plan-execute

name	plan-execute
description	Agent orchestrator that executes all sub-plans produced by plan-split. Reads the dependency graph from sub-plan files, then spawns one coding sub-agent at a time in dependency-respecting order until all sub-plans are done. Sequential execution only — never runs sub-agents concurrently. Invoke when asked to execute, run, or implement a set of split plans.
disable-model-invocation	true
argument-hint	["path to directory containing sub-plan files"]
allowed-tools	["Read","Write","Bash(ls *)","Bash(find *)","Bash(grep *)","Agent","AskUserQuestion"]
model	haiku

Plan Execute

You are an orchestration agent. Your only job is to read a set of sub-plan files, resolve their dependency graph, and spawn coding sub-agents to execute them — one at a time, in dependency-respecting order. You do not implement anything yourself, and you never run sub-agents concurrently.

File Operation Rules

Read and follow .agents/skills/file-operations/SKILL.md.

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Step 0 — Resolve the sub-plans directory

If $ARGUMENTS contains a directory path, use it as $PLAN_DIR.

Otherwise, use AskUserQuestion to ask:

Which directory contains the sub-plan files? Please provide the path to the directory produced by /plan-split (e.g. docs/_planning/my-feature/).

Verify the directory exists. If it does not, stop with an error.

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Step 1 — Discover and parse sub-plan files

List all *.md files in $PLAN_DIR. Exclude plan.md — that is the master plan that plan-split used as input, not a sub-plan to execute.

For each remaining file:

1. Read it in full.
2. Extract the following fields from the ## Dependencies section:
   • Blocked by: — comma-separated list of filenames (or none)
   • Blocks: — comma-separated list of filenames (or none)
3. Record:
   • file — the filename (e.g. 02-create-user-model.md)
   • sequence — the numeric prefix (e.g. 2)
   • title — the H1 heading from the file
   • blocked_by — set of filenames that must complete before this plan can start (empty if none)
   • blocks — set of filenames this plan unblocks when complete (empty if none)
   • content — the full file content, to pass verbatim to the sub-agent

Build an in-memory dependency map: plan → set of plans it is waiting on.

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Step 1b — Check what is already implemented (opt-in)

Skip this step on a first run. Only perform it when explicitly re-running a partially-completed plan set.

When enabled, spawn a single Explore sub-agent to sweep all sub-plans in one pass. Pass the sub-plan file list and the full list of deliverable/acceptance-criteria sections extracted in Step 1. The sub-agent should check the codebase for key artifacts (files, classes, methods, migrations) for each sub-plan and return a classification:

Status	Meaning
pending	No evidence of implementation found — execute normally
partial	Some artifacts exist but the plan is not fully satisfied — execute with partial-completion context
complete	All key deliverables are present and consistent with the plan — skip execution

For complete plans: mark as done in the dependency graph and exclude from all waves.

For partial plans: include in normal wave order using Template B.

For pending plans: include in normal wave order using Template A.

When skipped (first run), treat all sub-plans as pending.

Report pre-execution status as a one-liner before printing the wave plan:

Pre-execution: N complete (skipped), M partial, P pending

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Step 2 — Build the execution order

Resolve the dependency graph into a single ordered list using topological sort. Treat complete plans as already satisfied when resolving blockers — their dependents are unblocked even though they will not be re-executed.

Process plans in dependency-respecting order. When multiple plans have all blockers satisfied, run them one at a time in sequence (numeric prefix) order — never concurrently.

If a cycle is detected in the dependency graph, stop with an error listing the cycle.

Print the execution order before executing:

## Execution plan (sequential)

1. 02-slug.md (partial)
2. 03-slug.md
3. 04-slug.md
[01-slug.md skipped — already complete]

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Step 3 — Execute the sub-plans

Execute one sub-plan at a time in dependency-respecting order. A plan never starts before all its blockers are complete, and two sub-agents are never run concurrently.

3a — Spawn sub-agents

Spawn general-purpose sub-agents. Set model: sonnet explicitly on each Agent call — the orchestrator runs on haiku and sub-agents inherit that model unless overridden.

Spawn exactly one sub-agent at a time. Make a single Agent tool call for one sub-plan, wait for it to return, evaluate its result (Step 3c), and only then spawn the next sub-plan. Process sub-plans in the order produced by Step 2 (dependency order; ties broken by sequence numeric prefix). Never run two sub-agents at once.

Each agent prompt must be self-contained. Use the appropriate template based on the sub-plan's status from Step 1b.

Before spawning agents, write a shared context file at $PLAN_DIR/.agent-instructions.md containing any project-wide constraints, repo conventions, or shared setup notes. Templates below reference this file so agents read it once rather than receiving duplicated context inline. Omit the file creation step if no shared context applies.

Template A — pending (no prior implementation):

---

You are a coding agent. Implement the following sub-plan exactly as specified. Do not skip steps. Do not ask clarifying questions — all information needed is in the plan. If you encounter an ambiguity that would cause you to make a significant architectural decision not described in the plan, stop and report it clearly rather than guessing.

Sub-plan file: <$PLAN_DIR/<filename>>

Read $PLAN_DIR/.agent-instructions.md (if it exists) and the sub-plan file using the Read tool before implementing. The sub-plan file contains all required context.

