# 490d Mirror checkpoint after C318

24 September 2026. **C318 complete. C319 unexecuted.** 5 steps remain in the current C314–C323 authorization. Read this checkpoint and its report first; use the frozen predecessor checkpoint and certificate for inherited state. Do not repeat completed work or follow stale archived next-step paragraphs.

## Current finding

Thepaired−458 replacement decomposes as cumulative−460+2 and regular−650+130+60+2. All intermediate states pass; finalsource endpoints exist onlyi3…5. The sources permit ingredients but do not prescribe the exactpairedselection.

The paired458 replacement has a fully typed decomposition on the three rows where C287 is admitted. Its source ingredients are permitted, but the reviewed source passages do not prescribe this exact paired selection.

| Side | Explicit sequence | Net coordinate change |
|---|---|---:|
|Cumulative|LXX_OFF Shem_i→LXX_ON Shem_i→LXX_ON Shem_(i+2)|−460+2=−458|
|Regular|SP Flood_g OFF/T0→MT Flood_g OFF/T0→MT ON→MT ON/T60→MT Flood_(g+1), same boundary|−650+130+60+2=−458|

Full430 remains fixed. Each source-to-source step retains the selected start/close boundary. No person-companion is applied to MT or to Flood. The cumulative+2 is annual-member selection; the regular+2 is a permitted Noah/Shem/Flood Gear step. They are distinct operations.

The sign convention is explicit: cumulative coordinates are signed BC; regular values in this table are positive BC numbers, equivalently reflected coordinates. The corresponding unreflected signed regular changes would have opposite signs. Calling both actions−458 is valid only in this declared comparison frame.

All five rows admit the initial states and first three regular changes. Both final corners survive only i3/4/5, using SPG1/G2 and restored MTG2/G3. At i6/7 the cumulative final members8/9 and regularGear4 are absent. The formal arithmetic still computes a location there, but no source endpoint is added. Six exact-phase paths are source-admitted; four further component paths are formal failures at these boundaries.

The controlling identity is `650−130−60=460`. Therefore both sides have the same displacement and retain17K. The new short span is `600+(460−2)=1058=2K`, equivalent to the inherited `598+460`. File_18's regular variant fork, cumulative restoration rule, Flood table and restored-MT examples support the ingredients. This is a transparent relation between two previously admitted configurations, not an independent second derivation of every numeric premise.

## Retained context

C277–C310 and C311–C313 remain completed. C311 found no prescribing annual selector in its three-source audit; C312 admitted four complete cumulative transports and five SP targets; C313 found a center500 match only at j5 and no same-ancestry exact component500 match. The +155 regular normalization is local. C287 complete four-node indices remain2…5; direct17K admission is weaker. The original AD1905–1911 proposal remains unexecuted. Supplemental Engine ReportIII explicitly derives the LXX OFF field; older182/777 and mixed Cainan headings yield to File_18. Corrected LXX crossover8464 observations remain awareness only:1564→1700 and2484→2700, difference920→1000; AD3746/2300 is superseded. C-series and original unprefixed/Engine report series remain distinct.

Mirror/529 remains the focus: K=529, E=25/23, P=70/69. Global paired Mirror January AD1; local junction x=1 January AD2; no civil year zero. Regular Gears remain Noah/Shem/Flood only. SP minus-one companion is local to SP Noah/Shem. No cumulative/upstream Gear, new endpoint or phase, fitted anchor, global axis, z-law, canonical or graph edit. Capture now; canonize later. Source state, event identity, generated coordinate and phase ancestry remain distinct. Exact arithmetic and source membership do not establish intention or independent historical witnesses.

## Verification

57 main assertions and 14 frozen-input/predecessor checks passed. A second main replay produced byte-identical DATA and RESULTS. Separate review scope and agreement are recorded in the evidence. All frozen originals and standing controls remain unchanged. These are verification counts, not independent-witness counts.

## Best next bounded question

C319: Hold all source contexts fixed and toggle the cumulative+2 annual selection and regular+2 Gear selection independently in a four-case sensitivity test. Which17K and all-K relations actually require coupling them?

The decomposition exposes two distinct choices. Testing them independently will distinguish a source-permitted rectangle from the extra selection needed for its2K+15K form.

Continue within the authorized batch, reassessing after the next result.