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spec-consensus-param

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Draft an Algorand specification (sibling specs repo) update describing a new or changed consensus parameter in go-algorand. Use when the user asks to "update the spec for <param>", "document <feature> in the specs repo", or "write a spec update for a new consensus parameter".

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Spec Update for a Consensus Parameter

Turn a new/changed consensus parameter in go-algorand into a normative update to the Algorand Specification in the sibling specs repo. The goal is prose that reads as though the feature has always been part of the protocol, matching the surrounding spec's style and rigor.

This skill ships in the go-algorand repo and assumes it runs from that repo's root. The specification source is in a separate checkout of algorandfoundation/specs, commonly a sibling directory at ../specs. If it is elsewhere (or not checked out), ask the user for its path before editing.

Arguments

The name of the consensus parameter (the field on config.ConsensusParams), e.g. AppSizeUpdates. If omitted, ask which parameter, or infer it from the branch/PR under discussion.

Step 1: Understand the parameter in go-algorand

  1. Read the declaration and its doc comment:

    grep -rn "<PARAM>" config/consensus.go

    The comment usually states the intent. Note which vFuture/version block sets it true — that tells you the protocol version, but see the style rule in Step 4.

  2. Find everywhere it gates behavior, separating the two layers:

    grep -rn "\.<PARAM>" --include=*.go | grep -v _test.go
    • Stateless validation (wellFormed, data/transactions/...): what transactions/fields become newly legal or newly rejected.
    • Stateful semantics (ledger/apply/..., ledger/eval/...): what actually changes in account/application/asset state, MBR accounting, and in what order relative to program execution.

  3. Find supporting surface area the spec may need to mention:

    • New persisted fields: data/basics/userBalance.go (and ledger/store/trackerdb).
    • New AVM fields/opcodes: data/transactions/logic/fields.go (these are usually already regenerated into the spec's src/avm/avm-appendix-a.md via make logic).
    • New REST fields: daemon/algod/api/.../model/types.go (codec + json name).
    • goal surface: cmd/goal/....

  4. Read the introducing PR for rationale and the full blast radius:

    git log -S "<PARAM>" --oneline
git show <commit> --stat

Summarize to the user, in one paragraph, what the parameter does across both layers before touching the spec. Confirm your understanding of any subtle rule (shrink limits, who pays MBR, ordering, which sibling fields are affected but not changed).

Step 2: Locate the spec files

Spec source lives under <specs>/src (e.g. ../specs/src). Find the affected pages:

grep -rln "<relevant terms>" ../specs/src

Application/asset/payment features usually touch a field page, a semantics page, and a data model page. For apps, that is typically:

  • src/ledger/ledger-txn-application-call.md — transaction fields.
  • src/ledger/ledger-txn-semantics-application.md — the numbered procedure.
  • src/ledger/ledger-applications.md — the persistent data model and MBR rules.

Read all candidate pages fully before editing; the spec is cross-referential and consistent wording matters.

Step 3: Write the update

Cover, as applicable, each layer you found in Step 1:

  • Data model page: change field descriptions (e.g. drop "immutable"), add any new persisted field with its msgpack codec name and AVM exposure, and update MBR prose. If the feature adds a genuinely new concept, add a dedicated ## section.
  • Fields page: adjust when/where a field applies; state validation constraints.
  • Semantics page: add the effect into the correct numbered step, using the FAIL/SUCCEED vocabulary already in that file.

Step 4: Conventions (follow exactly)

  • Describe only the current protocol, as one coherent version. Do NOT write "from the protocol version that introduces X" or "as of vN" for ledger/transaction rules. A rule that changed simply reads in its new form; the old form drops out.
    • Exception: AVM-version gating persists ("For AVM Version 4 or higher..."), because old programs must still be evaluated under old AVM rules — so old AVM versions are part of the current protocol. Ledger/transaction rules are not versioned this way.
  • Normative keywords: MUST, MUST NOT, MAY, SHALL, and the FAIL/SUCCEED terms in semantics pages. Bold them as the surrounding text does.
  • Math and constants use the LaTeX macros defined in the $...$ block at the top of each page (e.g. \\( \MaxGlobalSchemaEntries \\)). Reuse existing macros; only add a new \newcommand if the constant is genuinely new.
  • Cross-reference with relative links plus lowercase-hyphenated heading anchors, e.g. [size sponsor](./ledger-applications.md#size-sponsor), [Step 6](./ledger-txn-semantics-application.md#step-6).
  • Codec names: cite the real msgpack tag from the Go struct (e.g. SizeSponsor is ss), not a guess.
  • Match the page's existing voice, list style, and line-wrapping.

Step 5: Review

git -C ../specs diff | cat

Check that: any pre-existing uncommitted spec changes (often auto-generated AVM appendix/opcode files from make logic) are left untouched; every new anchor link resolves to a real heading; and normative claims match the Go code, not intuition.

Present the diff summary to the user and flag any judgment calls (e.g. a rule whose history is now dropped by the "current protocol only" convention) rather than deciding silently.

Notes

  • Per go-algorand/CLAUDE.md: "new consensus parameters, or changes to existing parameters will require an update to the specification." This skill is that update.
  • New REST endpoints/transaction fields may also need go-algorand-sdk changes — out of scope here, but worth mentioning to the user.
  • Do not commit or open PRs unless asked; leave the working tree for review.