feat(fees): adult rates for 2026-07 to 2026-12, default 600

- Default adult monthly rate 700 -> 600 CZK
- 2026-07 and 2026-08 set to 0; 2026-09 through 2026-12 added at 600
- Single-session fee is capped at the month's rate, so a 0-rate month
  is free for one session as well
- Mirrored in Go and legacy Python; new calculate_fee parity fixtures

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

.gitea/workflows/kubernetes-deploy.yaml

@@ -1,111 +0,0 @@
-name: Deploy to K8s
-on:
-  workflow_dispatch:
-  push:
-    branches:
-      - '**'
-jobs:
-  deploy:
-    runs-on: ubuntu-latest
-    steps:
-      - name: Checkout
-        uses: actions/checkout@v4
-
-      - name: Debug - print Gitea Actions environment
-        run: |
-          echo "=== All environment variables ==="
-          env | sort
-          echo ""
-          echo "=== GITHUB_* / GITEA_* / ACTIONS_* vars ==="
-          env | grep -E '^(GITHUB|GITEA|ACTIONS)_' | sort
-
-      - name: Install kubectl
-        run: |
-          curl -sfLO "https://dl.k8s.io/release/$(curl -sfL https://dl.k8s.io/release/stable.txt)/bin/linux/amd64/kubectl"
-          install kubectl /usr/local/bin/
-
-      - name: Get Kanidm token from Vault
-        id: vault
-        run: |
-          set -euxo pipefail
-
-          VAULT_AUTH_RESPONSE=$(curl -f --request POST \
-            --data '{"role_id":"${{ secrets.VAULT_ROLE_ID }}","secret_id":"${{ secrets.VAULT_SECRET_ID }}"}' \
-            https://vault.hrajfrisbee.cz/v1/auth/approle/login)
-
-          echo "Vault auth response: $VAULT_AUTH_RESPONSE" >&2
-          VAULT_TOKEN=$(echo "$VAULT_AUTH_RESPONSE" | jq -r '.auth.client_token')
-
-          # Read the kanidm API token
-          SECRET_RESPONSE=$(curl -f \
-            -H "X-Vault-Token: ${VAULT_TOKEN}" \
-            https://vault.hrajfrisbee.cz/v1/secret/data/gitea/gitea-ci)
-
-          echo "Secret response: $SECRET_RESPONSE" >&2
-          API_TOKEN=$(echo "$SECRET_RESPONSE" | jq -r '.data.data.token')
-
-          echo "::add-mask::${API_TOKEN}"
-          echo "api_token=${API_TOKEN}" >> "$GITHUB_OUTPUT"
-
-      - name: Exchange for K8s OIDC token via Kanidm
-        id: k8s
-        run: |
-          API_TOKEN="${{ steps.vault.outputs.api_token }}"
-          echo "api_token length: ${#API_TOKEN}" >&2
-          echo "api_token prefix (first 8 chars): ${API_TOKEN:0:8}..." >&2
-
-          HTTP_BODY=$(mktemp)
-          HTTP_STATUS=$(curl -sS -X POST "https://idm.home.hrajfrisbee.cz/oauth2/token" \
-            -d "grant_type=urn:ietf:params:oauth:grant-type:token-exchange" \
-            -d "client_id=k8s" \
-            -d "subject_token=${API_TOKEN}" \
-            -d "subject_token_type=urn:ietf:params:oauth:token-type:access_token" \
-            -d "audience=k8s" \
-            -d "scope=openid groups" \
-            -o "$HTTP_BODY" -w "%{http_code}")
-
-          echo "HTTP status: $HTTP_STATUS" >&2
-          echo "Response body:" >&2
-          cat "$HTTP_BODY" >&2
-
-          RESPONSE=$(cat "$HTTP_BODY")
-          ID_TOKEN=$(echo "$RESPONSE" | jq -r '.id_token // empty')
-
-          if [ -z "$ID_TOKEN" ]; then
-            echo "::error::Kanidm token exchange failed (HTTP $HTTP_STATUS)"
-            exit 1
-          fi
-
-          echo "::add-mask::${ID_TOKEN}"
-          echo "id_token=${ID_TOKEN}" >> "$GITHUB_OUTPUT"
-
-          # Sanity check
-          # Warning - this is the part that is failing
-          # echo "$ID_TOKEN" | cut -d. -f2 | base64 -d 2>/dev/null | jq '{sub, groups, exp}'
-
-
-      - name: Debug - print environment before kubectl
-        run: env | sort
-
-      - name: Configure kubectl & deploy
-        run: |
-          echo "${{ secrets.K8S_CA_CERT }}" > /tmp/ca.crt
-          
-          kubectl config set-cluster mycluster \
-            --server=https://192.168.0.31:6443 \
-            --insecure-skip-tls-verify=true          
-          # --certificate-authority=/tmp/ca.crt \
-
-          kubectl config set-credentials gitea-ci \
-            --token="${{ steps.k8s.outputs.id_token }}"
-
-          kubectl config set-context gitea-ci \
-            --cluster=mycluster --user=gitea-ci
-
-          kubectl config use-context gitea-ci
-
-          kubectl auth whoami
-          kubectl get ns
-
-          # your deploy here
-          # kubectl apply -f k8s/

