---
title: "Bare Eval"
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."
---

<span className="badge badge-gray">Reference</span> <span className="badge badge-yellow">medium</span>

> **Auto-activated** — this skill loads automatically when Claude detects matching context.

<ContextualSkillSidebar slug="bare-eval" />


# 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

```bash
# --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) |

### `--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.

```bash
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:

```bash
# 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 &lt;name&gt;` also honors `permissionMode` in `--print` | Permission-gated tools (Bash, Edit) require either `permissionMode: acceptEdits` or explicit allowlists in the agent definition |

Migration test:

```bash
# 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 between runs, engineers chased phantom regressions.

**Fix:** `tests/evals/scripts/lib/eval-common.sh` exports `CLAUDE_CODE_FORK_SUBAGENT=1`, so every script that sources it (run-trigger-eval, run-quality-eval, run-agent-eval, optimize-description, etc.) gets forked graders automatically. The CI workflow `.github/workflows/orchestkit-eval.yml` also sets it at the workflow level. Older CC silently ignores the env var (no-op).

**Determinism contract:** running the same grader on the same fixture twice in a row produces the **same score**. Verified by `tests/evals/scripts/test-grader-determinism.sh`.

## Performance

| Scenario | Without --bare | With --bare | Savings |
|----------|---------------|-------------|---------|
| Single grading call | ~3-5s startup | ~0.5-1s | 2-4x |
| Trigger (per prompt) | ~3-5s | ~0.5-1s | 2-4x |
| Full eval (50 calls) | ~150-250s overhead | ~25-50s | 3-5x |

## Rules

```
Read("${CLAUDE_SKILL_DIR}/rules/_sections.md")
```

## Troubleshooting

```
Read("${CLAUDE_SKILL_DIR}/references/troubleshooting.md")
```

## Related

- `eval:skill` npm script — unified skill evaluation runner
- `eval:trigger` — trigger accuracy testing
- `eval:quality` — A/B quality comparison
- `optimize-description.sh` — iterative description improvement
- Version compatibility: `doctor/references/version-compatibility.md`


---

## Rules (3)

### Use --bare for grading/classification only — MEDIUM


# Use --bare for Grading/Classification Only

`--bare` should only be used for calls that don't need plugin context.

## Bare-Safe Calls

- Assertion grading (batch or per-assertion)
- Trigger classification (skill matching)
- Description optimization
- Force-skill eval (`--append-system-prompt`)
- Baseline comparison (no plugin)

## Never-Bare Calls

- `run_with_skill` — tests plugin routing and skill loading
- Agent eval generation — tests agent spawning via plugin
- Any call using `--plugin-dir`

## Incorrect

```bash
# BAD: run_with_skill with --bare defeats the purpose of testing plugin routing
build_claude_flags() {
    flags+=(--bare)  # Wrong — this function is called with include_plugin=true
    flags+=(--plugin-dir "$PLUGIN_DIR")
}
```

## Correct

```bash
# GOOD: only add --bare when NOT using plugins
build_claude_flags() {
    local include_plugin="$1"
    if [[ "$include_plugin" == "true" ]]; then
        flags+=(--plugin-dir "$PLUGIN_DIR")
    elif [[ "$BARE_MODE" == "true" ]]; then
        flags+=(--bare)
    fi
}
```

## Why

The eval pipeline's value comes from testing skills in their real environment. `--bare` is for the grading/classification overhead calls, not the core eval itself.


### Never combine --bare with --plugin-dir — HIGH


# Never Combine --bare with --plugin-dir

`--bare` explicitly skips plugin sync and skill directory walks. Adding `--plugin-dir` alongside it creates a silent conflict — the plugin may not load correctly.

## Incorrect

```bash
# BAD: --bare + --plugin-dir is contradictory
claude -p "$prompt" --bare --plugin-dir plugins/ork --output-format json
```

## Correct

```bash
# For plugin-routed tests: no --bare
claude -p "$prompt" --plugin-dir plugins/ork --dangerously-skip-permissions --output-format json

# For grading/classification: --bare, no --plugin-dir
claude -p "$prompt" --bare --max-turns 1 --output-format text
```

## Why

The `--bare` flag was designed for scripted `-p` calls that don't need the full Claude Code environment. Using it with `--plugin-dir` defeats the purpose and may cause unpredictable behavior since hooks and skill discovery are disabled.


### Always check ANTHROPIC_API_KEY before using --bare — HIGH


# Always Check ANTHROPIC_API_KEY Before --bare

`--bare` disables OAuth and keychain auth. If `ANTHROPIC_API_KEY` is not set, the call will fail.

