agent-spec-protocol

Agent Spec Protocol v3.0

AP is a standard for HTML documents that are simultaneously human-readable pages and machine-navigable agent workspaces. It uses custom HTML elements (<ap-gate>, <ap-source>, <ap-gen>, etc.) to encode which agents own which sections, what pipeline state each section is in, and how agents read, write, and route through the document.

---

Why HTML

Most AI pipeline definitions live in YAML config files, JSON schemas, or markdown documents. All three have the same problem: they are invisible to humans without tooling, and they separate the pipeline definition from the content it produces. An Airflow DAG file and the data it processes are two completely separate things. A GitHub Actions workflow and the code it builds live in different files. You must hold both in your head simultaneously.

AP collapses those two things into one file. An AP document is the pipeline definition AND the content workspace. Open it in a browser: you see a readable document showing each stage, its current status, and whatever content agents have written. Open it with an XPath query: you see a machine-navigable graph of sections with precise routing and state. The same file, read two ways, serves two different audiences without compromise.

Why not JSON? JSON has no human-readable rendering and no native hierarchy that maps to document content. You cannot open a JSON pipeline config in a browser and read the actual output from each stage.

Why not YAML? Same problem — YAML is config, not content. Pipeline state and pipeline output are still in separate files.

Why not Markdown? Markdown is human-readable but machine-opaque. There is no standard way to attach pipeline metadata, agent assignments, or status to a markdown section. Agents parsing markdown must read and interpret prose to find their work — there is no precise address to navigate to.

HTML's specific advantages for AP:

• Native hierarchy — the DOM tree is a real data structure agents can query with XPath, not freeform text
• Custom elements — W3C standard extension point: define your own tags with full attribute freedom, no prefixing required
• Human rendering — any browser renders an AP document as a readable page with zero tooling
• Stable addressing — id attributes are W3C-standardized unique addresses; #competitive inside <ap-gate> is a precise, unambiguous pointer
• Semantic vocabulary — HTML elements like <del>, <mark>, <progress>, <time>, <details> carry meaning that agents can read without custom attributes
• Separation by design — element names declare type, attributes carry metadata, element content holds human/agent output

---

Design Philosophy

HTML is the medium — use it fully. AP does not invent structure that HTML already provides. The DOM tree is the pipeline graph: nesting expresses grouping, hierarchy expresses inheritance, element order expresses sequence.

Custom elements are the building block for pipeline stages. Pipeline attributes (agent, status, on-pass, on-fail, depends-on) belong only on custom elements — never on standard HTML elements. A parser finding pipeline stages looks for custom elements only. The hyphenated tag name is the signal. Reading layer attributes (kind, topic) are different: they may appear on any element, standard or custom, because they carry no workflow semantics and produce no parser scanning overhead for pipeline discovery.

The element name is the namespace. <ap-gate id="trends"> — the <ap-gate> wrapper makes trends unambiguous. There is no need to write id="ap-trends" or on-pass="ap-competitive". The surrounding element provides the context. Attributes on custom elements are owned by that element — no data- prefix is needed or wanted.

Hierarchy over repetition. Parent elements declare shared defaults. Child sections override only what is genuinely different. An attribute that appears on every section belongs on their parent.

Self-describing documents. An agent knows its own name. That is the only query it needs: //ap-gate[@agent='idea-trends'][@status='pending']. The document delivers the agent directly to its work — no scanning, no full-document reads.

Framework owns vocabulary. Users own values. AP defines the element names and valid enums. The values inside attributes — agent names, section IDs, output key names — belong to the implementor. Any domain can use AP without AP knowing anything about that domain.

AP operates at two independent layers:

• Reading layer — topic and kind attributes on any HTML element. Makes existing content findable by agents without restructuring. No workflow implied.
• Pipeline layer — custom elements with agent, status, on-pass, etc. Defines workflow stages where agents do work.

A page can use either layer independently or both together.

AP also separates three concerns that must never mix:

• Design — visual classes owned by the design system (e.g., bp-*)
• Protocol — agent routing, state, and contracts encoded as attributes on AP custom elements
• Content — what agents and humans write inside AP elements

---

The Reading Layer

The reading layer solves one problem: an agent must find specific content in a document without reading the whole thing.

