SISO Agent Stack — Registry Model

The canonical hierarchy

Great Library of SISO └── Agents section / browse view └── SISO Agent Stack versioned assembly ├── SISO Project OS required component ├── SISO Agent Runtime required component ├── Agent Zero required component ├── Skills Hub required component ├── Agent Playbook required component ├── Agent Hooks required component ├── Agent Brain optional component ├── Session Intelligence optional component ├── Agent Integrations optional component └── Herdr optional external component SISO Agent Stack Distribution one-clone installer for the assembly

The component row is deliberately flat. Runtime, coordination, memory, model, tool, and playbook labels do not become artificial second-level categories. The assembly record carries each component's contextual role and connections.

What each component owns in this assembly

RequiredSISO Project OSProject-local operating layer

Architecture, canonical work, claims, run packets, verification, delivery, durable knowledge, and cold-pickup state.

RequiredSISO Agent RuntimeProvider-neutral host execution

Runs agent sessions, lifecycle, context, status, profiles, and command surfaces without owning project truth or coordination policy.

RequiredAgent ZeroConversation and coordination layer

Holds intent, priorities, lane boundaries, durable context, dispatch state, evidence distinctions, and final synthesis. The current artifact is a skill, not a generic playbook category.

RequiredSkills HubAtomic capabilities

Supplies reusable capabilities installed into both supported hosts from exact source pins.

RequiredAgent PlaybookScenario composition

Composes skills, tools, prompts, lanes, gates, and evidence into repeatable operating scenarios.

RequiredAgent HooksLifecycle automation

Generates Claude Code and Codex hook configuration from one manifest and verifies exact installed payloads.

Agent BrainOptional shared state

Provides durable task, artifact, memory, timeline, heartbeat, cost, and coordination APIs without publishing live databases.

Session IntelligenceOptional privacy-sensitive learning

Learns from explicitly supplied sessions while raw inputs and generated state remain outside the distribution.

Agent IntegrationsOptional adapters

Houses experimental runtime adapters with independent promotion and rollback gates.

HerdrOptional external terminal substrate

Provides persistent workspaces and addressable lanes while retaining external ownership and Apache-2.0 licensing.

The operating loop

1
Orient
Agent Zero reads the human outcome against Project OS state.

2
Brief
Agent Zero, Runtime, Skills, and Playbook select roles, capabilities, and an explicit return contract.

3
Run
Runtime executes while Hooks and optional Herdr lanes expose observable lifecycle state.

4
Prove
Hooks enforce verification; Project OS and optional Brain persist the appropriate durable truth.

5
Synthesize
Agent Zero returns verified state and the next bounded action.

Skills and playbooks belong together

Concept	Meaning	Placement
Skill	A reusable agent capability with a trigger, bounded instructions, and an expected result contract.	With the component or package that owns the behavior; indexed across the stack.
Playbook	A scenario-specific composition selecting and sequencing skills, tools, lanes, model choices, evidence, and verification. It may itself be delivered through a skill.	With its owning capability package; not a separate top-level stack layer.
SISO Agent Playbook	An independently released package containing scenario skills, tools, prompts, telemetry, and evidence.	Required Assembly component and independently addressable Work.
SISO Agent Hooks	Mechanical lifecycle automation around host events, commands, state, and completion verification.	Required Assembly component and independently addressable capability pack.

Concept

Meaning

Placement

Skill

A reusable agent capability with a trigger, bounded instructions, and an expected result contract.

With the component or package that owns the behavior; indexed across the stack.

Playbook

A scenario-specific composition selecting and sequencing skills, tools, lanes, model choices, evidence, and verification. It may itself be delivered through a skill.

With its owning capability package; not a separate top-level stack layer.

SISO Agent Playbook

An independently released package containing scenario skills, tools, prompts, telemetry, and evidence.

Required Assembly component and independently addressable Work.

SISO Agent Hooks

Mechanical lifecycle automation around host events, commands, state, and completion verification.

Required Assembly component and independently addressable capability pack.

Where the other concerns go

Concern	Why it is not a section under Agents	How it is represented
Models and CLIs	They are replaceable execution capacity, not durable product hierarchy.	Dependencies, providers, adapters, and evidence attached to the component that uses them.
Memory and context	They are responsibilities distributed across Project OS, Agent Base, and Agent Zero.	Owned records and capabilities, with explicit source-of-truth boundaries.
Research and evaluations	They explain or test decisions; they do not operate the stack by themselves.	Evidence attached to a Work, Release, Assembly, or decision.
A newly independent package	It becomes independently forkable, releasable, or referenceable.	A new stable Work linked into a later Assembly version.

Concern

Why it is not a section under Agents

How it is represented

Models and CLIs

They are replaceable execution capacity, not durable product hierarchy.

Dependencies, providers, adapters, and evidence attached to the component that uses them.

Memory and context

They are responsibilities distributed across Project OS, Agent Base, and Agent Zero.

Owned records and capabilities, with explicit source-of-truth boundaries.

Research and evaluations

They explain or test decisions; they do not operate the stack by themselves.

Evidence attached to a Work, Release, Assembly, or decision.

A newly independent package

It becomes independently forkable, releasable, or referenceable.

A new stable Work linked into a later Assembly version.

How the model evolves without pretending V1 is perfect

Works keep stable IDs even if repositories, names, and sections move.

An Assembly is immutable. A changed stack creates Assembly 1.1 or 2.0 instead of rewriting history.

Roles are contextual strings inside the Assembly, not universal object classes.

New browse trees, dependency graphs, onboarding views, CLI output, and MCP responses are generated from the same Assembly record.

A category is added only when it is stable over time, mutually useful, and changes what a person or agent can do.

The machine-readable current source is registry/assemblies/siso-agent-stack-v2.json, validated by schemas/assembly.schema.json. Immutable V1 remains preserved. This HTML is an explanation, not a second registry.