Issue Dedup — search before you create (HARD GATE)

The repo is issue-first: the first action for any initiative is opening the tracking issue. The trap that creates is duplicate / colliding issues — a teammate (or a past you, in an ephemeral session) already opened the epic, and a fresh agent dutifully opens a second one. github-tasks already says "search before creating," but that was a soft, skippable step. This skill makes it a gate, and a PreToolUse hook (require-issue-dedup.mjs) backstops it so a create can't land without proof a search ran.

Scope split: this is the create-time gate (don't mint a duplicate). The pickup-time gate — "should this issue even be done?" — is the sibling /issue-sanity-check skill. Both are sub-issues of epic #297.

When this fires

Any time you're about to call mcp__github__issue_write with method: create — a new epic, sub-issue, or standalone issue. Run the procedure below first.

Procedure

1. Extract search terms

Pull 2–5 distinctive keywords from the intended title/body — the nouns of the work (feature name, package/app, the thing being changed). Drop filler ("add", "fix", "the").

2. Auto-search open and recently-closed work

Stale-but-closed issues matter: the #257/#265 blog case duplicated closed epics. Search both:

mcp__github__search_issues  query: "repo:FriendlyInternet/nuxt-crouton <keywords>"
mcp__github__search_issues  query: "repo:FriendlyInternet/nuxt-crouton in:title <keyword>"
mcp__github__list_issues    labels: ["epic"]      # scan epic titles for overlap

Run a couple of phrasings — exact-title and broad-body — and include state:closed in at least one. Keep results in-context: these calls overflow easily (a bare list_issues labels:["epic"] came back at ~140k chars), so pass minimal_output: true, a small perPage (5–10), and prefer in:title filters — only widen if a narrow query misses. If output still overflows, narrow further rather than slicing the blob out-of-band.

3. Surface the matches to the human (number · state · why-similar)

Present a short table of candidates — never silently proceed:

#	State	Title	Why it might be the same
#297	open	Stale-epic dedup…	same feature — the dedup gate
#265	closed (completed)	POC pipeline preview URL	adjacent, not the same

If a candidate's closing comment cites artifacts (writeups, PRs) that don't exist in the repo, flag it — that's the #297 smell (a stale close hiding undone work).

4. Force a reuse / replace / new decision — this is the hard stop

Do not create until one is chosen:

• Reuse — a match already covers this. Stop. Don't create. Continue that issue (assign yourself, status:in-progress). This is the whole point of the gate.
• Replace — a stale/closed issue should be superseded. Link it in the new body (Supersedes #NN) and, if it's open, close it not_planned referencing the replacement.
• New — genuinely nothing matches (or matches are only adjacent). Proceed to create.

How to ask (the on-match signal):

• Interactive session → ask in chat with AskUserQuestion (reuse / replace / new) and wait. This is the cheapest stop.
• Autonomous / pipeline (no human in the loop to block on) → you may create the issue, but immediately post a reply comment on it naming the suspected duplicate(s) and asking the owner to confirm reuse / replace / keep — assigned to them so it surfaces. A created issue with an unresolved dup question is honest; a silent duplicate is not.

5. Record the dedup result in the body (REQUIRED — the hook checks for it)

Every created issue body MUST end with a one-line dedup attestation — it's both the audit trail and the token the backstop hook greps for. Format:

_Dedup-checked: searched «keyword, keyword» → no match_

or, when something related turned up:

_Dedup-checked: searched «dedup, issue» → related #297 (open), #800 (open); new because this is the create-time half_

The literal prefix Dedup-checked: is what the hook requires. Omit it and require-issue-dedup.mjs blocks the create with a reminder to run this skill.

The backstop hook

.claude/hooks/require-issue-dedup.mjs is a PreToolUse gate on mcp__github__issue_write:

• Only gates method: create — update and everything else pass untouched.
• Blocks (exit 2) when the body lacks a Dedup-checked: line.
• Mirrors require-comment-provenance.mjs exactly (body-content check, no state).

It's a backstop, not the brain — it can't tell whether you really searched, only that you attested. Do the real search (steps 1–4); the marker is your signed receipt.

What this is not

• Not the pickup gate — that's /issue-sanity-check (#800).
• Not a substitute for judgement — "related" ≠ "duplicate". Adjacent issues coexist; only a genuine same-scope overlap is a reuse/replace.