CHANGELOG.md

@@ -1,5 +1,29 @@
 # Changelog
 
+## 2026-10-08 11:53 CEST — feat(fees): adult rates for 2026-07 through 2026-12, default 600
+
+- Adult default monthly rate (months not in the table): 700 → 600 CZK.
+- 2026-07 and 2026-08: 600 → 0 CZK; 2026-09 through 2026-12 added at 600 CZK (September and October were previously billed at the old 700 default).
+- The single-session fee (200 CZK) is now capped at the month's rate, so a 0-rate month is free for one session too.
+- Mirrored in `go/internal/domain/fees/fees.go` and `legacy/scripts/attendance.py`; three new parity fixtures for `calculate_fee`.
+
+## 2026-10-08 11:48 CEST — fix(ci): remove kubernetes-deploy workflow that leaked secrets to logs
+
+- Deleted `.gitea/workflows/kubernetes-deploy.yaml`. It ran on every push to every branch, deployed nothing, and echoed the Vault login response, the Kanidm API token response and the OIDC token response to the job log.
+- Deployment is handled by `gitops-update.yaml`. Repo secrets `VAULT_ROLE_ID`, `VAULT_SECRET_ID` and `K8S_CA_CERT` are now unused.
+- Follow-up outside the repo: rotate the Vault AppRole secret and the Kanidm API token, and clear old job logs.
+
+## 2026-10-08 11:34 CEST — fix(python): return months_to_show from /api/adults and /api/juniors
+
+- Go already returned `months_to_show` in the JSON API; Python only passed it to its HTML templates. Backported the key so the API contract matches and `make parity` reports 3/3 routes.
+- Key files: `legacy/app.py`, `legacy/tests/test_app.py`.
+
+## 2026-10-08 11:34 CEST — fix: VS is always a string, on read and on write
+
+- Go rendered numeric sheet cells with `fmt.Sprint`, so a numeric VS came out as `2.609767878e+09`. Text columns of the payments sheet now go through `sheets.CellString` (plain digits); bank inference uses it too.
+- Both sync implementations now append VS as a text cell (leading apostrophe under `USER_ENTERED`), so Sheets no longer stores it as a number or drops leading zeros. Existing rows are unchanged.
+- Key files: `go/internal/io/sheets/cell.go`, `go/internal/services/membership/sources.go`, `go/internal/services/banksync/{sync,infer}.go`, `legacy/scripts/sync_fio_to_sheets.py`.
+
 ## 2026-10-08 11:33 CEST — refactor: move Python implementation to legacy/, Go is primary
 
 - Go (`go/`) is now the primary implementation. The original Python version moved to `legacy/` (`app.py`, `scripts/`, `templates/`, `tests/`, `pyproject.toml`, `uv.lock`, `build/`) and is considered legacy; new features are still built in both.

CLAUDE.md

@@ -126,13 +126,13 @@ Fio Bank API               ──► bank sync ──► Google Sheets (payments
 ### Member tiers
 
 Tiers are set in column B of the attendance sheet:
-- `A` — Adult, pays fees (per-month rate from `AdultFeeMonthlyRate` / `ADULT_FEE_MONTHLY_RATE`, fallback 700 CZK for 2+ sessions; 200 CZK for exactly 1)
+- `A` — Adult, pays fees (per-month rate from `AdultFeeMonthlyRate` / `ADULT_FEE_MONTHLY_RATE`, fallback 600 CZK for 2+ sessions; 200 CZK for exactly 1, capped at the month's rate)
 - `J` — Junior attending adult practices; their attendance is merged with the junior sheet
 - `X` — Excluded from junior fee calculation (coaches, etc.)
 
 ### Fee calculation
 
-- Adults: 0 sessions → 0, 1 session → 200 CZK, 2+ sessions → monthly rate (default 700 CZK)
+- 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)
 - 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))`.
 

docs/by-claude-opus/README.md

@@ -182,7 +182,7 @@ fuj-management/
 │
 ├── .gitea/workflows/
 │   ├── build.yaml                  # CI: build + push Docker image
-│   └── kubernetes-deploy.yaml      # CD: deploy to K8s cluster
+│   └── gitops-update.yaml          # CD: open image-update PR in home-kubernetes
 │
 ├── .secret/                        # (gitignored) API credentials
 ├── docs/                           # Project documentation

docs/by-claude-opus/deployment.md

@@ -129,32 +129,27 @@ The project uses two Gitea Actions workflows:
 
 **Tag resolution**: Uses the git tag name. For manual dispatch, uses the provided input.
 
-#### 2. Deploy to Kubernetes (`kubernetes-deploy.yaml`)
+#### 2. GitOps image update (`gitops-update.yaml`)
 
 **Triggers**:
-- Push to any branch
+- Completion of a successful "Build and Push" run
-- Manual dispatch
+- Manual dispatch (with `tag`, `dry_run` and `uh_cli_version` inputs)
 
 **Steps**:
-1. Checkout code
+1. Install `tea` and `uh-cli`
-2. Install kubectl
+2. Resolve the image tag of the Go image that was just built
-3. Retrieve Kanidm token from HashiCorp Vault:
+3. Open a PR in `kacerr/home-kubernetes` bumping the `fuj-management` Deployment (namespace `fuj`) to that image
-   - Authenticate to Vault via AppRole (`VAULT_ROLE_ID` / `VAULT_SECRET_ID`)
+
-   - Fetch API token from `secret/data/gitea/gitea-ci`
+The cluster picks the change up once that PR is merged. CI does not talk to the cluster directly.
-4. Exchange API token for K8s OIDC token via Kanidm:
+
-   - POST to `https://idm.home.hrajfrisbee.cz/oauth2/token`
+> The earlier `kubernetes-deploy.yaml` workflow (Vault → Kanidm → `kubectl`) was removed on 2026-10-08. It never deployed anything and printed credentials to the job log.
-   - Token exchange using `urn:ietf:params:oauth:grant-type:token-exchange`
-5. Configure kubectl with the OIDC token
-6. Run `kubectl auth whoami` and `kubectl get ns` (deploy commands are commented out — WIP)
 
 **Required secrets**:
 
 | Secret | Purpose |
 |--------|---------|
 | `REGISTRY_TOKEN` | Docker registry authentication |
-| `VAULT_ROLE_ID` | HashiCorp Vault AppRole role ID |
+| `GITOPS_TOKEN` | Gitea token with write and PR access to `home-kubernetes` |
-| `VAULT_SECRET_ID` | HashiCorp Vault AppRole secret ID |
-| `K8S_CA_CERT` | Kubernetes cluster CA certificate |
 
