Backtrail Implement

Purpose

Implement an existing CHANGE record after confirming selected work with the user. If the CHANGE has TASK records, implement eligible TASK records first; otherwise implement the CHANGE directly.

Input

Use the text after this skill invocation to select the CHANGE record.

Statuses

• Allowed CHANGE statuses: Proposed, Blocked, Done, Abandoned.
• Allowed TASK statuses: Todo, Blocked, In Progress, Done, Cancelled.
• Treat dependency readiness as derived from linked CHANGE or TASK statuses, not from Blocked alone.
• CHANGE Blocked means waiting on CHANGE dependencies listed in Blocked By.
• TASK Blocked means waiting on TASK dependencies listed in Blocked By.

Workflow

1. Read .backtrail/changes.md, .backtrail/tasks.md, .backtrail/adl.md, and .backtrail/features.md when they exist.
2. Select work.
   • If input starts with CHANGE-00014, CHANGE 00014, C-00014, #14, #014, 014, or 14, prefer the matching CHANGE record when it exists.
   • Otherwise, list eligible CHANGE records: status neither Done nor Abandoned, and not Blocked unless every CHANGE listed in Blocked By is Done.
   • If no eligible CHANGE records exist, stop and report that no implementable CHANGE exists.
   • If exactly one eligible CHANGE record exists, select it automatically.
   • If two or more eligible CHANGE records exist, ask the user to choose one. Use request_user_input when available.
3. Stop unless the selected CHANGE exists.
4. If the selected CHANGE is Blocked, read every CHANGE listed in Blocked By.
   • If any blocker is missing, stop and report the missing CHANGE links.
   • If any blocker status is not Done, stop and report the blocking CHANGE ids and statuses.
   • If every blocker is Done, update the selected CHANGE file and .backtrail/changes.md from Blocked to Proposed before continuing.
5. If the selected CHANGE links ADRs, stop unless every linked ADR exists and has status Accepted.
6. If the selected CHANGE links FEATUREs, stop unless every linked FEATURE exists and has status Accepted.
7. Read the selected CHANGE, linked TASKs, and linked ADRs or FEATUREs, if any.
   • Linked TASKs are defined only by the selected CHANGE file's canonical ## Tasks section.
   • Canonical TASK link format: - [TASK-NNNNN](tasks/task-NNNNN-title-slug.md).
   • Ignore TASK ids outside the ## Tasks section for CHANGE-to-TASK linkage.
   • Stop if .backtrail/tasks.md lists tasks for the selected CHANGE that are missing from the CHANGE ## Tasks section; ask to fix task links first.
   • Stop if the ## Tasks section contains malformed links, duplicate TASK ids, missing TASK files, or TASK records whose Change field does not match the selected CHANGE.
8. Choose implementation mode.
   • If the CHANGE has linked TASK records that are not Done or Cancelled, implement TASK mode.
   • If the CHANGE has no linked TASK records, implement CHANGE mode.
   • If every linked TASK is Done or Cancelled, skip code changes and continue to CHANGE completion checks.
9. TASK mode:
   • Unless the user explicitly states otherwise, select and implement only one TASK per invocation.
   • Validate each linked TASK belongs to the selected CHANGE and does not expand CHANGE scope.
   • Treat TASK records with status Cancelled as excluded work. Stop if cancelled work is required for CHANGE acceptance.
   • Unblock TASK records before selection when every TASK listed in Blocked By is Done; update each unblocked TASK file and .backtrail/tasks.md from Blocked to Todo.
   • Eligible TASKs have status Todo or In Progress and no unfinished blockers.
   • If no eligible TASK exists, stop and report remaining TASK blockers and statuses.
   • If exactly one eligible TASK exists, select it automatically. If two or more eligible TASKs exist, ask the user to choose one; include parallel TASKs as separate choices.
   • Summarize selected TASK goal, scope, acceptance criteria, verification, dependency context, and parent CHANGE context.
   • Prepare step-by-step TASK implementation plan.
   • Ask whether to implement the selected TASK now.
     • Use Yes/No buttons when request_user_input is available.
     • Yes: continue to implementation.
     • No: stop without changing files.
   • Before code changes, update the selected TASK file and .backtrail/tasks.md status to In Progress unless already In Progress.
   • Implement only selected TASK scope and run its verification.
   • If verification passes, update the selected TASK file and .backtrail/tasks.md status to Done.
   • If verification passes, read each TASK listed in selected TASK Blocks; when all its blockers are Done, update that TASK file and .backtrail/tasks.md from Blocked to Todo.
   • If verification fails, leave selected TASK as In Progress and report failures.
   • After a TASK reaches Done, if every linked TASK for the CHANGE is Done or Cancelled, run CHANGE-level verification when specified. If it passes, update the CHANGE file and .backtrail/changes.md status to Done; otherwise leave CHANGE status unchanged and report failures.
10. CHANGE mode:

• Summarize decision context, change scope, implementation steps, verification, dependencies, and rollback. For standalone CHANGE records, state that no ADR or FEATURE gate applies.
• Prepare step-by-step CHANGE implementation plan.
• Ask whether to implement the selected CHANGE now.
  • Use Yes/No buttons when request_user_input is available.
  • Yes: continue to implementation.
  • No: stop without changing files.
• Implement the CHANGE and run its verification.
• If verification passes, update the CHANGE file and .backtrail/changes.md status to Done.
• If verification fails, leave status unchanged and report failures.

11. When TASK or CHANGE implementation reaches Done, propose a commit message for the finished work based on finished scope
12. If the CHANGE reaches Done, read each CHANGE listed in Blocks.

• If the blocked CHANGE is missing, report the missing link and continue without inventing a record.
• If every CHANGE listed in that record's Blocked By field is Done, update that CHANGE file and .backtrail/changes.md status from Blocked to Proposed.
• If any blocker is not Done, leave the dependent CHANGE as Blocked and report remaining blockers.

13. If the CHANGE reaches Done and implements linked FEATUREs, update those FEATURE files and .backtrail/features.md status to Implemented.

Question UX

• Use request_user_input when available for two or three meaningful choices.
• For yes/no decisions, present Yes and No choices.
• If request_user_input is unavailable, ask one concise plain-text question with numbered choices.
• Do not claim that a skill can switch modes or force button rendering.

Guardrails

• Do not infer missing CHANGE records.
• If implementation needs to change an ADR decision, stop and ask for a new or updated ADR.
• If implementation needs to change a FEATURE scope, acceptance criteria, or status gate, stop and ask for a new or updated FEATURE.
• If implementation needs a different scope than the CHANGE describes, stop and ask whether to update the CHANGE first.
• In TASK mode, do not implement outside selected TASK scope.
• In TASK mode, default to one TASK at a time. Do not batch multiple TASKs unless explicitly requested.
• Do not mark a CHANGE Done until every linked TASK is Done or Cancelled and CHANGE-level verification passes when specified.