Exp Lens Unit Interference

Unit Interference Experimental Design Lens

Philosophical Mode: Causal-Structural Primary Question: "What is the unit, and can treatments spill over?" Focus: Experimental Unit, Cluster Structure, Shared Resources, Network Effects, SUTVA Violations

Arguments

/autoskillit:exp-lens-unit-interference [context_path] [experiment_plan_path]

• context_path (optional positional arg 1) — Absolute path to a lens context file containing IV/DV tables, H0/H1 hypotheses, controlled variables, and success criteria. If provided, read this file before beginning analysis to obtain structured context. If omitted, discover context by exploring the CWD.
• experiment_plan_path (optional positional arg 2) — Absolute path to the full experiment plan. If provided, read for complete experimental methodology and design. If omitted, locate the experiment plan by exploring the CWD.

When to Use

• Online A/B tests with shared infrastructure
• Distributed systems where units share caches, queues, or services
• Social or network experiments where units are connected
• User invokes /autoskillit:exp-lens-unit-interference or /autoskillit:make-experiment-diag unit

Critical Constraints

NEVER:

• Modify any source code files
• Do not litter the codebase with useless comments, TODO markers, or explanatory annotations — the skill output and diagram speak for themselves
• Create files outside {{AUTOSKILLIT_TEMP}}/exp-lens-unit-interference/
• Run subagents in the background (run_in_background: true is prohibited)

ALWAYS:

• Focus on the unit definition and whether SUTVA is plausible

• Map the full unit-cluster-resource hierarchy before assessing interference

• Identify every shared resource that could transmit treatment effects across groups

• Distinguish direct spillover (shared cache) from indirect spillover (market equilibrium)

• BEFORE creating any diagram, LOAD the /autoskillit:mermaid skill using the Skill tool - this is MANDATORY

• If the Skill tool cannot be used (disable-model-invocation) or refuses this invocation, do NOT proceed with diagram creation. Abort this step and omit the diagram from output.

• Write output to {{AUTOSKILLIT_TEMP}}/exp-lens-unit-interference/exp_diag_unit_interference_{YYYY-MM-DD_HHMMSS}.md

• After writing the file, emit the structured output token as literal plain text with no markdown formatting on the token name (the adjudicator performs a regex match):

  diagram_path = /absolute/path/to/{{AUTOSKILLIT_TEMP}}/exp-lens-unit-interference/exp_diag_unit_interference_{...}.md
  

Analysis Workflow

Step 0: Parse optional arguments

If positional arg 1 (context_path) is provided and the file exists, read it to obtain IV/DV tables, H0/H1 hypotheses, controlled variables, and success criteria. If positional arg 2 (experiment_plan_path) is provided and exists, read the experiment plan for full methodology. Use this structured context as the foundation for Steps 1-5; skip the CWD exploration for these fields if the context file supplies them.

Step 1: Launch Parallel Exploration Subagents

Spawn Explore subagents to investigate:

Unit Definition

• Find what constitutes one experimental unit
• Is it a user, request, session, query, item, sample, trial, or instance?
• Look for: user, request, session, query, item, sample, trial, instance

Cluster & Group Structure

• Find groupings of units that might share treatment effects
• Identify natural clustering that predates treatment assignment
• Look for: cluster, group, shard, server, region, batch, household, team

Shared Resources

• Find infrastructure shared across treatment groups
• Identify components both treatment and control units touch
• Look for: cache, queue, pool, database, service, load_balancer, gpu, memory

Network & Social Connections

• Find connections between units that could transmit treatment effects
• Identify paths by which a treated unit could alter a control unit's experience
• Look for: network, graph, friend, neighbor, link, message, recommend, influence

Treatment Assignment Boundary

• Find where the treatment boundary is drawn
• Identify whether the assignment is at the unit level or a coarser level
• Look for: bucket, hash, experiment_id, variant, flag, feature_flag, rollout

Step 2: Map the Unit-Cluster-Resource Hierarchy

For each level of the hierarchy:

• Can treatment at one level affect outcomes at another?
• Identify specific spillover pathways between levels
• Assess whether SUTVA (stable unit treatment value assumption) is plausible at each level

Document:

• Unit Level: The atomic entity receiving treatment
• Cluster Level: Natural groupings of units with shared context
• System Level: Infrastructure shared across all groups

Step 3: Analyze Interference Pathways

CRITICAL — Analyze Interference Pathways: For every shared resource or connection:

• Could treatment group A's behavior change the experience of control group B?
• Is this interference direct (shared cache hit rates) or indirect (market-level equilibrium effects)?
• What is the likely magnitude: negligible, moderate, or invalidating?
• Is there a mitigation strategy (cluster-level randomization, holdout, depletion correction)?

Rate each pathway:

• HIGH: Interference almost certainly contaminates the control group
• MEDIUM: Plausible interference under realistic usage patterns
• LOW: Theoretical but unlikely to affect measured outcomes

Step 4: Create the Diagram

Use flowchart with:

Direction: TB (units nested within clusters nested within the system)

Subgraphs:

• "EXPERIMENTAL UNITS" (the atomic entities being randomized)
• "CLUSTER STRUCTURE" (groupings above the unit level)
• "SHARED RESOURCES" (infrastructure accessible by both groups)
• "INTERFERENCE PATHWAYS" (explicit spillover routes)

Node Styling:

• cli class: Experimental units
• phase class: Cluster / group nodes
• stateNode class: Shared resources
• gap class: Interference pathways
• handler class: Treatment assignment
• detector class: SUTVA boundary

Step 5: Write Output

Write the diagram to: {{AUTOSKILLIT_TEMP}}/exp-lens-unit-interference/exp_diag_unit_interference_{YYYY-MM-DD_HHMMSS}.md (relative to the current working directory)

Pre-Diagram Checklist

Before creating the diagram, verify:

• LOADED /autoskillit:mermaid skill using the Skill tool
• Using ONLY classDef styles from the mermaid skill (no invented colors)
• Diagram will include a color legend table

Related Skills

• /autoskillit:make-experiment-diag - Parent skill for experimental lens selection
• /autoskillit:mermaid - MUST BE LOADED before creating diagram
• /autoskillit:exp-lens-causal-assumptions - For DAG-level causal structure analysis
• /autoskillit:exp-lens-randomization-blocking - For randomization strategy and blocking design