Structs Streaming (GRASS)

GRASS (Game Real-time Application Streaming Service) delivers real-time game events over NATS. Instead of polling queries repeatedly, subscribe to GRASS and react to events the moment they happen.

When to Use GRASS

Rule of thumb: If you need to react to something, use GRASS. If you need to read something, use a query.

Finding Your GRASS Endpoint

The GRASS WebSocket URL is not hardcoded — it comes from the guild configuration.

1. Query the guild list: curl http://reactor.oh.energy:1317/structs/guild
2. Follow the guild's endpoint URL to get its config
3. Look for services.grass_nats_websocket

Example (Orbital Hydro guild):

{
  "services": {
    "grass_nats_websocket": "ws://crew.oh.energy:1443",
    "guild_api": "http://crew.oh.energy/api/",
    "reactor_api": "http://reactor.oh.energy:1317/"
  }
}

The grass_nats_websocket value is your NATS WebSocket endpoint. Not all guilds provide this service — check before relying on it.

A reliable reference endpoint: ws://crew.oh.energy:1443 (Orbital Hydro / Slow Ninja).

Discovery First

Before subscribing to specific subjects, subscribe to the > wildcard to see all traffic flowing through the GRASS server. This reveals the actual subject patterns in use, which may differ from documentation.

const sub = nc.subscribe(">");
for await (const msg of sub) {
  console.log(`[${msg.subject}]`, new TextDecoder().decode(msg.data));
}

Watch the output for 30-60 seconds. You will see subjects like structs.planet.2-1, consensus, healthcheck, etc. Once you know what subjects carry the events you need, narrow your subscriptions to those specific subjects.

Important: Struct events (attacks, builds, status changes) often arrive on the planet subject rather than the struct subject. If you are not receiving expected struct events, subscribe to the struct's planet subject instead.

Subject Patterns

Subscribe to subjects matching the entities you care about:

Use wildcards (*) to discover what events exist. Narrow to specific subjects once you know what you need. Use > to see everything (see "Discovery First" above).

Event Types

Planet Events

Struct Events

Note: Struct events frequently arrive on the planet subject (structs.planet.{id}) rather than the struct subject. Subscribe to both if you need complete coverage.

Player Events

Guild Events

Inventory Events

Subject: structs.inventory.{denom}.{guild_id}.{player_id}.{address}

Track token movements — Alpha Matter, guild tokens, ore, etc.

Grid Events

Subject: structs.grid.{object_id}

Track attribute changes on any game object (players, structs, planets).

Combat Event Payloads

struct_attack events include detailed shot-by-shot resolution. Example payload (observed on planet subject):

{
  "category": "struct_attack",
  "attackingStructId": "5-100",
  "targetStructId": "5-200",
  "weaponSystem": "primary",
  "eventAttackShotDetail": [
    {
      "shotIndex": 0,
      "damage": 2,
      "evaded": false,
      "blocked": false,
      "blockerStructId": "",
      "counterAttackDamage": 1,
      "counterAttackerStructId": "5-200"
    }
  ],
  "attackerHealthRemaining": 2,
  "targetHealthRemaining": 1,
  "targetDestroyed": false,
  "attackerDestroyed": false
}

Key fields in eventAttackShotDetail:

• evaded -- true if the shot missed (defense type interaction)
• blocked -- true if a defender intercepted
• blockerStructId -- which struct blocked (if any)
• counterAttackDamage / counterAttackerStructId -- counter-attack info per shot

struct_health events track HP changes:

{
  "category": "struct_health",
  "structId": "5-200",
  "health": 1,
  "maxHealth": 3,
  "destroyed": false
}

Noise Filtering

The consensus and healthcheck subjects fire constantly (every few seconds). When using the > wildcard for discovery, filter these out to see actual game events:

const sub = nc.subscribe(">");
for await (const msg of sub) {
  if (msg.subject === "consensus" || msg.subject === "healthcheck") continue;
  console.log(`[${msg.subject}]`, new TextDecoder().decode(msg.data));
}

Global Events

Building Event Listener Tools

Agents should build custom tools that connect to GRASS when they need event-driven behavior. Here are patterns to follow.

Minimal Node.js Listener

Install the NATS WebSocket client:

npm install nats.ws

import { connect } from "nats.ws";

const nc = await connect({ servers: "ws://crew.oh.energy:1443" });

const sub = nc.subscribe("structs.planet.2-1");
for await (const msg of sub) {
  const event = JSON.parse(new TextDecoder().decode(msg.data));
  console.log(JSON.stringify(event));
}

Minimal Python Listener

Install the NATS client:

pip install nats-py

import asyncio, json, nats

async def main():
    nc = await nats.connect("ws://crew.oh.energy:1443")
    sub = await nc.subscribe("structs.planet.2-1")
    async for msg in sub.messages:
        event = json.loads(msg.data.decode())
        print(json.dumps(event))

asyncio.run(main())

Raid Alert Tool (example pattern)

