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feat(sdk)!: raise CPI limits to 64 metas and 4 signer groups - #21
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solana.Invoke, the SDK-2 C runtime and sdk/cpi allowed 16 account metas and 2 signer groups per CPI; Hyperlane's Sealevel programs need 22 (IGP PayForGas with quoted accounts) and 17 (fee QuoteFee). Seeds keep 16 per group, 32 bytes each and 1,024 encoded bytes. sol_Invoke gets 64-entry meta and 4x16 seed descriptor arrays and is noinline, so its 2,240-byte frame never lands in a caller's frame. cpi.Metas keeps 16 records inline and moves them to one 576-byte heap array at the 17th Add, so small CPIs keep their frame and zeroing cost. examples/cpi-limits and TestCPILimitsSBF run 3 to 64 metas with up to four PDA signers on fogo-v0 and solana-v3 against a C callee that checks its account count, signers and every repeated-account position, plus the 65-meta and 5-group errors through the builders and the raw boundary. The escrow, full-swap and tutorial SDK snapshots are refreshed; the check corpus records the 33 C hashes the runtime change moved.
results/compiler/2026-10-19-cpi-limits holds the before/after CU of the CPI-limits harness and the existing escrow, full-swap and tutorial suites, static frame sizes, and the fresh-rebuild metrics. The full swap's ELFs changed (fogo-v0 bcd9253e, solana-v3 86f0ed15), so verify_rebuild.py now defaults to this reference. HANDOFF records the SDK snapshot change.
paulbalaji
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Problem
CPIs are capped at 16 metas and 2 signer groups, well under the runtime's limits. Hyperlane needs up to 22: a quoted IGP payment takes 22 and a fee quote 17. Both fail with 3002 or 2006.
Solution
Raise the limits to 64 metas and 4 signer groups; seeds are unchanged. Why 64: agave caps account infos at 64 (128 behind a feature gate), and 255 metas would need about 4 KiB of descriptors, the whole frame.
sol_Invokeis no longer inlined. Its frame grows from 960 to 2,240 bytes; callers' frames don't change.cpi.Metasstays inline up to 16 and moves to a 576-byte heap array on the 17thAdd.Benchmarks
fogo-v0; solana-v3 within a few CU:
solana.Invoke, 3 metasTests
19 CPI cases on both profiles, from 3 to 64 metas and 0 to 4 groups, through builders and raw
Invoke. A C callee asserts the account count, signers and positions. 65 metas and 5 groups are rejected.Breaking: the SDK snapshot changes, so existing SDK-2 projects must be recreated.
Linked work
Closes #4. Used by hyperlane-xyz/hyperlane-monorepo#9852.