Output Dev Cost Hooks

// src/cost_hooks.ts
import { on } from '@outputai/core/hooks';
import type { HttpRequestCostEvent } from '@outputai/http';
import type { LLMGenerationMeteringEvent } from '@outputai/llm';

on<HttpRequestCostEvent>('cost:http:request', async event => {
  // handle HTTP cost
});

on<LLMGenerationMeteringEvent>('llm:generation:metering', async event => {
  // handle LLM cost
});

{
  "outputai": {
    "hookFiles": [
      "./dist/cost_hooks.js"
    ]
  }
}

// src/cost_hooks.ts
import { on } from '@outputai/core/hooks';
import { credentials } from '@outputai/core/credentials';
import type { HttpRequestCostEvent } from '@outputai/http';
import type { LLMGenerationMeteringEvent } from '@outputai/llm';

// Use plain fetch here, not createKyClient/outputFetch. Handlers run inside
// the emitting step's async context, so a traced client would add its own
// HTTP trace event to that step's trace on every forwarded cost event.
//
// Read the credential lazily with `get`, not `require`, at module scope: a
// hook file is imported at worker startup by an unguarded `await import()`
// (there's no try/catch around it), so a `require()` that throws here takes
// the whole worker down. `get`/`require` also only see workflow-scoped
// credentials from inside an activity — at startup, outside any activity,
// they resolve the global credential set only, so keep this in a global
// (not per-workflow) credential file.
const getWebhookUrl = (): string | undefined => credentials.get('observability.webhook_url') as string | undefined;

const postEvent = async (json: Record<string, unknown>): Promise<void> => {
  const webhookUrl = getWebhookUrl();
  if (!webhookUrl) {
    return;
  }

  const controller = new AbortController();
  const timeout = setTimeout(() => controller.abort(), 5000);
  try {
    await fetch(`${webhookUrl}/events`, {
      method: 'POST',
      headers: { 'content-type': 'application/json' },
      body: JSON.stringify(json),
      signal: controller.signal
    });
  } finally {
    clearTimeout(timeout);
  }
};

// Strip query strings — some APIs put API keys or tokens there.
const redactUrl = (url: string): string => {
  try {
    const parsed = new URL(url);
    return `${parsed.origin}${parsed.pathname}`;
  } catch {
    return '[unparseable-url]';
  }
};

on<HttpRequestCostEvent>('cost:http:request', async event => {
  if (!event.workflowDetails || !event.payload) {
    return;
  }

  // A caught failure here logs with this handler's own context; an
  // uncaught one is still caught and logged by the framework either way.
  try {
    await postEvent({
      eventId: event.eventId,
      eventDate: event.eventDate,
      workflowId: event.workflowDetails.workflowId,
      kind: 'http',
      url: redactUrl(event.payload.url),
      totalUsd: event.payload.total
    });
  } catch (error) {
    console.warn('cost_hooks: failed to forward HTTP cost event', error);
  }
});

on<LLMGenerationMeteringEvent>('llm:generation:metering', async event => {
  if (!event.workflowDetails || !event.payload) {
    return;
  }

  try {
    await postEvent({
      eventId: event.eventId,
      eventDate: event.eventDate,
      workflowId: event.workflowDetails.workflowId,
      kind: 'llm',
      providerId: event.payload.usage.providerId,
      modelId: event.payload.usage.modelId,
      totalUsd: event.payload.cost?.total ?? null
    });
  } catch (error) {
    console.warn('cost_hooks: failed to forward LLM cost event', error);
  }
});

// src/cost_hooks.ts
import { on } from '@outputai/core/hooks';
import { Logger } from '@outputai/core';
import type { HttpRequestCostEvent } from '@outputai/http';
import type { LLMGenerationMeteringEvent } from '@outputai/llm';

const log = Logger.createLogger('CostObservability');

const redactUrl = (url: string): string => {
  try {
    const parsed = new URL(url);
    return `${parsed.origin}${parsed.pathname}`;
  } catch {
    return '[unparseable-url]';
  }
};

on<HttpRequestCostEvent>('cost:http:request', async event => {
  if (!event.workflowDetails || !event.payload) {
    return;
  }

  log.info('http_request_cost', {
    eventId: event.eventId,
    workflowId: event.workflowDetails.workflowId,
    url: redactUrl(event.payload.url),
    totalUsd: event.payload.total
  });
});

on<LLMGenerationMeteringEvent>('llm:generation:metering', async event => {
  if (!event.workflowDetails || !event.payload) {
    return;
  }

  log.info('llm_generation_cost', {
    eventId: event.eventId,
    workflowId: event.workflowDetails.workflowId,
    providerId: event.payload.usage.providerId,
    modelId: event.payload.usage.modelId,
    totalUsd: event.payload.cost?.total ?? null
  });
});