Most Similar Issue found during research:

• bug: template upgrade fails on claimed prebuilt workspace #17840

Based on research, this bug is new and unique.
The issue described is distinct from the existing issues. Issue #17840 is related but different - it deals with template upgrades not properly restarting claimed prebuilt workspaces due to ignore_changes
This report is specifically about the Tasks UI selecting a running prebuild without restarting it when user-specific configuration needs to run.

Problem

When creating a workspace through the Tasks UI, if a fully running prebuild is available, it is selected and assigned without being restarted. This differs from normal workspace creation, which properly restarts the prebuild to apply user-specific configuration.

This behavior causes workspaces to fail when templates rely on restart-time user configuration (e.g., workspace owner-specific setup in startup scripts), as the prebuild retains configuration from the prebuilds system user.

Current Behavior

Tasks UI Flow:

1. User selects template and preset in Tasks UI
2. User enters task details (including workspace name)
3. If a fully running prebuild exists, it is claimed immediately
4. The workspace name is updated but the prebuild is not restarted
5. User-specific configuration from the template is not applied
6. Task errors and workspace becomes unusable

Normal Workspace Creation Flow:

1. User creates workspace from template
2. If a prebuild is claimed, it is properly restarted
3. User-specific configuration runs correctly
4. Workspace functions as expected

Expected Behavior

The Tasks UI should restart claimed prebuilds to ensure user-specific configuration runs, matching the behavior of normal workspace creation.

Impact

• Tasks become unusable for templates that configure workspaces based on workspace owner
• Only occurs when at least one prebuild is fully running and available
• Workaround: If no prebuilds are running, workspace creation works correctly

Environment

• Coder Version: v2.26.2+4793806
• Template Configuration:
  • 1 template used by Tasks
  • 8 prebuilds per region × 3 regions = 24 total prebuilds
• Reproduction Conditions: At least one prebuild must be in "running" state

Steps to Reproduce

1. Configure a template with prebuilds enabled
2. Ensure template has user-specific configuration in startup scripts (e.g., based on workspace.owner)
3. Allow at least one prebuild to reach "running" state
4. Create a workspace using the Tasks UI
5. Observe that the prebuild is claimed without restart
6. Observe that user-specific configuration fails to apply

Related Issues

• bug: template upgrade fails on claimed prebuilt workspace #17840 - Template upgrade fails on claimed prebuilt workspace (different but related issue about ignore_changes and restarts)
• Regression: Workspace doesn't stop before template version change when dynamic parameters enabled #20333 - Workspace doesn't stop before template version change when dynamic parameters enabled (similar restart bypass issue)

Notes

• Issue does not occur when no prebuilds are running
• Issue appears to be specific to the Tasks UI code path
• The workspace name is updated during claim, but this change is not propagated to trigger a restart