# Agent Note: Client plugin loading — lazy factories, Cordis lifecycle, and hot reload

Status: implemented

English | [中文](2026-07-23-client-plugin-loading-model.zh.md)

> Scope: the browser-side plugin loading machinery — how code arrives, how Cordis governs it, and how hot reload rides on that model. This note owns the loading chain; the [client shell layering note](2026-08-15-client-shells-and-dynamic-packages.md) owns package categories, build faces, shared-module requests, and npm dependency declarations, while the [web client architecture note](2026-07-19-gui-web-client-architecture.md) owns slots and the data object layer.

## Problem

On the host, cordis plugin loading stands on Node's module machinery — the require cache and the internal ESM loader own module identity and bytes. The vendored `@cordisjs/plugin-loader` implements plugin governance and hot reload on top of that substrate, and the two meet at one boundary: `Loader.internal`.

The browser client runs the same cordis plugin mechanism, so it needs the same substrate underneath — and the browser has no Node module system.

Conventional frontend engineering digests all dependencies at build time: one bundle, externals resolved by the bundler, nothing left to manage at runtime. Runtime module management on top of that is the unusual requirement here. The client therefore splits into two layers: the upper layer is cordis plugin loading through the same vendored Loader, and the lower layer is module-granular dependency management — `dsh-client-modules`.

The lower layer supplies four capabilities: externals (the platform list), remote arrival (same-origin external classic scripts plus lazy factory registration), immutable revisioned delivery, and hot update (invalidate/prefetch).

Plugin bundles are built independently outside Vite's module graph. Feeding response text into an inline script leaves the browser with a dynamic source execution: no standard source-map chain connects the network resource, generated bundle, and TypeScript/TSX source, so performance profiles and stacks stop at generated `client.js`; the module system must also buffer the complete source and split one arrival responsibility across fetch and execute transport boundaries.

On top of that, client and host plugins register and load consistently: a package declares `dsh.client` once, the host scans the declaration into the boot graph, and the same Loader semantics govern entries on both sides.

The first-generation client loader (`createClientLoader`) hand-wrote both layers in one function. The fusion left no unload/reload path (loads were one-shot, style tags never removed), hand-copied dependency lists that had already drifted across three files, and a module-table backdoor for cross-plugin imports that duplicated cordis's service mechanism while making load order a correctness constraint. The structure below replaced it.

## Decision

### Package membership and module requests

The [client shell layering note](2026-08-15-client-shells-and-dynamic-packages.md) defines the current static and dynamic package sets and the import rules between them. The loading machinery treats every `dsh.client` package as a host-graph row with one ordinary `lib/client.js` factory bundle. Its declaration carries Cordis `inject` edges, synchronous module-table `external` requests, and the optional `immediately` prefetch mark; the composing app owns only the mounted roster.

The web kernel remains framework-free and imports no dynamic package value. Modules is itself a dynamic row, but the host parser delivers its factory before the Vite main module. The HTML-installed `__ModuleLoader__` facade uses that factory to construct the module system when the kernel calls `create()`. Every other dynamic row belongs to an application combo script; static React, Cordis, and UI library identities come from the shell seed.

### One module system, one plugin governor

The browser mirrors the host's division of labor. `dsh-client-modules` (`ClientModuleSystem`) takes the module-system seat that Node's internal ESM loader holds host-side; the same vendored `@cordisjs/plugin-loader` keeps the governance seat on both sides. The line between them in one sentence: **the module system owns module identity and bytes — how code arrives, registers, and becomes an exports; the Loader owns plugin lifecycle — when a plugin mounts, what it waits for, and how it is torn down.**

`ClientModuleSystem` is a lazy CJS table. Executing a bundle only **registers** its factory — the bundle calls `window.__ModuleLoader__.load({ id, factory })` and nothing else happens. Every module body side effect, CSS injection included, lives inside the factory closure and runs at materialization: the first `require`/import of that id, memoized after that. Import and prefetch recursively register declared dynamic requests before their consumer; a factory then materializes any registered-but-unmaterialized request synchronously. The table resolves through a fixed branch order: seed word → memoized record → graph-row classic-script registration → registered-factory materialization → loud throw. The modules factory is the bootstrap exception: the HTML facade materializes it first, and construction places those same exports directly in the memoized table. That final throw is the runtime mirror of the build-time purity gate. The system also keeps per-module bookkeeping — owned `<style data-plugin>` tag ids, observed require edges — and exposes the two verbs HMR needs: `prefetch(id)` (register the requested dynamic factories and the row's own factory; concurrent arrivals share one task) and `invalidate(id)` (drop a non-bootstrap factory and record so the next arrival reloads it).

The vendored Loader consumes the module system through its `internal` contract — the only call site is `tree.import` — and owns everything entry-shaped: entry creation, fiber activation through cordis service waiting (PENDING until injected services exist, cascading when a service is provided), update/refresh, teardown. The governance code is byte-identical to the host side, per vendor policy. Browserization is compile-time mapping in the shell's vite config: a `node:module` stub alias plus `process.*` defines make `ModuleLoader.fromInternal()` return undefined — exactly the empty slot the shell fills. The module system mounts as `ctx.modules`.

### Combo external-script arrival and source maps

The Host snapshots every built plugin artifact and partitions each scheduling phase's ordered rows into one or more same-origin classic scripts. It greedily fills each group while the longer map-form request URL remains within 3 KiB, preserving graph order and allowing another request instead of emitting an oversized URL. Each script is addressed by its package resources, for example `/plugins/??<package-a>/client.js,<package-b>/client.js&rev=<rev>`. The `bootstrap` and `application` values are scheduling phases in the graph, not URL components: HTML preloads every application URL before executing every parser-blocking bootstrap URL. The module system keys in-flight transport by combo URL, so concurrent row arrivals within one group execute one script. Successful settlement still requires each requested row's factory id to exist in the module table, and registration does not run the factory, so the side-effect boundary remains first materialization.

The shared tsdown preset emits `client.js.map` for every plugin and rewrites first-party source paths into the browser-resolvable repository form `/packages/<group>/<package>/src/...`. The production Client pass consumes `lib/types`; the preset supplies each tsc map to Rolldown and fills `sourcesContent` from the original files, so the final map reaches TypeScript/TSX instead of stopping at emitted JavaScript. Other workspace sources inlined into a bundle likewise resolve to their `packages/` owner, while dependency paths remain unchanged. Combo generation strips each local debug directive, records its generated-line offset, resolves every authored source against the original per-plugin map URL, and emits an Indexed Source Map v3. An authored map supplies its section; otherwise an identity section embeds the generated bundle and uses the packer's `sourceURL` as its source name when present. The absolute map URL mirrors the script resource list by changing every `client.js` suffix to `client.js.map`, so `/plugins/??<package-a>/client.js,<package-b>/client.js&rev=<rev>` points to `/plugins/??<package-a>/client.js.map,<package-b>/client.js.map&rev=<rev>`. One resource follows the same rule and still produces an indexed map with one section. The Vite shell also emits source maps, letting shell code and combo-loaded plugins map stacks and performance profiles back to TypeScript/TSX.

The graph retains each row's revisioned one-resource combo URL for HMR and adds a content-addressed descriptor for every startup combo request; several descriptors may carry the same scheduling phase. Initial row revisions are opaque process nonces rather than content hashes; they keep the snapshotted one-resource response immutable without hashing every plugin at startup. After the watcher observes one artifact change, `rebuilt(id)` hashes only that bundle and map and publishes the resulting revision. Startup combo revisions cover the combined script inputs and indexed map. Versioned scripts and maps use immutable caching. The Host serves only exact generated URLs; stale revisions and unadvertised resource lists return 404 instead of aliasing different bytes. An external script's `error` event exposes neither response status nor body, so failure diagnostics name only the URL; the same-origin Host and build-stamped registration id form the identity boundary, while the post-`load` factory-presence check rejects an artifact that did not register the expected id.

