rea/docs/javascript-recovery.md

JavaScript source recovery

recover_javascript_sources / recover-javascript-sources derives readable modules from explicitly selected UTF-8 JavaScript files or bundles. Use it on files returned by export_web_scripts or other local scripts. The operation never executes the selected or recovered application code.

Caller-supplied engine

REA accepts Wakaru ^1.13.0 on Linux x64. The report parser is verified with Wakaru 1.14.0. Another release in that range is accepted, the observed version is reported, and a limitation records that the parser was not verified against that release. Wakaru changes --version, --json and provenance.json only by addition within a major version (compatibility policy), so the parser keeps unknown report fields and reported module statuses.

Set REA_WAKARU_COMMAND to the absolute path of an executable supplied by the caller. The adapter uses util-linux prlimit (default /usr/bin/prlimit; override with an absolute REA_JAVASCRIPT_PRLIMIT_COMMAND). REA does not install either tool. Engine configuration is checked only when recovery is requested; other REA capabilities remain available without it.

Unmodified upstream source is retained in third_party/wakaru, pinned to 8219bf5016a063d7fb215101a8c45d5959ec733f (v1.14.0, Apache-2.0). The result reports the executed binary's exact path, SHA-256 and observed version. The audited source revision is distinct from executed_source_revision: null: a version string cannot prove which source produced a caller-supplied binary.

Install Wakaru

Use the official release binary, the same one CI verifies:

curl -fL https://github.com/pionxzh/wakaru/releases/download/v1.14.0/wakaru-linux-x64.tar.gz | tar -xz wakaru
export REA_WAKARU_COMMAND="$PWD/wakaru"

Or install it from npm. Point at the platform binary, not the Node.js shim in node_modules/.bin:

npm install wakaru@1.14.0
export REA_WAKARU_COMMAND="$(realpath node_modules/@wakaru/cli-linux-x64/wakaru)"

Both give the same binary (SHA-256 664fa06782a61eda7ed15885134b52525fd565dd77607e642062ceb6cd927c38).

Recover and analyze

rea recover-javascript-sources /tmp/web-scripts/app.js /tmp/recovered-app --json
rea analyze-javascript-application /tmp/recovered-app/modules --json

# Recover related code-split chunks together; repeat --additional-path.
rea recover-javascript-sources /tmp/web-scripts/main.js /tmp/recovered-chunks \
  --additional-path /tmp/web-scripts/runtime.js \
  --additional-path /tmp/web-scripts/shared.js \
  --additional-path /tmp/web-scripts/checkout.chunk.js --json

MCP input:

{
  "path": "/tmp/web-scripts/main.js",
  "additional_paths": [
    "/tmp/web-scripts/runtime.js",
    "/tmp/web-scripts/shared.js",
    "/tmp/web-scripts/checkout.chunk.js"
  ],
  "output_directory": "/tmp/recovered-chunks"
}

The output directory must be absent, absolute, and have an existing parent. Each source is snapshotted separately in a private workspace. Multiple inputs retain their relative directory layout and are passed together to one Wakaru invocation, allowing cross-chunk module IDs to resolve. Inputs must be distinct; additional_paths accepts up to 16 additional files. The engine writes only to its own staging directory. Reported module paths, input identities, UTF-8 byte ranges, regular files and emitted map representations are validated before publication. REA writes verified bytes to an exclusively owned output tree and rolls it back on failure. It also checks that the original source and engine bytes remain unchanged before committing. The existing output is never overwritten.

Multi-input relative filenames must be representable unchanged as artifact paths: NFC Unicode spelling and no literal backslashes. Unsupported layouts fail before invoking the engine rather than silently renaming inputs referenced by source maps.

Published contents:

• inputs/bundle.js: exact original snapshot for a single input. Multiple inputs retain paths relative to their common parent under inputs/.
• modules/: derived modules and any upstream-emitted source maps.
• reports/stdout.json and reports/provenance.json: exact producer reports.
• manifest.json: identities, modules, transform choices, warnings and limitations.

The inline result includes complete file paths/digests/sizes, extraction ranges, warnings and analysis_input, directly usable as the arguments to analyze_javascript_application. source identifies the primary input and binds the Evidence subject; additional_sources records the other snapshots and their published copies when selected. Each module names its owning snapshot, original path and original digest; all extraction and context ranges refer to that input. Raw Evidence retains selected command arguments, reported input paths, exit status, stderr and reports; temporary paths are recorded as historical execution coordinates after their workspace is removed.

Transform choices and interpretation

extraction_mode defaults to structural (Wakaru --unpack=strict). heuristic uses --unpack=auto; inspection uses --unpack=inspect and can return finer, non-executable regions. rewrite_level accepts minimal, standard (default) and aggressive. Maps and provenance are requested in every operation.

Structural extraction can fall back to a single file. In the real fixtures, webpack 5 yields two modules; the esbuild scope-hoisted fixture remains one unknown-format script. Returned module counts and detected formats report those actual outcomes. A valid report with failed transformations returns partial with original warnings and files. An unusable report, inconsistent provenance, escaping path, symlink or missing module is an error, with owned cleanup.

Evidence confidence is derived. Extraction ranges are half-open UTF-8 byte offsets in the original snapshot, rather than rewritten line positions or a coverage assertion. Source maps are preserved without claiming independently verified mapping accuracy. Original variable names and arbitrary runtime equivalence remain unknown. No network fetching occurs.

Resource policy and verification

Each operation uses one worker, a 1 GiB address-space ceiling and a 120000 ms deadline. That deadline has no runtime override: raising analysis_timeout_ms or max_heap_mb does not raise it. An unchanged retry may hit the deadline again. The operation accepts up to 64 MiB of total input across all selected files and 128 MiB/10000 entries of staged output, with 8 MiB per diagnostic/report stream. A provenance.json over that report allowance names the fixed limit: this release has no runtime override, and raising max_heap_mb or analysis_timeout_ms does not raise it. Malformed reports stay distinct from that size refusal. Exceeding a limit is an explicit failure with rollback. Selected inputs beyond the total input allowance return a non-retryable resource_constraint with resource: "file-size" and reported_limits.maximum_input_bytes/remaining_input_bytes; input that is not valid UTF-8 is an invalid_format request issue. These limits apply per operation and do not claim aggregate host containment across concurrent callers.

See testing.md for the focused real Wakaru CLI/MCP lane and its source-owned compiler fixtures. Other host platforms and Bun/Vue recovery are not claimed by this adapter.