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Overview

The Notifier interface is the primary interface between the orchestrator and the human. Humans walk away after spawning agents; notifications bring them back when their judgment is needed. Core principle: Push, not pull. The human never polls. Plugin Slot: notifier
Default Plugin: desktop

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Interface Definition

export interface Notifier {
  readonly name: string;
  
  notify(event: OrchestratorEvent): Promise<void>;
  notifyWithActions?(event: OrchestratorEvent, actions: NotifyAction[]): Promise<void>;
  post?(message: string, context?: NotifyContext): Promise<string | null>;
}

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Methods

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name
string
required
Plugin name identifier (e.g. "desktop", "slack", "webhook").
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notify
(event: OrchestratorEvent) => Promise<void>
required
Push a notification to the human.Parameters:
  • event - Orchestrator event with type, priority, session ID, message, data
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notifyWithActions
(event: OrchestratorEvent, actions: NotifyAction[]) => Promise<void>
Optional: Push a notification with actionable buttons/links.Parameters:
  • event - Orchestrator event
  • actions - Array of actions with labels and URLs/callbacks
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post
(message: string, context?: NotifyContext) => Promise<string | null>
Optional: Post a message to a channel (for team-visible notifiers like Slack).Parameters:
  • message - Message text
  • context - Optional context (session ID, project ID, PR URL, channel)
Returns: Message ID/URL if posted, null otherwise

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OrchestratorEvent

export interface OrchestratorEvent {
  id: string;
  type: EventType;
  priority: EventPriority;
  sessionId: SessionId;
  projectId: string;
  timestamp: Date;
  message: string;
  data: Record<string, unknown>;
}
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id
string
required
Unique event identifier
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type
EventType
required
Event type (e.g. "session.needs_input", "ci.failing", "merge.ready")
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priority
EventPriority
required
Priority level: "urgent", "action", "warning", or "info"
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sessionId
SessionId
required
Session that generated this event
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projectId
string
required
Project identifier
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timestamp
Date
required
When event occurred
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message
string
required
Human-readable message
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data
Record<string, unknown>
required
Event-specific data (PR URL, error details, etc.)

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EventType

export type EventType =
  // Session lifecycle
  | "session.spawned" | "session.working" | "session.exited"
  | "session.killed" | "session.stuck" | "session.needs_input"
  | "session.errored"
  // PR lifecycle
  | "pr.created" | "pr.updated" | "pr.merged" | "pr.closed"
  // CI
  | "ci.passing" | "ci.failing" | "ci.fix_sent" | "ci.fix_failed"
  // Reviews
  | "review.pending" | "review.approved" | "review.changes_requested"
  | "review.comments_sent" | "review.comments_unresolved"
  // Automated reviews
  | "automated_review.found" | "automated_review.fix_sent"
  // Merge
  | "merge.ready" | "merge.conflicts" | "merge.completed"
  // Reactions
  | "reaction.triggered" | "reaction.escalated"
  // Summary
  | "summary.all_complete";

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EventPriority

export type EventPriority = "urgent" | "action" | "warning" | "info";
  • urgent - Immediate attention required (session stuck, CI failing repeatedly)
  • action - Human decision needed (merge ready, changes requested)
  • warning - Something to be aware of (session exited, CI fix sent)
  • info - FYI only (session spawned, PR created)

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NotifyAction

export interface NotifyAction {
  label: string;
  url?: string;
  callbackEndpoint?: string;
}
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label
string
required
Button/link label (e.g. "View PR", "Approve", "Kill Session")
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url
string
URL to open (for simple links)
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callbackEndpoint
string
API endpoint to call when action is clicked (for interactive buttons)

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NotifyContext

export interface NotifyContext {
  sessionId?: SessionId;
  projectId?: string;
  prUrl?: string;
  channel?: string;
}
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sessionId
SessionId
Session ID for context
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projectId
string
Project ID for context
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prUrl
string
PR URL to include in message
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channel
string
Channel/thread to post to (Slack, Discord)

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Usage Examples

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Implementing a Notifier Plugin

import type { Notifier, OrchestratorEvent, NotifyAction } from "@composio/ao-core";
import { execFile } from "node:child_process";
import { promisify } from "node:util";

const execFileAsync = promisify(execFile);

export function create(): Notifier {
  return {
    name: "desktop",
    
    async notify(event: OrchestratorEvent): Promise<void> {
      const title = `[${event.priority.toUpperCase()}] ${event.type}`;
      const body = `${event.message}\n\nSession: ${event.sessionId}`;
      