## Incorrect

```bash
# BAD: no API key check before --bare
claude -p "$prompt" --bare --max-turns 1 --output-format text
```

## Correct

```bash
# GOOD: conditional bare mode
BARE_MODE=false
if [[ -n "${ANTHROPIC_API_KEY:-}" ]]; then
    BARE_MODE=true
fi

local -a bare_flag=()
if [[ "$BARE_MODE" == "true" ]]; then bare_flag=(--bare); fi

claude -p "$prompt" "${bare_flag[@]}" --max-turns 1 --output-format text
```

## Why

Users authenticating via `claude auth login` (OAuth) or macOS keychain won't have `ANTHROPIC_API_KEY` set. Using `--bare` unconditionally would break their eval pipeline. The conditional pattern degrades gracefully — eval still works, just slower.



---

## References (3)

### Grading Schemas

# Grading Schemas

JSON schemas for structured eval output with `--json-schema`.

## Batch Assertion Grading

```json
{
  "type": "array",
  "items": {
    "type": "object",
    "properties": {
      "name": { "type": "string", "description": "Assertion name" },
      "verdict": { "enum": ["PASS", "FAIL"], "description": "Whether the output satisfies the assertion" },
      "reason": { "type": "string", "description": "One-line explanation" }
    },
    "required": ["name", "verdict", "reason"]
  }
}
```

## Trigger Classification

```json
{
  "type": "object",
  "properties": {
    "skill_name": { "type": "string", "description": "The skill that would be triggered" },
    "confidence": { "type": "number", "minimum": 0, "maximum": 1, "description": "Confidence score 0-1" },
    "reasoning": { "type": "string", "description": "Why this skill matches" }
  },
  "required": ["skill_name", "confidence"]
}
```

## Quality Score

```json
{
  "type": "object",
  "properties": {
    "score": { "type": "integer", "minimum": 0, "maximum": 10 },
    "dimensions": {
      "type": "object",
      "properties": {
        "accuracy": { "type": "integer", "minimum": 0, "maximum": 10 },
        "completeness": { "type": "integer", "minimum": 0, "maximum": 10 },
        "actionability": { "type": "integer", "minimum": 0, "maximum": 10 },
        "format": { "type": "integer", "minimum": 0, "maximum": 10 }
      }
    },
    "verdict": { "enum": ["PASS", "FAIL", "PARTIAL"] },
    "reason": { "type": "string" }
  },
  "required": ["score", "verdict"]
}
```

## Description Quality

For `optimize-description.sh` iterations:

```json
{
  "type": "object",
  "properties": {
    "improved_description": { "type": "string", "maxLength": 1024 },
    "changes_made": {
      "type": "array",
      "items": { "type": "string" }
    },
    "trigger_keywords_added": {
      "type": "array",
      "items": { "type": "string" }
    }
  },
  "required": ["improved_description"]
}
```

## Usage

```bash
# Save schema to file
cat > /tmp/grading-schema.json << 'EOF'
{ ... schema above ... }
EOF

# Use with --json-schema
claude -p "$prompt" --bare --json-schema /tmp/grading-schema.json --output-format json
```


### Invocation Patterns

# Bare Eval Invocation Patterns

Detailed patterns for each `--bare` eval scenario.

## 1. Batch Grading (Most Common)

Grade all assertions for an output in a single call:

```bash
grading_prompt="You are an assertion grader. Grade this output against EACH assertion.
For each, return: {\"name\": \"...\", \"verdict\": \"PASS\"|\"FAIL\", \"reason\": \"...\"}
Return ONLY a valid JSON array.

ASSERTIONS:
$assertions_json

OUTPUT:
$output_text"

result=$(claude -p "$grading_prompt" --bare --max-turns 1 --output-format text)
```

### Fallback: Per-Assertion Grading

If batch fails (malformed JSON), fall back to grading one assertion at a time.

> **CC 2.1.88 note**: The StructuredOutput schema cache bug that caused ~50% failure
> rate with multiple schemas has been fixed. Schema failures are now exceptional.
> If you see repeated failures, investigate the prompt/schema rather than assuming
> cache corruption.

```bash
grading_prompt="Grade this output against the assertion.
Output ONLY 'PASS' or 'FAIL' followed by a one-line reason.

ASSERTION: $assertion_check

OUTPUT:
$output_text"

result=$(claude -p "$grading_prompt" --bare --max-turns 1 --output-format text)
```

## 2. Trigger Classification

Test which skill a prompt would match:

```bash
classification_prompt="Which skill would be triggered by this user prompt: \"$prompt\"

Available skills:
$SKILLS_CATALOG"

claude -p "$classification_prompt" \
    --bare \
    --system-prompt "$CLASSIFIER_SYSTEM_PROMPT" \
    --output-format json \
    --json-schema "$TRIGGER_SCHEMA" \
    --max-turns 2
```

### Repetition for Confidence

Run multiple reps and check consistency:

```bash
for ((i=1; i<=reps; i++)); do
    result=$(claude -p "$prompt" --bare --json-schema "$schema" --output-format json)
    # Parse and aggregate
done
```

