Lsp Simulate

What it does

When your agent uses it

• Planning edits that might break things
• Exploring refactors across multiple files
• Verifying an edit is safe before applying

Example prompts

• “/lsp-simulate”

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__create_simulation_session, mcp__lsp__simulate_edit, mcp__lsp__simulate_chain, mcp__lsp__evaluate_session, mcp__lsp__commit_session, mcp__lsp__discard_session, mcp__lsp__destroy_session, mcp__lsp__preview_edit

What it can do on your machine

Read from SKILL.md and the folder at commit 6fa5faf. 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__create_simulation_session
  • mcp__lsp__simulate_edit
  • mcp__lsp__simulate_chain
  • mcp__lsp__evaluate_session
  • mcp__lsp__commit_session
  • mcp__lsp__discard_session
  • mcp__lsp__destroy_session
  • mcp__lsp__preview_edit

  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 Simulate loads about 1.8k tokens when it runs, and up to ~3.2k if it reads all its reference files. Until then it costs about 59 tokens; SKILL.md has 495 words of instructions outside code blocks.

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

~59

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

~1.8k

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

~3.2k

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

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 6fa5faf, republished under its MIT licence (© blackwell-systems). 495 words, ~1,812 tokens.

name

lsp-simulate

description

Speculative code editing session — simulate changes in memory before touching disk. Use when planning edits that might break things, exploring refactors across multiple files, or verifying an edit is safe before applying.

allowed-tools

mcp__lsp__start_lsp, mcp__lsp__create_simulation_session, mcp__lsp__simulate_edit, mcp__lsp__simulate_chain, mcp__lsp__evaluate_session, mcp__lsp__commit_session, mcp__lsp__discard_session, mcp__lsp__destroy_session, mcp__lsp__preview_edit

compatibility

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

user-invocable

true

license

MIT

mcp__lsp__start_lsp(root_dir: "/your/workspace")

mcp__lsp__preview_edit(
  workspace_root: "/your/workspace",
  language: "go",
  file_path: "/abs/path/to/file.go",
  start_line: 42, start_column: 1,
  end_line: 42, end_column: 20,
  new_text: "replacement text"
)

{ net_delta: 0 }   -- safe to apply
{ net_delta: 2 }   -- 2 new errors introduced; do NOT apply

mcp__lsp__create_simulation_session(
  workspace_root: "/your/workspace",
  language: "go"
)
→ { session_id: "abc123" }

mcp__lsp__simulate_edit(
  session_id: "abc123",
  file_path: "/abs/path/to/file.go",
  start_line: 10, start_column: 1,
  end_line: 10, end_column: 30,
  new_text: "func NewClient(cfg Config) *Client {"
)
→ { session_id: "abc123", edit_applied: true, version_after: 1 }

mcp__lsp__evaluate_session(
  session_id: "abc123",
  scope: "file"
)
→ {
    net_delta: 0,
    confidence: "high",
    errors_introduced: [],
    errors_resolved: [],
    edit_risk_score: 0.0,
    affected_symbols: []
  }

mcp__lsp__discard_session(session_id: "abc123")

-- Preview patch only (no disk write):
mcp__lsp__commit_session(session_id: "abc123", apply: false)

-- Write to disk:
mcp__lsp__commit_session(session_id: "abc123", apply: true)

mcp__lsp__destroy_session(session_id: "abc123")

mcp__lsp__simulate_chain(
  session_id: "abc123",
  edits: [
    { file_path: "/abs/file.go", start_line: 5, start_column: 1,
      end_line: 5, end_column: 40, new_text: "type Foo struct { Bar int }" },
    { file_path: "/abs/file.go", start_line: 20, start_column: 1,
      end_line: 20, end_column: 10, new_text: "f.Bar" },
    { file_path: "/abs/other.go", start_line: 8, start_column: 1,
      end_line: 8, end_column: 10, new_text: "x.Bar" }
  ]
)
→ {
    steps: [
      { step: 1, net_delta: 0, errors_introduced: [] },
      { step: 2, net_delta: 0, errors_introduced: [] },
      { step: 3, net_delta: 1, errors_introduced: [...] }
    ],
    safe_to_apply_through_step: 2,
    cumulative_delta: 1
  }

-- After commit:
mcp__lsp__commit_session(session_id: "abc123", apply: true)
mcp__lsp__destroy_session(session_id: "abc123")

-- After discard:
mcp__lsp__discard_session(session_id: "abc123")
mcp__lsp__destroy_session(session_id: "abc123")

© 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-simulate of blackwell-systems/agent-lsp.

• SKILL.md
• references/patterns.md

Open the folder on GitHubat commit 6fa5faf