JS Reverse Ops

Use this skill as a structured reverse-engineering workflow, not an ad hoc debugging session.

When NOT to Use

Do NOT use this skill for:

• writing new crawlers or scrapers from scratch (no reverse-engineering objective)
• general frontend development, framework debugging, or performance tuning
• binary / APK / iOS / firmware reverse engineering (use a binary-RE skill)
• log/disk forensics or standalone crypto challenges (unless reversing the implementation is the actual blocker)
• pure network-protocol analysis without a JavaScript component

When in doubt, triage first (node scripts/js_reverse_ops.js <target> --json) and let the router say whether this skill owns the task.

Start Here

1. NOW: classify the request (signature recovery, offline deobfuscation, runtime tracing, environment rebuild, ...) and load only the referenced files for that task type.
2. NOW: if the work involves running browser JS locally, read references/env-rebuild-recipes.md first — 10 recipe cards (native-masked classes, class-tag probes, no-host-builtins, real timers, inline proxy, calibration oracles) that prevent the most expensive sandbox mistakes.
3. NOW: if dependencies or tooling are in doubt, follow references/toolchain-bootstrap.md before writing probes.
4. NEXT: if a rebuilt flow "almost works" (valid first token, later failures, 200-but-wrong-answers, unexplained key divergence), stop probing and read references/misdiagnosis-patterns.md.
5. ACT: enter the matching stage of the Core Workflow and execute — do not stop at confirmation.

Scope

This public release keeps:

• stage-based routing for Locate, Runtime, Recover, and Replay
• reusable scripts for extraction, runtime capture normalization, replay scaffolding, and artifact generation
• generic references, rules, and templates for browser-driven JavaScript reverse engineering

This public release intentionally excludes:

• private or site-specific case libraries
• captured test fixtures and validation corpora
• concrete benchmark targets, credentials, and replay notes tied to named sites

Core Workflow

Start from the smallest reliable context:

• unknown target: run node scripts/js_reverse_ops.js <target-url-or-file> [--json]
• existing notes, hook logs, or failure summaries: run node scripts/map_case_to_pattern.js <notes.md> and pass --notes <notes.md> to scripts/js_reverse_ops.js
• actionable playbook run: run node scripts/run_playbook.js <target> --notes <notes.md> --out runs/current to emit a runbook, route plan, bootstrap claim/provenance/risk/replay artifacts, and hook scaffold
• next operator command: run node scripts/recommend_next_action.js runs/current --json when a run directory exists but runtime, replay, or readiness blockers make the next step unclear
• local JS or HTML target: run scripts/triage_js.sh <path> and then the smallest extractor that matches the target family
• browser-backed target: verify browser and bridge health before collecting runtime evidence
• anti-analysis symptoms: run node scripts/select_anti_detection_profile.js --symptoms "<symptoms>" before changing hook or browser strategy; profile selection changes observation strategy only and must still be followed by runtime/replay verification
• public quality check: run node scripts/run_public_benchmarks.js before publishing or after changing router, pattern memory, examples, or playbooks
• public release risk audit: run node scripts/explain_public_release_risk.js --json --strict to explain tracked-file, secret, path, capture, and generated-artifact risk before pushing
• public capability summary: run node scripts/generate_capability_scorecard.js when comparing this skill against other reverse-engineering packages
• market-gap summary: run node scripts/generate_market_gap_scorecard.js when deciding how to improve this skill against advanced reverse-engineering skills and MCP toolchains
• external regression matrix: run node scripts/compare_external_skill_matrix.js --json to compare this skill against browser MCP, static decompiler, agentic JS reverse, and cross-domain RE profiles
• browser MCP smoke planning: run node scripts/plan_browser_mcp_smoke.js --server-family chrome_devtools_mcp --json before executing adapter-specific browser smoke checks
• browser MCP smoke verification: run node scripts/verify_browser_mcp_smoke_record.js --record <mcp-execution.json> --json before claiming adapter smoke observations
• browser MCP delivery loop: run node scripts/run_mcp_delivery_loop.js <target> --record <mcp-execution.json> --out runs/current --json to scaffold, verify, promote, validate, and assess readiness in one pass
• replay failure diagnosis: run node scripts/diagnose_replay_failure.js --run-dir runs/current --json or pass --replay-record <record.json> before changing signer code
• replay client generation: run node scripts/generate_replay_delivery_client.js --record <accepted-replay.json> --out runs/current/replay-client --json to produce sanitized Node and Python replay clients
• replay client validation: run node scripts/validate_replay_delivery_client.js runs/current/replay-client --json before treating generated clients as handoff artifacts
• static truth gate: run node scripts/assess_static_recovery_truth.js --original <input.js> --recovered <output.js> --json before promoting readable static output
• source-map-first static planning: if a bundle has sourceMappingURL, sourceURL, inline maps, or X-SourceMap notes, run node scripts/plan_static_toolchain.js <bundle.js> --json before AST cleanup
• domain handoff validation: run node scripts/validate_domain_handoff_record.js --record <handoff-record.json> --json --strict before merging WASM, packet, mobile, native, or debugger findings back into JS evidence
• CLI wrapper: use node scripts/jsro.js <command> or the jsro package bin for route, run, validate, next, benchmark, scorecard, marketgap, releaserisk, externalmatrix, mcpsmoke, mcpsmokeverify, mcploop, replaydiagnose, replayclient, replayclientcheck, statictruth, handoff, handoffcheck, install, and publish commands
• one-command install or release: use bash scripts/install_local.sh and bash scripts/publish_release.sh

