# 2026-08-01 — CB-WP-0008 delivery notes

Kept out of the workplan file so it stays loadable (`loop-lint`).

## T01 — bots

`games/ground/src/bot.rs`, 8 tests. `Policy` + `RandomPolicy` (seeded
`ChaChaRng`) + `GreedyPolicy` (stated heuristic, deterministic), a
`legal_commands` generator that filters candidates through `validate`, and
a driver that reaches `GameEnded`.

Measured, 3-player, seed 42, both policies to GR-R09's fifth round:

| policy | commands | events | claimed | total vs threshold |
|---|---|---|---|---|
| random | 36 | 81 | 1 | 2 / 7 |
| greedy | 30 | 51 | 2 | 3 / 7 |

**The module is not gated on `scenarios`; its tests are.** A bot needs
only the aggregate, but the setup presets live behind that feature. That
is a real seam and it is left visible rather than papered over with a
feature the bot does not need.

### What the second consumer found

INTENT's second-use rule is why T01 was worth doing before the CLI. Three
findings, none of them fixed here, because fixing a rule from inside a bot
is exactly the invention-in-isolation the rule guards against.

1. **GR-A13 admits SOLVE against an already-claimed Problem.** The rule
   names "a face-up, non-Denied Problem"; `claimed_by` is not mentioned,
   so `check_targeting` accepts it and resolution then does nothing. The
   action is silently wasted. Greedy hit this immediately — it spent all
   fifteen selections re-solving Problem 1 and scored 1. The **policy**
   now avoids it; the **rule** is untouched and this is a U-item
   candidate for GroundRules.

2. **The 3-player standard fixture cannot succeed.** GR-S01 gives 3
   Problems at 3–4 players, the preset values them by priority (1, 2, 3 —
   maximum 6), and GR-E01 sets the 3–4p threshold at **7**.
   `group_success` is therefore unreachable at 3 players regardless of
   play. No scenario noticed because no scenario plays to scoring with
   maximal claiming. The fixture is documented as placeholder ("Problem
   content is scenario data") — so this is evidence that the placeholder
   is not neutral, not that GR-E01 is wrong.

3. **K13's `Project` trait has zero implementors.** `grep` finds no
   `impl Project` anywhere in the tree. T02 is its first consumer, and
   the projection will be written against a trait that has never been
   exercised.

### Process

The acceptance tests were mutation-checked by hand (no `mutation-check`
row — that denominator is the GameKernel acceptance table, and adding a
game-level row would move a metric by changing its question).

**The first mutation was a no-op and SURVIVED**: it changed
`apply(...)?` to `let _ = apply(...)`, which still issues the command.
Removing the `Resolve` call outright turned three tests red for their
stated reason. Third recorded instance of the weak-mutation class — the
retrospective in `260801-instrument-the-table-retrospective.md` predicted
mutation strength would stay a standing maintenance cost, and this is
that cost arriving on the next pass.

## T02 — `cb-play`

`tools/cb-play` (`make play`), 6 tests. A human seat is a `Policy` like
any bot, so the CLI adds no second driver: `HumanPolicy` renders the
projection, lists the legal commands, and reads an index or `pass`.

- **K13's first implementor** is `games/ground/src/view.rs`. Hidden:
  other seats' face-down selections until Reveal, hands (count only), the
  undealt deck (count only), a face-down Problem's suit and value, and
  **the seed** — not secret content, but a seat holding it can compute the
  deck.
- **A played session becomes an artifact.** `--record FILE` writes it as a
  scenario the runner executes; `--replay DIR` writes a `.cbreplay`
  bundle. `games/ground/src/record.rs` is the inverse of
  `parse_command`, and its warrant is a round-trip test over every
  command shape — an encoder checked against hand-written expectations
  only agrees with itself.

### Two vacuous tests, caught by counting

The acceptance clause *"a seat's projection never contains another seat's
hidden selection"* passed twice while asserting nothing.

1. The first version asserted the rendered text contained `face-down` —
   which it does, from **Problems**, in every game ever rendered.
2. The counted version then reported **0 inspected entries**: seats are
   asked in order, so a human at P1 is always prompted before anyone has
   selected and never sees a hidden selection at all.

Seating the human at **P3** exercises the rule; the test now counts what
it inspected and requires at least four. Mutating the projection
(`revealed = true`) fails it for its stated reason.

This is the same class as the AM-2 `expect` that matched passing output —
an assertion that cannot distinguish the two worlds. The remedy that
worked both times was **counting what the harness examined**, not
strengthening the predicate.

## T03 — the 2–6 player range

Every scenario in the corpus was 3-player. Now: `gr-o01-two-player`,
`gr-o01-six-player`, `gr-e01-threshold-unreachable-2p`, plus all-bot
games at every count under both policies, each reproducing at the same
seed (K8 at the boundaries, not only in the middle), and the CLI
transcript test run at 2p, 3p and 6p.

**Nothing broke.** The rules are seat-count-generic and the range works.
What the boundaries exposed is arithmetic:

| seats | Problems | best possible total | GR-E01 threshold | group success |
|---|---|---|---|---|
| 2 | 2 | 3 | 5 | **unreachable** |
| 3 | 3 | 6 | 7 | **unreachable** |
| 4 | 3 | 6 | 7 | **unreachable** |
| 5 | 4 | 10 | 9 | reachable |
| 6 | 4 | 10 | 9 | reachable |

With the standard preset's placeholder values (value = priority), *no
play at all* can clear the threshold below five seats. GR-S01 calls the
fixture a stand-in for scenario Problem data, so this is evidence the
stand-in is not neutral — not that GR-E01 is wrong. It is pinned three
ways: a scenario that passes on the fact, a test that asserts the
arithmetic, and a `provisional` marker with `ground-game` as owner so it
ages in `make coverage` (now 6 provisional defaults).

The test carries its own delete-by condition: **it is expected to fail**
when Problem values become scenario data, and that failure is the signal
to delete it rather than re-tune it.

Two smaller notes, recorded and not acted on: at 2 players GR-L01's
second relation slot can never be used (there is only one possible
partner), and a human at P1 is always prompted before any other seat has
selected, so the seat order makes P1 a weaker test position than P3.