build(rsc-runtime): one module graph, drop @modelcontextprotocol/sdk 1.x, expose ./package.json

[ScriptedAlchemy]

Closes the packages/rsc-runtime items of #566 (Section 2). Scope is @agent-bundle/runtime only; the other publishable packages' manifests and configs are untouched, as is src/state/sqlite.ts.

What changed

P1 — @modelcontextprotocol/sdk 1.x dropped

• packages/rsc-runtime/src/lower-mcp.ts:3 and src/project-mcp.ts import CallToolResult from @modelcontextprotocol/server 2.x (already a dependency) instead of @modelcontextprotocol/sdk/types.js; package.json:88 no longer lists @modelcontextprotocol/sdk@1.30.0; pnpm-lock.yaml loses the runtime's importer entry (the 1.x snapshot itself stays, agent-bundle still depends on it).
• Structural difference between the two SDKs: 1.x types structuredContent as Record<string, unknown> and _meta as a record, 2.x types both as unknown. Passing the 2.x type straight through broke examples/rsc-agent-runtime/src/mcp/handlers.ts, which hands runtime results to a 1.x handler. The package now states the shape it actually emits — McpCallToolResult / McpContentBlock (lower-mcp.ts:51-68, exported from the root at src/index.ts:97): SDK content blocks, _meta and structuredContent as finite JsonObjects — which is assignable to both SDK lines' CallToolResult. lowerMcpResult, documentToCallToolResult, and McpProjectedToolResult.result return/carry it; attachMcpStructuredContent (project-mcp.ts:215-228) is generic over its input (<T extends CallToolResult>(result: T, value) => T), so a caller holding a result typed by either SDK line gets it back as the same type — a 1.x CallToolResult is not assignable to McpCallToolResult (_meta is a loose record there), and the first draft of this PR would have stopped such callers compiling (self-review finding 1). Every modelcontextprotocol import in the repo (git grep -n "modelcontextprotocol" -- ':!repos' ':!pnpm-lock.yaml') typechecks against it.
• Packed tarball: no file in it mentions @modelcontextprotocol/sdk (manifest, dist/*.js, dist/*.d.ts); the shipped declarations import only react, zod, effect, @modelcontextprotocol/server, rsc-markdown-stream.

P2 — one module graph, no string externals

packages/rsc-runtime/rslib.config.ts:5-35 builds all nine public entries in one bundle-mode lib (option (a)). Rslib/Rspack emits every module two entries share in a common chunk (dist/<id>.js) that both import, so each class exists once; a module only one entry reaches stays in that entry's own chunk, so the graphs remain disjoint where they must.

Why not (b) bundle: false + redirect.js — measured, not assumed (scratch build of the same nine entries into /tmp, Rslib 0.23.2, redirect.js.extension: true): it passes every boundary in state-packaging.test.ts and yields an identical identity report, so it is a valid answer too, but it ships 48 JS files instead of 22 at +1.4 % bytes (374,108 vs 368,894), forces four exports import targets to move (state, notices, mount, lineage → */index.js, plus two test fixtures), and shows no measurable cold-import difference. Same guarantee, more files and churn, so (a).

Evidence (release-mode npm pack, before = origin/main, after = this branch):

	before	after
dependencies	@modelcontextprotocol/sdk 1.30.0, @modelcontextprotocol/server 2.0.0, effect, flare-redact, react-server-dom-rspack, rsc-markdown-stream, zod	@modelcontextprotocol/server 2.0.0, effect, flare-redact, react-server-dom-rspack, rsc-markdown-stream, zod
peerDependencies	@rspack/core ^2.2.0-0, react 19.2.8, react-dom 19.2.8	same; @rspack/core now peerDependenciesMeta.optional
tarball (gzip)	134,554 B	132,707 B
unpacked	624,988 B (64 files)	603,000 B (74 files)
dist/*.js	387,837 B	368,047 B
dist/*.d.ts	187,655 B	185,376 B
this.name = 'AgentStateError' definitions in dist	2 (state.js, state/sqlite.js)	1
AgentContractError / AgentRequestError definitions	3 / 3	1 / 1
node:sqlite referenced by	state/sqlite.js only	state/sqlite.js only
__webpack_require__ in dist	none	none
exports map	9 subpaths	same 9 + ./package.json
sideEffects: false	yes	yes
attw --profile esm-only on the tarball	—	clean (exit 0)
publint on the tarball	—	"All good!" (also runs at build via rsbuild-plugin-publint, throwOn: 'warning')

