> ## Documentation Index
> Fetch the complete documentation index at: https://docs.braintrust.dev/llms.txt
> Use this file to discover all available pages before exploring further.

# Topics facets empty due to Skipped status

> [!NOTE]
>
> **Applies to:**
>
> * Plan - Any
> * Deployment - Any
> *
> * Use case - Topics facets show empty results because all traces have Skipped status

## Summary

**Issue:** Topics facets appear empty and traces show a `Skipped` status instead of generating summaries.

**Cause:** `Skipped` means the default Thread preprocessor found no usable conversation text — this happens when traces do not store conversation content on LLM-type spans, which is what the default preprocessor reads.

**Resolution:** Create a custom preprocessor that extracts conversation from your actual trace shape, set it as the project default, and then re-generate topics.

## Resolution steps

### Step 1: Confirm the cause

Open a trace in **Logs** and select the **Thread** tab in the Trace Viewer. If the Thread view is empty, the preprocessor is not finding conversation content.

> [!NOTE]
>
> In the trace viewer, only the original thread view uses preprocessors and shows the preprocessor picker. The [new thread view](https://docs.braintrust.dev/observe/examine-traces.md#use-the-new-thread-view) is the default, so select  and choose **Go back to old thread view** first.

### Step 2: Create a custom preprocessor

1. In **Logs**, open any trace.
2. Select the **Thread** tab.
3. Click the config button.
4. In the **Preprocessor** dropdown, select **+ Custom preprocessor**.
5. Enter your preprocessor code. See the [Enable Topics - Write a custom preprocessor](https://docs.braintrust.dev/observe/topics/enable.md#write-a-custom-preprocessor) docs for examples.
6. Enter a name, click **Test** to verify output, then click **Save**.

### Step 3: Set the preprocessor as the project default

1. Navigate to **Settings → Project**.
2. Under **Default preprocessor**, select the preprocessor you just created. The selection saves automatically.

### Step 4: Verify and re-generate topics

1. Open a trace, go to the **Thread** tab, and confirm the conversation now appears.
2. In the trace's [**Evaluators** tab](https://docs.braintrust.dev/observe/examine-traces.md#test-and-apply-evaluators), test the facet on the trace to confirm facet output. See the [Custom facets - Create a facet](https://docs.braintrust.dev/observe/topics/custom-facets.md#create-a-facet) docs.
3. In **Topics**, click **Automation** and select your automation to open its status sheet.
4. At the bottom of the sheet, click **Process existing traces**, select a **Time range**, and click **Process traces**.


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