release: v4.0.0b18 — fix zeroed existing capacity for scalar+Map entity classes

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: jkiviluo

CHANGELOG.md

@@ -1,3 +1,31 @@
+## Release 4.0.0b18 (30.6.2026) — fix zeroed existing capacity for scalar+Map entity classes
+
+No database migration (schema stays **v62**) and dependency floors unchanged
+(`polar-high>=3.2.0`, `polars>=1.40`, `highspy<=1.14.0`). Output-only fix — the
+converged solution (dispatch, investments, optimal objective) is unchanged.
+
+### Outputs
+
+- **Fix zeroed `existing` capacity for a unit whose constant value shares an
+  entity class with a period-Map sibling.** When one unit carries a scalar
+  (constant) `existing` capacity while another unit of the same class carries a
+  period-indexed Map, the Spine reader returns a single frame with one shared
+  index column (named `x` by Spine's silent default) in which the constant
+  unit's row has a **null** index. The per-entity resolver classified rows by the
+  *presence* of that column rather than per-row, so the null-index scalar became
+  an explicit `(entity, period=null)` row that never joined the period grid and
+  was silently filled with `0`. Downstream this zeroed the output-facing
+  existing/total capacity for such units — surfacing most visibly as **negative
+  VRE curtailment** (`potential − flow`, with `potential` computed from a `0`
+  capacity), and as `0` in the capacity, capacity-factor, and per-entity
+  pre-existing fixed-cost reports. The resolver now detects scalars per row (a
+  null index broadcasts the constant across the period universe), in both mirror
+  implementations. The LP itself was never affected — its flow bound reads a
+  separate, scalar-correct existing-count parameter, and existing fixed cost
+  enters the objective only as an opt-in constant term — so this is purely a
+  reporting fix; re-running output processing on an existing solve produces
+  correct reports without re-solving.
+
 ## Release 4.0.0b17 (30.6.2026) — autoscale centres the objective (no more "excessively small costs")
 
 No database migration (schema stays **v62**). Dependency floor raised to

pyproject.toml

@@ -7,7 +7,7 @@ name = "flextool"
 # restructure are in.  4.0.0 final follows after the remaining
 # minor-functionality additions, cleanup and testing land.  PEP 440
 # pre-release suffix: 4.0.0a1, 4.0.0a2, ... 4.0.0b1, 4.0.0rc1, then 4.0.0.
-version = "4.0.0b17"
+version = "4.0.0b18"
 description = "IRENA FlexTool is an energy and power systems model for understanding the role of variable power generation in future energy systems."
 readme = "README.md"
 license = { file = "LICENSE.txt" }