CPIs in Anchor Best Practices

Typed, safe, minimal cross-program calls for production Anchor 0.32.1 programs.

How to Use This List

Review every new CPI in security PRs.
Pin external IDLs used by declare_program!.
Simulate CPI-heavy instructions on devnet.

A - Validation

Use Program<T> for every CPI target never unchecked program accounts.
Validate remaining_accounts before forward owner, discriminator, freshness.
Cap remaining account count prevent CU griefing.
Pin callee IDL version in repo with release tags.

B - Signing

Use with_signer only with validated PDAs seeds enforced in struct.
Prefer ctx.bumps over recomputing canonical bump.
Avoid CPI in constraint expressions keep side effects in handlers.

FAQs

Anchor 0.32.1 error format?

Custom codes in IDL plus #[msg] strings.

emit! vs emit_cpi!?

emit_cpi! costs more CU but improves capture reliability.

Should I use msg! on mainnet?

Avoid except behind feature flags.

How do clients get error codes?

From IDL via Anchor or Codama codegen.

Do events appear in IDL?

Yes, #[event] types are listed.

Can constraints return custom errors?

Yes with @ MyError::Variant.

What uses CU in logging?

Each log line and formatted string.

How to test errors?

anchor test expecting error codes.

Are logs consensus data?

Yes, but not an API contract; use events.

Next read?

See Related for cpi bp.

Stack versions: This page was written for Agave 4.1.1, Solana CLI 3.0.10, Anchor 0.32.1, anchor-lang 0.32.1, Rust 1.91.1, @solana/kit 7.0.0, Surfpool 0.12.0, and LiteSVM 0.6.x.

Reviewed by Chris St. John·Last updated Jul 16, 2026

Was this article helpful?

Rust Cross Program Invocations Anchor Best Practices List Cpi

CPIs in Anchor Best Practices

Typed, safe, minimal cross-program calls for production Anchor 0.32.1 programs.

How to Use This List

Review every new CPI in security PRs.
Pin external IDLs used by declare_program!.
Simulate CPI-heavy instructions on devnet.

A - Validation

Use Program<T> for every CPI target never unchecked program accounts.
Validate remaining_accounts before forward owner, discriminator, freshness.
Cap remaining account count prevent CU griefing.
Pin callee IDL version in repo with release tags.

B - Signing

Use with_signer only with validated PDAs seeds enforced in struct.
Prefer ctx.bumps over recomputing canonical bump.
Avoid CPI in constraint expressions keep side effects in handlers.

FAQs

Anchor 0.32.1 error format?

Custom codes in IDL plus #[msg] strings.

emit! vs emit_cpi!?

emit_cpi! costs more CU but improves capture reliability.

Should I use msg! on mainnet?

Avoid except behind feature flags.

How do clients get error codes?

From IDL via Anchor or Codama codegen.

Do events appear in IDL?

Yes, #[event] types are listed.

Can constraints return custom errors?

Yes with @ MyError::Variant.

What uses CU in logging?

Each log line and formatted string.

How to test errors?

anchor test expecting error codes.

Are logs consensus data?

Yes, but not an API contract; use events.

Next read?

See Related for cpi bp.

Stack versions: This page was written for Agave 4.1.1, Solana CLI 3.0.10, Anchor 0.32.1, anchor-lang 0.32.1, Rust 1.91.1, @solana/kit 7.0.0, Surfpool 0.12.0, and LiteSVM 0.6.x.

Reviewed by Chris St. John·Last updated Jul 16, 2026

Was this article helpful?

CPIs in Anchor Best Practices

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CPIs in Anchor Best Practices