TFE v202311-1/v202312-1: Operation failed: failed packing filesystem: illegal slug error: invalid symlink – HashiCorp Help Center

Problem

When running a plan in a Terraform Enterprise workspace, the operation fails after the plan phase with an illegal slug error. This prevents the workspace from proceeding to an apply.

Terraform will perform the following actions:
# null_resource.test will be created
+ resource "null_resource" "test" {
+ id = (known after apply)
}
Plan: 1 to add, 0 to change, 0 to destroy.
Operation failed: failed packing filesystem: illegal slug error: invalid symlink ("/home/tfc-agent/.tfc-agent/component/terraform/runs/run-HUDejy6P2Y3Hnxnc/config/stage/.terraform/providers/registry.terraform.io/hashicorp/null/3.1.1/linux_amd64" -> "/home/tfc-agent/.tfc-agent/component/terraform/runs/run-HUDejy6P2Y3Hnxnc/.terraform.d/plugins/registry.terraform.io/hashicorp/null/3.1.1/linux_amd64") has external target

Prerequisites

This issue occurs in environments with the following configuration:

Terraform Enterprise version v202311-1 or v202312-1.
Using a Terraform Bundle as documented in the Terraform Bundle README.
The workspace uses a VCS integration with a Terraform Working Directory specified.

Cause

This error occurs due to a compatibility issue in specific versions of Terraform Enterprise. The tfe-agent was updated to version 1.13.0 in TFE v202311-1 and 1.14.0 in TFE v202312-1. These agent versions do not work correctly with Terraform Bundles when the workspace is configured to use a VCS-backed working directory.

Solutions

Solution 1: Upgrade Terraform Enterprise

Upgrade the Terraform Enterprise environment to version v202401-1 or newer. This version includes a fix for the agent incompatibility.

Solution 2: Downgrade the TFE Agent

If an immediate upgrade is not possible, you can resolve the issue by configuring your Terraform Enterprise instance to use a custom agent image based on the older 1.12.0 version.

Create a custom agent image. Follow the guide on How to Add Custom Certificates to Terraform Agents for use with Terraform Enterprise, using the following Dockerfile to specify agent version 1.12.0.
```
FROM hashicorp/tfc-agent:1.12.0
USER root
ENV TFC_AGENT_AUTO_UPDATE=disabled
USER tfc-agent
```
Update your Terraform Enterprise Flexible Deployment Options (FDO) settings to use this custom agent image.
```
TFE_RUN_PIPELINE_IMAGE: "your-registry/custom-agent-image:latest"
```

Outcome

After applying one of the solutions, Terraform plans should execute successfully without the illegal slug error.

Additional Information

For general guidance on troubleshooting plan failures, refer to Troubleshoot Plan operation failures in Terraform Enterprise.