When a devcontainer subagent is terraform-managed, the provisioner sets
its directory to the host-side `workspace_folder` path at build time. At
runtime, the agent injection code determines the correct
container-internal
path from `devcontainer read-configuration` and sends it via
`CreateSubAgent`.
However, the `CreateSubAgent` handler only updated `display_apps` for
pre-existing agents, ignoring the `Directory` field. This caused
SSH/terminal
sessions to land in `~` instead of the workspace folder (e.g.
`/workspaces/foo`).
Add `UpdateWorkspaceAgentDirectoryByID` query and call it in the
terraform-managed subagent update path to also persist the directory.
Fixes PLAT-118
<details><summary>Root cause analysis</summary>
Two code paths set the subagent `Directory` field:
1. **Provisioner (build time):** `insertDevcontainerSubagent` in
`provisionerdserver.go`
stores `dc.GetWorkspaceFolder()` — the **host-side** path from the
`coder_devcontainer` Terraform resource (e.g. `/home/coder/project`).
2. **Agent injection (runtime):**
`maybeInjectSubAgentIntoContainerLocked` in
`api.go` reads the devcontainer config and gets the correct
**container-internal**
path (e.g. `/workspaces/project`), then calls `client.Create(ctx,
subAgentConfig)`.
For terraform-managed subagents (those with `req.Id != nil`),
`CreateSubAgent`
in `coderd/agentapi/subagent.go` recognized the pre-existing agent and
entered
the update path — but only called `UpdateWorkspaceAgentDisplayAppsByID`,
discarding the `Directory` field from the request. The agent kept the
stale
host-side path, which doesn't exist inside the container, causing
`expandPathToAbs` to fall back to `~`.
</details>
> [!NOTE]
> Generated by Coder Agents
Garrett Delfosse
3462c31f43