chemenu/docs/reference/configuration.md

# Configuration

The environment variables `wikitool` reads and the two tiered settings files an operator may create at
the root of an instance. None of them is needed for an instance to work: an instance installed from a
release runs against the origin's public release feed with no configuration at all.

Every setting of a feature - telemetry, the publish allowlist, the task tracker, the MCP `submit`
limits - is a section of those two files, and the shape of each section - its fields, their tier, what
an absent or a malformed section means, an example - is generated from the record `wikitool` itself
reads it with, so it cannot describe a field the tool does not take. What a setting does around it is
written by hand.

Three more files at the root are written by `wikitool` and never by hand: `.wikitool-release.json`,
`.wikitool-kb.json` and `.wikitool-tools.json` ([AGENTS.md invariant 1](../../AGENTS.md#invariants)).
The last one has its own section [below](#tool-paths), because the preflight that writes it is
something you run.

<!-- wikitool:toc -->
## Contents

- [Environment variables](#environment-variables)
- [Tool paths](#tool-paths)
- [Tiered settings](#tiered-settings)
- [Telemetry](#telemetry)
- [Allowed push URLs](#allowed-push-urls)
- [Task tracker](#task-tracker)
  - [Super Productivity](#super-productivity)
  - [CalDAV](#caldav)
  - [Profiles](#profiles)
- [MCP submissions](#mcp-submissions)
- [Site handlers](#site-handlers)
- [Files of earlier versions](#files-of-earlier-versions)
<!-- /wikitool:toc -->

## Environment variables

| Variable | Purpose | Fallback |
|----------|---------|----------|
| `WIKI_AUTHOR` | Overrides the author name of new source pages | `git config user.name`. Without either, `new` stops with an `ERROR` |
| `WIKITOOL_SESSION_ID` | Scopes the Iteration Budget Gate to a task rather than a terminal, and names the directory a trace lands in | A session variable the harness sets itself, where one is known (for example `CLAUDE_CODE_SESSION_ID`), else the parent process id ([instructions/session-setup.md](../../instructions/session-setup.md)) |
| `WIKITOOL_UPDATE_URL` | The release feed `version check`, `version notes` and `dist upgrade --latest` ask | The value in `.wikitool-release.json`, else the origin's feed |
| `WIKITOOL_UPDATE_TOKEN` | A Gitea token for the release feed, sent only to downloads on the feed's own host | None. Not needed against the origin, only against a feed in a private repository |
| `WIKITOOL_TASKS_CONFIG` | Path to a tracker profile that `task`, `review` and `doctor` read instead of the `tasks`, `superproductivity` and `caldav` sections of the settings, for running one checkout against several trackers in turn ([below](#profiles)) | The sections in `wikitool.json` and `.wikitool-local.json`. A path to a file that does not exist is an error, never "no tracker configured" |
| `WIKITOOL_SECRET_<NAME>` | The value behind a settings reference `{"ref": "<name>"}`, for CI and containers - `<NAME>` is the name upper-cased | The secrets file in the user's configuration directory ([below](#tiered-settings)) |
| `CHEMENU_ROOT` | Which corpus the package works on, for a caller outside the checkout itself | The checkout the package sits in. `tools/wikitool` behaves the same without it |
| `WIKI_TRACE` | `0`/`1` turns telemetry off or on, beating both the default and the `telemetry` section | The installation-form default ([below](#telemetry)) |
| `WIKI_TRACE_DIR` | Writes traces somewhere other than `reports/telemetry/` | `reports/telemetry/` |
| `WIKI_TRACE_CONTENT` | `0` keeps only lengths and digests of prompts and replies instead of their text | Text is kept |
| `WIKI_TRACE_MAX_CONTENT` | Per-attribute content cap in characters | 60 KiB |
| `WIKI_TRACE_MAX_SESSION_BYTES` | Byte cap per session trace; beats the section's `max_session_bytes` | 5 MiB |
| `WIKI_TRACE_KEEP_SESSIONS` | How many session directories retention keeps; beats the section's `keep_sessions` | 250 |

## Tool paths

**The preflight writes this file, not you.** `.wikitool-tools.json` at the root holds the absolute
paths of Python, git and ripgrep, as the preflight found them on this machine - and of the
1Password CLI `op` when it is installed. `op` is optional: the preflight records it when it finds
it, reports `ABSENT` when it does not, and never asks for it. Only an `op://` reference in the
[tiered settings](#tiered-settings) needs it. `wikitool` starts git
and rg from there instead of from `PATH`. It is per checkout and gitignored, because a path on one
machine says nothing about the next.

