Extending the CORAL framework

For day-to-day debug / reproduce loops see the sibling coral-debug skill. For creating a new examples/<task>/ (seed + task.yaml + grader package) see coral-new-task. This skill covers adding new components to the CORAL package itself.

Extending the grader infrastructure

If you're writing a grader for a specific task, use coral-new-task. This section is only for changes to the grader framework under coral/grader/:

• New helpers on TaskGrader (coral/grader/task_grader.py) — make sure they're useful to multiple existing example graders before adding.
• New GraderInterface implementations (coral/grader/protocol.py / base.py) — the bar is high; the existing protocol covers everything we currently need.
• Daemon-side changes (coral/grader/daemon.py) — concurrency, queue caps, worktree isolation, retry policy. Cover with tests/test_grader_daemon.py.
• Built-in graders under coral/grader/builtin/ — function_grader.py is the only one today; not wired through task.yaml. New built-ins should justify why a TaskGrader subclass per task isn't enough.

A new agent runtime

Adding a new runtime (e.g. another coding-agent CLI) means three small files plus a registry entry.

1. Create coral/agent/builtin/<name>.py and subclass AgentRuntime (coral/agent/runtime.py). Existing runtimes are the canonical reference — claude_code.py is the most complete; codex.py and cursor_agent.py are smaller and easier to mimic.
2. Register the runtime in coral/agent/registry.py:

python _RUNTIMES["my_runtime"] = MyRuntime _ALIASES["mine"] = "my_runtime" _DEFAULT_MODELS["my_runtime"] = "default-model-id"

1. Decide the runtime's native shared-state directory name (.claude for Claude Code, .codex for Codex, etc.). The worktree symlink uses this; pass it through shared_dir so generate_coral_md(...) renders the right paths.
2. If the runtime needs special config plumbing (e.g. cursor_agent.json, opencode.json, gateway port), follow the opencode pattern: emit a per-agent config file inside the worktree at startup.
3. Add a smoke test in tests/test_<runtime>.py modeled on tests/test_cursor_agent.py.

Reference recent additions: PR #79 (cursor_agent), commit f6f266e (codex web_search config fix).

A new CLI command

CLI is an old-school argparse single-file dispatcher.

1. Add a parser block in coral/cli/__init__.py::main(). Match the existing style — _HelpOnErrorParser, an epilog with Examples:, _CommandHelpFormatter. Add the new command name to _VISIBLE_COMMANDS so "did you mean?" suggestions work.
2. Implement cmd_<name>(args: argparse.Namespace) -> None in the most-fitting module under coral/cli/:

• start.py — agent lifecycle (start/resume/stop/status)
• query.py — read-only inspection (log/show/notes/skills/runs)
• eval.py — agent-side commands that mutate the worktree (eval/wait/diff/revert/checkout)
• heartbeat.py — heartbeat configuration
• ui.py — dashboard
• author.py — init / validate

Create a new module if none of those fit; keep imports lazy so coral --help stays fast.

1. Wire the function into the commands = {...} dict at the bottom of main().
2. If your command operates on a specific run, accept --task / --run via _add_run_args(parser) and resolve with coral.cli._helpers.find_coral_dir.
3. Add an example to CLAUDE.md's Commands section.

A new bundled skill or subagent template

These ship inside the package and are seeded into every run's .coral/public/skills/ (or agents/) by coral/workspace/project.py.

• Skill — create coral/template/skills/<name>/SKILL.md with frontmatter name and description. Include scripts/ and references/ subdirs as needed; existing examples are deep-research, organize-files, skill-creator.
• Subagent — create coral/template/agents/<name>.md (single markdown file). Existing examples are deep-researcher and librarian.
• Add a test in tests/test_template.py if the rendering pulls in new template variables.

The seed copy is one-shot per run (if not dst.exists()), so iterating on template content during development means deleting <run_dir>/.coral/public/skills/<name>/ and re-running coral start, or just editing the destination directly for that run.

A new hook

Right now there's only coral/hooks/post_commit.py. If you add another hook:

• Define a clear single entrypoint function (model on submit_eval).
• Make it pure-function over coral_dir + agent_id where possible.
• Atomic writes to .coral/public/ only; never write to a worktree from a hook.
• Add coverage to tests/test_hooks.py.

Configuration changes

coral/config.py is dataclass-based and merged via OmegaConf. When adding a new field:

1. Add it to the right dataclass (AgentConfig, GraderConfig, ...) with a sensible default.
2. If it deserves runtime validation, add it to the __post_init__ of that dataclass.
3. Cover the new field in tests/test_config.py.
4. Update examples/<task>/task.yaml only if the field is task-author facing — internal knobs should stay defaulted.
5. Mention it in CLAUDE.md if it changes user-visible behavior; otherwise leave the docs alone (CLAUDE.md describes invariants, not every flag).

Don't forget

• Lint + test before pushing: uv run ruff check . && uv run ruff format . && uv run pytest tests/ -v.
• Backward compatibility for run dirs. People resume old runs. Anything that reads from .coral/public/ must tolerate missing files (return defaults), not crash.
• No agent-side git. All commits go through coral eval → submit_eval. Don't add helpers that shell out to git from agent context.