fix(client): add missing Windows env vars to DEFAULT_INHERITED_ENV_VARS

[ChrisJr404]

Closes#2037.

On Windows, DEFAULT_INHERITED_ENV_VARS is missing a few variables that common dev tooling needs. The most impactful one is PATHEXT: without it, spawn('npm', ...) (and git, python, anything else that ships as .cmd/.exe/.bat) fails with ENOENT even when PATH is set, because Node has no extensions to try.

Added to the win32 branch:

• PATHEXT — extensions Windows treats as executable. Fix for the spawn npm ENOENT symptom in the issue.
• COMSPEC — path to cmd.exe; needed by spawn({ shell: true }) and anything that shells out.
• PROGRAMFILES(X86) and PROGRAMW6432 — the other two Program Files paths. Tools that resolve install locations need at least one of these depending on whether the parent is 32-bit or 64-bit.
• WINDIR — used by some legacy tooling that doesn't accept SYSTEMROOT.

Also sorted the array so future additions are easier to eyeball.

Test

Added a small assertion in stdio.test.ts that pins the expected list per platform, so a regression on either branch fails locally. pnpm test is green (365/365) and pnpm lint/pnpm typecheck are clean.

Changeset included as a patch bump on @modelcontextprotocol/client.

[changeset-bot]

🦋 Changeset detected

Latest commit: a379b7a

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 6 packages

Name	Type
@modelcontextprotocol/client	Patch
@modelcontextprotocol/core	Patch
@modelcontextprotocol/server	Patch
@modelcontextprotocol/server-legacy	Patch
@modelcontextprotocol/codemod	Patch
@modelcontextprotocol/core-internal	Patch

Not sure what this means? Click here to learn what changesets are.

Click here if you're a maintainer who wants to add another changeset to this PR

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@modelcontextprotocol/client

npm i https://pkg.pr.new/@modelcontextprotocol/client@2043

@modelcontextprotocol/codemod

npm i https://pkg.pr.new/@modelcontextprotocol/codemod@2043

@modelcontextprotocol/core

npm i https://pkg.pr.new/@modelcontextprotocol/core@2043

@modelcontextprotocol/server

npm i https://pkg.pr.new/@modelcontextprotocol/server@2043

@modelcontextprotocol/server-legacy

npm i https://pkg.pr.new/@modelcontextprotocol/server-legacy@2043

@modelcontextprotocol/express

npm i https://pkg.pr.new/@modelcontextprotocol/express@2043

@modelcontextprotocol/fastify

npm i https://pkg.pr.new/@modelcontextprotocol/fastify@2043

@modelcontextprotocol/hono

npm i https://pkg.pr.new/@modelcontextprotocol/hono@2043

@modelcontextprotocol/node

npm i https://pkg.pr.new/@modelcontextprotocol/node@2043

commit: a379b7a

[daxian-dbw]

I can confirm this issue caused troubles to starting executables from within a local stdio MCP server, such as PowerShell, GitHub CLI, and etc.

Especially that PowerShell depends on PATHEXT to discover native executables. Without that environment variable, no native executable can be discovered within PowerShell on Windows.

@jspahrsummers and @anaisbetts, I found you made the decision to not include those environment vars in #36. Could you please give some attention to this fix?

[ChrisJr404]

Rebased onto main. The only conflict was in stdio.test.ts from the import refactor and the new dispose/buffer tests — stdio.ts merged cleanly, all the new env vars are intact. daxian-dbw's confirmation about PowerShell/PATHEXT matches what we saw: without PATHEXT nothing native resolves. Ready for another look.

[ChrisJr404]

Closes#2037.

On Windows, DEFAULT_INHERITED_ENV_VARS is missing a few variables that common dev tooling needs. The most impactful one is PATHEXT: without it, spawn('npm', ...) (and git, python, anything else that ships as .cmd/.exe/.bat) fails with ENOENT even when PATH is set, because Node has no extensions to try.

