# The RNG ledger for one strategic turn — measured, not inferred Lane Z, 2026-09-08. Program `sots` / "Sword of the Stars.exe", ImageBase 0x00400000, all addresses VAs. Engine worktree `wip/tailrng`, `sots-engine/docs/Z-tail-rng.md` (the prediction, committed before the build). **The question.** The milestone is *a standalone that loads a save, runs one strategic turn, and writes an autosave that byte-matches the original's*. Generator state is part of the saved state. Lane K (`combat-done-tail.md` §3) found two draw sites in `StrategyServer::OnAllCombatDone_Tail` that nothing models and that both run **before** the autosave, and concluded that a reimplementation reproducing both `ProcessTurn` functions exactly would still diverge. Nobody had measured what a turn actually costs. **The answer, up front.** Across eight measured End Turns on two saves, a strategic turn advances the strategic generator by **18–22 words**, *all* of it inside `StrategyServer::ProcessTurn`, and the residual outside the two turn drivers is **exactly zero**. The tail's cost on these turns is **0**. The defect lane K found is real and **latent**: it will bite the first turn a node line expires or a real battle resolves, and our saves reach neither. --- ## 0. Where to start if you are building the standalone Three sentences, then the evidence. 1. A turn costs **18–22 generator words**, all of it inside `StrategyServer::ProcessTurn`; the two autosave files bracket exactly that interval and nothing draws between them outside the two turn drivers. 2. `verify/results/shim/tailrng/z-t6-endturn.sav` → `z-t6-autosave.sav` is a **byte-identical oracle pair with a known RNG cost of 18 words**, verified from the file bytes independently of the live hook. Test against that pair before any other. 3. Lane K's warning stands and is now quantified: the tail's cost is 0 **today** because no save is within ~40 turns of a node-line expiry (§9) and no encounter has ever produced a battle (§8). Both terms are real; both are latent. ## 1. The instrument, and why it is not an RNG hook Counting draws by hooking the primitives would have undercounted, and the campaign now knows by exactly how much. This lane's scan of the tempering immediates found **four** draw entry points where every prior lane's primitive set had three, and twelve functions with inlined draws. Lane J then found fourteen inlined-draw functions; lane I re-ran the scan at real instruction boundaries and audited it site by site, and its numbers are the ones to use: **seven entry points** and **eleven game functions with inlined draws over 28 sites**, with a brute byte scan finding zero orphans (`findings/control-flow/inlined-draws.md`). So the honest sequence is: three → four (this lane) → seven (lane I). The fourth, `Mars::RNG::NextUInt` 0x004f7670, is the one this lane's static work surfaced; the fifth, sixth and seventh — including `Mars_RNG_GaussianRange` 0x008e6e30, the only **unbounded** entry point at two words per attempt — are lane I's. Exactly **one** of the eleven inlined-draw functions is reachable from `StrategyServer::ProcessTurn` (0x007aa240, depth 4) and one more from the tail. **None of that changes a single number in this document**, and that is the point worth taking away. The instrument was never built from the primitive set or from the call graph: it reads the generator's **state** before and after a boundary and reports the difference. An inlined draw, a draw through an entry point nobody had named, a draw through a vtable — all of them move `left`, and all of them are counted. That is why method rule 16 (*any RNG accounting built from the call graph alone is a lower bound*) does not apply to it, and why three revisions of the primitive inventory landed underneath this measurement without disturbing it. The state it reads: `Mars::RNG` is `{void* vptr; uint32 mt[624]; uint32* next; int32 left}`, `sizeof 0x9cc` — `next` at +0x9c4 is a **pointer** into the block and `left` at +0x9c8 is the counter, and the inner primitives are entered with `ECX = &mt[0] = RNG+4` while the outer helpers take the object base and do the `add ecx,4` themselves — which is what lane T's "the generator is entered at `rng+4`" note was seeing. The draw is `if (left == 0) Twist(); y = *next++; --left;` — a pre-check against **0**, never −1. The block transform is a pure function, so the blocks a generator visits form a forward-only chain. `RngLedger` (`sots-engine/src/shim/hooks/rng_ledger.