DeepSeek Harness Connector for VS Code (v0.0.2)

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Native VS Code client for DeepSeek Harness.

Connect to your existing local Harness instance and continue the same workspaces and sessions directly inside VS Code.

Same Harness. Same Workspace. Same Session. VS Code Client.

This is not a Cursor replacement, a Claude Code replacement, or a full coding agent. It connects VS Code to your already-running local dsh web instance:

Browser ─────┐
             │
             ▼
       DeepSeek Harness
             ▲
             │
VS Code ─────┘

VS Code reads the workspaces and sessions the browser already has, and continues the same session — so a browser refresh of that session sees exactly what VS Code sent.

What's new in v0.0.2

Conversation UX & Architecture Baseline — the last direct-push release before PR-only mode.

• Assistant Markdown rendering — markdown-it (html: false) runs inside the webview. Code blocks, lists, tables, links all render. Unsafe HTML is dropped; links open with target=_blank rel=noopener.
• Tool cards merged — tool/call + tool/result are now a single collapsible ToolItem (by callId). No more pink result blocks. Click to expand Arguments + Result.
• System messages collapsed — SystemItem is its own kind (not a UserItem with a flag). Default UI is one collapsed line ▸ Runtime context · @deepseek-ai/dsh-system-prompt.
• Lazy workspace + session creation — open a repo, type a prompt, hit Send. Workspace and session are created automatically on first send. No confirmation modals.
• Streaming render fix — renderVersion monotonic counter ensures every model mutation triggers a webview re-render. Fixes the "streaming text changed but UI didn't update" bug.
• Architecture hardening — AppController owns orchestration; extension.ts is pure wiring; provider.ts split into styles/html/client/toolPresentation. Stable boundaries for future feature PRs.

See CHANGELOG.md for the full diff.

What v0.0.2 does

• Connect to a local dsh web (loopback only — 127.0.0.1 / localhost).
• Match the active VS Code folder to a Harness workspace. If none exists, the workspace is created lazily on first prompt — no modal.
• List the workspace's existing sessions.
• Open a session and render its history.
• Send a plain-text prompt to that session. If no session exists, one is created automatically.
• Stream the assistant's reply with Markdown rendering (code blocks, lists, tables, links).
• Show tool calls as collapsed cards with name-aware titles (Read src/foo.ts, Search "pattern", Run npm test).
• Hide plugin-injected system messages by default; toggle with the SYS button.
• Stop the active turn.
• Reopen the stream and refetch history on disconnect.
• "Open in Harness Web UI" command.
• Dock the view in the right side bar (like Chat) via the ⇲ button.

What v0.0.2 deliberately does NOT do

For your safety, v0.0.2 refuses to touch anything beyond read + prompt + cancel:

• No /api/respond, no approval allow/reject, no permission changes.
• No commands/execute, no credentials or settings API.
• No model switching.
• No diff review, file edits, inline completion, terminal/LSP integration.
• No second session database — the Harness Session is the only source of truth.
• No auto-install / auto-start / auto-upgrade of dsh.
• Does not fork or modify the Harness source.

If an action requires approval, VS Code only shows:

Action requires approval in DeepSeek Harness Web UI

and never responds on your behalf.

Requirements

• VS Code ≥ 1.85
• A running local dsh web (default port 3080). This extension does not start it for you.

Quick start

1. Start Harness locally:

   dsh web
   # → http://127.0.0.1:3080
   

2. Install from the VS Code Marketplace or via command line:

   code --install-extension lucasliang.harness-connector-deepseek
   

   Or install the VSIX from GitHub Releases:

   code --install-extension harness-connector-deepseek-0.0.2.vsix
   

3. Open a folder in VS Code that you want to bind to a Harness workspace.

4. The DeepSeek Harness activity-bar icon appears; the extension auto-connects. If your folder matches an existing Harness workspace, its sessions appear in the dropdown. Pick one and continue the conversation.

5. No matching workspace? Just type a prompt and hit Send — the workspace and session are created automatically.

6. Open the same session in your browser at http://127.0.0.1:3080/ — both surfaces see the same turn.

Configuration

Setting	Default	Notes
deepseekHarness.host	127.0.0.1	v0.0.x only allows 127.0.0.1 or localhost. Any other value is refused.
deepseekHarness.port	3080	The default dsh web port. Override if you started dsh web --port <n>.
deepseekHarness.showSystemMessages	false	Show plugin-injected system messages (runtime context, approval notices). Hidden by default; toggle live with the SYS button in the webview header.

Commands

• DeepSeek Harness: Connect / Disconnect
• DeepSeek Harness: New Session (in the active workspace)
• DeepSeek Harness: Refresh Sessions
• DeepSeek Harness: Move to Right Side Bar — dock the view in the secondary side bar (like Chat) so it stops competing with the file explorer. Also available via the ⇲ button in the webview header.
• DeepSeek Harness: Open Web UI
• DeepSeek Harness: Show Logs (the DeepSeek Harness output channel)

Architecture

See ARCHITECTURE.md for the one-page design and the protocol contract. (中文版: ARCHITECTURE.zh-CN.md)

Protocol fixtures

test/fixtures/ holds sanitized captures of the live wire format, useful for detecting upstream Harness protocol drift:

• host-describe.json, workspace-list.json, session-list.json, session-history.json, session-prompt.json, session-event.json

No credentials, API keys, or real prompt content are stored — only the JSON shapes (text fields are redacted).

Protocol spike

A standalone Node script validates the full loop against your running dsh web:

npm run spike            # read-only validation (connect / list / history / mux open)
npm run spike -- --prompt  # also exercises prompt + live events + cancel

Development

npm install
npm run build        # esbuild → dist/extension.js
npm run watch        # rebuild on change
npm run typecheck
npm run package      # → harness-connector-deepseek-0.0.2.vsix

Press F5 in VS Code to launch an Extension Development Host with the extension loaded.

Verified against

• DeepSeek Harness host v0.0.1 (@deepseek-ai/dsh-root), default dsh web port 3080.
• Wire contract: packages/host/apiproxy/src/api/ (authoritative).

Limitations

• Loopback only — no remote / LAN / WSL-bridged hosts.
• Text prompts only (no image attachments).
• History loads the last ~50 messages; "load older" is a future feature.
• Session deep-links in "Open Web UI" are intentionally not guessed — only the Harness home opens.
• Unknown harness event types are ignored (the protocol is merge-extensible); they do not crash the client but also do not render.

Roadmap (v0.0.3+, via feature PRs)

• Diff Review
• Approval integration
• Inline Completion
• VS Code filesystem provider
• Context injection

License

MIT