Iron Law

Verify task independence before parallel execution.

Red Flags

• "These tasks look independent enough" → STOP, because hidden output dependencies only surface after parallel dispatch wastes the full budget — verify independence rigorously before execution.
• "Part 2 builds on part 1's conclusion but we can still batch them" → STOP, because inherent sequencing means this is not a batch job — route to workflow instead.
• "Let's skip the approval step, the decomposition is obvious" → STOP, because the Approve gate is mandatory with no exceptions — decomposition errors are cheap to fix before execution and expensive after.
• "10 units is fine, we have the budget" → STOP, because cost scales linearly (10 units = 10x a single invocation) — always show estimated cost at the Approve gate and get explicit approval.
• "2 units failed but the other 8 are fine, just discard the failures" → STOP, because partial failure requires a clear failure report with error summaries and recommended actions — do not silently drop failed units.

Batch

Decompose large knowledge work tasks into independent parallel units, each executed in its own worktree. Inspired by Claude Code's /batch command — designed for high-volume, homogeneous content production.

When to Use

• User needs 5+ similar artifacts produced from distinct source material (e.g., 10 newsletter issues, 8 competitor analyses)
• The work has a clear unit of decomposition (by topic, by section, by competitor, by framework)
• Sequential execution would take too long and units do not depend on each other
• Output quality benefits from independent focus per unit rather than a shared context window

Workflow

1. Analyze

Dispatch an Explore agent to understand the full scope of the request:

• How many units does the task naturally decompose into?
• What is the unit type: topic, competitor, framework, section, time period, persona?
• What skill handles each unit (default: write)?
• What shared context applies to all units (format, voice, audience, constraints)?

2. Decompose

Break the task into 2–10 independent units. Each unit specification must include:

unit:
  id: <integer, 1-indexed>
  label: <short human-readable title>
  topic: <specific topic for this unit — no overlap with other units>
  skill: <write|research|analyze|review|refine>
  output: <file path: .captures/batch-{run_id}/{slug}.md>
  shared_context: <reference to shared context block>

Independence requirements (non-negotiable):

• Each unit produces a separate output file
• No unit uses another unit's output as input
• Units can complete in any order without inconsistency
• If a candidate unit depends on another unit's output → merge them into one unit or flag as sequential

Unit count limits:

• Minimum: 2 (batching 1 unit is a no-op)
• Default maximum: 10
• Override with --units N

3. Approve

Present the full decomposition plan to the user before any execution begins. This gate is mandatory — no exceptions.

Present as a table:

Show: total units, estimated cost (units × avg token cost), parallelism setting.

Wait for explicit approval. On rejection: re-decompose with user's feedback and re-present.

4. Execute

After approval, spawn one agent per unit. Each agent runs in an isolated worktree:

isolation: worktree
worktree_path: worktree-batch-{run_id}-unit-{id}

Concurrency is capped at --parallel (default: 3). Units beyond the cap queue and start as slots open.

Each unit agent receives:

• The unit specification (topic, skill, output path)
• The shared context block
• The selected skill's full instruction set

5. Monitor

Track status per unit: PENDING | RUNNING | DONE | FAILED.

Print a live status table as units complete. On unit failure:

• Log the failure with the unit's error
• Continue remaining units (do not abort the batch)
• Collect all failures for the synthesis report

6. Synthesize

After all units complete (or time out), produce a Batch Summary Report:

## Batch Summary — {topic} ({YYYY-MM-DD})

Units: {done}/{total} completed
Failed: {failed_ids} (if any)

### Output Files
| # | Label | Status | Path |
|---|-------|--------|------|
...

### Synthesis
{Optional: if --synthesize is set, produce a combined document merging all outputs}

### Failures
{For each failed unit: label, error summary, recommended action}

Save report to .captures/batch-{run_id}/00-summary.md.

Options

State

State persisted at .data/state/batch-{run_id}.json. Schema:

{
  "run_id": "batch-{timestamp}",
  "topic": "...",
  "status": "PENDING | RUNNING | DONE | FAILED",
  "units": [...],
  "parallel": 3,
  "created_at": "ISO-8601",
  "completed_at": "ISO-8601 | null"
}

Subagents

These are configurations for general-purpose subagents, not entries in agents/. There is no decomposer agent to dispatch by name — spawn a general-purpose subagent with the model, tools, and constraint below. (Contrast /scc:review, whose roles are real subagent_type values.)

explorer:   { model: haiku,  tools: [Read], constraint: "scope analysis only, no writing" }
decomposer: { model: sonnet, tools: [],     constraint: "produce unit specs, verify independence" }
unit_agent: { model: varies, isolation: worktree, constraint: "run assigned skill, write to assigned output path only" }
synthesizer: { model: opus,  tools: [Read, Write], constraint: "merge outputs faithfully, no hallucinated content" }

Gotchas

• Cost scales linearly: 10 units × write skill cost = 10× a single write invocation. Always show estimated cost at the Approve gate.
• Decomposition quality determines output quality: Vague unit topics produce vague output. If the topic cannot be made specific, ask the user before decomposing.
• Never skip the Approve gate: Decomposition errors are cheap to fix before execution and expensive after.
• Worktree cleanup: After synthesis, discard unit worktrees. Do not leave orphaned worktrees.
• No cross-unit dependencies: If the user's requested task has inherent sequencing (e.g., part 2 builds on part 1's conclusion), this is not a batch job — route to workflow instead.
• Partial failure is not total failure: If 2 of 10 units fail, deliver the 8 successes and report the 2 failures clearly. Do not withhold completed work.

See references/decomposition-guide.md for split strategies, anti-patterns, and merge strategies.