Kiro CLI vs Letta

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.

Letta 35

Harness reading of the framework checklist, as for the other harnesses. 30 for what leaves the machine by default, 20 for approvals and sandboxing, 15 for injection posture, 15 for audit and 20 for the security programme. Letta Cloud is the default backend, so agent state and conversations go to Letta's servers, and telemetry is on by default (10 of 30). The default permission mode is unrestricted; standard, acceptEdits and strict are opt-in, and cloud sandboxes exist for remote work (4 of 20). No prompt-injection guidance found for fetched pages or channel messages (5 of 15). Conversation search and git history of memory give an operator a record of what the agent saw and changed (10 of 15). SECURITY.md routes reports to support@letta.com and scopes out the retired server; no security.txt, bounty or certification found (6 of 20). Total 35.

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).

Letta 60

No x402, MPP or L402 (0 of 40). Per-unit API prices are public, $0.10 per active agent a month and $0.00015 a second of tool execution, plus plan prices (20). A $0 plan with bring-your-own keys; no card is mentioned (20). The CLI runs locally without signing in (20). Total 60.

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.

Letta 55

Apache-2.0 (30). The privacy policy has no date, no legal entity and no retention periods, and says hosted message data may train future models (8 of 30). The README and docs mark AgentFile, the Electron app and the V1 server as deprecated or retired, without dated notice periods (12 of 20). Telemetry is described in the privacy policy only as basic and opt-out when supported; the LETTA_CODE_TELEM=0 switch appears only in the source (5 of 20). Total 55.

Kiro CLI 73

3.0.0 on 3 November 2026, after 2.37.1 on 31 October (30). 25 dated releases from 2.17.0 on 11 August to 3.0.0 on 3 November, plus five patches, read from the first three changelog pages back to 9 July (20). A public issue tracker with area labels and triage automation, 69 cli issues closed against 96 opened in the 30 days to 8 October, and a Discord server, per the 8 October check, not re-read on 3 November. We didn't establish how many replies come from staff (14). No SDK and no registry entry. The ACP server is kept current, with ACP sign-in added in 2.37.0 and a migration guide for clients moving to V3 (6). Closed source, so no CI or dependency health to read. The installer verifies checksums (3). 30+20+14+6+3 = 73.

Letta 85

v0.34.42 on 6 November 2026 (30). Dozens of releases in 90 days (20). Pull requests are merged daily; recent issues from users have few replies (15 of 25). npm and PyPI packages and the Agent SDK track the releases (12 of 15). Lock files, CI and nightly smoke tests (8 of 10). Total 85.

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).

Letta 70

Harness reading. docs.letta.com serves llms.txt and a Markdown version of every page, with an applies_to block saying which backend and interface each page covers (10). TypeScript types for the Agent SDK and a documented App Server WebSocket protocol, but no JSON Schema or OpenAPI for the harness (15 of 25). Pages say when to use local or cloud backends, subagents and channels (14 of 20). Permission modes and options are typed in the SDK (12 of 15). Example applications and a remote client reference (11 of 15). Releases most days but no changelog file (8 of 15). Total 70.