docs/architecture/config-schema.md

@@ -0,0 +1,103 @@
+---
+type: api
+title: Config Schema
+description: Required/optional environment variables, validation rules, and the typed Config dataclass returned by tenbackward.config.load_config.
+tags: [config, env, schema]
+timestamp: 2026-08-04T17:51:00Z
+---
+
+# Purpose
+
+`tenbackward.config.load_config()` is the single boundary that turns
+process environment + optional `.env` file into a typed `Config`
+dataclass. Job 1083 changes every variable that ships in
+`.env.example` so that it is **explicitly required** at every layer
+(`entrypoint.sh`, `config.validate_config`, and the rendered cron).
+
+# Required Environment Variables
+
+All eight of these must be present and non-empty in the process
+environment for the container to boot.
+
+| Key                  | Purpose                                                | Validation                                                       |
+|----------------------|--------------------------------------------------------|------------------------------------------------------------------|
+| `MASTODON_BASE_URL`  | Mastodon instance to post against.                     | Must parse with `http` or `https` scheme and a non-empty netloc. |
+| `MASTODON_ACCESS_TOKEN` | OAuth token used by the future Mastodon.py client.   | Required string.                                                 |
+| `VISIBILITY`         | Default post visibility.                               | Must be `public` or `unlisted`.                                  |
+| `SITE_URL`           | Source blog URL (used by the future clone step).       | Must parse with `http` or `https` scheme and a non-empty netloc. |
+| `HASHTAGS`           | Comma-separated hashtags appended to every throwback.   | Required string (formatting handled by the future poster).       |
+| `THROWNBACK_PREFIX`  | Per-post title prefix (default: `Throwback:`).         | Required string.                                                 |
+| `MAX_RETRIES`        | Number of additional retries after the first attempt.  | Non-negative integer (parsed by `_parse_max_retries`).           |
+| `RUN_AT`             | Daily fire time for the cron entry.                    | `HH:MM` 24-hour format.                                          |
+| `TZ`                 | IANA timezone used by cron + the container clock.      | Must resolve via `zoneinfo.ZoneInfo`.                            |
+
+> **Note** — All nine keys are required since Job 1083. The previously
+> optional `MASTODON_VISIBILITY`, `THROWBACK_PREFIX`, and `RETRY_COUNT`
+> were promoted to first-class citizens and renamed to `VISIBILITY`,
+> `THROWNBACK_PREFIX`, and `MAX_RETRIES`.
+
+# Defaults
+
+`DEFAULTS` in `config.py` provides fallback strings that `apply_defaults`
+fills into the merged map **before** validation runs:
+
+| Default key           | Default value     |
+|-----------------------|-------------------|
+| `VISIBILITY`          | `public`          |
+| `THROWNBACK_PREFIX`   | `Throwback:`      |
+| `MAX_RETRIES`         | `3`               |
+| `TZ`                  | `Europe/Berlin`   |
+| `RUN_AT`              | `09:00`           |
+
+Because every required key carries a default, a freshly-initialised
+container can still boot to validate the scaffold, but the operator
+must supply `MASTODON_BASE_URL` and `MASTODON_ACCESS_TOKEN` (and
+ideally `SITE_URL`) to make a real run.
+
+# `Config` Dataclass
+
+| Field                   | Type      | Source                                       |
+|-------------------------|-----------|----------------------------------------------|
+| `mastodon_base_url`     | `str`     | `MASTODON_BASE_URL`                          |
+| `mastodon_access_token` | `str`     | `MASTODON_ACCESS_TOKEN`                      |
+| `visibility`            | `str`     | `VISIBILITY`                                 |
+| `site_url`              | `str`     | `SITE_URL`                                   |
+| `hashtags`              | `str`     | `HASHTAGS`                                   |
+| `throwback_prefix`      | `str`     | `THROWNBACK_PREFIX`                          |
+| `max_retries`           | `int`     | `MAX_RETRIES` (parsed as non-negative int)   |
+| `run_at`                | `str`     | `RUN_AT`                                     |
+| `tz`                    | `str`     | `TZ`                                         |
+| `data_dir`              | `Path`    | Constant: `Path("/app/data")`                |
+
+# Validation Behaviour
+
+`validate_config(values)` collects all failures before raising so the
+operator sees every problem at once. A single `ConfigError` lists each
+problem joined with `"; "`. Validation covers:
+
+* Required keys are non-empty.
+* `RUN_AT` parses as `HH:MM`.
+* `MASTODON_BASE_URL` and `SITE_URL` parse via `urllib.parse.urlparse`
+  with an `http`/`https` scheme and a non-empty `netloc`.
+* `VISIBILITY` is one of `{"public", "unlisted"}` (`ALLOWED_VISIBILITY`).
+* `TZ` resolves via `zoneinfo.ZoneInfo`.
+* `MAX_RETRIES` parses as a non-negative integer (rejects bools).
+
+# Exit Codes
+
+| Code | Source                                  | Meaning                                                              |
+|------|-----------------------------------------|----------------------------------------------------------------------|
+| `1`  | `main.main()` (retry budget exhausted)  | Pipeline failed on every attempt after `MAX_RETRIES + 1` tries.     |
+| `2`  | `main.main()` (`ConfigError`)           | Configuration was present but invalid; details are logged.           |
+
+# Citations
+
+* [1] `src/tenbackward/config.py` — `REQUIRED_KEYS`, `DEFAULTS`, `ALLOWED_VISIBILITY`, `Config`, `load_config`, `validate_config`.
+* [2] `.env.example` — canonical env-var list.
+* [3] `entrypoint.sh` — shell-side mirror of the required keys.
+
+# Related
+
+* [System Architecture](/architecture/system-overview.md)
+* [Logging & Run Summary](/architecture/logging.md)
+* [Environment Variable Setup](/operations/environment-setup.md)

