Harnesses Reference

Cupcake supports multiple AI coding agents (harnesses). Each harness has different event models, response formats, and integration mechanisms.

Supported Harnesses

Harness	Integration	Context Injection	Ask Support
Claude Code	External hooks (stdin/stdout)	Yes	Full
Cursor	External hooks (stdin/stdout)	No	Limited
OpenCode	In-process TypeScript plugin	Limited	Converted to deny
Factory AI	External hooks (stdin/stdout)	Yes	Full

Quick Comparison

Event Models

Feature	Claude Code	Cursor	Factory AI	OpenCode
Pre-execution events	`PreToolUse`	`beforeShellExecution`, `beforeMCPExecution`, `beforeReadFile`	`PreToolUse`	`PreToolUse`
Post-execution events	`PostToolUse`	`afterFileEdit`	`PostToolUse`	`PostToolUse`
Prompt events	`UserPromptSubmit`	`beforeSubmitPrompt`	`UserPromptSubmit`	-
Session events	`SessionStart`, `SessionEnd`	`stop`	`SessionStart`, `SessionEnd`	-
Compaction	`PreCompact`	-	`PreCompact`	-

Response Formats

Harness	Allow	Deny	Ask
Claude Code	`permissionDecision: "allow"`	`permissionDecision: "deny"`	`permissionDecision: "ask"`
Cursor	`permission: "allow"`	`permission: "deny"`	`permission: "ask"`
Factory AI	`permissionDecision: "allow"`	`permissionDecision: "deny"`	`permissionDecision: "ask"`
OpenCode	`decision: "allow"`	`decision: "deny"`	`decision: "deny"` (with reason)

Field Naming Conventions

Harness	Event Tag Field	Field Style
Claude Code	`hook_event_name`	snake_case
Cursor	`hook_event_name`	snake_case
Factory AI	`hookEventName`	camelCase
OpenCode	`hook_event_name`	snake_case

Policy Portability

Policies can be shared across harnesses with some considerations:

Claude Code <-> Factory AI: Most policies are directly portable (same event names, similar structure)
Cursor: Different event names require separate policy files or conditional logic
OpenCode: Simpler event model (PreToolUse/PostToolUse only)

Use the required_events and required_tools metadata to target specific harnesses:

# METADATA
# scope: package
# custom:
#   routing:
#     required_events: ["PreToolUse"]
#     required_tools: ["Bash"]
package cupcake.policies.my_policy