/bare-eval

name: bare-eval
compatibility: "Claude Code 2.1.220+"
description: "Run isolated eval and grading calls using CC 2.1.81 --bare mode. Constructs claude -p --bare invocations for skill evaluation, trigger testing, and LLM grading without plugin/hook interference. Use when running eval pipelines, grading skill outputs, benchmarking prompt quality, or testing trigger accuracy in isolation."
tags: [eval, bare, grading, pipeline, testing, ci]
version: 1.1.0
author: OrchestKit
user-invocable: false
complexity: medium
context: inherit
persuasion-type: discipline
effort: low

Bare Eval — Isolated Evaluation Calls

Run `claude -p --bare` for fast, clean eval/grading without plugin overhead.

**CC 2.1.81 required.** The `--bare` flag skips hooks, LSP, plugin sync, and skill directory walks.

When to Use

• Grading skill outputs against assertions
• Trigger classification (which skill matches a prompt)
• Description optimization iterations
• Any scripted `-p` call that doesn't need plugins

When NOT to Use

• Testing skill routing (needs `--plugin-dir`)
• Testing agent orchestration (needs full plugin context)
• Interactive sessions

Prerequisites

# --bare requires ANTHROPIC_API_KEY (OAuth/keychain disabled)
export ANTHROPIC_API_KEY="sk-ant-..."

# Verify CC version
claude --version  # Must be >= 2.1.81

Quick Reference

| Call Type | Command Pattern | |-----------|----------------| | Grading | `claude -p "$prompt" --bare --max-turns 1 --output-format text` | | Trigger | `claude -p "$prompt" --bare --json-schema "$schema" --output-format json` | | Streaming grade | `claude -p "$prompt" --bare --max-turns 1 --output-format stream-json` | | Optimize | `echo "$prompt" \| claude -p --bare --max-turns 1 --output-format text` | | Force-skill | `claude -p "$prompt" --bare --print --append-system-prompt "$content"` | | @-file in prompt | `claude -p "grade @fixtures/case-1.md against rubric" --bare` (CC 2.1.113 Remote Control autocomplete) |

> **Long harness runs (CC 2.1.199+):** set `CLAUDE_CODE_RETRY_WATCHDOG=1` for unattended eval batches — it raises the default retry count for non-capacity transient errors to 300 and lifts the cap of 15 on `CLAUDE_CODE_MAX_RETRIES`, so an overnight grading run survives transient API blips instead of dying mid-batch.

`--output-format stream-json`

Newline-delimited JSON events (one per token/tool-call) — lets a runner score partial output or abort early on a failing probe without waiting for the full response.

claude -p "$prompt" --bare --max-turns 1 --output-format stream-json \
  | while IFS= read -r line; do
      # line is a single JSON event; inspect $.type == "content_block_delta"
      jq -r 'select(.type == "content_block_delta") | .delta.text' <<< "$line"
    done

Use `stream-json` over `json` when:

• grading long outputs and you want incremental scoring,
• piping into another CLI step-by-step (e.g. `ork:eval-runner`),
• you need per-token timing data alongside the content.

Invocation Patterns

Load detailed patterns and examples:

Read("${CLAUDE_SKILL_DIR}/references/invocation-patterns.md")

Grading Schemas

JSON schemas for structured eval output:

Read("${CLAUDE_SKILL_DIR}/references/grading-schemas.md")

Pipeline Integration

OrchestKit's eval scripts (`npm run eval:skill`) auto-detect bare mode:

# eval-common.sh detects ANTHROPIC_API_KEY → sets BARE_MODE=true
# Scripts add --bare to all non-plugin calls automatically

**Bare calls:** Trigger classification, force-skill, baseline, all grading. **Never bare:** `run_with_skill` (needs plugin context for routing tests).

CC 2.1.119: `--print` honors agent `tools:` / `disallowedTools:` (M122)

Before CC 2.1.119, `--print` mode ran with the full default tool set regardless of the agent's frontmatter `tools:` and `disallowedTools:`. Bare-eval grading was effectively ungated — graders could call any tool they wanted, even if the agent definition restricted them.

**As of 2.1.119, `--print` enforces the agent's declared tool surface.** Implications for eval design:

| Consequence | Action | |---|---| | Eval graders that relied on unrestricted tool access may now fail | Audit grader prompts for tools they actually need; whitelist explicitly via the agent's `tools:` frontmatter | | Eval results match interactive runs | Reproducibility improves — grading what the model can actually do, not what it could do in an unsandboxed `--print` | | `--agent <name>` also honors `permissionMode` in `--print` | Permission-gated tools (Bash, Edit) require either `permissionMode: acceptEdits` or explicit allowlists in the agent definition |

Migration test:

# Run an eval against an agent with a deliberately tight tools: list.
# Graders that previously called Read/Bash freely will now fail unless those
# tools are declared on the agent.
claude -p "$prompt" --bare --print --agent grader-test

If the grader fails with a "tool not permitted" error, add the required tool to the agent's `tools:` frontmatter and re-run.

CC 2.1.121: `CLAUDE_CODE_FORK_SUBAGENT=1` for grader determinism (#1545)

Before CC 2.1.121, the env var only worked in interactive sessions. As of 2.1.121, **non-interactive paths (`claude -p`, SDK) honor it too** — each grader invocation gets a fresh forked subagent context.

**The cross-eval state-leak problem this fixes:**

Without forking, sequential `claude -p --bare` graders inherit harness state:

| Inherited | Symptom | |---|---| | memory MCP query cache | grader sees stale hit from previous run; same fixture grades differently | | `.claude/chain/*.json` on disk | grader for "implement" thinks "explore" already ran (file is from previous test) | | ToolSearch deferred-tool cache | first grader's MCP loads bleed into next grader's tool registry | | model picker pref | grader N inherits `--model=opus` from grader N-1 |

This produced ~5–10% retry rate and non-reproducible scores — the eval baseline drifted