IDL / JSON Input

What layoutd reads#

layoutd’s primary input is the Anchor IDL JSON — the same IDL your program already emits. You provide two versions of it and select which account to compare with --account <Name>. For zero-copy structs where the IDL is insufficient, the Rust source can be used as a fallback.

• Primary: Anchor IDL JSON (the common path).
• Fallback: the account’s Rust source, for zero-copy layouts.
• Optional: a hint file for facts the tool can’t infer, such as confirmed renames.

Producing the two version files#

Export the IDL at the old commit and the new commit, then point layoutd at both. The account-type entry layoutd reads for UserState looks like this:

{"name": "UserState","type": {"kind": "struct","fields": ["name": "authority", "type": "publicKey" },"name": "balance",   "type": "u64" },"name": "bump",      "type": "u8" }    ]  }}

{"name": "UserState","type": {"kind": "struct","fields": ["name": "authority", "type": "publicKey" },"name": "is_active", "type": "bool" },"name": "balance",   "type": "u64" },"name": "bump",      "type": "u8" }    ]  }}

The only difference above is the inserted is_active field in v2.json — which is exactly the change layoutd flags as DANGER, because it shifts the offsets of balance and bump.

Selecting the account#

An IDL can contain many accounts. Use --account to pick the one you want to diff:

layoutd diff v1.json v2.json --account UserState

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