Fix upstream format detection for registries with $schema

The legacy registry format also includes a $schema key, so checking
for $schema alone incorrectly classified legacy files as upstream.
Use the "data" wrapper object as the sole discriminator since only
the upstream format wraps servers inside it.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: rdimitrov

pkg/config/registry.go

@@ -333,19 +333,16 @@ func setRegistryFile(provider Provider, registryPath string) error {
 }
 
 // isUpstreamRegistryFormat returns true if the JSON data appears to be in the
-// upstream MCP registry format (has "$schema" or "data" wrapper object).
+// upstream MCP registry format. The key discriminator is the "data" wrapper
+// object — only the upstream format wraps servers inside it.
 func isUpstreamRegistryFormat(data []byte) bool {
 	var probe struct {
-		Schema string          `json:"$schema"`
-		Data   json.RawMessage `json:"data"`
+		Data json.RawMessage `json:"data"`
 	}
 	if err := json.Unmarshal(data, &probe); err != nil {
 		return false
 	}
-	if probe.Schema != "" {
-		return true
-	}
-	// data must be a JSON object (starts with '{'), not a primitive
+	// The "data" wrapper object is unique to the upstream format.
 	return len(probe.Data) > 0 && probe.Data[0] == '{'
 }
 

pkg/registry/upstream_parser.go

@@ -64,18 +64,15 @@ type upstreamFormatProbe struct {
 }
 
 // isUpstreamFormat returns true when the raw JSON appears to be in the upstream
-// registry format. It checks for the presence of a "$schema" key or a "data"
-// wrapper object (must be a JSON object, not a string/number), both of which
-// are unique to the upstream format.
+// registry format. The key discriminator is the "data" wrapper object — only
+// the upstream format wraps servers inside a "data" object. The "$schema" key
+// alone is not sufficient because the legacy format also includes one.
 func isUpstreamFormat(data []byte) bool {
 	var probe upstreamFormatProbe
 	if err := json.Unmarshal(data, &probe); err != nil {
 		return false
 	}
-	if probe.Schema != "" {
-		return true
-	}
-	// data must be a JSON object (starts with '{'), not a primitive
+	// The "data" wrapper object is unique to the upstream format.
 	return len(probe.Data) > 0 && probe.Data[0] == '{'
 }