rea/docs/website-module-trace.md

Captured website module relationships

trace_web_module_imports / rea trace-web-module-imports traces one script's outgoing native ES imports and re-exports from an exported capture. It verifies the selected source's SHA-256 and byte count, preserves browser URL identities, and returns every matching capture candidate inline. It does not refetch website assets.

Select the source and context

Provide a caller-supplied Chromium executable supporting import.meta.resolve. REA does not install or upgrade a browser. Real verification covers Linux x64; other hosts have not received this feature's real workflow verification.

REA_BROWSER_EXECUTABLE=/absolute/path/to/chrome \
  rea trace-web-module-imports /analysis/export/manifest.json 0 \
  --importer-url 'https://example.test/app/main.js?build=2#entry' \
  --import-map-path /analysis/import-map.json \
  --import-map-base-url https://example.test/maps/ \
  --json

The MCP input expresses the same choices:

{
  "manifest_path": "/analysis/export/manifest.json",
  "script_index": 0,
  "importer_url": "https://example.test/app/main.js?build=2#entry",
  "import_map": {
    "path": "/analysis/import-map.json",
    "base_url": "https://example.test/maps/"
  }
}

script_index is zero-based in manifest.scripts. If importer_url is omitted, the trace selects the reported source URL. An inline script's document base cannot be established from that URL alone; choose the context explicitly when known. import_map is optional and reads local JSON only. Its exact bytes and base URL are retained; selecting it does not prove the map was installed in the captured page. HTTP(S) importer contexts without URL userinfo are supported initially.

Interpret the evidence

• Static imports, re-exports and literal dynamic imports receive the native engine's resolved URL or exact rejection message. Empty strings are retained.
• Computed dynamic imports retain their expression and source positions with computed-specifier unknown resolution. Erased type-only imports/exports and inferred bundler IDs are excluded from native import claims.
• Locations use UTF-16 offsets and columns, with one-based lines. Parse recovery diagnostics and unparseable input are explicit.
• Query variants and fragments remain distinct. An exact reported URL is an exact-reported-url candidate. A response URL stripped of its fragment is a weaker response-url-without-fragment content candidate. Multiple captured versions are all returned; the trace selects none as canonical.
• Candidate metadata remains reported capture evidence; only the selected source's bytes are reverified. Missing/lazy targets can resolve successfully with no captured candidate. Every relationship reports execution as unknown.
• Source-map declarations remain declarations; this operation does not read or invent map bytes, original-source mappings, worker ownership or UI causality.

The selected source is loaded from files/ under the manifest's current directory. Relocation retains the manifest's originally reported paths and the actual current source path separately. Unsafe paths, symlink source directories, nonregular files, wrong digests/sizes and malformed UTF-8 fail explicitly.

Engine and lifecycle

An owned temporary browser context runs REA's trusted resolver stub. The selected application is parsed as data and is never executed by this trace. Page requests are fulfilled with REA's synthetic document/stub or blocked; no website asset is downloaded. This does not establish an OS sandbox or browser-wide network containment. The engine version and native report are retained in Evidence.

Sources without literal imports do not acquire a browser. The manifest, source and import map have 32 MiB, 16 MiB and 4 MiB input limits. Native resolution has one 20-second deadline; cleanup may extend that deadline. One renderer is requested, and there is no aggregate host memory-limit claim. Cancellation closes only the owned browser; cleanup failure cannot return a successful trace. REA_BROWSER_NO_SANDBOX=true passes Chromium's corresponding launch option when the host requires it; it does not enable an REA security boundary.

See testing for the native loading oracle and CLI/MCP real lane.