Letta vs OpenCode

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.

OpenCode 60

Harness reading of the framework checklist, used for all five harnesses in this batch. 30 for what leaves the machine by default, 20 for approvals and sandboxing, 15 for prompt-injection posture, 15 for audit and 20 for the security programme. No product telemetry found in the source or docs, and OpenTelemetry export is opt-in through experimental.openTelemetry. It fetches the model list from models.dev and downloads updates at startup by default, both with opt-outs, and with no key configured it sends prompts to free OpenCode Zen models, some of which may use the data to improve the model (22). Allow, ask or deny per tool with glob patterns, .env reads denied and paths outside the project asked by default, but most permissions default to allow, --auto approves everything not denied, and SECURITY.md says the permission system is not a sandbox (9). SECURITY.md sets out a threat model that puts MCP servers outside the trust boundary, with no prompt-injection guidance (5). Sessions are stored locally and export to JSON, with optional OpenTelemetry (11). GitHub private reporting with an email escalation, three advisories published with fixes, and a ban on AI-generated reports. No security.txt (13). CVE-2026-88624 (published 22 September, CVSS 9.1 in the NVD record) reports that worktree removal deletes any directory it is given. In 1.19.5, as in 1.19.3, Worktree.remove still deletes an existing path that isn't a registered worktree. The call needs access to the server API, which SECURITY.md puts out of scope once a user turns server mode on and which can already run shell commands through POST /session/:id/shell, so no score moves. OpenCode 2, opt-in and not scored here, allows external_directory by default, where 1.x asks.

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.

OpenCode 88

A JSON Schema for the config file at opencode.ai/config.json, and an OpenAPI 3.1 spec for the 1.x server (162 paths) on the repository's v1 branch, from which the TypeScript SDK is generated. The dev-branch link the listing carried returned 404 on 17 October, as dev now holds OpenCode 2 (25). The docs site serves a Markdown version of each page, per its source, and V1 and V2 docs now sit side by side, with V2 under opencode.ai/v2/docs (10). Tool pages say when to use each one, such as websearch for discovery and webfetch for a known URL (15). Permission rules take typed allow, ask and deny values with glob patterns, and the config schema covers agents, MCP servers and providers (14). Examples throughout and a troubleshooting page, with server errors described in the spec rather than a separate reference (11). A dated changelog at opencode.ai/changelog and GitHub releases (13).

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.

OpenCode 71

MIT (30). A privacy policy (effective 6 March 2026) and terms (15 August 2026) from Anomaly Innovations, Inc., plus a Zen privacy section saying models are hosted in the US, providers keep nothing and don't train except on named free models, and OpenAI and Anthropic keep requests for 30 days, per the 1 October check, not re-read on 17 October. The general retention line is as long as necessary (22). Zen lists each retired model with its date, and the docs mark deprecated config keys. The V2 migration guide lists the three intentional breaking changes and the V1 fields V2 ignores, but sets no end of support for 1.x (15). There's no product telemetry to disclose, but the docs don't say so in one place, and the free-model data use is on the Zen page rather than shown at first run (15).

Letta 58

Local-software lines, read for the harness. @letta-ai/letta-code on npm with Node.js 22.19 or newer, and PyPI wheels for glibc Linux, macOS 14 and Windows x64 with Python 3.9 or newer stated (20). ci.yml, nightly update smoke tests and Telegram live smoke tests exist, but GitHub's API answered with a rate limit, so run results were unread (15 of 25, unchecked). 332 open issues and pull requests, mostly pull requests; recent bug reports such as recall reading the wrong conversation have no reply yet (15 of 25). 398 tags at 0.34.x with release notes on GitHub, no changelog file, and breaking removals such as AgentFile announced in the README (8 of 15). Pre-1.0 (0). Total 58.

OpenCode 72

Read as a local package, graded on the 1.x line that npm i -g opencode-ai and the opencode.ai/install script put on a machine. opencode-ai 1.19.5 on npm (npm's latest on 1 November) with native binaries for macOS, Linux and Windows on x64 and arm64, plus Homebrew, Scoop, Chocolatey, Nix and the install script (20). A test workflow runs on the repository. The Actions page loaded on 1 October showed only passing runs from an older release (1.3.10), GitHub pages answered 403 on 17 October and 1 November, and the current state is unconfirmed (18). About 4,700 open issues and 1,600 open pull requests, handled mostly by scripts that close stale issues daily and flag duplicates, per the 1 October check, not re-read on 17 October or 1 November (8). Releases come almost daily with notes on GitHub and a changelog page. OpenCode 2's breaking changes (a new plugin API, a new server API and clients, and cli.json in place of tui.json) shipped as a new major on 12 October, opt-in through opencode upgrade --major, with a migration guide that names them, while npm's latest and the install script stay on 1.x. The 1.19.4 and 1.19.5 commits change no SDK code and mark no breaking change, but the 1.x release notes weren't read for a breaking-change section (11). 1.19, stable (15).

Letta 67

Harness reading. Toolsets switch with /model, skills load per agent, and subagents run in the background (18 of 25). Context is managed through memory blocks, reflection and dreaming (12 of 20). letta -p --output-format json for scripted runs and an App Server for programmatic control (12 of 20). Conversations resume by agent and conversation id, and memory is git-tracked so changes can be reverted (15 of 20). Runs with no account on the local backend, with one SDK language, TypeScript (10 of 15). Total 67.

OpenCode 79

Harness reading of the framework line, scored on what an agent or pipeline driving it has to supply. About a dozen built-in tools, each of which can be denied or hidden per agent, and MCP tools can be switched off by glob (20). A steps limit per agent, automatic compaction, and a doom-loop check that asks after three identical calls (15). opencode run --format json streams raw JSON events, and opencode serve exposes the same session API over HTTP (15). Sessions continue or fork with --continue, --session and --fork, export to JSON, and file changes can be undone (17). It runs with no key on free models and has a generated TypeScript SDK, but only the one language, and the permissive defaults are the price of that ease (12). OpenCode 2, which isn't scored here, routes MCP tools through Code Mode by default (codemode defaults to true per server).