extension-host

extension-host is a cursor rule for Cursor from keska-labs/enterprise-skills. It costs 0 tokens per session (334 once invoked), scanned A, original, MIT.

Coding rules for the extension host of a VS Code extension, including dependency setup, logging, errors, asynchronous work, and synchronization.

In plain words
What is it for?
Use them when implementing or reviewing code in src/, especially extension setup, panels, sync services, configuration, and event handlers.
Why use it?
They keep the extension's services connected consistently and help prevent missed cleanup, bundled platform APIs, and unhandled failures.

Cursor rule for Cursor

Written for Cursor: installed under .cursor/.

Good fit Use them when implementing or reviewing code in src/, especially extension setup, panels, sync services, configuration, and event handlers.

Compare 6 cursor rules from other repositories ↓
Install with agentmods
npx agentmods add rules/keska-labs/enterprise-skills/extension-host
Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

Clone the repo
git clone --depth 1 https://github.com/keska-labs/enterprise-skills

Made for: Cursor.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for extension-host

README.md
[![agentmods](https://agentmods.dev/badge/rules/keska-labs/enterprise-skills/extension-host/github.svg)](https://agentmods.dev/rules/keska-labs/enterprise-skills/extension-host)
Your own site
<a href="https://agentmods.dev/rules/keska-labs/enterprise-skills/extension-host"><img src="https://agentmods.dev/badge/rules/keska-labs/enterprise-skills/extension-host/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

agentmods 80×15 button for extension-host

Your own site · 80×15
<a href="https://agentmods.dev/rules/keska-labs/enterprise-skills/extension-host"><img src="https://agentmods.dev/badge/rules/keska-labs/enterprise-skills/extension-host.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 0 Nothing until a file matches its globs; then the whole rule loads.
When invoked 334 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5.1 $0.00000 $0.00334
Opus 5 $0.00000 $0.00167
Sonnet 5 $0.00000 $0.00067
Haiku 4.5 $0.00000 $0.00033

Measured 10d ago against content hash e98412dacf37, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-10, from the pricing page.

Security

Grade A, and why

extension-host scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 10d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

.cursor/rules/extension-host.mdc · 32 lines

What it actually says

Extension host (src/)

Composition

  • Wire dependencies in src/extension.ts: construct services once, pass into panels and SyncEngine.
  • Register everything that implements vscode.Disposable via context.subscriptions.push(...).

Errors and logging

  • Use Logger for diagnostics (log, warn, error). The output channel is the primary trace for support.
  • Throw or propagate ServiceError with a stable reason (no_session, network, source_invalid, …) when the failure maps to user-visible connection/sync health; panels map reasons to UI state where needed.

Async

  • Use async/await. At fire-and-forget boundaries (e.g. event handlers), use void this.someAsync() or .catch(...) so unhandled rejections do not crash the host.

VS Code API

Sync and config

  • ConfigService reads/writes skillSync.* keys only.
  • SyncEngine owns periodic sync and emits results; do not duplicate sync loops elsewhere.
Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 10d ago First seen · 32 lines · 0 tokens per session scan A e98412dacf37

Subscribe to this mod's changes

extension-host is a cursor rule published in the GitHub repository keska-labs/enterprise-skills (7 stars, last pushed 21d ago), licensed MIT. It costs nothing until one of its globs matches a file; then it loads 334 tokens. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.