cpm-engine

An open-source CPM engine with AACE-aligned methodology and a published Daubert disclosure.

**Open source. AACE-aligned. Daubert-disclosed. 1,273 JS unit tests, plus JS/Python parity on 1009 of 1015 enumerated cross-validation comparisons; the remaining 6 are not compared because neither engine emits the field on a completed activity (see DAUBERT.md §3.1).**

Court-facing usage: pair this engine with the analyst-application discipline in `FORENSIC_USE_SOP.md`, the verification chain in `VERIFY_RELEASE.md`, the per-release receipts in `release-evidence/`, and the field-level P6 comparison framework in `validation/p6-comparison/`. Do NOT cite README in a court-facing report — cite the documents listed in DAUBERT.md and `FORENSIC_USE_SOP.md` §Required pairing.

Maintained by Critical Path Partners — a forensic-scheduling consultancy.

Quick start

The npm package lags this repository. npm `latest` is 2.9.19, published 2026-05-17 — that is the number the npm badge above renders, and nothing has been published to npm since, while 22 tagged releases have shipped here. `npm install cpp-cpm-engine` therefore does not give you the engine described by DAUBERT.md, by the `release-evidence/` packets, or by any version reference in these docs. Install from the git tag:

git clone https://github.com/danafitkowski/cpp-cpm-engine.git
cd cpp-cpm-engine
git checkout v2.9.43

The engine has zero runtime dependencies, so a clone is all it needs. This is the same install path `VERIFY_RELEASE.md` gives an opposing expert.

const E = require('./cpm-engine.js');

const result = E.computeCPM(
    [
        { code: 'A', duration_days: 5, early_start: '2026-01-05', clndr_id: 'MF' },
        { code: 'B', duration_days: 3, clndr_id: 'MF' },
        { code: 'C', duration_days: 4, clndr_id: 'MF' },
    ],
    [
        { from_code: 'A', to_code: 'B', type: 'FS', lag_days: 0 },
        { from_code: 'B', to_code: 'C', type: 'FS', lag_days: 0 },
    ],
    {
        dataDate: '2026-01-05',
        calMap: { MF: { work_days: [1, 2, 3, 4, 5], holidays: [] } },
    }
);

console.log('Project finish:', result.projectFinish);     // 2026-01-21
console.log('Critical path:', result.criticalCodesArray); // ['A', 'B', 'C']
console.log('Engine version:', result.manifest.engine_version); // 2.9.43

That's it. Forward pass, backward pass, total float, free float, calendar arithmetic, P6-conventional date math, multi-jurisdiction holidays — all done.

Why this engine?

*(Vendor comparison removed in the v2.9.33 audit cycle. Comparisons against specific commercial CPM tools should be supplied by an independent reviewer, not authored by the engine's maintainer.)*

The engine math is a commodity. What carries a forensic schedule analysis is the workflow, the methodology discipline, and the Daubert disclosure posture — not the forward pass itself. Critical Path Partners open-sources the engine so any academic, any solo forensic scheduler, any contractor's internal scheduler can build on a transparent, citable foundation.

What you can build

• Forensic delay analysis primitives — CPM forward/backward pass that supports analyses under AACE 29R-03 MIPs 3.3 (windows), 3.6/3.7 (prospective TIA single-base / multi-base), and 3.8 (collapsed as-built). The engine provides the CPM math; full method implementations (period selection, fragnet integration, as-built reconstruction) live in the CPP forensic skill suite — this OSS engine is the math core they build on, not the full method.
• Claim packages — owner-submission EOT bundles with cover letter, exhibits, mitigation logs
• Daubert disclosures — FRCP 26(a)(2)(B) reports, FRE 702/707 four-prong methodology statements
• Schedule risk primitives — Bayesian posterior estimation (`computeBayesianUpdate`); per-iteration CPM (`runCPM`) suitable as an inner loop for Monte Carlo wrappers built on top of this engine. Full Monte Carlo / QRAMM scoring lives in the CPP forensic skill suite (`schedule-risk-analysis`), built atop this primitive.
• Schedule health — DCMA-14 assessment, A-F auto-grade, baseline-vs-current diff
• Multi-jurisdiction calendars — 66 default holiday rule sets (CA-FED + 13 provinces/territories, US-FED + 50 states + DC). These are framework-aligned defaults sufficient for general-purpose date math — see `docs/jurisdictions.md` for the per-jurisdiction reference table and forensic-use verification guidance. They are not legally certified calendars; for forensic use, override with the project's contract calendar via `opts.calendar`.

