plan-execute-strategy

name	plan-execute-strategy
description	Use when deciding HOW to split work between a strong planner and cheaper executors — subagent models, writing delegation prompts, running the plan-big/execute-small workflow, or choosing delegation vs the advisor tool.
license	MIT
metadata	{"author":"Mark Beacom","version":"0.1.0"}
allowed-tools	Read Bash

Plan / Execute Strategy

Two inversions of the same idea — spend strong-model tokens on judgment, cheap tokens on volume. Pick by which model you want in the driver's seat.

Strategy	Who plans	Who executes	Set up with
Delegation	strong main model	cheap subagents	CLAUDE_CODE_SUBAGENT_MODEL + a delegation prompt (this skill)
Advisor	strong advisor, consulted mid-turn	cheap main model	/advisor (the server-side advisor tool)

They are orthogonal — you can run both at once (cheap main + strong advisor + cheaper subagents). This skill is about delegation; the advisor tool is covered at the end so you pick the right one.

When to use delegation

• The task splits into independent, token-heavy sub-tasks (multi-file audits, broad research sweeps, large log/document review).
• You want a strong model (Opus 5, Fable 5) to plan and synthesize, but the reading and mechanical edits don't need that tier.
• The advisor can't help here — a Fable 5 main runs without any advisor today (see below), you're off the Anthropic API (Bedrock, Google Cloud, Foundry), or your main model doesn't support it — or you specifically want the strong model leading rather than merely advising.

Delegation, interactive

Run the session with a strong main model and pin subagents to a cheaper one, then tell the main model to delegate:

CLAUDE_CODE_SUBAGENT_MODEL=sonnet claude \
  --append-system-prompt "For task execution, delegate to subagents with clear, \
appropriately-scoped instructions. You own planning and oversight of overall \
progress; self-judged exceptions are allowed."

Set the main model separately with /model (in-session) or --model (e.g. --model claude-opus-5 or --model claude-fable-5). The two knobs are independent: --model / /model picks the driver, CLAUDE_CODE_SUBAGENT_MODEL picks the workers.

How the subagent model resolves (first match wins):

1. CLAUDE_CODE_SUBAGENT_MODEL env var (alias — sonnet / opus / haiku / fable — or a full model ID). Aliases track your provider's recommended version, not necessarily the newest one — see the alias caveat below.
2. The per-invocation model passed when the subagent is spawned.
3. The subagent definition's model: frontmatter.
4. Otherwise inherit (same model as the main conversation). As of v2.1.196, setting the env var to inherit is the same as leaving it unset.

Subagents also inherit the main conversation's extended-thinking setting (v2.1.198+).

Alias caveat — sonnet / opus are provider-scoped. They resolve to the recommended version for your provider, which is not always the newest one:

Provider	opus	sonnet
Anthropic API	Opus 5	Sonnet 5
Claude Platform on AWS	Opus 5	Sonnet 4.6
Amazon Bedrock, Google Cloud's Agent Platform	Opus 5	Sonnet 4.5
Microsoft Foundry	Opus 4.6	Sonnet 4.5

So an alias is the right default on the Anthropic API, but off it — exactly the runtimes where delegation is your only option, since the advisor can't reach them — sonnet can silently mean Sonnet 4.5. To force the current generation anywhere, pin the full model name (claude-opus-5, claude-sonnet-5) or set ANTHROPIC_DEFAULT_OPUS_MODEL / ANTHROPIC_DEFAULT_SONNET_MODEL. Opus 5 needs Claude Code v2.1.219+; Sonnet 5 needs v2.1.197+.

Where to put the delegation instruction — pick one, don't stack them:

• --append-system-prompt "…" — session-scoped, nothing left behind. Cleanest for a one-off. (This is the recommended default.)
• A custom output style (/output-style) — persists the delegation posture across sessions without editing CLAUDE.md.
• CLAUDE.md — durable and repo-shared, but it only steers behavior; it can't set the subagent model (that's the env var / frontmatter above).

Delegation, scripted

When you want the split to be deterministic and repeatable rather than left to the model's judgment, run the bundled workflow:

/plan-big-execute-small <task>

It runs a strong planner (decompose into independent sub-tasks) → cheap workers in parallel (default haiku, isolated contexts, distilled findings) → a cheap verifier (re-checks the workers' claims, read-only) → a strong synthesizer (merge). The command invokes the plugin's workflows/plan-big-execute-small.workflow.js via the Workflow tool. Prefer this over the interactive setup when you need coverage guarantees, a fixed number of workers, or a barrier before synthesis; prefer interactive when the shape of the work is still unfolding.

