Bitcoin Core v32.0rc1 Introduces Wallet Protocol Changes and Performance Updates

Bitcoin Core v32.0rc1, released on Sept. 14, marks a focused compatibility window for node operators, wallet providers, and services that rely on Core’s RPC interfaces. The candidate is a prerelease and does not activate new consensus rules.

Key Changes in the Release Candidate

• Parallel prefetching of transaction outputs during block connection, defaulting to eight worker threads (up to 16, configurable, and can be disabled).
• PSBT handling – four RPCs now default to PSBTv2, and deprecated fields are removed, causing older parsers to reject certain arguments.
• Fee estimation – the default estimatesmartfee combines block‑policy and mempool estimators, may return lower estimates, and can error if either component fails.
• HTTP RPC server – header size limit set to 8,192 bytes, stricter malformed‑header handling, default ceiling of 16 RPC connections, new REST cache controls, and immediate disconnection of unauthorized clients.
• Transaction index rebuild – new format uses less than half the disk space; older releases cannot read it, making downgrades trigger a lengthy rebuild.
• Privacy and Tor fixes – updated private‑broadcast failure paths, queue limits, and relay behavior under load.

Testing Recommendations

Operators should follow the Bitcoin Core RC testing guide: run the candidate in a separate data directory, compare node startup, wallet behavior, and RPC responses against the current baseline (v31.1). Specific tests include:

1. Assess block processing speed versus CPU, memory, and storage latency with different prefetch worker settings.
2. Validate PSBT creation, conversion, and fee‑bumping workflows through downstream parsers and signers.
3. Monitor estimatesmartfee under sparse or unhealthy mempool conditions and verify fallback behavior.
4. Check HTTP RPC interactions, especially header limits, connection caps, and unauthorized client handling, in environments using reverse proxies or health checks.
5. Confirm that the rebuilt transaction index functions correctly and that downgrades are avoided.
6. Test private‑broadcast mechanisms with Tor, respecting the new queue and attempt limits.

Release Timeline

The final v32.0 tag is targeted for Oct. 10, giving a 26‑day window from the RC tag. The schedule shifted from an earlier Sept. 10 target, but the deadline remains unchanged.