Added to the win32 branch:

• PATHEXT — extensions Windows treats as executable. Fix for the spawn npm ENOENT symptom in the issue.
• COMSPEC — path to cmd.exe; needed by spawn({ shell: true }) and anything that shells out.
• PROGRAMFILES(X86) and PROGRAMW6432 — the other two Program Files paths. Tools that resolve install locations need at least one of these depending on whether the parent is 32-bit or 64-bit.
• WINDIR — used by some legacy tooling that doesn't accept SYSTEMROOT.

Also sorted the array so future additions are easier to eyeball.

Test

Added a small assertion in stdio.test.ts that pins the expected list per platform, so a regression on either branch fails locally. pnpm test is green (365/365) and pnpm lint/pnpm typecheck are clean.

Changeset included as a patch bump on @modelcontextprotocol/client.

[changeset-bot]

🦋 Changeset detected

Latest commit: a379b7a

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 6 packages

Name	Type
@modelcontextprotocol/client	Patch
@modelcontextprotocol/core	Patch
@modelcontextprotocol/server	Patch
@modelcontextprotocol/server-legacy	Patch
@modelcontextprotocol/codemod	Patch
@modelcontextprotocol/core-internal	Patch

Not sure what this means? Click here to learn what changesets are.

Click here if you're a maintainer who wants to add another changeset to this PR

[pkg-pr-new]

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@modelcontextprotocol/client

npm i https://pkg.pr.new/@modelcontextprotocol/client@2043

@modelcontextprotocol/codemod

npm i https://pkg.pr.new/@modelcontextprotocol/codemod@2043

@modelcontextprotocol/core

npm i https://pkg.pr.new/@modelcontextprotocol/core@2043

@modelcontextprotocol/server

npm i https://pkg.pr.new/@modelcontextprotocol/server@2043

@modelcontextprotocol/server-legacy

npm i https://pkg.pr.new/@modelcontextprotocol/server-legacy@2043

@modelcontextprotocol/express

npm i https://pkg.pr.new/@modelcontextprotocol/express@2043

@modelcontextprotocol/fastify

npm i https://pkg.pr.new/@modelcontextprotocol/fastify@2043

@modelcontextprotocol/hono

npm i https://pkg.pr.new/@modelcontextprotocol/hono@2043

@modelcontextprotocol/node

npm i https://pkg.pr.new/@modelcontextprotocol/node@2043

commit: a379b7a

[daxian-dbw]

I can confirm this issue caused troubles to starting executables from within a local stdio MCP server, such as PowerShell, GitHub CLI, and etc.

Especially that PowerShell depends on PATHEXT to discover native executables. Without that environment variable, no native executable can be discovered within PowerShell on Windows.

@jspahrsummers and @anaisbetts, I found you made the decision to not include those environment vars in #36. Could you please give some attention to this fix?

[ChrisJr404]

Rebased onto main. The only conflict was in stdio.test.ts from the import refactor and the new dispose/buffer tests — stdio.ts merged cleanly, all the new env vars are intact. daxian-dbw's confirmation about PowerShell/PATHEXT matches what we saw: without PATHEXT nothing native resolves. Ready for another look.

[ChrisJr404]

Closes#2037.

On Windows, DEFAULT_INHERITED_ENV_VARS is missing a few variables that common dev tooling needs. The most impactful one is PATHEXT: without it, spawn('npm', ...) (and git, python, anything else that ships as .cmd/.exe/.bat) fails with ENOENT even when PATH is set, because Node has no extensions to try.

Added to the win32 branch:

• PATHEXT — extensions Windows treats as executable. Fix for the spawn npm ENOENT symptom in the issue.
• COMSPEC — path to cmd.exe; needed by spawn({ shell: true }) and anything that shells out.
• PROGRAMFILES(X86) and PROGRAMW6432 — the other two Program Files paths. Tools that resolve install locations need at least one of these depending on whether the parent is 32-bit or 64-bit.
• WINDIR — used by some legacy tooling that doesn't accept SYSTEMROOT.

Also sorted the array so future additions are easier to eyeball.

