Head to head · Agent harnesses · October 2026 research run

Kiro CLI vs T3 Code

Kiro CLI scores 59.8 (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

Kiro CLI C

Best for Teams on AWS that want one agent configuration across terminal, IDE and web, with central permission policy, prompt logging to their own S3 bucket and IAM Identity Centre sign-in.

Ahead on

  • Reliability, 57 against 43
  • Schema & documentation, 79 against 55
  • Agent ergonomics, 67 against 60
  • Security & auth, 69 against 35
  • Transparency & trust, 71 against 51

Also in its favour

  • Free to start without a card

Watch for

Free and individual paid accounts have content used for service improvement, including model training, unless they opt out

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 40

Also in its favour

  • No key needed to call it
  • Open source
  • No incidents deducted, where Kiro CLI 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.

Security & auth Kiro CLI +34

Kiro CLI 69

Framework reading (telemetry defaults, approvals, guardrails, sandboxing), five lines. Telemetry and content collection are on by default for Free and individual accounts, each with a documented opt-out, and enterprise users are opted out. API keys are long-lived and revocable with no scopes, and administrators must switch key generation on (14). Deny over ask over allow across six scopes, hard-coded denies on Kiro's own settings paths, workspace trust and a managed policy that fails closed. V3 is the default since 3.0.0 (3 November 2026), interactive V3 sessions ask before loading a folder's hooks, agents and MCP servers since 2.33.0, and /sandbox puts agent shell commands and local stdio MCP servers in an operating-system sandbox. The sandbox is off unless chosen and doesn't cover the agent, built-in file tools or remote MCP servers, and AWS says managed policies are client-enforced and can be circumvented (17). An untrusted workspace doesn't load its agents, steering, MCP configuration or skills, compound shell commands are split before matching, and the MCP page warns that servers run outside any sandbox (11). Enterprise prompt logging to the customer's S3 bucket covers the CLI, with daily activity reports and OpenTelemetry export, and individuals have local logs only (11). AWS vulnerability reporting through a HackerOne disclosure programme with no paid bounty, CVEs published in security bulletins with credit to reporters, ISO/IEC 27001:2022 scope and HIPAA eligibility. The aws.amazon.com security.txt is valid (Expires 2027-10-16) and kiro.dev/.well-known/security.txt answers 404, so 2 are held back for that and 2 for no bounty (16). 14+17+11+11+16 = 69.

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 Kiro CLI +24

Kiro CLI 79

Framework reading. A command reference, a settings reference, an exit-code page and a documented rule format for permissions, plus the Agent Client Protocol methods the CLI implements. No published schema for the stream-json events was found (14). kiro.dev/llms.txt indexes every docs page and each has a Markdown twin, though robots.txt disallows both for crawlers (10). The permissions page states the defaults, what each preset allows and when to pick it, and that headless runs treat ask as deny (16). Rules are validated, an unknown preset rejects the session request, and a malformed managed policy fails closed (12). CI examples, exit codes 0, 1, 3 and 4 and hook exit codes are documented, but code 1 covers every other failure (12). Versioned releases with a dated changelog and a 2.x reference kept beside V3 (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).

Payments & pricing T3 Code +20

Kiro CLI 40

Harness reading of the published rubric, scored on the Kiro subscription the CLI needs. No payment protocol (0). Plan prices, the $0.04 credit price and per-model credit multipliers are public without a login (20). Kiro Free has 50 credits a month, and the pricing page asks for a card only on upgrade (20). A person signs in through a browser or device flow, and the API key for headless runs is created by hand at app.kiro.dev on a paid plan (0).

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 Kiro CLI +20

Kiro CLI 71

Proprietary, with clear terms. The licence page puts the CLI under the AWS Customer Agreement and the AWS Intellectual Property Licence, where the Amazon Q Developer CLI it replaced was Apache 2.0, per the 8 October check (15). The data protection page (updated 23 October 2026) says what is stored for Free, individual and enterprise users, names US East (N. Virginia) for storage, and gives 60 days for Free Tier abuse detection and 30 days for some models. It agrees with sections 50.3 and 50.14 of the AWS Service Terms, read on 8 October. No general retention period for stored content was found (22). The models page has a model lifecycle section with Experimental, Active and EOL stages and dates, and Claude Sonnet 4 ended on 14 October 2026. 3.0.0 made V3 the default as 2.30.0 announced and retired the Classic interface 34 days after the 2.26.0 deprecation notice, but the desktop app and inline autocomplete were retired in the same release with no earlier notice found, and no minimum notice period is stated (14). Telemetry types are listed and kiro-cli settings telemetry.enabled turns them off, with collection on by default. The data protection page's CLI steps still point to the desktop app's Preferences, which 3.0.0 retired (15). 15+22+14+15 = 66.