If the file is missing or incomplete, `tools/wikitool` does not start (exit 42) and names the
preflight. If a tool sits somewhere the preflight does not look, name it:
`tools/preflight.sh --set rg=<path>`, or in PowerShell
`pwsh -NoProfile -ExecutionPolicy Bypass -File tools/preflight.ps1 --set rg=<path>`. Never edit the
file by hand. `doctor` reports under `tool-paths` whether every path still works.

## Tiered settings

Two files at the root hold the settings of the features that read them this way, and every field
declares the tier it belongs to:

| Tier | File | Holds |
|------|------|-------|
| `instance` | `wikitool.json`, committed | What belongs to the corpus and is the same in every clone |
| `checkout` | `.wikitool-local.json`, gitignored | What is true only for this clone on this machine |
| `secret` | neither | Tokens and passwords - both files hold only a reference |

Each file is a JSON object of sections, one per feature, beside two keys of its own:

```json
{
  "schema": 1,
  "instance_id": "6f1c0e52-3d1b-4b8e-9a51-2f0e7d1c9b44",
  "<section>": {"<field>": "<value>"}
}
```

`instance_id` sits in `wikitool.json` only. The first `wikitool config set` creates the file and
the id; the id names the directory of the secrets file below. The sections are [telemetry](#telemetry),
[remotes](#allowed-push-urls), [tasks, superproductivity and caldav](#task-tracker) and
[upload](#mcp-submissions) and [sites](#site-handlers). `config set` names the sections it knows, and `doctor` reports a
section it does not read as a `WARN`.

**One place per value.** A value in the file its tier does not name is an error naming the file,
the key and the right tier - never an override. The same holds for a key set in both files.

**References.** A field of tier `secret` takes only a reference; a field marked private - a host
name, an internal URL - takes a plain value in `.wikitool-local.json` or a reference in either
file. No other field takes one.

| Reference | Resolves through |
|-----------|------------------|
| `{"ref": "<name>"}` - lower-case letters, digits and single `_` | `WIKITOOL_SECRET_<NAME>`, else the key `<name>` in the secrets file |
| `{"ref": "op://<vault>/<item>/<field>"}` | `op read`, the 1Password CLI the preflight recorded |

The secrets file is `~/.config/chemenu/<instance_id>/secrets.json` (`$XDG_CONFIG_HOME` instead of
`~/.config` when it is set; `%APPDATA%\chemenu\<instance_id>\secrets.json` on Windows), a JSON object of
names to strings. Outside Windows it must be readable by its owner only (`chmod 600`); a file
others can read is refused.

A reference is resolved when a command asks for that value, never when the files are read. A name
nobody provides, an `op` that is not installed, or an item 1Password does not have ends the command
with exit 1; a 1Password that is locked, signed out or waiting for an approval ends it with exit 42,
for a human to unlock. Setting 1Password up: [use-1password-for-settings.md](../how-to/use-1password-for-settings.md).

**Never in the committed file:** a field that names a program to run or affects a gate - not even
as a reference. `config set` does not write such a field either (exit 42); the user edits
`.wikitool-local.json` by hand, and `doctor` checks it afterwards. The fields marked `gate` in the
tables below are these: the publish allowlist and the upload limits.

`wikitool doctor` reports one line per tier - `settings-instance`, `settings-checkout`,
`settings-secrets` - and for the references only whether they resolve. `docs verify` holds a
committed `wikitool.json` to the placement rules above, a plain secret or private value above
all. Neither file ships with `dist export`. Why the tiers exist, and what keeping secrets out of
the tree does not protect against: [configuration-tiers.md](../explanation/configuration-tiers.md).

## Telemetry

**Telemetry is off in an instance.** Every instance carries the `.wikitool-release.json` of its
release, and that is how `chemenu.telemetry.policy` recognises that nobody asked for telemetry. The
same holds for every further clone of the instance, because the file is committed with the first
publish. Only a clone of the origin repository, used to develop the stack, has no stamp. There the
traces are the instrument the stack measures itself with, and they are **on**.