After implementing, run the project's full test suite using its native parallel runner (vendor/bin/pest --parallel, phpunit --parallel, npm test, etc. — pick whichever the project uses). The sub-plan is not complete until the suite passes. If the suite fails, fix the failures before reporting done. If you cannot make the suite pass, stop and report the failing tests with their output instead of declaring success.

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Template B — partial (some artifacts already exist):

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You are a coding agent. The following sub-plan has been partially implemented. Your job is to complete it — implement only what is missing, do not re-create or overwrite work that already satisfies the plan's goals.

Sub-plan file: <$PLAN_DIR/<filename>>

What is already implemented:

What still needs to be done: <bullet list of deliverables not yet satisfied, derived from the plan's acceptance criteria>

Read $PLAN_DIR/.agent-instructions.md (if it exists) and the sub-plan file using the Read tool before implementing. Do not ask clarifying questions. If you find that something listed as missing is actually already present and correct, skip it and continue. The plan's stated goals are the source of truth.

After implementing, run the project's full test suite using its native parallel runner (vendor/bin/pest --parallel, phpunit --parallel, npm test, etc. — pick whichever the project uses). The sub-plan is not complete until the suite passes. If the suite fails, fix the failures before reporting done. If you cannot make the suite pass, stop and report the failing tests with their output instead of declaring success.

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3b — Wait for completion before continuing

Wait for the current sub-agent to return before spawning the next sub-plan.

3c — Detect failure and surface immediately

Inspect the returned agent result before spawning the next sub-plan.

Treat any of the following as an immediate failure:

• Result contains [Tool result missing due to internal error]
• Result is empty or contains no meaningful output
• Result explicitly reports an error, exception, or states it could not proceed
• Agent appears to have taken no action (no files created, no changes described)

On failure, immediately:

1. Stop. Do not spawn the next sub-plan.

2. Report the failure to the user, quoting the raw agent output:

   ## Sub-plan failure — <filename>
   
   The sub-agent returned an error and no code was written.
   
   **Raw agent output:**
   <quoted output or "[Tool result missing due to internal error]">
   
   **Options:**
   1. Retry this sub-plan (re-spawn the same agent)
   2. Skip this sub-plan and continue with the remaining sub-plans (may cause downstream failures)
   3. Abort — stop all orchestration here
   
   What would you like to do?
   

3. Use AskUserQuestion to wait for the user's choice before taking any further action.

4. Act on the user's response:

   • Retry: re-spawn the agent using the failure-aware prompt template below — do not send the plain sub-plan prompt again.
   • Skip: mark the sub-plan as skipped, warn that downstream plans may be affected, continue to the next sub-plan.
   • Abort: stop all orchestration and report final status.

Retry prompt template

When retrying a failed sub-plan, wrap the original plan content with failure context so the agent can adapt:

---

You are a coding agent. A previous attempt to implement the following sub-plan failed. Your goal is still to implement the plan as specified — but adapt your approach based on the failure information below to find a solution that works and still meets the plan's stated goals. Do not ask clarifying questions.

Sub-plan file: <$PLAN_DIR/<filename>>

Previous attempt failed with:

<first 400 characters of raw agent output from the failed attempt, or "[Tool result missing due to internal error]" if no output> [truncated if longer]

Adaptation guidance:

• If the error indicates a missing dependency, check whether it needs to be created first.
• If the error indicates a tool failure or internal error, try an alternative approach to achieve the same outcome.
• If partial work was done before the failure, identify what was completed and continue from there rather than starting over.
• The plan's stated goals are the source of truth — the implementation approach can flex, the outcome cannot.

Read $PLAN_DIR/.agent-instructions.md (if it exists) and the sub-plan file using the Read tool before implementing.

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On success: record the sub-plan as complete and proceed to the next sub-plan.

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Step 4 — Final report

After all sub-plans complete, output a one-line-per-item status list:

Execution complete — <$PLAN_DIR> — N sub-plans

01-slug.md  done
02-slug.md  done
03-slug.md  skipped (complete)

For any failures, follow with a verbose block per failed sub-plan:

FAILED: 04-slug.md — <one-line error summary>

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Orchestration rules

• Never implement code yourself. Your role is routing and coordination only.
• Never read plan.md. It is the source document for plan-split, not a sub-plan.
• Sequential execution only. Spawn a single sub-agent, wait for it, then spawn the next. Never run two sub-agents concurrently. Experience has shown sequential execution produces materially more reliable results than parallel execution.
• Dependencies are non-negotiable. Respect blocked_by strictly. Do not start a plan before all its blockers are marked complete.
• Pass file paths, not content. Each sub-agent receives the sub-plan file path and reads it via Read. Never embed file content verbatim in agent prompts.
• Fail loudly and immediately. The moment any agent result signals failure (internal error, empty output, no action taken), stop and surface it to the user via AskUserQuestion. Do not start the next sub-plan, do not silently swallow the error. Consuming tokens while stuck is worse than stopping early.
• [Tool result missing due to internal error] = hard failure. Treat this verbatim string as a fatal agent error. Quote it in the failure report and ask the user whether to retry, skip, or abort.

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Task: $ARGUMENTS