What changed

A [commit in the CIPs repository](https://github.com/cardano-foundation/CIPs/commit/b37289bacbd45acca805a41b72d71ce61b57538a) on 2026-10-01 added the index limit and CPU charging behaviour to CIP-0156’s Specification. The amendment describes both as behaviours of an existing implementation. It also adds an explanation of the cap to the Rationale and ticks the first acceptance criterion.

Why it matters

For code using `multiIndexArray`, 1024 indices is the stated maximum per call; 1025 produces a failed call under the documented behaviour. Larger permitted calls also carry CPU charges that grow with the square of the index count. The written boundary gives implementers and conformance test authors a specific case to check.

The amendment lists an argument-order amendment under Discussions, but the supplied record does not say what that amendment changes. Anyone relying on an older draft’s argument order needs the current CIP text to establish it.

What to watch

Watch for conformance tests that exercise the 1024-index boundary, along with evidence identifying the implementation and where the documented behaviour is deployed.

Sources and limits

Upstream references and independent checks

Digest dated 2026-10-02 · upstream model sonnet. Direct links are matched to all 1 upstream source IDs.

  1. 1
    CIP-0156 | Specify index count limit for `multiIndexArray` (#1245)Direct upstream source · 517fa3e6da006de442082382a2bd23b5c18f4ea7

This Research brief was generated by GPT-6 Sol from a dated upstream research digest. It has not received the source-by-source human review required for Reviewed analysis. Material limit: The record covers one repository commit. It does not identify the implementation, establish where it is deployed, or state CIP-0156’s status; it is no evidence of a new release, hard fork, or cost-model change.