To turn the default around, add a `telemetry` section to `.wikitool-local.json`, by hand or with
`wikitool config set telemetry.enabled true`. The consent to write prompts to this disk belongs to
the checkout, so the section has no instance-tier field and no gate.

<!-- wikitool:reference-config-telemetry -->
| Field | Tier | Type | Required | Default | Description |
|-------|------|------|----------|---------|-------------|
| `enabled` | checkout | boolean | no | the installation-form default | Telemetry on or off. `WIKI_TRACE` beats it in both directions. Any other value is read by its truthiness, so `"no"` means on. |
| `max_session_bytes` | checkout | positive integer | no | `5242880` | Byte cap per session trace. `WIKI_TRACE_MAX_SESSION_BYTES` beats it. A number written as a string is accepted. |
| `keep_sessions` | checkout | positive integer | no | `250` | How many session directories retention keeps. `WIKI_TRACE_KEEP_SESSIONS` beats it. A number written as a string is accepted. |

- **Absent:** The installation-form default applies: on in a clone of the origin repository, off in an instance.
- **Malformed:** The hook that reads it never fails on it: a value it cannot use counts as absent, and an unreadable `.wikitool-local.json` as an absent section. `doctor` reports each such deviation as a `WARN` under `telemetry`, naming the field.

Example:

```json
{
  "telemetry": {
    "enabled": true,
    "max_session_bytes": 5242880,
    "keep_sessions": 250
  }
}
```
<!-- /wikitool:reference-config-telemetry -->

`wikitool doctor` reports the current state: on or off, why, and how much has been recorded against
both caps. What the caps do and what never reaches a trace:
[telemetry-and-evaluation.md](../explanation/telemetry-and-evaluation.md).

The telemetry hook runs on every tool call and stays silent, so it reads only this section, leniently,
and never exits 42: a `.wikitool-telemetry.json` left over from an earlier version is ignored there
([below](#files-of-earlier-versions)).

## Allowed push URLs

The `remotes` section of `.wikitool-local.json` restricts where `publish` may push.

<!-- wikitool:reference-config-remotes -->
| Field | Tier | Type | Required | Default | Description |
|-------|------|------|----------|---------|-------------|
| `allowed_push_urls` | checkout, gate | array of strings | yes | - | The push URLs `publish` may write to, compared with the URL the remote resolves to for a push - not with its name. An empty list allows no push at all. |

- **Absent:** Any remote is allowed; the Publish-Remote Gate does not apply.
- **Malformed:** `publish` stops with an error before committing anything. A broken section is never read as "no restriction".

Example:

```json
{
  "remotes": {
    "allowed_push_urls": [
      "<url>"
    ]
  }
}
```
<!-- /wikitool:reference-config-remotes -->

With the section, `publish` refuses with exit 42 (the Publish-Remote Gate) before pushing to a URL not
on the list. Only you edit it: the field is marked `gate`, so `config set` exits 42 for it. The gate
has no token and no flag, and an agent that edits the list to get past a refusal is opening a gate on
its own initiative.

## Task tracker

**Optional.** The weekly review (`tools/wikitool review`, skill `gtd-weekly-review`) checks the
project pages under `kb/gtd/` against a task tracker. Which tracker that is, and its connection
details, are three sections: `tasks` (which provider, the review's thresholds), and the section of the
provider chosen, `superproductivity` or `caldav`. What is the same in every clone - the provider, the
thresholds, the list names - sits in `wikitool.json`; the host, the user name and the folder this
machine uses in `.wikitool-local.json`; a token or password is a reference to a secret, never a value.

<!-- wikitool:reference-config-tasks -->
| Field | Tier | Type | Required | Default | Description |
|-------|------|------|----------|---------|-------------|
| `provider` | instance | string | yes | - | Which adapter the review goes through. |
| `stalled_waiting_days` | instance | positive integer | yes | - | A waiting-for item older than this many days counts as overdue. A number written as a string is accepted. |
| `unpaged_project_weeks` | instance | positive integer | yes | - | A tracker project with no `kb/` page is reported once it is older than this many weeks. A number written as a string is accepted. |
| `someday_stale_months` | instance | positive integer | yes | - | A someday/maybe item untouched for this many months counts as stale. A number written as a string is accepted. |

- **Absent:** No tracker is configured - a valid state. The weekly review has nothing to check against.
- **Malformed:** An error, and `doctor` reports `FAIL`. A broken section is never read as "no tracker configured".