Test

Added a small assertion in stdio.test.ts that pins the expected list per platform, so a regression on either branch fails locally. pnpm test is green (365/365) and pnpm lint/pnpm typecheck are clean.

Changeset included as a patch bump on @modelcontextprotocol/client.

[changeset-bot]

🦋 Changeset detected

Latest commit: a379b7a

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 6 packages

Name	Type
@modelcontextprotocol/client	Patch
@modelcontextprotocol/core	Patch
@modelcontextprotocol/server	Patch
@modelcontextprotocol/server-legacy	Patch
@modelcontextprotocol/codemod	Patch
@modelcontextprotocol/core-internal	Patch

Not sure what this means? Click here to learn what changesets are.

Click here if you're a maintainer who wants to add another changeset to this PR

[pkg-pr-new]

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@modelcontextprotocol/client

npm i https://pkg.pr.new/@modelcontextprotocol/client@2043

@modelcontextprotocol/codemod

npm i https://pkg.pr.new/@modelcontextprotocol/codemod@2043

@modelcontextprotocol/core

npm i https://pkg.pr.new/@modelcontextprotocol/core@2043

@modelcontextprotocol/server

npm i https://pkg.pr.new/@modelcontextprotocol/server@2043

@modelcontextprotocol/server-legacy

npm i https://pkg.pr.new/@modelcontextprotocol/server-legacy@2043

@modelcontextprotocol/express

npm i https://pkg.pr.new/@modelcontextprotocol/express@2043

@modelcontextprotocol/fastify

npm i https://pkg.pr.new/@modelcontextprotocol/fastify@2043

@modelcontextprotocol/hono

npm i https://pkg.pr.new/@modelcontextprotocol/hono@2043

@modelcontextprotocol/node

npm i https://pkg.pr.new/@modelcontextprotocol/node@2043

commit: a379b7a

[daxian-dbw]

I can confirm this issue caused troubles to starting executables from within a local stdio MCP server, such as PowerShell, GitHub CLI, and etc.

Especially that PowerShell depends on PATHEXT to discover native executables. Without that environment variable, no native executable can be discovered within PowerShell on Windows.

@jspahrsummers and @anaisbetts, I found you made the decision to not include those environment vars in #36. Could you please give some attention to this fix?

[ChrisJr404]

Rebased onto main. The only conflict was in stdio.test.ts from the import refactor and the new dispose/buffer tests — stdio.ts merged cleanly, all the new env vars are intact. daxian-dbw's confirmation about PowerShell/PATHEXT matches what we saw: without PATHEXT nothing native resolves. Ready for another look.

[ChrisJr404]

Closes#2037.

On Windows, DEFAULT_INHERITED_ENV_VARS is missing a few variables that common dev tooling needs. The most impactful one is PATHEXT: without it, spawn('npm', ...) (and git, python, anything else that ships as .cmd/.exe/.bat) fails with ENOENT even when PATH is set, because Node has no extensions to try.

Added to the win32 branch:

• PATHEXT — extensions Windows treats as executable. Fix for the spawn npm ENOENT symptom in the issue.
• COMSPEC — path to cmd.exe; needed by spawn({ shell: true }) and anything that shells out.
• PROGRAMFILES(X86) and PROGRAMW6432 — the other two Program Files paths. Tools that resolve install locations need at least one of these depending on whether the parent is 32-bit or 64-bit.
• WINDIR — used by some legacy tooling that doesn't accept SYSTEMROOT.

Also sorted the array so future additions are easier to eyeball.

Test

Added a small assertion in stdio.test.ts that pins the expected list per platform, so a regression on either branch fails locally. pnpm test is green (365/365) and pnpm lint/pnpm typecheck are clean.

Changeset included as a patch bump on @modelcontextprotocol/client.

[changeset-bot]

🦋 Changeset detected

Latest commit: a379b7a

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 6 packages

Name	Type
@modelcontextprotocol/client	Patch
@modelcontextprotocol/core	Patch
@modelcontextprotocol/server	Patch
@modelcontextprotocol/server-legacy	Patch
@modelcontextprotocol/codemod	Patch
@modelcontextprotocol/core-internal	Patch

Not sure what this means? Click here to learn what changesets are.

