Bundle MCP gateway config schema in binary via go:embed by Copilot · Pull Request #2933 · github/gh-aw-mcpg

Copilot · 2026-03-31T13:52:03Z

The gateway schema was fetched at runtime from a pinned GitHub raw URL, causing startup failures in network-restricted environments and introducing a hard dependency on external availability.

Changes

Embed schema at build time: Added internal/config/schema/mcp-gateway-config.schema.json (v0.64.4) and a //go:embed directive with a embeddedSchemaBytes variable. getOrCompileSchema() now uses the embedded bytes directly — no network request.
Extract transformation logic: Split fetchAndFixSchema into two functions:
- fixSchemaBytes([]byte) ([]byte, error) — pure JSON transformation (negative-lookahead fix, registry/guard-policies injection)
- fetchAndFixSchema(url string) ([]byte, error) — HTTP fetch + fixSchemaBytes, retained for custom server schema validation
Remove schemaURL package var: The hardcoded GitHub URL is no longer needed for the main schema path. Update instructions are in the comment on embeddedSchemaBytes.
Simplify tests: fetch_and_fix_schema_test.go tests now call fixSchemaBytes directly with marshaled JSON instead of spinning up HTTP mock servers.

// Before: fetched from GitHub at runtime
schemaJSON, fetchErr := fetchAndFixSchema(schemaURL)

// After: uses bundled schema, zero network dependency
schemaJSON, fixErr := fixSchemaBytes(embeddedSchemaBytes)

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-build1174324405/b340/launcher.test /tmp/go-build1174324405/b340/launcher.test -test.testlogfile=/tmp/go-build1174324405/b340/testlog.txt -test.paniconexit0 -test.timeout=10m0s /tmp/go-build1174324405/b240/vet.cfg se 8413017/b047/vet.cfg ache/go/1.25.8/x64/pkg/tool/linux_amd64/vet --gdwarf-5 --64 -o ache/go/1.25.8/x64/pkg/tool/linux_amd64/vet (dns block)
invalid-host-that-does-not-exist-12345.com
- Triggering command: /tmp/go-build31076197/b001/config.test /tmp/go-build31076197/b001/config.test -test.testlogfile=/tmp/go-build31076197/b001/testlog.txt -test.paniconexit0 -test.timeout=10m0s -test.run=TestFetchAndFixSchema -test.v=true --local .13/x64/as user.email (dns block)
- Triggering command: /tmp/go-build2540153460/b001/config.test /tmp/go-build2540153460/b001/config.test -test.testlogfile=/tmp/go-build2540153460/b001/testlog.txt -test.paniconexit0 -test.timeout=10m0s -test.v=true 64/src/runtime/cgo 64/src/log/internal/internal.go ache/go/1.25.8/x64/pkg/tool/linu-o gpg.program (dns block)
- Triggering command: /tmp/go-build3088080346/b001/config.test /tmp/go-build3088080346/b001/config.test -test.testlogfile=/tmp/go-build3088080346/b001/testlog.txt -test.paniconexit0 -test.timeout=10m0s go_.�� 8958092/b096/_pkg_.a (dns block)
nonexistent.local
- Triggering command: /tmp/go-build1174324405/b340/launcher.test /tmp/go-build1174324405/b340/launcher.test -test.testlogfile=/tmp/go-build1174324405/b340/testlog.txt -test.paniconexit0 -test.timeout=10m0s /tmp/go-build1174324405/b240/vet.cfg se 8413017/b047/vet.cfg ache/go/1.25.8/x64/pkg/tool/linux_amd64/vet --gdwarf-5 --64 -o ache/go/1.25.8/x64/pkg/tool/linux_amd64/vet (dns block)
slow.example.com
- Triggering command: /tmp/go-build1174324405/b340/launcher.test /tmp/go-build1174324405/b340/launcher.test -test.testlogfile=/tmp/go-build1174324405/b340/testlog.txt -test.paniconexit0 -test.timeout=10m0s /tmp/go-build1174324405/b240/vet.cfg se 8413017/b047/vet.cfg ache/go/1.25.8/x64/pkg/tool/linux_amd64/vet --gdwarf-5 --64 -o ache/go/1.25.8/x64/pkg/tool/linux_amd64/vet (dns block)
this-host-does-not-exist-12345.com
- Triggering command: /tmp/go-build1174324405/b349/mcp.test /tmp/go-build1174324405/b349/mcp.test -test.testlogfile=/tmp/go-build1174324405/b349/testlog.txt -test.paniconexit0 -test.timeout=10m0s /tmp/go-build1174324405/b256/vet.cfg se 8413017/b038/vet.cfg ache/go/1.25.8/x64/pkg/tool/linux_amd64/vet (compatibility issue with Go 1.25.0). Continuing with other checks..."; \ elif command -v golan vendor/golang.or-unsafeptr=false -lang=go1.25 ache/go/1.25.8/x64/pkg/tool/linux_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)