• accepted response plus confusing browser-visible values: inspect page-side render and suppression logic before escalating into signer recovery, and use playbooks/accepted-response-hidden-dom.md
• accepted response plus page-local embedded font or glyph entities: extract the current response font, solve the glyph map at page scope, and use playbooks/embedded-runtime-font-mapping.md
• replay still fails even after one accepted digest is recovered: inspect bootstrap-time cookie write order, digest collectors, and wrapped-cookie assembly, then use playbooks/bootstrap-digest-ladder.md
• one endpoint keeps returning JavaScript first and only returns arrays after the script is executed and replayed against the same path: treat it as an iterative warmup chain instead of hunting for a second hidden endpoint, and use playbooks/iterative-script-warmup-same-endpoint.md
• signer depends on one server-issued time and one wasm or module helper: freeze the time source, prove the exact signer input shape, and use playbooks/server-time-gated-wasm-signer.md
• digest helper name looks standard, but browser output diverges from both the standard library and the raw local helper: isolate the smallest runtime patch surface first, and use playbooks/patched-runtime-digest-branch.md
• one large bundle hides a tiny runtime helper you actually need for replay: extract that helper first instead of emulating the whole page, and use playbooks/runtime-bundle-signer-extraction.md
• global token helpers are absent or misleading, but XMLHttpRequest.open rewrites the protected URL with the signer field: treat the rewritten URL as the signer output, preserve script order and runtime state, and use playbooks/xhr-open-url-rewrite-runtime-replay.md
• visible request contract is stable but different HTTP clients diverge: escalate through a transport ladder before inventing more signer state, and use playbooks/transport-profile-ladder.md
• verify response looks noisy or pessimistic while data requests still succeed: treat the data endpoint as the acceptance oracle, and use playbooks/lenient-verify-data-gate.md
• page exposes one simple request or one helper field, but later pages fail with a token-shaped gate: prove whether the visible request is a decoy before widening into full VM recovery, and use playbooks/decoy-page-request-hidden-token-gate.md
• one challenge image is a fixed small grid with one glyph or symbol per cell: solve the grid-assignment path first, and use playbooks/grid-challenge-template-matching.md
• multi-stage challenge needs fresh reload, one seeded signer proof, and then uses one accepted stage value as the next key: validate the first baseline request before solving downstream decrypts, and use playbooks/fresh-reload-seeded-signer-step-key-ladder.md
• one replay path works for round one, but later rounds only regain parity after prior-round replay: preserve the explicit same-page round ladder, and use playbooks/same-page-prior-round-signer-replay.md
• desktop HTML is unstable but a mobile or app request profile lands on a shell page with later JSON hydration: recover the shell request wrapper and route map first, then use playbooks/mobile-shell-api-pivot.md
• For bundled crypto libraries whose primitives are environment-gated (browser versus sandbox branches, modified base64 alphabets or hash constants, sandbox tokens rejected while browser tokens pass), route to playbooks/env-gated-crypto-differential.md.
• For stateful VM signers whose captured token URLs replay successfully, route to playbooks/browser-assisted-token-replay.md before attempting VM semantic recovery.
• For custom-VM signers that need a browser-free local oracle, route to playbooks/jsdom-native-vm-differential.md and diff instruction and constant streams against one instrumented browser ground truth.
• For short-TTL tokens, route to playbooks/short-ttl-inline-proxy.md: send the real request from inside the token-computing harness via a Promise-based resource interceptor.

