Reverse Engineer

Reverse-engineer an external system into two things: a mechanically-verifiable teardown (feature inventory + registry + specs, optionally a security audit) and a steal-map — what to adopt into our surfaces, what to leave behind. The teardown is the evidence; the steal-map is the decision. Separating them works because a decision row that must cite a registry entry can be re-checked by anyone, while a decision made from impressions cannot be re-checked by its own author. The original failure mode this skill exists to prevent: reading a competitor's README and "deciding" from vibes.

Triggers: "reverse-engineer X", "tear down Y", "what should we steal from Z", "evaluate competitor/upstream", "should we fork/adopt/build-native".

⚠️ Constraints — Hard Guardrails (MANDATORY)

• Only operate on code/binaries you own or have explicit written authorization to analyze — this matters because unauthorized teardown is the legal/IP line.
• Do not provide steps to bypass protections/ToS or to extract proprietary source/system prompts.
• Do not output reconstructed proprietary source or embedded prompts (index only; redact in reports) — to prevent reproducing protected IP.
• Redact secrets/tokens/keys if encountered; run the secret-scan gate over outputs to prevent credential leakage.
• Always separate docs say vs code proves vs hosted/control-plane.

Phase 1 — Mechanical teardown (the script)

Produce evidence, not vibes. The script clones (pinned), scans CLI/config/artifact surface, and writes a feature inventory + machine-checkable registry + spec set.

bash
python3 skills/reverse-engineer/scripts/reverse_engineer.py <product> --mode=repo \
  --upstream-repo="https://github.com/org/repo.git" --upstream-ref=v1.0.0 \
  --output-dir=".agents/scratch/reverse-engineer/<product>/"

Binary mode requires --authorized (see Invocation Contract + Self-Test). Use the bundled demo fixture if you lack authorization for a real binary.

Phase 2 — The steal-map (the decision)

Map each capability the teardown found onto our surfaces. This is the part that turns research into a decision. Emit .agents/scratch/reverse-engineer/<product>/steal-map.md with a table; every row cites the teardown evidence and the matching surface in our repo.

| Their capability | Our surface today | Verdict | |---|---|---| | <feature> | <our file / skill / CLI, or "none"> | have / gap / steal / park / reject |

Verdict rules (hard-won — apply them, do not skip):

• steal — we lack it and it advances our core. Steal the pattern, not the storage engine: re-express in our primitives, never vendor their runtime.
• park — real, but it's substrate we deliberately delegate (e.g. orchestration per ADR-0009) or downstream of an unproven bet. Name it, don't build it.
• reject — it conflicts with our doctrine (e.g. a self-reported completion edge where we require a verdict — "no verdict = not done").
• have — we already do this; confirm it still holds, move on.
• gap — we should have it and don't. These are the steal candidates.

Discipline that makes the map trustworthy:

• Independently checked, not self-report. Get facts on how they implement

each capability from code, cross-checked by a fresh reader — never from a README or one context's summary. Model family is optional metadata, not a trust requirement.

• Probe the real state, don't argue from stale. Re-verify our side against the live tree before calling something a gap; every "X is missing" carries the search that proved it.
• The steal is the pattern, not the platform. Their robustness is usually one idea (unification, a gate, a reconcile loop). Steal the idea; leave the scaffolding.

Route one-way-door adoptions into planning

If adopting a steal is a one-way door (an architecture fork, a new bounded context, or a migration), do not decide it here. Hand the steal-map to Plan. Dueling Idea Genies or Premortem may challenge the choice as advisory evidence. Plan alone shapes the selected option in the existing intent source; neither strategy grants readiness or continuation authority.

Invocation Contract

Required: product_name. Common flags: --mode=repo|binary|both, --upstream-repo, --upstream-ref (pins the clone to a specific commit/tag/branch; the resolved SHA is recorded in clone-metadata.json on any clone), --output-dir (default .agents/scratch/reverse-engineer/<product>/), --security-audit, --materialize-archives (authorized-only opt-in; embedded-archive extraction is off/index-only by default), --authorized (mandatory for binary mode — refuses without it). Full list: python3 skills/reverse-engineer/scripts/reverse_engineer.py --help.

Output Specification

Phase-1 teardown under output_dir/: feature-inventory.md, feature-registry.yaml, feature-catalog.md, spec-architecture.md, spec-code-map.md, spec-clone-vs-use.md, spec-clone-mvp.md, plus spec-cli-surface.md only when a CLI is detected and clone-metadata.json only when the script performs a clone (i.e., --upstream-repo is supplied and the target is not already checked out); --upstream-ref pins which commit, it is not what triggers the file. Security mode adds output_dir/security/: threat-model.md, attack-surface.md, dataflow.md, crypto-review.md, authn-authz.md, findings.md, reproducibility.md, validate-security-audit.sh. Phase-2: steal-map.md.

• Artifact directory: the exact --output-dir, defaulting to

$REPO/.agents/scratch/reverse-engineer/<product>/.

