cpm-engine

The forensically-defensible CPM engine. AACE-canonical. Daubert-disclosed. Bit-identical between JavaScript and Python.

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

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Quick start

npm install @critical-path-partners/cpm-engine

const E = require('@critical-path-partners/cpm-engine');

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); // 2.9.27

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

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Why this engine?

Capability	cpm-engine	SmartPM	Acumen Fuse	Phoenix
Open source	yes	no	no	no
AACE-canonical method labels (29R-03 / 49R-06 / 52R-06)	yes	partial	partial	partial
FRE 707 / Daubert disclosure (built-in)	yes	no	no	no
JS-Python bit-identical parity	yes	n/a	n/a	n/a
Topology fingerprint hash (SHA-256, copy-detection)	yes	no	no	no
Kinematic delay dynamics (velocity / accel / jerk)	yes	no	no	no
Bayesian update with hierarchical pooling	yes	no	no	no
Multi-jurisdiction holiday calendars (66 jurisdictions)	yes	partial	partial	partial
MIT licensed	yes	no	no	no

The engine math is a commodity. The competitive moat in forensic scheduling is the workflow, the discipline, and the Daubert posture — not the forward pass. Critical Path Partners open-sources the engine so any academic, any solo forensic, any contractor's internal scheduler can build on a defensible foundation.

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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 jurisdictions (CA-FED + 13 provinces, US-FED + 50 states + DC)

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AACE alignment

The engine implements the math behind these AACE Recommended Practices:

RP	Title	Method labels emitted
29R-03	Forensic Schedule Analysis	MIP 3.3 / 3.6 / 3.7 / 3.8
49R-06	Identifying the Critical Path	LPM, TFM, MFP
52R-06	Prospective Time Impact Analysis	MIP 3.6 (Single Simulation) / MIP 3.7 (Multiple Base)
122R-22	Quantitative Risk Analysis Maturity Model (QRAMM)	(badge surface)
PPG #20 (2nd Ed 2024)	Forensic Schedule Analysis Practice Guide	(general acceptance)

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

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Verifiable provenance

Every computation emits a manifest:

result.manifest = {
    engine_version: '2.9.27',
    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)
// Two XERs with identical hashes ARE the same schedule, regardless of UID rotation.

This is the single most important forensic feature in the engine. Bid-collusion detection, retroactive-manipulation detection, and copy-detection across XERs all rely on it. It is also the foundation that lets opposing counsel verify a CPP analysis post-hoc.

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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
# 43 fixtures × 747 checks. 0 deviations as of v2.9.27.

Plus a 282-activity real-XER stress test reports 0 mismatches.

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.

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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 <commit-sha>     # 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.

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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.

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Citation

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

Fitkowski, D. (2026). cpm-engine: A forensically-defensible critical-path-method engine with AACE-canonical method labels and Daubert disclosure. Critical Path Partners. Version 2.9.27. https://github.com/danafitkowski/cpp-cpm-engine

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

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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.

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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, AACE 29R-03 §4.3 actual_start immutability, 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 v2.9.27.

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Contributing

See CONTRIBUTING.md. Forensic correctness is enforced — every commit must pass 792 unit tests and 416 cross-validation checks. New citations require WebSearch-verified URLs. No fabricated case names. No LLM-generated narratives in core engine paths.

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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.

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Strategic note

CPP is a forensic-scheduling consultancy. The engine is open-source not as a loss-leader but as a deliberate inversion of the competitive landscape: the math is a commodity, the workflow and discipline are not. Every academic, every solo forensic, every contractor's internal scheduler now has a reason to install CPP and a citation pathway. The closed-engine competitors — SmartPM, ALICE, Nodes&Links, Acumen — cannot match this move because their valuations require the engine stay proprietary.

If you ship something built on this engine, we'd love to hear about it: [email protected].