# Earned rules

Rules this campaign paid for. Each one exists because it was violated first and something wrong got
published, or nearly did. Lane briefs should reference this file rather than restating it.

Ordered by how much damage the violation caused.

---

## 1. A green verdict is not evidence. Coverage is.

`tracecmp` exit 0 means "the declared regions agreed". It does **not** mean the hook compared
anything. B4 found three hooks that each printed `0 diverged` while comparing nothing:

- `describe_args` ran **before** `regions()`, so every logged argument was one call stale;
- the `StrategyServer` has **two bases 4 bytes apart** — reading the wrong one yields an empty
  player vector, zero declared regions, and a confident "1 call, 0 diverged";
- a Ghidra-base number was used as a raw struct offset (`0x64` vs `0x60`), enumerating a vector's
  spare capacity.

Structural fixes now in place: compile-time-required `Coverage` on every descriptor (a hook without
one does not compile), guard regions that **localise** undeclared writes by offset rather than
reporting that a hash moved, replace-mode records, and `tracecmp --strict-coverage`. A hook claiming
"complete" while a guard caught an undeclared write counts as a **divergence**.

**Read the trace, not the verdict.** Every hook bug above was visible to a reader and invisible to
the exit code.

## 2. Write the prediction down before the run

Commit the expected result *before* building, not before running. Lane U committed its prediction
before the build was even staged; lane P wrote its expected residual (`next_id` short by exactly 1
on every completion call) and lane V confirmed it live.

The strong form: **a prediction that survives a changed workload tests the model, not the
recording.** Lane U's call 9 was not the call its prediction was written against — the AI had picked
a different tech — and it unlocked three nodes at costs appearing in no earlier report. Numbers that
never occurred cannot have been memorised.

Include a falsification section: how the model could be wrong, and the symptom of each way.

## 3. Static reading finds what behavioural comparison cannot

Both of these compared clean and were still wrong:

- `ApplyTechEffect` had an early return that would have made **every real call a no-op**;
- the RNG divisor was wrong on 0.78% of draws and flipped **zero** decisions in 10⁶ trials.

Conversely, behavioural compare found the `MoveFleet` rounding that static reading had missed. They
are different instruments. Use both; trust neither alone.

## 4. Prefer the instruction stream to the decompiler for control flow

**An inlined `std::vector` destructor looks exactly like a branch.** The `je` skips only the
`operator delete`; both arms converge a few hundred bytes later. This has produced two wrong
published findings — `turn-spine.md`'s "deferred end-of-turn tail" (there is no such branch) and a
near-miss on `Streamable::Write`.

Any decompiler `if` that wraps a whole tail is suspect until you have found the converge point in
the disassembly.

## 5. Size structs by enumeration, never by what the code touches

`_Alval` is `std::allocator<char>`, an **empty class**: it occupies a word and is never loaded or
stored, so it is invisible to touch-based analysis and undercounts by exactly 4. That produced a
`std::string`-is-0x18 scare against a correct campaign-wide 0x1c.

An **enumeration** — serializer, constructor, copy constructor, or container stride — can show
**absence** where a touch-scan cannot. Same trap is live for `std::vector` here:
`{_Myfirst,_Mylast,_Myend,_Alval}` = `0x10`, **allocator-last**, the opposite of the shape the MSVC
textbooks describe.

Related: the on-disk primitive is **not** the memory kind. A member held as `int16`/`int8` is
written by `WriteInt` and is **four bytes on the wire**.

## 6. A path no save exercises is a hypothesis

Label it as one. `spies2`, `SysMem` and `mts` were "closed" with count 0 in every save — no element
value has ever been observed. Lane A later found the element typing was wrong, and it was invisible
*precisely because* nothing exercised it. The flagging discipline is what made that checkable.

**Saves can be manufactured.** No species-5 save existed, so lane V built one and closed a row that
had been disassembly-only for a day. Prefer building the workload over weakening the claim.

## 7. Round-trip byte-identity is not coverage

`ar.any` bodies round-trip trivially by copying bytes nobody understands. Measure the split between
items a field **names** and items a node merely **carries**. That reframing moved a "100% round-trip"
result to an honest 38%, and then to 99.9% by actual work.

## 8. Two independent-looking checks sharing a hidden assumption are one check

`save_reader.py` types items from its **own** kind catalog, not the schema passed to it — so on real
saves the catalog and the schema agreed with each other and were **both wrong**. Its failure mode is
silent agreement, not a desync.

## 9. Rankers rank; they never filter

A cohort/frequency ranker would have **discarded the correct answer**: the function that appends to
`ObservedTech` touches only two offsets on `ServerPlayer`, so every `--min>=1` cohort filter drops
it. What closed the case was a plain query plus one call-graph lookup.

Displacement scan for recall, call graph for disambiguation. Neither alone sufficed. And report the
false-positive rate honestly — that scanner's class-level precision is ~13% by function; its value
is a 900× search-space cut, not accuracy.

## 10. Derive experiment parameters from the ISA, not from assumed mnemonics

An x87 sensitivity experiment was briefed as `0x027f / 0x127f / 0x137f`. In fact `0x027f` is 53-bit
(differing from `0x127f` only in infinity control, ignored since the 387) and `0x137f` is 64-bit
extended. Run literally it returns "all three identical" — true, and the conclusion drawn from it
would have been wrong on both axes, because it tests single precision not at all and rounding not at
all. The real probes are `0x007f` and `0x1a7f`.

