every.channel: sanitized baseline

evolution/proposals/ECP-0036-multi-variant-manifests.md

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+# ECP-0036: Multi-Variant Manifests (One Epoch, Many Variants)
+
+Status: Draft
+Author: Codex
+Reviewers: founder@every.channel
+Created: 2026-02-07
+
+## Decision
+
+Extend `ec-core` manifests to optionally carry *multiple* variant hash-lists in a single signed manifest object.
+
+One manifest epoch can describe:
+
+- the "master" logical stream id (base)
+- N variants, each with:
+  - variant id
+  - variant stream id
+  - chunk index range
+  - per-chunk hashes
+  - per-variant merkle root
+
+Subscribers verify chunks by selecting the variant entry matching the chunk's `stream_id` (derived from encryption `key_id`).
+
+## Motivation
+
+- Quality pools (ABR ladders) need coordination: all variants should share epoch boundaries and be verifiable under one signed statement.
+- One manifest object per epoch reduces gossip/chattiness vs per-variant manifests.
+- Makes it easy to proxy to playlist-based views (HLS) without coupling the transport to playlists.
+
+## Data Model
+
+Add to `ec-core`:
+
+- `ManifestVariant` (new)
+  - `variant_id: String`
+  - `stream_id: StreamId`
+  - `chunk_start_index: u64`
+  - `total_chunks: u64`
+  - `merkle_root: String`
+  - `chunk_hashes: Vec<String>`
+  - `metadata: Vec<StreamMetadata>` (variant-specific; optional but useful)
+
+Extend `ManifestBody`:
+
+- `variants: Option<Vec<ManifestVariant>>`
+
+Rules:
+
+- Legacy manifests keep using `chunk_hashes` (single-variant).
+- Multi-variant manifests set `chunk_hashes` empty and populate `variants`.
+- `ManifestBody.merkle_root` becomes:
+  - legacy: merkle root of `chunk_hashes`
+  - multi-variant: merkle root of ordered `variants[].merkle_root` (sorted by `variant_id`)
+
+## Publishing
+
+- `ec-node moq-publish` can publish a CMAF ladder: one track per variant, one init track per variant.
+- After each epoch, publish a single manifest frame containing all variants' hashes for that epoch.
+
+## Subscribing
+
+- Subscriber requires manifests as today.
+- To validate a chunk:
+  - identify `stream_id` from `object.meta.encryption.key_id` (strip `/init` suffix if present)
+  - find a manifest in store that covers `(stream_id, chunk_index)`
+  - compare expected hash from the matching `ManifestVariant`.
+
+## Reversibility
+
+- Backwards compatible: old readers ignore `variants`, new readers accept both formats.
+- If later we move to per-variant manifests, we can keep multi-variant as an optimization.
+