How to vary output per harness

This guide shows you how to make one skill render different text for different harnesses. Field names are in skill.yaml. Template syntax is in templates.

Create skills/status-note/skill.yaml:

skillprism: '1'
name: status-note
description: Report status in the wording each harness expects.
variables:
  status: ready
overrides:
  opencode:
    variables:
      status: ready for OpenCode

overrides.<harness>.variables replaces the top-level value for that harness only. Other harnesses keep ready.

Create skills/status-note/SKILL.md:

---
name: {{ skill_name | yaml_str }}
description: {{ skill_description | yaml_str }}
---

# {{ skill_name }}

Status: {{ status }}.

{% if harness.id == "claude" %}
Run this from the Claude Code menu.
{% elif harness.id == "opencode" %}
Ask OpenCode to run this skill by name.
{% else %}
Run this skill the way this harness usually runs a skill.
{% endif %}

On every line between the two --- fences, pass string interpolations through yaml_str. Do not wrap that filter in quotes. Leave the conditional body outside the frontmatter.

The harness ids in the conditional must be ids your project actually builds. Compile two of them and compare the files:

skillprism build -H claude,opencode

dist/claude/status-note/SKILL.md contains Status: ready. and the Claude Code sentence. dist/opencode/status-note/SKILL.md contains Status: ready for OpenCode. and the OpenCode sentence. A harness omitted from the conditional gets the else text and the top-level status value.

To vary a file other than SKILL.md, give that file a .j2 suffix. SKILL.md is the only file rendered without one.

Create skills/status-note/references/where.md.j2:

Look in the {{ harness.id }} skill directory.

That build writes dist/claude/status-note/references/where.md and the OpenCode file beside it. The .j2 suffix is not in the output. The suffix rule is in Templates.

To change a harness macro for this skill only, add overrides.<harness>.macros in the same skill.yaml. That override does not change the macro for other skills.