Lsp Safe Edit

What it does

When your agent uses it

• Agent Workflows work in your project

Example prompts

• “/lsp-safe-edit”

Requirements

• Compatibility (from SKILL.md): Requires the agent-lsp MCP server (github.com/blackwell-systems/agent-lsp)
• Pre-approved tools (allowed-tools): mcp__lsp__start_lsp, mcp__lsp__open_document, mcp__lsp__get_diagnostics, mcp__lsp__preview_edit, mcp__lsp__simulate_chain, mcp__lsp__suggest_fixes, mcp__lsp__format_document, mcp__lsp__apply_edit, Edit, Write, Bash

Workflow steps

9 steps, taken from the step headings in SKILL.md.

1. 1Open target file(s)
2. 2Capture baseline diagnostics (BEFORE)
3. 3Speculative preview (preview_edit)
4. 4Apply the edit to disk
5. 5Capture post-edit diagnostics (AFTER)
6. 6Compute the diagnostic diff
7. 7Surface code actions if errors were introduced
8. 8Format (optional)
9. 9Report using DiagnosticDiffFormat

What it can do on your machine

Read from SKILL.md and the folder at commit 38ca488. It shows what the files ask for, not the result of running them.

• Tool permissions

  Pre-approves these tools, so the agent can use them without asking each time:

  • mcp__lsp__start_lsp
  • mcp__lsp__open_document
  • mcp__lsp__get_diagnostics
  • mcp__lsp__preview_edit
  • mcp__lsp__simulate_chain
  • mcp__lsp__suggest_fixes
  • mcp__lsp__format_document
  • mcp__lsp__apply_edit
  • Edit
  • Write

  …and 1 more on the same allowed-tools line.

  From allowed-tools in the SKILL.md frontmatter.

• Runs code

  No scripts in the folder and no shell commands in SKILL.md.

  From the folder's file list and the shell code blocks in SKILL.md.

• Network

  No URLs in SKILL.md.

  From URLs in SKILL.md, links to its own repository left out.

• Credentials

  Names no API keys, tokens, secrets or passwords.

  From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.

• Compatibility

  Requires the agent-lsp MCP server (github.com/blackwell-systems/agent-lsp)

  From compatibility in the SKILL.md frontmatter.

Context cost

Lsp Safe Edit loads about 2.5k tokens when it runs, and up to ~3k if it reads all its reference files. Until then it costs about 73 tokens; SKILL.md has 852 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it

~73

When it runs · the whole SKILL.md, loaded when a task matches

~2.5k

With references · SKILL.md plus every file in references/, read only if the agent opens them

~3k

Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.

Safety

• NotePre-approves every shell command (allowed-tools: Bash)SKILL.md

  allowed-tools: mcp__lsp__start_lsp, mcp__lsp__open_document, mcp__lsp__get_diagnostics, mcp__lsp__preview_edit, mcp

Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); files beside SKILL.md are not scanned.

SKILL.md

The full file from blackwell-systems/agent-lsp at commit 38ca488, republished under its MIT licence (© blackwell-systems). 852 words, ~2,467 tokens.

name

lsp-safe-edit

description

Wrap any code edit with before/after diagnostic comparison. Speculatively previews the change first (preview_edit), then applies to disk only if the error delta is acceptable. If post-edit errors appear, surfaces code actions for quick fixes. Handles single and multi-file edits.

allowed-tools

mcp__lsp__start_lsp, mcp__lsp__open_document, mcp__lsp__get_diagnostics, mcp__lsp__preview_edit, mcp__lsp__simulate_chain, mcp__lsp__suggest_fixes, mcp__lsp__format_document, mcp__lsp__apply_edit, Edit, Write, Bash

compatibility

Requires the agent-lsp MCP server (github.com/blackwell-systems/agent-lsp)

user-invocable

true

license

MIT

metadata.optional-capabilities

codeActionProvider documentFormattingProvider

mcp__lsp__open_document(file_path: "/abs/path/to/file.go", language_id: "go")

BEFORE = mcp__lsp__get_diagnostics(file_path: "/abs/path/to/file.go")

mcp__lsp__preview_edit(
  file_path: "/abs/path/to/file.go",
  start_line: <N>,
  start_column: <col>,
  end_line: <N>,
  end_column: <col>,
  new_text: "<replacement text>"
)

mcp__lsp__simulate_chain({
  "workspace_root": "/abs/path/to/workspace",
  "language": "go",
  "edits": [
    {
      "file_path": "/abs/path/to/file.go",
      "start_line": <N>, "start_column": <col>,
      "end_line": <N>,   "end_column": <col>,
      "new_text": "<replacement>"
    },
    // additional dependent edits (e.g. call site updates) ...
  ]
})

Edit(file_path: "/abs/path/to/file.go", old_string: "...", new_string: "...")

AFTER = mcp__lsp__get_diagnostics(file_path: "/abs/path/to/file.go")

mcp__lsp__suggest_fixes(
  file_path: "<file>",
  start_line: <error line>,
  start_column: 1,
  end_line: <error line>,
  end_column: 999
)

Errors introduced (2):
  file.go:34 — undefined: MyType
    → Code action: Import "mypackage" (quickfix)
  file.go:51 — cannot use int as string
    → No code actions available

Apply code actions? [y/n/select]

mcp__lsp__format_document({ "file_path": "/abs/path/to/file" })

mcp__lsp__apply_edit({ "workspace_edit": <TextEdit[]> })

## Edit Summary

Files changed: N
Errors introduced: A  →  Errors resolved: B  (net: A-B)
Warnings introduced: C  →  Warnings resolved: D

### Introduced errors
- file.go:34 — undefined: MyType

### Resolved errors
- file.go:12 — unused variable: x

© blackwell-systems, MIT. Rendered from Markdown: HTML in the file is shown as text, images as links, and headings moved down two levels. Raw file

Files

SKILL.md and 1 other file (references) in skills/lsp-safe-edit of blackwell-systems/agent-lsp.

• SKILL.md
• references/patterns.md

Open the folder on GitHubat commit 38ca488