Example:

```json
{
  "tasks": {
    "provider": "superproductivity",
    "stalled_waiting_days": 14,
    "unpaged_project_weeks": 3,
    "someday_stale_months": 5
  }
}
```
<!-- /wikitool:reference-config-tasks -->

The thresholds are configuration, not schema. A value the provider cannot supply at all - a
waiting item with no follow-up date, a tracker project with no creation date - is not skipped silently
but reported as its own finding (`waiting_no_follow_up`/`project_age_unknown`).

### Super Productivity

<!-- wikitool:reference-config-superproductivity -->
| Field | Tier | Type | Required | Default | Description |
|-------|------|------|----------|---------|-------------|
| `access` | instance | string | yes | - | Which way in: `api`, the local REST API (reads the current state and carries the write path), or `snapshot`, the newest backup snapshot (read-only). |
| `api_base_url` | checkout, private | string | no | `"http://127.0.0.1:3876"` | With `access: "api"`: where the app's REST API listens. An empty value means the default. |
| `api_token` | secret | string | no | - | With `access: "api"`, required: the token from the app's settings. Only ever a reference. |
| `backups_dir` | checkout | string | no | - | With `access: "snapshot"`, required: the directory the app writes its backup snapshots to; `~` is expanded. |

- **Absent:** Read only when `tasks.provider` is `superproductivity`.
- **Malformed:** An error when it is read: a field of the other access path beside `access`, or a missing `api_token` or `backups_dir`, stops the command with exit 1.

Examples:

```json
{
  "superproductivity": {
    "access": "api",
    "api_base_url": "http://127.0.0.1:3876",
    "api_token": {
      "ref": "sp_token"
    }
  }
}
```

```json
{
  "superproductivity": {
    "access": "snapshot",
    "backups_dir": "~/.config/superProductivity/backups"
  }
}
```
<!-- /wikitool:reference-config-superproductivity -->

`access` is **mandatory and has no fallback**. The fields of the other access path are an error, not ignored: a `backups_dir` beside `access: "api"` stops the command with exit 1, as does an `api_token` missing from it. It chooses between two mutually exclusive ways in:

- **`access: "snapshot"`** for an instance run headless: it reads only the newest backup snapshot
  under `backups_dir`. That works without the app running, but only reads. The tracker cannot be
  written from there.

- **`access: "api"`** for a desktop instance: it talks only to the local REST API. That answers only
  while the app runs, but it gives the current state and carries the write path. `api_token` is
  required (as a reference), because every endpoint except `GET /health` demands `Authorization: Bearer <token>`.

What can write:

- `tools/wikitool new project` creates a tracker project of the same name only with `access: "api"`,
  and even there not automatically. The command stops (exit 42) and asks a human to create it, then
  continues with `--resume`.
- `tools/wikitool task new` creates a single item without a `kb/` page.
- `tools/wikitool task close --id` marks an item done. It never deletes one.

With `access: "snapshot"`, all three refuse completely with exit 1, because the tracker is read-only
from there. `tools/wikitool task list --project` only reads, so it answers with either `access`.

### CalDAV

<!-- wikitool:reference-config-caldav -->
| Field | Tier | Type | Required | Default | Description |
|-------|------|------|----------|---------|-------------|
| `url` | checkout, private | string | yes, not empty | - | The account's CalDAV calendar home set. A trailing `/` is added when missing. |
| `username` | checkout, private | string | yes, not empty | - | The login name, which can differ from the user id in the URL. |
| `app_password` | secret | string | yes, not empty | - | An app password is recommended over the account password. Only ever a reference. |
| `inbox_list` | instance | string | yes, not empty | - | The name of the one inbox list. |
| `someday_list` | instance | string | yes, not empty | - | The name of the one someday/maybe list. |
| `exclude_lists` | instance | array of strings | no | `[]` | Existing plain task lists that are not projects. |

- **Absent:** Read only when `tasks.provider` is `caldav`.

