feat: do not create a separate trace for sub-agent

Author: murtaza-u

src/index.ts

@@ -2,6 +2,13 @@ import type { Plugin } from "@opencode-ai/plugin"
 import { SeverityNumber } from "@opentelemetry/api-logs"
 import { logs } from "@opentelemetry/api-logs"
 import { trace } from "@opentelemetry/api"
+import {
+  AGENT_NAME,
+  INPUT_MIME_TYPE,
+  INPUT_VALUE,
+  LLM_INPUT_MESSAGES,
+  MimeType,
+} from "@arizeai/openinference-semantic-conventions"
 import pkg from "../package.json" with { type: "json" }
 import type {
   EventSessionCreated,
@@ -218,14 +225,23 @@ export const OtelPlugin: Plugin = async ({ project, client, directory, worktree
         .filter(Boolean)
         .join("\n")
       sessionInputs.set(input.sessionID, promptText)
-      handleRunStarted(
-        input.sessionID,
-        agent,
-        promptText,
-        input.model ? `${input.model.providerID}/${input.model.modelID}` : "unknown",
-        Date.now(),
-        ctx,
-      )
+      const model = input.model ? `${input.model.providerID}/${input.model.modelID}` : "unknown"
+      const sessionSpan = sessionSpans.get(input.sessionID)
+      if (sessionSpan) {
+        sessionSpan.setAttributes({
+          [AGENT_NAME]: agent,
+          ...(promptText
+            ? {
+                [INPUT_VALUE]: promptText,
+                [INPUT_MIME_TYPE]: MimeType.TEXT,
+                [LLM_INPUT_MESSAGES]: JSON.stringify([{ role: "user", content: promptText }]),
+              }
+            : {}),
+          model,
+        })
+      } else {
+        handleRunStarted(input.sessionID, agent, promptText, model, Date.now(), ctx)
+      }
       const promptLength = promptText.length
       logger.emit({
         severityNumber: SeverityNumber.INFO,
@@ -238,7 +254,7 @@ export const OtelPlugin: Plugin = async ({ project, client, directory, worktree
           "session.id": input.sessionID,
           agent,
           prompt_length: promptLength,
-          model: input.model ? `${input.model.providerID}/${input.model.modelID}` : "unknown",
+          model,
           ...commonAttrs,
         },
       })

tests/handlers/spans.test.ts

@@ -1,7 +1,6 @@
 import { describe, test, expect } from "bun:test"
 import { SpanStatusCode } from "@opentelemetry/api"
 import {
-  AGENT_NAME,
   LLM_MODEL_NAME,
   LLM_PROVIDER,
   LLM_SYSTEM,
@@ -12,7 +11,6 @@ import {
   LLM_TOKEN_COUNT_PROMPT_DETAILS_CACHE_WRITE,
   OpenInferenceSpanKind,
   SemanticConventions,
-  SESSION_ID,
   TOOL_NAME,
 } from "@arizeai/openinference-semantic-conventions"
 import type { Span } from "@opentelemetry/api"
@@ -27,7 +25,7 @@ import {
   handleMessagePartUpdated,
   startMessageSpan,
 } from "../../src/handlers/message.ts"
-import { makeCtx, makeTracer, type SpySpan } from "../helpers.ts"
+import { makeCtx, makeTracer } from "../helpers.ts"
 import type {
   EventSessionCreated,
   EventSessionIdle,
@@ -156,32 +154,6 @@ describe("session spans", () => {
     expect(ctx.sessionSpans.has("ses_1")).toBe(false)
   })
 
-  test("run span carries session.id attribute", () => {
-    const { ctx, tracer } = makeCtx()
-    handleRunStarted("ses_1", "agent", "prompt", "anthropic/claude", 1000, ctx)
-    expect(tracer.spans[0]!.attributes["session.id"]).toBe("ses_1")
-    expect(tracer.spans[0]!.attributes[SESSION_ID]).toBe("ses_1")
-  })
-
-  test("run span is tagged as an OpenInference agent span", () => {
-    const { ctx, tracer } = makeCtx()
-    handleRunStarted("ses_1", "agent", "prompt", "anthropic/claude", 1000, ctx)
-    expect(tracer.spans[0]!.attributes[OPENINFERENCE_SPAN_KIND]).toBe(OpenInferenceSpanKind.AGENT)
-    expect(tracer.spans[0]!.attributes[AGENT_NAME]).toBe("agent")
-  })
-
-  test("run span carries is_subagent=false for root session", () => {
-    const { ctx, tracer } = makeCtx()
-    handleRunStarted("ses_root", "agent", "prompt", "anthropic/claude", 1000, ctx)
-    expect(tracer.spans[0]!.attributes["session.is_subagent"]).toBe(false)
-  })
-
-  test("session span carries is_subagent=true for subagent session", () => {
-    const { ctx, tracer } = makeCtx()
-    handleSessionCreated(makeSessionCreated("ses_child", 1000, "ses_parent"), ctx)
-    expect(tracer.spans[0]!.attributes["session.is_subagent"]).toBe(true)
-  })
-
   test("ends session span with OK status on session.idle", () => {
     const { ctx, tracer } = makeCtx()
     handleSessionCreated(makeSessionCreated("ses_1"), ctx)