Learn Hardcore Indonesian: Kapan pun kamu siap, saya akan datang langsung. - Whenever you are ready, I will come directly.

It means “whenever.” Write it as two words: kapan pun. The particle pun functions like “-ever/any,” and in standard Indonesian it is written separately after question words (e.g., apa pun, siapa pun, kapan pun, di mana pun). You may see “kapanpun” informally, but it’s nonstandard.

Is kapan pun the same as kapan saja or setiap kali?

kapan pun ≈ kapan saja: both mean “whenever/any time.” kapan saja sounds a bit more colloquial; kapan pun is neutral to slightly more formal.
setiap kali means “every time (each time),” emphasizing repeated occurrences rather than open-ended permission. In most everyday contexts, you can swap kapan pun and kapan saja, but not always with setiap kali.

Do I need the comma after the opening clause Kapan pun kamu siap?

Yes. When a subordinate clause comes first, Indonesian convention uses a comma: Kapan pun kamu siap, ... If you put the main clause first, you normally don’t use a comma: Saya akan langsung datang kapan pun kamu siap.

Can I switch the clause order without changing the meaning?

Yes:

Kapan pun kamu siap, saya akan langsung datang.
Saya akan langsung datang kapan pun kamu siap. Both are natural.

What nuance does langsung add? Should I use segera or saat itu juga instead?

langsung emphasizes doing something “straight away/straight to (without detours)” and often implies immediacy through directness.
segera emphasizes “soon/at once” (time-based urgency).
saat itu juga means “right then and there/that very moment,” the strongest for immediacy. In your sentence, langsung feels like “I’ll come straight over.” If you want to stress urgency more than directness, use segera. For maximum immediacy, use saat itu juga.

Where should I place langsung—before or after datang?

Common and natural placements:

Saya akan langsung datang. (most common)
Saya akan datang langsung. (also acceptable; reads more like a manner adverb “come directly”) Avoid odd orders like Saya langsung akan datang (rare/awkward) or adding a preposition (dengan langsung, ungrammatical).

Is akan required to show future meaning?

No. Indonesian often relies on context for future time. All are possible:

Kapan pun kamu siap, saya langsung datang. (future understood from context)
Kapan pun kamu siap, saya akan langsung datang. (akan makes the promise/plan explicit; common in careful speech/writing) Use akan when you want to sound clear, planned, or slightly more formal.

Are kamu and saya a natural pairing? What about aku or Anda?

kamu = you (informal/neutral); aku = I/me (informal/intimate).
Anda = you (polite/formal; capitalized); saya = I/me (neutral/formal). Typical pairings:
Informal/intimate: aku–kamu
Formal/polite: saya–Anda
Neutral and common today: saya–kamu (acceptable in many contexts) Choose based on relationship and formality.

Can I say Kapan pun kamu sudah siap? What does sudah change?

You can, but it shifts the focus to the completion point (“whenever you have become ready”). In practice, most speakers would just say Kapan pun kamu siap or use:

Begitu kamu siap, ... (“As soon as you’re ready, ...”)
Kalau kamu sudah siap, ... (“If/when you’re already ready, ...”) Adding sudah with kapan pun can feel a bit heavy unless you really mean the completed state.

Is siap a verb or an adjective here? Why is there no “to be” word?

siap is an adjective (“ready”). Indonesian does not require a copula (“to be”) before adjectives, so kamu siap = “you are ready.” Don’t use adalah with adjectives; adalah is for equating nouns (e.g., Dia adalah guru).

Do I need to specify a destination with datang?

Not necessarily. datang (“come”) can stand alone when the destination is obvious from context—here, “to you.” If needed, add a ke-phrase:

Saya akan langsung datang ke rumahmu/kantormu.
... ke tempatmu.

How else can I phrase this (more formal, more casual, or more precise)?

More formal/polite: Kapan pun Anda siap, saya akan segera/langsung datang.
Emphasize immediacy: Begitu kamu siap, saya akan datang saat itu juga.
Casual: Kalau kamu siap, aku langsung ke situ.
Emphasize repeated availability: Setiap kali kamu siap, saya akan langsung datang.

How does the particle pun work in general? What other patterns should I know?

With question words, pun makes “-ever/any”: apa pun, siapa pun, kapan pun, di mana pun, mana pun, berapa pun.
As “even,” pun follows the word/phrase: Saya pun setuju (“Even I agree”), Dia pun datang.
Spelling: usually separate. A few fixed forms are written together, e.g., walaupun, meskipun, sekalipun, bagaimanapun, adapun.