sweep

name	sweep
user-invocable	false
description	Internal drydry detection pass over a known scope and checklist; returns verified duplication findings only.
allowed-tools	["Agent","Read","Glob","Grep","Bash(date *)","Bash(rg *)","Bash(grep *)","Bash(find *)","Bash(wc *)","Bash(ls *)"]
effort	high

Sweep

The detection pass behind the drydry audit pipeline. It runs an independent pass over a named scope against a named checklist and returns a structured findings list with a runnable verifier per finding. Not user-invocable; the operator types /drydry:drydry and the orchestrator routes here.

Input contract

Caller supplies through args:

• scope: a directory, a glob, a package root, or a comma-separated list of files. Mandatory.
• checklist: either an inline markdown blob (the six-to-ten patterns), or a path to a markdown file containing one. Mandatory. Use drydry:checklist upstream when the caller does not already have one.
• exclude: optional comma-separated list of paths to exclude (vendor, generated, .bundle/, node_modules/, build outputs). Default excludes are inferred from .gitignore plus a built-in list.
• max_findings_per_pattern: optional cap, default 5. Prevents one rampant pattern from drowning out the rest.
• max_files: optional cap on the file count walked before the skill downsamples by language. Default 2000.

Output contract

Return a JSON-like markdown structure with one section per checklist pattern:

## Pattern: <pattern_id> -- <short pattern title>

- Finding 1
  - file_a: `<path>:<line>`
  - file_b: `<path>:<line>`
  - drift_hypothesis: <one sentence; the Chapter 4 test must pass>
  - verifier_command: `<runnable command>`
  - verifier_expected: <what the command should output to re-confirm>
- Finding 2
  - ...

## Pattern: <pattern_id_2> -- ...

Patterns with zero findings appear as _no findings under this pattern_. Patterns where the detector flagged "interesting but off-list" hits go under a separate ## Checklist gaps section at the end (Chapter 3 keeps them out of the findings proper).

Workflow

1. Read the inputs. Parse scope, load checklist. Compute default excludes from .gitignore plus the built-in list (.git/, node_modules/, vendor/, .bundle/, build/, dist/, target/, .next/, coverage/, tmp/).

2. Size the scope. Run find <scope> -type f | wc -l to gauge file count after excludes. When the count exceeds the caller's max_files (default 2000; the caller passes a different value when their project warrants it), downsample by language: keep all the language's primary source files, drop tests and fixtures unless the checklist explicitly names them. Log the downsample decision so the caller can verify.

3. Build the detector prompt. Use the template in this skill's body (see "Detector prompt template" below). Pass:

   • The checklist verbatim.
   • The scope file list (or a glob the detector can expand itself).
   • The verifier-burden rule (every finding carries a runnable verifier).
   • The drift-hypothesis rule (every finding carries a Chapter 4 sentence).
   • The off-list rule (anything outside the checklist goes to ## Checklist gaps, not into the findings).
   • The max_findings_per_pattern cap.

4. Run the independent detector. Use the host's native independent-review capability when available. In Claude Code this can be an Agent tool call with subagent_type: Explore; in Codex use native subagents when exposed, otherwise run a separate deliberate pass in the current session and record that limitation in the returned method notes. The detector needs read/search/shell access for verifier work. Token budget: enough for a thorough walk; do not skim.

5. Filter the response. Walk the detector's output:

   • Drop any finding without a verifier_command.
   • Drop any finding whose drift_hypothesis matches the Chapter 4 anti-patterns ("a bit messy", "would be cleaner to share", "feels redundant" without a concrete bad-thing-if-drifts).
   • Cap each pattern at max_findings_per_pattern.
   • Keep ## Checklist gaps separately.

5b. Run each verifier in this skill's own context. For every finding that survived step 5, execute its verifier_command here in sweep, not relying on the detector's claim that it ran. Drop the finding if the command exits non-zero, produces no matching output, or returns lines that do not contain both file_a and file_b. This is the only check with teeth; the detector's self-report is not enough.

6. Return. Hand back the filtered markdown structure to the caller. Do not write to disk; the caller owns the artefact.

Detector prompt template

You are a duplication-detection reviewer.

Scope: <inline or file list>
Excludes: <comma-separated>

Checklist (the only patterns you may report under):

<inline checklist verbatim>

Rules:

1. For each pattern, find at most <max_findings_per_pattern> distinct
   instances in scope. A "finding" is a pair (or set) of locations that
   match the pattern.

2. Verifier-burden discipline. For every finding, produce a runnable
   command (grep, rg, ast-grep, find ... -exec) that re-confirms the
   pair without you in the loop. If you cannot produce one, drop the
   finding. Do not invent a command you did not actually run.

3. Drift-hypothesis discipline. For every finding, write one sentence
   that answers "what bad thing happens if these two paths keep
   drifting?". Do not write "the code is a bit messy" or "it would be
   cleaner to share"; those are not drift hypotheses. Write the
   concrete consequence (a UI bug, a silent data loss, a localisation
   miss, a security regression, a deploy that breaks the second path).

4. Off-list rule. If you notice a pattern that is not in the checklist
   but seems important, do not silently report it under the closest
   matching pattern. Put it under a separate "## Checklist gaps"
   section at the end so the operator can fold it into the next sweep.

5. Output format: per pattern, the schema below.

   ## Pattern: <pattern_id> -- <short pattern title>

   - Finding 1
     - file_a: `<path>:<line>`
     - file_b: `<path>:<line>`
     - drift_hypothesis: <one sentence>
     - verifier_command: `<runnable command>`
     - verifier_expected: <what the command outputs to re-confirm>

   Empty patterns: "_no findings under this pattern_".

Do your homework: actually run the verifier commands you propose, do
not paste a regex you think looks right. The pipeline drops findings
whose verifier does not run cleanly.

Rules

• Verifier-burden is mandatory. Hits without a runnable verifier are dropped at filter-time even if the detector reported them.
• Drift hypothesis is mandatory. A hit without a Chapter 4 sentence is dropped.
• Off-list hits go to ## Checklist gaps, not into the findings. Chapter 3 keeps the audit deterministic.
• The orchestrator owns the artefact. This skill returns markdown to the caller and writes nothing to disk.
• Token honesty. When the scope is too large to walk thoroughly, downsample and log the decision instead of pretending the walk was complete.