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docs/tech-specs/capabilities.md

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+---
+layout: default
+title: "Capability Vocabulary Technical Specification"
+parent: "Tech Specs"
+---
+
+# Capability Vocabulary Technical Specification
+
+## Overview
+
+Authorisation in TrustGraph is **capability-based**. Every gateway
+endpoint maps to exactly one *capability*; a user's roles each grant
+a set of capabilities; an authenticated request is permitted when
+the required capability is a member of the union of the caller's
+role capability sets.
+
+This document defines the capability vocabulary — the closed list
+of capability strings that the gateway recognises — and the
+open-source edition's role bundles.
+
+The capability mechanism is shared between open-source and
+enterprise editions. The open-source edition ships a fixed
+three-role bundle (`reader`, `writer`, `admin`). Enterprise editions
+define additional roles by composing their own capability bundles
+from the same vocabulary; no protocol, gateway, or backend-service
+change is required.
+
+## Motivation
+
+The original IAM spec used hierarchical "minimum role" checks
+(`admin` implies `writer` implies `reader`). That shape is simple
+but paints the role model into a corner: any enterprise need to
+grant a subset of admin abilities (helpdesk that can reset
+passwords but not edit flows; analyst who can query but not ingest)
+requires a protocol-level change.
+
+A capability vocabulary decouples "what a request needs" from
+"what roles a user has" and makes the role table pure data. The
+open-source bundles can stay coarse while the enterprise role
+table expands without any code movement.
+
+## Design
+
+### Capability string format
+
+`<subsystem>:<verb>` or `<subsystem>` (for capabilities with no
+natural read/write split). All lowercase, kebab-case for
+multi-word subsystems.
+
+### Capability list
+
+**Data plane**
+
+| Capability | Covers |
+|---|---|
+| `query` | Read queries: agent, text-completion, prompt, graph-rag, document-rag, embeddings, triples, rows, NLP query, SPARQL, structured-query, mcp-tool |
+| `library:read` | List / fetch documents |
+| `library:write` | Add / replace / delete documents |
+| `collections:read` | List / describe collections |
+| `collections:write` | Create / delete collections |
+| `knowledge:read` | List / get knowledge cores |
+| `knowledge:write` | Create / delete knowledge cores |
+| `ingest` | text-load, document-load |
+| `export` | Streaming exports (triples, graph-embeddings, document-embeddings, entity-contexts, core-export) |
+| `import` | Streaming imports (triples, graph-embeddings, document-embeddings, entity-contexts, rows, core-import) |
+
+**Control plane**
+
+| Capability | Covers |
+|---|---|
+| `config:read` | Read workspace config |
+| `config:write` | Write workspace config |
+| `flows:read` | List / describe flows, blueprints, flow classes |
+| `flows:write` | Start / stop / update flows |
+| `users:read` | List / get users within the workspace |
+| `users:write` | Create / update / disable users within the workspace |
+| `users:admin` | Assign / remove roles on users within the workspace |
+| `keys:self` | Create / revoke / list **own** API keys |
+| `keys:admin` | Create / revoke / list **any user's** API keys within the workspace |
+| `workspaces:admin` | Create / delete / disable workspaces (system-level) |
+| `iam:admin` | JWT signing-key rotation, IAM-level operations |
+| `metrics:read` | Prometheus metrics proxy |
+
+### Open-source role bundles
+
+The open-source edition ships three roles:
+
+| Role | Capabilities |
+|---|---|
+| `reader` | `query`, `library:read`, `collections:read`, `knowledge:read`, `flows:read`, `config:read`, `keys:self` |
+| `writer` | everything in `reader` **+** `library:write`, `collections:write`, `knowledge:write`, `ingest`, `export`, `import` |
+| `admin` | everything in `writer` **+** `config:write`, `flows:write`, `users:read`, `users:write`, `users:admin`, `keys:admin`, `workspaces:admin`, `iam:admin`, `metrics:read` |
+
+Open-source bundles are deliberately coarse. `workspaces:admin` and
+`iam:admin` live inside `admin` without a separate role; a single
+`admin` user holds the keys to the whole deployment.
+
+### Authorisation evaluation
+
+For a request bearing a resolved set of roles
+`R = {r1, r2, ...}` against an endpoint that requires capability
+`c`:
+
+```
+allow if c IN union(bundle(r) for r in R)
+```
+
+No hierarchy, no precedence, no role-order sensitivity. A user
+with a single role is the common case; a user with multiple roles
+gets the union of their bundles.
+
+### Unknown capabilities and unknown roles
+
+- An endpoint declaring an unknown capability is a server-side bug
+  and fails closed (403, logged).
+- A user carrying a role name that is not defined in the role table
+  is ignored for authorisation purposes and logged as a warning.
+  Behaviour is deterministic: unknown roles contribute zero
+  capabilities.
+
+### Capability scope
+
+Every capability is **implicitly scoped to the caller's resolved
+workspace**. A `users:write` capability does not permit a user
+in workspace `acme` to create users in workspace `beta` — the
+workspace-resolver has already narrowed the request to one
+workspace before the capability check runs. See the IAM
+specification for the workspace-resolver contract.
+
+The three exceptions are the system-level capabilities
+`workspaces:admin` and `iam:admin`, which operate across
+workspaces by definition, and `metrics:read`, which returns
+process-level series not scoped to any workspace.
+
+## Enterprise extensibility
+
+Enterprise editions extend the role table additively:
+
+```
+data-analyst:   {query, library:read, collections:read, knowledge:read}
+helpdesk:       {users:read, users:write, users:admin, keys:admin}
+data-engineer:  writer + {flows:read, config:read}
+workspace-owner: admin − {workspaces:admin, iam:admin}
+```
+
+None of this requires a protocol change — the wire-protocol
+`roles` field on user records is already a set, the gateway's
+capability-check is already capability-based, and the capability
+vocabulary is closed. Enterprise introduces roles whose bundles
+compose the same capabilities differently.
+
+When enterprise introduces a new capability (e.g. for a feature
+that does not exist in open source), the capability string is
+added to the vocabulary and recognised by the gateway build that
+ships that feature.
+
+## References
+
+- [Identity and Access Management Specification](iam.md)
+- [Architecture Principles](architecture-principles.md)