# 490d Mirror checkpoint after C315

24 September 2026. **C315 complete. C316 unexecuted.** 8 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

Five complete source biographies and ten exact components pass. None matches the same-ancestry8395 Flood endpoint: residual+2 in every case, with three wrongGear aliases and two unadmitted candidates.

All five reversed pairings extend to an admitted SP biography: **Noah birth →Shem birth →selected Flood boundary →Noah death →Shem death**, with ordered spans **500+100+350+150=1100**. Noah's950 and Shem's600 survive at both exact output phases.

| j / i | SP state | Full source chain, BC | Fixed8395 candidate | Actual alias |
|---|---|---|---:|---|
|3 /7|G3 primary|3710→3210→3110→2760→2610|3112|Absent|
|4 /6|G3 companion|3709→3209→3109→2759→2609|3111|Absent|
|5 /5|G2 primary|3708→3208→3108→2758→2608|3110|G3 Flood start|
|6 /4|G2 companion|3707→3207→3107→2757→2607|3109|G3 Flood close|
|7 /3|G1 primary|3706→3206→3106→2756→2606|3108|G2 Flood start|

The selected boundary is Flood **start for a primary person rail**, and Flood **close for a companion person rail**. Flood close is an existing event boundary, never a propagated SP person-companion. Against both boundaries the primary Noah gaps are600/601 and companion gaps599/600. File_18 §3.1.4 and §3.2.1 control these roles. Noah-death stations retain the source's primary inclusive/harmonic and companion qualifications.

The fixed paths use n=q+8993 and r=q+8395, so n−r=598. The coherent source boundary f=n−600 therefore satisfies **r−f=2**. All ten equal-output-phase comparisons retain this exact residual. Re-pairing available quarter-year components gives residuals3/2,2,5/2, never0. Changing8395 to8393 would force a same-ancestor endpoint but is not adopted.

Three candidate coordinates are admitted only as another Gear's Flood boundary; two have no admitted SP Flood at all in the fixed context. Substituting these candidates into the source biography gives Shem→candidate98 and candidate→Noah death352. Those are consequences of the same discrepancy, not new witnesses. The source500,600 and950 relations remain valid.

## 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

47 main assertions and 15 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

C316: Test the forced two-year cumulative ancestry displacement h=i−2 that would retain both17K and8395 while reaching each selected source Flood. Compare with permitted regular one-Gear descent only where its initial alias is admitted; retain all domain and phase boundaries.

C315 isolates an exact2-year mismatch. This tests an existing-station correspondence with unchanged constants and distinguishes it from an impermissible cumulative Gear operation or a fitted bridge.

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