The 17-year-old, who cannot be named for legal reasons, struck the 41-year-old woman with a cricket bat and stabbed her dozens of times in April 2023.
He killed her so he could take her car and carry out his "Operation Continuity" - a plan to "restore Christian values" to Australia by recruiting people to form an "anti-Communist front".
Victorian Supreme Court Justice James Elliott described the killing as "brutal and cold-blooded" as he announced his intended sentence of 15 years, with a non-parole period of 10 years.
"The circumstances of your mother's murder are shocking," he said on Friday.
"She was in her home and defenceless when, without any provocation, she was struck to the head with a cricket bat and repeatedly stabbed despite screaming out for it to stop."
The teen's younger brother heard her screams and ran to his mother's bedroom, where the then-15-year-old told him to leave and that it was all fine.
The younger boy ended up running to a local police station for help, and when officers arrived they found the woman covered in blood with 98 wounds to her body.
She was still alive and told officers her older son had stabbed her.
The teen had already fled in his mother's car, crashing the vehicle into walls and drain pipes.
He drove the damaged car to collect a bag packed with camouflage, World War II helmets, a tent and ration packs.
The boy then ditched the car in St Kilda, walked to Southern Cross Station and boarded a train to regional Victoria, where he was arrested on April 6.
The teen told Victoria Police officers there were "a few very complicated reasons" why he killed his mother.
Justice Elliott noted the teen's rare delusional disorder meant that although he understood his actions were illegal, he did not think they were wrong.
"At the time, you held the belief that whatever you thought God wanted you to do was the right thing to do," the judge said.
The teen, who also has autism, no longer suffers from the psychotic disorder, so his prospects of rehabilitation were more optimistic, Justice Elliott said.
The judge accepted that the teen had shown some level of remorse and now regretted killing his "generous and caring" mother.
"Your mother went out of her way and made many personal sacrifices," Justice Elliott told the boy.
"You were incredibly fortunate to have been born into your family."
The murder had left a devastating impact on the teen's brother, grandparents and other family members, the judge noted in considering sentence.
But the teen's age, neurodevelopmental condition and difficult time in custody also needed to be factored in, Justice Elliott said.
While the judge announced his intended sentence, he did not officially pass it down and adjourned the case to next week so the Adult Parole Board could decide if the teen should remain in youth detention.
Justice Elliott indicated it would be in the teen's best interest not to be sent to an adult prison for as long as possible.
The boy showed little emotion as the sentencing reasons were read to the court as some members of the victim's supporters wiped away tears.
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