The duplication in today's build is real, not hypothetical: the literal externals covered '../state/index.js', but src/state/sqlite.ts imports ./contract.js directly (expectOperable, expectRevisionShape), so Rspack re-bundled the kernel's contract module — and its AgentStateError — into state/sqlite.js. Observable today:

$ node identity-probe.mjs <main dist>
sqlite store.read({revision:-1}) threw AgentStateError invalid-input | instanceof state.AgentStateError: false
$ node identity-probe.mjs <this branch's dist>
sqlite store.read({revision:-1}) threw AgentStateError invalid-input | instanceof state.AgentStateError: true

The existing state-packaging identity test passed on main only because its trigger (lifetime-mismatch) is thrown by code that reached AgentStateError through the externalized ./index.js.

Tests (both fail against main's dist — swapping main's dist into the workspace gives AgentContractError is defined in 3 dist files and sqliteRevisionError.instanceOfStateError: false):

• packages/rsc-runtime/tests/state-packaging.test.ts (integration pool) now walks the dist import graph per entry (tests/support/dist-graph.ts): every dist file is reachable from some public entry (so a chunk the walker's import parser missed would fail the test, not silently weaken it); root and ./plugin graphs contain no file that defines AgentStateError/AgentNoticeError (by definition file, whatever the quoting) and no kernel/ledger/sqlite identifier, and ./plugin stays Effect-free; every file that mentions node:sqlite/DatabaseSync is reachable from ./state/sqlite and from no other entry (by reachability, so Rspack may move the sqlite code into its own chunk without breaking the test); every error class declared in src (this.name = '…Error') is defined exactly once across the dist (occurrences counted, not files), and AgentStateError's file is in the graph of ./state, ./state/sqlite, ./mount, ./lineage, ./notices; a child process (--conditions=react-server, NODE_OPTIONS stripped so a host preload cannot skew moduleLoadList) imports all nine entries, asserts process.moduleLoadList has no NativeModule sqlite before ./state/sqlite and has it after, root.AgentRequestError === plugin.AgentRequestError, and errors thrown by the sqlite entry (lifetime-mismatch, and the formerly forked invalid-input) and the mount entry are instanceof ./state's AgentStateError.
• packages/rsc-runtime/tests/packed-entry-identity.test.ts (packed pool, registered in rstest.integration-tests.ts:152) installs the release tarball with npm, runs the same static graph checks against the installed dist (reachability, one definition per class, sqlite confinement — the probe alone would not see a deferred import('node:sqlite')), and repeats the probe through the exports map (@agent-bundle/runtime, /plugin, /flight/server, /state, /state/sqlite, /notices, /notices/inbox-route, /mount, /lineage), plus: no @modelcontextprotocol/sdk in the installed manifest or declarations, no * peer range, @rspack/core optional, and import.meta.resolve('@agent-bundle/runtime/package.json') resolves.
• lineage has no cheap runtime trigger for an AgentStateError (its instanceof is inside idempotency-conflict redelivery handling), so it is covered structurally: one definition in the dist, and that file is in the lineage entry's graph.

Rslib 0.23 vs 1.0: the config uses only lib[].source.entry, bundle, dts, format, syntax, and top-level output — the same shape on both; nothing here needs a follow-up for build/rslib-1.