 ### Infrastructure Topology
 
@@ -164,8 +159,7 @@ Gitea (git push / tag)
    ├── build.yaml → Docker Build → Gitea Container Registry
    │                                  (gitea.home.hrajfrisbee.cz)
    │
-   └── kubernetes-deploy.yaml → Vault → Kanidm → K8s Cluster
+   └── gitops-update.yaml → PR in home-kubernetes → K8s Cluster
-                                                   (192.168.0.31:6443)
 ```
 
 This is a self-hosted infrastructure stack:

docs/plans/2026-10-08-1026-pre-feature-cleanup-tasks.md

@@ -0,0 +1,164 @@
+# Pre-feature cleanup — task list
+
+Findings from a full repo audit on 2026-10-08, written up as tasks to clear
+before new feature work starts. Companion to the Go rewrite tracker,
+[2026-05-03-2349-go-backend-rewrite-progress.md](2026-05-03-2349-go-backend-rewrite-progress.md).
+
+## State at audit time
+
+- Two full implementations live side by side: Flask (`app.py`, `scripts/`,
+  `templates/`) and Go (`go/`). Recent changes were made in both.
+- Update 2026-10-08: the Python code was moved to `legacy/` after this audit.
+  Python paths below are relative to `legacy/` (`build/Dockerfile` is now
+  `legacy/build/Dockerfile`).
+- Python tests pass (32 tests). Go unit tests and the parity suite pass.
+  Go lint could not run (see T7).
+- The gitops workflow bumps the cluster deployment to the `-go` image, so Go
+  appears to be what is deployed. This was not verified against the cluster.
+- `CLAUDE.md` and all docs outside `docs/plans/` describe a Python-only
+  project. The rewrite tracker stops at M6; M7 and M8 are untouched.
+
+## How to use
+
+- Tick a checkbox when the task's PR or commit lands and append the SHA.
+- Tasks in "Fix first" are small and independent of each other and of the
+  cutover decision. Do them in any order.
+- T5 is a decision. Several cleanup tasks become unnecessary once it is made;
+  they are marked "moot if Python is retired".
+
+---
+
+## Fix first
+
+- [x] **T1** Remove the secret leak in `.gitea/workflows/kubernetes-deploy.yaml`.
+  Workflow deleted on 2026-10-08. Still open for the owner: rotate the
+  credentials and remove the now-unused repo secrets (see below).
+  - It runs on every push to every branch and deploys nothing.
+  - It echoes the raw Vault login response, the Kanidm token response and the
+    OIDC token response body to the log, and dumps the environment twice.
+  - It uses `--insecure-skip-tls-verify=true`.
+  - Delete or disable the workflow. Rotate the Vault AppRole secret and the
+    Kanidm API token if anyone else can read the CI logs.
+  - After deletion the repo secrets `VAULT_ROLE_ID`, `VAULT_SECRET_ID` and
+    `K8S_CA_CERT` are unused and can be removed. Old job logs still contain
+    the leaked tokens until they are deleted or expire.
+- [x] **T2** Confirm the fee rates for 2026-09 onward. Done 2026-10-08:
+  adult default 600, 2026-07/08 at 0, 2026-09 to 2026-12 at 600. Junior
+  rates were not changed.
+  - `ADULT_FEE_MONTHLY_RATE` ends at 2026-08 in `scripts/attendance.py` and
+    `go/internal/domain/fees/fees.go`.
+  - September and October 2026 are billed at the defaults: 700 CZK adults,
+    500 CZK juniors.
+  - If those are not the intended rates, add the months in both files.
+- [ ] **T3** Remove the hardcoded 2026 window from Python `/sync-bank`
+  (`app.py`, the `sync_to_sheets` call with `2026-01-01` / `2026-12-31`).
+  - It stops picking up transactions on 2027-01-01. Go already uses the
+    current year.
+  - Same applies to the `sync-2026` Makefile target.
+  - Moot if Python is retired before then.
+- [ ] **T4** Remove member names from tracked files (PII rule in `CLAUDE.md`).
+  - `CHANGELOG.md` line 29 names a member in a fix description.
+  - `tests/test_match_payments.py`, `tests/test_reconcile_exceptions.py` and
+    `go/internal/domain/reconcile/reconcile_test.go` use names that may be
+    real. Check them and replace with obviously fictional ones.
+  - Three files in `docs/plans/` contain the same names:
+    `2026-05-05-1717-payment-person-name-canonicalization.md`,
+    `2026-05-06-1626-infer-payments-junior-roster.md`,
+    `2026-05-11-2353-fill-first-multi-month-allocation.md`.
+  - The parity fixtures under `go/tests/fixtures/` are scrubbed and need no
+    change.
+  - Decide whether the names also need removing from git history.
+
+## Decide before new features
+
+- [ ] **T5** Decide how to finish the Python → Go cutover (M7 and M8 in the
+  rewrite tracker).
+  - Recommended: declare Go primary now, freeze Python, run one month-end
+    comparison of the balance report on both sides, then delete Python.
+  - Until this is done, every feature has to be written twice.
+  - Confirm first that the cluster really runs the `-go` image.
+- [ ] **T6** Add a test job to CI.
+  - `.gitea/workflows/build.yaml` only builds images on tag push. Nothing
+    runs tests.
+  - Run `go test -race ./...`, the parity suite (`-tags=parity`) and
+    `golangci-lint` on pull requests.
+  - Stop building the Python image on every tag once Python is retired.
+- [ ] **T7** Fix `make go-lint`.
+  - `go/.golangci.yml` is in the v1 config format. golangci-lint 2.12 refuses
+    to load it ("unsupported version of the configuration").
+  - Migrate the config to v2 and pin the linter version used in CI.
+- [ ] **T8** Protect the side-effectful routes.
+  - Neither app has any authentication.
+  - `GET /sync-bank` writes to the payments sheet, so a link prefetcher or