### The loading flow, end to end

What happens between `dsh web` starting and the UI appearing? Three stages: the host composes a graph and parser-preloads bootstrap factories, the HTML facade creates the module system and the shell prefetches, then Cordis orchestrates.

**Host side — compose the graph.**

1. The composing app (`apps/cli`) ships the roster as ordinary rows in its `cordis.yml` config tree — client plugin packages are entry rows like every host plugin, including the always-mounted `client-hmr` row. A roster row that fails to import is caught by `assertEntriesLoaded`; a row whose fiber rejects is reported with its original stack by `assertEntriesActivated` ([host boot decision](2026-07-24-web-config-tree-boot-and-transport-layering.md)).
2. The `dsh-client-modules` node half (the package is dual-face: its browser half is the module table) resolves each live Loader entry through the same `name` and owning-tree `baseUrl` inputs that imported its Host face, then reads the nearest owning package.json `dsh.client` declaration and composes `window.__DSH_BOOT__`: `{ rev, entries: [{ id, url, rev, inject?, immediately?, external? }], batches: [{ phase, url, rev, entries }] }`. The manifest package name is the browser module identity even when an overlay names a relative source or built entry file. Distinct active Loader sources resolving to one package name fail composition; after one source unloads, the surviving source supplies the row without a fiber restart. The row's three optional fields come from manifests, never hand-copied. Composition orders requested dynamic rows before their consumers, rejects synchronous request cycles, and assigns every row to exactly one initial batch. It refuses declared plugins without built `./client` bundles and groups their package/path rows under one required source-build instruction; malformed declaration fields also fail activation, and the Host audit reports either error from the FAILED fiber.
3. Scanning is incremental per package — there is no full-rescan code path. Each cordis `internal/plugin` emission marks the fiber's entry name dirty (entry-less fibers drop O(1)); a microtask flush reconciles each dirty name against live loader entries, with package metadata (including the negative "not a client package" verdict) cached per entry name and owning-tree base URL for the process lifetime and bundle re-hashing reachable only through `rebuilt(id)`. The activation pass seeds the same dirty set from current entries and flushes synchronously, so first scan and steady state share one implementation. Initial rows receive an opaque process nonce plus sequence without hashing their artifacts; startup combo revisions hash the combined script inputs plus indexed map, and the rows plus batch descriptors hash into `graph.rev`. The graph types are single-sourced in the modules package's `./client` export — the webserver knows nothing about the graph, while modules registers the combo route and contributes structured index-injection rows.

Why is the roster yml rows and not a scan? Because which plugins compose into a deployment is a composition decision, not a package property — a package declaring `dsh.client` in the repo does not mean this deployment mounts it, so discovery-by-scan cannot make that call; the node half scans only what the tree actually mounted.

**Phase one — the module face.** The injected HTML installs `window.__ModuleLoader__` in queue mode, starts preloading every application combo URL, executes every bootstrap combo URL as a blocking classic script, assigns `window.__DSH_BOOT__`, and then starts the Vite main module. The kernel calls the facade's `create()` with the raw graph and shell seeds. The facade removes and materializes the modules registration with a bootstrap `require` that rejects every external, then calls its `createClientModuleSystem` export. The modules bundle parses the graph, constructs the system, memoizes its own exports, retains the instance in its module closure, and switches the same facade to live registration. The kernel then prefetches every `immediately` row in parallel. Rows in the same application combo share its execution; separate combos load independently when an immediate row, a requested dependency, or ordinary entry import reaches them. A prefetch failure is swallowed here because phase two's import retries and owns the loud failure. `immediately` remains a registration barrier, not a package identity.

