PR #479 — Milestone 1: Traffic Cost Observability on Scan

Parent: #581 PR: https://github.com/canton-foundation/canton-dev-fund/pull/479

| | Months after grant approval | | :---- | :---- | | Estimated Delivery | Month 2 | | Focus | Making per-envelope traffic costs observable on Scan from production MainNet data |

Deliverables:

• Canton: traffic summary and view hash APIs on the mediator inspection and sequencer inspection services.
• Scan app: extended ScanVerdictIngestion to ingest traffic summaries alongside mediator verdicts.
• Scan API: traffic summaries served as part of /v0/events.
• Feature flag gating in the Scan app configuration, enabled by default once sufficient testing is complete.
• Integration testing on staging environments (CIRL, DevNet, TestNet).
• Unit and integration tests for traffic summary ingestion and serving.

Acceptance Criteria: Traffic summaries from MainNet confirmation requests are observable on the Scan API, enabling network explorers and app providers to compute approximate traffic-based reward previews.