deepseek-harness/packages/host/directory-picker/README.md

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description: "Workspace-directory picking seam for the web GUI host: the service contract, capability vocabulary, and error codes the native and browse backends implement."

kind: "package-reference"

@deepseek-ai/dsh-host-directory-picker

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Summary

The web GUI lets an operator choose a workspace directory with either an OS chooser or an in-app browser. Use the native option when the operator can reach the host display; use the browser option for remote clients or when directory listing and creation must stay in the app. Consumers receive the interaction kind and can present the matching workflow. Directory picking is limited to the GUI host and never affects the agent loop. The browser workflow exposes one directory tree at a time; multiple roots are unsupported.

Table of Contents

• Use this package
• Understand the implementation
• Further Exploration
• Model Experience
• Known Limitations and Deferred Work
• Dev Note

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Use this package

Mount exactly one directory-picker backend and let the workspace flow drive it: the seam itself is only the service contract, so a composition without a backend has no way to pick a directory.

Choosing a backend

The native backend is the right choice when the operator sits at the host's display: directoryPicker/pick opens one OS chooser and returns the chosen absolute path, or null on cancel. The browse backend works everywhere — it lists one directory level and creates child directories from the browser, so remote clients that cannot reach an OS dialog still pick a workspace. When the host situation varies between boots, compose the adaptive chooser, which resolves the situation once at boot and mounts the matching backend.

The capability contract

capability() returns a discriminated union describing how an operator selects a directory: { kind: 'native', pick(signal) } for the OS chooser, or { kind: 'browse', list(path?), createDirectory(path, name) } for the in-app browser. Consumers switch on kind; a capability kind no composition implements means the UI hides the picking affordance rather than failing. Browse failures throw the typed DirectoryPickerError with a closed code set — directory-unreadable, directory-exists, or directory-create-failed — each carrying the subject path, which the picking Remote controller maps 1:1 onto wire failure codes.

What rows carry

DirectoryEntry rows expose the absolute path and a host-owned hidden flag (dot-prefixed on POSIX) so display policy stays client-side; clients never join path segments themselves. DirectoryListing.crumbs is the ancestor chain from the filesystem root to the listed directory — every crumb is a jump target, and the root crumb is labeled by its full path.

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Understand the implementation

Implementation internals — click to expand

### Design concept The seam is built on one separation: the interaction shape a backend provides is a contract, not an implementation detail. `DirectoryPicker` is an abstract Cordis service with a single `capability()` method; a backend subclass registers as `ctx.directoryPicker`, and loading a second implementation throws the standard duplicate-service error. The capability object must be stable for the service lifetime because consumers may capture it across calls. ### The merge-extensible vocabulary `DirectoryPickerCapabilities` is a merge-extensible map keyed by capability kind, and `DirectoryPickerCapability` derives the union from it. A new backend declaration-merges its shape here (the entry's `kind` literal must equal its key) instead of editing this package. Each backend package also ships a browser entrypoint that registers the matching interaction in ui-workspace's directory-flow slots, so one composition row selects both the host capability and the client flow. ### Source map | File | Role | |---|---| | [`src/index.ts`](src/index.ts) | Service Definition: abstract `DirectoryPicker`, capability vocabulary, typed error, Context merge | ### Failure vocabulary `DirectoryPickerError` carries a closed `DirectoryPickerErrorCode` plus the absolute subject path, so consumers map business codes without string matching. The seam Agent Note records the design rationale, the separation from `ctx.fs`, and the policy decisions.

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Further Exploration

Read these when the seam contract is not enough: the decision record first, then the two backends and the adaptive chooser that compose it.

• Directory-picker capability seam decision — design rationale, the ctx.fs separation, and the policy decisions.
• Native backend — the OS-chooser interaction and its platform tooling.
• Browse backend — the in-app listing and creation interaction for remote clients.
• Adaptive chooser — boot-time resolution between the two backends.
• Workspace subsystem — the workspace records the picked directory feeds.

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Model Experience

None, as the GUI-host picking seam registers nothing model-facing.

KV Cache effect

None; this package neither assembles nor sends a provider request.

Known Limitations and Deferred Work

These limits define when the seam contract leaves a decision to a future consumer. They are current package constraints, not a task backlog.

• No multi-root support — the browse contract exposes one ancestry chain per listing; per-deployment root scoping (and Windows drive-root enumeration above a drive) waits for a consumer that needs it, per the DirectoryPicker Agent Note.

Dev Note

Working context for maintainers — click to expand

None.

Runtime invariant: No companion is published. This stateless Service Definition owns the capability vocabulary, while backends and the Remote controller own observations.