4 files changed, 204 insertions, 0 deletions
diff --git a/packages/core/src/effect/logger.ts b/packages/core/src/effect/logger.ts
new file mode 100644
index 000000000..69f9631e0
--- /dev/null
+++ b/packages/core/src/effect/logger.ts
@@ -0,0 +1,73 @@
+import { Cause, Effect, Logger, References } from "effect"
+import * as Log from "../util/log"
+
+type Fields = Record<string, unknown>
+
+const normalizeKey = (key: string) => (key === "sessionID" ? "session.id" : key)
+
+export interface Handle {
+  readonly debug: (msg?: unknown, extra?: Fields) => Effect.Effect<void>
+  readonly info: (msg?: unknown, extra?: Fields) => Effect.Effect<void>
+  readonly warn: (msg?: unknown, extra?: Fields) => Effect.Effect<void>
+  readonly error: (msg?: unknown, extra?: Fields) => Effect.Effect<void>
+  readonly with: (extra: Fields) => Handle
+}
+
+const clean = (input?: Fields): Fields =>
+  Object.fromEntries(
+    Object.entries(input ?? {})
+      .filter((entry) => entry[1] !== undefined && entry[1] !== null)
+      .map(([key, value]) => [normalizeKey(key), value]),
+  )
+
+const text = (input: unknown): string => {
+  // oxlint-disable-next-line no-base-to-string
+  if (Array.isArray(input)) return input.map((item) => String(item)).join(" ")
+  // oxlint-disable-next-line no-base-to-string
+  return input === undefined ? "" : String(input)
+}
+
+const call = (run: (msg?: unknown) => Effect.Effect<void>, base: Fields, msg?: unknown, extra?: Fields) => {
+  const ann = clean({ ...base, ...extra })
+  const fx = run(msg)
+  return Object.keys(ann).length ? Effect.annotateLogs(fx, ann) : fx
+}
+
+export const logger = Logger.make((opts) => {
+  const extra = clean(opts.fiber.getRef(References.CurrentLogAnnotations))
+  const now = opts.date.getTime()
+  for (const [key, start] of opts.fiber.getRef(References.CurrentLogSpans)) {
+    extra[`logSpan.${key}`] = `${now - start}ms`
+  }
+  if (opts.cause.reasons.length > 0) {
+    extra.cause = Cause.pretty(opts.cause)
+  }
+
+  const svc = typeof extra.service === "string" ? extra.service : undefined
+  if (svc) delete extra.service
+  const log = svc ? Log.create({ service: svc }) : Log.Default
+  const msg = text(opts.message)
+
+  switch (opts.logLevel) {
+    case "Trace":
+    case "Debug":
+      return log.debug(msg, extra)
+    case "Warn":
+      return log.warn(msg, extra)
+    case "Error":
+    case "Fatal":
+      return log.error(msg, extra)
+    default:
+      return log.info(msg, extra)
+  }
+})
+
+export const layer = Logger.layer([logger], { mergeWithExisting: false })
+
+export const create = (base: Fields = {}): Handle => ({
+  debug: (msg, extra) => call((item) => Effect.logDebug(item), base, msg, extra),
+  info: (msg, extra) => call((item) => Effect.logInfo(item), base, msg, extra),
+  warn: (msg, extra) => call((item) => Effect.logWarning(item), base, msg, extra),
+  error: (msg, extra) => call((item) => Effect.logError(item), base, msg, extra),
+  with: (extra) => create({ ...base, ...extra }),
+})
diff --git a/packages/core/src/effect/memo-map.ts b/packages/core/src/effect/memo-map.ts
new file mode 100644
index 000000000..c797dbf42
--- /dev/null
+++ b/packages/core/src/effect/memo-map.ts
@@ -0,0 +1,3 @@
+import { Layer } from "effect"
+
+export const memoMap = Layer.makeMemoMapUnsafe()
diff --git a/packages/core/src/effect/observability.ts b/packages/core/src/effect/observability.ts
new file mode 100644
index 000000000..0203079ab
--- /dev/null
+++ b/packages/core/src/effect/observability.ts
@@ -0,0 +1,107 @@
+import { Effect, Layer, Logger } from "effect"
+import { FetchHttpClient } from "effect/unstable/http"
+import { OtlpLogger, OtlpSerialization } from "effect/unstable/observability"
+import * as EffectLogger from "./logger"
+import { Flag } from "../flag/flag"
+import { InstallationChannel, InstallationVersion } from "../installation/version"
+import { ensureProcessMetadata } from "../util/opencode-process"
+
+const base = Flag.OTEL_EXPORTER_OTLP_ENDPOINT
+export const enabled = !!base
+const processID = crypto.randomUUID()
+
+const headers = Flag.OTEL_EXPORTER_OTLP_HEADERS
+  ? Flag.OTEL_EXPORTER_OTLP_HEADERS.split(",").reduce(
+      (acc, x) => {
+        const [key, ...value] = x.split("=")
+        acc[key] = value.join("=")
+        return acc
+      },