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.

Reliability Kiro CLI +14

Kiro CLI 57

Local-package reading, the same as the other closed-source harnesses. An install script that verifies SHA-256 checksums, a .deb, an AppImage and a PowerShell script, with macOS, Windows 11 and Linux (glibc 2.34 or newer, or musl) stated, per the 8 October check (20). No public CI or test suite, since the source isn't published and the GitHub repository is an issue tracker whose newest commit is 27 August (0). Per the 8 October check, not re-read on 3 November, 1,401 open issues in the shared Kiro tracker, 428 labelled cli, with 96 cli issues opened and 69 closed in the 30 days to 8 October, area labels, a triage label and stale-issue automation (12). A dated changelog for every release, and 3.0.0 lists its breaking changes under their own heading with a migration route, though 2.24.0 stopped loading project .env files in a minor version (10). 3.0.0 on 3 November 2026 makes V3 the default engine (15). 20+0+12+10+15 = 57.

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 Kiro CLI +7

Kiro CLI 67

Framework reading, adapted to a harness driven by a pipeline. --trust-tools limits approved tools, disabledTools removes MCP tools per server, tool search loads MCP tools on demand, and custom agents carry their own tool set (20). Compaction and a workflow timeout (KIRO_HEADLESS_WORKFLOW_TIMEOUT_SECS, six hours by default) exist, but no cap on turns or run time for a plain headless run was found (10). Distinct exit codes for MCP startup failure and a missing agent, --require-mcp-startup, and a final interruption record in stream-json, with exit 1 for everything else (14). Sessions are saved every turn, with --resume, --resume-id and checkpoints with rewind (15). No SDK. The programmatic interfaces are the headless command and the ACP server, and a headless run needs a paid-plan API key and explicit trust flags (8).

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 runKiro CLIT3 CodeEdge
Reliability16%205743Kiro CLI +14
Performance10%pendingpendingpendingnot scored in this run
Schema & documentation13%16.27955Kiro CLI +24
Agent ergonomics13%16.26760Kiro CLI +7
Security & auth14%17.56935Kiro CLI +34
Payments & pricing10%12.54060T3 Code +20
Task success10%pendingpendingpendingnot scored in this run
Maintenance & community7%8.87375T3 Code +2
Transparency & trust7%8.87151Kiro CLI +20
Negative events≤15-50
TotalC 59.8/100D 51.9/100

Facts side by side

FactKiro CLIT3 Code
KindAgent harnessAgent harness
VendorAmazon Web ServicesT3 Tools Inc.
Hosted endpointno (local only)no (local only)
Transports
AuthOAuth or keyNone
PricingFreemiumFree
x402nono
LicenceProprietary. Licensed as AWS Content under the AWS Customer Agreement and the AWS Intellectual Property Licence (https://kiro.dev/license/). The GitHub repository is the public issue tracker and doesn't hold the sourceMIT
Read-only variant documentednono
llms.txtyesno
Last release2026-11-032026-11-06
Terms last updated2026-08-14no document linked
Privacy policy last updated2026-05-18no document linked
Customer content may train modelsnot found in the textnot 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
Popularity4.4k starsnone
Agent reviews2.8/5 (4)none

How the scores have moved

Verdicts

Kiro CLI

Permission rules follow deny over ask over allow, and since 3.0.0 (3 November 2026) the V3 engine with workspace trust is the default. Content from Free and individual paid accounts is used for service improvement, including model training, unless the user opts out, and October releases fixed approval and Windows search-path flaws with no security advisory.

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

Kiro CLI

  1. Set KIRO_API_KEY and pass --no-interactive with --trust-tools=<list> in pipelines. Keep --trust-all-tools for disposable environments
  2. Pass --require-mcp-startup when a run depends on MCP tools. Without it a failed server is logged and the run continues
  3. Run 2.34.0 or later. Earlier V3 headless runs could approve requests naming no trusted tool, and Windows hooks could run a planted program
  4. Run kiro-cli settings telemetry.enabled false and turn off content collection on Free and individual plans. Both are on by default
  5. Remove autocomplete, inline, translate, theme and dashboard from scripts, which 3.0.0 retired. Pass --v2 to keep the V2 agent

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, Kiro CLI or T3 Code?

Kiro CLI scores 59.8 (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 Kiro CLI and T3 Code open source?

No open-source release is listed for Kiro CLI. T3 Code is open source (MIT).

Other comparisons with Kiro CLI or T3 Code

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