## 3. Description Optimization

Iteratively improve a skill description for better trigger accuracy:

```bash
improve_prompt="Current description: $current_desc

These prompts SHOULD trigger but DIDN'T:
$failures

Rules:
- Under 200 words
- Include WHAT and WHEN
- Third person
- Specific trigger keywords

Output ONLY the improved description."

new_desc=$(echo "$improve_prompt" | claude -p --bare --max-turns 1 --output-format text)
```

## 4. Force-Skill Eval (Isolated Quality)

Test skill content quality without plugin routing — inject SKILL.md body directly:

```bash
# Strip YAML frontmatter (macOS-compatible)
skill_content=$(awk 'BEGIN{skip=0} /^---$/{skip++; next} skip>=2{print}' "$SKILL_PATH")

claude -p "$prompt" \
    --bare \
    --print \
    --no-session-persistence \
    --max-budget-usd 0.50 \
    --append-system-prompt "$skill_content"
```

**Key:** `--print` forces text-only output (no tool calls). Combined with `--bare`, this is the fastest eval mode — pure text generation with skill context.

## 5. Baseline Comparison

Run without any skill context for A/B comparison:

```bash
claude -p "$prompt" \
    --bare \
    --dangerously-skip-permissions \
    --max-turns 3 \
    --output-format json \
    --json-schema "$QUALITY_SCHEMA" \
    --no-session-persistence \
    --max-budget-usd 0.50
```

> **CC 2.1.88**: The `--json-schema` flag is now safe to use with multiple schemas
> in a single session. The StructuredOutput schema cache bug (~50% failure rate)
> has been fixed. You can safely chain `--json-schema` calls across batch grading,
> trigger classification, quality scoring, and baseline comparison.

## Flag Compatibility Matrix

| Flag | Compatible with --bare? | Notes |
|------|------------------------|-------|
| `--max-turns` | Yes | Limits turn count |
| `--output-format` | Yes | json, text, stream-json |
| `--json-schema` | Yes | Structured output |
| `--system-prompt` | Yes | Override system prompt |
| `--append-system-prompt` | Yes | Append to system prompt |
| `--print` | Yes | Text-only, no tools |
| `--no-session-persistence` | Yes | No session file |
| `--max-budget-usd` | Yes | Cost cap |
| `--model` | Yes | Model override |
| `--plugin-dir` | **No** | Contradicts --bare |
| `--mcp-config` | Check | MCP may need network |
| `--dangerously-skip-permissions` | Yes | Useful for CI |
| `--settings` | Yes | Custom settings file |

## Timeout Wrapper

Use a portable timeout for CI environments:

```bash
# eval-common.sh provides run_with_timeout()
run_with_timeout 120 claude -p "$prompt" --bare --max-turns 1 --output-format text
```


### Troubleshooting

# Bare Eval Troubleshooting

## Common Errors

| Error | Cause | Fix |
|-------|-------|-----|
| `--bare requires ANTHROPIC_API_KEY` | OAuth/keychain not supported in bare mode | Set `ANTHROPIC_API_KEY` env var |
| `Unknown flag --bare` | CC version &lt; 2.1.81 | Upgrade: `npm i -g @anthropic-ai/claude-code@latest` |
| Empty response | Model returned empty or budget exceeded | Increase `--max-budget-usd` or check prompt |
| Malformed JSON from batch grader | Model wrapped JSON in markdown fences | Strip fences: `sed 's/^```json//;s/^```//;s/```$//'` |
| `BARE_MODE=false` despite key set | `ANTHROPIC_API_KEY` empty string | Ensure key has a value: `echo $ANTHROPIC_API_KEY` |
| Timeout in CI | Model taking too long | Use `run_with_timeout` with adequate seconds |

## Debugging

### Check if bare mode is active

```bash
# In eval scripts:
echo "BARE_MODE=$BARE_MODE"

# Manual test:
ANTHROPIC_API_KEY="$ANTHROPIC_API_KEY" claude -p "Hello" --bare --max-turns 1 --output-format text
```

### Verbose output

```bash
# Capture stderr for diagnostics
claude -p "$prompt" --bare --max-turns 1 --output-format text > output.txt 2> stderr.txt
cat stderr.txt
```

### Fallback when --bare unavailable

If CC &lt; 2.1.81, the eval scripts still work — they just don't add `--bare`:

```bash
# eval-common.sh:
BARE_MODE=false  # No ANTHROPIC_API_KEY → no bare mode
# Scripts run normally, just slower (full plugin/hook overhead)
```

## Performance Profiling

Compare eval times with and without bare:

```bash
# With bare
time ANTHROPIC_API_KEY="$KEY" claude -p "test" --bare --max-turns 1 --output-format text > /dev/null

# Without bare (full stack)
time claude -p "test" --max-turns 1 --output-format text > /dev/null
```

## Security Notes

- `--bare` disables auto-memory — no session learnings stored
- `--bare` requires explicit API key — no credential leakage via keychain
- Eval scripts already run outside Claude Code sessions (`unset CLAUDECODE`)
- `SKILL_NAME_RE` regex prevents path traversal in eval inputs (SEC-001)