docs/architecture/logging.md

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+---
+type: architecture
+title: Logging & Run Summary
+description: Structured JSON logging in 10Backward — JsonFormatter, secret redaction, and the startup / error / run_complete event helpers.
+tags: [logging, observability, json]
+timestamp: 2026-08-04T17:51:00Z
+---
+
+# Purpose
+
+`tenbackward.logging_setup` replaces the scaffold-era `basicConfig`
+text logger with a **single-line JSON formatter** that downstream
+log shippers can index. It also owns the three helpers the runner
+uses to record structured events: `log_startup`, `log_error`,
+`log_run_summary`.
+
+# JsonFormatter
+
+`JsonFormatter.format(record)` returns one JSON object per log record:
+
+| Key        | Source                                                              |
+|------------|---------------------------------------------------------------------|
+| `ts`       | UTC `datetime.fromtimestamp(record.created).isoformat()`.           |
+| `level`    | `record.levelname` (e.g. `INFO`, `ERROR`).                          |
+| `logger`   | `record.name` (always `tenbackward`).                               |
+| `message`  | `record.getMessage()`.                                              |
+| _extras_   | Any keyword passed via `logging.info(..., extra={...})` that is not a reserved `LogRecord` attribute and whose key is **not** in `_SECRET_KEYS`. |
+| `exc_type` | When `record.exc_info` is set, the exception class name.            |
+
+Reserved `LogRecord` attributes and any key starting with `_` are
+dropped before serialization, so the payload contains only the values
+that callers intentionally attached.
+
+## Secret Redaction
+
+`_SECRET_KEYS` is the canonical denylist applied in two places:
+
+1. **At format time** for keys passed via `extra={...}`.
+2. **At helper time** by `_redact_dict(...)` so values reaching
+   `log_startup` / `log_error` never expose known-sensitive fields
+   even before they hit the formatter.
+
+Deny-list contents (case-insensitive):
+
+```
+token, access_token, mastodon_access_token, password, secret,
+authorization, api_key
+```
+
+Any matching key is replaced with the string `[REDACTED]`.
+
+# Helper Functions
+
+| Helper                                | When it fires                                                         | Logger / Level | `event` field      |
+|---------------------------------------|-----------------------------------------------------------------------|----------------|--------------------|
+| `configure_json_logging(level=INFO)`  | First line of `main.main()`. Idempotent — clears existing handlers.   | n/a            | n/a                |
+| `log_startup(**fields)`               | After config load + `data_dir.mkdir`, before the pipeline pass.       | `INFO`         | `startup`          |
+| `log_error(event, *, exc=None, **fields)` | When a pipeline attempt raises, or when the retry budget is exhausted. | `ERROR`     | the supplied event name; `exc_type` added when `exc` is provided. |
+| `log_run_summary(scanned, matched, posted, skipped, posted_ids)` | Once per successful pass. **Silently skipped** when all counters are zero and no ids were posted. | `INFO`         | `run_complete`     |
+
+## Startup payload
+
+`log_startup` is invoked with:
+
+```
+version, site_url, run_at, tz, hashtags, throwback_prefix
+```
+
+Each is added to the `startup` event payload under its own key.
+
+## Run-summary payload
+
+`log_run_summary` is the canonical "what did the bot do today?" record:
+
+```json
+{
+  "ts": "2026-08-04T09:00:00+00:00",
+  "level": "INFO",
+  "logger": "tenbackward",
+  "message": "run complete",
+  "event": "run_complete",
+  "scanned": 0,
+  "matched": 0,
+  "posted": 0,
+  "skipped": 0,
+  "posted_ids": []
+}
+```
+
+A pass with no candidates emits **no line at all**, matching the
+"silent on no matches" contract.
+
+# Examples
+
+## Successful run with one new post
+
+```json
+{"ts":"2026-08-04T09:00:00+00:00","level":"INFO","logger":"tenbackward","message":"startup","event":"startup","version":"0.1.0","site_url":"https://blog.example.com","run_at":"09:00","tz":"Europe/Berlin","hashtags":"#throwback,#10backward","throwback_prefix":"Throwback:"}
+{"ts":"2026-08-04T09:00:01+00:00","level":"INFO","logger":"tenbackward","message":"run complete","event":"run_complete","scanned":1,"matched":1,"posted":1,"skipped":0,"posted_ids":["2025-08-04-post-slug"]}
+```
+
+## Retry budget exhausted
+
+```json
+{"ts":"...","level":"ERROR","logger":"tenbackward","message":"pipeline_error","event":"pipeline_error","attempt":1,"max_attempts":4,"exc_type":"ConnectionError"}
+{"ts":"...","level":"ERROR","logger":"tenbackward","message":"pipeline_error","event":"pipeline_error","attempt":2,"max_attempts":4,"exc_type":"ConnectionError"}
+{"ts":"...","level":"ERROR","logger":"tenbackward","message":"pipeline_failed","event":"pipeline_failed","attempts":4,"exc_type":"ConnectionError"}
+```
+
+The container then exits with status `1`.
+
+## Token accidentally logged
+
+Even if a future call wrote `extra={"access_token": "..."}`, the
+formatter replaces it:
+
+```json
+{ "...": "...", "access_token": "[REDACTED]" }
+```
+
+# Related
+
+* [System Architecture](/architecture/system-overview.md)
+* [Pipeline Runner](/architecture/pipeline-runner.md)
+* [Config Schema](/architecture/config-schema.md)

