fix: set brownfield Foundry projectName without ACR

cli/azd/extensions/azure.ai.agents/CHANGELOG.md

@@ -4,6 +4,7 @@
 
 ### Bugs Fixed
 
+- [[#8917]](https://github.com/Azure/azure-dev/pull/8917) Fix an `InvalidTemplate` error when deploying a brownfield (`endpoint:`) Foundry project that declares model deployments without creating a container registry. The `projectName` ARM parameter is now always set, so the referenced `Microsoft.CognitiveServices/accounts/projects` resource gets a valid two-segment name.
 - [[#8901]](https://github.com/Azure/azure-dev/pull/8901) Remove duplicate service-target provider claims from the `azure.ai.agents` extension manifest for hosts now owned by the split Foundry extensions (`azure.ai.projects`, `azure.ai.connections`, `azure.ai.toolboxes`). Thanks @huimiu for the contribution!
 
 ## 1.0.0-beta.1 (2026-06-30)

cli/azd/extensions/azure.ai.agents/internal/project/foundry_provisioning_provider.go

@@ -810,11 +810,15 @@ func (p *FoundryProvisioningProvider) brownfieldParams(
 	params := map[string]any{
 		"accountName": map[string]any{"value": account},
 		"deployments": map[string]any{"value": p.brownfieldDeployments},
+		// projectName is always required: the template unconditionally references
+		// the existing accounts/projects resource, whose ARM name is
+		// '<accountName>/<projectName>'. Leaving it empty yields a single-segment
+		// name and an InvalidTemplate error even when no ACR is created.
+		"projectName": map[string]any{"value": p.brownfieldProjectName()},
 	}
 	if createACR {
 		params["includeAcr"] = map[string]any{"value": true}
 		params["acrName"] = map[string]any{"value": p.brownfieldACRName(account)}
-		params["projectName"] = map[string]any{"value": p.brownfieldProjectName()}
 		params["tags"] = map[string]any{"value": map[string]string{"azd-env-name": p.envName}}
 		// Only set location when resolved; an empty value would override the
 		// template default (resourceGroup().location) and fail the deployment.

cli/azd/extensions/azure.ai.agents/internal/project/foundry_provisioning_provider_brownfield_acr_test.go

@@ -172,13 +172,20 @@ func TestBrownfieldParams(t *testing.T) {
 
 	deployments := []synthesis.Deployment{{Name: "gpt-4o-mini"}}
 
-	t.Run("without ACR carries only account and deployments", func(t *testing.T) {
+	t.Run("without ACR carries account, deployments and projectName", func(t *testing.T) {
 		t.Parallel()
-		p := &FoundryProvisioningProvider{envName: "dev", brownfieldDeployments: deployments}
+		p := &FoundryProvisioningProvider{
+			envName:               "dev",
+			brownfieldDeployments: deployments,
+			brownfieldEndpoint:    "https://acct.services.ai.azure.com/api/projects/my-project",
+		}
 		params := p.brownfieldParams(t.Context(), "acct", "rg", false)
 
 		assert.Equal(t, map[string]any{"value": "acct"}, params["accountName"])
 		assert.Equal(t, map[string]any{"value": deployments}, params["deployments"])
+		// projectName is always required so the existing accounts/projects
+		// resource gets a valid two-segment ARM name.
+		assert.Equal(t, map[string]any{"value": "my-project"}, params["projectName"])
 		assert.NotContains(t, params, "includeAcr")
 		assert.NotContains(t, params, "acrName")
 	})