Workspaces store graphs in graphs/<name>.yaml and schemas in schemas/<Name>.yaml. Both are YAML.
Graph YAML
There is no policy: block in graph YAML; trigger policy lives only on the macro side.
name: perception # required
prefix: robot1 # optional; omitted line => default = hostname without ".local"
nodes:
- id: camera # required, unique instance ID
type: camera # required, node type = folder name (YAML key is `type`)
inputs: # optional
- name: image # input port name (matches #[input] field)
source: camera/image # "<node_id>/<output_name>"
outputs: # optional
- name: image # output port name (matches #[output] field)
schema: sensor_msgs/Image # optional; "::" auto-normalized to "/"
max_slice_len: 6291456 # optional usize; runtime resolves if omitted (final fallback 16 MiB)
history_size: 2 # optional usize, default 0 (volatile; >0 = transient-local replay depth)
Top-level fields (GraphConfig)
| Field | Type | Required | Default | Meaning |
|---|
name | String | Yes | | Graph name. |
prefix | String | No | hostname without .local | Topic prefix. Omitted line resolves to the hostname at load time. |
nodes | list of node entries | No | empty | Node instances in the graph. |
Node entry fields (NodeDef)
| Field | YAML key | Type | Required | Default | Meaning |
|---|
id | id | String | Yes | | Unique instance ID. |
node_type | type | String | Yes | | Node type = folder name. The YAML key is type (serde rename). |
inputs | inputs | list | No | empty | Input bindings. |
outputs | outputs | list | No | empty | Output ports. |
| Field | Type | Required | Meaning |
|---|
name | String | Yes | Input port name (matches the #[input] field). |
source | String | Yes | <node_id>/<output_name>. |
Output fields (OutputDef)
| Field | Type | Required | Default | Meaning |
|---|
name | String | Yes | | Output port name (matches the #[output] field). |
schema | String | No | empty | Schema name (:: is normalized to /). Should match the output type declared in the node’s macro. If it doesn’t, cerulion graph run emits a warning and ignores this field for buffer sizing. |
max_slice_len | usize | No | (runtime-resolved; final fallback 16 MiB) | Max slice length. Skipped from output when none. |
history_size | usize | No | 0 | 0 = volatile; > 0 = transient-local replay depth. |
perception graph with nodes camera/detector/imu/fusion/tracker/diagnostics, topology only) exists at cerulion_core/fixtures/test_graph.yaml.
Schema YAML
cerulion schema create Reading writes schemas/Reading.yaml with a skeleton:
schemas:
Reading:
description: ""
fields:
# Add fields: type name
schemas:
Reading:
description: "A single sensor reading"
fields:
float64 value:
uint64 timestamp:
schemas: map holds one entry per schema name; each entry has a description string and a fields: map keyed by type name.
Schema info hash
cerulion schema info reports the schema name, description, field count, and Hash: 0x<16-hex>. The hash is the FNV-1a hash of the schema name. 
