[poolski]

A discovery sweep listed each connected server's tools one after another, so one slow or large upstream delayed every other server's tools/list by up to its own timeout.

The sweep now lists up to 8 servers at once (discoveryListConcurrency). Results are recorded in the original order with the same logging, markSwept and capture handling. A server's concurrent tools/list calls were already coalesced into one request, and each capture carries its own process-global sequence, so the order in which lists finish does not change how their results are applied.

TestDiscoverToolsListsServersConcurrently uses three upstreams whose tools/list waits for another list to be in flight and requires the sweep to overlap them.

Testing

• go test -race ./internal/upstream/...
• scripts/test-api-e2e.sh (70/70)
• golangci-lint with .github/.golangci.yml, bare and --build-tags server: no new issues

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[Dumbris]

Thanks — clean change, cross-model review (gpt-6.1-sol) came back clean too. The one gap was that nothing asserted the upper bound (removing the semaphore left every test green), so I pushed TestDiscoverToolsBoundsConcurrentLists (12 servers, asserts peak ≤ discoveryListConcurrency; verified it fails without the semaphore). Auto-merge is armed.

[Dumbris]

Merged. Thank you, @poolski! Discovery sweeps used to wait on each upstream's tools/list in turn, so one slow server delayed all of them by up to its own timeout; listing up to eight at once makes a fleet of upstreams index in roughly the time of the slowest one.

Contributions like this are what keep MCPProxy moving, and they matter a lot to the project.

One small ask, only if you feel like it: a short public note about your change (a tweet, a LinkedIn post, a line in a community you are part of) helps more people discover MCPProxy. No pressure at all, and I would be glad to repost it.