CHALLANGES

Understanding the ecosystem

I started from 0 the only thing I knew of ZEC was that it has privacy features, the ticker and my balance on CEX. The zcash ecosystem can be a bit confusing, nodes, wallets, libraries.

I acquired the knowledge for the appropriate and up2date tools. (And thx to NEAR intents I was confident to fully offboard from CEX)

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ZIP-317 Fee Calculation Mismatch

I calculated fees differently than the Builder, causing "ChangeRequired" errors when amounts didn't balance

I matched the Builder's exact formula:

5000 * max(2, logical_actions)

.

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Upstream Library Breaking Changes

Initially I created a fork and fixed the bugs (https://github.com/gstohl/librustzcash/tree/pczt-append-transparent-sigs) and added needed features of library branch https://github.com/zcash/librustzcash/tree/pczt-append-transparent-sigs. When upstream fixed things and added features, method names and signatures changed.

After upstream updated I had to migrated to it, so I needed to update renamed methods and new error variants.

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Cross-Language Memory Management

Rust uses ownership/borrowing, but Go/TypeScript/Kotlin/Java have garbage collection.

I serialize PCZT to bytes at FFI boundary, each language manages its own copy.

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Bridge Solution Selection

I had to choose from multiple options for each language (cgo vs pure Go, N-API vs WASM vs KOFFI, JNI vs JNA) with different tradeoffs.

I selected based on maintainability:

• Go → cgo
• TypeScript → koffi
• Kotlin/Java → JNA

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Unified Workflow Across Languages

Each language has different idioms for error handling, async, and byte arrays.

I wrapped the same C FFI but made each binding feel native, for example:

• Go: multiple return values for errors
• TypeScript: promises and thrown exceptions
• Kotlin/Java: exceptions with ByteArray/byte[]

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Submission Video

The hardest challenge was to make the submission video