pi-delegate

One Pi tool: delegate.

Give Pi a clean side thread. delegate starts a fresh child agent, gives it a task, then brings back only the useful result. No child transcript. No scratchpad spill. No context mud.

Small by design: no workflow engine, background job manager, dashboard, or artifact system. One tool. One job. Keep the main context clean.

Install

pi install npm:pi-delegate

What it adds

pi-delegate adds the delegate tool.

The tool runs a fresh in-memory child Pi agent in the current project, waits for the task to finish, and returns:

• the child’s concise final report
• model/effort metadata
• duration
• child tool/error counts
• child turn/token/cost usage when the provider reports usage
• output truncation metadata when the final report is large
• native tool errors with concise failure metadata when delegation fails

The main agent never sees the child’s intermediate exploration.

Tool API

delegate

Parameters:

• task: the task for the child agent
• effort: optional fast | balanced | smart — default balanced, but callers should choose explicitly

Effort maps to one model with different thinking levels:

effort	model	thinking
fast	openai-codex/gpt-5.5	minimal
balanced	openai-codex/gpt-5.5	medium
smart	openai-codex/gpt-5.5	high

Choose fast for scouting, repo mapping, docs/API lookup, and quick read-only recon. Choose smart for review, critique, debugging, ambiguous design, and high-risk reasoning. Use balanced for moderate investigation or exceptional, explicitly write-capable child implementation.

If openai-codex/gpt-5.5 is missing or unauthenticated, delegate falls back to the parent model and reports the fallback in metadata.

Behavior

• fresh in-memory child session
• parent cwd
• project context files loaded through Pi's normal resource discovery
• extensions and package resources discovered from the child session's cwd/agent directory are loaded; ad-hoc extension paths listed in PI_CHILD_EXTENSION_PATHS are also loaded in the child
• recursive delegation tools are disabled inside the child
• sequential execution to avoid concurrent delegated writes
• 15-minute internal timeout
• running calls render as neutral progress, not failure; the tool header stays compact, while the result area shows the assigned task in a boxed card
• collapsed task cards show the first four non-empty task lines with a hidden-line hint; expanded tool output shows the full assigned task
• completed calls include a bounded child-report preview when collapsed and the full child report when expanded
• parent-facing delegation policy is tool-owned through the active delegate tool description, snippet, guidelines, and parameter descriptions; the package does not append a separate parent system prompt
• child final reports are prompted as handoff-ready summaries with task, result, evidence, files, verification, and only-important handoff notes
• failures throw native Pi tool errors with a concise reason plus model/duration/tool-count metadata
• final child output is truncated at Pi's standard 2000-line/50KB tool-output limits, with the full report saved to a temp file when truncation occurs
• normal Pi tools are available to the child, including write-capable tools; parent agents should keep implementation/final validation in the parent by default and delegate write-capable child tasks only when explicit or exceptional

Package shape

The npm package is both a Pi package and a small TypeScript module. Pi loads ./extensions/delegate.ts from the package manifest, while ./index.ts re-exports the extension and helper types for tests or advanced consumers.

When to use it

Use delegate for work that benefits from isolation:

• scan a code area without filling the main context
• research a library/API and report the answer
• get an explicitly requested independent/fresh review
• investigate noisy failures and report evidence

Do not use it as a workflow engine or a default implementation worker. The parent agent owns implementation, final validation, and the final answer unless the user explicitly asks for child implementation or the task has a clear exceptional isolation benefit. Explicit independent/fresh review requests should use delegation because isolation is the product. If you need chains, background jobs, worktrees, or agent management, use a purpose-built workflow package.

Development

bun install
bun test
bun run typecheck
bun run check
bun pm pack --dry-run
PI_OFFLINE=1 bunx --bun pi --no-extensions -e . --list-models >/tmp/pi-delegate-pi-load.out

Live delegate evals

live-eval.test.ts runs Pi in JSON mode against disposable fixture repos and compares delegate-enabled runs with a delegate-disabled control. It is opt-in locally because it uses live model calls:

PI_DELEGATE_LIVE=1 \
PI_DELEGATE_EVAL_JUDGE_MODEL=openai/gpt-5.5:low \
PI_DELEGATE_EVAL_TIMEOUT_MS=1800000 \
PI_DELEGATE_EVAL_MAX_TOKENS=1500000 \
PI_DELEGATE_EVAL_MAX_COST_USD=30 \
PI_DELEGATE_EVAL_ARTIFACT_DIR=artifacts/live-eval \
bun run test:live

PI_DELEGATE_EVAL_MODEL and PI_DELEGATE_EVAL_JUDGE_MODEL default to openai/gpt-5.5:low. Use PI_DELEGATE_EVAL_TASKS=id1,id2 to run a subset while tuning the policy.

The suite records sanitized JSONL traces plus summary.json, including delegate decision and effort-selection KPIs. It hard-fails crashes, budget overruns, read-only writes, required/forbidden delegate decision misses, and effort mismatches when delegate is called with an expected effort; implementation fixtures are generally allowed-not-required delegation. Judge quality scores remain calibration data.