Rails Planning Phaser

Rails Planning Phaser

Take a single plan, grade it with rails-grade-cer, and — if it breaches threshold — fracture it into sequential phases small enough for a local model to execute end-to-end. Rewrite the original plan into a manifest that points at the phases and tracks their execution.

The point is a dark factory: keep real execution on the local rig by default, sizing each phase so the local model can actually do the work rather than deferring to a cloud model. Where phasing cannot get a phase small enough, this skill assigns it up the model tier rather than over-cutting.

Phasing is not triggered by failure. A plan scoring past threshold has not failed — it is just larger than one execution unit. That is ordinary software engineering. This skill's job is to size the work to the executor.

Core Principles

1. Phase to fit the executor. The threshold is the local model's competence boundary, not an abstract quality bar. A phase exists so a given model can finish it.
2. Local first, tier up only when forced. Always prefer the local model. Only move to a cloud tier when no legal phasing brings a phase under the local threshold.
3. Sequential, always. Phases run strictly in order. Never out of order — that defeats the purpose. Phase N may depend on phase N−1's output.
4. Every phase is a complete, testable unit. After any phase, the application compiles and runs. A phase that leaves the app broken or half-built is not a phase — it cannot be evaluated, so it cannot be trusted. This constraint outranks hitting the threshold.
5. Natural seams, not arithmetic. Cut at logical completion points, not by slicing effort into equal buckets. Because seams are respected, the sum of phase scores can exceed the original plan's scores. That is expected, not a defect.
6. Lean on model intelligence. The plan author (a high-reasoning model working to spec) already structures a good plan with testable increments. This skill reads that structure and groups it. Treat the grouping hints below as hints, not a rigid seam-finding algorithm.
7. Know when phasing cannot help. If the work is inherently too big (too many phases) or inherently too complex/risky to reduce, say so. Do not pretend phasing solved a problem it did not.

Relationship To rails-grade-cer

This skill holds no grading rubric of its own. Every score in this skill comes from following the rails-grade-cer skill against the whole document being scored (the original plan, or later, an individual phase). Grade all three axes at concise detail — this skill only needs the score table, not the paragraphs.

rails-grade-cer always writes a cer-score-card.md file beside whatever it grades. This skill embeds the resulting scores into the manifest and phase frontmatter instead of keeping grading artifacts around — after reading a score table, delete the cer-score-card.md file that produced it. The plan's scoring history is not lost: it lives in the manifest and in git history, not as loose score-card files.

Inputs

• Target document. A plan by default, but this skill can run on anything CER can grade — a plan, a phase, or a story summary. Locate it via Agentic Rails plan paths (context/implementation-plans/<task-folder>/plan.md) or an explicit path the user gives. If ambiguous, ask.
• Thresholds. Come from references/model-matrix.md, not from the user. The tier-1 (local) threshold is (5, 5, 5) — a provisional seed, not yet calibrated against real completion outcomes. Treat it as authoritative until better data exists; do not let the user override it ad hoc.
• This skill reads the target, writes the manifest and phase files, and follows rails-grade-cer for every score. It does not execute the plan's work.

Already-Phased Check (do this first)

Before doing anything else, check whether the target folder already looks phased: a plan.md containing a Phase Registry table, or existing phase-1.md/phase-N.md files beside it.

If it is already phased, refuse: tell the user the plan is already phased, point them at the existing manifest and phase files, and stop. Do not re-phase, diff, or silently overwrite. If the user wants to redo phasing, they can say so explicitly and re-run this skill after reverting or removing the existing manifest state themselves.

A plan carrying only a single-unit CER annotation (see below) is not considered phased — it has no phase registry or phase files, so this skill may run on it again if its CER scores have since changed.

The Phasing Loop

1. Grade the target with CER. Follow rails-grade-cer on the whole document, all three axes, concise detail. Read the scores; delete the resulting cer-score-card.md.

2. Check against the tier-1 threshold (5, 5, 5) from references/model-matrix.md:

   • All axes < 5 → no phasing needed. Annotate the plan in place with a single-unit CER assignment block (see references/manifest-template.md, Single-Unit Variant) and stop. No phase files, no phase registry table — there is only one unit of work and it already fits the local model.
   • Any axis ≥ 5 → phase it (continue).

3. Fracture at natural seams. Read the plan's own structure (its implementation steps, file groupings, and stated completion points) and group it into candidate phases, each a complete, testable increment (Principle 4). Aim for each phase to land all three axes under (5, 5, 5). Useful hints, not rules: bundle setup/scaffolding work into an early phase, cut at points the plan itself already treats as checkpoints, keep a step and everything it strictly depends on in the same phase, and never propose a cut that would leave the app non-compiling or a feature half-wired.

4. Ceiling check — before writing anything. Count the candidate phases. If more than 7, stop immediately: do not write phase files, do not modify the original plan. Escalate to the human (see the Seven-Phase Ceiling section below) and end here.

5. Write draft phase files. For each candidate phase, write phase-1.md … phase-N.md beside the original plan using references/phase-template.md, with the phase's slice of the work but placeholder frontmatter (no scores yet).

6. Re-grade every phase with CER. One CER invocation per phase file just written, identical in method to step 1. Embed the resulting three scores into that phase file's frontmatter. Delete each resulting cer-score-card.md after reading it.

