TruthSyntax — EVC (Evidence-Validated Confidence)

EVC is a small, explainable trust gate for actions and model outputs.

It ingests signals → aggregates into an instant score A(t) → smooths over time into E(t) → applies a policy to decide: ALLOW | STEP_UP | BLOCK.

• Monorepo: TypeScript + pnpm workspaces

• Packages:

  • @lumen-syntax/evc-core — core library (aggregation, EWMA smoothing, policy)
  • @lumen-syntax/evc-service — HTTP service exposing /evc/evaluate

• License: Apache-2.0

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Requirements

• Node.js ≥ 20
• pnpm ≥ 10

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Quickstart

Install and build all workspaces:

pnpm install
pnpm -r build

Run the HTTP service (dev):

pnpm --filter @lumen-syntax/evc-service dev

By default the service listens on http://localhost:8787.

Auth headers The POST /evc/evaluate endpoint expects:

• Authorization: Bearer dev-token
• x-session-id: run-123

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Healthcheck

curl -s http://localhost:8787/health
# → { "status": "ok" }

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Evaluate (cURL)

curl -s -X POST http://localhost:8787/evc/evaluate \
  -H 'Authorization: Bearer dev-token' \
  -H 'x-session-id: run-123' \
  -H 'Content-Type: application/json' \
  -d @examples/curl/evaluate.json

Example request body (examples/curl/evaluate.json):

{
  "signals": [
    { "name": "uncertainty",  "value": 0.12, "weight": 1.0, "evidence": "mc-dropout" },
    { "name": "consistency",  "value": 0.88, "weight": 1.2, "evidence": "n=5 majority" },
    { "name": "novelty",      "value": 0.30, "weight": 0.8, "evidence": "embedding-drift" },
    { "name": "verification", "value": 0.92, "weight": 1.5, "evidence": "tool-check:pass" }
  ],
  "alpha": 0.6,
  "thresholds": { "allow": 0.75, "step_up": 0.5 }
}

Example response:

{
  "decision": "ALLOW",
  "score": 0.81,
  "reasons": ["temporal_consistency", "low_uncertainty"]
}

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API

• Minimal OpenAPI: packages/evc-service/openapi.yaml

• Examples:

  • cURL: examples/curl/evaluate.sh, examples/curl/evaluate.json
  • Node: examples/node/request.ts

Endpoints

• GET /health → { status: "ok" }
• POST /evc/evaluate → { decision, score, reasons[] }

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Packages

@lumen-syntax/evc-core

Core scoring & policy:

• Aggregate signals → A(t)
• EWMA smoothing → E(t)
• Policy thresholds → ALLOW | STEP_UP | BLOCK

@lumen-syntax/evc-service

HTTP wrapper for the core engine.

• GET /health
• POST /evc/evaluate (requires Authorization and x-session-id headers)

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Development

Root scripts:

pnpm -r lint
pnpm -r typecheck
pnpm -r test
pnpm -r build
pnpm format

Service package scripts (most useful for local runs):

pnpm --filter @lumen-syntax/evc-service dev
pnpm --filter @lumen-syntax/evc-service build
pnpm --filter @lumen-syntax/evc-service start
pnpm --filter @lumen-syntax/evc-service test

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Contributing

Pull Requests welcome. Please:

• Keep README and OpenAPI in sync with the implementation.
• Include runnable examples when adding new endpoints.

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License

Apache-2.0 © Lumen Syntax