Serve @cardstack/base modules from the host bundle

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Status

Work in progress, not ready for review. The PR is complete when every @cardstack/base module is served from the host bundle; the checklist below tracks progress. One commit per converted module, so the pattern is visible in the diff.

Goal

Importing @cardstack/base/* in the host resolves to code the host build already carries, instead of a per-module fetch of realm-server-transpiled source. Base does not change between deploys, so each of those fetches is a round trip for bytes the build could have included.

How

• shimExternals (app/lib/externals.ts) registers each base module with virtualNetwork.shimAsyncModule({ id, resolve: () => import(...) }), the mechanism that already serves runtime-common and boxel-ui to card code. The lazy import() lets Vite emit each module as its own chunk, so a loader import of that identifier is answered from the bundle.
• A Vite alias maps @cardstack/boxel-host/tools/* and @cardstack/boxel-host/commands/* to app/tools/, mirroring the virtual network's runtime shim, so a bundled base module that imports host tools resolves them at build time.
• The host test helper (tests/helpers/base-realm.ts) imports each converted module statically instead of through loader.import, so the suite exercises the bundled copy.

Progress

Served from the bundle:

• date/day, date/month, date/month-day, date/month-year, date/year, date/week, date/quarter

Still loaded through the loader by the test helper (next candidates):

• time, time/time-range, time/duration, time/relative-time
• string, number, boolean, big-integer, email, ethereum-address, phone-number, text-area, markdown, rich-markdown, color, code-ref, realm, enum, searchable, base64-image
• date, datetime, datetime-stamp, date-range-field
• cards-grid, workspace, process-card, remix-card, system-card, skill, file-api
• card-api

Then everything else under packages/base, at which point the per-module entries collapse into one @cardstack/base/ prefix shim with the same lazy import().

Shape during the transition

A bundled module's ../card-api import is bundled with it, while the rest of the host still loads card-api through the loader, so two copies of card-api exist until card-api itself is served from the bundle. The Integration | date-time fields tests build a card through the loader's card-api with the bundled fields as field types, which is where a class-identity mismatch would surface first.

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[chatgpt-codex-connector]

Codex Review Summary

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Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-09-11T02:13:31.730249Z	5d86c7e	PR opened

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Preview deployments

• Host staging preview

• Host production preview

Host Test Results

    1 files      1 suites   1h 59m 52s ⏱️
4 739 tests 4 725 ✅ 14 💤 0 ❌
4 754 runs  4 740 ✅ 14 💤 0 ❌

Results for commit 5d86c7e.

Realm Server Test Results

    1 files    210 suites   1h 12m 8s ⏱️
2 764 tests 2 764 ✅ 0 💤 0 ❌
2 803 runs  2 803 ✅ 0 💤 0 ❌

Results for commit 5d86c7e.

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💡 Codex Review

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Reviewed commit: 5d86c7e5b1

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[chatgpt-codex-connector]

Register base shims before the base-realm import map

In NetworkService.configureVirtualNetwork, the @cardstack/base/ realm mapping is installed before shimExternals, so registering either of these shims resolves its ID to the real base-realm URL. PackageShimHandler.handle only considers requests under PACKAGES_FAKE_ORIGIN, meaning loader imports of these IDs bypass the resolver and continue fetching the realm-server-transpiled modules; the new chunks therefore provide no offline or network-independent fallback. Register these shims before that realm import map or update the handler to serve mapped realm URLs.

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[chatgpt-codex-connector]

Keep host test base imports behind the loader

When the date-time tests request DayField or MonthField, these static re-exports are evaluated directly by the host build rather than via loader.import, so the tests no longer exercise either newly added virtual-network shim and can pass even when those shims fall through to the realm server. This is also a host-side static value import from the base realm, which the repository explicitly requires to remain loader-mediated.

AGENTS.md reference: AGENTS.md:L235-L237

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