fix(plugin): make a Laminar trace red iff the turn failed

Two defects made trace status uninformative for v4 runs.

A tool that throws is normal agent flow - the model reads the `tool-error`
result and adapts - but the AI SDK stamps ERROR on the `ai.toolCall` span and
Laminar reds a whole trace if any of its spans is ERROR. One buggy
`browser_execute` snippet therefore reported the entire run as a failure:
1,058 errored `browser_execute` spans in two days on prod. Demote those spans
to UNSET, keeping the message on `bcode.tool.error` and the `exception` event
intact.

Conversely nothing ever marked a genuinely failed turn. The AI SDK ends
`ai.streamText` / `ai.streamText.doStream` inside a transform `flush` that
never runs when the consumer aborts, so a provider error arriving mid-stream
drops those spans instead of marking them - the trace showed a clean, shorter
run. Mark the turn span ERROR on `session.error`, which `SessionProcessor.halt`
publishes just before the session goes idle. Aborts are excluded: stopping a
run is not a failure.

Author: Alezander9

packages/bcode-laminar/src/plugin.ts

@@ -12,6 +12,7 @@
 // module, not here.
 
 import type { Plugin } from "@opencode-ai/plugin"
+import { SpanStatusCode } from "@opentelemetry/api"
 import { NodeSDK } from "@opentelemetry/sdk-node"
 
 import { createSpanExporter } from "./exporter"
@@ -108,6 +109,27 @@ export const LaminarPlugin: Plugin = ({ client }) => {
     },
     event: async ({ event }) => {
       switch (event.type) {
+        case "session.error": {
+          // The turn span is the only place a failed run can be recorded.
+          // Nothing upstream does it: the AI SDK ends `ai.streamText` and
+          // `ai.streamText.doStream` inside a transform `flush` that never
+          // runs when the consumer aborts, so a provider error arriving
+          // mid-stream drops those spans entirely rather than marking them —
+          // the trace then showed a clean, shorter run. `session.error` is
+          // published just before the session goes idle (processor.ts `halt`),
+          // so the span is still open here; `session.idle` ends it below.
+          const sessionId = event.properties.sessionID
+          const span = sessionId ? sessionCurrentTurnSpan[sessionId] : undefined
+          const error = event.properties.error
+          // An abort is the user stopping the run, not a failure.
+          if (!span || !error || error.name === "MessageAbortedError") break
+          const detail = "message" in error.data ? error.data.message : ""
+          span.setStatus({
+            code: SpanStatusCode.ERROR,
+            message: detail ? `${error.name}: ${detail}` : error.name,
+          })
+          break
+        }
         case "session.idle": {
           const sessionId = event.properties.sessionID
           const span = sessionCurrentTurnSpan[sessionId]

packages/bcode-laminar/src/processor.ts

@@ -17,7 +17,7 @@
 //  - `pino` logger — opencode plugins log via `client.app.log`; the plugin passes
 //    in a logger callback.
 
-import { type Context, type Span, trace } from "@opentelemetry/api"
+import { type Context, type Span, SpanStatusCode, trace } from "@opentelemetry/api"
 import {
   BatchSpanProcessor,
   type ReadableSpan,
@@ -39,6 +39,7 @@ import { otelSpanIdToUUID, type StringUUID } from "./utils"
 
 const SDK_VERSION = "bcode-laminar-0.1"
 const SPAWNING_TOOL_NAMES = ["task"]
+const TOOL_ERROR = "bcode.tool.error"
 type LogFn = (level: "debug" | "info" | "warn" | "error", message: string) => void
 
 export class OpenCodeLaminarSpanProcessor implements SpanProcessor {
@@ -153,6 +154,21 @@ export class OpenCodeLaminarSpanProcessor implements SpanProcessor {
   }
 
   onEnd(span: ReadableSpan): void {
+    // A tool that throws is normal agent flow, not a failed run: the model
+    // reads the `tool-error` result and adapts. The AI SDK still stamps ERROR
+    // on the `ai.toolCall` span (`recordErrorOnSpan`), and Laminar reds a
+    // whole trace if ANY of its spans is ERROR — so every run where the model
+    // wrote one buggy `browser_execute` snippet was reported as a failure.
+    // Demote to UNSET, keeping the message as an attribute and the recorded
+    // `exception` event untouched. Only the `turn` span decides run outcome.
+    //
+    // Mutated in place because `setStatus`/`setAttribute` are no-ops once the
+    // span has ended, which it has by the time onEnd runs.
+    if (span.attributes["ai.toolCall.id"] && span.status.code === SpanStatusCode.ERROR) {
+      Object.assign(span.attributes, { [TOOL_ERROR]: span.status.message ?? "" })
+      Object.assign(span, { status: { code: SpanStatusCode.UNSET } })
+    }
+
     const spanId = span.spanContext().spanId
     this.spanIdLists.delete(spanId)
     this.spanIdToPath.delete(spanId)