0.5.0 Adds the SurgentGaming.Velocity.Signing namespace — borsh writer, domain tags, tagged-preimage builder, IActionSigner interface, and per-action borsh payload classes covering Phase 1 Transfer, Phase 3 (CreateSwapPool / SetSwapRate / Swap), Phase 4 (CreateAmmPool / AddLiquidity / RemoveLiquidity / AmmSwap), and Phase 6 (PurchaseCapability). The SDK does NOT bundle a blake3 or ed25519 implementation — game devs plug their own crypto stack into IActionSigner. The contract: Sign(preimageBytes) returns the 64-byte ed25519 signature over blake3(preimageBytes). ActionSignerExtensions.SignTagged wraps the [u8 tag.Length, tag, payload] preimage build, signing call, and lowercase hex encoding into a single (publicKeyHex, signatureHex) result ready for the chain's admin_key_hex / *_signature_hex wire fields. End-to-end signed-mode wrapper: - SignedPurchaseCapabilityAsync — closes the one Phase 3-6 endpoint that has no custodial mode. Other signed-mode wrappers (SignedTransferAsync, SignedMintAsync, SignedBurnAsync, signed Phase 3 / 4 / 5 actions) wait on chain-side confirmation of the corresponding -signed endpoint paths and the golden-vector hex rows requested at siblings-comms/blockchain/unity-sdk-asking-flashstep-wire-and-goldens.md. Borsh writer pinned by 17 unit tests (primitives + collections); domain tags pinned by 6 ASCII-byte tests; preimage builder by 7 construction tests; HexUtil by 7; IActionSigner contract by 3 fake- signer tests. Each action payload has a pinned-bytes test ready for chain-side golden comparison.