Evalbench

Documentation from tfohlmeister/convex-evalbench, recorded October 23, 2026. APIs and setup may differ in the Bijection adaptation.

convex-evalbench

Reactive LLM eval, tracing, and regression layer as a Convex Component.

Capture spans from your agents, run datasets against them, score with built-in scorers and LLM-as-judge, and watch results stream into a reactive dashboard live, all inside your own Convex deployment. No extra infrastructure, no polling: Convex subscriptions push every new span to your UI as it lands.

Status: tracing (with the @convex-dev/agent and Vercel AI SDK adapters plus an OTLP/JSON receiver), versioned datasets, the eval runner, deterministic scorers, LLM-as-judge with multi-judge consensus, embeddingSimilarity, custom scorers, run comparison with a CI regression gate, host-invoked trace retention, and a live reactive dashboard are shipped. See the roadmap. References: docs/tracing.md, docs/evals.md, docs/dashboard.md.

Tracing

Record every LLM call as a span inside your own Convex deployment. Because Convex is reactive, a trace renders as a live span tree that fills in while it is in flight, no polling.

Install and register

Copy codenpm install convex-evalbench

Copy code// convex/convex.config.ts
import { defineApp } from "convex/server";
import evalbench from "convex-evalbench/convex.config";

const app = defineApp();
app.use(evalbench);
export default app;

Record spans (source-agnostic API)

Construct an Evalbench from the generated component handle and record spans. Recording is best-effort: a failure is logged and swallowed, never thrown back into your LLM call.

Copy codeimport { Evalbench } from "convex-evalbench";
import { components } from "./_generated/api.js";
import { action } from "./_generated/server.js";

const evalbench = new Evalbench(components.evalbench);

export const runStep = action({
  args: {},
  handler: async (ctx) => {
    const traceId = crypto.randomUUID();
    const rootSpanId = crypto.randomUUID();
    await evalbench.recordSpan(ctx, {
      traceId,
      spanId: rootSpanId,
      kind: "agent_step",
      operationName: "my operation",
      status: "success",
      startedAt: Date.now(),
    });
    await evalbench.recordSpan(ctx, {
      traceId,
      spanId: crypto.randomUUID(),
      parentSpanId: rootSpanId,
      kind: "llm",
      operationName: "llm call",
      model: "...",
      provider: "...",
      inputTokens: 10,
      outputTokens: 20,
      totalTokens: 30,
      status: "success",
      startedAt: Date.now(),
      // input/output are recorded only when you pass them (opt-in).
      input: "the prompt",
      output: "the completion",
    });
  },
});

Read it back (reactive)

Expose the queries from your host so a client can subscribe; the span tree fills in live as spans are recorded.

Copy codeimport { query } from "./_generated/server.js";
import { v } from "convex/values";

export const listSpans = query({
  args: { traceId: v.string() },
  handler: (ctx, args) => evalbench.spansByTrace(ctx, args.traceId),
});

export const listRecentTraces = query({
  args: { limit: v.optional(v.number()) },
  handler: (ctx, args) => evalbench.recentTraces(ctx, args),
});

// Resolve a span's content on demand (inline strings plus signed URLs for
// content held in File Storage). `spanId` is the document id from listSpans.
export const getSpanContent = query({
  args: { spanId: v.string() },
  handler: (ctx, args) => evalbench.spanContent(ctx, args.spanId),
});

The tree and recent-traces queries return metadata only (no raw content), so reactive updates stay small. Raw content is opt-in (you record it by passing input/output); content at or below 4 KB is stored inline, larger content is offloaded to Convex File Storage and resolved on demand.

Wrap a @convex-dev/agent agent (optional)

The withEvalbench adapter is one optional ingestion source. It wraps a @convex-dev/agent agent so each LLM call is recorded as a span, composing with (not replacing) any handlers you already set. @convex-dev/agent is an optional peer dependency; the tracing core does not import it.

