refactor: split oversized files by responsibility (mcp/connection, proxy/handler, httputil)

[Copilot]

Three files had grown beyond single-responsibility: mcp/connection.go (749 lines, 4 distinct concerns), proxy/handler.go (618 lines, HTTP dispatch mixed with JSON transforms), and httputil/httputil.go (generic utilities mixed with GitHub-specific helpers). Pure mechanical splits — zero logic changes.

internal/mcp/connection.go → 4 files

File	Responsibility
connection.go	Lifecycle: NewConnection, NewHTTPConnection, Close, reconnect*, SendRequest*
connection_methods.go	RPC dispatch: callSDKMethod, listTools, callTool, listResources, readResource, listPrompts, getPrompt
connection_logging.go	RPC logging: logOutboundRPCRequest, logInboundRPC*, logReconnect*
pagination.go	Generic helpers: paginateAll, listMCPItems, marshalToResponse, unmarshalParams, callParamMethod

internal/proxy/handler.go → new response_transform.go

Extracted 5 pure data-manipulation utilities that had no business sitting in the HTTP handler layer:

// response_transform.go
func deepCloneJSON(v interface{}) interface{}
func rewrapSearchResponse(originalData, filteredItems interface{}) interface{}
func unwrapSingleObject(originalData, filteredData interface{}) interface{}
func replaceNodesArray(v interface{}, items []interface{}) bool
func rebuildGraphQLResponse(originalData interface{}, filtered *difc.FilteredCollectionLabeledData) interface{}

internal/httputil/httputil.go → new github_http.go

Follows the existing envutil/github.go pattern — GitHub-specific helpers extracted to a dedicated file:

httputil.go       ← WriteJSONResponse, IsTransientHTTPError
github_http.go    ← GitHubUserAgent, ApplyGitHubAPIHeaders, ParseRateLimitResetHeader

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• example.com
  • Triggering command: /tmp/go-build864305169/b509/launcher.test /tmp/go-build864305169/b509/launcher.test -test.testlogfile=/tmp/go-build864305169/b509/testlog.txt -test.paniconexit0 -test.timeout=10m0s -test.v=true ache/go/1.25.9/x64/src/runtime/c--gdwarf-5 8J3C/BnJLWL_dWV6lGp5L8J3C x_amd64/compile (dns block)
  • Triggering command: /tmp/go-build1786442162/b513/launcher.test /tmp/go-build1786442162/b513/launcher.test -test.testlogfile=/tmp/go-build1786442162/b513/testlog.txt -test.paniconexit0 -test.timeout=10m0s (dns block)
• invalid-host-that-does-not-exist-12345.com
  • Triggering command: /tmp/go-build864305169/b491/config.test /tmp/go-build864305169/b491/config.test -test.testlogfile=/tmp/go-build864305169/b491/testlog.txt -test.paniconexit0 -test.timeout=10m0s -test.v=true rnal/descopts/op-errorsas ache/go/1.25.9/x-ifaceassert x_amd64/compile (dns block)
  • Triggering command: /tmp/go-build1786442162/b495/config.test /tmp/go-build1786442162/b495/config.test -test.testlogfile=/tmp/go-build1786442162/b495/testlog.txt -test.paniconexit0 -test.timeout=10m0s (dns block)
• nonexistent.local
  • Triggering command: /tmp/go-build864305169/b509/launcher.test /tmp/go-build864305169/b509/launcher.test -test.testlogfile=/tmp/go-build864305169/b509/testlog.txt -test.paniconexit0 -test.timeout=10m0s -test.v=true ache/go/1.25.9/x64/src/runtime/c--gdwarf-5 8J3C/BnJLWL_dWV6lGp5L8J3C x_amd64/compile (dns block)
  • Triggering command: /tmp/go-build1786442162/b513/launcher.test /tmp/go-build1786442162/b513/launcher.test -test.testlogfile=/tmp/go-build1786442162/b513/testlog.txt -test.paniconexit0 -test.timeout=10m0s (dns block)
• slow.example.com
  • Triggering command: /tmp/go-build864305169/b509/launcher.test /tmp/go-build864305169/b509/launcher.test -test.testlogfile=/tmp/go-build864305169/b509/testlog.txt -test.paniconexit0 -test.timeout=10m0s -test.v=true ache/go/1.25.9/x64/src/runtime/c--gdwarf-5 8J3C/BnJLWL_dWV6lGp5L8J3C x_amd64/compile (dns block)
  • Triggering command: /tmp/go-build1786442162/b513/launcher.test /tmp/go-build1786442162/b513/launcher.test -test.testlogfile=/tmp/go-build1786442162/b513/testlog.txt -test.paniconexit0 -test.timeout=10m0s (dns block)
• this-host-does-not-exist-12345.com
  • Triggering command: /tmp/go-build864305169/b518/mcp.test /tmp/go-build864305169/b518/mcp.test -test.testlogfile=/tmp/go-build864305169/b518/testlog.txt -test.paniconexit0 -test.timeout=10m0s -test.v=true -quiet 649241/b151/ x_amd64/vet -I . -imultiarch x_amd64/vet 6492�� 1.80.0/balancer/balancer.go 1.80.0/balancer/conn_state_evalu-nolocalimports x_amd64/vet --gdwarf-5 --64 -o jk0CHzx/dUnZUsTpJceORqTvO77n (dns block)
  • Triggering command: /tmp/go-build1786442162/b522/mcp.test /tmp/go-build1786442162/b522/mcp.test -test.testlogfile=/tmp/go-build1786442162/b522/testlog.txt -test.paniconexit0 -test.timeout=10m0s -o /tmp/go-build175649241/b461/_pkg-p -trimpath x_amd64/vet -p github.com/githu/usr/bin/runc -lang=go1.25 x_amd64/vet -uns�� -unreachable=false /tmp/go-build864305169/b035/vet.-nolocalimports x_amd64/vet -c=4 -nolocalimports -importcfg x_amd64/vet (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

[Copilot]

Pull request overview

Refactors oversized internal packages by splitting mixed-responsibility Go files into smaller units (MCP connection/pagination/logging, proxy response transforms, and GitHub-specific HTTP utilities) while keeping behavior the same.

Changes:

• Split internal/mcp/connection.go into dedicated files for SDK method dispatch, RPC logging, and pagination/helpers.
• Extract proxy JSON response transformation helpers from handler.go into response_transform.go.
• Extract GitHub-specific HTTP helpers from httputil.go into github_http.go.

Show a summary per file

File	Description
internal/mcp/connection.go	Removes logging/SDK dispatch/pagination helpers that were moved into dedicated files.
internal/mcp/connection_methods.go	New file containing SDK RPC method dispatch and list/call/read wrappers.
internal/mcp/connection_logging.go	New file containing reconnect + RPC request/response logging helpers.
internal/mcp/pagination.go	New file containing shared marshal/unmarshal helpers and pagination utilities.
internal/proxy/handler.go	Removes response-shape transformation helpers now living outside the HTTP handler.
internal/proxy/response_transform.go	New file containing JSON response transformation + deep-clone helpers.
internal/httputil/httputil.go	Keeps generic HTTP helpers; removes GitHub-specific helpers.
internal/httputil/github_http.go	New file containing GitHub-specific headers + rate limit reset parsing.

Copilot's findings

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• Files reviewed: 8/8 changed files
• Comments generated: 1