feat(fees): junior rate for 2026-08 is 0

- 2026-08 added to the junior rate table at 0 CZK, same as adults
- A single practice in a 0-rate month is 0 instead of "?", since a
  free month needs no manual review
- Mirrored in Go and legacy Python; new calculate_junior_fee parity
  fixtures

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

CHANGELOG.md

@@ -1,5 +1,11 @@
 # Changelog
 
+## 2026-10-08 21:27 CEST — feat(fees): junior rate for 2026-08 is 0
+
+- Junior monthly rate for 2026-08: 500 → 0 CZK, same as adults.
+- A single practice in a 0-rate month is now 0 instead of `?`, since there is nothing to review in a free month. Other months are unchanged.
+- Mirrored in `go/internal/domain/fees/junior.go` and `legacy/scripts/attendance.py`; two new parity fixtures for `calculate_junior_fee`.
+
 ## 2026-10-08 12:37 CEST — feat(infer): messages starting with "other:" are not monthly fees
 
 - When the bank message starts with `other:` (case-insensitive), inference no longer looks for a month. It copies the trimmed message into Purpose, so the payment is linked to the person as an "other" transaction and not counted as a monthly fee. Messages that contain `other:` elsewhere are inferred as before.

CLAUDE.md

@@ -140,7 +140,7 @@ Tiers are set in column B of the attendance sheet:
 ### Fee calculation
 
 - Adults: 0 sessions → 0, 1 session → 200 CZK (never more than the month's rate, so a 0-rate month is free), 2+ sessions → monthly rate (default 600 CZK)
-- Juniors: 0 → 0, 1 → `"?"` (manual review required), 2+ → monthly rate (default 500 CZK)
+- Juniors: 0 → 0, 1 → `"?"` (manual review required; 0 in a 0-rate month), 2+ → monthly rate from `JuniorFeeMonthlyRate` / `JUNIOR_MONTHLY_RATE` (default 500 CZK)
 - Per-member per-month overrides live in the `exceptions` tab of the payments sheet (columns: Name, Period YYYY-MM, Amount, Note). Exceptions are keyed by `(normalize(name), normalize(period))`.
 
 ### Merged months

go/internal/domain/fees/junior.go

@@ -7,6 +7,7 @@ const JuniorFeeDefault = 500 // CZK fallback for 2+ practices when month not in
 var JuniorFeeMonthlyRate = map[string]int{
 	"2025-09": 250,
 	"2026-03": 250,
+	"2026-08": 0,
 }
 
 // Expected is the result of a junior fee calculation.
@@ -21,17 +22,19 @@ type Expected struct {
 // the given monthKey (format "YYYY-MM").
 //
 //	0 practices → Expected{Value: 0}
-//	1 practice  → Expected{Unknown: true}  (manual review; Python sentinel "?")
+//	1 practice  → Expected{Unknown: true}  (manual review; Python sentinel "?"),
+//	              or Expected{Value: 0} when the month's rate is 0
 //	2+          → Expected{Value: JuniorFeeMonthlyRate[monthKey] or JuniorFeeDefault}
 func CalculateJuniorFee(attendanceCount int, monthKey string) Expected {
 	if attendanceCount == 0 {
 		return Expected{Value: 0}
 	}
-	if attendanceCount == 1 {
+	rate, ok := JuniorFeeMonthlyRate[monthKey]
+	if !ok {
+		rate = JuniorFeeDefault
+	}
+	if attendanceCount == 1 && rate > 0 {
 		return Expected{Unknown: true}
 	}
-	if rate, ok := JuniorFeeMonthlyRate[monthKey]; ok {
 	return Expected{Value: rate}
-	}
-	return Expected{Value: JuniorFeeDefault}
 }

go/internal/domain/fees/junior_test.go

@@ -33,6 +33,9 @@ func TestCalculateJuniorFee(t *testing.T) {
 		{"two practices reduced sept", 2, "2025-09", mustRate("2025-09")},
 		{"two practices reduced march", 2, "2026-03", mustRate("2026-03")},
 		{"high count same as two", 5, "2025-09", mustRate("2025-09")},
+		// A 0-rate month is free, and a single practice needs no manual review.
+		{"two in free month is free", 2, "2026-08", Expected{Value: 0}},
+		{"single in free month is free", 1, "2026-08", Expected{Value: 0}},
 		// Two+ practices for an unknown/future month: must fall back to JuniorFeeDefault.
 		{"unknown future month falls back", 2, "2027-01", Expected{Value: JuniorFeeDefault}},
 		{"empty month falls back", 2, "", Expected{Value: JuniorFeeDefault}},

go/tests/fixtures/pure/calculate_junior_fee/one_session_free_august.json

@@ -0,0 +1,13 @@
+{
+  "case": "one_session_free_august",
+  "func": "scripts.attendance.calculate_junior_fee",
+  "captured_at": "2026-10-08",
+  "input": {
+    "attendance_count": 1,
+    "month_key": "2026-08"
+  },
+  "output": {
+    "value": 0,
+    "unknown": false
+  }
+}

go/tests/fixtures/pure/calculate_junior_fee/two_sessions_free_august.json

@@ -0,0 +1,13 @@
+{
+  "case": "two_sessions_free_august",
+  "func": "scripts.attendance.calculate_junior_fee",
+  "captured_at": "2026-10-08",
+  "input": {
+    "attendance_count": 2,
+    "month_key": "2026-08"
+  },
+  "output": {
+    "value": 0,
+    "unknown": false
+  }
+}

legacy/scripts/_fixture_seeds.py

@@ -146,6 +146,12 @@ SEEDS[("calculate_junior_fee", "two_sessions_reduced_sep")] = {
 SEEDS[("calculate_junior_fee", "two_sessions_default_fallback")] = {
     "attendance_count": 2, "month_key": "2099-06"
 }
+SEEDS[("calculate_junior_fee", "two_sessions_free_august")] = {
+    "attendance_count": 2, "month_key": "2026-08"
+}
+SEEDS[("calculate_junior_fee", "one_session_free_august")] = {
+    "attendance_count": 1, "month_key": "2026-08"
+}
 
 
 # --- parse_czk_amount ---

legacy/scripts/attendance.py

@@ -34,7 +34,8 @@ ADULT_FEE_MONTHLY_RATE = {
 JUNIOR_FEE_DEFAULT = 500  # CZK for 2+ practices
 JUNIOR_MONTHLY_RATE = {
     "2025-09": 250,
-    "2026-03": 250   # reduced fee for March 2026
+    "2026-03": 250,  # reduced fee for March 2026
+    "2026-08": 0,
 }
 ADULT_MERGED_MONTHS = {
     "2025-09": "2025-10",   # keys are merged into values
@@ -105,12 +106,13 @@ def calculate_fee(attendance_count: int, month_key: str) -> int:
 
 
 def calculate_junior_fee(attendance_count: int, month_key: str) -> str | int:
-    """Apply junior fee rules: 0 → 0, 1 → '?', 2+ → Configured Rate (default 500)."""
+    """Apply junior fee rules: 0 → 0, 1 → '?' (0 in a 0-rate month), 2+ → Configured Rate (default 500)."""
     if attendance_count == 0:
         return 0
-    if attendance_count == 1:
+    rate = JUNIOR_MONTHLY_RATE.get(month_key, JUNIOR_FEE_DEFAULT)
+    if attendance_count == 1 and rate > 0:
         return "?"
-    return JUNIOR_MONTHLY_RATE.get(month_key, JUNIOR_FEE_DEFAULT)
+    return rate
 
 
 def get_members(rows: list[list[str]]) -> list[tuple[str, str, list[str]]]: