Ablation Planner

Systematically design ablation studies that answer the questions reviewers will ask. The external LLM reviewer leads the design (reviewer perspective), CC reviews feasibility and implements.

Context: $ARGUMENTS

When to Use

• Main results pass /result-to-claim with claim_supported = yes or partial
• User explicitly requests ablation planning
• /auto-iteration-loop reviewer identifies missing ablations

Reviewer LLM Configuration (mandatory, read first)

This skill calls an external LLM reviewer. Never hardcode a model name and never read the reviewer model from task.md / project READMEs / source comments. Project-level files may list available API keys for unrelated purposes (e.g., LLM-as-judge inside experiment code); those are not the reviewer config.

Resolve LLM_MODEL, LLM_BASE_URL, LLM_API_KEY strictly in this priority order before any reviewer call:

1. Project MCP config — ${PROJECT_ROOT}/.mcp.json, field mcpServers["llm-chat"].env.{LLM_MODEL,LLM_BASE_URL,LLM_API_KEY}.
2. User MCP config — ~/.claude/settings.json, same field.
3. Shell environment — $LLM_MODEL, $LLM_BASE_URL, $LLM_API_KEY.

Pre-flight check (run before Step 2, mandatory)

LLM_MODEL_SRC=""
if [ -f .mcp.json ] && jq -e '.mcpServers["llm-chat"].env.LLM_MODEL' .mcp.json >/dev/null 2>&1 ; then
  export LLM_MODEL=$(jq -r '.mcpServers["llm-chat"].env.LLM_MODEL' .mcp.json)
  export LLM_BASE_URL=$(jq -r '.mcpServers["llm-chat"].env.LLM_BASE_URL' .mcp.json)
  export LLM_API_KEY=$(jq -r '.mcpServers["llm-chat"].env.LLM_API_KEY' .mcp.json)
  LLM_MODEL_SRC="project .mcp.json"
elif [ -f ~/.claude/settings.json ] && jq -e '.mcpServers["llm-chat"].env.LLM_MODEL' ~/.claude/settings.json >/dev/null 2>&1 ; then
  export LLM_MODEL=$(jq -r '.mcpServers["llm-chat"].env.LLM_MODEL' ~/.claude/settings.json)
  export LLM_BASE_URL=$(jq -r '.mcpServers["llm-chat"].env.LLM_BASE_URL' ~/.claude/settings.json)
  export LLM_API_KEY=$(jq -r '.mcpServers["llm-chat"].env.LLM_API_KEY' ~/.claude/settings.json)
  LLM_MODEL_SRC="user ~/.claude/settings.json"
elif [ -n "$LLM_MODEL" ] && [ -n "$LLM_BASE_URL" ] && [ -n "$LLM_API_KEY" ] ; then
  LLM_MODEL_SRC="shell env"
fi
echo "[reviewer-config] LLM_MODEL=$LLM_MODEL  LLM_BASE_URL=$LLM_BASE_URL  source=$LLM_MODEL_SRC"

Hard-fail rule: If LLM_MODEL is empty after this resolution (none of the three sources provides it), the skill MUST abort with:

"Reviewer model not configured. Add mcpServers.llm-chat.env.{LLM_MODEL,LLM_BASE_URL,LLM_API_KEY} to .mcp.json (project) or ~/.claude/settings.json (user)."

Do not guess a default. Do not fall back to a model name read from task.md or any other project file.

Workflow

Step 1: Prepare Context

CC reads available project files to build the full picture:

• Method description and components (from docs/research_contract.md or project CLAUDE.md)
• Current experiment results (from EXPERIMENT_LOG.md, EXPERIMENT_TRACKER.md, or W&B)
• Confirmed and intended claims (from result-to-claim output or project notes)
• Available compute resources (from CLAUDE.md server config, if present)

Step 2: External LLM Reviewer Designs Ablations

Always ask the external reviewer for strict, high-rigor feedback.

mcp__llm-chat__chat:
  prompt: |
    You are a rigorous ML reviewer planning ablation studies.
    Given this method and results, design ablations that:

    1. Isolate the contribution of each novel component
    2. Answer questions reviewers will definitely ask
    3. Test sensitivity to key hyperparameters
    4. Compare against natural alternative design choices

    Method: [description from project files]
    Components: [list of removable/replaceable components]
    Current results: [key metrics from experiments]
    Claims: [what we claim and current evidence]

    For each ablation, specify:
    - name: what to change (e.g., "remove module X", "replace Y with Z")
    - what_it_tests: the specific question this answers
    - expected_if_component_matters: what we predict if the component is important
    - priority: 1 (must-run) to 5 (nice-to-have)

    Also provide:
    - coverage_assessment: what reviewer questions these ablations answer
    - unnecessary_ablations: experiments that seem useful but won't add insight
    - suggested_order: run order optimized for maximum early information
    - estimated_compute: total GPU-hours estimate

Step 3: Parse Ablation Plan

Normalize the reviewer's response into structured format:

## Ablation Plan

### Component Ablations (highest priority)
| # | Name | What It Tests | Expected If Matters | Priority |
|---|------|---------------|---------------------|----------|
| 1 | remove module X | contribution of X | performance drops on metric Y | 1 |
| 2 | replace X with simpler Z | value of learned vs fixed | drops, especially on dataset A | 2 |

### Hyperparameter Sensitivity
| # | Parameter | Values to Test | What It Tests | Priority |
|---|-----------|---------------|---------------|----------|
| 3 | lambda | [0.01, 0.1, 1.0] | sensitivity to regularization | 3 |

### Design Choice Comparisons
| # | Name | What It Tests | Priority |
|---|------|---------------|----------|
| 4 | joint vs separate matching | whether joint adds value | 4 |

### Coverage Assessment
[What reviewer questions these ablations answer]

### Unnecessary Ablations
[Experiments that seem useful but won't add insight — skip these]

### Run Order
[Optimized for maximum early information]

### Estimated Compute
[Total GPU-hours]

Step 4: CC Reviews Feasibility

Before running anything, CC checks:

• Compute budget: can we afford all ablations with available GPUs?
• Code changes: which ablations need code modifications vs config-only changes?
• Dependencies: which ablations can run in parallel?
• Cuts: if budget is tight, propose removing lower-priority ablations and ask the external reviewer to confirm

Step 5: Implement and Run

1. Create configs/scripts for each ablation (config-only changes first)
2. Smoke test each ablation before full run
3. Run in suggested order, using descriptive names (e.g., ablation-no-module-X)
4. Track results in EXPERIMENT_LOG.md
5. After all ablations complete → update findings.md with insights

Rules

• The external LLM reviewer leads the design. CC does not pre-filter or bias the ablation list before the reviewer sees it. The reviewer thinks like a reviewer; CC thinks like an engineer.
• Every ablation must have a clear what_it_tests and expected_if_component_matters. No "just try it" experiments.
• Config-only ablations take priority over those needing code changes (faster, less error-prone).
• If total compute exceeds budget, CC proposes cuts and asks the external reviewer to re-prioritize — don't silently drop ablations.
• Component ablations (remove/replace) take priority over hyperparameter sweeps.
• Do not generate ablations for components identical to the baseline (no-op ablations).
• Record all ablation results in EXPERIMENT_LOG.md, including negative results (component removal had no effect = important finding).