Custom agents

A CLI that is not in the catalog of five built-in agents is declared in .caesar/config.toml, without writing code — the generic adapter builds its command line from a template:

[[agent]]
id = "my-agent"
bin = "my-agent-cli"
args = ["--task-file", "{{taskDir}}/task.json", "--out", "{{reportPath}}", "--cwd", "{{workspace}}", "{{prompt}}"]
cwd_mode = "process"      # "process": the workspace is the process's cwd. "flag": already carried by a token in args.
network_args = ["--online"]  # optional: what must be added to open the network.

Substitution tokens

The tokens {{prompt}}, {{workspace}}, {{taskDir}}, {{reportPath}} and {{model}} are substituted; a token with no value ({{model}} if no model was requested — by --model, the role, or the [models] table) makes the entire argument disappear rather than leaving a residual undefined.

The presence of {{model}} in args is also what grants the declared agent the "model" capability: without it, a configured default model is dropped (with a report finding) and an explicit --model is refused.

Network capability

Declaring network_args is asserting that without these arguments the CLI is confined: caesar then promotes its network capability from "unknown" to "controllable", and honors them according to the task's network setting. Without them, caesar doctor announces "network unknown" and promises neither opening nor closing it.

What a generic agent gets by default

A generic agent has no declared capability by default (no native output schema, no MCP channel): it settles for the most tolerant report tier, the one that only requires knowing how to read $CAESAR_TASK_FILE and write $CAESAR_REPORT_PATH. That is deliberate — the standard's minimal contract is designed to be reachable by a script of a few lines, not only by the five agents supported by name.

Next steps

• Configuration — the full .caesar/config.toml reference, including [[agent]].
• The OACP standard — the file-based contract every agent, built-in or custom, has to speak.