ember-4-to-5-migration

name	ember-4-to-5-migration
description	The 4.12 LTS → 5.x migration path — what's removed (ember-cli-typescript as a separate addon, RSVP global, classic test API holdouts), the ember-data → @ember-data/request transition (and the WarpDrive direction), Glint adoption with template-imports, optional .gjs/.gts adoption. Use when planning, scoping, or executing a 4 → 5 upgrade.
type	reference

Ember 4.12 → 5.x Migration

If the prerequisites in ember-4-recommendations are met (Embroider at least in compat mode, official TS setup, Octane settled, addons 5-compatible), the 4 → 5 jump is mostly a version bump plus opt-in features. The headline work is:

1. The version bump itself.
2. The addons rolling forward.
3. Adopting <template> tag and Glint's template-imports environment (optional but recommended).
4. Adopting the @ember-data/request request manager (optional).

4.12 LTS  →  5.4  →  5.8  →  5.12  →  ...latest LTS
                                         ↓
                                       (continue with `ember/` plugin)

Pre-flight

Verify on 4.12:

• No Ember.X global imports anywhere.
• All ember-data relationships specify async and inverse.
• No classic test API (moduleForXxx) anywhere.
• No (mut ...) or (action ...) template helpers.
• Embroider in compat mode (or optimized).
• If TypeScript: official setup, no ember-cli-typescript addon.
• All addons in package.json ship versions that support both 4.12 and 5.x.
• Test suite green; deprecation workflow file empty or owner-tagged.

If anything's unchecked, finish on 4.12.

What 5.x removes / changes

Removed / changed	Replacement
ember-cli-typescript (the standalone addon) — its functionality is now in the framework	Use tsconfig.json directly with @tsconfig/ember/tsconfig.json.
Implicit injection in some places (@service without an explicit name when the resolver is ambiguous)	@service('foo') declare foo: FooService; everywhere.
Older ember-data model registry path	The path moves around in 5.x — use the ember-data/types/registries/model augmentation pattern.
Some ember-cli-mirage 1.x patterns	Bump to 2.x or 3.x depending on the version range; serializer/factory APIs largely unchanged.
Several deprecated RouterService methods	Use the modern equivalents documented in the upgrade guide.
Older Glint environment naming	The ember-loose and ember-template-imports environments are stable; older configurations need updating.

The full removed list is in the official Deprecations app; filter to "since: 4.x".

What 5.x adds

New	What it gives you
<template> tag in .gjs/.gts	Single-file components with strict-mode templates. Replaces .ts + .hbs pairs over time.
Glint ember-template-imports environment	Type-checking for <template> blocks. Materially better than Glint's loose mode.
@ember-data/request request manager	Builder-based fetch layer. Adapters/serializers become optional.
WarpDrive direction	The next-generation ember-data branding/architecture. Backward-compatible during 5.x.
Vite-based dev server (via @embroider/vite or ember-cli-vite)	Faster HMR. Optional.
Polaris RFCs landing in feature flags	Route templates as components, etc. — opt-in via flags during 5.x.

Hop-by-hop

5.x's release cadence has been less predictable than 4.x's, but the LTS-by-LTS approach is still the safest. Bump to each LTS in order, run the suite, run the codemods, smoke test, ship. Rough cadence:

4.12 → 5.4 LTS

The biggest hop. Most removals land here. Specifically:

• ember-cli-typescript is no longer needed — remove it from package.json, replace its tsconfig.json with @tsconfig/ember/tsconfig.json.
• Older ember-data paths get cleaned up — relationships without explicit options error out (they were warnings in 4.12).
• Many addons release "5.x-compatible" majors here — bump them in the same window.
• Embroider becomes the preferred build pipeline for 5.x. If you're still on classic ember-cli, expect rough edges.

pnpm exec ember-cli-update --to 5.4
pnpm exec ember-cli-update --run-codemods

5.4 → 5.8 LTS

Quieter. Mostly addon ecosystem catching up.

This is a good moment to:

• Adopt <template> tag for a small number of new components. Not a migration of existing code — just new files.
• Install @glint/environment-ember-template-imports and turn it on in tsconfig.json.

5.8 → 5.12 LTS

The last 5.x LTS in the predictable cadence (subject to the actual release schedule). At this point:

• Glint is stable enough for whole-codebase use.
• Most major addons ship Glint signatures.
• The <template> tag is everywhere in new code.
• The @ember-data/request request manager is the recommended way to do fetches.

This is the handoff point to the ember-polaris-migration skill — Polaris-style authoring is now mainstream.