…rk fetch Agent-Logs-Url: https://github.com/github/gh-aw-mcpg/sessions/e18d275d-1cfe-4125-8dd3-b0a394ea8a68 Co-authored-by: lpcox <15877973+lpcox@users.noreply.github.com>

…dedSchemaID constant Agent-Logs-Url: https://github.com/github/gh-aw-mcpg/sessions/e18d275d-1cfe-4125-8dd3-b0a394ea8a68 Co-authored-by: lpcox <15877973+lpcox@users.noreply.github.com>

Move //go:embed directive to immediately before the var declaration, after the doc comment block, as required by gofmt. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Copilot

Pull request overview

This PR removes the MCP Gateway’s runtime dependency on fetching its JSON Schema over the network by bundling the schema into the binary with go:embed, while keeping remote fetch behavior for validating custom server schemas.

Changes:

Embedded the MCP gateway config JSON Schema at build time and switched schema compilation to use embedded bytes (no runtime HTTP fetch).
Refactored schema transformation logic into a pure fixSchemaBytes helper and reused it from both embedded and remote fetch paths.
Updated tests to exercise schema-fix behavior directly from bytes rather than via HTTP test servers.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 3 comments.

File	Description
internal/config/validation_schema.go	Embeds the schema and refactors schema fix/fetch/compile flow to remove runtime network dependency.
internal/config/validation_schema_test.go	Updates schema configuration test to validate embedded schema presence and compilation.
internal/config/schema/mcp-gateway-config.schema.json	Adds the bundled MCP Gateway configuration schema JSON file to the repo.
internal/config/fetch_and_fix_schema_test.go	Simplifies transformation tests to call `fixSchemaBytes` directly.

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Copilot · 2026-03-31T14:55:03Z

internal/config/validation_schema.go

+func fixSchemaBytes(schemaBytes []byte) ([]byte, error) {
 	fixStart := time.Now()
 	var schema map[string]interface{}
 	if err := json.Unmarshal(schemaBytes, &schema); err != nil {


fixSchemaBytes currently removes the type: "string" constraint from definitions.customServerConfig.properties.type (and only adds a not enum). That makes schema validation accept non-string values (e.g., numbers/objects) as a valid custom server type and drops the type-name format constraints, weakening config validation and producing less helpful downstream unmarshal errors. Suggest keeping type: "string" and replacing only the negative-lookahead portion with a Draft-7-safe equivalent (e.g., preserve the allowed-name pattern and add a not enum for reserved types).

Copilot · 2026-03-31T14:55:03Z

internal/config/validation_schema.go

 	}
 	logSchema.Printf("Schema fixes applied in %v", time.Since(fixStart))

-	logSchema.Printf("Total schema fetch and fix completed in %v", time.Since(startTime))
 	return fixedBytes, nil


fixSchemaBytes unconditionally injects/overwrites several properties (e.g., trustedBots, guard-policies) in the schema map. Now that the bundled schema version already includes some of these fields, this risks clobbering upstream definitions/descriptions and leaves the inline comment about the field being absent in older released schemas stale. Consider only injecting these properties if they are missing (and refresh/remove the version-specific comment) to avoid silently diverging from the embedded schema source-of-truth.

