Dos Plan Price

dos-plan-price — price the fan-out before you launch it

DOS is a court; this skill asks it to quote a price first. Every other DOS trust surface reads the past or present tense: verify reads a commit that already shipped, arbitrate refuses a colliding acquire as the worker reaches the turnstile. A court rules after the collision. But the cheapest moment to catch a colliding fan-out is before any worker runs — and the kernel's own file-tree geometry can answer that forward question with zero new trust: the partition's overlap is a fact about glob prefixes, decidable without believing any agent's intent (docs/347, the predictive flip). This skill prices the proposed partition so a bad plan is refused with 0 agents launched, instead of the reactive court launching K-1 workers before the Kth acquire collides.

The shape is domain-free: discover the layout → collect the proposed partition → price it from the un-authored geometry → act on the price → fall back to the reactive lease floor. The policy (which lanes exist, where things live) is data read from dos doctor --json, never literals.

When to use this (and when not)

• Use it right before a fan-out: a dos-goal-fleet wave, a dos-next-up packet's dispatch list, or any "launch N agents over these trees" moment. The dispatch list IS a proposed partition; price it before you spend the launches.
• Do not use it for a single agent (N=1 has no partition to price — the price is trivially 0), or as a substitute for dos arbitrate at acquire time. The price is a forward estimate; the lease arbiter is the unforgeable floor. This skill runs ahead of the floor, it does not replace it.
• This is a layer-3 helper / screenplay (a PDP, docs/99). It mints no new verdict; it reads the kernel's pure geometry and narrates the price. The geometry is the judgment; this skill is the narrator.

The honest seam — no first-party verb yet (read this before Step 2)

There is no dos price-plan CLI verb today (it is filed as issue #178). The un-forgeable primitive the price stands on IS shipped: dos._tree.lane_trees_disjoint, the same agent-blind prefix geometry dos arbitrate already trusts. The reference implementation that lifts that pairwise predicate into a whole-partition price is the kernel's own experiment, examples/plan_price/plan_price.py (a clean price_plan(agents) -> PlanPrice API and a --json main; docs/347).

So this skill shells/imports that example as the interim primitive and emits a one-line log naming the gap — exactly the docs/345 discipline for a step whose first-party verb does not exist yet. It never pretends a dos price-plan verb is there. If the example (or the kernel) is absent, the predictive step degrades to advisory and you fall straight to Step 4 (the dos arbitrate floor), which is always available.

Step 0 — Discover the workspace once (the WCR on-ramp)

dos doctor --workspace . --json

Stash it. The fields this skill uses:

• lanes.trees — the active lane→file-tree map. If a proposed worker is named by a lane rather than an explicit tree, resolve its tree from here (never a literal).
• paths.root — so declared trees are workspace-relative, comparable by the geometry.
• git — informational; the price needs no git history (it reads the proposed partition, which has no commits yet — that is the whole point).

Step 1 — Collect the PROPOSED partition

Build the list of agents the fan-out is about to launch, each with the file-tree it would be handed (globs). The source is whichever planner you are gating:

• A dos-goal-fleet wave → one entry per objective, its declared scope.
• A dos-next-up packet → one entry per dispatch-list pick, the plan's load-bearing files as its tree.
• An operator's hand-written "these N agents over these trees" → as given.

Each entry is {name, tree: [glob, ...]}. An agent whose tree you cannot resolve — an empty/unknown blast radius — is kept with an empty tree on purpose: the geometry will (correctly, conservatively) price it as colliding with everything, which is the signal "name this worker's scope before you launch it."

Step 2 — Price the partition BEFORE launch

Compute the price from the un-authored geometry. Shell the interim primitive and log the gap in the same breath:

# interim — no `dos price-plan` verb yet (#178); the example lifts the shipped
# `dos._tree.lane_trees_disjoint` predicate into a whole-partition price.
python examples/plan_price/plan_price.py --json

…or, for your own partition rather than the example scenarios, import the API:

from plan_price import Agent, price_plan          # examples/plan_price/
price = price_plan([Agent(name, tree) for name, tree in proposed])

Then emit the gap note so it is surfaced at runtime, not just documented here:

log: predictive price is example-backed (examples/plan_price) pending the
     first-party `dos price-plan` verb (#178); the underlying predicate
     (dos._tree.lane_trees_disjoint) is the shipped kernel geometry.

