What is migrate-to-meteor-3?

A migration guide for moving an application from Meteor 2 to Meteor 3, including changes to database calls, modules, reactivity, and packages.

Finding synchronous APIs, rewriting database calls, updating server and client code, handling Promises, and reviewing package compatibility.

Meteor 3 removed Fibers and makes server database operations asynchronous, so older code may fail or need callers to wait for results.

migrate-to-meteor-3 — Skill for Claude Code by meteor

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 meteor/agent-skills --skill migrate-to-meteor-3

Clone the repo

git clone --depth 1 https://github.com/meteor/agent-skills

Made for: Claude Code.

Or install meteor, the plugin that ships this one along with the rest of its 19 skills.

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.

README.md

[![agentmods](https://agentmods.dev/badge/skills/meteor/agent-skills/migrate-to-meteor-3/github.svg)](https://agentmods.dev/skills/meteor/agent-skills/migrate-to-meteor-3)

Your own site

<a href="https://agentmods.dev/skills/meteor/agent-skills/migrate-to-meteor-3"><img src="https://agentmods.dev/badge/skills/meteor/agent-skills/migrate-to-meteor-3/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.

Your own site · 80×15

<a href="https://agentmods.dev/skills/meteor/agent-skills/migrate-to-meteor-3"><img src="https://agentmods.dev/badge/skills/meteor/agent-skills/migrate-to-meteor-3.svg" alt="Reviewed on agentmods" width="80" height="20"></a>

Per session 151 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.

When invoked 2,082 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.

Model	Per session	Once invoked
Fable 5.1	$0.00151	$0.02082
Opus 5	$0.00076	$0.01041
Sonnet 5	$0.00030	$0.00416
Haiku 4.5	$0.00015	$0.00208

Measured 12d ago against content hash c418b052a09e, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-12, from the pricing page.

Security

Grade A, and why

migrate-to-meteor-3 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 12d 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.

skills/migrate-to-meteor-3/SKILL.md · 146 lines

How it starts

The opening of the file, as written. The whole thing — 146 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Migrate a Meteor 2.x application to Meteor 3.x

Meteor 3 removed Fibers. Server-side Mongo APIs are async. The module system enforces strict mode. Client reactivity inside async code needs care. Atmosphere packages often need forking or replacement. Approach the migration in phases. Do not flip the framework version flag first.

Recommended strategy

Update the project to the latest 2.x release.
Run the app with WARN_WHEN_USING_OLD_API=true meteor run. The console logs every sync-API call that needs an async sibling, giving you a to-do list before the framework flip.
Migrate server-side sync Mongo calls to *Async siblings while still on 2.x. Trace each changed function through every server-side caller: await where the caller consumes the value, forward Promises deliberately, and restructure sync-only boundaries. Stop only at an async-capable framework boundary. See references/async-rewrites.md and references/call-vs-callAsync.md. A community jscodeshift codemod automates the easy cases, but it misses non-standard collection imports (for example, meteor/<publisher>:collections). Review the diff by hand, then audit callback Promise ownership and collection argument shapes.
Audit Atmosphere packages. Find replacements or fork outdated ones; pin api.versionsFrom(['2.x', '3.0']). See references/package-triage.md. Save .meteor/versions and npm lockfile checkpoints so package-major changes remain distinguishable from Meteor.
Upgrade to Meteor 3.x.
Sweep implicit globals; rewrite to const or export / import. See references/module-system.md.
Audit Blaze helpers and Tracker.autorun blocks for lost reactivity after await. See references/client-reactivity.md.
Replace iterators that contain await (forEach, map, filter) with for...of or Promise.all. See references/js-iterators.md.
Audit publications using internal cursor APIs (_cursorDescription, manual sub.added) and framework handlers that read invocation this. Both synchronous and async publish handlers may return cursors; keep cursor transforms synchronous and use ordinary functions when Meteor must bind this. When a package patches Meteor.publish with an EnvironmentVariable, scope publish.call at the wrapper's top level, not inside the invoked handler. Verify invocation context before and after await. See references/publications.md and references/other-breaking-changes.md.
For TypeScript projects, install zodern:types and update tsconfig.json. See references/typescript-migration.md.
For React projects, decide whether to adopt the Suspense-aware react-meteor-data import. See references/react-migration.md, then use meteor-react for current hook, scaffold, and build guidance.

Read the full file on GitHub · 146 lines

Files

What ships with it

15 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

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.

12d ago First seen · 146 lines · 151 tokens per session scan A c418b052a09e

Subscribe to this mod's changes

migrate-to-meteor-3 is a skill published in the GitHub repository meteor/agent-skills (9 stars, last pushed today), licensed MIT. It adds 151 tokens to every session and 2,082 once invoked, about $0.0008 per session on Opus 5. 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.

Backend and APIs Claude Code Databases agent-skills ai-agents codex meteor meteorjs

event-store-design

Design and implement event stores for event-sourced systems. Use when building event sourcing infrastructure, choosing event store technologies, or implementing event persistence patterns.

wshobson/agents · 33 tokens

convex-explain-app

Explain an existing Convex app — data model + relationships, public vs internal functions, auth/ownership model, components, a request→data flow — read from the schema and function surface. Read-only.

openclaw/clawhub · 47 tokens

platform-custom-field-generate

Use this skill when users need to create, generate, or validate Salesforce Custom Field metadata. Trigger when users mention custom fields, field types, Roll-up Summary fields, Master-Detail relationships, Lookup relationships, formula fields, picklists, dependent (controlling) picklists, referencing a value set from…

forcedotcom/sf-skills · 194 tokens

field-service-sobject-create-configure

Headless 360 REST API deployment step for creating sObject records. Handles describe-based field discovery, required-field derivation, entity-relationship ordering, and composite graph transactions. Use this skill when a designer skill (or a user directly) needs to create sObject records after design confirmation…

forcedotcom/sf-skills · 74 tokens

durable-objects

Build, debug, or review Cloudflare Durable Objects code for persistent state and coordination.

fcakyon/claude-codex-settings · 22 tokens

nornicdb-grpc

Drive NornicDB over gRPC — the Qdrant-compatible surface (Collections, Points, Snapshots) plus the additive NornicSearch service. Use when ingesting via Qdrant SDKs, migrating from Qdrant, or running hybrid text+vector search from a non-Bolt client. Covers connection, RPC catalog, collection→database mapping…

orneryd/NornicDB · 98 tokens