Files
coder/docs
Kacper Sawicki 1e07ec49a6 feat: add merge_strategy support for coder_env resources (#23107)
## Description

Implements the server-side merge logic for the `merge_strategy`
attribute added to `coder_env` in [terraform-provider-coder
v2.15.0](https://github.com/coder/terraform-provider-coder/pull/489).
This allows template authors to control how duplicate environment
variable names are combined across multiple `coder_env` resources.

Relates to https://github.com/coder/coder/issues/21885

## Supported strategies

| Strategy | Behavior |
|----------|----------|
| `replace` (default) | Last value wins — backward compatible |
| `append` | Joins values with `:` separator (e.g. PATH additions) |
| `prepend` | Prepends value with `:` separator |
| `error` | Fails the build if the variable is already defined |

## Example

```hcl
resource "coder_env" "path_tools" {
  agent_id       = coder_agent.dev.id
  name           = "PATH"
  value          = "/home/coder/tools/bin"
  merge_strategy = "append"
}
```

## Changes

- **Proto**: Added `merge_strategy` field to `Env` message in
`provisioner.proto`
- **State reader**: Updated `agentEnvAttributes` struct and proto
construction in `resources.go`
- **Merge logic**: Added `mergeExtraEnvs()` function in
`provisionerdserver.go` with strategy-aware merging for both agent envs
and devcontainer subagent envs
- **Tests**: 15 unit tests covering all strategies, edge cases (empty
values, mixed strategies, multiple appends)
- **Dependency**: Bumped `terraform-provider-coder` v2.14.0 → v2.15.0
- **Fixtures**: Updated `duplicate-env-keys` test fixtures and golden
files

## Ordering

When multiple resources `append` or `prepend` to the same key, they are
processed in alphabetical order by Terraform resource address (per the
determinism fix in #22706).
2026-03-18 15:43:28 +01:00
..
2025-06-25 15:17:49 +00:00

About

Coder is a self-hosted, open source, cloud development environment that works with any cloud, IDE, OS, Git provider, and IDP.

Screenshots of Coder workspaces and connectionsScreenshots of Coder workspaces and connections

Coder is built on common development interfaces and infrastructure tools to make the process of provisioning and accessing remote workspaces approachable for organizations of various sizes and stages of cloud-native maturity.

IDE support

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You can use:

Why remote development

Remote development offers several benefits for users and administrators, including:

  • Increased speed

    • Server-grade cloud hardware speeds up operations in software development, from loading the IDE to compiling and building code, and running large workloads such as those for monolith or microservice applications.
  • Easier environment management

    • Built-in infrastructure tools such as Terraform, nix, Docker, Dev Containers, and others make it easier to onboard developers with consistent environments.
  • Increased security

    • Centralize source code and other data onto private servers or cloud services instead of local developers' machines.
    • Manage users and groups with SSO and Role-based access controlled (RBAC).
  • Improved compatibility

    • Remote workspaces can share infrastructure configurations with other development, staging, and production environments, reducing configuration drift.
  • Improved accessibility

    • Connect to remote workspaces via browser-based IDEs or remote IDE extensions to enable developers regardless of the device they use, whether it's their main device, a lightweight laptop, Chromebook, or iPad.

Read more about why organizations and engineers are moving to remote development on our blog, the Slack engineering blog, or from OpenFaaS's Alex Ellis.

Why Coder

The key difference between Coder and other remote IDE platforms is the added layer of infrastructure control. This additional layer allows admins to:

  • Simultaneously support ARM, Windows, Linux, and macOS workspaces.
  • Modify pod/container specs, such as adding disks, managing network policies, or setting/updating environment variables.
  • Use VM or dedicated workspaces, developing with Kernel features (no container knowledge required).
  • Enable persistent workspaces, which are like local machines, but faster and hosted by a cloud service.

How much does it cost?

Coder is free and open source under GNU Affero General Public License v3.0. All developer productivity features are included in the Open Source version of Coder. A Premium license is available for enhanced support options and custom deployments.

How does Coder work

Coder workspaces are represented with Terraform, but you don't need to know Terraform to get started. We have a database of production-ready templates for use with AWS EC2, Azure, Google Cloud, Kubernetes, and more.

Providers and compute environmentsProviders and compute environments

Coder workspaces can be used for more than just compute. You can use Terraform to add storage buckets, secrets, sidecars, and more.

Visit the templates documentation to learn more.

What Coder is not

  • Coder is not an infrastructure as code (IaC) platform.

    • Terraform is the first IaC provisioner in Coder, allowing Coder admins to define Terraform resources as Coder workspaces.
  • Coder is not a DevOps/CI platform.

    • Coder workspaces can be configured to follow best practices for cloud-service-based workloads, but Coder is not responsible for how you define or deploy the software you write.
  • Coder is not an online IDE.

    • Coder supports common editors, such as VS Code, vim, and JetBrains, all over HTTPS or SSH.
  • Coder is not a collaboration platform.

    • You can use Git with your favorite Git platform and dedicated IDE extensions for pull requests, code reviews, and pair programming.
  • Coder is not a SaaS/fully-managed offering.

    • Coder is a self-hosted solution. You must host Coder in a private data center or on a cloud service, such as AWS, Azure, or GCP.

Using Coder v1?

If you're a Coder v1 customer, view the v1 documentation or the v2 migration guide and FAQ.

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