loom-istio

loom-istio is a skill for Claude Code from cosmix/loom. It costs 22 tokens per session (10,705 once invoked), scanned B, original, MIT.

A guide to Istio, a service mesh for controlling, securing, and observing traffic between microservices. It explains Envoy proxies, mutual TLS (which encrypts and authenticates service-to-service traffic), and sidecar or ambient deployment models.

In plain words
What is it for?
Use it to configure encrypted service traffic, canary or blue-green releases, A/B routing, retries, timeouts, circuit breakers, internet gateways, and controlled outbound traffic.
Why use it?
It helps manage communication between services without requiring each application to implement traffic policies itself. It also clarifies which features require ambient waypoints and how the two deployment models differ.

Skill for Claude Code

Written for Claude Code: allowed-tools in frontmatter.

Good fit Use it to configure encrypted service traffic, canary or blue-green releases, A/B routing, retries, timeouts, circuit breakers, internet gateways, and controlled outbound traffic.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/cosmix/loom/loom-istio
View source ↗ cosmix/loom
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.

Any agent
npx skills add cosmix/loom --skill loom-istio
Clone the repo
git clone --depth 1 https://github.com/cosmix/loom

Made for: Claude Code.

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 loom-istio

README.md
[![agentmods](https://agentmods.dev/badge/skills/cosmix/loom/loom-istio.svg)](https://agentmods.dev/skills/cosmix/loom/loom-istio)
Your own site
<a href="https://agentmods.dev/skills/cosmix/loom/loom-istio"><img src="https://agentmods.dev/badge/skills/cosmix/loom/loom-istio.svg" alt="Measured on agentmods" height="20"></a>
Per session 22 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 10,705 The whole file, excluding the scripts and references it only reads on demand.
Security scan B 2 findings. A grade says what 26 rules found in the file — not that it is safe. Third-party audits
  • NVIDIA SkillSpector warn 7 Sept 2026
SkillSpector: 1 finding, up to high

These are SkillSpector’s own severities. On a checked sample its high-severity flags on skills were ~96% false positives — a documented command, a public API, a “never do X” rule — so we show them as a caution to read, not a verdict. Why →

  • high Supply Chain · line 122
    Remote code is downloaded and executed. This bypasses code review and could introduce malicious code.
    Fix: Avoid downloading and executing remote scripts. Use trusted packages from PyPI/npm. If remote fetch is required, verify checksums and use HTTPS.
How audits are shown
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 $0.00022 $0.10705
Opus 5 $0.00011 $0.05352
Sonnet 5 $0.00004 $0.02141
Haiku 4.5 $0.00002 $0.01070

Measured 5d ago against content hash 2a09455f1c0e, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-08, from the pricing page.

Security

Grade B, and why

loom-istio scanned grade B with 2 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 5d 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.

Downloads and executes remote codemediumSupply chain

curl | sh runs whatever the server returns today, which is not necessarily what it returned when this was reviewed.

curl -L https://istio.io/downloadIstio | sh -

Downgraded: this mod is about security review, or the phrase is quoted, so it is likely naming the pattern rather than instructing it.

Makes network callslowCapability

Not a fault in itself. Listed so you know the mod talks to something, and to what.

curl -L https://istio.io/downloadIstio | sh -
skills/loom-istio/SKILL.md · 1,206 lines

How it starts

The opening of the file, as written. The whole thing — 1,206 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Istio Service Mesh

Overview

Istio is a service mesh: Envoy proxies intercept all service traffic to provide traffic management, mTLS, and observability with no app changes. Two data-plane models — pick deliberately:

  • Sidecar (classic): one Envoy per pod; full L7 everywhere; higher per-pod CPU/mem and injection restart cost.
  • Ambient (GA in 1.24): per-node ztunnel does L4 mTLS + L4 auth/telemetry automatically; waypoint proxies add L7 only where deployed. Lower overhead, no injection restarts, but L7 features silently no-op without a waypoint. See Currency.

Quick Reference: Common Tasks

Task Resources Section
Enable mTLS between services PeerAuthentication mTLS PeerAuthentication
Route traffic to new version VirtualService + DestinationRule Traffic Splitting for Canary
Add circuit breaker DestinationRule (outlierDetection) Circuit Breaker and Retry
Configure retries/timeouts VirtualService (retries, timeout) Circuit Breaker and Retry
Expose service to internet Gateway + VirtualService Gateway and VirtualService
Control egress traffic Sidecar + ServiceEntry Sidecar Resource for Egress
Add authorization rules AuthorizationPolicy AuthorizationPolicy for RBAC
Configure load balancing DestinationRule (loadBalancer) DestinationRule with Traffic Policies
Test resilience VirtualService (fault injection) Fault Injection for Testing

Architecture Components

Control Plane (istiod)

istiod is a single unified binary (since Istio 1.5) that performs:

  • Service discovery and configuration distribution (xDS to the Envoy sidecars)
  • Certificate authority for mTLS
  • Sidecar injection (mutating admission webhook)
  • Configuration validation

Read the full file on GitHub · 1,206 lines

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. 5d ago Changed · -37 tokens per session 2a09455f1c0e
  2. 8d ago First seen · 1,206 lines · 59 tokens per session scan B 30dbbf67dcba

Subscribe to this mod's changes

loom-istio is a skill published in the GitHub repository cosmix/loom (54 stars, last pushed yesterday), licensed MIT. It adds 22 tokens to every session and 10,705 once invoked, about $0.0001 per session on Opus 5. A static security scan graded it B with 2 findings (downloads and executes remote code, makes network calls). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.

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