DeepSeek Harness Connector for VS Code (v0.0.3)

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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 v0.0.3

Diff Review, Approval Workflow & File Context Inlining — closes the biggest experience gap with Cursor/Cline: code changes can now be reviewed and approved entirely inside VS Code.

• Diff Review & Inline Code Application — When the agent writes or edits files, a review card appears in the sidebar showing each changed file with +added/-removed line counts. Click Diff to open VS Code's native diff editor. Accept (keep) or Reject (safe revert via git checkout) per-file or all at once.
• Approval Workflow Integration — approval/requested events now render inline as cards with Allow once / Deny buttons. No more switching to the browser to approve. A security allowlist restricts which tools can be approved from VS Code; high-risk operations still require the Web UI.
• @file Content Inlining — File references (@file:path or @file:path:L10-L20) now have their content read and inlined directly into the user message, guaranteeing the agent can see file content. Context metadata (active file, selection) is only sent on the first prompt of a session.
• Context Menu Integration — Right-click a file in the explorer → Add to Harness Chat. Select text in the editor → right-click → Send Selection to Harness. Both use workspace-relative paths.

See CHANGELOG.md for the full diff.

Previous releases

• v0.0.2 — Conversation UX & Architecture Baseline: Assistant Markdown rendering, tool card merging, system message collapsing, lazy workspace/session creation, streaming render fix, architecture hardening.
• v0.0.1 — First public release: prove VS Code and the browser share the same Harness session.

What v0.0.3 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).
• Review agent code changes — diff cards with per-file Accept/Reject, native VS Code diff editor, bulk Accept All / Reject All.
• Approve or deny agent actions — inline approval cards with Allow once / Deny buttons (security allowlist enforced).
• Attach file context — use @file:path or @file:path:L10-L20 in your prompt; file content is read and inlined automatically. Right-click in explorer or editor for quick insertion.
• 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 v0.0.3 deliberately does NOT do

For your safety, the following remain out of scope:

• No commands/execute, no credentials or settings API.
• No model switching.
• No inline completion, terminal/LSP integration.
• High-risk approvals (e.g. bash with untrusted input) cannot be allowed from VS Code — the card shows "Review in Web UI".
• 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.

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-0.0.3.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. Attach file context — type @file:src/main.ts or right-click a file in the explorer and choose Add to Harness Chat. Select text in the editor, right-click, and choose Send Selection to Harness for line-range references.

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

Configuration

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)

Context menu actions

• Add to Harness Chat (explorer right-click) — inserts @file:<relative-path> into the chat input.
• Send Selection to Harness (editor right-click, requires selection) — inserts @file:<relative-path>:L<start>-L<end> into the chat input.

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-0.0.3.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.
• Diff review revert uses git checkout — uncommitted changes to the target file will be lost on Reject.

Roadmap (v0.0.4+)

• Inline Completion
• VS Code filesystem provider
• Terminal integration
• LSP / ACP integration
• Image attachments

License

MIT