fix: unblock @modelcontextprotocol/sdk upgrades past 1.26.0 (nodenext)

[evilmachina]

Summary

Fixes #42. The build was stuck on @modelcontextprotocol/sdk@1.26.0 because newer versions tripped tsc with TS1479 under the Node16 module resolution. This bumps the SDK to 1.29.0 and migrates module resolution to nodenext.

Root cause

The SDK's ./server export entry advertises an unconditional "types": "./dist/esm/server/index.d.ts" (ESM declaration). Under moduleResolution: "Node16", tsc read that ESM .d.ts, classified the bare subpath as ESM, and refused to emit a require() for it from this CommonJS package:

src/mcp_server.ts(30,31): error TS1479: The current file is a CommonJS module whose imports
will produce 'require' calls; however, the referenced file is an ECMAScript module ...

Fix: migrate to nodenext

tsconfig module/moduleResolution → nodenext. The newer algorithm correctly applies the package's CommonJS require condition for the bare subpath, so the import resolves without error.

• The package stays CommonJS — nodenext keys module format off package.json "type" (absent → CommonJS). Emit is still require(...); no entrypoint, __dirname, or readFileSync plumbing changes were needed.
• nodenext floats to current Node resolution semantics, so this also future-proofs against later SDK subpath changes (unlike Node16, pinned to Node 16-era behavior).
• ServerOptions is tightened to import type (used only as a type annotation), so it erases at compile time.

Why nodenext over the one-line import type workaround

A surgical alternative existed (keep Node16, import ServerOptions from the explicit /server/index.js wildcard subpath). We chose nodenext deliberately: it's the forward-looking resolution mode, fixes the bare public import without relying on the ./* exports wildcard, and unblocks future SDK subpath changes generally rather than patching one import site. A full ESM migration (type: module) was not needed — nodenext solves it while the package stays CommonJS.

Verification

• npm run build passes on SDK 1.29.0 under nodenext
• npm test passes (236/236)
• Emitted JS still uses require() (package remains CommonJS); the type import is erased
• Server starts over stdio, responds to initialize, lists all 12 tools

Acceptance criteria

• SDK upgradable to >= 1.29.0
• npm run build passes
• npm test passes (236 tests)
• MCP server starts over stdio and tools respond
• Decision documented (changeset + this PR): migrate to nodenext, package stays CommonJS

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📥 Commits

Reviewing files that changed from the base of the PR and between 21010f7 and 394bb0e.

⛔ Files ignored due to path filters (1)

• package-lock.json is excluded by !**/package-lock.json, !package-lock.json

📒 Files selected for processing (4)

• .changeset/unblock-mcp-sdk-upgrade.md
• package.json
• src/mcp_server.ts
• tsconfig.json

✅ Files skipped from review due to trivial changes (2)

• .changeset/unblock-mcp-sdk-upgrade.md
• src/mcp_server.ts

🚧 Files skipped from review as they are similar to previous changes (1)

• package.json

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📝 Walkthrough

Walkthrough

@modelcontextprotocol/sdk is bumped from ^1.26.0 to ^1.29.0 in package.json. tsconfig.json switches module and moduleResolution to nodenext. src/mcp_server.ts changes ServerOptions to a type-only import from @modelcontextprotocol/sdk/server/index.js. A new changeset file records the patch release and the TypeScript/module-resolution change.

🚥 Pre-merge checks | ✅ 2

✅ Passed checks (2 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly matches the main change: unblocking SDK upgrades via nodenext.
Description check	✅ Passed	The description is directly about the SDK upgrade, TS1479 fix, and module-resolution change.

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