[OttoAllmendinger]

Problem

pairedWallet.sendMany({ ..., unstakingParams: { pox5: { branch: 'early-exit', principalPreimage } } }) on a custodial PoX-5 paired wallet created a pending approval whose stored buildParams had no unstakingParams, so the server built a late-exit PSBT (locktime = unlock height, no preimage) instead of an early exit. The SDK dropped the field in three places before the request left the client:

• BuildParams (buildParamKeys) did not list unstakingParams
• Wallet.initiateTransaction picked only the keys of TxSendBody from @bitgo/public-types, which does not declare unstakingParams
• the TxSendBody codec is exact and strips unknown keys on encode

Change

• Add unstakingParams to BuildParams and PrebuildTransactionOptions.
• Extend the initiate whitelist and codec locally (TxInitiateBody, whitelistedInitiateParams in wallet.ts) until @bitgo/public-types declares it on TxSendBody.
• Unit test (custodialInitiate.ts): the encoded initiate body keeps unstakingParams.

Testing

• modules/sdk-core: custodialInitiate.ts (2 passing); prettier and eslint clean on touched files.
• Live (staging tbtcstx, 2026-11-02, SI-2167): a custodial PoX-5 early exit via sendMany({ unstakingParams: { pox5: { branch: 'early-exit', principalPreimage } } }) with this change passed end to end (tx 6fde203b632e5e6baabed754396ab165fe35df5841f486ce78b23b083a43ac6b). The server-side halves, Wallet Platform (BitGo/bitgo-microservices#63950 and BitGo/bitgo-microservices#63958), and HSM firmware 3.79.3 were deployed on staging for the run.
• The only CI failure on the previous head was Starknet deploy account RPC wire format (live Sepolia) in sdk-coin-starknet, a live-network test unrelated to this change.

Follow-up

@bitgo/public-types 7.2.0 (latest) does not declare unstakingParams on TxSendBody, so the local TxInitiateBody extension stays. Tracked in SI-2170; once published, drop the extension and bump the dependency.

Refs: SI-2167

🤖 Generated with Claude Code

[linear-code]

SI-2167

[github-actions]

⚠️ Compatibility checks are failing on Node.js 27-nightly (experimental, non-blocking). This does not block merge, but it signals an incompatibility to fix before this release becomes supported.

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[claude]

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