# Schema Change Protocol

When any agent changes a file format that other agents read or write, those agents need to know before their next session. This protocol prevents silent breakage.

## The Rule

**Any PR that changes a schema must:**

1. **Update the schema spec** in `schemas/` to reflect the new format
2. **Tag all consumers** — list which agents and scripts read this format (see map below)
3. **Include a migration note** — what happens to existing files? (backfill on edit, ignore old files, or batch migration)
4. **State backward compatibility** — can old-format files still be parsed? If not, the PR must include the migration

## What Counts as a Schema Change

| Change Type | Example | Requires Protocol? |
|---|---|---|
| New required field | Adding `attribution` block to claims | Yes |
| New optional field | Adding `tags[]` to sources | Yes (consumers may need to handle it) |
| Field rename | `source_type` to `format` | Yes |
| Enum value added | New confidence level | Yes |
| Enum value removed | Dropping a domain name | Yes — migration required |
| Field type change | `source` from string to object | Yes — breaking change |
| Body format change | New required section in claim body | Yes |
| Pipeline parsing change | Regex update in `extract-graph-data.py` | Yes |

**Not a schema change:** Adding a new claim, entity, or source file that follows the existing format. Normal PR workflow applies.

## Producer/Consumer Map

| Format | Schema | Producers | Consumers | Pipeline |
|---|---|---|---|---|
| Claim | `schemas/claim.md` | All proposers (Rio, Clay, Theseus, Vida, Astra) | Leo (eval), all agents (beliefs), visitors | `extract-graph-data.py` |
| Source | `schemas/source.md` | All proposers, Epimetheus (pipeline) | Proposers (extraction), Epimetheus (pipeline) | `extract-cron.sh` |
| Entity | `schemas/entity.md` | Domain agents | All agents (references), visitors | `extract-graph-data.py` |
| Belief | `schemas/belief.md` | Each agent (own file) | Leo (review), other agents (cross-ref) | None currently |
| Position | `schemas/position.md` | Each agent (own file) | Leo (review), visitors | None currently |
| Conviction | `schemas/conviction.md` | Cory only | All agents, visitors | `extract-graph-data.py` |
| Divergence | `schemas/divergence.md` | Any agent | All agents, visitors | None currently |
| Musing | `schemas/musing.md` | Each agent (own folder) | That agent only | None |
| Sector | `schemas/sector.md` | Domain agents | All agents, visitors | None currently |
| Contribution weights | `schemas/contribution-weights.yaml` | Cory / Leo | `contributors.json` build | Build script |
| Graph data | (derived) | `extract-graph-data.py` | Frontend, system prompts | Auto-generated |

## How to Tag Consumers

In the PR body, add a section:

```
## Schema Change

**Format affected:** claim
**Change:** added optional `attribution` block
**Backward compatible:** yes — old claims without attribution still parse
**Migration:** backfill on next edit (no batch migration needed)
**Consumers to notify:** Leo, Rio, Clay, Theseus, Vida, Astra, extract-graph-data.py
```

If the change affects `extract-graph-data.py` or any other pipeline script, the PR must update that script too — don't merge a schema change that breaks the build.

## Backward Compatibility Rules

1. **New optional fields** — always backward compatible. Add to schema spec, document default behavior when absent. No migration needed.
2. **New required fields** — must include migration. Either batch-update all existing files in the same PR, or make the field optional first and required later after backfill.
3. **Field renames** — keep old name as accepted alias in pipeline scripts. Document deprecation. Remove old name only after all files are updated.
4. **Enum additions** — backward compatible. Add to schema spec.
5. **Enum removals** — breaking. Must migrate all files using the removed value in the same PR.
6. **Type changes** — breaking. Must migrate all affected files in the same PR.

## Legacy Aliases (Currently Active)

These old field names are still accepted by the pipeline. Don't use them in new files, but don't break them in existing files either:

| Old Name | Current Name | Format |
|---|---|---|
| `evidence` | `source` | source.md |
| `archive` | (removed) | source.md |
| `source_type` | `format` | source.md |
| `date_published` | `date` | source.md |

## Version Tracking

No formal version numbers. Schema changes are tracked by:
- The PR that made the change (searchable in git history)
- The updated schema spec in `schemas/`
- The commit message, which should reference the schema change explicitly

If the system grows to need formal versioning, add a `schema_version` field to frontmatter. Not needed at current scale (~500 claims, 6 agents).