TypeScript / Glint adoption order

If you're adding template type-checking during the 5.x window:

1. Bump to 5.x with the JS-only TS setup intact.
2. Stabilize. Run the suite. Smoke-test.
3. Install Glint and the ember-loose environment.
4. Add component signatures to every component. Most should already have them from the 4.x phase.
5. Run glint --watch until the codebase is clean.
6. Add glint --noEmit to CI.
7. Install ember-template-imports and the matching Glint environment.
8. Adopt <template> tag for new components. Don't migrate existing ones in the same window.
9. Plan a slow migration of existing components to <template> tag, opportunistically when you'd touch them anyway.

ember-data — the request-manager transition

@ember-data/request is opt-in throughout 5.x. The transition shape:

// existing 4.x style — still works in 5.x
const post = await this.store.findRecord('post', '42');

// new 5.x style — coexists with the above
import { findRecord } from '@ember-data/json-api/request';
const { content: post } = await this.store.request(findRecord('post', '42'));

Don't rewrite all existing fetches at once. Two practical lines:

1. New endpoints use the request manager. Especially custom RPC endpoints — no more custom adapter required.
2. Existing endpoints stay on the legacy findRecord/query API until you're touching them anyway.

The legacy adapter/serializer pipeline survives in 5.x. WarpDrive is the long-term direction; for a 5.x app today, you're fine with both styles coexisting.

<template> tag adoption

Same advice as for the request manager: new files in .gts, existing files stay. Plan a slow migration.

When you do migrate a file:

1. Rename foo.ts + foo.hbs → foo.gts.
2. Wrap the .hbs body in a <template>...</template> inside the class.
3. Add import statements for every component, helper, and modifier referenced.
4. Run Glint. Fix the resulting errors.
5. Delete the old .hbs (it's gone — confirm via git status).

See the ember-polaris-migration skill for the full workflow.

Addon survival list (4 → 5)

Rough categorization at the time of 5.x's mature releases:

Addon	5.x status
ember-cli-mirage	Alive. Major bumps but API stable.
ember-power-select	Alive. Glint signatures shipping.
ember-cli-page-object	Alive.
ember-test-selectors	Alive.
ember-modifier	Alive. Stable API.
@ember/render-modifiers	Alive.
ember-truth-helpers	Replaced/wrapped by @ember/truth-helpers (built-in).
ember-svg-jar	Alive.
ember-intl	Alive.
ember-simple-auth	Alive.
ember-concurrency	Alive. Glint signatures shipping.
ember-resources	Alive. The canonical "resource" pattern.
tracked-built-ins	Alive.
ember-cli-typescript (the addon)	Removed/no longer needed.
Addons stuck on 4-only with no 5-compat statement	Replace or fork.

Time estimates (rough, mid-size app, 4.12 prerequisites met)

Hop	Calendar days
4.12 → 5.4	5–10
5.4 → 5.8	1–3
5.8 → 5.12	2–5
(Optional) Glint adoption	1–2 weeks separate
(Optional) <template> tag adoption	Continuous, opportunistic
Total core upgrade	~2–3 weeks

If 4.x prerequisites aren't met, add 2–4 weeks to fix them on 4.12 first.

Common 4 → 5 surprises

Surprise	Cause	Fix
Build fails with "Cannot find module 'ember-cli-typescript'"	Addon removed but a config file still references it.	Delete ember-cli-typescript config from ember-cli-build.js; remove from package.json.
Type 'PostModel' is not assignable to type 'unknown'	ModelRegistry augmentation path changed.	Update the path: declare module 'ember-data/types/registries/model' { ... }.
Glint reports errors in addons' templates	Addon doesn't ship Glint signatures.	Skip addons in your Glint config, or add a stub registry, or wait for the addon to update.
RouterService.transitionTo deprecation	Method signature changed.	Use the modern equivalent per the upgrade guide.
Some (component "name" ...) calls fail	Embroider staticComponents requires curried component references.	Replace string with imported component.
Test suite hangs after bump	Custom test waiter not migrated to @ember/test-waiters.	Migrate the waiter.

Verification — at the latest 5.x LTS

• ember-source on the latest 5.x LTS.
• ember-data matching.
• ember-cli-typescript not in package.json.
• All component signatures declared.
• (Optional) Glint passes in CI on ember-loose environment.
• (Optional) Glint passes on ember-template-imports environment.
• (Optional) New components use <template> tag.
• All addons on 5-compatible versions.
• Embroider in compat or optimized mode.
• CI green; suite passes; manual smoke-test passes.
• Deprecation workflow file empty.

When all green, switch to the modern Ember skills for ongoing work — Polaris adoption, the modern addon skill, and the ember-architect / ember-test-engineer agents take over from here.

See also

• ember-4-recommendations — the prerequisite work.
• ember-polaris-migration — <template> tag adoption.
• ember-typescript-and-glint — Glint setup at the destination.
• Official: emberjs.com/releases/, Deprecations, @ember-data/request.