Intelligent Devices (インテリジェントデバイス Interijiento Debaisu) are Devices that incorporate sophisticated artificial intelligence in their programming, enabling them to have some degree of autonomy. Most Intelligent Devices seen in the series utilise the Midchildan or Modern Belkan magic system and speak English, though Steed shows that Japanese-speaking models are available to civilians. Intelligent Devices appear almost sentient, possessing their own thoughts and personalities. Subaru Nakajima has on several occasions spoken of her own Device, Mach Caliber as a friend or partner ("aibō") rather than a mere tool, which Mach Caliber reciprocates, calling Subaru her "buddy".
If an Intelligent Device does not "agree" that a maintenance operation is complete, it can persistently manifest its "displeasure" with an error code. Both Raising Heart and Bardiche, after severe damage from the Wolkenritter's Armed Devices, raise code E203 and request the Administrative Bureau to install a CVK-792-compatible system — more precisely, the Belkan cartridge system — into their systems. In The MOVIE 1st, Raising Heart elaborates that Intelligent Devices are "merely vehicles", and require proper "drivers" to display their maximum potential. In other words, Intelligent Devices are tools to properly utilize magical energy, but can only operate with limited functionality on their own.
Intelligent Devices may even exercise their will in choosing the mages they will serve. Though Yuuno Scrya was Raising Heart's original owner, she refused to accept him as her Master. As Devices need to synchronize to a mage's brain, presumably Raising Heart could examine Yuuno and judge him to be incompatible with her purpose as a shooting/bombardment weapon. By contrast, Raising Heart instantly and fully accepted Nanoha Takamachi as her Master after making the contract between them, which presumably served as the synchronization process.
Before that, Raising Heart did accept Yuuno so far as to register him as a Guest user, allowing him limited access to her searching and sealing functions. So an Intelligent Device might reject a mage based on incompatibility, but cooperate with a mage based on trust. Similarly, Raising Heart would later acknowledge Vivio Takamachi as another Guest user, helping Nanoha's adopted daughter to practice magic and cooperation with a Device until Vivio received one of her own.
- Asteion (Einhard Stratos)
- Bardiche (Fate Testarossa)
- Blitz Caliber (Ginga Nakajima)
- Brunzel (Corona Timil)
- Cross Mirage (Teana Lanster)
- Huracan (Fuka Reventon)
- Luciferion (Material-S)
- Mach Caliber (Subaru Nakajima)
- Raising Heart (Nanoha Takamachi)
- Sacred Heart (Vivio)
- Solfège (Rio Wesley)
- Star Saber (Miura Rinaldi)
- Steed (Thoma Avenir)
- Storm Raider (Vice Granscenic)
- Vulnificus (Material-L)