Click here if you're a maintainer who wants to add another changeset to this PR

[pkg-pr-new]

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@modelcontextprotocol/client

npm i https://pkg.pr.new/@modelcontextprotocol/client@2043

@modelcontextprotocol/codemod

npm i https://pkg.pr.new/@modelcontextprotocol/codemod@2043

@modelcontextprotocol/core

npm i https://pkg.pr.new/@modelcontextprotocol/core@2043

@modelcontextprotocol/server

npm i https://pkg.pr.new/@modelcontextprotocol/server@2043

@modelcontextprotocol/server-legacy

npm i https://pkg.pr.new/@modelcontextprotocol/server-legacy@2043

@modelcontextprotocol/express

npm i https://pkg.pr.new/@modelcontextprotocol/express@2043

@modelcontextprotocol/fastify

npm i https://pkg.pr.new/@modelcontextprotocol/fastify@2043

@modelcontextprotocol/hono

npm i https://pkg.pr.new/@modelcontextprotocol/hono@2043

@modelcontextprotocol/node

npm i https://pkg.pr.new/@modelcontextprotocol/node@2043

commit: a379b7a

[daxian-dbw]

I can confirm this issue caused troubles to starting executables from within a local stdio MCP server, such as PowerShell, GitHub CLI, and etc.

Especially that PowerShell depends on PATHEXT to discover native executables. Without that environment variable, no native executable can be discovered within PowerShell on Windows.

@jspahrsummers and @anaisbetts, I found you made the decision to not include those environment vars in #36. Could you please give some attention to this fix?

[ChrisJr404]

Rebased onto main. The only conflict was in stdio.test.ts from the import refactor and the new dispose/buffer tests — stdio.ts merged cleanly, all the new env vars are intact. daxian-dbw's confirmation about PowerShell/PATHEXT matches what we saw: without PATHEXT nothing native resolves. Ready for another look.

[ChrisJr404]

Closes#2037.

On Windows, DEFAULT_INHERITED_ENV_VARS is missing a few variables that common dev tooling needs. The most impactful one is PATHEXT: without it, spawn('npm', ...) (and git, python, anything else that ships as .cmd/.exe/.bat) fails with ENOENT even when PATH is set, because Node has no extensions to try.

Added to the win32 branch:

• PATHEXT — extensions Windows treats as executable. Fix for the spawn npm ENOENT symptom in the issue.
• COMSPEC — path to cmd.exe; needed by spawn({ shell: true }) and anything that shells out.
• PROGRAMFILES(X86) and PROGRAMW6432 — the other two Program Files paths. Tools that resolve install locations need at least one of these depending on whether the parent is 32-bit or 64-bit.
• WINDIR — used by some legacy tooling that doesn't accept SYSTEMROOT.

Also sorted the array so future additions are easier to eyeball.

Test

Added a small assertion in stdio.test.ts that pins the expected list per platform, so a regression on either branch fails locally. pnpm test is green (365/365) and pnpm lint/pnpm typecheck are clean.

Changeset included as a patch bump on @modelcontextprotocol/client.

[changeset-bot]

🦋 Changeset detected

Latest commit: a379b7a

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 6 packages

Name	Type
@modelcontextprotocol/client	Patch
@modelcontextprotocol/core	Patch
@modelcontextprotocol/server	Patch
@modelcontextprotocol/server-legacy	Patch
@modelcontextprotocol/codemod	Patch
@modelcontextprotocol/core-internal	Patch

Not sure what this means? Click here to learn what changesets are.

