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What this plugin gives your agent

The official DeepSeek Harness ctx.lsp seam covers navigation (go-to-definition, references, implementation, hover). dsh-lsp-actions completes the action surface — the feedback loop an agent needs while it writes and fixes code:

Tool	What it does	Writes?
lsp_diagnostics <file>	Compiler/analyzer errors, warnings and hints with severity, range, message and source server	❌ read-only
lsp_format <file> [range?]	Formats a file or selection through the language server and applies the result, returning the diff	✅ via fs/write-intent + sandbox policy
lsp_completion <file> <line> <character>	Completion suggestions at a cursor position, including the actual insertion text	❌ read-only
lsp_code_action <file> [range?] [only?]	Server-verified quickfixes/refactorings (with their edits) for a range or the first diagnostic	❌ reference-only
lsp_symbols <query?> <file_path?>	Workspace-wide symbol search by name, or one file's symbol outline	❌ read-only
lsp_signature <file> <line> <character>	Signature help (parameters and documentation) inside a call	❌ read-only
lsp_inlay_hints <file> [range?]	Type annotations and parameter-name hints from the server	❌ read-only
lsp_rename <file> <line> <character> <new_name>	Server-verified symbol rename, applied workspace-wide with per-file diffs	✅ via fs/write-intent + sandbox policy

✨ A real typescript-language-server run is part of the test suite: diagnostics, formatting, completion, symbol search, and rename are verified end-to-end against a live server, not just mocks. The suite is self-contained (tsls is a devDependency) and runs in CI on Node 22/24 across Linux, Windows, and macOS.

Quick start

dsh plugin --profile <name> add dsh-lsp-actions

Remove it with:

dsh plugin --profile <name> remove dsh-lsp-actions

Configure one entry per language server (the shape mirrors the official lsp-stdio config):

# in your profile's cordis.patch.yml (or the bundle row)
- insert:
    - id: lsp-actions
      name: dsh-lsp-actions
      inject: [tools, fs, subprocess]
      config:
        servers:
          ts:
            command: typescript-language-server
            args: [--stdio]
            extensionToLanguage:
              ".ts": typescript
            formattingOptions: { tabSize: 2, insertSpaces: true }
          py:
            command: pyright-langserver
            args: [--stdio]
            extensionToLanguage:
              ".py": python
        maxDiagnostics: 200
        maxCompletionItems: 20
        maxCodeActions: 50
        maxSymbols: 100
        maxSignatures: 10
        maxInlayHints: 200
        maxResultChars: 16000
        timeoutMs: 60000

The eight tools are always registered. With an empty servers table and no ctx.lsp seam mounted, calls fail loudly with LSP_ACTION_UNAVAILABLE telling the user what to configure — the plugin never starts servers you did not configure. A ctx.lsp seam mounted after this plugin is picked up on the next call (seam detection is per-call, so load order does not matter).

Why it is safe by construction

• Formatting and rename are real mutations, treated like write/edit. Every byte goes through the fs/write-intent waterfall (observation → guarded write → observation) and the per-call sandbox policy. lsp_rename pre-flights every edited file (workspace containment, overlap check, byte-capped read) before the first write, so a bad server response cannot leave a half-applied rename.
• Everything else is read-only by design. Code actions, completions, symbols, signatures, and hints are reported as reference material; applying them is the model's own write/edit decision. Command forms are reported and never executed.
• Read-only sessions fail loud, fast, and structured — LSP_ACTION_READ_ONLY with the shared [sandbox: …] marker, raised before any server round-trip.
• Escalation matches the official tools. Under a confining filesystem, lsp_format and lsp_rename advertise the same sandbox_permissions / justification one-shot retry as write/edit, resolved through ctx.approval.
• Conflicts never clobber. If the file changed on disk after it was read, the guarded write fails with LSP_ACTION_CONFLICT and the model is told to choose: re-read and re-run, or apply the diff manually.
• Timeouts are the platform's. Each tool declares timeoutMs; the official dsh-tool-call-timeout-policy enforces it, and every await honors exec.signal.
• Nothing is cached. Results live only in the session log; there is no cross-session persistence.
• Bad servers fail loudly. A missing executable fails at load; a server that dies at startup fails the call with LSP_ACTION_SERVER_FAILED plus its stderr tail (after one fresh-spawn retry).

Architecture

Actions run official-seam-first and fall back to the plugin's own minimal stdio client:

lsp_diagnostics / lsp_format / lsp_completion / lsp_code_action /
lsp_symbols / lsp_signature / lsp_inlay_hints / lsp_rename
        │
        ▼
   ctx.lsp seam (extended: diagnostics / formatDocument / completion)
        │  absent · legacy · no provider for this file
        ▼
   built-in stdio client  ←  servers table (ctx.subprocess.spawn + JSON-RPC)

The seam extension is proposed upstream (upstream/lsp-action-seam.patch, PR description in upstream/PR-description.md). Once it lands, the plugin keeps working unchanged — the built-in client simply stops being used. The built-in client stays as the standalone fallback for the servers table. Full research and design notes: docs/seam-extension-notes.md.