+    crawler can trigger a sync. Change it to POST with a confirmation page,
+    as `/flush-cache` already does.
+  - Confirm that the ingress enforces access control, or add it in the app.
+  - The Go server uses `http.ListenAndServe` with no read, write or idle
+    timeouts (`go/internal/web/server.go`). Use an `http.Server` with
+    timeouts.
+- [ ] **T9** Move fee rates and merged months out of code.
+  - Today a rate change needs a code change in two languages and a release.
+  - Candidate: a tab in the payments sheet, read the same way as
+    `exceptions`.
+  - This also removes the cause of T2.
+
+## Cleanup
+
+- [x] **T10** Rewrite `CLAUDE.md` for the current state: Go commands,
+  architecture and key modules, and which backend is primary. Done with the
+  move of Python to `legacy/`.
+- [ ] **T11** Collapse the documentation into one set.
+  - `docs/by-claude-opus/`, `docs/by-gemini/` and the top-level docs overlap,
+    date from February–March 2026 and predate the Go rewrite.
+  - Update `docs/_sidebar.md` and `docs/README.md` to match.
+- [ ] **T12** Update the rewrite tracker.
+  - M6.7 is unchecked although the changelog records it as done.
+  - M7.1 and M8.4 refer to a `docker-compose.yml` that does not exist.
+- [ ] **T13** Remove leftovers: `.agent/rules.md` (Antigravity config) and
+  `prompts/`.
+- [ ] **T14** Prune merged branches: 42 local and 44 remote branches are
+  fully merged into `main`.
+- [ ] **T15** Clean up `.claude/settings.json`.
+  - It is tracked and contains absolute paths under one user's home
+    directory and one-off commands.
+  - Keep only shared, generic permissions there; move the rest to
+    `.claude/settings.local.json`, which is already ignored.
+- [ ] **T16** Align versions.
+  - `pyproject.toml` says `0.10`; git tags are at `0.39`.
+  - `build/Dockerfile` pip-installs unpinned packages and ignores `uv.lock`.
+  - `go.mod` and `go/build/Dockerfile` are on Go 1.26; the local toolchain is
+    1.27.
+  - Dependencies on both sides are a few months behind.
+  - The Python items are moot if Python is retired.
+- [ ] **T17** Stop the Python tests from calling live Google APIs.
+  - `warmup_cache()` runs at import of `app.py`, so `make test` makes real
+    Drive and Sheets read calls and needs the credentials file.
+  - Moot if Python is retired.
+- [ ] **T18** Set the time zone in the Go container.
+  - The image has no time zone configured, so `time.Now()` is UTC and the
+    "current month" flips one to two hours late at month boundaries.
+  - The Python image sets `Europe/Prague`.
+- [ ] **T19** Decide where `fujarna/` lives.
+  - `fujarna/project.md` is untracked. It is a brief for a separate
+    tournament website and shares almost nothing with this codebase.
+  - Options: its own repository, or a clearly separate Go module here.
+- [ ] **T20** Add tests for the untested Go packages: `cmd/fuj`,
+  `internal/io/sheets`, `internal/io/drive`, `internal/config` (about 590
+  lines in total).
+
+## Found during validation of the `legacy/` move
+
+Plan: [2026-10-08-1103-api-parity-vs-months-to-show.md](2026-10-08-1103-api-parity-vs-months-to-show.md).
+
+- [x] **T21** Go rendered numeric VS cells in exponent form
+  (`2.609767878e+09`). Sheet text cells now go through `sheets.CellString`.
+- [x] **T22** Python `/api/adults` and `/api/juniors` did not return
+  `months_to_show`. Backported; `make parity` reports 3/3 routes matching.
+- [x] **T23** Write VS to the payments sheet as text. Both sync
+  implementations use `USER_ENTERED`, so Sheets stored VS as a number and
+  dropped leading zeros. New rows now carry a text marker; existing rows are
+  left as they are and are read correctly either way.
+
+## Notes & decisions
+
+(Add entries as you go. Format: `YYYY-MM-DD — short note`.)

docs/plans/2026-10-08-1103-api-parity-vs-months-to-show.md

@@ -0,0 +1,112 @@
+# Fix the two Go/Python parity differences
+
+## Context
+
+Running `make parity` against both containers on 2026-10-08 reported
+`0/3 routes match`. Two causes, neither related to the move to `legacy/`:
+
+1. **VS rendered in scientific notation by Go.** The payments sheet is read
+   with `UNFORMATTED_VALUE`, so a numeric VS cell arrives as `float64`. Go
+   stringifies cells with `fmt.Sprint`, which prints any float ≥ 1e6 in
+   exponent form (`2.609767878e+09`). Python already converts integer floats
+   to plain digits for VS (`get_str` in `fetch_sheet_data`). VS must always be
+   a plain string.
+2. **`months_to_show` missing from the Python JSON API.** Go returns it in
+   `/api/adults` and `/api/juniors` (and it is `required` in the committed
+   schemas). Python already has the feature in its HTML pages
+   (`MONTHS_TO_SHOW` is passed to the templates) but never added the key to
+   the API responses. Backport the key so the API contract matches.
+
+Outcome: `make parity` reports 3/3 routes matching.
+
+## Branching
+
+Both are bug fixes that touch `legacy/` paths, so they depend on the
+uncommitted `feat/python-to-legacy` work. Commit that branch first (still
+awaiting confirmation), then branch `fix/api-parity-vs-months-to-show` from
+it, with one commit per task. Open the MR with `tea` after the legacy move is
+merged, or target it at that branch.
+
+## Task 1 — VS (and other text cells) always a plain string in Go
+
+Root cause is `getVal` in `parseTransactionRows`