For interactive delegation of a single scoped unit, hand it to the execution-worker subagent this plugin ships — a Sonnet-by-default worker (its model: sonnet frontmatter is cheaper than an Opus 5 / Fable 5 planner, capable enough to edit) that does one task and reports back. Override its model with CLAUDE_CODE_SUBAGENT_MODEL — haiku for read-only investigation, or claude-sonnet-5 to guarantee Sonnet 5 on a provider whose sonnet alias still points at 4.x.

Deferred by design: if a workload ever needs a guaranteed read-only lane — e.g. many workers on a shared tree — a dedicated investigation-worker (tools: Read/Grep/Glob only, no Bash/Edit/Write) is the sanctioned next agent to add. It isn't shipped yet: one broadly-scoped worker plus these instructions covers the current need, and a fleet of specialized agents would fight the "few agents" convention while the CLAUDE_CODE_SUBAGENT_MODEL override flattens per-agent model pins on the scripted path anyway.

The advisor tool (/advisor) — how it differs

/advisor (the advisorModel setting) is the server-side advisor tool: a cheaper main model consults a stronger advisor mid-turn for a plan or course correction, then keeps executing. It is the inverse of delegation — the strong model advises rather than leads. What to know before picking it:

• Capability pairing. The advisor must be at least as capable as the main (executor) model — a weak main + strong advisor is the point. An Opus 5 main accepts Fable or any Opus 4.7-or-later advisor (Opus 5 included); a Sonnet 5 or Opus 4.6 advisor is rejected. A Sonnet 5 main accepts Fable, Opus, or Sonnet 5 — a Sonnet 4.6 advisor is rejected. The advisor is Anthropic-API-only, so there the opus / sonnet aliases do resolve to Opus 5 / Sonnet 5 (unlike the provider-scoped delegation case above); pass a full ID like claude-opus-5 only when you need to pin a version. An equal-tier advisor (e.g. Opus 5 main + Opus 5 advisor) is not a no-op — it's a legitimate independent second read, just not a stronger opinion.
• Fable 5 as the advisor is turned off right now — a deliberate, remotely-controlled rollout, not a billing gate. As of Claude Code v2.1.210+ the advisor doc says so: the /advisor picker shows a dimmed Fable 5 (temporarily unavailable) row, and Claude Code rejects /advisor fable and --advisor fable. The underlying defect is #76199 — advisorModel: fable plus any prior tool_use in the transcript deterministically returns unavailable (the executor model is irrelevant, an Opus advisor is immune, and it is not a context-size issue). Use /advisor opus instead — the alias resolves to Opus 5, which works as the advisor today.
• A Fable 5 main session has no advisor at all. A Fable main accepts only a Fable advisor, and Fable isn't offered, so a Fable 5 session runs advisor-less until the rollout returns it. That gap is exactly what delegation (this skill) fills: plan big with Fable 5, execute small with cheaper subagents.

Hardening notes (these bite CI and gateway users):

• Anthropic API only. The advisor is a server-executed tool — not available on Amazon Bedrock, Claude Platform on AWS, Google Cloud's Agent Platform, or Microsoft Foundry. Through an LLM gateway it works only if the request is forwarded intact. On those runtimes, delegation is the fallback.
• Deterministic off-switch. CLAUDE_CODE_DISABLE_ADVISOR_TOOL=1 disables the advisor entirely: /advisor becomes unavailable, any advisorModel is ignored, and --advisor is accepted but inert — existing scripts won't error. Clean when you want delegation to be the only orchestration in play.
• Subagents inherit the advisor and re-check the pairing against their own model, so a Sonnet 5 subagent under an Opus 5 main can still consult the advisor even where the parent pairing couldn't — useful when you combine delegation with an advisor.

Rule of thumb: cheap main that occasionally needs a smart second opinion → advisor. Strong main that should offload volume → delegation (this skill).

Portability (GitHub Copilot)

GitHub Copilot CLI supports this plugin format directly — no manual file copying. Register the marketplace and install the plugin:

copilot plugin marketplace add mbeacom/context-kit
copilot plugin install plan-execute@context-kit

The scripted Workflow and CLAUDE_CODE_SUBAGENT_MODEL are Claude Code features; the delegation posture (plan strong, execute cheap) applies wherever an agent can spawn workers.