Configuration reference

interface Config {
  /** Named language servers; empty = the plugin's own client serves nothing. */
  servers?: Record<string, LspServerEntry>
  maxDiagnostics?: number        // default 200
  maxCompletionItems?: number    // default 20
  maxCodeActions?: number        // default 50
  maxSymbols?: number            // default 100
  maxSignatures?: number         // default 10
  maxInlayHints?: number         // default 200
  maxResultChars?: number        // default 16000 (complete rendered result cap)
  maxDocumentBytes?: number      // default 4000000
  timeoutMs?: number             // default 60000 (enforced by the official timeout policy)
}

interface LspServerEntry {
  command: string                        // executable, resolved on PATH at load
  extensionToLanguage: Record<string, string>  // ".ts" → "typescript"
  fileGlobs?: string[]                   // optional; glob matches beat the extension map
  args?: string[]                        // no shell
  env?: Record<string, string>
  initializationOptions?: unknown
  configuration?: unknown                // object form answers workspace/configuration per section
  formattingOptions?: unknown            // e.g. { tabSize: 2, insertSpaces: true }
  maxMessageBytes?: number               // default 16000000
  maxStderrBytes?: number                // default 1000000
  killGraceMs?: number                   // default 2000
  shutdownTimeoutMs?: number             // default 5000
  diagnosticsSettleMs?: number           // default 2000 (push-only diagnostics window)
  diagnosticsDebounceMs?: number         // default 250 (quiet period after the last pushed batch)
  idleTimeoutMs?: number                 // default 0 (0 = keep the server process alive)
}

Error codes

Every failure carries a stable code on the error result; models and callers route on the code, never on message text.

Code	Meaning
LSP_ACTION_UNAVAILABLE	No server entry and no seam provider handles this file.
LSP_ACTION_UNSUPPORTED	The server (or seam provider) does not advertise the operation.
LSP_ACTION_SERVER_FAILED	The server failed (with its stderr tail); startup failures retry once.
LSP_ACTION_MALFORMED_RESPONSE	The server sent a structurally invalid payload.
LSP_ACTION_CONFLICT	The file changed since it was read, or the server's edits overlap / go out of bounds / leave the workspace.
LSP_ACTION_READ_ONLY	The session's sandbox mode forbids the formatting/rename write.
LSP_ACTION_WORKSPACE_REQUIRED	The calling session has no workspace cwd to root the server in.
LSP_ACTION_NO_SYMBOL	The server found no renameable symbol at the cursor position.

Host version support

The plugin declares its DeepSeek Harness packages as peer dependencies (@deepseek-ai/dsh-fs, dsh-llm, dsh-sandbox, dsh-subprocess, dsh-tools ≥ 0.1.0-rc.6), so one copy serves both the host and the plugin. Tested against 0.1.0-rc.6; last verified 2026-08-15.

Known limitations

• Transient documents. Every action opens the file, runs one request, and closes it again (matching the official stdio host). Project-based servers that require a resident open file for document-free requests (tsls refuses workspace/symbol without one) are served by passing file_path to lsp_symbols, which keeps the routing file open for that request. tsls also answers textDocument/signatureHelp with null under this lifecycle; other servers (gopls, pyright, rust-analyzer) serve it normally.
• Range formatting requires the server's range provider. Servers that only advertise whole-document formatting fail range requests with LSP_ACTION_UNSUPPORTED.
• Rename applies text edits only. Resource operations (create/delete/rename files) in a server's rename answer are refused with LSP_ACTION_UNSUPPORTED, and edits outside the workspace fail as LSP_ACTION_CONFLICT before anything is written. On utf-8/utf-32 servers, cross-file rename positions are decoded by reading each edited file; an unreadable edited file fails the call as a conflict instead of mis-decoding positions.

Development

pnpm install
pnpm run lint        # oxlint over src/ and tests/
pnpm test            # 240+ tests: unit + fixture-server integration + real tsls e2e
pnpm run test:coverage   # gates: lines/statements/functions ≥ 90%, branches ≥ 85%
pnpm build           # emits lib/

Releasing

CI runs the lint/build/test matrix plus the coverage gate on every push and pull request. Pushing a v* tag triggers the publish workflow, which verifies the suite and publishes the package to npm — it needs an NPM_TOKEN Actions secret (a publish-scoped npm access token) set once on the repository. The version is bumped manually in package.json/CHANGELOG.md before tagging.

Contributors

Thanks to everyone who has contributed to this project:

• PerryLink — the plugin itself: the LSP action client and server lifecycle, all eight tools, tests, CI, and documentation.

License

Apache License 2.0