llm_meter 0.1.0

Per-request token cost + latency + cache observability HUD for any Flutter LLM app. Drop-in wrapper, live HUD in dev, silent telemetry sink in prod.

Changelog

0.1.0 — 2026-06-02

First public release. Per-request cost + latency + cache observability for any Flutter LLM app.

Added

• Core
  • MeterEvent — immutable record of one LLM call (provider, model, tokens, cost, latency, cache hits, conversation/request ids, error, metadata).
  • LlmMeter singleton with init(config), record(event), stats(), events(), stream, and clear().
  • MeterConfig — sinks, pricing overrides, display currency, GDPR mode, ring-buffer capacity.
• Pricing engine
  • ModelPricing.perMillion(...) factory.
  • Built-in pricing table for 31 hosted models (OpenAI GPT-5/4.1/4o/o3/o4, Anthropic Claude 4.7/4.6/4.5/3.7/3.5, Google Gemini 2.5/2.0, Meta Llama 3.3/3.1, Mistral, xAI Grok, DeepSeek, Cohere). Snapshot dated 2026-05-31.
  • pricingFor(model) / priceForModel(...) pure functions with case-, separator-, and provider-prefix-tolerant lookup.
  • Cache-discount math (Anthropic cache reads, Gemini context cache).
  • User overrides via MeterConfig.pricingOverrides.
• Currency
  • Currency with perMillion conversion + prefix/suffix formatting; bundled USD, EUR, GBP, INR, SEK, CHF. No package:intl dependency.
• Aggregation
  • RingBuffer<T> — fixed-capacity O(1) push, oldest dropped.
  • MeterStats — total $, p50/p99 latency, cache-hit %, per-model breakdown.
• Provider wrappers
  • MeteredCall.run<T>(...) — wraps any Future, extracts usage, records latency. Records zero-cost error events and rethrows on failure.
  • MeteredStream.wrap<C>(...) — streaming passthrough that records once on done. Handles per-chunk usage deltas, errors, and mid-stream cancellation.
  • Provider usage recipes (openAiUsage, anthropicUsage, geminiUsage) that accept JSON maps — no provider SDK dependency.
• HUD
  • LlmMeterHud floating draggable card; snaps to nearest corner on release.
  • Live total cost, last call cost+ms, p50/p99, cache %, event count.
  • Tap-to-expand event log (configurable maxEventsInLog).
  • AnimatedSize transition; auto-hides in release unless forceShow: true.
• Sinks
  • MeterSink abstract interface.
  • ConsoleSink (debug default).
  • PosthogSink and MixpanelSink via dart:io HttpClient (no SDK dep; web fallback is a no-op).
  • BatchingSink (by count or time interval).
  • RetryingSink (exponential backoff with bounded offline queue).
  • gdprScrub() helper that drops conversation_id, request_id, and user_* / email / ip metadata.

Quality

• 124 unit and widget tests passing.
• flutter analyze with strict casts/inference/raw-types: zero issues.
• Pure-Dart core; no transitive runtime dependencies.
• API keys are never read or stored by the package — caller-supplied only.