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ci(mcp-diff): prebuild HTTP server and fail when a side is unreachable #3440

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Merged
SamMorrowDrums merged 1 commit into from
Oct 6, 2026
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ci(mcp-diff): prebuild HTTP server and fail when a side is unreachable #3440

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25 changes: 24 additions & 1 deletion .github/workflows/mcp-diff.yml
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Original file line number Diff line number Diff line change
Expand Up @@ -119,18 +119,41 @@ jobs:
} >> "$GITHUB_OUTPUT"

- name: Run MCP Server Diff (streamable-http)
id: diff
# Pinned to mcp-server-diff v3.0.0 — see rationale on the stdio job above.
# The action sleeps http_startup_wait_ms and then probes, with no
# readiness check. Build the binary in install_command (which runs to
# completion on both the current and baseline checkouts before the
# server is started) so the wait only covers process startup, not
# compilation. Using `go run` here let compile time on the uncached
# baseline checkout exceed the wait, so every baseline probe failed.
uses: SamMorrowDrums/mcp-server-diff@40d992e0a220e5b63378758f9a40d6a8982898d2 # v3.0.0
with:
setup_go: "false"
install_command: |
go mod download
mkdir -p pkg/github/ui_dist
cp "${RUNNER_TEMP}"/ui_dist/*.html pkg/github/ui_dist/
http_start_command: go run ./cmd/github-mcp-server http --port 8082
go build -o bin/github-mcp-server ./cmd/github-mcp-server
http_start_command: ./bin/github-mcp-server http --port 8082
http_startup_wait_ms: "5000"
configurations: ${{ steps.configs.outputs.configurations }}

- name: Verify both sides were probed
# mcp-server-diff treats a configuration that fails on only one side as
# "missing on that ref" (non-fatal) and diffs against an empty
# baseline, so fail_on_error does not catch an unreachable server.
# With a single shared HTTP server, a one-sided failure always means
# that side's server never came up, so fail the job explicitly.
env:
REPORT: ${{ steps.diff.outputs.json_report_path }}
run: |
jq -e 'all(.results[]; .configMissing == null)' "$REPORT" > /dev/null || {
jq -r '.results[] | select(.configMissing) | "::error::\(.configName): server unreachable on \(.configMissing.side) side: \(.configMissing.error)"' "$REPORT"
exit 1
}
jq -r '.results[] | "\(.configName): base=\(.baseProtocolVersion) head=\(.branchProtocolVersion) tools base=\(.baseCounts.tools) head=\(.branchCounts.tools)"' "$REPORT"

- name: Add interpretation note
if: always()
run: |
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