+(`go/internal/services/membership/sources.go`, the `fmt.Sprint(row[i])`
+closure). The same pattern exists in `get` in
+`go/internal/services/banksync/infer.go`.
+
+1. Add `CellString(v any) string` to `go/internal/io/sheets` (new small file
+   `cell.go`; both services already import this package):
+   - `nil` → `""`
+   - `float64` → `strconv.FormatFloat(x, 'f', -1, 64)` (never exponent form;
+     `2609767878.0` → `"2609767878"`, `12.5` → `"12.5"`)
+   - `string` → unchanged
+   - anything else → `fmt.Sprint(v)`
+2. Use it in `getVal` in `sources.go`. This fixes VS and protects the other
+   text columns (Message, Bank ID, Sender, …) from the same failure.
+   - `getVal` currently returns `"<nil>"` for nil cells and the inferred-amount
+     code checks for that literal; simplify that check to `iv != ""`.
+   - Leave `getRaw`/`FormatDate` and `parseFloat` for Date and Amount as they
+     are — those must stay numeric.
+3. Use it in `get` in `banksync/infer.go` (keeping the `TrimSpace`), so
+   inference sees the same text the dashboard shows.
+4. Tests:
+   - `go/internal/io/sheets/cell_test.go`: table test for `CellString`
+     (large integer float, small integer float, fractional, string with
+     leading zeros, nil).
+   - Extend `TestLoadTransactions` in
+     `go/internal/services/membership/sources_test.go` with a row whose VS is
+     `2609767878.0` and whose Bank ID is an 11-digit float; assert plain
+     digit strings.
+5. Python: no code change needed — `get_str` already does this for VS. Add one
+   regression test for `fetch_sheet_data` in
+   `legacy/tests/test_match_payments.py` (mock the Sheets service, numeric VS
+   cell → `"2609767878"`) so the two sides are pinned to the same behaviour.
+
+Not included (note for later): VS is *written* to the sheet with
+`USER_ENTERED` by both sync implementations, so Sheets stores it as a number
+and drops leading zeros. Fixing that means writing VS as text and is a
+separate change to the sheet's data.
+
+## Task 2 — backport `months_to_show` to the Python JSON API
+
+`legacy/app.py` only; `MONTHS_TO_SHOW` is already imported there.
+
+1. In `api_adults()` and `api_juniors()`, add the key to the response:
+   build `out = _unwrap_view_model_for_api(vm)`, set
+   `out["months_to_show"] = MONTHS_TO_SHOW`, return `jsonify(out)`.
+   - Do not add it inside `build_*_view_model` or `_unwrap_view_model_for_api`:
+     the HTML routes already pass `months_to_show=` to `render_template`
+     alongside `**vm`, and a duplicate key would raise `TypeError`.
+   - `/api/payments` is unchanged; Go does not return the key there.
+2. Tests in `legacy/tests/test_app.py`:
+   - Add `"months_to_show"` to the expected key list used by
+     `test_api_adults` / `test_api_juniors` (the tuple near the top of the
+     file), and assert the value is an `int`.
+3. Go: no change. The key and schemas
+   (`go/tests/fixtures/api-schema/{adults,juniors}.schema.json`) already
+   contain it.
+
+## Wrap-up
+
+- `CHANGELOG.md` entry at the top (after confirmation it works), per repo
+  convention.
+- Copy this plan to
+  `docs/plans/2026-10-08-HHMM-api-parity-vs-months-to-show.md`, per the repo's
+  plan-location rule.
+- Add both items to
+  `docs/plans/2026-10-08-1026-pre-feature-cleanup-tasks.md` as done tasks so
+  the audit list stays complete.
+
+## Verification
+
+1. `make go-test-all` — unit tests (including the new ones) and parity
+   fixtures pass.
+2. `make test` — Python tests pass, including the new API key and VS tests.
+3. `cd go && go test ./internal/web/api/...` — schema golden test still
+   matches (no schema change expected).
+4. End to end: start `make web-py` and `make web-go`, then `make parity`;
+   expect `3/3 routes match`. Alternatively repeat the two-container run used
+   to find the bugs (`make image`, Go image from `go/build/Dockerfile`, then
+   `go run ./cmd/parity -py … -go …`).
+5. Open `/payments` on :8080 and check the affected transaction's VS shows as
+   plain digits.

go/internal/domain/fees/fees.go

@@ -2,7 +2,7 @@
 package fees
 
 const (
-	AdultFeeDefault = 700 // CZK fallback for 2+ practices when month not in AdultFeeMonthlyRate
+	AdultFeeDefault = 600 // CZK fallback for 2+ practices when month not in AdultFeeMonthlyRate
 	AdultFeeSingle  = 200 // CZK for exactly 1 practice
 )
 
@@ -11,24 +11,27 @@ const (
 var AdultFeeMonthlyRate = map[string]int{
 	"2025-09": 750, "2025-10": 750, "2025-11": 750, "2025-12": 750,
 	"2026-01": 750, "2026-02": 750, "2026-03": 350,
-	"2026-04": 700, "2026-05": 450, "2026-06": 600, "2026-07": 600, "2026-08": 600,
+	"2026-04": 700, "2026-05": 450, "2026-06": 600, "2026-07": 0, "2026-08": 0,
+	"2026-09": 600, "2026-10": 600, "2026-11": 600, "2026-12": 600,
 }
 
 // CalculateFee returns the adult fee in CZK for attendanceCount practices in
 // the given monthKey (format "YYYY-MM").
 //
 //	0 practices → 0
-//	1 practice  → AdultFeeSingle (200)
+//	1 practice  → AdultFeeSingle (200), capped at the month's rate so a
+//	              0-rate month is free for everyone
 //	2+          → AdultFeeMonthlyRate[monthKey] or AdultFeeDefault
 func CalculateFee(attendanceCount int, monthKey string) int {
 	if attendanceCount == 0 {
 		return 0
 	}
+	rate, ok := AdultFeeMonthlyRate[monthKey]
+	if !ok {
+		rate = AdultFeeDefault
+	}
 	if attendanceCount == 1 {
-		return AdultFeeSingle
+		return min(AdultFeeSingle, rate)
 	}
-	if rate, ok := AdultFeeMonthlyRate[monthKey]; ok {