AACE alignment

The engine implements the math behind these AACE Recommended Practices:

Method labels are emitted in `result.manifest.methodology` — exactly the strings AACE peer-reviewers and opposing experts expect.

Verifiable provenance

Every computation emits a manifest:

result.manifest = {
    engine_version: '2.9.43',
    method_id: 'computeCPM',
    activity_count: 3,
    relationship_count: 2,
    data_date: '2026-01-05',
    calendar_count: 1,
    computed_at: '2026-05-10T14:32:01.847Z',
}

Plus, for forensic provenance, every input carries a SHA-256 topology hash:

const hash = E.computeTopologyHash(activities, relationships);
console.log(hash.topology_hash);  // 64-char hex over canonical (code, duration, sorted preds + types + lags)
// Two XERs with identical hashes have IDENTICAL CANONICALIZED TOPOLOGY under the hashed-field
// set (activity codes, durations, predecessor links + types + lags). NOT a forensic-equivalence
// statement — different calendars, resources, WBS, names, or constraints can still produce
// different schedules under the same hash. The hash is a signal, not a schedule-equivalence proof.

This is the engine's network-topology fingerprint. Bid-collusion signal, retroactive-manipulation signal, and copy-detection signal across XERs all rely on it. It is also the foundation that lets opposing counsel verify topology-level integrity of a CPP analysis post-hoc — they can recompute the hash from the same XER and confirm the activity/relationship network was not altered between submission and review.

JavaScript - Python parity

The engine has a Python sibling (`_cpp_common/scripts/cpm.py`) used by every CPP forensic skill. The two implementations are kept bit-identical via cross-validation:

npm run crossval
# 46 fixtures, 1009 checks executed, 0 deviations, measured 2026-09-02.
# A further 6 comparisons on the enumerated surface (1015 total) are skipped rather than failed by the harness field guards, all on ff_signed / ff_signed_working_days on completed activities, where NEITHER engine emits the field.

Plus a 282-activity real-XER stress test reports 0 mismatches. That XER is a single non-public reference file, is not committed, and the run is not independently reproducible from this repo (see DAUBERT.md §2).

This means a forensic analysis run in JavaScript (browser, Node) produces the same numbers as one run in Python (claims-preparation skill, MCP server, batch pipeline). Every CPP deliverable carries the same manifest regardless of which surface produced it.

Independent verification

The same-author crossval is honest about its limit: both JS and Python implementations are maintained here. To close the Daubert "no independent testing" objection, the engine ships with a one-command third-party reproduction harness:

git clone https://github.com/danafitkowski/cpp-cpm-engine
cd cpp-cpm-engine
git checkout      # the SHA cited in the disclosure
npm run verify                # runs unit + crossval + citation tests
# → attestations/latest.json   ← machine-readable witness file

Engine has zero npm dependencies, so reproduction requires only Node 18+ and Python 3.10+. The witness file contains:

• Engine SHA-256 + Python-reference SHA-256
• Commit SHA + git ref + workflow URL (in CI)
• Test counts: unit-tests passed/failed, crossval fixtures + checks, citation regression status
• Timestamp + Node version + platform
• Verdict (PASS/FAIL)

Compare your locally-generated witness against the CI-signed witness (published on every push as a workflow artifact + Sigstore-signed via `actions/attest-build-provenance`). Bit-identical SHA-256s + matching pass counts on a clean clone = third-party reproduction confirmed.

Verify a signed CI attestation:

gh attestation verify attestations/latest.json --owner danafitkowski

See DAUBERT.md §3.1 — Independent Verification for the full Daubert framing.

Production use

The engine runs live at **mcp.criticalpathpartners.ca** — try it in your browser. The same `cpm-engine.js` file is served over the wire and embedded inline in every report CPP produces.

The CPP forensic suite (forensic-delay-analysis, claims-preparation, claim-workbench, time-impact-analysis, schedule-risk-analysis, collapsed-as-built, counter-claim-analysis) all consume this engine — the JS port for browser/MCP, the Python sibling for batch pipelines.

Citation

If you use this engine in academic work or expert-witness reports, please cite:

> Fitkowski, D. (2026). *cpm-engine: An open-source critical-path-method engine with AACE-canonical method labels and a published Daubert disclosure.* Critical Path Partners. Version 2.9.43.

