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Agent Skill

Mirrord Prev Env skill

mirrord-prev-envmetalbear-co/mirrordmirrord/mcp/corpus/skills/mirrord-prev-env/SKILL.md

Help users create and manage mirrord preview environments — running a modified service as an isolated pod in a shared Kubernetes cluster, scoped by an environment key and HTTP/queue traffic filtering, so teams can validate and review changes against real traffic without affecting live services. Use when a developer wants to run "mirrord preview" ad hoc, share a preview via a link (mirrord-share-ingress), or wire preview environments into CI with the metalbear-co/mirrord-preview GitHub Action (e.g. per-PR previews, least-privilege cluster access).

5.4kMIT

always on

122 tokname + description

once used

9,633 tokSKILL.md body

bundled files

14 KB

repo stars

5.4kGitHub

Install the Mirrord Prev Env skill

Skills CLI (Claude Code, Codex, Cursor and others)

npx skills add https://github.com/metalbear-co/mirrord --skill mirrord-prev-env

Claude Code, by hand (all projects)

git clone --depth 1 https://github.com/metalbear-co/mirrord.git /tmp/mirrord
mkdir -p ~/.claude/skills
cp -R /tmp/mirrord/mirrord/mcp/corpus/skills/mirrord-prev-env ~/.claude/skills/mirrord-prev-env

For one project only, copy the folder into .claude/skills/ in that project instead. The agent picks it up when a task matches its description.

What it costs your context

Agent Skills load in three steps. Tokens counted with the o200k tokenizer; your model's count will differ a little.

WhenWhat loadsCost
Every sessionName and description122 tok
When the agent uses itThe SKILL.md instructions9,633 tok
Only if opened1 bundled files (4 KB)varies

Until it is used, mirrord-prev-env costs about 11× less than the median MCP server we measured (1,362 tokens on every turn). Installing all 12 skills from metalbear-co/mirrord would load 1,593 tokens of descriptions. Skills vs MCP study

Checks

  • The instructions are over 5,000 tokens, the Agent Skills specification's guideline for SKILL.md.
  • The instructions are over 500 lines; the specification suggests moving detail into reference files.

Checked 2026-10-22 · method

What's inside

The headings of its SKILL.md. Read the full file on GitHub.

  • Mirrord Preview Environment Skill
  • Purpose
  • When to Use This Skill
  • Security (must follow)
  • Security Boundaries
  • How preview environments work
  • Prerequisites
  • Mode 1 — Ad-hoc (developer) usage
  • Preview config (mirrord.json)
  • Sending traffic to your preview
  • Building a Preview From Your Manifests
  • Targeting scaled-to-zero workloads (queue splitting only)
  • Targeting CronJobs
  • Sharing a preview via a link
  • Stable share hosts
  • Mode 2 — CI with the mirrord-preview GitHub Action
  • Cluster access for CI (least-privilege)
  • Action inputs
  • Per-PR lifecycle (from the official docs)
  • Driving the CLI directly in CI (alternative to the Action)
  • Using extraconfig for anything the Action doesn't expose
  • CI best practices
  • Common Issues
  • Response Guidelines

More skills from metalbear-co/mirrord

All skills in this repo
  1. mirrord-chaosmetalbear-co/mirrord

    Help users chaos test their app with mirrord: inject artificial latency or connection errors into a mirrord session's outgoing traffic via per-session chaos rules managed with the `mirrord chaos` CLI. Use when a user wants to add latency or delay to outgoing connections or a dependency (e.g. a slow database), simulate connection failures (reset, timed out, refused), test app behavior under degraded network conditions, or wire chaos rules into CI test runs. Always use this skill instead of the deprecated _experimental_.latency mirrord config option.

    5.4k119 tok idle · 3,421 in use
  2. mirrord-cimetalbear-co/mirrord

    Help users set up mirrord in CI pipelines for testing against real Kubernetes environments. Use when users want to run end-to-end tests, integration tests, or automated tests in CI using mirrord to connect to staging/shared clusters.

    5.4k52 tok idle · 3,331 in use
  3. mirrord-configmetalbear-co/mirrord

    Helps users generate, edit, and validate mirrord.json configuration files for mirrord (MetalBear). Use when the user wants to connect their local process to a Kubernetes environment, configure features (env/fs/network), or needs feedback on an existing mirrord.json. Always ensures output JSON is valid and schema-conformant.

