In 2003, Schapker joined the espionage-action series Alias in its third season as an executive story editor and writer. At the beginning of season four, she was promoted to producer, and by the final season, she had been named supervising producer. During her three-season span, Schapker co-wrote twelve episodes total. The installments are as follows:
"A Missing Link"
"After Si"
"Unveiled"
"Blood Ties"
"Détente"
"The Index"
"The Orphan"
"Search and Rescue"
"Prophet Five"
"Bob"
"30 Seconds"
"Reprisal"
''Brothers & Sisters''
In 2006, Schapker was brought on to develop the first season of the ABC dramaBrothers & Sisters as a writer and supervising producer. She then went on to become co-executive producer at the start of season two, and then held the position of executive producer throughout seasons three and four. At the conclusion of the fourth season, Schapker left the show. Episodes she co-wrote are as follows:
In Fall 2006, Schapker joined the third season crew of ABC's Lost, as a writer and supervising producer. She left the series in January 2007. She co-wrote one episode while working on the show, with supervising producer Monica Owusu-Breen, "The Cost of Living".
''Fringe''
After her departure from Brothers & Sisters in Spring 2010, Schapker was hired as a writer and co-executive producer on the FOX science fiction/horror series Fringe, going into its third season. In its fifth season, Schapker retains her third season credits. Episodes she has contributed to include:
"The Plateau"
"Marionette"
"Bloodline"
"The Last Sam Weiss"
"One Night in October"
"Enemy of My Enemy"
"A Better Human Being"
"The Bullet That Saved the World"
"The Human Kind"
"Liberty"
''Almost Human''
From 2013 to 2014, she worked on the FOX series Almost Human. Serving as a co-executive producer and writer until its cancellation.
''The Flash''
In summer 2014, Schapker joined the DC Comics produced CW series The Flash, as a writer and consulting producer. Her first episode to contribute to was the series' third installment, "Things You Can't Outrun", which she co-wrote with Grainne Godfree. The episode featured the introduction of Ronnie Raymond. She next co-wrote the seventh installment, "Power Outage", again with Godfree. Schapker and Brooke Eikmeier co-scripted the series' 11th episode, "The Sound and the Fury". It introduces infamous rogue member The Pied Piper. She and Eikmeier went on to co-write the series' 20th installment, "The Trap".
''Altered Carbon''
In July 2018, it was announced that Schapker will be the co-showrunner and one of the executive producers of the second season of the Netflix science-fiction series, Altered Carbon On May 23, 2019, it was announced that Schapker will be the primary showrunner for the series, replacing Laeta Kalogridis who is still credited as an executive producer.