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Merged
BYK merged 2 commits into from
Sep 18, 2025
Merged

feat(sidecar): Add stdio transport for MCP #933

BYK merged 2 commits into from
Sep 18, 2025

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@BYK BYK commented Sep 17, 2025

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spotlightjs Ready Ready Preview Comment Sep 17, 2025 8:55pm

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looks good! thought this was going to take more time, BYK delivering

Some notes on trying the mcp locally:

  • i was trying to use the spotlight package at first instead of sidecar. shouldn't we expose the --stdio-mcp argument by adding it to packages/spotlight/bin/run.js and passing it to setupSidecar.
  • We should do dynamically change the sidecar port. If it's already running and you run another server, it says that sidecar is already running. this would cause trouble if you want to connect to the mcp and alread have the electron app running. same happened to me when I was trying it on the mcp inspector and then went to cursor (without closing the inspector connection).

packages/sidecar/src/mcp/mcp.ts

export function createMcpInstance() {
export function createMCPInstance() {
const mcp = new McpServer({
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shouldn't we track this with our instrumentation?
WrapMcpServerWithSentry?

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Yes @MathurAditya724 shouldn't we track our stuff? 😀

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BYK commented Sep 17, 2025

i was trying to use the spotlight package at first instead of sidecar. shouldn't we expose the --stdio-mcp argument by adding it to packages/spotlight/bin/run.js and passing it to setupSidecar.

Yes, that was actually my next step once we validated that this thing works. Will add it to this patch.

We should do dynamically change the sidecar port. If it's already running and you run another server, it says that sidecar is already running. this would cause trouble if you want to connect to the mcp and alread have the electron app running. same happened to me when I was trying it on the mcp inspector and then went to cursor (without closing the inspector connection).

This is a great point, thanks for sharing! We cannot create multiple sidecar instances listening on random ports tho as we need to tell the SDKs which sidecar to talk to. Instead, when we detect an existing instance, I'll make the new one a proxy for the other one. Since this is gonna be a bit tricky, I'll do that in a follow up PR tho.

@BYK BYK force-pushed the byk/feat/stdio-mcp branch from 461f1ff to 37b0a02 Compare September 17, 2025 20:53
@BYK BYK force-pushed the byk/feat/stdio-mcp branch from 37b0a02 to d89e980 Compare September 17, 2025 20:54
@BYK BYK requested a review from betegon September 17, 2025 20:55
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thought it looked good from afar, far better up close. reference

@BYK BYK merged commit cec5457 into main Sep 18, 2025
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@BYK BYK deleted the byk/feat/stdio-mcp branch September 18, 2025 12:20
@sentry-release-bot sentry-release-bot bot mentioned this pull request Aug 25, 2025
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betegon pushed a commit that referenced this pull request Sep 20, 2025
@sentry-release-bot @github-actions
meta(changelog): Update package versions (#910)
2180641 
This PR was opened by the [Changesets
release](https://github.com/changesets/action) GitHub action. When
you're ready to do a release, you can merge this and publish to npm
yourself or [setup this action to publish
automatically](https://github.com/changesets/action#with-publishing). If
you're not ready to do a release yet, that's fine, whenever you add more
changesets to main, this PR will be updated.


# Releases
## @spotlightjs/overlay@4.0.0

### Major Changes

- Remove integrations architecture in favour of fixed telemetry features
and remove the ability to use the package as an overlay on top of apps.
([#917](#917))

- Remove all vite-plugins as they are deprecated
([#937](#937))

### Minor Changes

- - Implement URL-based routing in overlay with BrowserRouter for web
apps and HashRouter for Electron
([#921](#921))
- Remove sentry-integration.ts and simplify telemetry implementation
- Moved telemetry logic from App.tsx to dedicated Telemetry component

### Patch Changes

- Remove local resource handling and vite plugin as overlay feature is
not supported ([#924](#924))

- Refactor to remove object destructuring from hooks returning only one
value ([#930](#930))

## @spotlightjs/sidecar@2.0.0

### Major Changes

- Make `setupSidecar` async as it should be
([#936](#936))

- Remove all vite-plugins as they are deprecated
([#937](#937))

### Minor Changes

- Add support for multiple stdio MCP servers to run, as a proxy for the
existing main sidecar
([#935](#935))

- Adds stdio based MCP server via a `--stdio-mcp` CLI argument. Also
removes the context-based message buffers to be able to achieve this as
there's no context-id for the stdio transport. This feature was not used
anyway. ([#933](#933))

Moves all log messages to stderr as they should have been to avoid
clobbering the MCP stdio transport.

### Patch Changes

- - To check all items in an envelope for errors.
([#880](#880))

- restructured the sidecar server and minor improvements
([#918](#918))

- To add a soft reset buffer when its cleared.
([#895](#895))

## @spotlightjs/spotlight@4.0.0

### Major Changes

- Make `setupSidecar` async as it should be
([#936](#936))

- Remove all vite-plugins as they are deprecated
([#937](#937))

### Minor Changes

- Add support for multiple stdio MCP servers to run, as a proxy for the
existing main sidecar
([#935](#935))

- Adds stdio based MCP server via a `--stdio-mcp` CLI argument. Also
removes the context-based message buffers to be able to achieve this as
there's no context-id for the stdio transport. This feature was not used
anyway. ([#933](#933))

Moves all log messages to stderr as they should have been to avoid
clobbering the MCP stdio transport.

### Patch Changes

- Remove local resource handling and vite plugin as overlay feature is
not supported ([#924](#924))

- Updated dependencies
\[[`2fe54bb`](2fe54bb),
[`20783d0`](20783d0),
[`48c6753`](48c6753),
[`65f4e9f`](65f4e9f),
[`bb85759`](bb85759),
[`1f2096e`](1f2096e),
[`cec5457`](cec5457),
[`5670dd4`](5670dd4),
[`605b1e1`](605b1e1),
[`69bfd17`](69bfd17),
[`3d56a55`](3d56a55)]:
    -   @spotlightjs/sidecar@2.0.0
    -   @spotlightjs/overlay@4.0.0

## @spotlightjs/electron@1.8.0

### Minor Changes

- Run electron app in background and add a menu tray
([#929](#929))

- Make app window draggable
([#931](#931))

- Added Auto Updater
([#922](#922))

### Patch Changes

- - Implement URL-based routing in overlay with BrowserRouter for web
apps and HashRouter for Electron
([#921](#921))
- Remove sentry-integration.ts and simplify telemetry implementation
- Moved telemetry logic from App.tsx to dedicated Telemetry component
- Updated dependencies
\[[`2fe54bb`](2fe54bb),
[`20783d0`](20783d0),
[`48c6753`](48c6753),
[`65f4e9f`](65f4e9f),
[`bb85759`](bb85759),
[`1f2096e`](1f2096e),
[`cec5457`](cec5457),
[`5670dd4`](5670dd4),
[`605b1e1`](605b1e1),
[`69bfd17`](69bfd17),
[`3d56a55`](3d56a55)]:
    -   @spotlightjs/sidecar@2.0.0
    -   @spotlightjs/overlay@4.0.0

Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>
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@betegon betegon betegon approved these changes

@MathurAditya724 MathurAditya724 Awaiting requested review from MathurAditya724

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@BYK @betegon