7. Resolve phases that will not drop below threshold. If a phase still breaches (5, 5, 5) after natural-seam grouping — because merging was needed to stay testable, or the work is inherently heavy — do not over-cut it further. Assign it up references/model-matrix.md to the lowest tier whose thresholds cover all three of its scores. Leave it as one phase at that tier.

8. Assign models and rewrite the manifest. Every phase gets an assigned model in the manifest's phase registry and a matching recommended model in its own frontmatter. Rewrite the original plan.md in place into the manifest using the Full Manifest Variant in references/manifest-template.md.

9. Report. Tell the user the manifest path, every phase file path, each phase's assigned model and scores, and whether any phase was tiered up instead of reduced.

Model Capability Matrix

See references/model-matrix.md for the full tier table. Summary: a phase is assigned to the lowest tier whose thresholds cover all three of its axes — a phase at (5, 4, 8) needs a tier whose risk threshold is at least 8, even though its complexity and effort would fit tier 1. The tier-1 threshold (5, 5, 5) doubles as the phasing target: this skill tries to make every phase fit tier 1 before accepting a higher tier.

The Seven-Phase Ceiling

Seven phases is the hard ceiling. Needing an eighth means the target is mis-tiered: it is a story that should be split into at least two stories before phasing.

On breach, this skill does not produce phase files and does not touch the original plan. It stops and tells the human plainly: this is too many phases for one unit of work, so split the original into multiple stories at the Story tier, then run this skill on each story separately. Name the problem; do not attempt the story split yourself — that is one tier up, and this skill's job stops at phasing.

The Manifest

The original plan.md is rewritten in place into a manifest when phasing occurs. No separate copy of the pre-phase plan is kept — git history holds the previous version. A parent plan sitting alongside its own phases would just create conflicting sources of truth.

The manifest is the single source of truth and the communication channel between sub-agents: an orchestrator reads it, spins up a sub-agent for the next phase, hands it the manifest plus that phase file. The sub-agent executes, writes its status and notes back into the manifest's phase registry row, and returns. The next sub-agent sees the updated state.

Keep the plan-level context carried into the manifest short: one paragraph condensing the original goal/objective and high-level scope. Do not copy the full original plan body verbatim — the detail that mattered for execution now lives in the phase files, and the original wording remains fully recoverable from git history. See references/manifest-template.md for the exact structure and the phase registry table schema.

Phase Files

Phase files are small plans — same shape as any Agentic Rails plan, just guaranteed small (fits under threshold, or is the smallest legal testable unit at its assigned tier).

• Naming: phase-1.md, phase-2.md, phase-3.md … Sequential integers only. Never a content-based name — a descriptive name adds nothing for a smaller model loading one specific phase file and only invites drift from the registry.
• Location: the plan's existing folder, beside the manifest.
• Structure: frontmatter carries the recommended model and the three CER scores; the body carries the same kind of content a plan uses (objective, steps, verification, acceptance). See references/phase-template.md.

This is progressive disclosure in practice: a sub-agent working phase 2 loads only phase 2, not the entire original plan. It reads the manifest for state and its own phase file for the work — nothing more. The manifest's assigned model for a phase and that phase file's own recommended model must always agree; if they do not, something in the phasing process broke and should be corrected before reporting done.

Hard Rules

• Never break the build. No phase leaves the application non-compiling or non-running. A phase must be independently testable. This outranks hitting the threshold.
• Sequential only. Phases run in order. Never emit or imply phases can execute out of order.
• Local first. Always try to fit tier 1. Only tier up when no legal phasing gets a phase under threshold.
• Never over-cut. Do not split past what natural seams allow just to force a lower score. Assign up the tier instead.
• Stop at seven. More than seven candidate phases → escalate to the human as a mis-tiered story. Emit no phase files, touch no existing files.
• Rewrite, don't duplicate. The plan becomes the manifest in place. No parallel copy of the pre-phase plan.
• Don't execute. This skill phases, grades, and assigns models. It does not do the plan's work.
• Grade via CER only. Every score comes from following rails-grade-cer. This skill holds no rubric of its own.
• Don't litter grading artifacts. Delete each cer-score-card.md after reading its scores; the scores live in the manifest and phase frontmatter.
• Refuse on already-phased targets. If a manifest and phase files already exist for the target, stop and tell the user — do not silently re-phase or overwrite.

Validation

Before considering this skill applied correctly, confirm:

• The already-phased check ran first, and the skill refused rather than silently overwrote an existing manifest.
• Every score used in the manifest or a phase's frontmatter came from a rails-grade-cer invocation, not an invented number.
• No cer-score-card.md files remain in the plan's folder after this skill finishes.
• If no phasing was needed, the plan received a single-unit CER annotation and no phase files were created.
• If phasing occurred, there are between 1 and 7 phase files, each named phase-N.md with sequential integers, each independently testable per the plan's own structure.
• Every phase's assigned model in the manifest matches its own frontmatter's recommended model, and is the lowest tier whose thresholds cover all three of that phase's scores.
• If more than 7 candidate phases were found, no phase files were written, the original plan was left untouched, and the human was told to split at the Story tier first.
• The manifest's plan-level context is a short condensed paragraph, not a verbatim copy of the original plan body.
• The user was told the exact paths of the manifest and every phase file, plus a summary of model assignments.