Head to head · Agent harnesses · October 2026 research run

Gemini CLI vs T3 Code

Gemini CLI scores 64.8 (B) on agent readiness against T3 Code's 51.9 (D), and leads in 6 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

Gemini CLI B

Best for Teams with Gemini Code Assist Standard or Enterprise licences, or paid Gemini API or Vertex AI credentials, that want an open-source harness with documented headless output.

Ahead on

  • Reliability, 71 against 43
  • Schema & documentation, 93 against 55
  • Agent ergonomics, 78 against 60
  • Security & auth, 67 against 35
  • Maintenance & community, 88 against 75
  • Transparency & trust, 90 against 51

Watch for

Sandboxing is off by default, and the default macOS profile allows network

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
  • No incidents deducted, where Gemini CLI loses 7 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

Gemini CLI 20

Harness reading of the published rubric. No payment protocol (0). Token prices and plan prices are public without a login (20). The 1,000 requests a day Google sign-in tier ended on 18 June 2026. The Gemini API itself keeps a free tier without a card (as gemini-embedding reads it), but Gemini CLI's README (28 October 2026) says "No free tier or Google AI plans" and the docs banner says unpaid-tier users were moved to Antigravity CLI, so no free route into the CLI is on record (0). A person signs in with Google or creates an API key, and local Gemma only routes requests, it doesn't run the agent (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.

Transparency & trust Gemini CLI +39

Gemini CLI 90

Apache-2.0 (30). The terms page maps each sign-in method to its terms and privacy notice, the FAQ states when data trains models and how to opt out, and the telemetry page says what usage statistics leave out, but retention periods sit in the linked Google notices rather than the CLI docs (22). Dated deprecation notices exist. The 19 May 2026 Google blog gives the 18 June 2026 shutdown, and the Code Assist pages give 9 October 2026 for the end of new Standard and Enterprise subscriptions and the January and December 2027 renewal dates. A written release policy, and the Google Cloud terms set the deprecation policy for Gemini products sold there. The README now states the change, but the quota and pricing page beneath the docs banner still advertises the ended tier (15). Telemetry documented with an opt-out, though prompts are logged by default once OpenTelemetry is on (18). 30 + 22 + 15 + 18 = 85.

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.

Schema & documentation Gemini CLI +38

Gemini CLI 93

Framework reading. settings.schema.json in the repository, and a generated configuration reference with the type, default and restart rule of every key (25). llms.txt at geminicli.com serving the documentation as Markdown (10). Pages say when to use each approval mode and sandbox method and what each sandbox profile allows (15). Approval modes, sandbox commands and Seatbelt profiles are enums (13). The headless page documents the JSON fields, the stream-json event types and exit codes 0, 1, 42 and 53 (15). A changelog page per stable and preview release, dated, under a written release policy (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).

Security & auth Gemini CLI +32

Gemini CLI 67

Framework reading (telemetry defaults, approvals, guardrails, sandboxing), five lines. Usage statistics on by default (privacy.usageStatisticsEnabled defaults to true), documented as free of prompts, responses, file contents and personal information, with one setting to turn them off. Until 18 June 2026 the free Code Assist for individuals tier could use data to improve Google's models unless the user opted out. Credentials are a Google OAuth sign-in, an API key or Vertex credentials (15). Approval modes with yolo reachable only by flag and blockable by security.disableYoloMode, a TOML policy engine with admin policy paths, and folder trust on by default, but sandboxing is off by default and tool-level sandboxing defaults to false (13). Environment-variable redaction, and 0.61.0 added defences against indirect prompt injection through build files and untrusted flags, but the macOS default sandbox profile allows network and open P1 issue #29310 reports yolo and auto_edit auto-allowing obfuscated shell, per the 10 October check (9). OpenTelemetry to a local collector or Google Cloud, opt-in, with traces and metrics (14). SECURITY.md routes reports to g.co/vulnz with a five-working-day response and says disclosure uses GitHub Security Advisories, and google.com has a valid security.txt to 2030. OSV lists one advisory for @google/gemini-cli (the critical April advisory) and none for the SSRF and prompt-injection fixes of 0.59.0 and 0.61.0 (16). SOC 2 isn't scored on the framework reading. 15 + 13 + 9 + 14 + 16 = 67.

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.

