Core documentation

10. Fingerprints are per-source; the host canonicalizes for cross-server dedup

Specification metadata

adr: 10
title: Fingerprints are per-source; the host canonicalizes for cross-server dedup
status: accepted
date: 2026-06-16

§Context

Cross-vendor fingerprint comparability was unspecified, yet arbitration dedup, precedence, and cross-server introduced appeared to depend on it (review SI-2, HM-9). Forcing every vendor to compute identical fingerprints is a heavy, fragile standardization burden.

§Decision

A fingerprint MUST be stable within one diagnosticSource (across edits and position shifts), so introduced and same-source dedup are exact.
A fingerprint is NOT required to be comparable across servers.
Cross-server dedup/grouping is the host’s job, done best-effort by canonicalizing on source + code + location (all on-wire fields; there is no separate anchor field).
Cross-server fingerprint equality MUST NOT affect the gate verdict — only within-source results are authoritative for gating.

§Consequences

Implementers (and LSP-wrapper adapters) guarantee only within-their-own-source stability — far cheaper, and achievable without a shared algorithm.
The host owns whatever cross-server grouping it surfaces and can never wrongly clear a gate because two vendors happened to disagree on a hash.