Example:

```json
{
  "caldav": {
    "url": {
      "ref": "op://Chemenu/caldav/url"
    },
    "username": "<login>",
    "app_password": {
      "ref": "caldav_app_password"
    },
    "inbox_list": "Inbox",
    "someday_list": "Someday",
    "exclude_lists": [
      "..."
    ]
  }
}
```
<!-- /wikitool:reference-config-caldav -->

`caldav` is the standards-based second adapter (RFC 4791/5545). It is verified against Nextcloud
Tasks, with iOS *Reminders* as the mobile client, and built for that split: tick items off on the
phone, maintain them at the desk. Unlike Super Productivity, there is only one way in. CalDAV is
always a network access, so no `access` field is needed.

- `url` may be an alias - Nextcloud accepts a short name there - because every later address comes
  only from the `href`s the server returns, never from this URL joined with a name.
- `inbox_list` and `someday_list` name the two fixed lists, exactly one of each per instance.
- A list with a `VEVENT` component never counts as a project, so `exclude_lists` is needed only for
  plain task lists.

A project is a list whose only supported component is `VTODO`. `tools/wikitool new project` creates
it automatically with `MKCALENDAR` - without asking, unlike Super Productivity, because CalDAV has a
real create command for lists. The uniqueness check runs against **every** list in the account,
including excluded lists, the inbox, someday and mixed calendars. If a new name collides with any of
them, nothing is created and the collision is named. Renaming the existing list in Nextcloud stays a
manual step.

`task new` and `task close` work without restriction on `caldav`, which has no read-only mode like
`access: "snapshot"`. When ticking an item off, `task close` changes only `STATUS`, `COMPLETED`,
`PERCENT-COMPLETE`, `LAST-MODIFIED` and `DTSTAMP` on the existing `.ics` resource. Every other
property, including an unknown `X-` property or an alarm, is kept unchanged. A resource that changed
since it was read (an ETag conflict) is not written, and the command stops with exit 1. Nothing is
ever deleted. The lists of finished projects stay after archiving, because the adapter never deletes
a list. Remove them by hand in Nextcloud when you want to.

### Profiles

`WIKITOOL_TASKS_CONFIG` points at a profile: a file in the format of `.wikitool-local.json` that holds
only the sections `tasks`, `superproductivity` and `caldav` (and `schema`, and `live_test_version`
for the live suite). While it is set, `task`, `review` and `doctor` read those three sections from the
profile instead of from `wikitool.json` and `.wikitool-local.json`, so one checkout can be run against
several trackers in turn. A profile is checked like the local file, except that a plain instance-tier
value is allowed in it; a secret is a reference there too, never a value. The live suite takes its
throwaway tokens from `WIKITOOL_SECRET_<NAME>`.

## MCP submissions

The `upload` section of `.wikitool-local.json` in the served corpus turns on the MCP read server's
optional `submit` tool. What the authentication in front of the server has to guarantee before you
create it is in
[Set up the MCP read server](../how-to/set-up-the-mcp-server.md#optional-the-submit-path). Every field
is marked `gate`: the limits are the user's to set by hand, and `config set` exits 42 for them.

<!-- wikitool:reference-config-upload -->
| Field | Tier | Type | Required | Default | Description |
|-------|------|------|----------|---------|-------------|
| `identity_header` | checkout, gate | string | no | `"X-Forwarded-User"` | The request header the authenticating middleware sets to the submitter's identity on every request. An empty value means the default. |
| `max_bytes` | checkout, gate | positive integer | yes | - | Largest single submission, in bytes. A number written as a string is accepted. |
| `allowed_extensions` | checkout, gate | array of strings | yes | - | The file extensions `submit` accepts, each starting with `.`. Compared case-insensitively. Entries are read as strings and lower-cased; duplicates collapse. |
| `quota_submissions_per_day` | checkout, gate | positive integer | yes | - | Submissions one submitter may make over any rolling 24 hours. A number written as a string is accepted. |
| `quota_bytes_per_day` | checkout, gate | positive integer | yes | - | Bytes one submitter may submit over any rolling 24 hours. A number written as a string is accepted. |

- **Absent:** The `submit` tool is not registered: the write path does not exist.
- **Malformed:** An error. The MCP server does not start and `doctor` reports `FAIL`. A broken section is never read as "no limits".

Example:

```json
{
  "upload": {
    "identity_header": "X-Forwarded-User",
    "max_bytes": 10485760,
    "allowed_extensions": [
      ".md",
      ".pdf"
    ],
    "quota_submissions_per_day": 20,
    "quota_bytes_per_day": 52428800
  }
}
```
<!-- /wikitool:reference-config-upload -->

Size and quota are your deployment's decision, not defaults worth copying blindly.