A documentation page with 40 sections costs 8,000 tokens if an agent reads it in full. With reading layer attributes, the agent issues one XPath query and reads only the sections it needs. Like a book with a precise index — you don't read every page to find the definition of a term.

Two attributes. Both may appear on any HTML element — standard or custom. Neither implies workflow state or pipeline processing.

kind — What type of content is this?

A spec-defined closed vocabulary. Every AP-aware tool understands these values consistently.

Value	Meaning
summary	A condensed version of larger content
overview	High-level introduction to a topic
reference	Detailed lookup material (API docs, specs, tables)
key-point	A single critical insight worth highlighting
definition	A term and its meaning
example	A concrete illustration of a concept
instruction	Step-by-step directions for doing something

topic — What subject does this cover?

A user-defined open vocabulary. AP defines the attribute name. The implementor defines the values. Any string is valid. Use kebab-case for multi-word topics.

topic="authentication"
topic="error-handling"
topic="pricing"
topic="getting-started"

Reading Layer in Practice

<!-- a documentation page — no restructuring needed, just annotations -->
<section id="auth-intro"     topic="authentication" kind="overview">
  <h2>Authentication</h2>
  <p>Our API uses bearer tokens...</p>
</section>

<section id="auth-reference" topic="authentication" kind="reference">
  <h2>Authentication Reference</h2>
  <table>...</table>
</section>

<p id="auth-tldr" topic="authentication" kind="summary">
  Pass your API key as a Bearer token in the Authorization header.
</p>

<aside id="rate-limit-note" topic="rate-limiting" kind="key-point">
  Requests are limited to 1,000 per minute per API key.
</aside>

An agent answering "how does authentication work?" needs exactly two queries:

//*[@topic='authentication'][@kind='summary']     ← get the one-line answer first
//*[@topic='authentication'][@kind='reference']   ← get the full details if needed

Neither query reads the rate limiting section, the pricing section, or anything else. The document delivers targeted content directly.

Reading Layer Rules

• kind and topic may appear on any HTML element — standard or custom
• kind takes only the enumerated values above — no custom values
• topic is user-defined — any lowercase kebab-case string is valid
• These attributes carry no workflow semantics — no agent assignment, no state, no routing
• A document using only kind and topic is a valid AP reading-layer document even with no custom elements

---

Document Structure

Every AP document is a valid HTML5 file with three distinct zones:

Zone	Element	Owns
1	<html>	Design system attributes only
2	<head>	Document-level metadata in <meta> tags
3	<body>	Content and AP pipeline sections

---

Zone 1: The <html> Element

Only design system attributes live here. AP protocol does not touch <html>.

<html data-bp-theme="auto" lang="en">

---

Zone 2: Head Metadata

Document-level metadata lives in <head> as namespaced <meta> tags:

<meta name="[namespace]:[key]" content="[value]">

Namespace rules:

• Lowercase letters and hyphens only: a-z and -
• Must identify the plugin without requiring a lookup
• Registered: every plugin using AP registers its namespace to prevent collisions

Example:

<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>AI Memory Layer</title>

  <meta name="idea:id"            content="ai-memory-layer">
  <meta name="idea:status"        content="in-progress">
  <meta name="idea:current-stage" content="competitive">
  <meta name="idea:gates-passed"  content="trends">
  <meta name="idea:gates-failed"  content="">
  <meta name="idea:created"       content="2026-03-30T01:19:03Z">
</head>

The index contract: An orchestrator reading a portfolio of AP documents reads only <head> metadata — never section content. Meta tags must be complete and current. Every agent that updates a section status must also update the relevant <meta> tags.

---

Zone 3: AP Custom Elements

Each pipeline stage is an AP custom element in <body>. The element name declares the stage type. Attributes declare the metadata. Content is what agents and humans write.

AP custom elements may be nested. A parent <ap-parallel> contains child elements that run concurrently. All other nesting is for attribute inheritance.

---

AP Custom Elements

Element Vocabulary

Element	Who runs it	Gate decision?	Notes
<ap-source>	human	no	Immutable origin. Never modified after creation.
<ap-gen>	AI agent	no	Produces content with no pass/fail outcome.
<ap-transform>	AI agent	no	Converts inputs to a different output form.
<ap-gate>	AI agent	yes	Automated pass/fail decision.
<ap-review by="ai">	AI agent	yes	AI reads upstream content and decides.
<ap-review by="human">	human	yes	Human reads and decides. Status set manually. Never completed by an agent.
<ap-route>	AI agent	no	Reads context, writes route-to, orchestrator follows.
<ap-parallel>	orchestrator	no	Container: all children run concurrently.
<ap-placeholder>	—	—	Child element: marks unfilled content. Removed when agent writes.

