prj-detect-overlap

name	prj-detect-overlap
description	PR Jangler duplicate and overlap detector. Use when the orchestrator dispatches the overlap check after triage marked a PR as possible-duplicate, or when the user runs 'prj-detect-overlap' for manual debug.

prj-detect-overlap

Overview

This skill is the overlap-and-duplication detector for the PR Jangler module. One invocation scores one target PR's file footprint against every other open PR in the queue, runs a structured semantic comparison on the high-overlap pairs, and writes a verdict that drives the next phase transition. The deterministic plumbing (file overlap scan via gh pr diff --name-only, label application via gh pr edit, overlap report rendering, atomic state I/O) lives in Python scripts. The semantic comparison itself is LLM-driven from assets/prompt-semantic-compare.md; the script accepts the per-pair verdicts on the CLI and persists them.

Act as a careful cross-referencer. Treat any 2-shared-files pair as worth a semantic look, but apply verdicts conservatively: independent is the default when comparison is unclear, redundant requires near-identical intent on near-identical files, and conflicting requires the two diffs to disagree on the same lines or contracts.

Conventions

• Bare paths (e.g. scripts/run.py) resolve from the skill root.
• {project-root}/... resolves from the project working directory.
• Configuration variables live under [modules.prj] in {project-root}/_bmad/config.toml.
• All state I/O goes through prj-orchestrator's state_io module (imported via sys.path); this skill never touches state.json directly.

On Activation

The orchestrator passes --pr-number N (the target). Load configuration from {project-root}/_bmad/config.toml ([modules.prj]). Required key: prj_repo. If absent, exit early with status misconfigured and a clear run-log entry.

Two-step workflow:

Step 1: scan for overlap pairs

python3 scripts/run.py --pr-number N --scan

This invokes gh pr diff --name-only for the target PR and every other open PR, computes intersections, and emits a JSON pairs report on stdout. Each pair carries the two PR numbers, the shared file list, and the overlap count. Pairs with fewer than 2 shared files are filtered out and listed under skipped.

If pairs is empty, the script writes the overlap report (empty table), transitions the PR to ReviewPending, applies no labels, and exits. No semantic comparison is needed.

Step 2: invoke semantic comparison for each pair

For every pair returned in step 1, read assets/prompt-semantic-compare.md, fill in the variables (target PR diff, other PR diff, shared files), and run the comparison. Pick exactly one verdict per pair:

• independent — the two diffs touch the same files but address unrelated concerns
• conflicting — the two diffs disagree on the same lines, the same contracts, or mutually exclusive approaches
• complementary — the two diffs work together; the older one logically lands first
• redundant — the two diffs do the same thing on the same surface; one of them should be closed

Then persist all verdicts in one call:

python3 scripts/run.py --pr-number N --verdicts-json '{"82": "complementary", "75": "independent"}'

The script applies labels, writes the overlap report at prs/{n}/overlap.md, executes the phase transition, and appends a run-log entry. Pass --rationale-json '{"82": "...", "75": "..."}' to surface one-paragraph rationales in the report (optional but strongly recommended; the prompt asks for them).

Flags on scripts/run.py:

• --pr-number N (required) — target PR number.
• --scan — run step 1 only (emit pairs as JSON, do not persist).
• --verdicts-json STR — JSON object mapping other_pr_number (string) -> verdict.
• --rationale-json STR — JSON object mapping other_pr_number (string) -> one-paragraph rationale.
• --dry-run — compute everything, log intent, do not call gh, do not write state, do not write the report.
• --skip-label — perform state and cache writes but skip the gh label call.
• --verbose — emit progress diagnostics to stderr.
• --project-root PATH — override autodetect.

See python3 scripts/run.py --help for full detail.

Verdict Aggregation and Phase Transitions

The target PR receives one final phase based on the strongest verdict across all pairs (most-severe wins):

Strongest pair verdict	Target PR phase	Target PR next_action	Labels applied
redundant	Rejected	null	prj/overlap:duplicate, prj/triage:definite-no
conflicting	Blocked (target is newer)	null	prj/overlap:conflicts-with-{other-pr} (per pair)
complementary	ReviewPending	{skill: "prj-review", mode: null}	prj/overlap:depends-on-{older-pr} (per pair)
independent only	ReviewPending	{skill: "prj-review", mode: null}	none

Severity order: redundant > conflicting > complementary > independent.

If verdict is conflicting and the target PR is older than its counterpart (by phase_entered_at ascending, fallback to PR number ascending), the OTHER PR moves to Blocked instead, with blocking_on set to the target. Either way, the script also sets blocking_on on the blocked PR.

For complementary pairs, older_pr is the lower PR number tiebroken by earlier phase_entered_at. The label encodes the dependency direction: the newer PR carries prj/overlap:depends-on-{older-pr-number}.

complementary verdicts also append a one-line note to the target PR's cache at prs/{n}/overlap-notes.md so the daily report can surface the merge-ordering recommendation.

Architecture

Concern	Lives in
Shared state I/O (atomic load, save, runlog)	state_io (imported from prj-orchestrator/scripts)
File overlap computation + gh pr diff --name-only calls	scripts/overlap_scan.py
Label application + report rendering + phase transitions	scripts/verdict_io.py
Orchestration: config, scan, verdict persist, runlog	scripts/run.py
Semantic-compare prompt (LLM input)	assets/prompt-semantic-compare.md

The script split keeps each module narrow and independently testable. run.py itself is mostly argument routing. The semantic comparison is the LLM's job, not Python's: the prompt asset is the contract.

State and Cache Touched

This skill writes to:

• {project-root}/_bmad-output/pr-workflow/state.json (via state_io.save_state, atomic)
• {project-root}/_bmad-output/pr-workflow/prs/{pr_number}/overlap.md (overwritten each run)
• {project-root}/_bmad-output/pr-workflow/prs/{pr_number}/overlap-notes.md (append-only, complementary pairs only)
• {project-root}/_bmad-output/pr-workflow/logs/{YYYY-MM-DD}.jsonl (append-only run-log)
• GitHub: prj/overlap:* labels per the verdict aggregation table

This skill reads from:

• {project-root}/_bmad/config.toml (config)
• {project-root}/_bmad-output/pr-workflow/state.json (prior queue state; finds all other open PRs)
• GitHub via gh pr diff --name-only (changed-file lists for target and every other open PR)

Non-Negotiables

• Compare against ALL other open PRs. Not just recent ones. Stale PR overlaps must be detected.
• 2+ shared files triggers semantic compare. No skipping the LLM step when the threshold is hit.
• Conservative verdicts. When the comparison is ambiguous, pick independent. redundant requires near-identical intent on near-identical files.
• Atomic state writes. Always via state_io.save_state. Direct file writes to state.json are forbidden.
• Idempotent persistence. Rerunning with the same inputs produces the same state. overlap.md is overwritten; overlap-notes.md appends.

Verification

Smoke-test the scan step (requires gh auth, reads target PR's changed files):

python3 scripts/run.py --pr-number 82 --scan --verbose

Expected: exit 0, JSON on stdout with pairs array, no state changes.

Then exercise verdict persistence in dry-run mode (no gh, no state writes):

python3 scripts/run.py --pr-number 82 --verdicts-json '{"81": "complementary"}' --dry-run --verbose

Expected: exit 0, run-log entry with status: "dry-run", no state changes, no label applied, no overlap.md written.

Run the unit tests (no gh calls; all subprocess invocations mocked):

python3 -m unittest discover scripts/tests