Click here if you're a maintainer who wants to add another changeset to this PR

[pkg-pr-new]

Open in StackBlitz

@modelcontextprotocol/client

npm i https://pkg.pr.new/@modelcontextprotocol/client@2043

@modelcontextprotocol/codemod

npm i https://pkg.pr.new/@modelcontextprotocol/codemod@2043

@modelcontextprotocol/core

npm i https://pkg.pr.new/@modelcontextprotocol/core@2043

@modelcontextprotocol/server

npm i https://pkg.pr.new/@modelcontextprotocol/server@2043

@modelcontextprotocol/server-legacy

npm i https://pkg.pr.new/@modelcontextprotocol/server-legacy@2043

@modelcontextprotocol/express

npm i https://pkg.pr.new/@modelcontextprotocol/express@2043

@modelcontextprotocol/fastify

npm i https://pkg.pr.new/@modelcontextprotocol/fastify@2043

@modelcontextprotocol/hono

npm i https://pkg.pr.new/@modelcontextprotocol/hono@2043

@modelcontextprotocol/node

npm i https://pkg.pr.new/@modelcontextprotocol/node@2043

commit: a379b7a

[daxian-dbw]

I can confirm this issue caused troubles to starting executables from within a local stdio MCP server, such as PowerShell, GitHub CLI, and etc.

Especially that PowerShell depends on PATHEXT to discover native executables. Without that environment variable, no native executable can be discovered within PowerShell on Windows.

@jspahrsummers and @anaisbetts, I found you made the decision to not include those environment vars in #36. Could you please give some attention to this fix?

[ChrisJr404]

Rebased onto main. The only conflict was in stdio.test.ts from the import refactor and the new dispose/buffer tests — stdio.ts merged cleanly, all the new env vars are intact. daxian-dbw's confirmation about PowerShell/PATHEXT matches what we saw: without PATHEXT nothing native resolves. Ready for another look.

[ChrisJr404]

Closes#2037.

On Windows, DEFAULT_INHERITED_ENV_VARS is missing a few variables that common dev tooling needs. The most impactful one is PATHEXT: without it, spawn('npm', ...) (and git, python, anything else that ships as .cmd/.exe/.bat) fails with ENOENT even when PATH is set, because Node has no extensions to try.

Added to the win32 branch:

• PATHEXT — extensions Windows treats as executable. Fix for the spawn npm ENOENT symptom in the issue.
• COMSPEC — path to cmd.exe; needed by spawn({ shell: true }) and anything that shells out.
• PROGRAMFILES(X86) and PROGRAMW6432 — the other two Program Files paths. Tools that resolve install locations need at least one of these depending on whether the parent is 32-bit or 64-bit.
• WINDIR — used by some legacy tooling that doesn't accept SYSTEMROOT.

Also sorted the array so future additions are easier to eyeball.

Test

Added a small assertion in stdio.test.ts that pins the expected list per platform, so a regression on either branch fails locally. pnpm test is green (365/365) and pnpm lint/pnpm typecheck are clean.

Changeset included as a patch bump on @modelcontextprotocol/client.

[changeset-bot]

🦋 Changeset detected

Latest commit: a379b7a

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 6 packages

Name	Type
@modelcontextprotocol/client	Patch
@modelcontextprotocol/core	Patch
@modelcontextprotocol/server	Patch
@modelcontextprotocol/server-legacy	Patch
@modelcontextprotocol/codemod	Patch
@modelcontextprotocol/core-internal	Patch

Not sure what this means? Click here to learn what changesets are.

Click here if you're a maintainer who wants to add another changeset to this PR

[pkg-pr-new]

Open in StackBlitz

@modelcontextprotocol/client

npm i https://pkg.pr.new/@modelcontextprotocol/client@2043

@modelcontextprotocol/codemod

npm i https://pkg.pr.new/@modelcontextprotocol/codemod@2043

@modelcontextprotocol/core

npm i https://pkg.pr.new/@modelcontextprotocol/core@2043

@modelcontextprotocol/server

npm i https://pkg.pr.new/@modelcontextprotocol/server@2043

@modelcontextprotocol/server-legacy

npm i https://pkg.pr.new/@modelcontextprotocol/server-legacy@2043

@modelcontextprotocol/express

npm i https://pkg.pr.new/@modelcontextprotocol/express@2043

@modelcontextprotocol/fastify

npm i https://pkg.pr.new/@modelcontextprotocol/fastify@2043

@modelcontextprotocol/hono

npm i https://pkg.pr.new/@modelcontextprotocol/hono@2043

@modelcontextprotocol/node

npm i https://pkg.pr.new/@modelcontextprotocol/node@2043

commit: a379b7a

[daxian-dbw]

I can confirm this issue caused troubles to starting executables from within a local stdio MCP server, such as PowerShell, GitHub CLI, and etc.