Required Attributes

Every leaf AP element must have all three:

Attribute	Format	Example
id	kebab-case	id="competitive"
agent	agent name string	agent="idea-competitive"
status	enum	status="pending"

Recommended Attributes

Attribute	Type	Purpose
on-pass	section ID	Where control routes on pass
on-fail	section ID	Where control routes on failure
on-skip	section ID	Where control routes on skip
depends-on	space-separated IDs	Guards: all must be passed before this runs
context	space-separated IDs	Section IDs to inject as agent context
updated-at	ISO 8601 datetime	When agent last wrote to this section
version	positive integer	How many times this section has been written

Optional Attributes

Attribute	Type	Purpose
gate	enum	Whether this stage has a pass/fail gate decision
format	enum	Expected output shape
token-budget	positive integer	Max tokens the agent should write
outputs	space-separated keys	Named values this section produces
inputs	space-separated keys	Named values this section requires from upstream
route-to	section ID	Written by <ap-route> agents; orchestrator follows this

---

Attribute Inheritance

AP attributes cascade from parent to child elements, exactly like CSS properties cascade through the DOM. Declare shared defaults on the nearest common ancestor.

Cascading Attributes

Attribute	Cascades
gate	Yes
format	Yes
token-budget	Yes
on-fail	Yes — default escalation path for all children

Non-Cascading Attributes

Attribute	Does Not Cascade
agent	Each element has its own assigned agent
status	Each element holds its own live state
depends-on	Each element declares its own guards
context	Each element specifies its own read targets
outputs	Each element declares its own produced keys
inputs	Each element declares its own required keys
on-pass	Each element declares its own forward route
on-skip	Each element declares its own skip route
updated-at	Each element holds its own timestamp
version	Each element holds its own count

Inheritance Example

<!-- Parent sets shared defaults -->
<main gate="required" format="prose">

  <!-- Children only declare what is unique -->
  <ap-gate id="trends"
    agent="idea-trends"
    status="pending"
    context="raw-idea"
    on-pass="competitive"
    on-fail="human-triage"
  >

  <ap-gate id="competitive"
    agent="idea-competitive"
    status="blocked"
    depends-on="trends"
    context="raw-idea trends"
    on-pass="icp"
    on-fail="human-triage"
  >

</main>

---

Enumerated Vocabularies

Closed sets. No values outside these lists are valid.

status

Value	Meaning
pending	Not yet processed
running	Agent currently processing
passed	Gate cleared or section complete
failed	Gate not cleared
skipped	Intentionally bypassed
blocked	Waiting on a dependency that has not passed

gate

Value	Meaning
required	Must pass for downstream sections to become runnable
optional	Informational — pipeline continues regardless of outcome
none	Purely generative; no gate decision

format

Value	Meaning
prose	Narrative text paragraphs
json	Structured JSON data
list	Unordered or ordered list
table	Tabular data
html	Rich HTML fragment
mixed	Multiple formats within the section

---

HTML Semantic Elements as Agent-Readable State

AP custom elements handle pipeline-level concerns. For content-level state within a section, use native HTML semantic elements — they carry meaning that both browsers and agents understand without custom attributes.

HTML element	Human sees	Agent reads as
<del>	strikethrough	done / removed / no longer applies
<ins>	underline	newly added / just written
<mark>	highlight	flagged / needs attention
<progress value="3" max="7">	progress bar	3 of 7 steps complete
<details open>	expanded section	currently active
<details> (no open)	collapsed	not active / archived
<time datetime="...">	readable date	machine-parseable ISO timestamp
<strong>	bold	high importance

Example — an agent marking completed checklist items:

<ul>
  <li><del>Research competitors</del></li>   <!-- done -->
  <li>Write ICP analysis</li>                <!-- pending -->
  <li><mark>Review pricing model</mark></li>  <!-- needs attention -->
</ul>

XPath to find incomplete items: //li[not(del)]

---

Parallel Execution via Nesting

Sections that can run concurrently are wrapped in <ap-parallel>. The nesting IS the group declaration.

