# Version Control

Epsilla’s application configuration version control enables users to **track, tag, restore, and manage configuration changes** within AI applications (e.g., workflows, agent logic, prompt chains). This feature ensures reliable iteration and safe rollback across development lifecycles.

### Accessing Version History

Click the **Version History** icon in the bottom bar to open the list of previously saved versions. Each version entry includes:

<figure><img src="/files/1KQ37cXA3JCC84nwAMrD" alt="" width="288"><figcaption></figcaption></figure>

* A **timestamp** (default label) or an optional **custom tag**
* Hover and click to **restore to that version**
* An edit icon for renaming the tag

<figure><img src="/files/K8KzEZK8Dq5XEIUACF6h" alt=""><figcaption></figcaption></figure>

> Only saved versions will appear. Unsaved changes must be saved before a new version is recorded.

### Tagging a Version

You can assign a **custom tag** to any version to help you identify important checkpoints (e.g., `PromptTest0827`, `BetaRelease`, etc.):

1. Click the **Edit icon** next to a version in the list.
2. In the **Edit Version Tag** modal, enter your custom label.
3. Click **Save** to apply the tag.

<figure><img src="/files/abPj9Rq8riSA43ieE3CA" alt=""><figcaption></figcaption></figure>

> If left blank, the version will be displayed using its timestamp.

### Restoring a Version

To roll back to a previous version:

1. Open the version history using the clock icon.
2. Hover over the desired version.
3. **Click** to restore into that version.

<figure><img src="/files/4TRBWmqZZfLEphRrsjxg" alt=""><figcaption></figcaption></figure>

### Send Chat Requests with Version Control

Epsilla allows users to invoke **specific versions** of an AI application configuration by supplying a `version_tag` in the request header. This enables reproducible experiments, A/B testing, or rollback behavior directly via API—without modifying the live application.

#### Usage

To target a specific version of your AI workflow, include the `version_tag` header in your API request. This version must already exist ( via a custom tag defined from the UI).

```bash
curl -X POST "https://rag.epsilla.com/chat/{projectId}/{appId}/{conversation-UUID}" \
     -H "X-API-Key: {Your-API-Key-Here}" \
     -H "Content-Type: application/json" \
     -H "version_tag: {Your-Version-Tag}" \
     -d '{
           "message": "{The question}"
         }'
```

#### Notes

* If `version_tag` is **omitted**, the request uses the **latest saved configuration**.
* The `version_tag` value must match exactly with one of the version tags visible in the **Version History**.
* This feature is ideal for:
  * Reproducing past results
  * Isolating bugs in specific versions
  * Controlled A/B testing across deployments

### Best Practices

* We recommend tagging the versions with meaningful names (e.g., `PromptFix0826`, `BetaDeploy`, `v1.2-customerA`). This ensures clarity and traceability across environments.
* **Save** during major edits to maintain a detailed version timeline.
* Use version history to **experiment confidently**, knowing you can always revert.


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