P3 — manifest hygiene (packages/rsc-runtime/package.json)

• :71 — "./package.json": "./package.json" export (attw: 🟢 JSON on every resolution mode).
• :83-87 — @rspack/core marked peerDependenciesMeta.optional. No runtime entry imports it (packed dist/*.js externals: react, react-server-dom-rspack/{server,client}.node, effect, zod, flare-redact, rsc-markdown-stream, @modelcontextprotocol/server, node:*); it is react-server-dom-rspack's build-plugin peer, which agent-bundle supplies at build time. This is exactly the AB7014 guidance for a required peer nothing imports. Measured against real installs (npm 12 and pnpm 11, before/after tarballs in fresh consumers): today the flag changes nothing observable — react-server-dom-rspack@0.1.0 still declares the same @rspack/core ^2.2.0-0 as a required peer, so both package managers auto-install @rspack/core@2.2.2 either way with byte-identical lockfile entries and no warnings; the only visible difference is pnpm peers check (with auto-install-peers=false) no longer listing the runtime as a wanter. The runtime provably loads every entry, including ./state/sqlite, with @rspack/core absent (npm install --legacy-peer-deps). The consumer-facing win lands when react-server-dom-rspack marks its peer optional too — worth a follow-up there, not here.
• react / react-dom stay exact 19.2.8 and required — deliberate, not accidental: the Flight wire format is pinned to the React build (docs/plans/2026-08-14-rsc-agent-runtime-demo-design.md:364, agent-bundle pins the same), and react-server-dom-rspack's client.node (root entry) and server.node (./flight/server) both require("react-dom") at import time. No * ranges.
• rsc-markdown-stream stays ^0.1.0 (:93) with the pnpm-workspace.yaml workspace:* override, per the read of docs/preview-packages.md and the harness: scripts/run-packed-tests.mjs and tests/support/shared-pack.ts pack with npm pack, which does not rewrite workspace: protocols, so a workspace:* specifier would ship verbatim in the harness tarball and fail the consumer install with EUNSUPPORTEDPROTOCOL; the AB7015 rule documents the same (workspace: counts as a registry specifier only under a pnpm/Yarn/Bun prepack lifecycle). The override already gives the workspace the linked package; the published range is what consumers need.
• Release gate: pnpm lint:release (root package.json) now runs attw --pack --profile esm-only and scripts/check-declaration-imports.mjs on the packed runtime as well — build: gate releases on attw + declaration-import check; manifest hygiene for agent-bundle, rsc-markdown-stream, create-agent-bundle (#566 §2) #568 added that gate for the other three packages; the runtime is the fourth (48 packed declarations, 44 reachable from 9 export entries, 0 errors, 0 warnings). preview-packages.mdx (en + zh) lists it.
• AB7014/AB7015 for this package: agent-bundle prepack applies to agent-bundle projects, so the rules were checked by hand against the packed tarball — every dependencies entry is imported by packed JS or referenced by a packed .d.ts; every specifier is a registry version/range; the one peer nothing imports is now optional.

Docs

No page under website/docs/en/** lists the runtime's dependencies, install size, or entry layout (installation.mdx names the package; preview-packages.mdx mentions the renderer dependency, unchanged). guide/authoring/mcp.mdx (en + zh) gains a paragraph naming the lowered result type McpCallToolResult/McpContentBlock and its assignability to both SDK lines' CallToolResult; packages/rsc-runtime/README.md:158 says the same. docs/preview-packages.md:70 listed the runtime's peers as react, react-dom, @rspack/core — now says the last is optional. A repo-wide sweep found no consumer outside packages/rsc-runtime naming a dist/ path of the runtime (everything goes through the exports subpaths), so the extra shared chunks are invisible to them. pnpm docs:site:build passes (TypeDoc compiles the public API, which reaches the new exported types).

Gates

On the final state: pnpm build, pnpm typecheck (plus examples/rsc-agent-runtime's tsc, the 1.x consumer), pnpm lint, pnpm test:unit (3589 passed), state-packaging.test.ts (7/7), packed-entry-identity.test.ts through scripts/run-packed-tests.mjs (1/1), pnpm docs:site:build. On the previous push: pnpm test:integration:run (1065 passed), pnpm test:packed (11 files, 28 passed, 1 skipped). A compile check (in /tmp, against the workspace types) confirmed attachMcpStructuredContent round-trips a 1.x CallToolResult, a 2.x CallToolResult, and McpCallToolResult, and that McpCallToolResult is assignable to both SDK lines; its negative control (const bad: McpCallToolResult = legacy) fails as expected.

