omp-task-group

Atomic multi-agent coordination for Oh My Pi (OMP) — fan out N independent subagents, join, and return exactly one logical result to the parent. Not a workflow engine: no DAG, no depends_on, no pipeline, no loop, no resume.

Works with the installed omp (v18.x). Zero runtime dependencies; public API only.

What it does

When you delegate 2+ independent jobs whose combined results drive your next decision, the naive task-per-job pattern amplifies parent wakes: every child completion is a separate async delivery that interrupts you. omp-task-group fixes that:

Property	Without (N × task)	With Task Group
Logical parent deliveries	N	1
Wake amplification	N	1/N
Parent context cost	N raw child outputs	one bounded digest
Failure handling	ad hoc	all / any / quorum × collect / fail_fast

Main: 1 call → [child1 child2 … childN] (parallel) → 1 joined result back

Install

# clone somewhere stable
cd ~/src && git clone <this-repo> omp-task-group && cd omp-task-group
bun install && bun run build
omp plugin link "$(pwd)"

The plugin does not shadow or re-register the built-in eval tool. A Task Group runs as an ordinary native eval cell whose code is exactly one ompTaskGroup(<strict JSON>) envelope; the plugin recognizes the envelope through tool hooks, runs the group inside that single cell, and returns one joined result. Ordinary eval is never claimed as plugin-owned — non-envelope cells run exactly as native eval would.

Usage

Single delegated job → keep using the native async task tool. Dependent stages, pipelines, loops, resume → use OMP swarm. Task Group is for one atomic batch:

ompTaskGroup({
  "context": "Audit plan: independent workstreams, results are combined.",
  "label": "audit",
  "tasks": [
    { "name": "deps",  "agent": "scout",  "task": "Enumerate vulnerable dependencies." },
    { "name": "auth",  "agent": "security-reviewer", "task": "Review auth flows." },
    { "name": "tests", "agent": "scout",  "task": "Report test coverage gaps." }
  ],
  "join":     { "mode": "all" },
  "failure":  { "mode": "collect" },
  "execution": { "strategy": "auto", "concurrency": "auto" },
  "output":   { "mode": "compact", "perTaskChars": 1200, "maxTotalChars": 8000 }
});

That block is the entire cell: a standard eval call with language: "js", timeout: 0, and code containing exactly the ompTaskGroup(...) envelope — outer whitespace and one optional terminal semicolon are allowed, nothing else is. The argument is strict JSON (double-quoted keys, no comments, no trailing commas), so the envelope is recognized without executing arbitrary JavaScript. A recognized-but-malformed envelope is blocked with a precise reason; anything that is not the envelope is an ordinary eval cell and runs exactly as native eval would.

Per task: schema (+ schemaMode) for structured output, isolated for worktree isolation, tools for kernel-tool exposure, effort (forward-compatible).

Join and failure

• join.mode: all (default) · any (first success settles) · quorum: N
• failure.mode: collect (default — report everything, group completes with partial successes) · fail_fast (first failure cancels the rest)
• Losers of any/quorum/fail_fast are cancelled and reaped — their deliveries are consumed, nothing leaks to the parent.

Output modes (Result Gate)

• compact — per-task glyph/status, clipped preview, duration + model, agent:// handle for the full transcript (handles preserved so nothing is lost).
• structured — one JSON aggregate of per-task structured outputs.
• summarize — stateless completion() digest (opt-in via config), falls back to compact on failure.
• Hard caps: perTaskChars per task, maxTotalChars total. Raw child output is never concatenated wholesale.

Strategies

• fanout — per-child agents with per-handle waits, all inside the single eval cell; child deliveries are consumed exactly once there, so the parent sees only the one native eval result (no re-delivery wakes).
• pool — one workpool for large homogeneous batches (join=all + collect, all tasks same agent/isolation/tools/schema, count ≥ threshold). Coarse progress; per-item results recovered from the aggregate; automatic fallback to fanout on any mismatch.
• auto (default) picks between them; /task-group explain shows the decision trace.

