git:20260920.15599f0 to git:20261008.3a1e352

# Desktop Agent Notes

## Frontend And Host Compatibility

- The desktop frontend and host are versioned and shipped together. Do not

support a current frontend talking to an older desktop host.

- Evolve desktop protocol payloads, the frontend, and the host in lockstep. Do

not make fields optional, hide controls, or add capability detection solely

for compatibility with a pre-change host unless the user explicitly asks for

it.

## Development Builds

- The supported development build is the packaged `.dev` application

(`package/build.mjs` with the development project config, e.g.

`dist/SeekMoonDev.app`). It runs the same packaged layout as a release —

`seekmoon/web` for the frontend, the per-user runtime dir for state — and

differs only by its identity suffix and the development-only behavior gated

on it.

- The unpackaged launch — `just desktop-dev` / `package/dev`, `proton dev`,

`desktop-dev.html`, `@development.Layout`, `desktop/target/dev-state` — is

deprecated and no longer supported. Do not design for it, review against it,

or fix issues that only reproduce under it; code that exists only to serve

it may be removed.

## Child Processes

- For a one-shot command that collects stdout and stderr but must not read

input, use `@processx.collect_output_no_stdin` from

`desktop/backend/internal/processx` instead of `@process.collect_output`.

- `collect_output_no_stdin` gives the child a valid stdin handle that is

already at EOF and always suppresses creation of a console window. Both are

required for Windows GUI builds: inheriting a missing standard-input handle

makes process creation fail, while launching a console application without

suppression flashes a visible console window.

- Do not use it for interactive commands, long-lived protocol processes, or

commands that receive a real stdin pipe, file, or PTY.

## JSON Protocol Codecs

- Never use `derive(FromJson)`, `derive(ToJson)`, or a combined

`derive(FromJson, ToJson)` anywhere under `desktop/`.

- Every type crossing a JSON boundary must provide explicit `FromJson` and

`ToJson` implementations. The decoder must deliberately specify the behavior

of required, missing, `null`, malformed, and unknown fields; the encoder must

deliberately specify which optional fields are omitted.

- When modifying an existing Desktop protocol type that still derives either

JSON trait, replace that derived codec with explicit implementations in the

same change.

## Desktop Trust And Security Model

- A frontend connected and authenticated to a Desktop instance is trusted with

the authority of the local user. This includes the Proton renderer, an

authenticated relay frontend, and code the user runs in that frontend's

DevTools.

- The connected frontend can already invoke Desktop terminal and shell

operations. Letting the same frontend select a working directory or send an

app-server execution-policy field is therefore not, by itself, a privilege

escalation or a Desktop security-boundary violation.

- The security boundary is before a frontend obtains an authenticated Desktop

command channel. Unauthenticated network peers, unrelated web origins,

repository content, model output, and other displayed data are not trusted

principals and must not acquire command authority merely by being processed

or rendered.

- Continue validating command payloads for type safety, protocol correctness,

product invariants, and protection against accidental destructive actions.

Workspace and path checks may enforce product scope, but they do not sandbox

a trusted frontend that can already spawn a shell.

- Prefer typed request and response models at Desktop command boundaries. They

document the protocol, reject malformed data, and expose schema drift during

development; do not justify them as a privilege boundary against the trusted

frontend.

- A security finding must name the less-trusted principal and the new capability

it gains. Do not report a privilege escalation solely because a trusted

frontend can craft fields that the normal UI does not expose.

- The local user and whatever they choose to run are one principal. A branch

the user checked out and built, its hooks and build scripts, any process

running under their account, a development build, and the DevTools console

all already act with the user's authority. A finding whose attacker is "a

branch the developer checked out", "a file in the checkout", or "a process

on the developer's machine" names no less-trusted principal and is not a

security finding.

- "Repository content is untrusted" means the host must not grant command

authority to content it processes as data — rendered Markdown, diffs, file

previews, tool output, model output. It does not apply to code the user

runs on purpose; checking out and building a branch is running its code.

- Release and development builds share this one model. A development build

differs in the surfaces it exposes, not in who is trusted: a development-only

surface such as the loopback console is judged by the same two-principal

test. Loopback binding limits reachability, not identity — a web page from

another origin can reach loopback — so such a surface fences web origins

with a launch token, a session cookie, and an `Origin` check, and does not

need to defend against processes already running as the user.