## Site handlers

`tools/wikitool raw fetch` knows how some websites serve their pages. For a URL of such a website a
*site handler* fetches the page in the website's standard form, leaves the page furniture out of the
derived text and prints hints about the page as `CHECK` lines; today there are two, both for
`learn.microsoft.com`: `learn-microsoft` for every page of the host and
`learn-microsoft-powershell-module` for a PowerShell module's overview page, which adds a hint
naming the cmdlet pages it lists. Handlers are JSON files: the stack's, and the instance's own under `sites/`
(see [How to write a site handler](../how-to/write-a-site-handler.md)).
The `sites` section is what the instance decides about the handlers, and it is optional: without it every
handler applies, in the locale `en-us`.

- `disabled` switches handlers off by name. A page of that website is then handled as any other:
  fetched under the URL as typed, with its page furniture in the derived text. A name no handler has
  is an error, so a typo cannot leave a handler on. Switching off a special handler leaves the
  general one of the same website in force.
- `locale` is the language segment a handler for a multi-language website puts into the URL it
  fetches. The header of the derived text keeps the URL as typed under `requested_url`.
- `notes` adds hint lines of the instance's own, printed after a fetch or an `--html` derivation of
  a page of that host, whether or not a handler exists for it. An entry names a `host` (exact, lower
  case), optionally a `path` (a regular expression matched against the start of the URL path, after
  the standard form was applied) and one to three single-line `lines`. A host and path pattern appears
  once; an entry whose `path` is left out applies to the whole host. A line is plain text and is
  output as it is, so it is for a reminder to the reader of the capture, never for an instruction
  the tool should carry out.

<!-- wikitool:reference-config-sites -->
| Field | Tier | Type | Required | Default | Description |
|-------|------|------|----------|---------|-------------|
| `disabled` | instance | array of strings | no | `[]` | The names of the site handlers that do not apply. `raw fetch` then treats a page of that website as it does any other. A name no handler has is an error when `raw fetch` reads the section, so a typo cannot leave a handler on. |
| `locale` | instance | string | no | `"en-us"` | The locale a handler for a multi-language website fetches, in the website's own spelling and lower case. An empty value means the default. |
| `notes` | instance | array of objects | no | `[]` | Hint lines of the instance's own, printed as `CHECK` lines after a fetch or an `--html` derivation of a page of that host. Each entry has `host` (exact, lower case), an optional `path` (a regular expression matched against the start of the URL path) and `lines` (one to 3 single-line strings of at most 300 characters). A host and path pattern appears once. |

- **Absent:** Every handler applies, with the locale `en-us` and no further hint lines.
- **Malformed:** An error when `raw fetch` reads it: it stops with exit 1 before fetching anything. A broken section is never read as "no handlers".

Example:

```json
{
  "sites": {
    "disabled": [
      "learn-microsoft-powershell-module"
    ],
    "locale": "en-us",
    "notes": [
      {
        "host": "learn.microsoft.com",
        "path": "^/[a-z-]+/azure/",
        "lines": [
          "Check the Azure retirement notice at the top of the page."
        ]
      }
    ]
  }
}
```
<!-- /wikitool:reference-config-sites -->

All three fields are instance-tier: what a website needs cleaned is the same in every clone, and none
of them names a program or opens a gate. A section that does not read correctly stops `raw fetch`
with exit 1 before it fetches anything.

## Files of earlier versions

Until version 10 every feature above had a file of its own at the root: `.wikitool-telemetry.json`,
`.wikitool-remotes.json`, `.wikitool-upload.json` and `.wikitool-tasks.json`. Nothing reads them any
more. A command that needs the setting such a file held stops with exit 42 and names
`tools/wikitool config migrate`, `doctor` reports each one as a `FAIL`, and only the telemetry hook
ignores it. `config migrate` moves the content into the sections above, each value into the file its
tier names and each secret into the secrets file, and then removes the old files; it is run once per
checkout. `.wikitool-tools.json` is not among them and stays. The migration step for an instance is
[10.0.0-settings-tiers.md](../../instructions/migrations/10.0.0-settings-tiers.md).