    5.4k72 tok idle · 2,643 in use
  4. mirrord-db-branchingmetalbear-co/mirrord

    Helps users configure mirrord.json for database branching, enabling isolated database copies for safe development and testing. Use when the user wants to set up MySQL, MariaDB, PostgreSQL, MSSQL, MongoDB, Redis, DynamoDB, ClickHouse, Google Spanner, Amazon S3, turbopuffer, or generic branches, configure copy modes, connection sources, schema migrations, IAM authentication, or manage database branches.

    5.4k94 tok idle · 17,404 in use
  5. mirrord-header-propagationmetalbear-co/mirrord

    Makes a codebase propagate W3C baggage (the `baggage` header carrying `mirrord-session=<key>`) end to end, so mirrord HTTP filters, preview environments, and queue splitting can route a whole request chain to one developer's session. Detects existing OpenTelemetry, Datadog, or other tracing that can already propagate baggage and enables it; otherwise adds a small propagation layer. Covers inbound/outbound HTTP and gRPC, publishing to and consuming from Kafka, RabbitMQ, SQS/SNS, GCP Pub/Sub, Azure Service Bus, NATS, Redis Pub/Sub, BullMQ and Temporal, per-message context restore in consumers, and storage hand-offs such as a GCS signed URL upload that triggers Pub/Sub or an S3 presigned upload that triggers SQS. Ends with a report of every flow found and which ones still drop the header. Use when the user asks to propagate headers, baggage, tracestate, the mirrord session key, or trace context across services or queues, or when a mirrord filter matches the first service but not downstream services or queue consumers.

    5.4k237 tok idle · 4,164 in use
  6. mirrord-kafkametalbear-co/mirrord

    Helps DevOps engineers configure mirrord Operator's Kafka queue splitting feature end-to-end. Generates the MirrordSplitConfig and MirrordPropertyList Kubernetes CRD YAMLs (the current resources; MirrordKafkaTopicsConsumer + MirrordKafkaClientConfig are deprecated but still supported), the matching mirrord.json split_queues section with message_filter and jq_filter, and Helm value guidance. Use this skill whenever the user mentions Kafka splitting with mirrord, MirrordSplitConfig, MirrordPropertyList, MirrordKafkaClientConfig, MirrordKafkaTopicsConsumer, Kafka queue/topic splitting, configuring mirrord with Kafka, Kafka Streams splitting, MSK IAM auth, or troubleshooting Kafka splitting sessions. Also trigger on split_queues with queue_type Kafka, or connecting mirrord to a Kafka cluster. This is a Team/Enterprise feature of mirrord.

    5.4k188 tok idle · 6,045 in use
  7. mirrord-operatormetalbear-co/mirrord

    Help users install and configure the mirrord Operator for team/enterprise environments. Use when users ask about operator setup, Helm installation, cloud API key or license configuration, air-gapped/offline licensing, enabling features (queue splitting, DB branching, preview environments, multi-cluster), internal registries, OpenShift/GKE Autopilot, RBAC, or multi-user mirrord deployments. Also use when an AI agent hits a Team or Enterprise feature on a cluster with no license and needs to offer the user a trial (agent-started trial; the trial is Enterprise tier).

    5.4k124 tok idle · 6,107 in use
  8. mirrord-propagation-discoverymetalbear-co/mirrord

    Scans a live Kubernetes environment with `mirrord dump` to find an identifier mirrord can filter traffic on: a header, a `baggage` or `tracestate` member, a tenant or user id, a trace id (W3C, B3, X-Ray, Google, Jaeger), a JWT claim, a cookie, a path segment, or a JSON body field that is present on every hop of a request chain, unique to one developer's traffic, and settable by that developer. Runs mirror-only dumps on each service, sends a tagged probe request at the edge or observes real traffic, scores the candidates, and produces the matching `http_filter` (regex, jq on headers, path, method, body, or combinations) plus a per-hop report of where each identifier is dropped. Installs the mirrord CLI through a package manager when it is missing. Use when the user asks what to filter on, whether the cluster already propagates a request id or trace context, how to isolate their own requests on a shared staging cluster, how to filter on a JWT or cookie with mirrord, or wants to inspect live traffic with mirrord dump. Changes no application code: propagation gaps go to the mirrord-header-propagation skill.

    5.4k273 tok idle · 4,050 in use