`coder_devcontainer`: sub-agent name collides when using `for_each` / `count`; no way to override

[blinkagent]

Summary

The Terraform-managed sub-agent created for a coder_devcontainer resource derives its name from the Terraform block name only. When iterating with for_each or count, every instance shares the same block name, so all sub-agents try to claim the same workspace agent name and workspace creation fails with:

insert devcontainer "repos" subagent: insert subagent:
pq: workspace agent name "repos" already exists in this workspace build

There is no attribute on coder_devcontainer to override the sub-agent name from Terraform.

Reproduction

Plan/apply this template with Coder server 2.25+ and terraform-provider-coder 2.14.0+:

locals {
  repos = toset(["repo-a", "repo-b", "repo-c"])
}

resource "coder_devcontainer" "repos" {
  for_each         = data.coder_workspace.me.start_count > 0 ? local.repos : toset([])
  agent_id         = coder_agent.dev[0].id
  workspace_folder = "/home/user/workspaces/${each.value}"
  config_path      = "/home/user/workspaces/${each.value}/.devcontainer/devcontainer.json"
}

Result: workspace build fails because all three sub-agents are named "repos".

Root cause

In coder/coder's provisioner, the sub-agent name is taken from resource.Name, which is the Terraform block name and does not include the for_each key:

https://github.com/coder/coder/blob/main/provisioner/terraform/resources.go#L466-L471

agent.Devcontainers = append(agent.Devcontainers, &proto.Devcontainer{
    Id:              attrs.ID,
    Name:            resource.Name,   // no for_each key suffix
    WorkspaceFolder: attrs.WorkspaceFolder,
    ...
})

The coder_devcontainer provider schema has no name attribute to override this:

https://github.com/coder/terraform-provider-coder/blob/main/provider/devcontainer.go

Workarounds

1. Define each devcontainer with a unique resource block name instead of iterating. Does not scale.
2. Wrap coder_devcontainer in a module and call it once per repo. Scales, but introduces a module layer purely to work around this.
3. Set customizations.coder.name in each devcontainer.json. Requires a PR to every repository and leaks deployment concerns into the repo.

Proposal

Add an optional name attribute to coder_devcontainer:

resource "coder_devcontainer" "repos" {
  for_each         = local.repos
  name             = each.value   # new
  agent_id         = coder_agent.dev[0].id
  workspace_folder = "/home/user/workspaces/${each.value}"
  config_path      = "..."
}

When set, name takes precedence over the block name when the provisioner constructs the proto.Devcontainer. This mirrors the customizations.coder.name escape hatch on the devcontainer.json side but keeps the override in Terraform, where the rest of the iteration already lives.

Environment

• Coder server: v2.32.0
• Coder CLI / agent: v2.31.6+f765029
• terraform-provider-coder: v2.14.0

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Created on behalf of manuel.anda@torc