      // macOS notification
      await execFileAsync("osascript", [
        "-e",
        `display notification "${body}" with title "${title}"`
      ], { timeout: 5_000 });
    },
    
    async notifyWithActions(event: OrchestratorEvent, actions: NotifyAction[]): Promise<void> {
      // For desktop, open URLs in browser
      await this.notify(event);
      
      if (actions.length > 0 && actions[0].url) {
        await execFileAsync("open", [actions[0].url], { timeout: 5_000 });
      }
    }
  };
}

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Slack Notifier Example

import type { Notifier, OrchestratorEvent, NotifyAction, NotifyContext } from "@composio/ao-core";

export function create(config: { webhookUrl: string; channel?: string }): Notifier {
  return {
    name: "slack",
    
    async notify(event: OrchestratorEvent): Promise<void> {
      const color = {
        urgent: "danger",
        action: "warning",
        warning: "warning",
        info: "good"
      }[event.priority];
      
      await fetch(config.webhookUrl, {
        method: "POST",
        headers: { "Content-Type": "application/json" },
        body: JSON.stringify({
          channel: config.channel,
          attachments: [{
            color,
            title: event.type,
            text: event.message,
            fields: [
              { title: "Session", value: event.sessionId, short: true },
              { title: "Project", value: event.projectId, short: true }
            ],
            footer: "Agent Orchestrator",
            ts: Math.floor(event.timestamp.getTime() / 1000)
          }]
        })
      });
    },
    
    async notifyWithActions(event: OrchestratorEvent, actions: NotifyAction[]): Promise<void> {
      await fetch(config.webhookUrl, {
        method: "POST",
        headers: { "Content-Type": "application/json" },
        body: JSON.stringify({
          channel: config.channel,
          text: event.message,
          attachments: [{
            callback_id: event.id,
            actions: actions.map(a => ({
              type: "button",
              text: a.label,
              url: a.url,
              value: a.callbackEndpoint
            }))
          }]
        })
      });
    },
    
    async post(message: string, context?: NotifyContext): Promise<string | null> {
      const response = await fetch(config.webhookUrl, {
        method: "POST",
        headers: { "Content-Type": "application/json" },
        body: JSON.stringify({
          channel: context?.channel || config.channel,
          text: message,
          context: context ? {
            session: context.sessionId,
            project: context.projectId,
            pr: context.prUrl
          } : undefined
        })
      });
      
      return response.ok ? "posted" : null;
    }
  };
}

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Using Notifiers in Lifecycle Manager

import type { Notifier, OrchestratorEvent } from "@composio/ao-core";

// Get notifiers for this priority level
const priority = "urgent";
const notifierNames = config.notificationRouting[priority]; // ["desktop", "slack"]
const notifiers = notifierNames.map(name => registry.get("notifier", name));

// Create event
const event: OrchestratorEvent = {
  id: crypto.randomUUID(),
  type: "session.needs_input",
  priority: "urgent",
  sessionId: session.id,
  projectId: session.projectId,
  timestamp: new Date(),
  message: `Session ${session.id} is waiting for your input`,
  data: {
    workspacePath: session.workspacePath,
    branch: session.branch
  }
};

// Notify all configured notifiers
await Promise.all(notifiers.map(n => n.notify(event)));

// Or with actions
const actions = [
  { label: "Open Session", url: `http://localhost:3000/sessions/${session.id}` },
  { label: "Kill", callbackEndpoint: `/api/sessions/${session.id}/kill` }
];

for (const notifier of notifiers) {
  if (notifier.notifyWithActions) {
    await notifier.notifyWithActions(event, actions);
  } else {
    await notifier.notify(event);
  }
}

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Implementation Notes

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Notification Routing

Notifications are routed by priority in agent-orchestrator.yaml: 
notificationRouting:
  urgent: [desktop, slack]      # Immediate attention
  action: [desktop]             # Human decision needed
  warning: [slack]              # FYI for team
  info: []                      # No notifications

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Rate Limiting

Notifiers should implement rate limiting to avoid spam:
  • Group similar events (multiple CI failures)
  • Debounce rapid events (agent activity)
  • Respect platform limits (Slack API rate limits)

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Error Handling

Notifiers should fail gracefully:
  • Log errors but don’t throw (notification failure shouldn’t crash orchestrator)
  • Retry with backoff for transient failures
  • Fall back to simpler notifiers (desktop if Slack fails)

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Built-in Plugins

  • desktop - macOS/Linux desktop notifications (default)
  • slack - Slack webhook/API integration
  • composio - Composio notification API
  • webhook - Generic webhook POST
Future plugins could support Discord, Email, SMS, PagerDuty, etc.

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See Also

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