+	return rate
-		return rate
-	}
-	return AdultFeeDefault
 }

go/internal/domain/fees/fees_test.go

@@ -26,9 +26,11 @@ func TestCalculateFee(t *testing.T) {
 		// Zero attendance always returns 0.
 		{"zero short-circuits", 0, "2026-05", 0},
 		{"zero empty month", 0, "", 0},
-		// Single practice returns AdultFeeSingle regardless of month.
+		// Single practice returns AdultFeeSingle, capped at the month's rate.
 		{"single practice", 1, "2026-05", AdultFeeSingle},
-		{"single ignores monthKey", 1, "unknown", AdultFeeSingle},
+		{"single unknown month", 1, "unknown", AdultFeeSingle},
+		{"single in free month is free", 1, "2026-07", 0},
+		{"two in free month is free", 2, "2026-08", 0},
 		// Two+ practices for a configured month: must use the map value, not the default.
 		// Expected values are read from AdultFeeMonthlyRate so this test stays correct
 		// when rates are updated — the assertion verifies dispatch logic, not rate values.

go/internal/io/sheets/cell.go

@@ -0,0 +1,33 @@
+package sheets
+
+import (
+	"fmt"
+	"strconv"
+)
+
+// CellString renders a cell read with UNFORMATTED_VALUE as text.
+// Numeric cells arrive as float64; fmt.Sprint would print large ones in
+// exponent form ("2.609767878e+09"), which corrupts identifiers such as VS
+// or Bank ID. Mirrors get_str in legacy/scripts/match_payments.py.
+func CellString(v any) string {
+	switch x := v.(type) {
+	case nil:
+		return ""
+	case string:
+		return x
+	case float64:
+		return strconv.FormatFloat(x, 'f', -1, 64)
+	}
+	return fmt.Sprint(v)
+}
+
+// TextCell marks s to be stored as text when written with USER_ENTERED:
+// a leading apostrophe stops Sheets from parsing digits as a number (which
+// would drop leading zeros). The apostrophe is not part of the stored value.
+// Empty stays empty. Mirrors as_text_cell in legacy/scripts/sync_fio_to_sheets.py.
+func TextCell(s string) string {
+	if s == "" {
+		return ""
+	}
+	return "'" + s
+}

go/internal/io/sheets/cell_test.go

@@ -0,0 +1,36 @@
+package sheets
+
+import "testing"
+
+func TestTextCell(t *testing.T) {
+	if got := TextCell("0308"); got != "'0308" {
+		t.Errorf(`TextCell("0308"): got %q`, got)
+	}
+	if got := TextCell(""); got != "" {
+		t.Errorf(`TextCell(""): got %q`, got)
+	}
+}
+
+func TestCellString(t *testing.T) {
+	cases := []struct {
+		name string
+		in   any
+		want string
+	}{
+		{"nil", nil, ""},
+		{"string", "fee", "fee"},
+		{"string with leading zeros", "0308", "0308"},
+		{"small integer float", 123.0, "123"},
+		{"large integer float", 2609767878.0, "2609767878"},
+		{"eleven digit float", 26123456789.0, "26123456789"},
+		{"fractional float", 12.5, "12.5"},
+		{"bool", true, "true"},
+	}
+	for _, tc := range cases {
+		t.Run(tc.name, func(t *testing.T) {
+			if got := CellString(tc.in); got != tc.want {
+				t.Errorf("CellString(%v): want %q, got %q", tc.in, tc.want, got)
+			}
+		})
+	}
+}

go/internal/services/banksync/infer.go

@@ -94,7 +94,7 @@ func InferPayments(
 			if idx < 0 || idx >= len(row) {
 				return ""
 			}
-			return strings.TrimSpace(fmt.Sprint(row[idx]))
+			return strings.TrimSpace(sheets.CellString(row[idx]))
 		}
 
 		// Skip rule: any of manual fix / Person / Purpose non-empty → leave alone

go/internal/services/banksync/sync.go

@@ -6,6 +6,7 @@ import (
 	"fmt"
 	"fuj-management/go/internal/domain/synch"
 	"fuj-management/go/internal/io/fio"
+	"fuj-management/go/internal/io/sheets"
 	"os"
 	"strings"
 	"time"
@@ -130,7 +131,7 @@ func SyncToSheets(
 		newRows = append(newRows, []any{
 			tx.Date, tx.Amount,
 			"", "", "", "", // manual fix, Person, Purpose, Inferred Amount
-			tx.Sender, tx.VS, tx.Message, tx.BankID, syncIDs[i],
+			tx.Sender, sheets.TextCell(tx.VS), tx.Message, tx.BankID, syncIDs[i],
 		})
 	}
 
@@ -141,7 +142,7 @@ func SyncToSheets(
 	if opts.DryRun {
 		for _, row := range newRows {
 			fmt.Printf("Dry run: would append date=%v amount=%v sender=%v vs=%v message=%v\n",
-				row[0], row[1], row[6], row[7], row[8])
+				row[0], row[1], row[6], strings.TrimPrefix(fmt.Sprint(row[7]), "'"), row[8])
 		}
 		if opts.Sort {
 			fmt.Println("Dry run: would sort by date")

go/internal/services/banksync/sync_test.go

@@ -38,6 +38,10 @@ func TestSyncToSheets_EmptySheet(t *testing.T) {
 	if syncID, ok := rows[0][10].(string); !ok || len(syncID) != 64 {
 		t.Errorf("expected 64-char hex sync ID, got %v", rows[0][10])
 	}
+	// VS (index 7) is written as text so Sheets keeps it a string.
+	if vs, _ := rows[0][7].(string); vs != "'123" {
+		t.Errorf("expected VS written as text cell '123, got %v", rows[0][7])
+	}
 }
 
 func TestSyncToSheets_Dedup(t *testing.T) {

go/internal/services/membership/sources.go

@@ -402,7 +402,7 @@ func parseTransactionRows(rows [][]any) ([]reconcile.Transaction, error) {
 		if i < 0 || i >= len(row) {
 			return ""
 		}
-		return fmt.Sprint(row[i])
+		return sheets.CellString(row[i])
 	}
 
 	// getRaw returns row[i] without stringifying — needed for FormatDate to
@@ -425,7 +425,7 @@ func parseTransactionRows(rows [][]any) ([]reconcile.Transaction, error) {
 		amount := parseFloat(amountRaw)
 
 		var inferredAmount *float64
-		if iv := getVal(row, idxInferred); iv != "" && iv != "<nil>" {
+		if iv := getVal(row, idxInferred); iv != "" {
 			if f := parseFloat(iv); f != 0 {
 				inferredAmount = &f
 			}

go/internal/services/membership/sources_test.go

@@ -123,6 +123,8 @@ func TestLoadTransactions(t *testing.T) {
 			{"Date", "Amount", "manual fix", "Person", "Purpose", "Inferred Amount", "Sender", "VS", "Message", "Bank ID", "Sync ID"},
 			{"2026-04-01", 700.0, "", "Alice", "2026-04", "", "Alice Bank", "", "fee", "", "abc"},
 			{46147.0, 500.0, "", "", "", "", "Bob Bank", "", "platba", "", "def"}, // 46147 serial-day = 2026-05-05
+			// Numeric VS / Bank ID cells arrive as float64 and must stay plain digits.
+			{"2026-05-06", 500.0, "", "", "", "", "Carol Bank", 2609767878.0, "platba", 26123456789.0, "ghi"},
 		},
 	}}
 	s := buildSources(t, &attendance.Fake{}, sh)
@@ -131,8 +133,8 @@ func TestLoadTransactions(t *testing.T) {
 	if err != nil {
 		t.Fatal(err)
 	}
-	if len(txns) != 2 {
+	if len(txns) != 3 {
-		t.Fatalf("want 2 transactions, got %d", len(txns))
+		t.Fatalf("want 3 transactions, got %d", len(txns))
 	}
 	if txns[0].Person != "Alice" {
 		t.Errorf("txn[0].Person: want Alice, got %q", txns[0].Person)
@@ -146,6 +148,12 @@ func TestLoadTransactions(t *testing.T) {
 	if txns[1].Date != "2026-05-05" {
 		t.Errorf("txn[1].Date (numeric serial-day): want 2026-05-05, got %q", txns[1].Date)
 	}
+	if txns[2].VS != "2609767878" {
+		t.Errorf("txn[2].VS (numeric cell): want 2609767878, got %q", txns[2].VS)
+	}
+	if txns[2].BankID != "26123456789" {
+		t.Errorf("txn[2].BankID (numeric cell): want 26123456789, got %q", txns[2].BankID)
+	}
 }
 
 func TestLoadExceptions(t *testing.T) {

go/tests/fixtures/pure/calculate_fee/one_session_free_july.json

@@ -0,0 +1,12 @@
+{
+  "case": "one_session_free_july",
+  "func": "scripts.attendance.calculate_fee",
+  "captured_at": "2026-10-08",
+  "input": {
+    "attendance_count": 1,
+    "month_key": "2026-07"
+  },
+  "output": {
+    "fee": 0
+  }
+}

go/tests/fixtures/pure/calculate_fee/two_sessions_default_fallback.json

@@ -1,12 +1,12 @@
 {
   "case": "two_sessions_default_fallback",
   "func": "scripts.attendance.calculate_fee",
-  "captured_at": "2026-05-06",
+  "captured_at": "2026-10-08",
   "input": {
     "attendance_count": 2,
     "month_key": "2099-01"
   },
   "output": {
-    "fee": 700
+    "fee": 600
   }
 }

go/tests/fixtures/pure/calculate_fee/two_sessions_free_july.json

@@ -0,0 +1,12 @@
+{
+  "case": "two_sessions_free_july",
+  "func": "scripts.attendance.calculate_fee",
+  "captured_at": "2026-10-08",
+  "input": {
+    "attendance_count": 2,
+    "month_key": "2026-07"
+  },
+  "output": {
+    "fee": 0
+  }
+}

go/tests/fixtures/pure/calculate_fee/two_sessions_october.json

@@ -0,0 +1,12 @@
+{
+  "case": "two_sessions_october",
+  "func": "scripts.attendance.calculate_fee",
+  "captured_at": "2026-10-08",
+  "input": {
+    "attendance_count": 2,
+    "month_key": "2026-10"
+  },
+  "output": {
+    "fee": 600
+  }
+}

legacy/app.py

@@ -179,7 +179,9 @@ def api_adults():
         datetime.now().strftime("%Y-%m"),
         attendance_url=attendance_url, payments_url=payments_url, bank_account=BANK_ACCOUNT,
     )
-    return jsonify(_unwrap_view_model_for_api(vm))
+    out = _unwrap_view_model_for_api(vm)
+    out["months_to_show"] = MONTHS_TO_SHOW
+    return jsonify(out)
 
 @app.route("/api/juniors")
 def api_juniors():
@@ -203,7 +205,9 @@ def api_juniors():
         datetime.now().strftime("%Y-%m"),
         attendance_url=attendance_url, payments_url=payments_url, bank_account=BANK_ACCOUNT,
     )
-    return jsonify(_unwrap_view_model_for_api(vm))
+    out = _unwrap_view_model_for_api(vm)
+    out["months_to_show"] = MONTHS_TO_SHOW
+    return jsonify(out)
 
 @app.route("/api/payments")
 def api_payments():

legacy/scripts/_fixture_seeds.py

@@ -115,6 +115,15 @@ SEEDS[("calculate_fee", "two_sessions_reduced_march")] = {
 SEEDS[("calculate_fee", "two_sessions_default_fallback")] = {
     "attendance_count": 2, "month_key": "2099-01"
 }
+SEEDS[("calculate_fee", "two_sessions_free_july")] = {
+    "attendance_count": 2, "month_key": "2026-07"
+}
+SEEDS[("calculate_fee", "one_session_free_july")] = {
+    "attendance_count": 1, "month_key": "2026-07"
+}
+SEEDS[("calculate_fee", "two_sessions_october")] = {
+    "attendance_count": 2, "month_key": "2026-10"
+}
 
 
 # --- calculate_junior_fee ---

legacy/scripts/attendance.py

@@ -10,7 +10,7 @@ from config import ATTENDANCE_SHEET_ID as SHEET_ID, JUNIOR_SHEET_GID
 EXPORT_URL = f"https://docs.google.com/spreadsheets/d/{SHEET_ID}/export?format=csv&gid=0"
 JUNIOR_EXPORT_URL = f"https://docs.google.com/spreadsheets/d/{SHEET_ID}/export?format=csv&gid={JUNIOR_SHEET_GID}"
 
-ADULT_FEE_DEFAULT = 700  # CZK, for 2+ practices in a month
+ADULT_FEE_DEFAULT = 600  # CZK, for 2+ practices in a month
 ADULT_FEE_SINGLE = 200  # CZK, for exactly 1 practice in a month
 ADULT_FEE_MONTHLY_RATE = {
     "2025-09": 750,
@@ -23,8 +23,12 @@ ADULT_FEE_MONTHLY_RATE = {
     "2026-04": 700,
     "2026-05": 450,
     "2026-06": 600,
-    "2026-07": 600,
+    "2026-07": 0,
-    "2026-08": 600,
+    "2026-08": 0,
+    "2026-09": 600,
+    "2026-10": 600,
+    "2026-11": 600,
+    "2026-12": 600,
 }
 
 JUNIOR_FEE_DEFAULT = 500  # CZK for 2+ practices
@@ -91,12 +95,13 @@ def group_by_month(dates: list[tuple[int, datetime]], merged_months: dict[str, s
 
 
 def calculate_fee(attendance_count: int, month_key: str) -> int:
-    """Apply fee rules: 0 → 0, 1 → 200, 2+ → configured rate (default 750)."""
+    """Apply fee rules: 0 → 0, 1 → 200 (capped at the month's rate), 2+ → configured rate (default 600)."""
     if attendance_count == 0:
         return 0
