Orchestration

Scope: covers multi-agent workflow design. For individual agent authoring, see [[writing-agents]]. For plugin architecture, see [[writing-plugins]].

1. Four Orchestration Patterns

Pattern A: Parallel Dispatch

Multiple agents run simultaneously on independent work. A command dispatches them via the Task tool and synthesizes results.

Command dispatches via Task:
  |-- agent-1 (analyzes security)
  |-- agent-2 (analyzes performance)
  |-- agent-3 (analyzes architecture)
  --> Command synthesizes all results into final report

Use when: agents don't depend on each other's output.

Real examples:

• grill plugin: 6 review agents analyze code from different angles in parallel
• docs-guardian: 4 agents (staleness, accuracy, coverage, quality) run simultaneously

Implementation pattern in command body:

## Execution
1. Dispatch the following agents in parallel using Task:
   - security-agent: analyze for vulnerabilities
   - performance-agent: analyze for bottlenecks
   - architecture-agent: analyze for structural issues
2. Collect all agent outputs
3. Synthesize into a unified report with cross-references

Key decisions:

Decision	Recommendation
Max parallel agents	6 (diminishing returns above this)
Timeout per agent	120 seconds for sonnet, 300 for opus
Failure handling	Continue with other agents if one fails
Result merging	Deduplicate findings that appear in multiple agents

Pattern B: Sequential Pipeline

Each stage feeds into the next. Output of stage N is input to stage N+1.

parse --> chunk --> summarize --> QC --> output

Use when: each stage depends on the previous stage's output.

Real examples:

• reading-assistant: parse PDF -> chunk content -> summarize chunks -> QC summaries -> output
• tdd-guardian: discover tests -> run tests -> check coverage -> analyze failures -> report -> enforce

Implementation pattern:

## Execution
### Phase 1: Parse (haiku)
1. Scan input files
2. Extract structured content
3. Output: parsed data as JSON

### Phase 2: Process (sonnet)
4. Receive parsed data from Phase 1
5. Analyze and transform
6. Output: processed results

### Phase 3: QC (sonnet)
7. Verify Phase 2 output meets quality bar
8. Output: pass/warn/fail verdict

### Phase 4: Output
9. If QC passed: format and deliver final report
10. If QC failed: report failures and stop

Key decisions:

Decision	Recommendation
Phase boundary	Each phase should have a clear input type and output type
Error propagation	Fail fast -- don't continue past a failed phase
State passing	Use structured output (JSON) between phases
Resumability	Track phase status for long pipelines (see section 4)

Pattern C: QC Gate

AI processing followed by quality verification before output reaches the user.

Phase 1: Mechanical prep (haiku)
Phase 2: AI work (sonnet)
Phase 3: QC verification (sonnet/opus)
  --> pass: proceed to output
  --> warn: output with warnings
  --> fail: stop, report issues
Phase 4: Output

Use when: AI output needs verification before the user sees it.

Threshold design:

Verdict	Condition	Action
PASS	All checks green	Deliver output directly
WARN	Minor issues (< 3 low-severity)	Deliver output with warnings section
FAIL	Any critical issue OR > 5 total issues	Stop, report what failed, suggest re-run

Real examples:

• reading-assistant: QC agents verify summaries for accuracy, completeness, fidelity
• codex-toolkit audit-fix: audit -> fix -> verify loop

Pattern D: Retry Loop

On failure, re-dispatch with error context. The agent gets a second chance with specific feedback about what went wrong.

agent produces output
  --> QC checks output
    --> pass: done
    --> fail: re-dispatch agent with error context
      --> QC re-checks
        --> pass: done
        --> fail (attempt 2): re-dispatch again
          --> max retries reached: fail with report

Use when: quality failures are recoverable by re-trying with more context.

Implementation:

## Retry Protocol
- Max retries: 3
- On retry, include in the agent prompt:
  - Previous output (or summary if too long)
  - Specific failures from QC
  - Instruction: "Fix ONLY the listed failures. Do not change passing sections."
- If max retries exhausted: output best attempt with failure annotations

Key decisions:

Decision	Recommendation
Max retries	3 (rarely succeeds after 3 if it failed 3 times)
Error context	Include specific failures, not "try again"
Scope of retry	Fix only failures, preserve passing output
Cost cap	Each retry costs full agent invocation -- budget accordingly

2. Shared Partials for DRY

Extract common logic into commands/shared/*.md with user-invocable: false in frontmatter.

When to Extract

Situation	Extract?
Same logic in 3+ commands	Yes -- always extract
Same logic in 2 commands, complex (> 20 lines)	Yes -- extract
Same logic in 2 commands, simple (< 10 lines)	No -- duplication is fine
Logic used by 1 command but might be reused	No -- wait until it's actually reused

Good Candidates for Extraction

Partial	What it contains	Who includes it
shared/load-config.md	Read and validate plugin config file	All commands that need config
shared/discover-files.md	Find target files by pattern/extension	Commands that scan the repo
shared/validate-prereqs.md	Check tool availability, environment	Commands with external dependencies
shared/format-report.md	Common report header, footer, severity colors	Commands that output reports

Partial File Structure

---
user-invocable: false
description: "Shared config loading logic — reads and validates the plugin config file"
---

## Config Loading

1. Look for `.config.md` in the project root
2. If not found, look for `.config.yaml`
3. If neither found, output error: "Run `/plugin:init` first to create a config file"
4. Parse the config file
5. Validate required fields: [list fields]
6. Return parsed config

3. Cost Gates

For expensive AI pipelines, add a cost estimation step between mechanical prep and AI processing.