A tool that watches for raids on your planet and outputs an alert:

import { connect } from "nats.ws";

const PLANET_ID = process.argv[2]; // e.g. "2-1"
const nc = await connect({ servers: "ws://crew.oh.energy:1443" });
const sub = nc.subscribe(`structs.planet.${PLANET_ID}`);

for await (const msg of sub) {
  const event = JSON.parse(new TextDecoder().decode(msg.data));
  if (event.category === "raid_status") {
    console.log(JSON.stringify({ alert: "RAID", planet: PLANET_ID, data: event }));
  }
  if (event.category === "fleet_arrive") {
    console.log(JSON.stringify({ alert: "FLEET_ARRIVAL", planet: PLANET_ID, data: event }));
  }
}

Player Creation Watcher (example pattern)

Instead of polling structsd query structs address after guild signup, watch for the address registration event:

import { connect } from "nats.ws";

const nc = await connect({ servers: "ws://crew.oh.energy:1443" });
const sub = nc.subscribe("structs.address.register.*");

for await (const msg of sub) {
  const event = JSON.parse(new TextDecoder().decode(msg.data));
  console.log(JSON.stringify(event));
  break; // exit after first match
}
await nc.close();

When to Build a Custom Tool

Build a GRASS listener tool when:

• You need to wait for an event — guild signup completion, fleet arrival, raid detection
• You need continuous monitoring — threat detection during vulnerable ore window, combat tracking
• You want an event-driven game loop — react to block events instead of polling on a timer
• You're managing multiple players — one GRASS connection can monitor all your entities simultaneously

Store custom tools in your workspace (e.g., scripts/ or alongside the relevant skill).

Connection Best Practices

• Use specific subjects once you know what you need. Wildcards are for discovery.
• Limit to 10-20 subscriptions per connection to avoid overwhelming the client.
• Implement reconnection with exponential backoff — NATS connections can drop.
• Parse JSON defensively — not all messages may match expected schema.
• Close connections when done. Don't leave idle GRASS connections open.

Procedure

Quick Setup

1. Get the GRASS endpoint from your guild config (or use ws://crew.oh.energy:1443)
2. Record the endpoint in TOOLS.md under Servers
3. Choose your language (Node.js or Python)
4. Install the NATS client library (nats.ws for Node, nats-py for Python)
5. Write a listener script for your specific use case
6. Run it in a background terminal

For Ongoing Monitoring

1. Subscribe to your planet(s): structs.planet.{id} — raid alerts, fleet arrivals
2. Subscribe to your structs: structs.struct.{id} — attack/status alerts
3. Subscribe to global: structs.global — block tick for game loop timing
4. Log events to memory/ for cross-session awareness

Automation Patterns (Defence Contractor)

The Structs permission system and GRASS event stream were designed for AI agents to automate game responses. The design docs call this the "Defence Contractor" pattern — an agent that monitors events and acts on behalf of players within scoped permissions.

Common Automation Triggers

Permission Scoping for Automated Agents

When delegating actions to an automation agent (separate key or service):

1. Grant minimal permissions: Use permission-grant-on-object to allow specific actions on specific structs, not blanket access.
2. Separate keys: The automation agent should use its own signing key, registered as a secondary address on the player via address-register.
3. Scope by struct: Grant mine/refine permissions on extractors and refineries only. Grant defense permissions on fleet structs only.
4. Revoke when not needed: Use permission-revoke-on-object to remove automation access during sensitive operations.

Example: Refine-on-Mine-Complete Loop

Subscribe to: structs.struct.{extractor-id}
On event: struct_ore_mine_complete
  → Run: structsd tx structs struct-ore-refine-compute -D 1 --from [key] --gas auto -y -- [refinery-id]

Subscribe to: structs.struct.{refinery-id}
On event: struct_ore_refine_complete
  → Run: structsd tx structs struct-ore-mine-compute -D 1 --from [key] --gas auto -y -- [extractor-id]

This creates a continuous mine-refine loop that runs unattended. Ore is never left unrefined.

Example: Defend-on-Raid-Detected

Subscribe to: structs.planet.{planet-id}
On event: planet_raid_start
  → Activate stealth on vulnerable structs
  → Set defenders on high-value structs
  → Log raid to memory/intel/threats.md
  → Alert commander if available

Safe Boundaries

• Never auto-spend Alpha without commander approval (infusion, guild-bank operations)
• Never auto-move fleets away from defended planets without threat assessment
• Always log actions to memory/ for cross-session audit trail
• Rate-limit reactions — one transaction per ~6 seconds per key (sequence number constraint)

See Also

• protocols/streaming — Full GRASS/NATS protocol specification
• api/streaming/event-types — Complete event type catalog
• api/streaming/event-schemas — JSON schema definitions for event payloads
• api/streaming/subscription-patterns — Subscription patterns and examples
• awareness/async-operations — Background operations and pipeline strategy
• awareness/threat-detection — Using GRASS for early warning