CI on f22c2e9 had one red job, Release gates (Node 22.19): packages/workbench/tests/packed-release.e2e.test.ts › "foreground outage ledger quiet fence" — the first /api/project/session probe 9 ms into a Workbench restart got net::ERR_SOCKET_NOT_CONNECTED where packed-outage-ledger.ts:167 tolerates only ERR_CONNECTION_REFUSED/ERR_CONNECTION_RESET; the next eleven probes were REFUSED and recovery returned 200. This PR does not touch packages/workbench, and the runtime's own packed test passed in that same job. It recurred on the first merged head (e9f041967, run 33936651225) while Release gates passed on main and four other PRs in the same window; closeChild sends SIGTERM (graceful), so the browser's first retry races the server closing its keep-alive sockets and Chromium reports RESET (tolerated since 7eefeae) or SOCKET_NOT_CONNECTED (not yet) by sub-millisecond ordering — nothing the runtime's dist layout can influence. One gh run rerun --failed of 33936651225 passed with no code change. Follow-up, out of this PR's scope: add net::ERR_SOCKET_NOT_CONNECTED to downServerProbeCodes in packages/workbench/tests/support/packed-outage-ledger.ts:167.

Self-review

Reviewer: change-risk-reviewer subagent, model gpt-5.6-sol-medium, diff vs origin/main; plus a generalPurpose test-robustness review of the new test files.

1. attachMcpStructuredContent input narrowed from SDK 1.x CallToolResult to McpCallToolResult — should-fix. A 1.x-typed result has _meta: { [x: string]: unknown; … }, not assignable to JsonObject; external callers would stop compiling. Fixed: the function is generic <T extends CallToolResult>(result: T, value: unknown): T (project-mcp.ts:215-228); compile check with both SDK lines and the package's own type passes, negative control fails.
2. errorClassDefinitions counted files, not occurrences — two copies in one chunk would pass. Fixed: one entry per match (dist-graph.ts), assertion unchanged (toHaveLength(1)).
3. Regex import walker could see imports in strings/comments or miss a fourth import form. Fixed: static/side-effect imports match from statement start only; dynamic import() kept; and both tests now assert unreachedFiles(sources) is empty — Rslib emits no unreferenced chunk, so a missed edge form surfaces as an unreached file instead of a silently smaller closure.
4. sqlite confinement required the identifiers to sit in state/sqlite.js by name — a legitimate Rspack split into a private chunk would fail it. Fixed: every file mentioning node:sqlite/DatabaseSync must be reached by ./state/sqlite and no other entry (entriesReaching).
5. Packed test had no static sqlite check — a deferred import('node:sqlite') in another entry would not run during the probe. Fixed: the installed dist gets the same reachability, definition-count, and confinement checks.
6. Root/plugin kernel check keyed on the single-quoted this.name = 'AgentStateError' marker. Fixed: the root and plugin closures must not contain the definition file of AgentStateError/AgentNoticeError, found quote-agnostically.
7. Probe children inherited NODE_OPTIONS — a host preload importing node:sqlite would fail the test spuriously. Fixed: probeEnvironment() strips it in both tests.
8. No findings on: build layout and export targets, node:sqlite isolation of the shipped dist, in-repo consumers of the renamed types, changeset, docs parity.

Second pass (change-risk-reviewer, gpt-5.6-sol-medium, after the fixes above) — verified finding 1's fix; two new findings:

9. No regression test for the 1.x compatibility of attachMcpStructuredContent — should-fix. Fixed: examples/rsc-agent-runtime/tests/mcp-lowering.test.tsx (the repo's one 1.x-typed consumer) annotates a lowered result and its attachMcpStructuredContent round-trip as the 1.x SDK's CallToolResult; the example's tsc (CI "Examples check") fails if either narrows again — verified by reintroducing the narrowing, rebuilding the runtime declarations, and watching the example typecheck fail with TS2345 on that line.
10. New public types McpCallToolResult/McpContentBlock undocumented on the website — must-fix per AGENTS.md docs parity. Fixed: paragraph in website/docs/{en,zh}/guide/authoring/mcp.mdx plus the README line; pnpm docs:site:build green (parity check included).

Third pass (change-risk-reviewer, gpt-5.6-sol-medium, on the final head): no findings in any category — docs match source, zh paragraph faithful, example test correct, no remaining merge risk.

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