Algorithm citations are in `docs/citations.md`. All citations have been verified against primary sources.

License

MIT — see LICENSE.

You can use this engine in commercial forensic consulting, in academic research, in your own scheduling product, in court-filed expert reports. Just keep the copyright notice. No support is implied; no warranty is provided. You are responsible for the conclusions you draw with the engine. A Daubert disclosure is built in (`DAUBERT.md`) — you may use it as a starting point for your own FRCP 26(a)(2)(B) report.

Release notes

v2.9.12 (2026-05-16) — Round 9 engine math fix wave. ~30 substantive math defects closed across four buckets: T1 constraint handling (MS_Start backward LF clamp, actual_start precedence over ES-side constraints per P6 forward-pass semantics, Section D Monte Carlo actual_start pinning, INFO task-dropped alerts, constraint-unrecognized / incomplete WARNs, CS_MANSTART/CS_MANFINISH aliases, Section D SNLT/FNLT/MS_Start violated+applied alerts); T2 calendar/lag arithmetic (calendar-aware Free Float on binding link, signed _countWorkDaysBetween, negative-FF preserved, dateToNum rollover guard, non-finite lag rejection, invalid-calendar-falling-back WARN, SUB_DAY_LAG_ROUNDED direction-bias disclosure); T3 in-progress + actuals (remaining_duration P6 retained-logic, backward LS=ES pin for in-progress, Section C EF>=ES guard, OoS enumerates every pred, hammock-orphan ALERT, hammock duration_working_days, unrecognized-task-type WARN); T4 Python parity (R8A-1 backport, ALAP secondary slot, forward ES gate). 792 unit tests / 416 crossval checks / verify PASS. See CHANGELOG.md for the full T1-T4 fix index.

v2.9.11 (2026-05-16) — Round 8 R8A engine math fix wave. Four T1 silent-wrong-answer paths closed: `actual_finish` without `actual_start` no longer collapses ES to EF; sub-day fractional lags emit `SUB_DAY_LAG_ROUNDED` ALERT; FF / SF Free Float uses the successor's calendar; Section D constraint clamps emit `constraint-skipped` WARN when `opts.projectStart` is missing.

v2.9.10 (2026-05-16) — Round 7-8 hardening. Independent-verification infrastructure (public CI on 9 OS × Node combos, Sigstore-signed witness JSONs, one-command local reproduction via `npm run verify`) ships as a tagged release. Engine math byte-identical to v2.9.9; that is a docs + infra release. See DAUBERT.md §3.1 and the new §10 Roadmap.

See CHANGELOG.md for the full release history through v2.9.43.

Contributing

See `CONTRIBUTING.md`. Forensic correctness is enforced — every commit must pass 1,273 unit tests and the cross-validation harness, in which 1009 of 1015 defined comparisons execute and are bit-identical with 0 failures across 46 fixtures (the remaining 6 are skipped rather than compared — 3 `ff_signed`, 3 `ff_signed_working_days`, all on completed activities where neither engine emits the field), plus the citation regression, truncation regression, and version-drift regression gates (all wired into `npm run test:all` and `npm run verify`). New citations require WebSearch-verified URLs. No fabricated case names. No LLM-generated narratives in core engine paths.

Companion repositories

Two companion repositories are public:

• **cpp-xer-parser** — the canonical Primavera P6 XER parser. The engine consumes its parse output as the canonical XER → JS-object layer; `cpp-xer-parser` has no dependency on this engine.
• **cpp-critical-path-validator** — critical path validation and DCMA-14 assessment. Optionally consumes this engine for the LPM cross-check; degrades gracefully when absent.

Additional CPP skills (forensic-delay-analysis, claims-preparation, claim-workbench, time-impact-analysis, collapsed-as-built, counter-claim-analysis, schedule-risk-analysis) are private; contact Critical Path Partners for access.

Strategic note

CPP is a forensic-scheduling consultancy. The engine is open-source as a deliberate posture choice: the CPM math is a decades-old peer-reviewed commodity (Kelley & Walker 1959, Kahn 1962, Tarjan 1972); the workflow, methodology discipline, and Daubert-disclosure posture are where forensic value lives. Open-sourcing the math layer means any academic, solo forensic, contractor's internal scheduler, or independent reviewer has a transparent, citable foundation to inspect, modify, or build on.

If you ship something built on this engine, we'd love to hear about it: danafitkowski@gmail.com.