Fan-Out and Fan-In
Splitting work across parallel workers and recombining their results.
Fan-out and fan-in — also called scatter–gather — is the pattern of dividing a task into independent pieces, processing them concurrently, and combining the results. It is the oldest parallelism shape there is, and it applies unchanged to fleets of model instances.
The design decision that matters most is whether the recombination is a barrier. A barrier waits for every worker before anything proceeds, which is correct when the next stage genuinely needs the whole set — deduplicating across all results, deciding whether to continue at all, comparing findings against one another. When the next stage only needs one item's result, a barrier is pure waste: total time becomes the slowest worker in each stage summed, rather than the slowest single chain. Streaming each item through its stages independently is usually the better default.
The second decision is width. Parallelism trades wall-clock time for peak resource consumption, and the resource is frequently shared: concurrent test suites starve each other of processor time, concurrent builds exhaust disk, concurrent model workers consume a shared spending limit. Wide fan-outs fail in ways narrow ones do not, and the failures look like defects rather than contention. See Resource Starvation and Token Budget.
Silent truncation is the last hazard: if a fan-out caps coverage, say so, or a partial sweep reads as a complete one.
See also4
Hand-picked in the note itself — the neighbours worth reading next.
Multi-Agent Orchestration
Coordinating several model instances on one body of work, each with its own context.
Agents & Language Models10 connections
Subagent
A model instance spawned by another to handle a scoped task with its own context.
Agents & Language Models11 connections
Race Condition
A defect whose occurrence depends on the relative timing of concurrent operations.
Testing & Verification11 connections
Exhaustive Claim
A statement of the form "the last one" or "nothing else does this" — load-bearing, and only as good as the search behind it.
Method13 connections
Related3
Nearby in the graph rather than deliberately chosen. Looser, sometimes surprising.
Linked from6
Notes elsewhere in the wiki that reach for this one.
- Git WorktreeVersion Control & Delivery
An additional working directory attached to one repository, each on its own branch.
- Multi-Agent OrchestrationAgents & Language Models
Coordinating several model instances on one body of work, each with its own context.
- Race ConditionTesting & Verification
A defect whose occurrence depends on the relative timing of concurrent operations.
- Resource StarvationTesting & Verification
Failures caused by competition for a finite shared resource rather than by any defect.
- SubagentAgents & Language Models
A model instance spawned by another to handle a scoped task with its own context.
- Token BudgetAgents & Language Models
The finite allowance of model usage a task may consume, and the design decisions it forces.