Guide
How the kit works
Special Delivery brings Lumi in with an Electro attack, puts her in Yellow Light Mode and grants Yellow Light Spark. Searchlight Service also makes her Pounce when she enters the field, without spending STA.
In Yellow Light, Navigation Support fires three ranged shots. Dodge starts a Sprint and puts Lumi into Zoom Mode, where she automatically shoots Glitters at a locked-on target. Glitter hits count as Basic Attack DMG. Lumi cannot Dodge while she is sprinting, so watch the enemy before committing to it.
Yellow Light attacks and Glitters build Yellow Light Spark. Under Signal Light, filling the gauge replaces the skill with Energized Pounce. Use it to deal Electro DMG and enter Red Spotlight Mode. Its damage counts as Basic Attack DMG. Red Spotlight strengthens Red Light Basic and Heavy Attacks and gives extra Spark recovery; it ends after four of those attacks in total.
In Red Light or Red Spotlight, hits from Navigation Support recover Red Light Spark. When it is full, use Energized Rebound to deal Electro DMG counted as Basic Attack DMG and enter Yellow Spotlight Mode. There, Glitter becomes the stronger Glare and recovers extra Spark. The mode ends after six Glares.
Both Spark gauges hold up to 100. Escorting (outro) consumes the Sparks from the current mode; at 25 or more, it can fire Laser. Every 25 Sparks adds a beam, up to four. Use Squeakie Express for an Electro hit, then switch when you are ready to pass on the Outro buff.
Build and why
Moonlit Clouds is a recommended set option. Its two-piece effect gives 10% Energy Regen, which suits a build that wants access to Lumi's Resonance Liberation. Void Thunder is the damage-focused alternative: its two-piece effect gives 10% Electro DMG. The game's build lists a five-piece Void Thunder setup.
Lustrous Razor is the first weapon to consider. It gives 12.8% Energy Regen, and casting Resonance Skill grants 7% Resonance Liberation DMG Bonus for 12 seconds, stacking up to three times. Lumi uses her skill to change modes, so she has opportunities to trigger it.
Ages of Harvest gives 12% Attribute DMG Bonus and has Resonance Skill DMG Bonus effects after Intro and skill casts. Its skill bonuses should not be mistaken for Basic Attack DMG bonuses: Energized Pounce and Energized Rebound are classified as Basic Attack DMG. Verdant Summit also gives 12% Attribute DMG Bonus, though its Heavy Attack DMG Bonus should not be assumed to boost Red Light Heavy Attack, which counts as Basic Attack DMG.
For a four-star option, Autumntrace gives ATK when Lumi deals Basic Attack or Heavy Attack DMG. Discord is worth considering if you want its Concerto Energy recovery after casting the skill. ATK and Energy Regen are useful stats to consider, but the supplied build does not specify Echo stat slots.
Leveling priority
A suggested leveling order is Signal Light first, followed by Navigation Support. The first covers Lumi's enhanced attacks and Laser, while the second covers the attacks she uses in both modes.
After those, consider Squeakie Express, then Searchlight Service and Special Delivery. This order gives attention to her field damage first; the skill also controls her mode changes, while the Intro provides an entry attack.
For maximum ascension, gather 170,000 Shell Credit, 4 LF Howler Core, 12 MF Howler Core, 12 HF Howler Core, 4 FF Howler Core, 46 Thundering Tacet Core and 60 Terraspawn Fungus.
Leveling all skills to maximum takes 2,030,000 Shell Credit, 25 LF Howler Core, 28 MF Howler Core, 40 HF Howler Core, 57 FF Howler Core, 26 Sentinel's Dagger, 25 Waveworn Residue 210, 28 Waveworn Residue 226, 55 Waveworn Residue 235 and 67 Waveworn Residue 239.
Resonance Chain nodes worth it
A suggested node to look at is Captain Lumi, At Your Service (sequence 4), which grants 30% Basic Attack DMG Bonus. It matches several parts of Lumi's kit, including her enhanced skill hits and Laser.
Lollo Logistics, Ready to Help (sequence 2) is another useful option: Energized Pounce and Energized Rebound ignore 20% of the target's DEF. Give Me A Five-star Rating (sequence 6) instead adds team value, giving all team members 20% ATK for 20 seconds when Lumi casts her Liberation.
If you are choosing a stopping point, node 4 is worth considering for Lumi's own Basic Attack DMG. Node 6 is more appealing if you also want the team ATK effect. Parcel Collected On Time (sequence 5) increases Laser's DMG Multiplier by 100% when Spark is full, so switching with a full gauge matters more if you have it.
Teams
Lumi wants an incoming damage dealer who can use Resonance Skill DMG Amplification. Escorting (outro) gives that character 38% amplification for 10 seconds, but it ends early if they switch out. Plan their field time around that window.
Hsin, Carlotta and Changli are guide-named partners to consider. Jinhsi and Phrolova are other options. Check which attacks you intend to use during the buff window: Lumi amplifies Resonance Skill DMG, not every hit the next character deals.
A third slot can cover whatever the team still needs, such as sustain or other support. Shorekeeper, Verina and Baizhi are also named in the guides. Lumi's buff does not require the incoming character to have a particular element.
Common mistakes
Do not treat Sprint as a normal Dodge. It starts Zoom Mode, but Lumi cannot Dodge while performing it. If an enemy is about to attack, account for that before starting the Sprint.
Do not switch out without checking the Spark gauge. Below 25 Sparks, Laser cannot fire. More Sparks add beams, up to four, so waiting can give Lumi a stronger exit attack when the fight allows it.
Do not build around a damage label just because it appears on the button. Energized Pounce and Energized Rebound are cast through Resonance Skill, but their damage counts as Basic Attack DMG. Red Light Heavy Attack also counts as Basic Attack DMG.
Do not pass the Outro buff to a character and immediately switch them out. The 38% Resonance Skill DMG Amplification ends on switch, even if its 10 seconds have not elapsed.