<ap-parallel id="phase-3" depends-on="competitive">

  <ap-gen id="icp"      agent="icp-agent"      status="blocked">
  <ap-gen id="mom-test" agent="mom-test-agent"  status="blocked">
  <ap-gen id="mvp"      agent="mvp-agent"       status="blocked">

</ap-parallel>

The orchestrator fans out all children simultaneously when <ap-parallel> becomes runnable. The container completes when all children have status="passed".

---

Routing

Each AP element declares where control goes when it finishes. The orchestrator never needs to scan for what comes next.

Attribute	Trigger	Meaning
on-pass	section passes	Activate this section ID next
on-fail	section fails	Activate this section ID next
on-skip	section is skipped	Activate this section ID next
depends-on	before running	Guard: all listed IDs must be passed first

depends-on is a guard — prevents a section from starting too early. on-* are routes — they tell the orchestrator where to go after. Two different jobs; two different attributes.

Dynamic Routing via <ap-route>

When routing logic is too complex for a static value, use <ap-route>. The agent reads context, decides the next target, writes route-to on its own element — never on any other element — then sets status="passed". The orchestrator follows route-to.

<ap-route
  id="score-router"
  agent="scoring-router-agent"
  context="trends competitive"
  status="pending"
  route-to=""
>
  <!-- agent writes route-to="icp" or route-to="human-triage" based on scores -->
</ap-route>

---

Output/Input Contracts

Key Naming Convention

Keys are namespaced with a colon: [section-id]:[key-name]. This prevents two sections from producing a key with the same name.

trends:score
trends:recommendation
competitive:gaps

<ap-gate id="trends"
  outputs="trends:score trends:recommendation trends:signals">

<ap-gate id="competitive"
  inputs="trends:score trends:recommendation"
  outputs="competitive:score competitive:gaps">

Every key in inputs must resolve unambiguously to exactly one upstream element's outputs. The CLI validates this graph.

---

What a Completed Section Looks Like

<!-- PENDING -->
<ap-gate id="trends" agent="idea-trends" status="pending" on-pass="competitive">
  <ap-placeholder>Trends analysis pending.</ap-placeholder>
</ap-gate>

<!-- COMPLETED -->
<ap-gate id="trends" agent="idea-trends" status="passed" updated-at="2026-05-12T14:30:00Z" version="1" on-pass="competitive">
  <h2>Trends Analysis</h2>
  <p>Strong market signal across three growth vectors...</p>
  <footer>
    <time datetime="2026-05-12T14:30:00Z">May 12, 2026 at 2:30 PM</time>
    · idea-trends · 387 tokens
  </footer>
</ap-gate>

updated-at is agent-writable and XPath-queryable. version tracks rewrites. <time datetime="..."> renders the timestamp for humans in the browser. <ap-placeholder> is removed when the agent writes real content — its presence alone signals pending state.

---

Agent Navigation

An agent knows its own name. One query delivers it directly to its work:

//ap-gate[@agent='idea-competitive'][@status='pending']

The CLI materializes inheritance before returning an element to an agent. When ap next --agent=idea-competitive runs, the CLI resolves all attributes inherited from parent elements and returns the section with its full resolved attribute set. Agents never walk the tree themselves — they receive a complete work order.

Common XPath Patterns

//ap-gate[@agent='idea-trends'][@status='pending']      ← agent finds its pending work
//ap-gate[@id='competitive']                             ← read a specific section
//ap-gate[@status='failed'][@gate='required']            ← find blocking failures
//ap-review[@by='human'][@status='pending']               ← find work waiting on a human
//*[@status='pending'][not(ap-placeholder)]              ← pending but already has content
//ap-gate[@version > 1]                                  ← sections rewritten more than once
//li[not(del)]                                           ← incomplete checklist items

---

Orchestrator Contract

The orchestrator reads only <head> meta tags and AP element attributes. It never reads section content.