{h,cpp}`) indexes that chain from the first block it sees and positions any state exactly: ``` words(block, left) = block * 624 + (624 - left) ``` Differences between positions are then exact **across twists, across rejection loops, and across draws nobody hooked**. Nine host tests pin the arithmetic, including the block boundary (`left == 0` is a real state and must not be off by 624), a rejection loop counted against a shadow generator, and the out-of-order case below. **One ordering subtlety, and it is load-bearing.** `Hook<>` takes the `before` snapshot at entry but renders it (calls the region's `describe`) only *after* the original returns — so for nested calls the inner snapshots are rendered first, and by the time an outer `before` is rendered the chain has moved past it. Walking a Mersenne Twister backwards is not possible. Every hook therefore **observes at entry from `describe_args`**, which indexes the entry block while it is still current; the render then resolves it from the memo. Without that, every outer-call `before` would read `words: null`. Six nested trace hooks, all watching the object at `S+0x16c`: `StrategyHost::Autosave` (both markers) › `StrategyServer::ProcessTurn` › `OnAllCombatDone_Tail` › `ApplyEncounterResult` (phase 6) › node-line decay (phase 11) › `ProcessNodeSpaceTravel` (runs twice a turn). --- ## 2. The ledger Save `ref-turn2` (2-player Morrigi vs AI), four consecutive End Turns, build `z-tailrng-20260908T1314Z`, `hooks=trace`. Words are 32-bit MT outputs consumed by the generator at `S+0x16c`. | turn | `ProcessTurn` | tail | `ApplyEncounterResult` | node-line decay | `ProcessNodeSpaceTravel` ×2 | **bracket total** | **residual** | |---|---|---|---|---|---|---|---| | 3 | **19** | 0 | 0 | 0 | 0, 0 | (incomplete — see below) | — | | 4 | **18** | 0 | 0 | 0 | 0, 0 | **18** | **0** | | 5 | **20** | 0 | 0 | 0 | 0, 0 | **20** | **0** | | 6 | **18** | 0 | 0 | 0 | 0, 0 | **18** | **0** | "Bracket" is `Autosave(endTurn=1)` → `Autosave(endTurn=0)`: the pre-turn save file to the post-turn save file, which is exactly the interval a standalone has to reproduce. The turn-3 bracket is incomplete **by construction** and is reported rather than dropped: the pre-turn autosave of the first End Turn after a load runs before any turn driver, so the hook has no server pointer yet and its record carries `words: null`. A second save, `zuul-turn16-noderoute` (Zuul vs Zuul), build `z-tailrng2-20260908T1328Z`: | turn | `ProcessTurn` | tail | `ApplyEncounterResult` | node-line decay | `ProcessNodeSpaceTravel` ×2 | **bracket total** | **residual** | |---|---|---|---|---|---|---|---| | 17 | **20** | 0 | 0 | 0 | 0, 0 | (incomplete) | — | | 18 | **20** | 0 | 0 | 0 | 0, 0 | **20** | **0** | | 19 | **22** | 0 | 0 | 0 | 0, 0 | **22** | **0** | | 20 | **20** | 0 | 0 | 0 | 0, 0 | **20** | **0** | **So: we consume 18–22 words per turn and model 0 of them.** Not 0 because the modelling is bad — because *nothing in the repo models any part of a turn's RNG consumption as a count*. B1/B3/B4 compare the generator's state around three specific functions and get it right; no lane has ever stated a turn's total. This table is that statement. ### 2.1 The generator does not move outside the turn pipeline Every turn's `ProcessTurn` entry position equals the previous turn's post-turn autosave position, exactly: 211 → 211, 229 → 229, 249 → 249. The UI, the renderer and the per-frame tick draw **nothing** from the strategic generator between turns. For the standalone this is worth as much as the total: the interval it must reproduce is closed. --- ## 3. An independent check, from the files rather than from memory The two autosaves of the turn-6 bracket were pulled off the VM and their `Sim.RNG` blobs parsed by `verify/save-reader/save_reader.py` (the frame's payload is 2503 bytes: `mt[624]`, then `left` as int32 at +2496). Twisting the pre-turn block forward until it matches the post-turn block, and applying the same position formula: ``` z-t6-endturn.sav (pre-turn) left = 375 z-t6-autosave.sav (post-turn) left = 357 twists = 0 -> words consumed between the two files = 18 ``` The live ledger recorded 18 for that turn, `left` 375 → 357. **Two instruments that share no code path — one reading process memory through a hook, one reading gzip-compressed file bytes through the save reader — agree exactly.** Files and the checker in `verify/results/shim/tailrng/`. **And the two do not share a hidden assumption** (the trap of method rule 8, which is live here because both sides know how to twist an MT block). `twists = 0`: the block is byte-identical in the two files, so the file-side number is `left_before − left_after` and involves the twist implementation **not at all**. The agreement is therefore about the game's behaviour, not about two copies of the same algorithm agreeing with each other. This is the pair a standalone should be tested against first: it is a byte-identical oracle *with a known RNG cost attached*, which none of the eleven corpus saves has. **A second pair was produced by the later per-site run and agrees the same way.** `z2-endturn.sav` → `z2-autosave.sav` (the turn-4 → turn-5 bracket of `ref-turn2`) gives `left` 395 → 375, `twists = 0`, **20 words** — matching both the boundary ledger's bracket for that turn and §11's per-site sum. So on turn 5 of `ref-turn2` **three instruments that share no code path agree on 20**: a hook reading process memory around a phase boundary, a set of detours keyed by return address, and the two save files on disk. | pair | turns | `left` | words | |---|---|---|---| | `z-t6-endturn` → `z-t6-autosave` | 5 → 6 | 375 → 357 | **18** | | `z2-endturn` → `z2-autosave` | 4 → 5 | 395 → 375 | **20** | --- ## 4. Lane K's inference, settled > **§6, labelled hypothesis:** "I did not prove that `SNMAllCombatDone` is delivered on turns with no > combat." **The handler runs on every End Turn.** Eight out of eight, across two unrelated saves, `OnAllCombatDone_Tail` recorded exactly one call per End Turn, at depth 0, between the two autosaves, with the post-turn autosave following it. The determinism-note inference was right. The stronger claim — that it runs with an *empty encounter vector* — is **not** settled by this workload and must not be reported as though it were. On **both** saves the encounter vector is **empty at `ProcessTurn` entry and holds exactly one encounter by the time the tail runs**, on every one of the eight turns: detection (`ProcessTurn` phase 31) creates it, and the tail's phase 7 clears it. So what is proved is "the tail runs on a turn with **no battle**", not "on a turn with no encounter at all". See §8 for what closing the remaining gap needs. Two things fall out of the same records and are worth more than the phrasing: * **Phase 7 really is a wholesale `clear()`.** `encounters` reads **1** at the phase-6 `ApplyEncounterResult` call and **0** at the phase-11 node-line-decay call, on every turn. Lane K read that off the instruction stream against a decompile that reads as a conditional prune; it is now also a behavioural fact. * **Every encounter on these turns has `res->+0x4 != 0`** (`res_no_battle = 1`), the flag that makes `ApplyEncounterResult` a whole-function no-op. Its measured cost is 0 words, which is what that gate predicts, and which is why the combat resolver has never run under any instrument this campaign has built. --- ## 5. `S+0x8` has a name, and it is `ModCount` — correcting `combat-done-tail.md` §7.1, lane T §0.1, `addresses.json`, and this lane's own prediction Lane K wrote that `S+0x8` "advances **at least twice** per turn" and that "the word at `S+0x8` has never been named" (lane T §0.1). The first is right and this lane's prediction that it advances **exactly** twice is **wrong**. The second is now answered — by `StrategyServer::Write`'s own wire tags: ``` 0079fb2f lea edx,[edi+0x08] ; push "ModCount" ; edi = S -- the same edi that indexes 0079fb40 lea eax,[edi+0x0c] ; push "Frame" ; the players vector at +0x54 ``` So **`S+0x8` is `ModCount` and `S+0xc` is `Frame`**, the turn number. `ghidra/addresses.json` has the name on the wrong word: its `StrategyServer_off_ModCount = 0x8` is the stored-frame offset of `S+0xc`, which the wire calls `Frame` — `turn-spine.md` was right to call it that and lane T flagged the clash without being able to settle it. The name `ModCount` belongs to the word lane T recorded as `StrategyServer_off_PhaseCounter = 0x4`. Confirmed three ways, and the third is the satisfying one. **From the saves:** | save | `Frame` | `ModCount` | |---|---|---| | turn1-state / turn2-state / turn3-state | 1 / 2 / 3 | 0 / 12 / 24 | | z-t6-endturn / z-t6-autosave (this lane's bracket) | 5 / 6 | 50 / 62 | | zuul-turn16-noderoute / zuul-turn23-fleet23 | 16 / 23 | 241 / 412 | `Frame` is the turn; `ModCount` moves **+12 per turn** on the early Human game and averages **+24** on the Zuul one. **From the live trace**, `S+0x8` at hook entry: | save | turn | `ProcessTurn` entry | tail entry | tail's callees | increments to the next turn | |---|---|---|---|---|---| | ref-turn2 | 3 | 22 | 23 | 24 | **12** | | ref-turn2 | 4 | 34 | 35 | 36 | **14** | | ref-turn2 | 5 | 48 | 49 | 50 | **12** | | ref-turn2 | 6 | 60 | 61 | 62 | — | | zuul-noderoute | 17 | 253 | 254 | 255 | **16** | | zuul-noderoute | 18 | 269 | 270 | 271 | **21** | | zuul-noderoute | 19 | 290 | 291 | 292 | **44** | | zuul-noderoute | 20 | 334 | 335 | 336 | — | The live deltas (12, 14, 12 on the Human game; 16, 21, 44 on the Zuul one) sit exactly where the saves' `ModCount` deltas say they should. The two turn drivers account for **2 of 12 to 44** increments; the rest are spread across the turn and mostly fall between the post-turn autosave and the next `ProcessTurn`. That is no longer a mystery to be chased — **it is what a modification counter is for**. `S+0x8` is not a turn number, not a driver-invocation counter and not a constant per turn: it counts state mutations, so it scales with the size of the empire, and asking "which writer is responsible" has no single answer. Lane K's operational conclusion stands and is now explained rather than merely observed. `S+0xc` (`Frame`) reads 3, 4, 5, 6 and 17, 18, 19, 20 over the same records and is the turn counter. **For the integrator:** this is a name collision to reconcile, not a new entry. `StrategyServer_off_ModCount` (0x8, stored frame) and `StrategyServer_off_PhaseCounter` (0x4, stored frame) are the two words above with their names swapped; `ghidra/addresses.d/lane-z.json` records the evidence under `StrategyServer_wire_ModCount_vs_Frame` rather than adding a third name for either word. ## 6. Corrections to `combat-done-tail.md` §3 and §6.1 Both from the instruction stream, both load-bearing for anyone reimplementing these functions. **§3 — the node-line fleet check does not gate the roll.** Lane K: *"The roll is skipped for a line if any fleet with flag `0x20000` is targeting it."* The straight-line order in node-line decay's first loop is ``` 0x007ae088 call NodePath::RemainingLife ; expiry test 0x007ae08f jg 0x007ae1e2 ; not expired -> next record, NO DRAW 0x007ae095 mov ecx,[esi+0x16c] ; THE DRAW 0x007ae0a5 call 0x008e6dd0 ; Mars::RNG::Chance(0.5f) 0x007ae0aa test al,al ; je 0x007ae1e2 ; roll failed -> next record 0x007ae0b2 ... ; THE 0x20000-FLEET SCAN STARTS HERE ``` The scan begins 0x1d bytes **after** the `Chance` call and is reached only when the roll *succeeded*. It suppresses the collapse (`0x007a92e0` / `0x007a4700`), never the draw. Lane K's headline — one `NextFloat` per expired node line per turn — survives intact and is now pinned to a formula. **§6.1 — `StrategyHost::Autosave` is `ret 8` and returns a value.** Its epilogue is `c2 08 00`, and `0x00895b5c mov eax,esi` puts the `std::string*` (the MSVC named-return slot) in EAX. A hook declaring it `void` drops EAX at both call sites. Neither call site passes `this`: both hardcode `mov ecx,0xb29f98`. (The `+0x54` candidate on that global was recorded live and is **not** the `StrategyServer` — `server_agrees` is false on all eight autosave records, so the global that the autosave uses is a different object from the `StrategyHost` whose `+0x54` `OnMessage` reads.) ### 6.1 The expiry predicate, now concrete `NodePath::RemainingLife` 0x006e2130, `__thiscall(NodePath*, int turn)`, `ret 4`, whole 122-byte body read: ```c if (npt(+0x04) == 0) return INT_MAX; // permanent line, never expires if (npdtn(+0x1c) == INT_MAX) return INT_MAX; // immortal line aged = (npctm(+0x14) >= 0 && turn >= npctm) ? turn - npctm : 0; wear = (npdtf(+0x20) != INT_MAX && npdtf > 0) ? nptf(+0x24) / npdtf : 0; // SIGNED idiv rem = npdtn - wear - aged; return rem > 0 ? rem : 0; // callee-side clamp ``` A line is expired exactly when this returns 0. **The lifetime is derived, never ticked** — the function writes nothing, and neither does the loop around it — so there is no decrement-ordering question and a snapshot at function entry is a valid prediction basis. `nptf` is never sign-checked, so the division's signed truncation must be reproduced literally. `Chance` 0x008e6dd0 returns **false with no draw** when `p <= 0` and **true with no draw** when `p >= 1`; `0.5f` takes neither, so it is exactly one word, and the comparison is `p > r` (equality returns false). A NaN `p` falls through both early-outs and *does* draw — irrelevant here, noted because it is the kind of edge a reimplementation gets wrong. --- ## 7. One generator, confirmed twice Static: the image has one persistent strategic `Mars::RNG`, at `S+0x16c`, constructed by the `StrategyServer` ctor 0x007d78d0 (`push 0x9cc` + `Seed(0)` at 0x007d7d25/0x007d7d3d) and reseeded only from `Read` and `LoadGame`. `StrategyClient+0x134` and `Mars::CombatSim+0x108` exist but are unreachable from the turn roots; three more are stack temporaries in map generation. **The combat resolver draws from the same `S+0x16c` object** — all three RNG entry points in its 750-node direct-call closure load `[reg+0x16c]`. Behavioural: across **64 ledger observations over eight turns on two saves**, every state resolved on a single forward chain — no `words: null`, no second chain. If a second generator had been in play, the ledger would have said so by construction rather than by anyone noticing. --- ## 8. What is not settled, listed as loudly as the results * ~~The combat resolver has never run under an instrument.~~ **It has now, once — see §10. It cost 0 words.** What remains unsettled is everything a single auto-resolved encounter cannot speak for; §10.2 lists it. * **Node-line expiry did not fire.** See §9 for the quantified distance rather than an absence. * **A turn with a genuinely empty encounter vector was not observed** (§4). Both saves produce exactly one sighting encounter on every turn. The tail-runs-every-turn claim is settled; the no-encounters variant is still an inference, now a much narrower one. * ~~`players` reads 8 on a 2-player save, and may be the `S+0x64` bug again.~~ **Resolved, and the flag was my own error.** The offset is right and so is the count. `StrategyServer`'s base-class ctor 0x0085b120 (entered with `ecx = S+4`) zero-initialises four consecutive vectors as three-word triples with the fourth word skipped — `+0x40/+0x50/+0x60/+0x70` raw, 0x10 apart, allocator-last — which enumerates the players triple as literally `{S+0x54, S+0x58, S+0x5c}` with no frame arithmetic at all, and puts the fleets vector at `S+0x64` exactly where B4 measured it. Five NPC accessors at 0x00788de0ff bounds-check an index against `([S+0x58] − [S+0x54]) >> 2` and then index `_Myfirst`, which is a third confirmation. **The vector is not the lobby's player list.** It is `#empires + one rebel-AI per distinct empire species + 4 NPC pseudo-players` (Alien Menace, Peacekeeper Enforcer, Von Neumann, Independent Colony — all species 4). `Sim.NumPlrs` reads **8** in the Human saves (two species) and **7** in every Zuul save (one species), against a `Summary.Players` array with **2** entries in both. Both numbers are right; they count different things. **And my draft of this document was wrong about my own data.** It said the hook read 8 "on both saves". It did not: the trace reads 8 on `ref-turn2` and **7** on `zuul-turn16-noderoute`, matching each save's `NumPlrs` exactly. I generalised from one run without re-reading the other, and it took a check aimed at something else to catch it. * **Which of the 12-to-44 `S+0x8` increments per turn come from where** (§5), and what they scale with. * The direct-call sweeps behind "node-line decay's only RNG site is the `Chance(0.5f)`", "its downstream pair draws nothing" and "`ProcessNodeSpaceTravel` draws nothing" are **worth less than they look**, and method rule 16 (landed by lane J while this run was in flight) says why: an inlined draw leaves no call-graph edge at all, so a call sweep is a lower bound. Rule 17 applies too — those sweeps clipped at Ghidra's reported function sizes. **The behavioural measurement is what carries these claims, not the sweeps.** `ProcessNodeSpaceTravel` moved the generator by 0 words on **16** observations (twice per turn, eight turns) and node-line decay by 0 on **8**. That evidence is immune to both rules, because it does not ask which function drew — it asks whether the generator moved. * **No Guard region is declared by any hook in this family, so nothing here can report an undeclared write.** That is deliberate — these hooks make no claim about game state at all, and a guard over the generator would only duplicate the Result region that already covers the whole object — but it means the usual harness-audit safety net is absent by design. Both traces show `err = 0`, `undeclared = 0` on 32 records each; the second number is vacuous and should be read that way. * **The one record with no ledger position is the first pre-turn autosave of each session**, which runs before any turn driver and therefore before the hooks know the server pointer. It declares no region at all rather than declaring one it cannot fill. Every record that *did* declare the region resolved: 0 `words: null` across 64 records. * **The ledger's block-chain machinery has never run live.** Every observation in both runs sat inside a single MT block — `left` walked 432 → 413 → 395 → 375 → 357 on `ref-turn2` and 263 → 243 → 223 → 201 → 181 on the Zuul save, never reaching 0. So every live word count reduces to `left_before − left_after`, and the twist-and-index path that makes the instrument correct across block boundaries is exercised **only by the host tests**. A turn that crosses a boundary (any turn spending more words than `left`) is the first real test of it. This is the thinnest part of the instrument and the one to watch. * Everything here is one game state per save, two saves, eight turns, with **158 words** of generator movement in total (192 → 267 and 361 → 443). It is a thin workload measured precisely, not a broad one. In particular the per-turn total moved only between 18 and 22 across eight turns: the *variation* is barely sampled, and nothing here says what makes it 18 rather than 22. ## 9. Node-line expiry — a distance, not an absence Lane O's `zuul-turn16-noderoute.sav` was pushed to the VM and played forward. Phase 11 draws one word per **expired** node line; rather than report "we ran N turns and it never fired", the hook was extended to classify the whole `NodePath` population at entry, using the same `RemainingLife` formula the original tests. The classification is what makes the negative result usable: | turn | node paths | permanent (`npt == 0`) | immortal (`npdtn == INT_MAX`) | **mortal** | min remaining life | ≤ 5 | expired → words | |---|---|---|---|---|---|---|---| | 17 | 53 | 51 | 0 | **2** | 40 | 0 | 0 | | 18 | 54 | 51 | 0 | **3** | 42 | 0 | 0 | | 19 | 56 | 51 | 0 | **5** | 41 | 0 | 0 | | 20 | 57 | 51 | 0 | **6** | 43 | 0 | 0 | Three things follow, none of which was knowable before: 1. **51 of the 53 node lines on this map can never expire** — `npt == 0` takes `RemainingLife`'s first early-out. The static map's node network is not a decay candidate at all. Only *dug* lines are, which is why this is a Zuul save: the mortal count rises by roughly one per turn as the Zuul dig. 2. **Every mortal line is ~40 turns from expiry**, and the population's minimum stays in a 40–43 band while new lines are added at full life. So the first phase-11 draw on this save is **tens of turns away**, not one or two — and it is reachable, which "we saw nothing" would not have told anyone. 3. It explains why the campaign never noticed: no save in the corpus is within 40 turns of a decay event, and the ones that could get there are the newest saves in it. ### 9.1 The prediction, and the turn it came true Because `min_life` was falling by exactly 1 per turn — 43, 42, 41 … 30 at turn 34, with the traffic term contributing nothing on this map — a numeric prediction became possible, and it was committed to `sots-engine/docs/Z-tail-rng.md` §6 at turn 34 with the run still in flight: > **P9. The first phase-11 draw happens on turn 64, and costs exactly 1 word.** Node-line decay records > `np_min_life = 0`, `predict_words = 1`, and a measured `rng` delta of 1; the tail's total becomes 1 > instead of 0; the bracket total becomes `ProcessTurn + 1`. The game was played to turn 64. **Every clause held.** | turn | node paths | mortal | min life | ≤5 | expired | `predict_words` | node-decay words | **tail words** | `ProcessTurn` | bracket | residual | |---|---|---|---|---|---|---|---|---|---|---|---| | 62 | 64 | 13 | 2 | 1 | 0 | 0 | 0 | 0 | 18 | 18 | 0 | | 63 | 64 | 13 | 1 | 1 | 0 | 0 | 0 | 0 | 18 | 18 | 0 | | **64** | 64 | 13 | — | 0 | **1** | **1** | **1** | **1** | 20 | **21** | **0** | **That is the first non-zero tail cost this campaign has ever recorded**, and it is exactly the draw lane K found by reading 0x007ae095. The defect lane K warned about is no longer latent, no longer inferred and no longer a hypothesis: **on turn 64 of this save, a reimplementation that models `ProcessTurn` perfectly and stops would have written an autosave one generator word out of step, and every subsequent turn would diverge.** `predict_words` is computed at hook entry, *before* the original runs, from the same `RemainingLife` predicate transcribed in §6.1. It said 1; the measurement said 1. That is a real check of the model — as opposed to the 63 preceding turns, where it said 0 and the measurement said 0, which checked nothing and was reported that way. ### 9.2 The twist path ran, live, on the same turn The instrument's thinnest part (§8: "the block-chain machinery has never run live") was exercised on this very turn. `ProcessTurn` entered with `left = 11` and left with `left = 615` — it **crossed a block boundary**, the generator twisted, and the ledger reported `11 + (624 − 615) = 20` words. Sixty-three turns of measurements had all sat inside a single block, so every earlier word count reduced to a subtraction; this one did not, and the bracket still reconciled to a residual of 0. ### 9.3 What is still not settled about node lines * **One expiry, on one map.** 51 of the 64 lines are permanent; the 13 mortal ones are Zuul-dug. A non-Zuul game may never produce a mortal line at all. * **The `0x20000`-fleet gate has never been exercised**, because it only matters when the roll *succeeds* and no fleet was riding this line. Whether the roll succeeded here is not visible in a word count — the draw costs 1 either way, which is the whole point of §6's correction. * **Two expiries on one turn has never been observed** (`np_within5` read 1, never 2), so "one word per expired line" is confirmed for *one* line and extrapolated for two. --- ## 10. A real battle, measured — and it costs nothing The turn-54 End Turn of the long run stopped on an **Encounter at Gallandro**: the player's five ships (3 DE Colonizer, 2 DE Armor) against a **Von Neumann**. That is the workload §8 said did not exist and lane J's `combat-resolver.md` asked for — every encounter in 54 turns until this one had `res->+0x4` set, making `ApplyEncounterResult` a whole-function no-op. **Auto Resolve** was chosen (the dialog's four options are Fight Manually / Auto Resolve / Fight Manually If Opponent Does / Retreat), and the prediction was committed to `sots-engine/docs/Z-tail-rng.md` §7 with the dialog still on screen and unclicked. | turn | `res_no_battle` | `ApplyEncounterResult` words | tail words | `ProcessTurn` words | bracket | residual | |---|---|---|---|---|---|---| | 52 | 1 | 0 | 0 | 18 | 18 | 0 | | 53 | 1 | 0 | 0 | 18 | 18 | 0 | | 54 | 1 | 0 | 0 | 16 | 16 | 0 | | **55** | **0** | **0** | **0** | 22 | **22** | **0** | **P10 predicted a non-zero tail cost and was wrong.** The first battle this campaign has ever instrumented moved the strategic generator by **zero words**, and the bracket residual stayed 0 — so combat proper (`RunCombatRound` / the combat server, which run between `ProcessTurn` and the tail and are hooked by nobody) drew nothing either. Every one of the turn's 22 words was inside `StrategyServer::ProcessTurn`, just as on a peaceful turn. That is the *strong* form of lane J's reading. Lane J established from the instruction stream that the resolver has **no unconditional draw** — its three sites are a node-cannon `NextInt`, an inlined `NextFloat` per back-engineering candidate, and a `NextInt` per successful roll of that. This run shows that on an ordinary encounter **none of the three fires**, and lane J's own cheap prediction — *a plain fleet battle should cost the same as a peaceful turn* — holds exactly. ### 10.1 Why this matters to the standalone A reimplementation that models a strategic turn's RNG and **nothing about combat** reproduces the generator correctly through a battle. Combat's effect on the save is entirely in the state it writes, not in the generator it advances. That is a much cheaper milestone than "read the 7,641-byte resolver first", and it was not knowable before this run: the honest prior was lane K's "draw counts are entirely combat-dependent and unknown". ### 10.2 What one battle does not settle — and it is a lot * **One encounter, auto-resolved.** `Auto Resolve` may not take the same path as a manually fought battle; the tactical engine has its own `Mars::CombatSim` generator at `sim+0x108` (§7) which nothing here watches. A manually fought battle is a different experiment and has still never been run. * **The opponent was a Von Neumann**, an NPC pseudo-player, not a rival empire's war fleet. No node cannon was present, so R1 could not fire; whether R2's salvage roll was skipped because no candidate had a non-zero salvage slot, or because the arm was not reached at all, is not distinguishable from a word count of 0. * **A cost of 0 is the easiest number to produce by accident.** It is exactly what a hook that compared nothing would report. The reasons to believe it here are that the same hook reported 18–22 for `ProcessTurn` on the same turn, that `res_no_battle` flipped to 0 for the first time in 55 turns on exactly the turn the battle happened, and that the player's fleet was destroyed — the battle demonstrably occurred. It is still one observation. * **No `EVENT_*` or state-side check was made.** These hooks declare the generator and nothing else, so this says the battle was RNG-free and says nothing about whether it was *computed* correctly. --- ## 11. The per-call-site ledger — every word of a turn, attributed §2 said *where* a turn's words are spent (all inside `ProcessTurn`); this says *which call site* spends them. The seven generator entry points are detoured and each call records `__builtin_return_address(0)` — the game instruction after its own `call` — with the word cost taken from `left` before and after (`sots-engine/src/shim/hooks/draw_sites.