Top-level vs. nested primitives

Every AXON primitive is either top-level (it stands alone at the program root) or nested (it only appears inside another construct). The compiler enforces this at parse time: a step declaration outside any flow is a syntax error; a flow declaration inside another flow is too.

This page is the authoritative table. When an agent is unsure where a primitive belongs, it should consult this resource — every decision follows from one row.

How to read this table

• Surface — the AXON keyword as it appears in source.
• Top-level — ✓ if the keyword starts a top-level declaration; ✗ if it only appears nested.
• Lives inside — for nested primitives, the parent construct(s) that may contain it.
• Category — the family the primitive belongs to (drives the axon.primitives(filter) facet).
• Since — the cycle that introduced it.

Cognition

Surface	Top-level	Lives inside	Since
persona	✓	— (referenced by run … as and step … use)	v0.1.0
context	✓	— (referenced by run … within)	v0.1.0
flow	✓	—	v0.1.0
anchor	✓	— (referenced by run … constrained_by [...])	v0.1.0
tool	✓	— (referenced implicitly by the tool surface)	v0.1.0
intent	✓	—	v0.1.0
memory	✓	—	v0.1.0
agent	✓	—	v0.1.0
step	✗	flow	v0.1.0
reason	✗	flow (sibling of step) — also step body	v0.1.0
probe	✗	flow, step body	v0.1.0
validate	✗	flow	v0.1.0
refine	✗	flow	v0.1.0
weave	✗	flow	v0.1.0
use	✗	flow, step header	v0.1.0

Cognitive I/O

Surface	Top-level	Lives inside	Since
resource	✓	—	v1.2.0
fabric	✓	—	v1.2.0
manifest	✓	—	v1.2.0
observe	✓	—	v1.2.0
reconcile	✓	—	v1.2.0
lease	✓	—	v1.2.0
ensemble	✓	—	v1.2.0
session	✓	— (referenced by socket protocol:)	v2.3.0

Data plane

Surface	Top-level	Lives inside	Since
axonstore	✓	—	v1.31.0
dataspace	✓	—	v1.31.0
corpus	✓	—	v1.31.0
pix	✓	—	v1.14.0
ledger	✓	—	v2.12.0
type	✓	—	v0.1.0

Session types & wire

Surface	Top-level	Lives inside	Since
session	✓	—	v2.3.0
socket	✓	—	v2.3.0
axonendpoint	✓	—	v1.23.0
axpoint	✓	—	v1.23.0
daemon	✓	—	v1.11.0
mcp	✓	—	v1.24.0+
listen	✗	flow, daemon body	v1.11.0
channel	✓	—	v1.6.0
emit	✗	flow, daemon body	v1.6.0
publish	✗	flow, daemon body	v1.6.0
discover	✗	flow, daemon body	v1.6.0

The taint keyword is a reserved word in the lexer but has no parser production today (it appears in the epistemic-uncertainty lattice in axon-frontend::epistemic, not as a top-level declaration). If a future cycle introduces a taint <Name> { … } declaration the registry + this table grow together.

Operators

Surface	Top-level	Lives inside	Since
shield	✓	—	v1.13.1
mandate	✓	—	v1.13.1
compute	✓	—	v1.12.0
lambda	✓	—	v1.10.0
forge	✗	flow	v1.12.0
ots	✓	—	v1.4.0
psyche	✓	—	v1.5.2
agent	✓	—	v1.12.0

The logic keyword is a reserved word in the lexer but — like taint (v1.2.0) — has no parser production today. If a future cycle introduces a logic <Name> { … } declaration the registry + this table grow together.

Statements (not primitives, but parsed at flow body)

These are statements an agent treats as the body of a flow. They are NEVER top-level.

Surface	Lives inside	What it does
if … else	flow body	Conditional branch
for x in …	flow body	Bounded iteration
let x = …	flow body	Local binding
return …	flow body	Early/explicit return
break	inside for	Loop early-exit
continue	inside for	Next iteration
run …	top-level — but it is a binding, not a declaration	Binds a flow to a persona+context+anchors
apply	step body field	Invoke another flow

Composition discipline

• Flows compose by apply, not by nesting. A flow declaration cannot appear inside another flow. Sub-flows are referenced from a step body via apply: <FlowName>.
• Anchors and shields bind through run, not the flow header. A flow does not list its constraints; the run statement that executes it does, via constrained_by [...].
• Personas, contexts, and tools are referenced, not redeclared. A flow that uses a persona references it (as <Persona> on the run, or use <Persona> per step). It does not embed a fresh declaration.

For the why behind these rules, read axon://logic/flow_composition.