---
name: ensemble-synthesizer
kind: pattern
version: 0.15.0
---

# Ensemble-Synthesizer

K services work independently on the same task. A synthesizer merges by reasoning about disagreements.

### Description

Fans out the same task to K independent services and synthesizes their results by reasoning about disagreements.

### Metadata

- `version`: 0.1.0

### Slots

- `ensemble_member` (primary)
- `synthesizer`

### Config

- `ensemble_size` (integer, default: 3): Number of independent ensemble members to run

### Invariants

- All ensemble members receive the identical brief
- Synthesizer reasons about disagreements — it does not majority-vote
- Ensemble members are unaware of each other

### Shape

- `self`: fan out to K ensemble members, collect results, delegate to synthesizer
- `delegates`:
  - `ensemble_member`: produce a result given the brief — run K times
  - `synthesizer`: merge K results by reasoning about disagreements
- `prohibited`: none

### Parameters

- Pattern instance receives:
    ensemble_member: string   -- responsibility or function name for each ensemble member
    synthesizer: string       -- responsibility or function name for the synthesizer
    task_brief: string        -- the task (same brief goes to all members)
    ensemble_size: number     -- (optional, default 3)

### Returns

- `result`: the synthesis, plus a confidence assessment
- `member_results`: the K individual results

The synthesis is produced by a synthesizer that received all K member results — each member having independently received the SAME brief — and reasoned about WHY the results differ rather than majority-voting, treating disagreement as signal about ambiguity or difficulty.

### Delegation

```prose
let member_results = parallel repeat ensemble_size:
  call ensemble_member
    task_brief: task_brief

let result = call synthesizer
  task_brief: task_brief
  member_results: member_results
  prompt: "Synthesize by reasoning about agreement, disagreement, and confidence; do not majority-vote."

return {
  result: result,
  member_results: member_results
}
```

### Notes

This is a seed pattern. Ensemble members do not know other services are working on the same task. The synthesizer does not know it is part of an ensemble pattern. Disagreement between members is the primary signal — it reveals ambiguity in the task, not errors in individual services.