fix(submodel): allow 1.645 as an observation_code constant

src/maple/core/calibration/submodel_target.py

@@ -3080,7 +3080,9 @@ def validate_no_hardcoded_values_in_observation_code(self) -> "SubmodelTarget":
 
         Allowed constants:
         - 0, 1, 2 (indexing, basic arithmetic)
-        - 1.96 (95% CI convention)
+        - 1.96 (normal z for the 2.5th-97.5th / 95% CI range)
+        - 1.645 (normal z for the 5th-95th percentile range; box-plot whisker
+          convention, parallel to 1.96)
 
         NOT allowed (should be inputs):
         - Time conversions like 24.0, 60.0 (add as unit_conversion input)
@@ -3090,8 +3092,9 @@ def validate_no_hardcoded_values_in_observation_code(self) -> "SubmodelTarget":
         """
         import ast
 
-        # Minimal set of truly necessary constants
-        ALLOWED_CONSTANTS = {0, 0.0, 1, 1.0, 2, 2.0, 1.96}
+        # Minimal set of truly necessary constants (normal z-values for the two
+        # standard percentile ranges used in SD-from-percentile reconstructions).
+        ALLOWED_CONSTANTS = {0, 0.0, 1, 1.0, 2, 2.0, 1.96, 1.645}
 
         errors = []
 

tests/unit/core/test_submodel_target_validators.py

@@ -2110,3 +2110,29 @@ def test_percent_with_normal_shape_raises(self):
     def test_percent_with_logit_normal_passes(self):
         # logit_normal on a median-in-(0,1) percent observable is the correct shape.
         SubmodelTarget(**_percent_target("logit_normal"))
+
+
+# ============================================================================
+# Test that 1.645 (5th-95th percentile z) is an allowed observation_code constant,
+# parallel to 1.96 (2.5th-97.5th). The authoring prompt instructs 1.645 for
+# box-plot-whisker SD reconstruction, so the validator must not flag it.
+# ============================================================================
+
+CODE_WITH_1645 = """
+def derive_observation(inputs, sample_size, rng, n_bootstrap):
+    import numpy as np
+    sd = inputs['test_value'] / (2 * 1.645)
+    return rng.normal(inputs['test_value'], sd / np.sqrt(sample_size), n_bootstrap)
+"""
+
+
+class TestAllowedConstant1645:
+    """1.645 must be whitelisted like 1.96 in observation_code."""
+
+    def test_1645_not_flagged_as_hardcoded(self):
+        data = make_algebraic_target(input_value=10.0, measurement_error_code=CODE_WITH_1645)
+        try:
+            SubmodelTarget(**data)
+        except ValidationError as e:
+            msg = str(e)
+            assert "1.645" not in msg and "hardcoded" not in msg.lower(), msg