{h,cpp}`; report tool `tools/rng_site_report.py`). This is attribution, not discovery: lane I closed the search space at seven entry points and 22 sites in `ProcessTurn`'s closure. Three consecutive End Turns on `ref-turn2`, build `z-sites2-20260908T1432Z`: | call site | owner | entry point | calls/turn | words/turn | |---|---|---|---|---| | 0x0050329d | `FUN_00503200`+0x9d ← `DetectEncounters` (lane I, depth 4) | `NextFloat` | 1 | 1 | | 0x007929a4 | `FUN_00792750`+0x254 ← `DetectEncounters` (lane I, depth 3) | `NextInt` | 1 | 1 | | 0x00587888 | `TechTree::ProcessResearch`+0x1c8 | `NextFloat` | 0–1 | 0–1 | | 0x0088df4f | `ServerPlayer::RollResearchEvent`+0x2f (lane T) | `NextFloat` | 0–1 | 0–1 | | **0x00893426** | **`FUN_00893290`+0x196** | **`Chance`** | **8** | **8** | | **0x00893513** | **`FUN_00893290`+0x283** | **`Chance`** | **8** | **8** | | turn | site sum | `ProcessTurn`, measured independently | residual | |---|---|---|---| | 3 | **19** | 19 | **0** | | 4 | **18** | 18 | **0** | | 5 | **20** | 20 | **0** | **Nothing is unattributed, on any of the three turns.** The two instruments share no code path — one reads `left` around a boundary and reconstructs an absolute position, the other reads `left` around a single call and keys on a return address — and they agree word for word. The 18–20 spread that §2 could only report is now *explained*: it is the two optional research draws, both of which are gated. ### 11.1 The dominant consumer of a turn is not in the static inventory **`FUN_00893290` spends 16 of every turn's 18–20 words** — two `Chance` calls per player across all eight entries of the server's player vector — and it is **not one of lane I's 22 sites**. Lane I stated plainly that its closure covers **direct** call edges only and that indirect-call reachability was unsettled. This is that gap, measured: the single largest RNG consumer in a strategic turn is invisible to a direct-call sweep from `StrategyServer::ProcessTurn`. That is not a criticism of lane I's inventory — its recall claim is about the *tempering-immediate scan*, which is complete, and its 22-site list is explicitly a direct-edge closure. It is the demonstration that the caveat mattered. **`FUN_00893290` is unidentified as of this writing** and is the highest-value target left: it decides something twice per player per turn, on a coin the game bothers to flip. ### 11.2 Two bookkeeping corrections the raw numbers need The shim's raw totals are 35 / 34 / 36, not 19 / 18 / 20, and both differences are accounting rather than measurement — `tools/rng_site_report.py` applies them and shows its working: * **Helper-internal rows double-count.** `Chance` calls `NextFloat` internally, so its 16 words appear twice: once on the `Chance` rows and once on a row whose return address (0x008e6e04) is *inside* `Chance`'s own body. The report subtracts any row landing inside another entry point's body. * **Other generators are not this generator.** 8 calls per turn come from `FUN_00578cf0`, `FUN_005798e0` and `FUN_0069dbb0` drawing on a **different `Mars::RNG` instance** — the `StrategyClient`'s at `client+0x134` (§7). They are real draws and they are correctly excluded: they never touch the strategic generator the save serialises. The first version of this instrument did not distinguish them and reported 44 words against a bracket of 18, which is what caught it. The second point is worth keeping: **a per-site RNG ledger that does not identify which generator each draw came from is not a ledger.** The boundary instrument was immune to this by construction because it watches one object; the site instrument had to be told. ### 11.3 What the site ledger did not see * **`EncounterDetect_AssignContacts` never ran** on these three turns — its gate in `EncounterDetect_ProcessTeamRecord` (some team-record member must have `+0xfc != 0`) was not satisfied. Its hook recorded no call, so lane I's one inlined site in `ProcessTurn`'s closure contributed **0**, which is consistent with the sums reconciling exactly. **The inlined-draw path is therefore still unexercised**, and if it fires on some other save the site sum will fall short of the bracket by exactly its cost — which is how it will announce itself. * Three turns of one save. The two `Chance` sites fired 8/8 every turn with no variation, so nothing here says what makes them fire *fewer* times, and `FUN_00893290`'s own gating is unmeasured.