The price (PlanPrice) carries:

• collisions — the proposed pairs that provably overlap (one is a prefix of the other in the prefix algebra). These are the launches you must not spend yet.
• max_concurrency + safe_now — the largest set of proposed agents that can run at once with no collision (the maximum independent set on the collision graph), and their names. This is the honest "how many of these N can actually run together" — a number the per-acquire arbiter never computes.
• repartition — for each colliding agent, the narrowest private subtree that would clear it. A geometric suggestion (it cannot know the agent's true intent), so treat it as the shape of the fix, not the fix.
• expected_rework — a transparent contention price (monotone in collisions); ordinal, not a calibrated cost (calibration is #179).

Step 3 — Act on the price (the court → oracle move)

This is the value. Branch on the price before launching:

• 0 collisions → launch the full fan-out. The price added no friction (the falsifier: when the partition is truly disjoint, the lift is exactly 0).
• ≥1 collision → do not launch the colliding plan. Pick one:
  • Launch only safe_now this wave (the maximal disjoint set), and hold the colliding agents for a later wave; or
  • Apply the repartition suggestion (narrow the colliding trees), re-run Step 2, and launch once the price is 0.

Either way you have refused the bad plan with 0 agents launched. Contrast the reactive court (Step 4): admitting agents one at a time, it only refuses when the colliding acquire arrives — by which point the earlier agents have already launched and are mutating the tree. The measured gap (docs/347): on a 4-agent plan with one hidden overlap, the reactive court launches 2 agents before it can refuse; the price refuses with 0.

Step 4 — The reactive floor still applies (EXAMPLES.md R2, dos arbitrate)

Pricing the plan does not replace the lease floor. Every worker still takes its lane lease at acquire time — the unforgeable check over the leases actually held:

dos arbitrate --workspace . --lane <lane>      # honor the verdict; redirect on refuse

Be explicit about why both exist: the predictive price is a forward estimate over an agent-declared (and therefore forgeable) partition — it reduces wasted launches and surfaces the collision early, but it is not a guarantee. dos arbitrate over the real WAL leases is the floor that cannot be talked around. Price first to save the launches; arbitrate at acquire to be safe.

Step 5 — Return

Print the price and the recommended action, so a caller (dos-goal-fleet, dos-next-up) can chain it:

Priced <N> agents: <C> collisions, max safe concurrency <M> (run now: <safe_now>).
Action: <LAUNCH_ALL | LAUNCH_SAFE_SET | REPARTITION_AND_REPRICE>.

Return the action as the final line so the launch step branches on it, not on prose.

What this skill deliberately does NOT do (no silent gap)

• No first-party verb. It shells examples/plan_price because dos price-plan (#178) is not built. It logs that gap every run rather than faking the verb.
• No semantic collision detection. The price is geometric — it catches two trees that overlap by prefix, not two disjoint trees whose intents conflict (the docs/347 §5 ceiling, shared with arbitrate). It moves collision latency earlier; it does not widen what geometry can see.
• No leasing. It computes a price; it journals no lease. The lease is dos arbitrate's job at acquire time (Step 4). The price is advisory until then.

Log the gap, never silently skip it. The first time the skill prices a partition without the first-party verb, emit the one-line log from Step 2 — so the capability gap is visible at runtime, not just here.

Anti-patterns

• ❌ Launching a plan the price flagged as colliding "because arbitrate will catch it anyway". That is the reactive court — you spend the launches you could have saved. Price first; launch the safe set or re-partition.
• ❌ Treating the price as the unforgeable floor and skipping dos arbitrate at acquire. The price is a forward estimate over a forgeable declared partition; the lease arbiter is the floor. Do both.
• ❌ Faking a dos price-plan call. The verb does not exist yet (#178) — shell the example and log the gap.
• ❌ Naming a specific lane or path as a literal — resolve trees from dos doctor --json (lanes.trees).
• ❌ Pricing a single agent. N=1 has no partition; the price is trivially 0.