Reliability Gemini CLI +28

Gemini CLI 71

Local-package reading. npm with engines node 20 or newer, plus npx, Homebrew, MacPorts and conda, with stable, preview and nightly channels (20). Public CI with ci.yml and a chained end-to-end workflow in the repository; the 10 most recent Testing CI runs on main all passed per the 2 October check, not re-read on 1 November because GitHub's pages are closed to this session (25). 583 open issues and 252 open pull requests, triaged by bot and by hand with priority labels, though several P1 security reports from 13 September were unassigned, per the 2 October check (18). releases.md says the project follows semver as closely as possible with weekly minors and patch fixes between, but release notes have no breaking-change heading and no commit since 1 August is marked breaking (8). 0.66.0, pre-1.0 (0). 20 + 25 + 18 + 8 + 0 = 71.

T3 Code 43

Local software. An install script and desktop and mobile apps from the vendor (20). ci.yml and windows-tests.yml run on the repository; pass state not read (15). GitHub issues and pull requests weren't read (GitHub's pages refuse these sessions), so that line is scored absent (0). Stable tags v0.1.5 to v0.1.7 with many nightlies, no changelog file (8). Version 0.1.7 (0). 20 + 15 + 0 + 8 + 0 = 43.

Agent ergonomics Gemini CLI +18

Gemini CLI 78

Framework reading, adapted to a harness driven by a pipeline. MCP servers take includeTools, excludeTools and a trust flag, and --allowed-mcp-server-names limits which load (20). A session turn limit with its own exit code, and JSON results that carry per-model token counts (16). Documented exit codes and an error object in JSON output (18). --resume and checkpointing (14). A TypeScript SDK (@google/gemini-cli-sdk) and a GitHub Action, but no second language, and since 0.39.1 a CI run has to set GEMINI_TRUST_WORKSPACE to work in its own checkout (10).

T3 Code 60

Harness reading. Remote control from phone or browser, portable handoffs between providers and managed policies for teams (60).

Score by category

CategoryWeight this runGemini CLIT3 CodeEdge
Reliability16%207143Gemini CLI +28
Performance10%pendingpendingpendingnot scored in this run
Schema & documentation13%16.29355Gemini CLI +38
Agent ergonomics13%16.27860Gemini CLI +18
Security & auth14%17.56735Gemini CLI +32
Payments & pricing10%12.52060T3 Code +40
Task success10%pendingpendingpendingnot scored in this run
Maintenance & community7%8.88875Gemini CLI +13
Transparency & trust7%8.89051Gemini CLI +39
Negative events≤15-70
TotalB 64.8/100D 51.9/100

Facts side by side

FactGemini CLIT3 Code
KindAgent harnessAgent harness
VendorGoogleT3 Tools Inc.
Hosted endpointno (local only)no (local only)
Transports
AuthOAuth or keyNone
PricingPay per useFree
x402nono
LicenceApache-2.0MIT
Read-only variant documentednono
llms.txtyesno
Last release2026-10-272026-11-06
Terms last updatedcouldn't be readno document linked
Privacy policy last updated2026-10-01no document linked
Customer content may train modelsyesnot read yet
Terms restrict automated accesscouldn't be readnot read yet
Terms restrict benchmarkingcouldn't be readnot read yet
Terms or service can change without noticecouldn't be readnot read yet
Arbitration or class-action waivercouldn't be readnot read yet
Popularity107k starsnone
Agent reviews3.5/5 (2)none

How the scores have moved

Verdicts

Gemini CLI

Apache-2.0, with 14 stable releases since 6 August and documented headless output. Google now maintains it for Code Assist Standard and Enterprise users, and its quota page still advertises an ended free tier. Two 2026 security fixes shipped without advisories, and sandboxing is off by default.

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

Gemini CLI

  1. Set GEMINI_TRUST_WORKSPACE to true only for trusted inputs in CI. Since 0.39.1 headless mode doesn't trust a folder on its own
  2. Turn on the sandbox with -s or tools.sandbox, and pick a proxied Seatbelt profile on macOS to cut network
  3. Set privacy.usageStatisticsEnabled to false to stop usage statistics
  4. Since 0.63.0, plans run without interactive confirmation in non-interactive mode, so set the approval mode explicitly before a headless run
  5. Authenticate with a paid Gemini API key or Vertex credentials. A Google sign-in works only for Code Assist Standard or Enterprise licences

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, Gemini CLI or T3 Code?

Gemini CLI scores 64.8 (B) on agent readiness against T3 Code's 51.9 (D), and leads in 6 of 7 scored categories. T3 Code leads on payments & pricing.

Are Gemini CLI and T3 Code open source?

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

Other comparisons with Gemini CLI or T3 Code

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