add experimental.open_telemetry config option to enable OTEL spans

[noamzbr]

Related Issues

• Feature Request: Add Langfuse Tracing #219
• [Question] detailed per-interaction telemetry (token counts and input composition) for opencode-model communications #2666

What this does

• AI SDK has an experimental_telemetry flag. When enabled, it will automatically emit OTEL spans. I've added an optional config that turns that on in all calls to AI SDK generation functions.
• The user can then use any OTEL supporting framework for tracing. For example, in Langfuse it's pretty simple - the user can build a simple plugin to send the generated spans to Langfuse.

---

Happy to add / edit / expand if needed!

[r-costa-tornis]

👀

[r-costa-tornis]

Can you provide a little doc explaining how to enable langfuse for example?
In the config files I mean.

[noamzbr]

Sure, you should add "open_telemetry": true in your opencode.jsonc, and then add a relevant plugin. For Langfuse, the following plugin worked for me

/**
 * Langfuse OpenTelemetry Plugin for OpenCode
 * 
 * Requires: bun add @langfuse/otel @opentelemetry/sdk-node
 * Env vars: LANGFUSE_PUBLIC_KEY, LANGFUSE_SECRET_KEY, LANGFUSE_HOST
 */
import { NodeSDK } from "@opentelemetry/sdk-node"
import { LangfuseSpanProcessor } from "@langfuse/otel"

let initialized = false

export const LangfusePlugin = async () => ({
  async config(config) {
    if (!config.open_telemetry || initialized) return
    initialized = true

    const processor = new LangfuseSpanProcessor()
    new NodeSDK({ spanProcessors: [processor] }).start()

    // // Flush frequently - Required in headless mode to make sure flushes are made before process exit
    // setInterval(() => processor.forceFlush(), 500)
  },
})

[r-costa-tornis]

@rekram1-node 👀

[rekram1-node]

I'm a bit behind on prs at the moment but lemme take a look

[rekram1-node]

/oc rename open_telemetry to be under "experimental" object in the config, update all locations it's used

[opencode-agent]

Perfect! All changes are in place. Let me create a summary of what was changed:

Summary

I've successfully renamed open_telemetry to be under the experimental object in the config. Here are the changes made:

Changes Made:

1. Config Schema (packages/opencode/src/config/config.ts):

   • Removed open_telemetry from the root config object
   • Added openTelemetry to the experimental object (line 673-676)

2. Agent (packages/opencode/src/agent/agent.ts):

   • Updated line 233: cfg.open_telemetry → cfg.experimental?.openTelemetry

3. Session Compaction (packages/opencode/src/session/compaction.ts):

   • Updated line 196: cfg.open_telemetry → cfg.experimental?.openTelemetry

4. Session Prompt (packages/opencode/src/session/prompt.ts):

   • Updated line 618: cfg.open_telemetry → cfg.experimental?.openTelemetry
   • Updated line 1470: cfg.open_telemetry → cfg.experimental?.openTelemetry

5. Session Summary (packages/opencode/src/session/summary.ts):

   • Updated line 114: cfg.open_telemetry → cfg.experimental?.openTelemetry
   • Updated line 156: cfg.open_telemetry → cfg.experimental?.openTelemetry

New Config Format:

Users should now use the following format in their opencode.jsonc:

{
  "experimental": {
    "openTelemetry": true
  }
}

Instead of the previous format:

{
  "open_telemetry": true
}

opencode session  |  github run

[r-costa-tornis]

🎉 🎉 🎉 🎉
Ty so much @rekram1-node