Implementation

Phase 1: Parse and discover (haiku -- cheap)
  --> Count items to process
  --> Estimate cost: items x model cost per item
  --> Display estimate to user

User confirms or adjusts scope

Phase 2: AI processing (sonnet/opus -- expensive)
  --> Process confirmed scope

Cost Estimation Table

Model	Approx cost per item	10 items	100 items	1000 items
haiku	$0.001	$0.01	$0.10	$1.00
sonnet	$0.01	$0.10	$1.00	$10.00
opus	$0.03	$0.30	$3.00	$30.00

"Item" = one agent invocation processing one unit of work (one file, one chunk, one component).

User Confirmation Pattern

## Cost Gate
After Phase 1, display:
- Items to process: {N}
- Estimated model: {model}
- Estimated cost: ~${amount}
- Estimated time: ~{minutes} minutes

Ask: "Proceed with {N} items? (You can reduce scope with --filter)"

4. Pipeline State

For resumable pipelines (long-running, expensive, or failure-prone), track state in a JSON file.

State File Schema

{
  "pipeline": "my-pipeline",
  "startedAt": "2024-01-15T10:00:00Z",
  "configFingerprint": "sha256:abc123",
  "phases": {
    "parse": {
      "status": "completed",
      "startedAt": "2024-01-15T10:00:00Z",
      "completedAt": "2024-01-15T10:00:05Z",
      "itemsProcessed": 42,
      "output": "parse-output.json"
    },
    "analyze": {
      "status": "running",
      "startedAt": "2024-01-15T10:00:06Z",
      "itemsProcessed": 15,
      "itemsTotal": 42
    },
    "qc": {
      "status": "pending"
    }
  },
  "lock": {
    "pid": 12345,
    "acquiredAt": "2024-01-15T10:00:00Z"
  }
}

State Transitions

pending --> running --> completed
                   --> failed
                   --> skipped (if previous phase failed)

Resumability Rules

1. On start: check for existing state file
2. If state exists and configFingerprint matches: resume from last incomplete phase
3. If state exists and configFingerprint differs: warn user, offer fresh start or resume
4. If lock exists: check if PID is alive. If dead, clear stale lock. If alive, abort.

5. Model Tier Allocation

Assign models by cognitive load, not by importance.

Mechanical / IO:     haiku    (parser, scanner, formatter, counter)
Reasoning / AI:      sonnet   (summarizer, extractor, reviewer, linter)
Judgment / QC:       opus     (coordinator, architect, final reviewer)

Pipeline Model Assignment Example

Phase 1: Discover files          → haiku  (just glob + read)
Phase 2: Parse and chunk         → haiku  (mechanical splitting)
Phase 3: Analyze each chunk      → sonnet (requires judgment)
Phase 4: QC all analyses         → sonnet (verify, not create)
Phase 5: Synthesize final report → opus   (cross-reference, prioritize)

Cost Optimization

Optimization	How	Savings
Batch mechanical work	One haiku call processes all files, not one per file	5-10x
Pre-filter before AI	Use grep/glob to skip irrelevant files before sonnet	2-5x
Cache phase outputs	Don't re-run completed phases on retry	1-3x
Scope reduction	Let user filter to subset before expensive phases	Variable

6. Error Propagation

Rules

1. Phase fails -> STOP. Set status "failed" + error message in state. Do not continue to next phase.
2. Agent fails -> report and continue (in parallel dispatch). One agent's failure shouldn't block others.
3. Retry fails -> escalate. After max retries, surface the failure to the user with full context.
4. Never swallow errors silently. Every failure must be visible in the final output.

Error Report Format

## Pipeline Error

**Phase**: {phase_name}
**Status**: FAILED
**Error**: {error_message}

### Context
- Items processed before failure: {N} of {M}
- Last successful item: {item_id}
- Time elapsed: {duration}

### Recovery Options
1. Fix the issue and run `/command --resume` to continue from this phase
2. Run `/command --restart` to start fresh
3. Run `/command --skip-phase {phase_name}` to skip this phase (not recommended)

Fallback Paths

Always offer a manual fallback when automation fails:

## Fallback
If the pipeline fails after 3 retries:
1. Output all successfully processed items
2. List failed items with error context
3. Suggest manual analysis for failed items

7. Pattern Selection Guide

Your situation	Pattern	Why
Multiple independent analyses of same input	A: Parallel	No dependencies, maximize throughput
Each step needs previous step's output	B: Sequential	Data flows in one direction
AI output must be verified before delivery	C: QC Gate	Catch errors before user sees them
Quality failures are recoverable with feedback	D: Retry	Cheaper than manual re-run
Complex multi-stage with verification	B + C	Pipeline with QC gates between expensive phases
Multiple analyses with quality bar	A + C	Parallel dispatch, then QC all results