previewChangePlan: mixed currencies in response with no per-line-item conversion

[codeweft]

Description

The previewChangePlan response mixes two currencies in a single payload — line items are in USD while the summary is in the customer's adaptive currency (e.g. AUD). There are no converted amounts provided, making it impossible to build a fully localised plan change confirmation UI.

Steps to Reproduce

1. Enable Adaptive Currency in Business Settings (Test Mode)
2. Customer billing country: AU — triggers AUD adaptive currency
3. Products: Pro at $9/mo USD, Teams at $29/mo USD
4. Call subscriptions.previewChangePlan(subId, { product_id: teamsProductId, proration_billing_mode: "prorated_immediately", quantity: 1 })

Actual Response (abbreviated)

{
  "immediate_charge": {
    "summary": {
      "total_amount": 147,
      "currency": "AUD",
      "settlement_amount": 100,
      "settlement_currency": "USD"
    },
    "line_items": [
      { "name": "Pro",   "unit_price": 900,  "currency": "USD", "proration_factor": -0.9997 },
      { "name": "Teams", "unit_price": 2900, "currency": "USD", "proration_factor": 1.0 }
    ]
  }
}

Problem

• Line items have currency: "USD" with USD unit_price values
• The summary total_amount is in AUD (the customer's card currency)
• The summary settlement_amount is in USD
• There is no AUD-converted amount on each line item

This means a single response contains three currency contexts (USD line items, AUD card charge, USD settlement) with no per-line-item conversion. It is not possible to show the customer what each proration line is worth in their local currency without implementing exchange rate conversion independently.

Expected Behaviour

Either:

• Option A: Provide converted unit_price amounts on each line item in the customer's local currency alongside the existing USD values
• Option B: Document clearly that line items are always in USD and the summary total_amount / currency is the card charge in local currency — so integrators know to display them as separate sections

Environment

• SDK: dodopayments 2.23.2
• Mode: Test Mode
• Adaptive Currency: Enabled
• Customer billing country: AU (Australia)