Code Duplication Checks

Authoritative procedure composition

Before executing this skill, read .agents/skills/deduplicate-code/PROCEDURE.md in full. That file preserves the complete established duplicate-code procedure. This SKILL.md is the authoritative entrypoint and owns the differential-causality and control-plane corrections below; on conflict, this file wins.

All retained whole-repository scanner scope, finding classification, consolidation, suppression-merit, migration/test-surface, forbidden-silencing, rerun, and evidence rules remain normative except where this entrypoint explicitly replaces historical-baseline causality.

Ticket-differential uses the Execution Anchor

When delegated by $implement-ticket, ticket-differential receives:

TICKET_BASELINE
    immutable historical ticket lineage only

EXECUTION_ANCHOR
    exact fetched shared-branch commit admitted before this implementation attempt

candidate
    exact working candidate relative to EXECUTION_ANCHOR

For ticket-differential, EXECUTION_ANCHOR is the comparison base. TICKET_BASELINE is not the scanner/differential baseline and must never be used to create the isolated comparison worktree for the current attempt.

Run whole-repository candidate scans in the current exact worktree as before. Establish comparison evidence against an isolated read-only EXECUTION_ANCHOR worktree/ref.

A reusable ticket-differential comparison scan is valid only while all of these are unchanged:

• exact EXECUTION_ANCHOR;
• scanner executable/toolchain versions;
• Execution-Anchor Arid/JSCPD configuration and suppression-policy files;
• scan scope/configuration semantics used for the differential comparison.

Interpret the retained four causality states against EXECUTION_ANCHOR:

candidate-introduced
candidate-expanded
baseline-identical
unresolved

Here baseline-identical means identical to the Execution Anchor. Legitimate shared-branch/prerequisite/workflow changes between historical Ticket baseline and Execution Anchor are inherited upstream state and cannot become ticket-attributable duplicate debt.

Spec-differential uses the verify-spec attribution manifest

When delegated by $verify-spec, the fixed Spec baseline remains immutable lineage and contract history. It is not, by itself, the technical-gate causality boundary for a long-lived Spec branch that has also absorbed upstream/default-branch work.

$verify-spec must first build the current machine attribution manifest with:

python .agents/skills/verify-spec/scripts/verify_spec_attribution.py build \
  --repo . \
  --default-ref origin/main \
  --candidate-ref HEAD \
  --output <verify-spec-attribution.json>

Require exact:

VERIFY-SPEC ATTRIBUTION: VALID

The manifest distinguishes:

candidate_attributable_paths
    branch-side paths whose exact candidate blob is not current default-branch state

inherited_default_equivalent_paths
    branch-side paths whose exact candidate blob equals current default-branch state

Whole-repository Arid/JSCPD scanner scope is unchanged. The attribution manifest changes repair/blocking causality only.

Before applying the retained spec-differential four-state classification, disposition a scanner relation as upstream-inherited when all of these hold:

1. none of the relation's occurrence paths is in candidate_attributable_paths;
2. no candidate-attributable scanner configuration or suppression-policy change caused its visibility; and
3. the scanner completed normally.

upstream-inherited findings are reported as inherited repository state and do not enter the $verify-spec repair loop or block Spec PASS. They are not silently called baseline-identical; retain their actual upstream/default-branch causality.

Any relation touching at least one candidate_attributable_paths entry remains subject to the retained Spec-baseline correlation and may become candidate-introduced, candidate-expanded, baseline-identical, or unresolved as appropriate. Operational scanner/source-processing errors remain blocking regardless of path attribution.

A path that diverges from current default branch is candidate-attributable even when it is a workflow/control-plane path. This rule therefore cannot be used to hide Spec-owned or branch-owned workflow divergence merely because the path is broadly classified as workflow code.

The fixed Spec baseline is still supplied to spec-differential for historical correlation of the remaining candidate-attributable relations. It must never be used to turn an exact current default-branch-equivalent path into Spec-attributable duplicate debt.

Protected control-plane boundary

When delegated by $implement-ticket, this skill has zero authority to modify protected workflow/control-plane or semantic-authority paths. A duplicate finding does not grant such authority, even when consolidation would otherwise be the preferred repository-wide repair.

Before classifying or repairing ticket-attributable findings, require:

python -m scripts.workflow_candidate_guard check \
  --anchor <execution-anchor>

Run it again after every deduplication repair batch and before returning control to $implement-ticket.

If a candidate-introduced or candidate-expanded duplicate relation can be resolved only by changing a protected path:

1. leave the protected path untouched;
2. do not add a suppression there;
3. do not weaken scanner configuration;
4. report the relation as blocked by the workflow/control-plane ownership boundary;
5. return control to $implement-ticket for upstream routing.

The protected path set is owned by scripts.workflow_candidate_guard; this skill must not redefine, narrow, bypass, or locally override it.

If the candidate already contains a protected-path mutation, stop immediately. The parent $implement-ticket may use its narrow restoration command to restore those paths exactly to the Execution Anchor; $deduplicate-code itself does not perform that recovery.

Terminal evidence for ticket-differential

In addition to the retained differential evidence, report:

Ticket baseline: <immutable historical sha>
Execution Anchor: <exact comparison sha>
Differential comparison base: Execution Anchor
Protected control-plane candidate paths: 0

A ticket-differential PASS is invalid if the comparison worktree was created from TICKET_BASELINE, if the supplied Execution Anchor is missing/mismatched, or if any protected control-plane candidate path remains.

Terminal evidence for spec-differential

In addition to the retained Spec differential evidence, report:

Spec baseline: <immutable historical sha>
Default branch head: <exact attribution-manifest sha>
Candidate head: <exact attribution-manifest sha>
Candidate-attributable paths: <n>
Inherited default-equivalent paths: <n>
Upstream-inherited duplicate findings: <n>

A spec-differential PASS is invalid if the attribution manifest does not bind the exact candidate HEAD or current fetched default-branch head, or if an unresolved relation remains.

All standalone/default behavior not explicitly overridden here remains unchanged from the retained procedure.