Skill mode vs prompt mode

The harness has two flavors that share one config surface. Skill mode tests a predefined skill (/my-skill --args); prompt mode tests an agent capability directly by sending a prompt with no skill wrapper. You pick one by setting either execution.skill or execution.prompt — never both.

The one distinction

execution.skill invokes a SKILL.md implementation. execution.prompt sends a raw prompt to the agent. Everything downstream — dataset, judges, thresholds, tool interception, reward — is identical. This is orthogonal to execution.mode (case vs batch), which only controls how many invocations run.

Which one do I want?

You want to evaluate…	Use	Because
A skill's correctness, quality, cost	skill mode (execution.skill)	The skill under test is the artifact you iterate on
Whether agents can navigate/apply your docs	prompt mode (execution.prompt)	The docs (not a skill) are the artifact under test
An agent capability (code gen, API usage, reasoning)	prompt mode	No skill wrapper exists — you probe the model directly
A guardrail / constraint your CLAUDE.md documents	prompt mode	You test whether the agent respects documented rules

The two configs, side by side

Both minimal configs below differ in exactly one key.

Skill modePrompt mode

eval.yaml

name: my-skill-eval

execution:
  mode: case
  skill: my-skill          # the artifact under test
  arguments: "{prompt}"    # resolved per case from input.yaml

dataset:
  path: eval/dataset/cases
  schema: "Each case has an input.yaml with a 'prompt' field."

judges:
  - name: output_quality
    prompt: "Score the output 1-5 for completeness and accuracy."

eval.yaml

name: docs-navigation-eval

execution:
  mode: case
  prompt: "{{ input.prompt }}"   # sent directly to the agent

runner:
  workspace_mode: repo           # navigate the real repository

dataset:
  path: eval/dataset/cases
  schema: "Each case has an input.yaml with a 'prompt' field."

judges:
  - name: used_docs
    builtin: consulted_docs

Mutually exclusive — enforced at load time

Setting both execution.skill and execution.prompt raises a ValueError when the config is parsed, not mid-run:

execution.skill and execution.prompt are mutually exclusive.

A top-level skill: is still accepted but deprecated — it is auto-normalized into execution.skill with a warning. Author new configs with execution.skill.

What differs downstream

Almost nothing. The two flavors share the same dataset, judges, thresholds, inputs.tools, outputs, traces, and reward blocks. The differences are:

Aspect	Skill mode	Prompt mode
execution.* key	skill (+ arguments)	prompt
Analyze with	/eval-analyze --skill my-skill	/eval-analyze --prompt <analysis.md>
Default dataset provenance	generation.strategy: skill (agent authors from skill analysis)	often synthetic (LLM generates from seeds)
Run name derives from	the skill name	name / config path
Artifact you iterate on	the skill's SKILL.md	the docs / prompt under test
is_prompt_mode() returns	False	True

How the harness decides

The runner resolves the target through EvalConfig.resolve_skill() — which prefers execution.skill, falls back to the deprecated top-level skill, and returns None for prompt mode. EvalConfig.is_prompt_mode() is True only when execution.prompt is set. All execution substrates (local, Harbor, EvalHub) go through this method, so an execution.skill-only config runs the skill rather than silently degrading to prompt mode.

The review/optimize target is the key difference

The scoring pipeline is identical, but what you change in response to the scores is not. That target flows straight into /eval-review and /eval-optimize.

flowchart TD
    A[eval.yaml] --> B{execution.skill<br/>or execution.prompt?}
    B -->|skill| C[Invoke /my-skill --args]
    B -->|prompt| D[Send prompt to agent]
    C --> E[Score with judges]
    D --> E
    E --> F[/eval-review · /eval-optimize/]
    F -->|skill mode| G[Edit SKILL.md]
    F -->|prompt mode| H[Edit the docs / prompt under test]

• Skill mode: low scores point at the skill implementation. Review and optimize edit the skill's SKILL.md (and its scripts/sub-skills).
• Prompt mode: low scores point at the documentation or prompt the agent consulted. Review and optimize edit the docs under test — the model itself is fixed, so you improve what the agent reads.

Workflow shortcuts

Skill modePrompt mode

/eval-setup
/eval-analyze --skill my-skill      # reads SKILL.md, writes eval.yaml
/eval-dataset
/eval-run --model opus
/eval-review --run-id <id>          # feedback → edit SKILL.md
/eval-optimize --model opus

/eval-setup
/eval-analyze --prompt examples/openshift-agentic-docs.md
/eval-dataset                       # synthetic cases from seeds
/eval-run --model sonnet
/eval-review --run-id <id>          # feedback → edit the docs under test

Where to go next

• The execution model

  ---

  How mode (case/batch) composes with skill/prompt, in depth.

  Execution model

• Agentic-docs eval

  ---

  The flagship prompt-mode flavor: test whether agents can use your docs.

  Agentic docs

• Config reference

  ---

  Every execution.* key, with defaults and validation rules.

  execution · eval.yaml