**Phase two — the plugin face.**

1. The kernel mounts the vendored Loader and injects the module system as `internal` before any entry exists. Ordering matters: `tree.import`'s bare-import fallback must never run in a browser.
2. It creates every graph row uniformly. Importing the modules row returns the memoized bootstrap exports, whose `apply()` provides the closed-over system as `ctx.modules`; rows that require that service remain PENDING until then, so the modules row needs no special creation position. Render assembly is an ordinary host-graph row provided by `dsh-client-ui-renderer`; the kernel appends no assembly pseudo-entry.
3. Graph order governs synchronous factory availability; Cordis activation remains independent and proceeds through service waiting.
4. `settled` = every entry created + `loader.await()` quiescent + an all-ACTIVE sweep. The sweep lists each import-failed, FAILED, or PENDING fiber with its missing services. It exists because cordis inject waits have no timeout — the sweep is the fail-loud floor.
5. The framework-free loading page projects real fiber states via `internal/status`. After the sweep, the kernel calls `ctx.uiRenderer.mount(container)` and replaces the page with the real UI in one pass.

### Hot reload: one driver plugin, self-watched bundles

Hot reload is a composition decision: the web bundle mounts the `client-hmr` row (a normal plugin package) unconditionally; its node half brings the bundle watch and the SSE channel, and the chain stays idle until a rebuild watcher rewrites client bundles. A composition that must not expose it disables the row.

How does a rebuilt bundle become a reload signal? The hmr node half observes it itself — no builder tells it. Before reading each startup snapshot, the module host captures the bundle stat baseline and exposes it through `ctx.clientModules.artifactBaseline(id)`. One HMR-owned interval compares every current graph row with that baseline. An unchanged row starts watching without a content read or hash; a write after baseline capture is already a stat delta and only that row enters `rebuilt(id)`. This avoids both an initial all-row re-hash and `fs.watchFile`, whose asynchronous first baseline can silently absorb a construction-time rebuild. Watch membership follows `onGraphChanged`; vanished rows drop out, and a bundle missing at poll time keeps its row dirty so reappearance forces a re-hash even with identical metadata. On a bundle mtime or size delta, or a dirty row, `rebuilt(id)` is the single re-hash entry point; it reads the current source map as part of that new artifact snapshot, while a map-only write does not remount unchanged executable code. When the `rev` actually changed, the node half broadcasts a `rebuilt` frame on `GET /plugins/events` — a system SSE channel that sends the full graph on connect and `rebuilt` frames on change, presentation-only wire that never enters the session log. Polling is deliberate because inotify does not fire on the weka network mount, the same reason the build-side watcher needs `--poll`; one bundle stat per row and interval is sufficient, the interval is a validated config field (default 500ms), and disposal clears the one timer. Rebuilding artifacts is any tsdown watch process's business — `scripts/dev-web.ts` remains the watch-build entry point, discovering its package list through `dsh.client` while scanning `packages/*/*/package.json` at startup — and builder and host share zero protocol. A torn bundle read self-heals: its stats keep changing while the write completes, so the next poll re-hashes and broadcasts the final rev.

On the browser side, the driver reloads one plugin per frame, serialized:

1. `invalidate` — drop the stale factory and record, and bind the rebuilt frame's revision to that row's one-resource combo URL. A live factory would make the next step a no-op.
2. `prefetch` — load that one-resource external script and register the fresh factory while the old fiber still serves. The initial multi-resource script never executes again.
3. `registry.delete` — before touching the fiber. A bare fiber dispose trips the vendored Loader's self-dispose branch, which would disable the entry permanently.
4. Drain the old fiber's disposers.
5. Remove owned `<style data-plugin>` tags.
6. `entry.refresh()` — re-imports, materializing the fresh factory. CSS re-injects here, under the same stable tag ids.
7. `fiber.await()` — rethrows loud.

Every plugin shares this one semantics; an `immediately` row reloads exactly like a lazy one. Dependency cascade costs zero client code: a fiber's activation epoch strings its service providers' uids, so replacing a foundational provider such as connection re-loads every dependent through cordis itself — correct, if heavy.

The support boundary, stated honestly. Reload is coarse by design: fresh fiber, fresh components, React state lost, data layer untouched — react-refresh-grade state preservation conflicts with "re-executing the bundle re-runs the factory" and is deliberately out. Static assembly packages and the shell kernel are not entries: changing them means a shell rebuild and a full page reload. Reload has no rollback: an import failure leaves the entry fiberless and the next rebuilt frame retries from scratch; an apply failure leaves a FAILED fiber for the status projection; both log loudly. Self-reload works — the in-flight reload finishes in the old bundle's closure and the new apply opens a fresh SSE channel — but frames arriving in the gap are lost, and the next rebuild renotifies. One known dev-only race: a rebuilt frame overlapping a still-in-flight boot arrival shares that arrival's task and may materialize the pre-rebuild bytes; the next frame self-heals.

