Update cli/azd/extensions/azure.ai.agents/internal/cmd/session.go

Co-authored-by: Jon Gallant <2163001+jongio@users.noreply.github.com>

Author: therealjohn

cli/azd/extensions/azure.ai.agents/internal/cmd/session.go

@@ -418,11 +418,23 @@ The isolation key is derived from the Entra token by default.`,
 				flags.isolationKey,
 				DefaultVNextAgentAPIVersion,
 			)
-			if err != nil {
-				return exterrors.ServiceFromAzure(
-					err, exterrors.OpDeleteSession,
-				)
-			}
+if err != nil {
+if respErr, ok := errors.AsType[*azcore.ResponseError](err); ok &&
+respErr.StatusCode == http.StatusNotFound {
+return exterrors.Validation(
+exterrors.CodeSessionNotFound,
+fmt.Sprintf(
+"session %q not found or has already been deleted",
+sessionID,
+),
+"use 'azd ai agent sessions list' to see "+
+"available sessions",
+)
+}
+return exterrors.ServiceFromAzure(
+err, exterrors.OpDeleteSession,
+)
+}
 
 			fmt.Printf(
 				"Session %q deleted from agent %q.\n",