Copy codeimport { Agent } from "@convex-dev/agent";
import { Evalbench } from "convex-evalbench";
import { withEvalbench } from "convex-evalbench/agent";
import { anthropic } from "@ai-sdk/anthropic";
import { components } from "./_generated/api.js";

const evalbench = new Evalbench(components.evalbench);

const agent = withEvalbench(
  new Agent(components.agent, {
    name: "my-agent",
    languageModel: anthropic("claude-haiku-4-5"),
  }),
  { evalbench, recordContent: true }, // recordContent defaults to false
);

LLM calls made inside one generateText / generateObject operation share a traceId and link to a root agent_step span, so the operation renders as one trace tree. See docs/tracing.md for details and limitations.

Other ingestion sources

Two more optional sources feed the same tracing core:

• Vercel AI SDK (convex-evalbench/ai): evalbenchMiddleware wraps a model with wrapLanguageModel, recording one span per call with measured latency. ai is an optional peer dependency.
• OpenTelemetry (convex-evalbench/otlp): otlpTraceHandler is an httpAction you mount (e.g. at /v1/traces) so any OTLP/JSON exporter streams spans in, mapped via GenAI semantic conventions.

See docs/tracing.md for both.

Evals: datasets, runs, scorers

Keep a versioned dataset of inputs with expected outputs, run your system under test against every item with bounded parallelism, and watch the pass rate fill in live.

Copy code// Seed a dataset.
const datasetId = await evalbench.createDataset(ctx, {
  name: "greetings",
  items: [
    { input: "hello", expectedOutput: "HELLO" },
    { input: "world", expectedOutput: "WORLD" },
  ],
});

// The system under test: an action taking { input, runId, itemId } and
// returning { output, traceId? }. Stamp your spans with runId so the
// run's traces correlate.
export const myTarget = action({
  args: { input: v.any(), runId: v.string(), itemId: v.string() },
  handler: async (ctx, args) => {
    const output = await runMyAgent(args.input);
    return { output };
  },
});

// Run it: one idempotent, scored result per item.
const runId = await evalbench.startRun(ctx, {
  datasetId,
  target: api.evals.myTarget,
  config: { scorers: [{ type: "exactMatch" }], concurrency: 4 },
});

Subscribe to evalbench.runSummary(ctx, runId) for the live counters (completed / passed / aggregate score, maintained in the same mutation that writes each result) and evalbench.listResults(ctx, runId) for the per-item rows with scores and trace links.

Scorers: deterministic built-ins exactMatch and jsonSchema (eval-free JSON Schema validation that runs in Convex's V8 runtime), plus host-extensible scoring with no provider SDK in the component: defineScorer for custom scorer actions, llmAsJudge for rubric-based judging with your own LLM call (each verdict traced as a judge span), multi-judge consensus with a quorum, and embeddingSimilarity against a host embedder action. A wedged run is recovered with evalbench.redriveRun(ctx, runId) (attempts-capped). See docs/evals.md for the target and scorer contracts, versioning, and the runner's execution model.

Local development

The repo bundles a pinned convex-local-backend, so the example app and tests run without a cloud Convex project. See CONTRIBUTING.md for the dev loop and release flow.

Roadmap

Tracing, datasets, the runner with managed retries (retryable target failures retried with exponential backoff; see docs/evals.md), judges (LLM-as-judge with consensus), embeddingSimilarity, custom scorers, regression / A-B (run comparison with a CI gate), trace retention (host-invoked pruneTraces), the Vercel AI SDK adapter (evalbenchMiddleware), the OTLP/JSON receiver (otlpTraceHandler for any OpenTelemetry-instrumented app; see docs/tracing.md), and the live dashboard (a companion React app over the reactive queries; see docs/dashboard.md) are shipped. The roadmap items are all delivered; feature requests are welcome via issues.

Security

Raw prompt/completion content is only stored when you opt in; span metadata is always recorded. See SECURITY.md for the threat model and how to report vulnerabilities.

License

Apache-2.0