+    rate = ADULT_FEE_MONTHLY_RATE.get(month_key, ADULT_FEE_DEFAULT)
     if attendance_count == 1:
-        return ADULT_FEE_SINGLE
+        return min(ADULT_FEE_SINGLE, rate)
-    return ADULT_FEE_MONTHLY_RATE.get(month_key, ADULT_FEE_DEFAULT)
+    return rate
 
 
 def calculate_junior_fee(attendance_count: int, month_key: str) -> str | int:

legacy/scripts/sync_fio_to_sheets.py

@@ -59,6 +59,16 @@ def get_sheets_service(credentials_path: str):
     return _SHEETS_SERVICE
 
 
+def as_text_cell(value) -> str:
+    """Mark a value to be stored as text when written with USER_ENTERED.
+
+    A leading apostrophe stops Sheets from parsing digits as a number (which
+    would drop leading zeros); it is not part of the stored value. Empty stays empty.
+    """
+    s = "" if value is None else str(value)
+    return f"'{s}" if s else ""
+
+
 def generate_sync_id(tx: dict) -> str:
     """Generate a unique SHA-256 hash for a transaction.
     
@@ -209,7 +219,7 @@ def sync_to_sheets(
                 "", # Purpose
                 "", # Inferred Amount
                 tx.get("sender", ""),
-                tx.get("vs", ""),
+                as_text_cell(tx.get("vs", "")),
                 tx.get("message", ""),
                 tx.get("bank_id", ""),
                 sync_id,

legacy/tests/test_app.py

@@ -6,7 +6,7 @@ from app import app
 EXPECTED_ADULTS_KEYS = {
     "months", "raw_months", "results", "totals", "member_data", "month_labels",
     "raw_payments", "credits", "debts", "unmatched", "attendance_url",
-    "payments_url", "bank_account", "current_month",
+    "payments_url", "bank_account", "current_month", "months_to_show",
 }
 EXPECTED_JUNIORS_KEYS = EXPECTED_ADULTS_KEYS
 EXPECTED_PAYMENTS_KEYS = {"grouped_payments", "sorted_people", "attendance_url", "payments_url"}
@@ -139,6 +139,7 @@ class TestWebApp(unittest.TestCase):
         self.assertIsInstance(data['member_data'], dict)
         self.assertIsInstance(data['month_labels'], dict)
         self.assertIsInstance(data['raw_payments'], dict)
+        self.assertIsInstance(data['months_to_show'], int)
 
     @patch('app.get_cached_data', side_effect=_bypass_cache)
     @patch('app.fetch_sheet_data')
@@ -166,6 +167,7 @@ class TestWebApp(unittest.TestCase):
         self.assertIsInstance(data['member_data'], dict)
         self.assertIsInstance(data['month_labels'], dict)
         self.assertIsInstance(data['raw_payments'], dict)
+        self.assertIsInstance(data['months_to_show'], int)
 
     @patch('app.get_cached_data', side_effect=_bypass_cache)
     @patch('app.fetch_sheet_data')

legacy/tests/test_match_payments.py

@@ -1,6 +1,7 @@
 import unittest
+from unittest.mock import MagicMock, patch
 
-from scripts.match_payments import canonical_member_key, reconcile
+from scripts.match_payments import canonical_member_key, fetch_sheet_data, reconcile
 
 
 class TestCanonicalMemberKey(unittest.TestCase):
@@ -67,3 +68,23 @@ class TestReconcileTolerantPersonMatching(unittest.TestCase):
 
 if __name__ == "__main__":
     unittest.main()
+
+
+class TestFetchSheetDataVS(unittest.TestCase):
+    """Numeric VS cells arrive as floats (UNFORMATTED_VALUE) and must stay plain digit strings."""
+
+    def _fetch(self, vs_cell):
+        service = MagicMock()
+        service.spreadsheets().values().get().execute.return_value = {"values": [
+            ["Date", "Amount", "manual fix", "Person", "Purpose", "Inferred Amount",
+             "Sender", "VS", "Message", "Bank ID", "Sync ID"],
+            ["2026-04-15", 750, "", "", "", "", "Test Sender", vs_cell, "fee", "", "abc"],
+        ]}
+        with patch("scripts.match_payments.get_sheets_service", return_value=service):
+            return fetch_sheet_data("sheet-id", "creds.json")
+
+    def test_numeric_vs_is_plain_digit_string(self):
+        self.assertEqual(self._fetch(2609767878.0)[0]["vs"], "2609767878")
+
+    def test_string_vs_is_kept(self):
+        self.assertEqual(self._fetch("0308")[0]["vs"], "0308")

legacy/tests/test_sync_fio.py

@@ -0,0 +1,33 @@
+import contextlib
+import io
+import unittest
+from unittest.mock import MagicMock, patch
+
+from scripts.sync_fio_to_sheets import COLUMN_LABELS, as_text_cell, sync_to_sheets
+
+
+class TestAsTextCell(unittest.TestCase):
+    def test_digits_get_text_marker(self):
+        self.assertEqual(as_text_cell("0308"), "'0308")
+        self.assertEqual(as_text_cell(123), "'123")
+
+    def test_empty_stays_empty(self):
+        self.assertEqual(as_text_cell(""), "")
+        self.assertEqual(as_text_cell(None), "")
+
+
+class TestSyncWritesVSAsText(unittest.TestCase):
+    def test_appended_row_has_text_vs(self):
+        service = MagicMock()
+        sheet = service.spreadsheets.return_value
+        sheet.values.return_value.get.return_value.execute.return_value = {"values": [COLUMN_LABELS]}
+        tx = {"date": "2026-04-10", "amount": 750.0, "sender": "Test Sender",
+              "vs": "0308", "message": "fee", "bank_id": "111"}
+        with patch("scripts.sync_fio_to_sheets.get_sheets_service", return_value=service), \
+             patch("scripts.sync_fio_to_sheets.fetch_transactions_all", return_value=[tx]), \
+             contextlib.redirect_stdout(io.StringIO()):
+            sync_to_sheets("sheet-id", "creds.json", days=30)
+
+        body = sheet.values.return_value.append.call_args.kwargs["body"]
+        self.assertEqual(len(body["values"]), 1)
+        self.assertEqual(body["values"][0][7], "'0308")