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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 — reference-only hints, never executed	❌ read-only

✨ A real typescript-language-server run is part of the test suite: diagnostics, formatting, and completion are verified end-to-end against a live server, not just mocks.

Quick start

dsh plugin --profile <name> add <path-or-tarball-of-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
        maxResultChars: 16000
        timeoutMs: 60000

With an empty servers table and no ctx.lsp seam mounted, the plugin contributes nothing — it never starts servers you did not configure.

Why it is safe by construction

• Formatting is a real mutation, treated like write/edit. Every byte goes through the fs/write-intent waterfall (observation → guarded write → observation) and the per-call sandbox policy.
• 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 advertises 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. Diagnostics/completion 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.

Architecture

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

lsp_diagnostics / lsp_format / lsp_completion
        │
        ▼
   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. Full research and design notes: docs/seam-extension-notes.md.

Configuration reference

interface Config {
  /** Named language servers; empty = the plugin activates no servers. */
  servers?: Record<string, LspServerEntry>
  maxDiagnostics?: number        // default 200
  maxCompletionItems?: number    // default 20
  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                // static answer to workspace/configuration
  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)
}

Development

pnpm install
pnpm test          # 105 tests: unit + fixture-server integration + real tsls e2e
pnpm build         # emits lib/

License

Apache License 2.0