+      {} as Record<string, string>,
+    )
+  : undefined
+
+export function resource(): { serviceName: string; serviceVersion: string; attributes: Record<string, string> } {
+  const processMetadata = ensureProcessMetadata("main")
+  const attributes: Record<string, string> = (() => {
+    const value = process.env.OTEL_RESOURCE_ATTRIBUTES
+    if (!value) return {}
+    try {
+      return Object.fromEntries(
+        value.split(",").map((entry) => {
+          const index = entry.indexOf("=")
+          if (index < 1) throw new Error("Invalid OTEL_RESOURCE_ATTRIBUTES entry")
+          return [decodeURIComponent(entry.slice(0, index)), decodeURIComponent(entry.slice(index + 1))]
+        }),
+      )
+    } catch {
+      return {}
+    }
+  })()
+
+  return {
+    serviceName: "opencode",
+    serviceVersion: InstallationVersion,
+    attributes: {
+      ...attributes,
+      "deployment.environment.name": InstallationChannel,
+      "opencode.client": Flag.OPENCODE_CLIENT,
+      "opencode.process_role": processMetadata.processRole,
+      "opencode.run_id": processMetadata.runID,
+      "service.instance.id": processID,
+    },
+  }
+}
+
+function logs() {
+  return Logger.layer(
+    [
+      EffectLogger.logger,
+      OtlpLogger.make({
+        url: `${base}/v1/logs`,
+        resource: resource(),
+        headers,
+      }),
+    ],
+    { mergeWithExisting: false },
+  ).pipe(Layer.provide(OtlpSerialization.layerJson), Layer.provide(FetchHttpClient.layer))
+}
+
+const traces = async () => {
+  const NodeSdk = await import("@effect/opentelemetry/NodeSdk")
+  const OTLP = await import("@opentelemetry/exporter-trace-otlp-http")
+  const SdkBase = await import("@opentelemetry/sdk-trace-base")
+
+  // @effect/opentelemetry creates a NodeTracerProvider but never calls
+  // register(), so the global @opentelemetry/api context manager stays
+  // as the no-op default. Non-Effect code (like the AI SDK) that calls
+  // tracer.startActiveSpan() relies on context.active() to find the
+  // parent span - without a real context manager every span starts a
+  // new trace. Registering AsyncLocalStorageContextManager fixes this.
+  const { AsyncLocalStorageContextManager } = await import("@opentelemetry/context-async-hooks")
+  const { context } = await import("@opentelemetry/api")
+  const mgr = new AsyncLocalStorageContextManager()
+  mgr.enable()
+  context.setGlobalContextManager(mgr)
+
+  return NodeSdk.layer(() => ({
+    resource: resource(),
+    spanProcessor: new SdkBase.BatchSpanProcessor(
+      new OTLP.OTLPTraceExporter({
+        url: `${base}/v1/traces`,
+        headers,
+      }),
+    ),
+  }))
+}
+
+export const layer = !base
+  ? EffectLogger.layer
+  : Layer.unwrap(
+      Effect.gen(function* () {
+        const trace = yield* Effect.promise(traces)
+        return Layer.mergeAll(trace, logs())
+      }),
+    )
+
+export const Observability = { enabled, layer }
diff --git a/packages/core/src/effect/runtime.ts b/packages/core/src/effect/runtime.ts
new file mode 100644
index 000000000..e4f682709
--- /dev/null
+++ b/packages/core/src/effect/runtime.ts
@@ -0,0 +1,21 @@
+import { Layer, type Context, ManagedRuntime, type Effect } from "effect"
+import { memoMap } from "./memo-map"
+import { Observability } from "./observability"
+
+export function makeRuntime<I, S, E>(service: Context.Service<I, S>, layer: Layer.Layer<I, E>) {
+  let rt: ManagedRuntime.ManagedRuntime<I, E> | undefined
+  const getRuntime = () =>
+    (rt ??= ManagedRuntime.make(Layer.provideMerge(layer, Observability.layer) as Layer.Layer<I, E>, {
+      memoMap,
+    }))
+
+  return {
+    runSync: <A, Err>(fn: (svc: S) => Effect.Effect<A, Err, I>) => getRuntime().runSync(service.use(fn)),
+    runPromiseExit: <A, Err>(fn: (svc: S) => Effect.Effect<A, Err, I>, options?: Effect.RunOptions) =>
+      getRuntime().runPromiseExit(service.use(fn), options),
+    runPromise: <A, Err>(fn: (svc: S) => Effect.Effect<A, Err, I>, options?: Effect.RunOptions) =>
+      getRuntime().runPromise(service.use(fn), options),
+    runFork: <A, Err>(fn: (svc: S) => Effect.Effect<A, Err, I>) => getRuntime().runFork(service.use(fn)),
+    runCallback: <A, Err>(fn: (svc: S) => Effect.Effect<A, Err, I>) => getRuntime().runCallback(service.use(fn)),
+  }
+}