Feature: title-based deduplication for create-issue safe-output handler

[kaovilai]

Problem

Agents emit duplicate create_issue safe-output messages within a single run. Even with explicit prompt instructions ("do not create duplicates", "track your own output"), the LLM still produces multiple create_issue calls with identical titles in the same conversation.

Example from https://github.com/kaovilai/dotfiles/actions/runs/25941313101:

• #41 and #43 — identical title, same run
• #42 and #44 — identical title, same run

Prompt engineering is unreliable for this. The dedup should happen at the handler level.

Proposed Solution

Add a deduplicate option to the create-issue safe-output handler config:

safe-outputs:
  create-issue:
    deduplicate: true

When enabled, the handler should skip a create_issue message if:

1. Within-run dedup: Another message in the same run already created an issue with the same (or very similar) title
2. Repo-level dedup: An open or recently-closed issue in the repo already has the same title (with the configured title-prefix)

The handler already has max and title_prefix — dedup fits naturally alongside these.

Why Handler-Level

• Agent can't bypass it — dedup happens after the LLM emits messages, before GitHub API calls
• Zero prompt engineering needed — works regardless of model, temperature, or instruction-following quality
• Consistent behavior across all workflows using create-issue

Related

Filed from https://github.com/kaovilai/dotfiles — workflow dotfiles-improvements consistently produces duplicate issues across runs.

Note

Responses generated with Claude

[pelikhan]

@copilot

• add field "deduplicate-by-title"
• support Boolean or number that indicates levenstein distance
• apply check in safe outputs MCP server to provide immediate feedback to the agent
• apply check when creating issues as well
• log any dropped duplicate, render in step summary
• implement levenstein distance in separate file with full test suite