refactor(build): align Rsbuild integration with official plugin patterns

[ScriptedAlchemy]

Source-reading pass over the official/community plugins evaluated in #509 (rsbuild-plugin-publint, rsbuild-plugin-arethetypeswrong, @rsbuild/plugin-type-check, @rsbuild/plugin-check-syntax, rsbuild-plugin-source-build, @rsbuild/plugin-react, rsbuild-plugin-virtual-module) plus Rsbuild core's built-in plugins, looking for patterns that make an existing path in packages/agent-bundle/src/build/** or the two package rslib.config.ts files shorter or clearer with identical output. Scope kept to that; no new abstraction, plugin layer, or option. Each change below is one commit-sized item the maintainer can judge separately.

Changes

#	Path	Before → after (code lines, comments excluded)	Pattern borrowed from	Behavior
1	packages/agent-bundle/rslib.config.ts — the __filename/__dirname ESM shim	17 → 15; nesting 5 → 3 levels; drops the Rspack/rspack type imports and the engine parameter	api.processAssets({ stage: 'additions' }, ({ assets, compilation, sources }) => …) — how Rsbuild's built-in rsbuild:inline-chunk and rsbuild:appIcon plugins hang asset rewrites, instead of a hand-written Rspack plugin class (apply → thisCompilation.tap → processAssets.tap({ stage: PROCESS_ASSETS_STAGE_ADDITIONS })) appended via tools.rspack. Rsbuild's implementation of the hook is the same thisCompilation + processAssets.tapPromise({ stage }) tap.	dist/** byte-identical (warm and cold cache): diff -rq before/after clean; dist/1178.js still carries the shim.

That is the only change that met the bar. pluginPublint was already registered the official way, and both composeEntryLibConfig and composeMcpAppsRsbuildConfig already use @rsbuild/plugin-react.

Considered and left alone (with the reason)

• Post-build checks onto onAfterBuild / afterEmit (assertNoResidualReservedImports, assertSelfContainedViews; publint/attw use api.onAfterBuild, check-syntax uses compiler.hooks.afterEmit over compilation.getAssets()): the framework's checks deliberately read the published on-disk bytes after rslib.build() resolves and after close(), and wrapping them in a plugin would be a new plugin layer, not a shorter path.
• Logging through @rsbuild/core's logger (publint/attw/type-check pattern): src/build/** prints nothing itself — every failure is a thrown Error/DiagnosticError that the CLI's diagnostics layer renders, and builds run at logLevel: 'silent'/'error'. Nothing to move.
• Option validation: the official plugins validate nothing beyond TypeScript types; the framework's tools shape checks (AB4720–4723) live in config/validate.ts, outside this scope, and are the diagnostics the docs promise.
• pluginReact({ fastRefresh: false }) in rslib.ts: the plugin only enables refresh in dev mode, so the option is redundant for build(), but the file is owned by perf(build): one Rslib instance per target for every agent-host surface (xref row 12) #503 right now (see below) and the explicit false documents intent.
• Multi-environment handling: composeMcpAppsRsbuildConfig already uses one Rsbuild instance with one environment per view, the shape type-check's checkedTsconfig-per-environment logic assumes.

For the xref-build-orchestration worker (#503 touches rslib.ts; not edited here)

1. virtualModulesPluginConstructor is duplicated verbatim in src/build/rslib.ts (Rslib's engine) and src/build/mcp-apps.ts (workspace @rsbuild/core), differing only in the message text. One helper taking (rspack, engineName, purpose) would drop ~10 lines; both call sites keep their own engine object, so the dual-engine rule holds.
2. enforceInvariants in rslib.ts grows a DefinePlugin and a VirtualModulesPlugin through config.plugins = [...(config.plugins ?? []), …] twice; a single append at the end of the mutator is one statement.

Verification

• pnpm typecheck, pnpm lint: clean.
• packages/agent-bundle/dist before vs after: diff -rq reports no differences, with the default warm Rspack cache and with a fresh AGENT_BUNDLE_RSLIB_CACHE_DIRECTORY.
• artifact/** for examples/audiobook-curator and examples/host-test: unchanged by construction — no src/build/** file changes in this PR and the package dist they build with is byte-identical.

Review status

Codex reviewed 5a3cb01 (PR opened). One thread, addressed in-branch rather than by reply (this PR posts no comments):

• .changeset/build-official-plugin-patterns.md — "implementation-only summary": agreed; there is no user-facing change to describe (byte-identical dist/**, no command, export, or config key). The changeset is removed and the PR carries the skip-changeset label, the AGENTS.md escape hatch for genuinely no-op changes.

Last Codex-reviewed head: 5a3cb01. Unreviewed heads (no re-review arrived after the pushes; this PR posts no comments): the changeset-number commit, the rebase over #507, and the changeset removal — current head 76877346d. Merged on green CI per the AGENTS.md fallback; any thread opened afterwards is answered in a follow-up PR.

[changeset-bot]

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[chatgpt-codex-connector]

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Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-09-04T02:27:15.827186Z	5a3cb01	PR opened

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[chatgpt-codex-connector]

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Reviewed commit: 5a3cb01fcf

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[chatgpt-codex-connector]

Replace the implementation-only changeset summary

When the next Version Packages release consumes this changeset, this paragraph becomes user-facing release prose, but it only documents the internal processAssets/Rspack refactor and explicitly says behavior is unchanged; it also names no public command, export, or config key. Replace it with the required user-facing imperative summary rather than publishing internal build mechanics.

AGENTS.md reference: AGENTS.md:L104-L105

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[pkg-pr-new]

npm i https://pkg.pr.new/ScriptedAlchemy/agent-bundle@510

npm i https://pkg.pr.new/ScriptedAlchemy/agent-bundle/create-agent-bundle@510

npm i https://pkg.pr.new/ScriptedAlchemy/agent-bundle/@agent-bundle/runtime@510

commit: 7687734