Participatory budget

A city asks 500 residents to choose among several complete plans for a $1M capital budget. Each plan says exactly how the money would be spent. Residents get nine credits each and may put them all behind one plan or spread them across plans they could support.

This is a decision GRP v0.1 can represent directly. The shipped quadratic_vote mechanism selects one option; it does not divide money among the options. That is why each option below is a complete budget plan rather than a single department or project.

Path: REST or MCP with one mandate per eligible resident.

Visibility: public for a public-records process.

Mechanism: quadratic_vote, with the v0.1 budget of nine credits per voter.

Quorum: 250 residents.

Window: 14 days.

1. Create the standing room

POST https://grp.app/api/rooms
X-Mandate: {city-clerk's-mandate}
Content-Type: application/json
 
{
  "about": "2026 participatory capital budget",
  "defer_first_decision": true,
  "config": {
    "type": "persistent",
    "visibility": "public",
    "mechanism": "quadratic_vote",
    "quorum": 250,
    "voting_window": 1209600,
    "max_participants": 501,
    "auth": "mandate_required",
    "decision_opening_authority": { "kind": "operator" },
    "creator_votes": false
  }
}

The response supplies a random slug; every later request uses that value. The clerk occupies the non-voting operator seat, so max_participants: 501 leaves room for 500 resident voters. Each resident joins by presenting a mandate issued through the city’s own eligibility process.

2. Open the budget decision

Once enrollment is ready, the clerk opens the question. Each option is a full plan that totals $1M.

POST https://grp.app/api/rooms/{slug}/ask
X-Mandate: {city-clerk's-mandate}
Content-Type: application/json
 
{
  "question": "Which complete capital plan should the city adopt for 2026?",
  "context": "Each option totals $1M. Allocate at most nine credits across the plans.",
  "options": [
    "Plan A — schools $400K; housing $300K; transit $200K; parks $100K",
    "Plan B — housing $400K; transit $300K; climate $200K; libraries $100K",
    "Plan C — roads $350K; public safety $250K; schools $250K; small business $150K",
    "Plan D — climate $350K; parks $250K; transit $250K; public art $150K"
  ]
}

3. Cast a quadratic ballot

A resident can express both preference and intensity. This ballot spends all nine available credits:

POST https://grp.app/api/rooms/{slug}/choose
X-Mandate: {resident's-mandate}
Content-Type: application/json
 
{
  "choice": {
    "Plan A — schools $400K; housing $300K; transit $200K; parks $100K": 5,
    "Plan B — housing $400K; transit $300K; climate $200K; libraries $100K": 3,
    "Plan D — climate $350K; parks $250K; transit $250K; public art $150K": 1
  },
  "rationale": "I prefer Plan A, but Plans B and D also address urgent needs."
}

The mechanism adds sqrt(credits) to each plan’s score for each voter. The transport accepts a structurally valid allocation even if it overspends; at resolution, the mechanism marks any ballot spending more than nine credits as invalid and excludes it from the tally. The signed receipt records the options, ballots allowed by the room’s visibility policy, tally, and outcome. The city executes the winning plan outside GRP.

What this example shows

• The ballot can carry intensity. A resident need not pretend that every acceptable plan is equally good.
• The option must match the mechanism. The shipped mechanism chooses a winner. It is not the separate, post-v0.1 budget_allocation mechanism.
• Eligibility stays outside the protocol. The city decides who is a resident and issues mandates; GRP enforces those credentials in the room.
• The room leaves a public record. The decision and its receipt remain readable under the host’s advertised retention policy.

Future extension: topical delegation

Liquid, topic-scoped delegation is not part of v0.1. A later profile could let a resident delegate a bounded set of credits to a trusted specialist, with the scope and cap signed into the delegation. Until that extension is specified and implemented, every resident casts their own ballot.