Algorithm:

1. Read all AP elements — collect id, agent, status, depends-on, gate, on-pass, on-fail
2. Resolve inherited attributes for each element (cascade from parent)
3. Find the first element where:
   • status="pending"
   • All IDs in depends-on have status="passed" (or attribute is absent)
4. If inside <ap-parallel>, fan out all pending siblings simultaneously
5. Run the agent for that element
6. After agent completes:
   • Update status
   • Set updated-at to current ISO 8601 timestamp
   • Increment version
   • Follow on-pass, on-fail, or on-skip to activate the next element
   • Update relevant <meta> tags in <head>

---

Agent Write Contract

When an agent writes to its element:

1. Read context: fetch elements listed in context using XPath
2. Read its own element: fetch //ap-gate[@id='[own-id]'] to see current state
3. Respect token budget: do not exceed token-budget (if present)
4. Respect format: output matches format
5. Remove placeholder: replace <ap-placeholder> with real content
6. Set outcome: update status to passed or failed
7. Set timestamp: write updated-at with current ISO 8601 datetime
8. Increment version: add 1 to version (or set to 1 if absent)
9. Never touch other elements — write scope is exactly its own element

---

ID Rules

• Format: kebab-case, lowercase, letters and hyphens: [a-z][a-z0-9-]*
• Unique per document
• Frozen once set — IDs are stable addresses. #competitive today finds the same element indefinitely. Never rename or reuse.

Valid: raw-idea, competitive, mom-test Invalid: Raw_Idea (uppercase/underscore), 3rd (starts with digit)

---

Complete Example

<!DOCTYPE html>
<html lang="en" data-bp-theme="auto">
<head>
  <meta charset="UTF-8">
  <title>AI Memory Layer</title>
  <meta name="idea:id"            content="ai-memory-layer">
  <meta name="idea:status"        content="in-progress">
  <meta name="idea:current-stage" content="trends">
  <meta name="idea:gates-passed"  content="">
  <meta name="idea:created"       content="2026-05-12T00:00:00Z">
</head>
<body>

  <main gate="required" format="prose">

    <ap-source id="raw-idea" agent="human" status="passed" outputs="raw-idea:text">
      <h2>Raw Idea</h2>
      <p>The raw idea text goes here, exactly as captured.</p>
    </ap-source>

    <ap-gate id="trends"
      agent="idea-trends"
      status="pending"
      context="raw-idea"
      inputs="raw-idea:text"
      outputs="trends:score trends:recommendation"
      on-pass="competitive"
      on-fail="human-triage"
    >
      <ap-placeholder>Trends analysis pending.</ap-placeholder>
    </ap-gate>

    <ap-gate id="competitive"
      agent="idea-competitive"
      status="blocked"
      depends-on="trends"
      context="raw-idea trends"
      inputs="raw-idea:text trends:score trends:recommendation"
      outputs="competitive:score competitive:gaps"
      on-pass="phase-3"
      on-fail="human-triage"
    >
      <ap-placeholder>Blocked — waiting for trends to pass.</ap-placeholder>
    </ap-gate>

    <ap-parallel id="phase-3" depends-on="competitive">

      <ap-gen id="icp"      agent="icp-agent"      status="blocked" context="raw-idea competitive">
      <ap-gen id="mom-test" agent="mom-test-agent"  status="blocked" context="raw-idea competitive">
      <ap-gen id="mvp"      agent="mvp-agent"       status="blocked" context="raw-idea competitive">

    </ap-parallel>

    <ap-review by="human"
      id="final-review"
      agent="human"
      status="blocked"
      depends-on="phase-3"
    >
      <ap-placeholder>Awaiting human review after all analysis completes.</ap-placeholder>
    </ap-review>

  </main>

</body>
</html>

---

Extending AP

AP is a protocol, not a fixed vocabulary. The <ap-*> elements are the reference implementation — the vocabulary AP ships with. Any team can define their own custom elements and remain fully within spec, as long as those elements honor the core attribute contract.

The Core Contract

Any custom element is AP-compliant if it:

1. Has a hyphenated tag name (W3C requirement for all custom elements)
2. Carries id, agent, and status on every pipeline stage element
3. Uses the enumerated values for status without modification
4. Uses on-pass, on-fail, on-skip, and depends-on for routing and guards when routing is needed

That is the entire contract. AP does not need to know your element names.