Especially that PowerShell depends on PATHEXT to discover native executables. Without that environment variable, no native executable can be discovered within PowerShell on Windows.

@jspahrsummers and @anaisbetts, I found you made the decision to not include those environment vars in #36. Could you please give some attention to this fix?

[ChrisJr404]

Rebased onto main. The only conflict was in stdio.test.ts from the import refactor and the new dispose/buffer tests — stdio.ts merged cleanly, all the new env vars are intact. daxian-dbw's confirmation about PowerShell/PATHEXT matches what we saw: without PATHEXT nothing native resolves. Ready for another look.

[ChrisJr404]

Closes#2037.

On Windows, DEFAULT_INHERITED_ENV_VARS is missing a few variables that common dev tooling needs. The most impactful one is PATHEXT: without it, spawn('npm', ...) (and git, python, anything else that ships as .cmd/.exe/.bat) fails with ENOENT even when PATH is set, because Node has no extensions to try.

Added to the win32 branch:

• PATHEXT — extensions Windows treats as executable. Fix for the spawn npm ENOENT symptom in the issue.
• COMSPEC — path to cmd.exe; needed by spawn({ shell: true }) and anything that shells out.
• PROGRAMFILES(X86) and PROGRAMW6432 — the other two Program Files paths. Tools that resolve install locations need at least one of these depending on whether the parent is 32-bit or 64-bit.
• WINDIR — used by some legacy tooling that doesn't accept SYSTEMROOT.

Also sorted the array so future additions are easier to eyeball.

Test

Added a small assertion in stdio.test.ts that pins the expected list per platform, so a regression on either branch fails locally. pnpm test is green (365/365) and pnpm lint/pnpm typecheck are clean.

Changeset included as a patch bump on @modelcontextprotocol/client.

[changeset-bot]

🦋 Changeset detected

Latest commit: a379b7a

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 6 packages

Name	Type
@modelcontextprotocol/client	Patch
@modelcontextprotocol/core	Patch
@modelcontextprotocol/server	Patch
@modelcontextprotocol/server-legacy	Patch
@modelcontextprotocol/codemod	Patch
@modelcontextprotocol/core-internal	Patch

Not sure what this means? Click here to learn what changesets are.

Click here if you're a maintainer who wants to add another changeset to this PR

[pkg-pr-new]

Open in StackBlitz

@modelcontextprotocol/client

npm i https://pkg.pr.new/@modelcontextprotocol/client@2043

@modelcontextprotocol/codemod

npm i https://pkg.pr.new/@modelcontextprotocol/codemod@2043

@modelcontextprotocol/core

npm i https://pkg.pr.new/@modelcontextprotocol/core@2043

@modelcontextprotocol/server

npm i https://pkg.pr.new/@modelcontextprotocol/server@2043

@modelcontextprotocol/server-legacy

npm i https://pkg.pr.new/@modelcontextprotocol/server-legacy@2043

@modelcontextprotocol/express

npm i https://pkg.pr.new/@modelcontextprotocol/express@2043

@modelcontextprotocol/fastify

npm i https://pkg.pr.new/@modelcontextprotocol/fastify@2043

@modelcontextprotocol/hono

npm i https://pkg.pr.new/@modelcontextprotocol/hono@2043

@modelcontextprotocol/node

npm i https://pkg.pr.new/@modelcontextprotocol/node@2043

commit: a379b7a

[daxian-dbw]

I can confirm this issue caused troubles to starting executables from within a local stdio MCP server, such as PowerShell, GitHub CLI, and etc.

Especially that PowerShell depends on PATHEXT to discover native executables. Without that environment variable, no native executable can be discovered within PowerShell on Windows.