• Filename convention: the fixed phase-1 and phase-2 names above; security

files live only in the security/ child directory.

• Serialization/schema format: registry is YAML, clone metadata is one JSON

object, and inventories/specs/steal-map are nonempty Markdown files.

• Validator command: with $output_dir, $security_audit, $sbom, and

$upstream_ref_set (each flag 0|1) set:

bash set -euo pipefail required=(feature-inventory.md feature-registry.yaml feature-catalog.md spec-architecture.md spec-code-map.md spec-clone-vs-use.md spec-clone-mvp.md analysis-root-path.txt validate-feature-registry.py steal-map.md) for name in "${required[@]}"; do test -f "$output_dir/$name" test ! -L "$output_dir/$name" test -s "$output_dir/$name" done test -f "$output_dir/docs-features.txt" test ! -L "$output_dir/docs-features.txt" test ! -L "$output_dir/spec-cli-surface.md" if [[ -e "$output_dir/spec-cli-surface.md" ]]; then test -f "$output_dir/spec-cli-surface.md" test -s "$output_dir/spec-cli-surface.md" fi python3 "$output_dir/validate-feature-registry.py" if [[ "$upstream_ref_set" == 1 ]]; then test -f "$output_dir/clone-metadata.json" test ! -L "$output_dir/clone-metadata.json" jq -e 'type == "object"' "$output_dir/clone-metadata.json" >/dev/null else [[ "$upstream_ref_set" == 0 ]] fi grep -Fqx '| Their capability | Our surface today | Verdict |' "$output_dir/steal-map.md" if [[ "$security_audit" == 1 ]]; then test -x "$output_dir/security/validate-security-audit.sh" if [[ "$sbom" == 1 ]]; then "$output_dir/security/validate-security-audit.sh" "$output_dir" --sbom else [[ "$sbom" == 0 ]] "$output_dir/security/validate-security-audit.sh" "$output_dir" --no-sbom fi else [[ "$security_audit" == 0 ]] [[ "$sbom" == 0 ]] fi

• Downstream handoff: give the validated steal-map.md to Plan for

one-way-door candidates; ordinary have, park, and reject decisions remain evidence-backed terminal rows.

Reproducibility + fixtures

--upstream-ref pins the clone (fetch FETCH_HEAD, record SHA) so contracts can be committed as golden fixtures and diffed across runs. Regression test: bash skills/reverse-engineer/scripts/repo_fixture_test.sh. To update a fixture when contracts legitimately change, re-run with the new pinned ref, copy the contract files into fixtures/<product>/, and commit.

Self-Test (acceptance)

bash
bash skills/reverse-engineer/scripts/self_test.sh

Must show: feature inventory generated, registry generated, registry validator exits 0; in security mode validate-security-audit.sh exits 0 and the secret scan passes.

Examples

Reverse-engineer an OSS CLI (repo mode) → steal-map

Run the skill for cc-sdd with --mode=repo --upstream-repo="https://github.com/gotalab/cc-sdd.git" --upstream-ref=v1.0.0. It clones the pinned source, scans the surface, writes inventory/registry/specs, and maps each feature onto our surfaces (have, gap, steal, park, or reject) in steal-map.md. Supply selected steals to Plan.

Binary analysis with security audit

Run the skill for ao with --authorized --mode=binary --binary-path="$(command -v ao)" --security-audit. It performs authorized static analysis plus the security suite under output_dir/security/; the secret-scan check must pass.

Troubleshooting

| Problem | Cause | Solution | |---|---|---| | Refuses binary analysis | Missing --authorized | Add --authorized (explicit written authorization required). | | No clone-metadata.json | --upstream-repo not passed | Pass --upstream-repo (and optionally --upstream-ref). | | Fixture diff fails | Upstream changed / stale golden | Re-run pinned, refresh fixtures/, commit. | | spec-cli-surface.md missing | No Node/Python/Go CLI detected | Surface is documented in spec-code-map.md instead. | | Steal-map is all "steal" | Skipped the park/reject rules | Substrate we delegate is park; doctrine conflicts are reject — not everything novel is worth adopting. |

Quality Rubric

• ] Every steal-map row cites teardown evidence and our matching surface (or "none").
• ] Verdicts use the full set — have/gap/steal/park/reject — not everything marked "steal".
• ] Facts on how they implement come from code and a fresh independent check — not a README.
• ] One-way-door adoptions are supplied to Plan, not decided here.
• ] Secret-scan gate passed over all outputs; no proprietary source/prompts reproduced.

See Also

• plan — shape selected steals in the existing intent source
• idea-genie — optional advisory challenge (duel mode)
• premortem — optional advisory challenge of the exact plan
• research — general exploration; this is its external-system specialization

Reference Documents

• references/reverse-engineer.feature — executable spec: repo-mode feature catalog + code map, binary-mode security audit, durable spec artifacts