Copilot · 2026-03-31T14:55:04Z

internal/config/schema/mcp-gateway-config.schema.json

+        "port": 8080,
+        "domain": "localhost",
+        "startupTimeout": 60,
+        "toolTimeout": 120


The second entry in the examples array has gateway missing the required apiKey field (gatewayConfig.required includes apiKey). Examples should be valid instances of the schema to avoid confusing users and downstream tooling; add an apiKey to this example (or adjust required fields if apiKey is intentionally optional).

Suggested change

"toolTimeout": 120

"toolTimeout": 120,

"apiKey": "gateway-secret-token"

Initial plan

95feb7b

Copilot AI assigned Copilot and lpcox Mar 31, 2026

Copilot started work on behalf of lpcox March 31, 2026 13:53 View session

Copilot AI linked an issue Mar 31, 2026 that may be closed by this pull request

Schema outdated and failed to download #2932

Closed

Copilot AI and others added 2 commits March 31, 2026 14:02

Bundle MCP gateway schema in binary using go:embed, eliminating netwo…

cea6dc9

…rk fetch Agent-Logs-Url: https://github.com/github/gh-aw-mcpg/sessions/e18d275d-1cfe-4125-8dd3-b0a394ea8a68 Co-authored-by: lpcox <15877973+lpcox@users.noreply.github.com>

Address review comments: add schema version comment and extract embed…

d2f3671

…dedSchemaID constant Agent-Logs-Url: https://github.com/github/gh-aw-mcpg/sessions/e18d275d-1cfe-4125-8dd3-b0a394ea8a68 Co-authored-by: lpcox <15877973+lpcox@users.noreply.github.com>

Copilot AI changed the title ~~[WIP] Update gateway schema to bundle in go program~~ Bundle MCP gateway config schema in binary via go:embed Mar 31, 2026

Copilot finished work on behalf of lpcox March 31, 2026 14:05

Copilot AI requested a review from lpcox March 31, 2026 14:05

lpcox and others added 2 commits March 31, 2026 07:44

style: fix gofmt formatting for go:embed directive

cf64d7b

Move //go:embed directive to immediately before the var declaration, after the doc comment block, as required by gofmt. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Merge branch 'main' into copilot/update-gateway-schema-fetch

94efd9c

lpcox marked this pull request as ready for review March 31, 2026 14:50

Copilot AI review requested due to automatic review settings March 31, 2026 14:50

lpcox merged commit 1e9fee1 into main Mar 31, 2026
13 checks passed

lpcox deleted the copilot/update-gateway-schema-fetch branch March 31, 2026 14:50

Copilot started reviewing on behalf of lpcox March 31, 2026 14:51 View session

Copilot AI reviewed Mar 31, 2026

View reviewed changes

This was referenced Mar 31, 2026

Smoke Test: Copilot - 23803792661 #2937

Closed

[ca] Update CLI versions: MCP Gateway v0.2.11, Playwright Browser v1.59.0, Playwright MCP 0.0.70 github/gh-aw#23820

Closed

Copilot AI mentioned this pull request Apr 1, 2026

feat: bump MCP Gateway v0.2.11, Playwright Browser v1.59.0, Playwright MCP 0.0.70, Firewall v0.25.6 github/gh-aw#23821

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Bundle MCP gateway config schema in binary via go:embed#2933

Bundle MCP gateway config schema in binary via go:embed#2933
lpcox merged 5 commits intomainfrom
copilot/update-gateway-schema-fetch

Copilot AI commented Mar 31, 2026 •

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	"toolTimeout": 120
	"toolTimeout": 120,
	"apiKey": "gateway-secret-token"

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

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Pull request overview

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Copilot AI commented Mar 31, 2026 •

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