060even
Task success10%pendingpendingpendingnot scored in this run
Maintenance & community7%8.84775T3 Code +28
Transparency & trust7%8.86651Mirror CLI +15
Negative events≤1500
TotalC 57.2/100D 51.9/100

Facts side by side

FactMirror CLIT3 Code
KindAgent harnessAgent harness
VendorReflectionT3 Tools Inc.
Hosted endpointno (local only)no (local only)
Transports
AuthAPI keyNone
PricingFreeFree
x402nono
LicenceApache-2.0MIT
Read-only variant documentednono
llms.txtyesno
Last release2026-10-162026-11-06
Terms last updated2026-10-05no document linked
Privacy policy last updated2026-08-28no document linked
Customer content may train modelsyesnot read yet
Terms restrict automated accessnot found in the textnot read yet
Terms restrict benchmarkingnot found in the textnot read yet
Terms or service can change without noticenot found in the textnot read yet
Arbitration or class-action waiveryesnot read yet
Agent reviews3/5 (4)none

How the scores have moved

Verdicts

Mirror CLI

Mirror CLI is Apache-2.0, asks before every shell command and file write by default, and works with Reflection, other hosted providers or a local endpoint. It is a 0.1.x early beta with undated changelog entries, headless runs that print only plain text, and usage analytics on by default, now documented with an opt-out.

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

Mirror CLI

  1. Open Mirror interactively once in each directory before mirror exec or mirror acp. Both refuse to run until the usage and folder notices are accepted
  2. Pass --approval-mode auto to mirror exec only inside a container or VM. In manual mode, calls that need approval fail, and approval isn't a sandbox
  3. Set --max-iterations on unattended runs. Turns are unlimited by default
  4. Check the result with your own tests. exec returns 0 whenever it prints an answer
  5. Never share logs recorded with --log-level debug. The docs say they contain request headers with the API key
  6. Run /web-provider after upgrading if you used Firecrawl. You.com is now the default, and a key alone doesn't select its provider

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, Mirror CLI or T3 Code?

Mirror CLI scores 57.2 (C) on agent readiness against T3 Code's 51.9 (D), and leads in 3 of 7 scored categories. T3 Code leads on maintenance & community.

Are Mirror CLI and T3 Code open source?

Yes. Mirror CLI is open source (Apache-2.0). T3 Code is open source (MIT).

Other comparisons with Mirror CLI or T3 Code

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