@jspahrsummers and @anaisbetts, I found you made the decision to not include those environment vars in #36. Could you please give some attention to this fix?

[ChrisJr404]

Rebased onto main. The only conflict was in stdio.test.ts from the import refactor and the new dispose/buffer tests — stdio.ts merged cleanly, all the new env vars are intact. daxian-dbw's confirmation about PowerShell/PATHEXT matches what we saw: without PATHEXT nothing native resolves. Ready for another look.

[ChrisJr404]

Closes#2037.

On Windows, DEFAULT_INHERITED_ENV_VARS is missing a few variables that common dev tooling needs. The most impactful one is PATHEXT: without it, spawn('npm', ...) (and git, python, anything else that ships as .cmd/.exe/.bat) fails with ENOENT even when PATH is set, because Node has no extensions to try.

Added to the win32 branch:

• PATHEXT — extensions Windows treats as executable. Fix for the spawn npm ENOENT symptom in the issue.
• COMSPEC — path to cmd.exe; needed by spawn({ shell: true }) and anything that shells out.
• PROGRAMFILES(X86) and PROGRAMW6432 — the other two Program Files paths. Tools that resolve install locations need at least one of these depending on whether the parent is 32-bit or 64-bit.
• WINDIR — used by some legacy tooling that doesn't accept SYSTEMROOT.

Also sorted the array so future additions are easier to eyeball.

Test

Added a small assertion in stdio.test.ts that pins the expected list per platform, so a regression on either branch fails locally. pnpm test is green (365/365) and pnpm lint/pnpm typecheck are clean.

Changeset included as a patch bump on @modelcontextprotocol/client.

[changeset-bot]

🦋 Changeset detected

Latest commit: a379b7a

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 6 packages

Name	Type
@modelcontextprotocol/client	Patch
@modelcontextprotocol/core	Patch
@modelcontextprotocol/server	Patch
@modelcontextprotocol/server-legacy	Patch
@modelcontextprotocol/codemod	Patch
@modelcontextprotocol/core-internal	Patch

Not sure what this means? Click here to learn what changesets are.

Click here if you're a maintainer who wants to add another changeset to this PR

[pkg-pr-new]

Open in StackBlitz

@modelcontextprotocol/client

npm i https://pkg.pr.new/@modelcontextprotocol/client@2043

@modelcontextprotocol/codemod

npm i https://pkg.pr.new/@modelcontextprotocol/codemod@2043

@modelcontextprotocol/core

npm i https://pkg.pr.new/@modelcontextprotocol/core@2043

@modelcontextprotocol/server

npm i https://pkg.pr.new/@modelcontextprotocol/server@2043

@modelcontextprotocol/server-legacy

npm i https://pkg.pr.new/@modelcontextprotocol/server-legacy@2043

@modelcontextprotocol/express

npm i https://pkg.pr.new/@modelcontextprotocol/express@2043

@modelcontextprotocol/fastify

npm i https://pkg.pr.new/@modelcontextprotocol/fastify@2043

@modelcontextprotocol/hono

npm i https://pkg.pr.new/@modelcontextprotocol/hono@2043

@modelcontextprotocol/node

npm i https://pkg.pr.new/@modelcontextprotocol/node@2043

commit: a379b7a

[daxian-dbw]

I can confirm this issue caused troubles to starting executables from within a local stdio MCP server, such as PowerShell, GitHub CLI, and etc.

Especially that PowerShell depends on PATHEXT to discover native executables. Without that environment variable, no native executable can be discovered within PowerShell on Windows.

@jspahrsummers and @anaisbetts, I found you made the decision to not include those environment vars in #36. Could you please give some attention to this fix?

[ChrisJr404]

Rebased onto main. The only conflict was in stdio.test.ts from the import refactor and the new dispose/buffer tests — stdio.ts merged cleanly, all the new env vars are intact. daxian-dbw's confirmation about PowerShell/PATHEXT matches what we saw: without PATHEXT nothing native resolves. Ready for another look.