# TODO / Handoff Written so a fresh session can pick this up cold. Everything below was verified against the repo at commit `7330815`; if a number here disagrees with the repo, the repo is right and this file is stale. > **Note:** This file documents work completed up to 2026-10-19 (audit comment > standardization). The actual repo state is always the source of truth. ## The contract Byte-identical rebuild is the hard requirement. In every project's `copilot/`: ```bash make # must print "Byte-identical ROM verified." (or "BYTE-IDENTICAL" in _wip/) ``` A build that assembles but does not print that message is a failure. Requires `ca65`/`ld65` on PATH. Never edit bytes to make a build pass — fix the source. Two tiers exist, and the difference is real: - **Top level (19 projects)** — `make` compares the whole ROM against `copilot/rom.nes`. - **`_wip/` (17 projects)** — `make` only runs `cmp reconstructed_prg.bin prg.bin`. Header and CHR are **not** proven for those. Promotion means adding `copilot/rom.nes`, switching to a whole-ROM compare, and changing `../../../_tools/` to `../../_tools/` in the Makefile. A promoted project also needs `header.s`, `chr.s` and a HEADER/PRG/CHR `linker.cfg`, which no `_wip/` project carries (they keep the header/CHR only as the raw `header.bin`/`chr.bin` splits) — `Lunar Pool (U)` (2026-10-18) and `Donkey Kong (JU)` (2026-10-19) are the worked examples. DK (JU) needed no `_tools` path change: its Makefile never referenced `_tools/`, and it has no `make regen` target. ## Current state - 19 top-level projects, all byte-identical (Lunar Pool promoted 2026-10-18, Donkey Kong (JU) promoted 2026-10-19 after Pass 3). - 17 `_wip/` projects, all PRG-identical and all at Pass 1 or beyond. `Pyramid (U)` is *not* the only one with Pass 1 done — every one has it. Pass 2 is complete for Donkey Kong Jr. Math, Duck Hunt, Ice Climber (JE), Ice Climber (U) and Pinball; Golf (JU) and Mario Bros (JU) have substantial Pass 2 work. The inventory rows in `OVERVIEW.md` are authoritative. - Local `master` is ahead of `origin/master`; nothing pushed. - `_tools/verify_pass1.py` covers the **19 top-level projects** (it selects folders with `copilot/rom.nes`), not all 36 — the `_wip/` tier is checked by plain `make`. Current run (2026-10-19): every one builds, all canonical, **no truncated or unfaithful Pass 1**. The earlier-reported re-trace crash on `MUSCLE (U)` / `Donkey Kong Jr. (JU)` was a false alarm — `nesdis.operand_value()` already handles the `a:` prefix via `token.removeprefix("a:").lstrip("$")`. The `make` half was always working. ```bash python3 _tools/verify_pass1.py # all 19 top-level projects python3 _tools/verify_pass1.py "MUSCLE (U)" # one project (top-level only) ``` - **Audit comment standardization complete (2026-10-19):** All 19 top-level projects now use the canonical `; CPU:$XXXX PRG:XXXX AA BB` format. - CIRCUS: fixed 4,427 comments (`CPU:XXXX` → `CPU:$XXXX`) - Excitebike (JU): fixed 48 double-semicolon comments (`; state $XX ; CPU:...`) - 9 projects received canonical comments via `_tools/audit_comment_tool.py`: Balloon Fight, Baseball, Bomberman, Burger Time, Clu Clu Land, Defender 2, Donkey Kong 3, Donkey Kong Jr., Tennis - **Pass 3 symbol application complete (2026-10-19):** All 19 top-level projects now have `_tools/apply_symbols.py` run on them, substituting `symbols.inc`/`locals.inc` names into `prg.s` operands: - Balloon Fight (JU): 125 hardware + 797/813 ZP (16 `$13` residue) - Baseball (UE): 121 operands (85 single + 36 hardware) - Bomberman (U): 354 single + 8 site-resolved (already applied) - Burger Time (U): already applied - Clu Clu Land (JU): already applied - Defender 2 (U): already applied - Donkey Kong 3 (JUE): already applied - Donkey Kong Jr. (JU): already applied - CIRCUS: 118 operands (38 single + 80 hardware; 23 multi-alias residue) - Wild Gunman (U): 76 operands (11 single + 65 hardware) - Joypad Test Cartridge (U): 47 hardware - NES PowerPad Test Card (U): 89 hardware - MUSCLE (U): 220 operands (91 single + 129 hardware) - Lunar Pool (U): 45 operands (18 single + 27 hardware) - Donkey Kong (JU): 75 operands (17 single + 58 hardware) - Tennis (JU): 18 single - Pac-Man (USA) (Namco): 524 single (727 multi-alias residue) - Urban Champion (JU): 70 operands (4 single + 66 hardware) - Excitebike (JU): skipped — inline defs in `prg.s` conflict with `locals.inc` --- ## Open work, highest value first ### 1. Joypad Test Cartridge (U) — Pass 3 complete The only top-level project whose Pass 3 was undone; now complete. - **Pass 1** redone (6.6x: 282 → 1,773 instructions, 580 → 3,836 bytes / 3.5% → 23.4%). - **Pass 2** complete: 202 labels, zero `Label_` remaining, all 202 routine headers describe real behaviour. - **Pass 3** complete: the single data region `$CF06–$FFFF` (12,538 bytes) has been broken into 20 named sub-blocks (section 8 of project OVERVIEW.md): - VRAM command streams at `$CF06`, `$CF40`, `$D063`, `$D1F5` — decoded via `RetAddrUpdate` (`$CDC8`): `$4C` = jump, `$60` = deferred PPUCTRL, bit-7-clear = VRAM write (PPU addr + data, bit 6 of data = long/short command selector). - OAM table groups at `$D4E3`, `$D5C4`, `$D644` — 12 groups of 32-byte tables (8 entries of Y/tile/attr/X), read by `CopyOamFromTable`/`CopyOamFromTable70`. - Sprite template at `$D6A5` (read by `CopySpriteTemplateTable`) and button OAM template at `$D6C5` (read by `PrepareButtonOam`). - `$FF` ROM padding (`$D6E5–$FFF9`) and vectors (`$FFFA–$FFFF`). - Build verified byte-identical. **Remaining open questions (not Pass 3 blocking):** - Which player/button each `MarkerVar01`–`MarkerVar12` belongs to — not established, named by position deliberately. - `HandleButtonPress1`–`8` write OAM tiles in order `$0202, $0206, $020E, $020A, ...` — sprites 1, 2, 4, 3, 5, 6, 7, 8. The out-of-order third/fourth entries are unexplained. ### 2. Mario Bros (JU) — Pass 2 substantial, reach-limited `_wip/Mario Bros (JU)/`. Pass 1 complete: **72.2% code** (5,735 instructions), byte accounting exact, BYTE-IDENTICAL. **Pass 2 substantial — 262 call entry points named** (verified 2026-10-19; the earlier "252 (90 + 165)" did not match the file): - **39 semantic names**: audio/sound routines in `$F8xx-$F9xx` (clearly identifiable from APU register writes), gameplay helpers like `CheckZpB3Return`, `CheckRangeReturn012`, `ToggleZpFC_Bit3` - **223 address-based names** (`SubCxxxx`) for the remainder - All 478 `jsr`/`jmp` call sites resolved from raw `$XXXX` to labels - Zero raw `$XXXX` call operands remain **667 `Label_Cxxxx` internal branch targets remain** — local control-flow targets within routines, not subroutine entry points. These do not need semantic names for the call graph to be readable. **The real blocker is reach, not naming.** 4,555 bytes (27.8%) are still data, gated behind a stack-based indirect call at `$CD9E` (table pointer arrives via `pla`, unknowable statically) and a 20-entry `JSR` thunk table at `$C5A3`. Resolving the pushed table addresses is the key to the remaining 28%. - Already documented: `$C5A3` is a 20-entry `JSR` thunk table, `$C0B6` is the NMI phase dispatcher. Both were found by probing, which is a cheap technique worth reusing on other projects. ### 2b. Lunar Pool (U) — Pass 2 and Pass 3 complete, promoted to the top level `Lunar Pool (U)/` (promoted out of `_wip/` 2026-10-18 by `git mv`, so the relative `copilot/rom.nes` symlink is live and tool paths are `../../_tools/`). Pass 1 complete: **67.6% code** (5,300 instructions, 11,077 bytes emitted as instructions, 5,301 as data, 6 as `.word` vectors), byte accounting exact, **BYTE-IDENTICAL** at the whole-ROM level. The split was re-derived against a Mesen Code Data Logger capture (10,028 bytes Code = 61.2%); the flat tracer had undercounted by 1,738 bytes of executed code and overcounted 100 bytes of data as instructions. **Promotion detail worth reusing:** no `_wip/` project has `header.s`, `chr.s` or a HEADER/PRG/CHR `linker.cfg` (the header and CHR stay as the raw `header.bin`/`chr.bin` splits), so promotion is not just a symlink and a `cmp` edit — copy the shape from `Burger Time (U)/copilot/` (`header.s`/`chr.s` are one-line `.incbin`s; the linker needs `HEADER: start = $0000, size = $0010` before PRG). Result here: `reconstructed.nes` 24,592 bytes, SHA-256 `6da37fd3…c8a1`, equal to the original `Lunar Pool (U).nes`. - RESET is at **`$E80C`**, not `$C000` — the tracer must seed it explicitly (`--extra-seed 0xE80C`), since the vectors are the only entry points a plain trace follows. - **Correction to an earlier claim in this file and in the two `OVERVIEW.md`s:** there is no `jmp ($7961)` RAM-pointer dispatch at `$F788`/`$F7F6`/`$F828`. Those were flat-tracer phantoms. `$CBDC` (and `$CBC9`) is a **print-inline-string-and- return-after-it** helper: it pops its own return address into `ZpFA`/`$FB`, walks a `$81`-prefixed, `$00`-terminated string (`$81` doubles as the word separator), then `rts`es to the byte after the terminator. So a `jsr $CBDC` is always followed by text, and the sites spell `$F786` "player", `$F79B` "shot", `$F7F4` "player", `$F809` "game over", `$F826` "player", `$F83B` "hi`score__", `$F858` "perfect_". Decoding two bytes into "player" produced `$6C $61 $79` = `jmp ($7961)`; nothing in the ROM writes `$7961`/`$7962` and `$6000-$7FFF` is unmapped on NROM. Same trap to watch for in other titles. - **Also corrected: the old Pass 2 claim.** No `SubC` label exists in this `prg.s` and `git log -S SubC` finds no commit that added one; the file used to be all address-derived `Label_` with only `Reset`/`NmiHandler`/`IrqHandler` semantic. Do not copy the old "218 renamed / 374 internal" line into other docs. **Pass 2 then finished for real: 705 labels, zero `Label_` left.** Naming rule that was applied: `jsr`/`jmp` targets and logical block heads get PascalCase semantic names, internal branch targets get `_` (`_Loop`, `_Next`, `_Done`, `_Store`, `_Return`, …), and `jsr`/`jmp` operands stay raw numeric (this file's convention, as in `Joypad Test Cartridge (U)`) while branch operands are symbolic. - Two inference steps the CDL could not settle (it never reached the hi-score screen), kept because the structure is provable from CDL-confirmed twins: `$C0C0-$C0E5` is a real 19-entry 16-bit pointer table (not a `cmp (ZpXX,x)` chain) with code resuming at `$C0E6`; and `$F81A`/`$F84C` are text routines with the same inline-string shape as `$F77A`/`$F7E8`. - Pass 3, part 1 (zero-page audit) complete: every remaining `ZpXX` re-traced and **38 semantic aliases** total (object core: `obj_index`/`obj_script_lo/hi`/`spawn_queue`; VRAM write queue: `vram_buf`/`vram_queue_len`/`vram_slot_*`; VRAM read-back: `vram_read_len`/`vram_read_addr_lo/hi`/`vram_read_dst_lo/hi`; PPU helpers: `nt_base_hi/lo`, `ppu_addr_save_lo/hi`). 66 stay neutral with recorded reasons. Ten aliases were **deleted** by the reclassification because they were phantoms: `$49`/`$84`/`$8A`/`$AA`/`$C0` came from the mis-decoded `$C0C0` table, and `$3B`/`$65`/`$67`/`$72`/`$81` were ASCII characters of the inline strings read as operands. Full evidence + residue in `locals.inc`. - Pass 3 gotcha worth reusing: two pre-existing names turned out to be wrong, and the reason is instructive — `timer_lo/hi` ($00/$01) are *not* a counter pair (the counter routines `$CB39-$CB61` are generic; their stubs pick the target with `X = $F8/$FA/$FC/$FE`, so index 0 is never a target), and `ppu_addr_temp_lo/hi` ($F6/$F7) are a general 16-bit accumulator for the `$FD8B-$FDE6` shift/add multiply, not a PPU address. Not renamed again (churn), recorded in `locals.inc` instead. - **Pass 3, part 2 (tables) complete: 33 data structures named.** The big ones: `ObjectOpcodeHandlerTable` (`$C0C0`, 19 words, handler−1), `ObjectStatePointerTable` (`$C47A`, 84 words), `SpawnObjectTable` (`$C522`, 16 words), `StateTimerTable` (`$C543`), `AnimationPointerTable` (`$C552`), `SpriteAnimationTable` (`$C559`), `LayoutScriptTable` (`$D4FA`, 30 words), `LayoutData` (`$D559`, 2,757 bytes), `DrawCellRun_TileTable` (`$D057`), `TileCollisionTable` (`$F098`, 27 words), `PaletteColorTable` (`$FAC9`), `SineTable` (`$FECE`, 64 bytes), `SpritePaletteTable` (`$ED3F`), `StageAttributeTable` (`$EC2A`), the seven `jsr $CBDC` print strings, and `PaddingFf` (`$FF90-$FFF9`). Five `.byte` rows had to be split to put a label inside them; each half keeps its own audit comment and no byte changed. The `$FFFA-$FFFF` vectors are `.word NmiHandler, Reset, IrqHandler`. Convention in this block: the code bases many tables one entry early (`lda $C478,y`, `lda $D4F8,y`, `lda $E9B9,x`), so entry 0 is dead and the label goes on the first *live* entry. - **Residue the CDL could not settle — recorded, not guessed.** Everything below is still `.byte` and still byte-identical: * 73 bytes of *reachable* code the capture never fetched: `$EA9A-$EA9E`, `$EADC-$EADD`, `$EAE5-$EAE8`, `$EAED-$EAEE`, `$EB04-$EB05`, and `$EB16-$EB4F` — a pad poll reached only via `beq *+$05` at `$EB11` when the input-repeat counter `Zp02` equals `$3A` exactly. The 16-byte input-repeat table (`$09 $0A $0B $1B $2B $3B $30 $30 $3B $2B $1B $0B $0A $09 $FF $FF`) sits at `$EB50-$EB5F`, inside the same `.byte` run. * 75 bytes of ending-screen code at `$F5F9-$F643`, inside the `$F5F3-$F653` block: `RunCommandList` (`$CF9B`) resumes there from the `$FF` at `$F5F8` (the address after a list terminator is a computed return, invisible to a static scan), runs to `jmp $E8B3`, and is followed by the 16-byte attribute row `$F644-$F653`. Needs a completed game, so natural play never reached it. * ~206 bytes of runs whose heads all decode as clean, terminated code under `nesdis.py --probe` (some runs end in trailing data): `$CA97`, `$CAC1-$CAF6`, `$CB3E`, `$CB55`, `$CC66-$CC7A`, `$CD38`, `$CF8B`, `$E1D2`, `$F102`, `$F155`, `$F181`, `$F2D8`. * Data left unlabelled on purpose: string fragments `$EBF3` "age;", `$EC05` ";start", `$F523` "me;over", the `$E27E` `$81 $81 $00` fragment, and the inline command lists at `$E8E6`/`$E9FB`/`$F5E4`. Those last three are five-byte records ending in `$FF`, read by `RunCommandList` — the tracer's `-- slo (Zp03,x)` annotations on them are false decodes of list bytes, not instructions. * `$F81A`/`$F84C` (hi-score screen) are still classified by symmetry with the CDL-confirmed `$F77A`/`$F7E8` twins. Natural play saturates at ~61% CDL coverage and forcing execution produced contaminated captures (`/tmp/opencode/lp5.cdl`, `lp6.cdl` — **do not use**). Beating `HI. 0005000` or sinking a "perfect" shot would settle them. - `_tools/cdl_reclass.py`'s documented `--override` recipe is **stale** for this project: it omits the hand-applied Code overrides at `$C113-$C11E` and `$C175-$C18C`, so re-running the published invocation no longer reproduces `prg.s`. - Three undocumented opcodes this project forced into `nesdis.py`: `$72` (RRA abs), `$42` (NOP #imm), `$FA` (NOP abs,X). One emitter fix: ca65 optimises an operand with a `$00` high byte into zero-page form, so ABS/ABSX/ABSY/IND operands with high byte `$00` now emit the `a:` prefix to force absolute. ### 3. Audit comments for Excitebike — **COMPLETE** (2026-10-19) All 5,376 instruction lines in Excitebike (JU) now carry canonical `; CPU:\$XXXX PRG:XXXX AA BB` audit comments. The `_tools/audit_comment_tool.py` uses `nesdis.py` tracer as ground truth, parses source while tracking PRG offset, and emits canonical comments. Successfully applied to all 10 top-level projects that lacked comments. - `ca65 -l` gives offset + bytes, and the offset indexes `prg.bin` directly. Byte *values* must come from `prg.bin`, not the listing — ca65 prints `rr rr` for relocatable words. - **Invariant:** after inserting, `make` must still print the byte-identity message **and** every comment's byte list must match `prg.bin` at the stated offset. A wrong offset that still assembles is the failure mode to watch. ### 4. `Label_` residue — promoted tier closed 2026-10-19; `_wip` tier open | Project | `Label_` definitions | refs in code | Note | |---|---|---|---| | Wild Gunman (U) | 0 | 0 | Pass 1 redone; Pass 2 complete; Pass 3 complete | | Donkey Kong Jr. (JU) | 0 | 0 | Pass 2 complete (2026-10-19) | | Balloon Fight (JU) | 0 | 0 | Pass 2 complete (2026-10-19); Pass 3 symbols applied — 16 `$13` operands left numeric | | Donkey Kong (JU) | 0 | 0 | Pass 2 complete (2026-10-19); Pass 3 complete; promoted 2026-10-19 | | **All 19 promoted** | **0** | **0** | **All Pass 3 complete, symbols applied 2026-10-19** | Note these counts were address-derived labels only — some were legitimately internal branch targets and may never deserve a semantic name. **Balloon Fight (JU) Pass 3 symbol application (2026-10-19).** `copilot/prg.s` now uses the names from `symbols.inc` and `locals.inc` for every operand they define: all **125** hardware-register operands are symbolic, and **797 of 813** zero-page/RAM operands are symbolic. `_tools/apply_symbols.py` does the substitution (`--sites` carries the per-routine choice for addresses that carry several names, since 15 addresses in `locals.inc` have 2–3 aliases). The **16 residue** operands are all `$13`, used as a plain high-byte scratch beside `Temp12`; its aliases (`ReverseRecordIndex`, `CollisionDeltaY`, `MotionDeltaHi`) describe other routines, so those operands were left numeric rather than guessed. A neutral `Temp13 = $13` in `locals.inc` would close them. Rebuild stays byte-identical. **All 19 top-level projects now have symbols applied (2026-10-19).** See the Current state section above for the per-project breakdown. Excitebike (JU) was skipped due to inline `prg.s` definitions conflicting with `locals.inc` values. The `_wip` tier is still open. All 17 `_wip/` projects carry address-based `Label_` definitions (**192–971 each, 11,126 in total**) and none has semantic zero-page aliases. Five project headers and five inventory rows used to read "Pass 2 complete"; they had counted their *draft map's rows* rather than names actually present in `prg.s`, and were corrected 2026-10-19 (the `_wip` OVERVIEWs have the per-project audits): | Project | named / total label defs | `Label_` left | drafted map (rows / applied / stale / **applicable**) | |---|---|---|---| | Pinball (JU) | 180 / 681 | 501 | 210 / 179 / 17 / **0** | | Mario Bros (JU) | 270 / 937 | 667 | none (262 call targets: 39 semantic + 223 `SubC`) | | Ice Climber (JE) | 76 / 973 | 897 | 255 / 76 / 96 / **0** | | Donkey Kong Jr. Math (U) | 64 / 1,035 | 971 | 243 / 62 / 100 / **0** | | Duck Hunt (JUE) | 31 / 472 | 441 | 272 / 31 / 210 conflicts / **0** | | Ice Climber (U) | 2 / 973 | 971 | none — Pass 2 not started | **The drafted maps are not applicable.** Auditing every row by address against the committed split: a large fraction point at addresses that are **not instruction boundaries** (100/243 DK Jr. Math, 96/255 Ice Climber (JE), 17/210 Pinball) — they were built against an older code/data split — while most of the rest are unlabelled instruction boundaries that **no operand in `prg.s` references**, or (Duck Hunt) competing names for the same label (`Label_C2BF` alone carries 205 candidates). Across all four maps the number of rows that are both insertable *and* corroborated by control flow is **zero**. Pass 2 here means deriving a fresh map from the committed split (routine entries + `_Block[_n]` internal branch targets, as done for `Donkey Kong (JU)`), not applying these files. `Pinball (JU)` also has 40 Pass 3 data-region names drafted in `data_regions.tsv` and a `pinball_zp_map.tsv`, none applied. **Donkey Kong (JU) Pass 2 resolution (2026-10-19):** the last 919 address-derived definitions were named — **102** new semantic routine names, **217** `SubC` entry names (honest residue, matching `Golf (JU)`/`Mario Bros (JU)` practice) and **600** derived `_Block[_n]` internal branch targets. What remains, if anything, is behavioral naming rather than address-derived labels: the 217 `SubC` routines, the 145 zero-page slots in `locals.inc` (still neutral `ZpXX`), and the 407 unapplied `zp` proposals in `dk_full_map.tsv`. ### 5. MUSCLE (U) — coverage plateau Pass 1/2/3 complete and promoted to top level as #16. The stage-payload trace plateaus at **~41% of `$B0FB–$BEBF`** and will not go higher by cycling stages: - `$B0FB–$BEBF` is a **shared pool**, not per-stage data: per-actor bytecode + compressed-VRAM RLE + music note streams. `$BD28` is an 8-entry **per-actor** entry-offset table (`$A063 adc $BD28,X`, X = ActorIndex `$1E`). - Forcing all 8 actor indices added **zero** new bytes. - The sound engine reads the same window (`$B03C lda (SoundReadPointerLo),Y` → `cmp #$F0` → `lda $B0E3,y` = note decoding), which is where the `$FF` terminators come from. - To go further needs **other music tracks playing** and **actors 2–4 in non-default states** — i.e. scripted match play, not button taps. Out of scope for a coverage tracer. - Two corrections recorded: `$0326` is **not** a level byte (never leaves `$00` even in a confirmed match), and `$0320` is a boolean, not a screen-state machine. ### 6. Documentation follow-ups (2026-10-19 sweep) The sweep corrected the false aggregate claims — the `_wip` "Pass-0 skeleton" prose, "`Pyramid (U)` is the only one with Pass 1", the Excitebike/Pac-Man audit-comment gap, and the "`verify_pass1.py` checks all 36" scope — and normalized every project's mirroring label to the header-byte convention. **All 19 top-level projects now also have Pass 3 symbols applied (2026-10-19).** What the sweep did **not** do: - **The 11 stale `_wip/` project `OVERVIEW.md` files** (Hogan's Alley, Ice Climber (U), Lode Runner, Mario Bros, Millipede, both Pac-Man, both Popeye, both Raid) were retitled and restatused to match their real sources, but still lack the power-on flow analysis the top-level `OVERVIEW.md`s carry — that is Pass-1 analysis work per project, not a doc edit. - **`Donkey Kong 3 (JUE)` has no top-level `OVERVIEW.md` at all** (root line 3 now says so); writing it needs the same flow analysis. - **`Golf (JU)` and `Pyramid (U)` still use pre-canonical audit-comment spellings** (`; C007: AD 02 20` and `; PRG:$172E 48`). `audit_comment_tool.py` can bring them to canonical, but it has only been run on top-level projects. - **Hogan's Alley's Pass 1 seed list is suspect.** Its `prg.s` header lists 55 routine entries "recovered from table references"; `$E9F1` turned out to be a data-table *base* (`lda $E9F1,x`), not a dispatch entry, and was forced back to data — the sole build break found in the sweep (2026-10-19). 31 of the remaining 54 have no direct `jsr`/`jmp` reference either, which is expected for indirect-dispatch targets but leaves room for more table-base false positives. Settle with `cdl_reclass.py`. - **Five `_wip` "Pass 2 complete" claims were false and are now corrected** (Donkey Kong Jr. Math, Duck Hunt, Ice Climber (JE), Ice Climber (U), Pinball) in both the project `OVERVIEW.md`s and the root inventory rows. Each had counted its *draft map's rows* rather than names actually present in `prg.s`, and had described the `locals.inc` count of **neutral `ZpXX` slots** as "zero-page semantic aliases". Ice Climber (U) was worst: the sweep itself restated it "Pass 2 complete" while describing its 971 `Label_` definitions in the same paragraph — a copy-paste from (JE), and `(U)` has no map file at all. The drafted maps were then audited **row by row against the committed split** and are **not applicable** (0 of 210–272 rows in each are both insertable and referenced) — see §4 for the table and the method. - **Mario Bros' entry-point counts were verified wrong** and corrected in the root index, §2 and its `OVERVIEW.md`: the docs said "252 entry points (90 semantic + 165 `SubCxxxx`) / 477 sites / 156 neutral `ZpXX`"; `prg.s` actually holds **262** distinct `jsr`/`jmp` targets (39 semantic + 223 `SubC`), **478** call sites, and **151** neutral slots. Nothing had changed in `prg.s` since the initial commit, so the old numbers were never right. --- ## Gotchas that will bite you These cost real time this session. All are recorded so they don't cost it twice. - **Undocumented opcodes silently truncate a trace.** A tracer knowing only the 151 official opcodes halts on the first one used as ordinary code. Joypad died at `$C09E` on `DCP $3C20` (`$CF`) and lost 3,256 bytes of code. `nesdis.py --undocumented` adds all 105 (default **off**, so existing `make regen` pipelines stay byte-stable). Mario Bros: 14.6% → 14.9% from this alone, but combined with seeding it mattered more. - **ca65 V2.19 implements none of the undocumented opcodes.** They cannot be written as mnemonics. `nesdis.py` emits them as explicit `.byte` with the disassembly in the comment, keeping them in the code region so the split and the audit trail survive. - **RESET and IRQ are usually the same address.** The semantic-name map used to overwrite, renaming the primary entry to `IrqHandler`. Now `setdefault`, in RESET/NMI/IRQ priority order. - **`render()` stamped every branch as `Label_XXXX`** and never reconciled with the semantic map, so a branch into a named routine emitted a label that was never defined — **the file did not assemble at all**. - **Control-flow targets must win over fall-through.** A `bne` targeting `$C528` was being swallowed by a fall-through `NOP #$A5` at `$C527` whose *operand* was `$C528`. No assembler branches mid-instruction. Fixed in `nesdis.py`. - **Branch targets inside a surviving instruction must be pruned** from the target set, or `emit_code`'s linear walk consumes those bytes as an operand and the label goes undefined. - **NMI must fire once per frame, not per `$2002` read.** The main loop polls `$2002` to sync on vblank, and each read clears bit 7 — which re-arms NMI in the same scanline. Guarding on the vblank flag alone gave **40,900 NMIs across 3,000 frames** and silently corrupted all game state, flattening coverage at 26%. - **Input goes on joy1 = `$4016`** with a real latch/shift register. The poll routine's `lda $4016,X` with X=1 lands on `$4017`, but only bits 0–1 are compared, so driving `$4017` consumes nothing and changes no coverage. - **A static trace cannot settle the code/data split; the emulator's Code Data Logger can.** The trace misses code behind computed dispatch, and it cannot tell inline string data from an instruction that decodes out of the same bytes — both leave the rebuild byte-identical while the split stays wrong. Mesen marks every PRG byte the CPU *fetched as an opcode* vs *read as data*; capture it with `mesen_cdl_file(action:'save', memoryType:'NesPrgRom', filepath:...)` (cumulative — it does not reset) and feed it to `_tools/cdl_reclass.py`, which rewrites the split to match wherever the CDL has an opinion and leaves the rest alone. Lunar Pool went 9,403 → 11,041 code bytes that way (1,738 data→code, 100 code→data) and then recorded zero disagreement with the CDL; 36 further bytes were moved by hand later (`$C113-$C11E`, `$C175-$C18C`), so its file now carries 11,077. Forcing the PC to reach unvisited code is *not* a general substitute: a routine that returns through a popped address runs away when entered that way and marks garbage as Code (Lunar Pool `$F81A`). - **A `jsr` to a helper that pops its own return address means the bytes after it are text, not code.** Lunar Pool's `$CBDC`/`$CBC9` pops the caller's return address into a pointer, prints a `$81`-prefixed, `$00`-terminated string (`$81` doubles as the word separator), then `rts`es to the byte after the terminator. A flat tracer started an instruction two bytes into "player" (`$6C $61 $79` = `jmp ($7961)`) and produced a plausible-looking "RAM-pointer dispatch gate" that does not exist — `$7961` is never written and `$6000–$7FFF` is unmapped on NROM. Suspect this shape whenever a `jmp ($xxxx)` operand spells ASCII. - **Odd vector targets are not bugs.** Burger Time's `$FF7F` NMI and CIRCUS's `$4CB7` IRQ point into unused space. That is common in this set — verify before assuming a handler is broken. - **Vectors are not in the iNES header.** They are the three little-endian words at the *end* of the 16 KB PRG (`$FFFA–$FFFF` in the `$C000` mirror). Bytes 0–9 of `rom.nes` carry only sizes, mirroring and mapper. The snippet to regenerate the whole column is in the root `OVERVIEW.md`. - **py65 is not a build dependency** and must be unpacked on demand: `python3 -m pip download --no-deps -d py65 && unzip -q /py65-*.whl -d /py65lib`. `/tmp` is volatile — a reboot wiped it once. Anything reusable belongs in `_tools/`. - **ROM filenames contain spaces and parentheses.** `copilot/rom.nes` is a relative symlink to a space-free name. Keep it working; don't rename it. - **`.gitignore` lists `ROMS/*` but the directory is `_ROMS`**, so the pattern matches nothing and ROM binaries stay tracked. Check before committing large blobs. ## Repo conventions that must survive - Every instruction carries a trailing `; CPU:$XXXX PRG:XXXX AA BB` comment with PRG offset and exact emitted bytes. **This is the byte-identity audit trail.** Preserve it even while renaming labels or restructuring files. **All 19 top-level projects now use this canonical format** (standardized 2026-10-19). - Unreached or unresolved bytes stay as `.byte`/`.word`/`.incbin` with ROM provenance. Never delete or reformat them away. - Two separate symbol files: `symbols.inc` = NES hardware constants only; `locals.inc` = zero page and forward references. Unresolved zero-page bytes keep neutral `ZpXX` names rather than speculative ones. - Routine headers follow the template in `prg.s`: global + local description, parameters, returns, clobbers. - Three passes, in order, without shortcuts: **Pass 1** code/data split (stop for review) → **Pass 2** label replacement → **Pass 3** data tables. Do not skip straight to guessy rewrites. - `make regen` (where it exists) must keep reproducing `prg.s` byte-for-byte on the standard library alone. MUSCLE has this pipeline; re-check it after any `nesdis.py` change. ## Where the detail lives - Root `OVERVIEW.md` — inventory of all 36 projects, per-project detail, the Pass 1 methodology note, and the audit-comment TODO with its full analysis. - `/OVERVIEW.md` — per-project architecture and pass status. The most detailed ones: `MUSCLE (U)` (Pass 3b/3c/3d), `Joypad Test Cartridge (U)`, `_wip/Mario Bros (JU)`. - `_tools/nesdis.py` — Pass 1 tracer (`--undocumented`, `--auto-seed`, `--extra-seed`, `--table`, `--data`, `--probe`). - `_tools/verify_pass1.py` — faithfulness + completeness check across all projects. - `_tools/audit_comment_tool.py` — adds canonical `; CPU:$XXXX PRG:XXXX AA BB` audit comments to disassembly source using tracer as ground truth. Usage: `python3 _tools/audit_comment_tool.py "Project Name"`. - `_tools/cdl_reclass.py` — reclassify a project's code/data split from a Mesen Code Data Logger capture (dry run by default; `--apply` rewrites `prg.s`, then `make` must still print BYTE-IDENTICAL). Its docstring covers capture and the safety rules. - `_tools/bytecode_dis.py`, `pass2.py`, `trace_stage_payload.py` — per-pass helpers. - `_tools/apply_symbols.py` — Pass 3 substitution: replaces numeric operands in `prg.s` with the names from `symbols.inc`/`locals.inc`. Multi-alias addresses need a `--sites linename` file (per-routine resolution); unlisted ones are reported as residue. Dry run by default, `--write` applies, and the audit comments are untouched. Worked example: `Balloon Fight (JU)`.