Commands

• /task-group — overview + capability probe
• /task-group stats — cumulative telemetry (wake amplification, output reduction, strategy mix)
• /task-group explain — why the last group chose its strategy
• /task-group config — effective configuration

Smart Dispatcher (default: suggest)

A short routing policy is appended to the system prompt (zero extra inference) via before_agent_start. enforce mode additionally blocks obviously-batched native task calls. off disables both. The post-hoc Missed Group Detector records missed_group_candidates telemetry when ≥2 independent task calls happen in one turn.

Configuration

~/.omp/agent/task-group.json and/or <cwd>/.omp/task-group.json (project wins). Unknown keys ignored; invalid values error with a precise path.

{
  "enabled": true,
  "dispatcher": { "mode": "suggest", "detectMissedGroups": true },
  "execution": { "strategy": "auto", "concurrency": "auto", "pool": { "enabled": "auto", "threshold": 6 } },
  "join": { "default": "all" },
  "failure": { "default": "collect" },
  "output": { "mode": "compact", "perTaskChars": 1200, "maxTotalChars": 8000, "preserveHandles": true },
  "summarize": { "enabled": false, "model": "smol" },
  "telemetry": { "enabled": true, "detectMissedGroups": true }
}

Foreground barrier (fail-closed)

Task Group requires a foreground native eval cell — the group runs and finalizes inside that one call. eval.autoBackground.enabled=true would hand long cells to the background job runner and return early, so a configured auto-background is a hard block: the plugin detects the documented config key and refuses to run envelope groups, telling you exactly how to fix it. A steering-triggered auto-background (a mid-cell steer forcing native auto-background) cannot be pre-blocked; if it happens anyway, the native result carries details.async and the group is decoded as a barrier violation — detected and fail-closed, never silently treated as a clean result. The plugin never mutates user settings, and there is no degraded opt-in.

RPC / headless

A group is one native eval tool result — there is no live per-task update stream and no custom widget/RPC snapshot channel.

• Content: the bounded text digest — per-task status, clipped preview, duration + model, agent:// handle for the full transcript.
• Details: the stable snapshot shape { protocol: "omp-task-group/v1", snapshot, gate, ... } on the final result (decoded from the eval wire payload — never raw jsonOutputs).
• Plain/headless and TUI/RPC modes receive identical final content/details.

Architecture

See docs/ARCHITECTURE.md. Highlights:

• Standard eval envelope: usage is eval code containing exactly ompTaskGroup(<strict JSON>). The plugin never shadows eval; a tool_call hook recognizes the envelope (rewriting the cell to run the compiled group program) and a tool_result hook finalizes the result.
• Compiled program uses only the public eval prelude (agent / wait / workpool / completion / display / print) and calls display() exactly once with the wire protocol omp-task-group/eval-result-v1; the finalizer decodes it from native details.jsonOutputs back into the stable snapshot details.
• One state reducer → one snapshot protocol (omp-task-group/v1); every text and detail consumer reads only that final snapshot.
• Private-API import guard: CI fails if any source file imports OMP internals (scripts/check-private-imports.ts, mirrored as a test).

Development

bun install
bun run typecheck        # tsc --noEmit (strict)
bun test                 # unit tests incl. mocked-kernel program execution
TEST_INTEGRATION=1 bun test tests/integration   # real omp run (10 sonic children)
bun run lint:private-api
bun run build

Known limits (v0.1)

• Per-child token counts are not exposed by OMP's public surface in 18.1.x; snapshots carry null tokens and budget-delta estimates in telemetry.
• No live per-task stream: the parent sees one final tool result. Output lines the native eval cell may show while a group runs are ordinary cell output, not Task Group transport — never rely on them as a per-task update channel.
• The group cell renders through native eval's public tool UI (code + output); the plugin cannot swap in a custom live renderer, so the joined digest is the delivered content/details.
• effort is accepted but inert until OMP exposes effort on eval agent().
• Pool strategy reports coarse (aggregate) progress while running.