fix(samples/frontend): scale default quote amount by source currency decimals

[pengying]

The quote step hardcoded lockedCurrencyAmount=1000, which is $10.00 in USD
(2 decimals) but only 0.001 USDC (6 decimals) — below corridor minimums,
causing AMOUNT_OUT_OF_RANGE when funding from USDC. Default to 10 major
units scaled by the source currency's decimals (USD->1000, USDC->10000000).

Co-Authored-By: Claude Opus 4.8 (1M context) noreply@anthropic.com

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Project	Deployment	Actions	Updated (UTC)
grid-flow-builder	Ignored	Preview	Jun 18, 2026 8:49pm
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[pengying]

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This pull request is not mergeable via GitHub because a downstack PR is open. Once all requirements are satisfied, merge this PR as a stack on Graphite.
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• fix(samples/frontend): floor default quote amount to corridor minimum #605
• fix(samples/frontend): scale default quote amount by source currency decimals #604 👈 (View in Graphite)
• fix(samples/kotlin): select crypto network when funding a quote from USDC #603
• feat(samples/kotlin): add exchange-rates lookup flow #602
• feat(samples/kotlin): add USD → USDC wallet payout flow #593
• fix(samples/kotlin): send customer email for USDB embedded wallets #590
• feat(samples/kotlin): support GRID_API_BASE_URL override #589
• main

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[greptile-apps]

Greptile Summary

This PR fixes a bug in the CreateQuote sample step where lockedCurrencyAmount was hardcoded to 1000, which is $10.00 in USD but only 0.001 USDC — well below corridor minimums, causing AMOUNT_OUT_OF_RANGE errors when a user selected USDC as the source currency.

• Introduces SOURCE_CURRENCY_DECIMALS ({ USD: 2, USDC: 6 }) and DEFAULT_SEND_UNITS = 10, then computes lockedCurrencyAmount = DEFAULT_SEND_UNITS * 10 ** decimals inside the useEffect. USD behaviour is unchanged (1000 = $10.00); USDC now correctly produces 10,000,000 (~10 USDC).
• A ?? 2 fallback guards against any future currency not yet listed in the decimals map, preserving USD-like behaviour as a safe default.

Confidence Score: 5/5

Safe to merge — the change is a targeted fix to a sample UI default value with no backend or data-model impact.

The fix is a small arithmetic expression computed entirely from a hardcoded lookup table with integer exponents. For both listed currencies the result is an exact integer within JS's safe-integer range (USD→1000, USDC→10,000,000), so there are no floating-point concerns. The ?? 2 fallback is a sensible default. No new state, no new API paths, no auth changes.

No files require special attention.

Important Files Changed

Filename	Overview
samples/frontend/src/steps/CreateQuote.tsx	Adds SOURCE_CURRENCY_DECIMALS map and DEFAULT_SEND_UNITS constant to compute a correctly-scaled lockedCurrencyAmount per source currency; math is exact for all listed decimal values.

Flowchart

%%{init: {'theme': 'neutral'}}%%
flowchart TD
    A[User selects sourceCurrency] --> B{sourceCurrency in\nSOURCE_CURRENCY_DECIMALS?}
    B -- Yes --> C["decimals = SOURCE_CURRENCY_DECIMALS[sourceCurrency]\n(USD→2, USDC→6)"]
    B -- No\n(fallback) --> D[decimals = 2]
    C --> E["lockedCurrencyAmount =\nDEFAULT_SEND_UNITS × 10^decimals\n(USD→1000, USDC→10 000 000)"]
    D --> E
    E --> F[setBody with updated quote payload]
    F --> G[User submits → POST /api/quotes]

Loading

%%{init: {'theme': 'base', 'themeVariables': {"darkMode": true, "background": "#0d1117", "primaryColor": "#21262d", "primaryTextColor": "#e6edf3", "primaryBorderColor": "#8b949e", "lineColor": "#8b949e", "textColor": "#e6edf3", "edgeLabelBackground": "#161b22", "actorBkg": "#21262d", "actorBorder": "#8b949e", "actorTextColor": "#e6edf3", "actorLineColor": "#8b949e", "signalColor": "#8b949e", "signalTextColor": "#e6edf3", "noteBkgColor": "#373320", "noteBorderColor": "#d4a72c", "noteTextColor": "#f0e6c0", "labelBoxBkgColor": "#21262d", "labelBoxBorderColor": "#8b949e", "labelTextColor": "#e6edf3", "loopTextColor": "#e6edf3", "activationBkgColor": "#30363d", "activationBorderColor": "#8b949e"}}}%%
flowchart TD
    A[User selects sourceCurrency] --> B{sourceCurrency in\nSOURCE_CURRENCY_DECIMALS?}
    B -- Yes --> C["decimals = SOURCE_CURRENCY_DECIMALS[sourceCurrency]\n(USD→2, USDC→6)"]
    B -- No\n(fallback) --> D[decimals = 2]
    C --> E["lockedCurrencyAmount =\nDEFAULT_SEND_UNITS × 10^decimals\n(USD→1000, USDC→10 000 000)"]
    D --> E
    E --> F[setBody with updated quote payload]
    F --> G[User submits → POST /api/quotes]

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