## Package ownership

The current package inventory and build forms live in the [client shell layering note](2026-08-15-client-shells-and-dynamic-packages.md). This note retains only the loading properties that apply to every dynamic row: lazy factory registration, Cordis entry governance, external-script arrival, source maps, and HMR.

## Consequences

One governance implementation runs on both sides of the wire; the browser-specific layer is one module system plus one reload plugin. Dynamic packages have one artifact form, so the purity check covers them all. Cordis dependencies, module requests, and the boot tier live with their owners — the manifests — while the composing app holds only the roster. Host graph validation and recursive request arrival keep synchronous factory dependencies explicit. Browser-native script loading preserves the standard mapping among plugin network resources, generated bundles, and TypeScript/TSX sources, while the module system keeps only one replaceable `loadBundle` hook.

Costs accepted: the vendored Loader carries idle machinery in the browser (EntryTree persistence is a no-op, groups/isolation unused); every plugin edit in dev pays a bundle rebuild plus fiber remount; graph `inject` rows guide factory arrival but service availability remains the activation authority, so a mismatch appears at the settled sweep; the static UI libraries keep direct value exports; every bundle gains a source-map artifact; and external-script failures provide only coarse URL diagnostics instead of the HTTP status available to an explicit fetch. The Host retains per-plugin bundle/map snapshots, generated one-resource responses, current startup combo responses, and one previous startup generation, so memory scales as several copies of the composed client artifacts. This retained state keeps URLs immutable and lets an in-flight request finish across one HMR recomposition.

Roster: it lives in the web bundle's config tree (`packages/bundle/web-app/cordis.patch.yml`); `mountWebPlugins` and the `CLIENT_PACKAGES` constant are gone, and recomposing a deployment means swapping the yml/overlay. The graph composer lives in the `dsh-client-modules` node half, while the parser-preloaded client face bootstraps the browser module table. The webserver remains a plain route-registration plugin; `/api/*` binding, browser authentication, RPC envelopes, and exact Fetch routes belong to the Connection node half, while Remote dispatch belongs to API Gateway and the dev bundle watch plus SSE channel belongs to the hmr node half.

## Alternatives considered

| Rejected | One-line reason |
|---|---|
| Two-axis taxonomy (entry × arrival) with infrastructure packages lacking `dsh.client` | Erased manifest dependency edges (inject leaked to the composer), split the plugin shape in two, blinded the purity gate to half the plugins |
| Keep evolving the hand-written loader into a governor | Re-implements entry/fiber lifecycle the vendored Loader owns; HMR would have no shared skeleton with the host side |
| Reuse `@cordisjs/plugin-hmr` in the browser | ~80% solves problems the browser doesn't have (fs watching, deep graph coloring, Node's dual caches); the reload skeleton is copied as a shape |
| Module federation | Independently built remote bundles are exactly the form vite federation does not support |
| Import maps | Ruled out earlier; the DI require table is the terminal mechanism |
| Full ctx-ification now (React and libraries via services, no module table) | Static UI libraries still expose synchronous values, so removing the table would leave those imports without a shared identity |
| Eager instantiation with a frozen table | Runs bundle side effects at script arrival; lazy registration keeps execution at Cordis import while recursive `require` materializes registered requests |
| Fetch response text, then inject an inline `<script>` | Makes the module system buffer the complete source and maintain separate fetch/execute paths; dynamic source execution also breaks the browser-native association among the network resource, source map, and profile |
| Builder-push rebuild channel (`POST /plugins/rebuilt` from the orchestrator's `onSuccess`) | Couples reload to one blessed builder process and a second wire protocol; the webserver already holds every bundle path, and stat polling covers the torn-write race (re-hash on every stat change) that once justified pushing |
