fix(provider): normalize --protocol before named-provider conflict check

Normalize the raw --protocol value in ResolveNamedProvider before
comparing it against the spec's protocol. An invalid value (e.g.
"openai_api") now surfaces the clear "unknown --protocol" error listing
the accepted set, instead of a misleading conflict message; valid
aliases no longer falsely conflict.

Author: smallnest

internal/provider/resolve.go

@@ -136,9 +136,18 @@ func ResolveNamedProvider(name, model, baseURL, protocol string, env func(string
 		return nil, "", fmt.Errorf("unknown --provider %q (available: %s)", name, strings.Join(ProviderNames(), ", "))
 	}
 	// A concurrently-set --protocol must agree with the provider's own protocol;
-	// an incompatible pair is a user error naming both flags.
-	if p := strings.TrimSpace(protocol); p != "" && p != spec.Protocol {
-		return nil, "", fmt.Errorf("--provider %q speaks the %q protocol, which conflicts with --protocol %q; drop --protocol or set it to %q", name, spec.Protocol, p, spec.Protocol)
+	// an incompatible pair is a user error naming both flags. Normalize the raw
+	// value first so aliases (e.g. "openai/chat" for an "openai" spec) don't
+	// falsely conflict, and a genuine typo surfaces as a clear "unknown --protocol"
+	// error rather than a misleading conflict message.
+	if strings.TrimSpace(protocol) != "" {
+		canonical, err := NormalizeProtocol(protocol)
+		if err != nil {
+			return nil, "", err
+		}
+		if canonical != spec.Protocol {
+			return nil, "", fmt.Errorf("--provider %q speaks the %q protocol, which conflicts with --protocol %q; drop --protocol or set it to %q", name, spec.Protocol, protocol, spec.Protocol)
+		}
 	}
 	// Special-auth providers (Azure / Bedrock / Vertex / Cloudflare) compose
 	// their endpoint from several env vars and/or need non-standard credential

internal/provider/resolve_test.go

@@ -158,6 +158,16 @@ func TestResolveProviderExplicitProvider(t *testing.T) {
 	if !strings.Contains(err.Error(), "deepseek") {
 		t.Errorf("unknown-provider error should list available names, got: %v", err)
 	}
+	// An invalid --protocol paired with a named provider surfaces the clear
+	// "unknown --protocol" error (listing the accepted set) rather than a
+	// misleading conflict message.
+	_, _, err = ResolveProvider("deepseek-chat", "", "openai_api", "deepseek", os.Getenv)
+	if err == nil {
+		t.Fatal("provider=deepseek + protocol=openai_api should error")
+	}
+	if !strings.Contains(err.Error(), "unknown --protocol") {
+		t.Errorf("invalid --protocol should surface the unknown-protocol error, got: %v", err)
+	}
 }
 
 // TestResolveProviderCNPresets verifies the Chinese-cloud preset ids route to