reverse-engineering-anything/docs/verification/javascript-precision-calibration.md

JavaScript primitive-budget calibration — 2026-11-09

Keep the existing semantic precision defaults. A narrow real-source comparison found no additional required facts when doubling primitive_bytes; it does not justify a global increase or replacing the existing conservative admission rule. The input contract now explains that rule, and its list of defaults derives from the policy owner instead of repeating independent literals.

What was checked

Two inert directories went through the actual compiled analyze-javascript-application CLI, including its isolated source worker, complete Evidence serialization and normal CLI cleanup:

• An original theme.ts embedded in the pinned Actual Budget Theme source map. The required task recovers all 237 literal CSS property/value pairs and their source identity. A separate Python parser accepts only the complete literal-only declaration and checks every name/value without using REA's evaluator. A small package descriptor constructs the analysis directory; this is one captured module, not the complete application or an authenticated browser capture.
• The installed locked ms 2.1.3 package's original index.js and package descriptor. The requested small control recovers its s = 1000 millisecond base unit. Multiplication-derived coefficients remain unsupported and unknown; larger byte admission does not implement arithmetic or prove those values.

Input URLs/digests, a portable preparation/oracle script, CLI task driver and all twelve compact numeric receipts are in the calibration assets. No downloaded code or complete large replies are committed. The theme original source SHA-256 is 05307dc6f927705a8c76e43579c910bf6415ce28b375eea19251dc51dd2b1726.

Results

Three fresh CLI/worker trials per case compare omitted precision with explicit semantic_precision: {"primitive_bytes": 2097152}. Both requests hold the worker and CLI host old-space allowance at 512 MiB. Each task makes one analysis call, with no retries. All twelve exit successfully, verify the required facts and leave the observer's process group empty. Theme has no semantic unknowns; ms keeps the same 133 unrelated unknowns in both variants. This is complete coverage of the requested facts, not complete semantic understanding of ms.

Task / allowance	Required facts	Estimated CLI task tokens	Wall s	CPU s	Sampled host-group RSS MiB
Theme / default 1 MiB	237	259,396	0.937	1.226	330.6
Theme / explicit 2 MiB	237	259,475	0.928	1.229	330.8
ms base unit / default 1 MiB	1	234,613	0.899	1.238	322.2
ms base unit / explicit 2 MiB	1	234,668	0.905	1.225	330.5

Values are medians of three serial trials, in fixed default-then-double order. Node 24.22.1 ran on macOS 26.3 arm64; OS caches were not flushed. Mixed small timing/memory differences do not establish a performance improvement.

Token estimates use tiktoken 0.12.0 cl100k_base: compact Unicode JSON of the actual argv and complete parsed stdout Evidence, plus literal progress stderr. The full complete replies are about 734 KB for Theme and 624 KB for ms. This measurement includes the CLI entrypoint, worker, serialized output, and the driver's correctness checks. It excludes artifact acquisition, one-off oracle preparation, tokenizer computation, MCP discovery/protocol, chat framing and model reasoning. These are not billed model tokens or a claim that full output is an efficient agent workflow; existing retained summary/views can change delivery independently of evaluator precision. Replays with other path spellings can have different tokens and identities.

CPU is OS wait4 user+system usage of the waited subtree; sampler work and unwaited descendants are excluded. RSS sums the host process group every 20 ms: short peaks may be missed and shared pages counted more than once. The isolated JavaScript worker launches into another process group, so its peak memory is unmeasured here. The table is not total process-family peak memory. The observer's 1536 MiB early-stop guard is not a kernel hard limit; its 90-second deadline was not reached. Worker old-space flags are also not whole-process memory limits. Compiled entrypoint and owner hashes are retained because HEAD e2a2ede5440df396e44b3406ef511a31a680290e alone does not identify the measured uncommitted runtime. Portable scripts revise path handling after measurement without changing the requested facts; original driver/oracle hashes are retained.

Why retain the conservative rule

primitive_bytes charges six estimated JSON bytes per UTF-16 code unit plus quotes, before creating concatenations. At the 1 MiB default, 174,762 ASCII units fit and one additional unit exhausts that estimate, even though actual ASCII JSON occupies far fewer bytes. Control characters and lone surrogates can need six escaped bytes, so this is a conservative precision/resource policy rather than an assertion about observed encoded bytes. Existing regressions retain the boundary and exact exhausted-control recovery.

A bounded Babel inventory of the pinned generated Theme, main and DateSelect scripts found their longest static strings/templates to be 152, 936 and 13,120 UTF-16 units respectively. This inventory is not full semantic analysis and does not bound dynamically composed values or candidate cross-products. It nevertheless supplies no representative case requiring a higher string default.

Exact preallocation accounting would need to inspect string contents across every candidate concatenation, including pairs formed across piece boundaries, while preserving work bounds. Without an observed task failing this estimate, that added work and complexity are unjustified. The 256-candidate, 512-state and other depth/work defaults remain provisional: these two tasks do not establish their suitability for large unions, getters, aliases or adversarial sources.

Reproduce

Download the pinned Theme map URL from manifest.json to external storage, use the pinned Node toolchain and installed locked dependencies, then run:

REA_JS_REPO=/absolute/path/to/rea
REA_JS_NODE=/absolute/path/to/node24
REA_JS_DATA=/absolute/path/to/external-receipts
REA_JS_ASSETS="$REA_JS_REPO/scripts/verify/analysis/javascript-precision-calibration"
python3 "$REA_JS_ASSETS/prepare.py" "$REA_JS_REPO" /absolute/path/to/theme.js.map "$REA_JS_DATA"
for trial in 1 2 3; do
  for task in theme ms; do
    for budget in default double; do
      python3 "$REA_JS_REPO/scripts/verify/analysis/budget-calibration-run.py" \
        --output "$REA_JS_DATA/r${trial}-${task}-${budget}.metrics.json" \
        --cwd "$REA_JS_REPO" --timeout-seconds 90 --memory-mib 1536 -- \
        python3 "$REA_JS_ASSETS/task.py" "$REA_JS_REPO" "$REA_JS_NODE" \
        "$REA_JS_DATA" "$task" "$budget" "$REA_JS_DATA/r${trial}-${task}-${budget}.replies.json"
    done
  done
done
python3 "$REA_JS_ASSETS/aggregate.py" "$REA_JS_DATA" "$REA_JS_DATA/aggregate.json"

aggregate.py needs the separately installed tokenizer version above. These scripts neither install dependencies nor change host/provider configuration. Later checkouts are new measurements even when target hashes still match.