Domain Vocabulary Example

A legal team defines their own elements. An orchestrator that understands the core contract routes through this document without any changes:

<legal-intake   id="case-filing"    agent="intake-bot"    status="pending" on-pass="extraction">
<legal-extract  id="extraction"     agent="clause-reader" status="blocked" on-pass="risk-gate" depends-on="case-filing">
<legal-gate     id="risk-gate"      agent="risk-assessor" status="blocked" on-pass="sign-off"  on-fail="flagged" depends-on="extraction">
<legal-review   id="sign-off"       agent="human"         status="blocked" depends-on="risk-gate">

The orchestrator reads agent, status, on-pass, on-fail, depends-on — the same six attributes it reads on <ap-gate>. It never needs to know what <legal-gate> means.

Rules for Domain Extensions

• Tag names must contain a hyphen: legal-gate is valid; legalgate is not
• Do not redefine the core attribute enum values — status="approved" instead of status="passed" breaks orchestrator compatibility
• Do not add AP protocol semantics to standard HTML elements in the same document — pick one model per document
• Document your element vocabulary the same way AP does: element name, who runs it, whether it produces a gate decision

What Implementors Get for Free

Because it is HTML, domain teams do not write a new parser. Every language has an HTML parser that handles custom elements:

Language	Library
JavaScript	Native DOM (querySelectorAll, XPath)
Python	BeautifulSoup, lxml
Ruby	Nokogiri
Go	golang.org/x/net/html
Rust	html5ever

An XPath query that works on <ap-gate> works identically on <legal-gate>:

//*[@status='pending'][not(ap-placeholder)]   ← finds pending work in any vocabulary

---

Validation Checklist

Structure

• Valid HTML5
• <html> has no AP attributes
• <head> contains at least one <meta name="[namespace]:[key]"> tag

Elements

• Every AP pipeline stage uses a custom element with a hyphenated tag name
• No AP protocol attributes (agent, status, on-pass, on-fail, depends-on, etc.) appear on standard HTML elements (<section>, <div>, <article>, etc.) — this is a violation, not a warning
• Every leaf AP element has id, agent, status
• All IDs match ^[a-z][a-z0-9-]*$ (kebab-case, no prefix required)
• All IDs are unique within the document
• status is one of the enumerated values
• gate is one of the enumerated values (if present)
• format is one of the enumerated values (if present)
• An <ap-source> element never has status="running"
• An <ap-review by="human"> element is never set to status="passed" by an agent

Routing and Dependencies

• All IDs in depends-on reference existing element IDs in the document
• All IDs in context reference existing element IDs in the document
• All IDs in on-pass, on-fail, on-skip reference existing element IDs
• No circular dependencies in depends-on chains

Contracts

• Every key in inputs follows the [section-id]:[key-name] convention
• Every key in inputs appears in a reachable upstream element's outputs
• No two elements produce a key with the same fully-qualified name

---

Open Issues

OI-1: Formal Attribute Type Grammar

Each attribute needs a declared type for validators to be written against the spec without interpretation:

Type	Meaning	Example
string	Freeform text	agent name
enum	One value from a closed set	pending, gate
id	A single kebab-case section ID	trends
id-list	Space-separated section IDs	trends raw-idea
key-list	Space-separated namespaced contract keys	trends:score trends:recommendation
integer	Positive whole number	3
ISO-8601	Full datetime string	2026-05-12T00:00:00Z

Status: Not yet assigned to each attribute. Needed before v1.0 stability declaration.

---

OI-2: Multi-Domain Worked Examples

The spec uses one domain (idea validation) in all examples. Two additional worked examples are needed:

• Suggested example A: Legal document review — intake, AI extraction, human-review gate, compliance gate, final approval
• Suggested example B: Software CI pipeline — source commit, lint gate, test gate, build transform, deploy gate

These should live in /examples/ and use real agent names, routing decisions, and inputs/outputs contracts.

Status: Not yet written.

---

OI-3: Stability Promise

Every attribute needs a maturity level before open source publication:

Level	Meaning
stable	Will not change in a breaking way within a major version
experimental	May change; implementors should expect breakage
reserved	Defined but not yet implemented

Status: Maturity levels not yet assigned.

---

OI-4: Parallel Container Error Model

When some children of <ap-parallel> pass and some fail:

• Does the container itself pass, fail, or take a new value like partial?
• Does on-fail on the container fire if any child fails, or only if all children fail?
• Can on-pass fire before all children complete?

Status: Semantics not yet defined. Blocking for pipelines using parallel execution with required gates.