**Brief lanes to challenge the parameters, not just execute them.** Lane F did, and lane G rejected
its brief's premise outright and was right to.

## 11. Correcting the record beats defending it

Claims downgraded on evidence, by later lanes: "RNG matched 15/15" (workload luck, not a property);
B1's and B4's coverage after the harness audit; `StreamableEnum` typing; the deferred end-of-turn
tail; "the research roll draws exactly one NextFloat" (the branch it fires draws a second).

If you find an earlier finding wrong, say so plainly and correct it in place. Nothing here is
anyone's reputation.

## 12. Fix the oracle openly, never quietly

Four defects were found in the reference save reader. The right move was **not** to patch them
mid-campaign in silence: they were recorded, then fixed openly with a test per defect and
byte-neutrality proven at item granularity (offset sequences identical across ~39,000 offsets per
save; typed-value deltas balancing to the byte).

## 13. Run verification gates as separate commands

Never `&&`-chain them. Once, a clean-room failure short-circuited the chain, skipping build and test
while a separate push still ran — an unverified tree reached `main`.

On one merge **both** gates failed and both were real: a raw `FUN_xxxxxxxx` identifier had reached
`docs/` in the public-capable engine repo, and the **shim cross-build** hit `-Werror=unused-function`
on a WIN32-only TU. Host `ctest` passed cleanly both times and would have hidden both.

**If a lane cannot cross-build its own shim TU, it must say so, and the integrator must run the
CT111 shim build before pushing.**

## 14. Never hand-resolve a generated header

Always regenerate from `ghidra/addresses.json` plus the `ghidra/addresses.d/<lane>.json` fragments.
Hand-resolving a merge conflict there silently dropped a new entry and broke the build — twice.

Per-lane fragments exist because a shared single file caused three cross-lane sweeps in one day.
Duplicate names across fragments are a **hard error**, never last-wins: two lanes disagreeing about
an address is exactly what must not be papered over.

## 15. Report thin coverage as loudly as divergences

A green run that establishes twenty facts is not a strong result. `ComputeBudget` compared 4,284
calls with 0 divergences — but only **20 distinct states**, with 4,278 of them the UI polling one
player, and **13 of 22 slots zero on every call**, including 5 of 6 declared input-boundary slots.

The most useful sections of the best reports here have been the honest lists of what was *not*
covered.

## 16. Inlined draws are invisible to call-graph sweeps

The combat resolver's `NextFloat` is **inlined**, so the only call-graph edge it leaves is
`caller -> RNG_Twist`, which reads as a bare Twist and is not one — it is the lazy twist *inside*
`NextFloat`. Lane K's "no NextFloat in that subtree" was wrong for exactly this reason.

An image-wide scan for the MT tempering immediates at instruction boundaries finds **14 game
functions with inlined draws that no RNG call-graph sweep can see**, two of them inside
`ProcessTurn`'s closure at depth 4.

Scan for the **constants at instruction boundaries**, not for calls. Any RNG accounting built from
the call graph alone is a lower bound.

## 17. A truncated range makes a loop look like a sequence

Lane J read a function as straight-line because it dumped the range at **Ghidra's reported size**,
and the outer back-edge fell just outside it. A delegated sweep made the same mistake independently.
That changed the draw count of the very site it was there to measure.

This is the same defect lane X hit from the other side: clipping sweeps at `fva + sizeInBytes` lost
**11%** of functions to mid-instruction truncation, and sweeping to the *next function start* took
coverage 89% -> 100%. Ghidra's size is also simply wrong sometimes — it gave 7,499 bytes for a body
that is 7,641 and ends mid-instruction.

**Never trust a function's end. Disassemble to the next function start and find the real boundary.**

## 18. Measure first. The lab exists.

We have the game running under a hook framework, a debugger, 11 curated saves, a byte-identical
autosave oracle and a state-checksum tool that localises to named leaves. **Use them before deriving
anything.**

The RNG gap is the case study. Static analysis spent several lanes on it and produced a complete
draw-site inventory with an unexplained count — genuinely good work that could not close. The answer
came from ten minutes of live hooking: return-address capture on the entry points attributed every
word in one turn, and the dominant consumer turned out to hang off a **virtual** edge that no
direct-edge closure could ever have reached.

The general shape: **static reading is for explaining what you measured, not for predicting it.**
Derivation is the fallback when the path cannot be reached, not the default.

A question of the form *"what writes this?"*, *"how many times does this run?"*, *"does this branch
ever fire?"* is a **watchpoint or a hook**, not a week of reading. Open items that fit that shape
right now: the `Player.Status` writer between tail phase 31 and the autosave; the `TShn`/`ltis`
writer; `Summary.Checksum`'s inputs; whether a trade-raid roll ever succeeds (a word count cannot
separate "no success" from "empty candidate list" — a hook on the callee separates them instantly).

Corollary, from the same session: **search the notes before the binary.** The dominant RNG consumer
was already identified in `strategic-turn-internals.md` months of lanes earlier. What was missing was
never the identification — it was the connection.