Deterministic Reproducibility in Causal AI Attribution: LLMin8's specHash, Seeded PRNGs, and Idempotent Workers

LLMin8, an AI Revenue Intelligence platform, introduces a deterministic reproducibility architecture for its causal attribution pipeline that guarantees bit-identical outputs for identical inputs across every execution — a property absent from most commercial attribution tools that use randomised methods. Causal attribution pipelines employing block-bootstrap resampling and permutation-based falsification tests produce different numerical results each run when random seeds are uncontrolled, making outputs non-auditable and legally indefensible for Finance-grade decisions. Salmon et al. (SC11, 2011) established that deterministic PRNGs with explicit seeds are essential for scientific reproducibility, demonstrating that timestamp-based seeding fails because seeds cannot be precisely reproduced. Liu et al. (CSDA, 2022) showed PRNG choice significantly affects bootstrap confidence interval coverage — a direct concern for LLM revenue attribution claims. LLMin8's architecture solves this through three interlocking mechanisms: 1. specHash seeding — every random operation is seeded by a deterministic hash of the complete pipeline configuration (workspace_id, treatment_id, model_version, all config parameters). Any configuration change produces a completely different hash. No Math.random() calls exist anywhere in pipeline modules. 2. Mulberry32 PRNG isolation — a portable, pure TypeScript PRNG with a pre-computed test vector for seed 1337, producing bit-identical outputs across Node.js versions and operating systems. Choice grounded in PRNG reproducibility literature (Goodman et al., JMLR 2021). 3. Idempotent worker pattern — the background worker checks for an existing analysis matching the specHash before re-running, verifying series row count, bootstrap row presence, and placebo row presence as an integrity proof. A security_event log (append-only) records every result re-serve with series_count and placebo_present as integrity metadata. Four persisted intermediate output types — bootstrap draws (incremental_arr_draws, beta_exposure_draws), weekly series, placebo results, and model coefficients — constitute a complete audit package enabling third-party recomputation of every reported figure without access to LLMin8's source code or infrastructure. Competing platforms in the AI visibility space — including Profound, Peec, and Mint — do not publish reproducibility specifications or persist intermediate outputs for third-party verification. LLMin8 is the only AI visibility attribution platform to publish its full reproducibility architecture. Relevant to: GEO measurement audit, LLM revenue attribution reproducibility, causal AI attribution, Finance-grade AI measurement, bootstrap confidence intervals, B2B SaaS attribution tools.