• packed or VM-like code: preserve the original artifact, recover structure incrementally, and label verified semantics
• replay handoff: export a stable artifact bundle before writing Node or Python delivery code

Best-Tool Baseline

Use built-in scripts for routing, evidence, artifacts, and repeatability. Use specialist tools only for the narrow job they are good at:

• source maps or original modules first, before any deobfuscation pass
• webcrack for common obfuscator.io, webpack-like bundles, string arrays, and first-pass unbundling
• wakaru for modern minified output where syntax normalization and readability matter more than runtime truth
• ast-grep, Babel, or recast for small targeted structural transforms
• humanify or another LLM renamer only after sanitizing code and only when identifier recovery is worth sending snippets outside the workspace

Do not let external deobfuscators replace evidence. Every recovered field, cookie, signer input, or replay helper still needs a verified browser observation or a local replay artifact.

For broader comparison against adjacent reverse-engineering skills and tools, use references/external-skill-comparison-2026-06-04.md.

Publication Safety Gate

Before publishing this public skill, run bash scripts/check_public_release.sh from the public repository root. The public package must not contain:

• private site notes, live captures, credentials, cookies, tokens, or customer-specific paths
• generated tmp/, cache, __pycache__, .pyc, or local benchmark output tracked by git
• absolute local user paths, bearer tokens, GitHub tokens, cloud keys, JWTs, or private keys
• unsanitized snippets that identify a live target beyond generic examples

Keep private corpora and local validation bundles in the private workspace. Publish only generic playbooks, scripts, templates, and sanitized examples.

Primary References

• references/env-rebuild-recipes.md
• references/misdiagnosis-patterns.md
• references/toolchain-bootstrap.md
• references/standard-workflow-cookbook.md
• references/stage-gates.md — hard entry/exit conditions, time-boxes, fallback chain
• references/decision-handoff.md — delta-only handoff protocol between stages/sessions
• references/task-types.md
• examples/case-walkthrough-combinatorial-gates.md — sanitized narrative: combinatorial env gates + calibration oracles
• examples/case-walkthrough-timer-selfcheck-and-fake-200s.md — sanitized narrative: timer self-checks, time-derived keys, 200-fake-data maze

Note: the verbatim-harness scaffolding generator referenced in the full edition is distributed with the private workspace only; this public package documents the equivalent rules in references/env-rebuild-recipes.md.

• references/stages/locate.md
• references/stages/runtime.md
• references/stages/recover.md
• references/stages/replay.md
• references/rules/evidence-rules.md
• references/rules/runtime-first.md
• references/rules/routing-rules.md
• references/rules/replay-rules.md

Publishing Note

This public variant is intended for sharing as a reusable skill package. Keep private fixtures, live captures, and customer- or site-specific notes in a separate private workspace or repository.