Staged Implementation

Staged Implementation is a Codex plugin that bundles four skills for chunked implementation work:

planner plans scoped chunks, writes implementer prompts, reviews diffs, and clarifies frozen contracts.
implementer executes one scoped implementation prompt without widening the task.
validator verifies implemented behavior against the plan, prompt, checklist, review findings, or frozen contracts.
orchestrator coordinates the planner, implementer, and validator loop across multiple chunks.

Use this plugin when a feature or fix is too large or contract-heavy to handle as one open-ended coding pass.

Plugin Structure

staged-implementation/
  .codex-plugin/
    plugin.json
  skills/
    planner/
      SKILL.md
    orchestrator/
      SKILL.md
    implementer/
      SKILL.md
    validator/
      SKILL.md

Recommended Marketplace Layout

Codex installs plugins from a marketplace catalog. To publish this from Git, put the plugin inside a marketplace repository:

arcana-codex-plugins/
  .agents/
    plugins/
      marketplace.json
  plugins/
    staged-implementation/
      .codex-plugin/
        plugin.json
      skills/
        planner/
        orchestrator/
        implementer/
        validator/

Example .agents/plugins/marketplace.json:

{
  "name": "arcana-codex-plugins",
  "interface": {
    "displayName": "Arcana Codex Plugins"
  },
  "plugins": [
    {
      "name": "staged-implementation",
      "source": {
        "source": "local",
        "path": "./plugins/staged-implementation"
      },
      "policy": {
        "installation": "AVAILABLE",
        "authentication": "ON_INSTALL"
      },
      "category": "Productivity"
    }
  ]
}

Install From Git

Add the marketplace repository:

codex plugin marketplace add dayowe/arcana-codex-plugins --ref master

Install the plugin:

codex plugin add staged-implementation@arcana-codex-plugins

Start a new Codex session after installation so the bundled skills are available.

Usage

Invoke a specific skill when you know the role you want:

Use $planner to write the next implementer prompt for this feature.
Use $implementer with docs/prompts/chunk-03.md.
Use $validator to verify this chunk against the frozen API contract.
Use $orchestrator to run the staged implementation loop for this checklist.

The usual flow is:

Use planner to freeze scope, contracts, validation, and the next chunk.
Use implementer to execute only that chunk.
Use validator when runtime, UI, API, integration, or regression evidence is needed.
Use orchestrator when you want Codex to coordinate the loop across chunks.

Lifecycle and Context Efficiency

The workflow keeps implementation and validation rigor while avoiding avoidable context churn:

Each worker carries stable chunk/assignment IDs, with a recorded mapping to a supported unique task label when available. Same-worker corrections retain the ID; replacement workers increment the attempt.
An implementer may remain available for same-chunk repairs but cannot write during validation. Replacements acquire write ownership only after prior writes stop and the candidate, findings and resources are verified and transferred.
Accepted/permanently blocked assignments retire after handoff: stop work and dispatch, close when supported, otherwise establish inactivity. Retained exceptions need a purpose/release condition; safe independent chunks may overlap with explicit ownership and isolation. Idle availability alone does not demonstrate token expense.
Workers return one compact packet and stop until a concrete follow-up. Avoid acknowledgement chatter; retain justified liveness checks, intervention and blocker reporting.
The existing durable handoff stays compact while preserving pending gates, dependencies, recovery obligations and authority restrictions directly or through authoritative links.
Parent review starts from the actual diff, requirements and evidence, inspecting surrounding code, callers and shared behavior as needed without waiting for a discovered defect.
Read the resource reference for initial persistence verification before edits and before substantial allocations (including large builds in the main checkout), worktree/resource management or cleanup. Reuse applicable instructions and verified setup rather than reloading them for routine steps.

These are efficiency rules, not acceptance shortcuts. Required independent validation, fresh gates, contract checks and evidence remain mandatory where the task requires them.

Notes

The skills are intentionally separate. Keeping the roles separate makes the boundaries clearer and reduces accidental scope widening.
validator reports evidence and risk. planner or orchestrator decides whether a chunk is accepted.
orchestrator may commit accepted chunks only when the user explicitly authorizes commits.
Unfinished source, backing Git metadata and required evidence live on persistent storage from creation. Prefer the project's established worktree location; ask once if isolation needs a new location. /tmp is for reproducible scratch, never the only copy of unfinished work. Nested worktree paths must be ignored, untracked and protected from broad cleanup.
Authorizing orchestration includes routine cleanup of its tracked, disposable temporary resources after ownership, retention and consumer-release checks pass. The handoff states this default; explicit retention/no-deletion instructions override it. Shared caches, unrelated files and resources still needed remain protected.
If the same skill names also exist as standalone local skills, Codex may show duplicates. After the plugin is installed and verified, remove or disable the standalone copies if you want only the plugin version.

Development

Validate the plugin manifest:

python3 /path/to/plugin-creator/scripts/validate_plugin.py /path/to/staged-implementation

Validate an individual skill:

python3 /path/to/skill-creator/scripts/quick_validate.py /path/to/staged-implementation/skills/planner

After pushing marketplace changes, run codex plugin marketplace upgrade arcana-codex-plugins.

If this plugin changed, reinstall it with codex plugin add staged-implementation@arcana-codex-plugins, then start a new Codex session so updated skills are loaded.

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