docs/architecture/pipeline-runner.md

@@ -0,0 +1,111 @@
+---
+type: architecture
+title: Pipeline Runner
+description: How tenbackward.main turns one cron tick into a startup log line, a retry-wrapped pipeline pass, and a single run_complete summary line.
+tags: [pipeline, runner, retry]
+timestamp: 2026-08-04T17:51:00Z
+---
+
+# Purpose
+
+`tenbackward.main` is the entry point executed by cron. Job 1083
+rewrote it to: (a) install JSON logging, (b) execute a retry-wrapped
+pipeline pass that is **silent when there are no candidates**, and
+(c) emit a single structured `run_complete` summary on success.
+
+# Call Flow
+
+```
+main.main()
+  ├── configure_json_logging()
+  ├── load_config()  ── raises ConfigError → exit 2
+  ├── config.data_dir.mkdir(parents=True, exist_ok=True)
+  ├── log_startup(version, site_url, run_at, tz, hashtags, throwback_prefix)
+  ├── result = _run_with_retry(config)
+  │       ├── for attempt in 1 .. max_retries+1:
+  │       │     try: return _run_once(config)
+  │       │     except Exception as exc:
+  │       │           log_error("pipeline_error", exc=exc, attempt=attempt, max_attempts=attempts)
+  │       ├── log_error("pipeline_failed", exc=last_exc, attempts=attempts)
+  │       └── return None
+  ├── if result is None: return 1
+  └── log_run_summary(scanned, matched, posted, skipped, posted_ids)
+```
+
+# Extension Point: `_iter_candidates`
+
+```python
+def _iter_candidates(config: Config) -> Iterable[str]: ...
+```
+
+Job 1083 ships `_iter_candidates` as an **empty iterator** so the
+silent-on-no-matches contract is the default behaviour. The future
+blog-clone + matching pipeline plugs into this function without
+touching `_run_once` or `_run_with_retry`.
+
+# `_run_once` — Summary Counters
+
+`_run_once` returns a 5-tuple:
+
+```python
+(scanned, matched, posted, skipped, posted_ids)
+```
+
+| Counter     | Meaning                                                              |
+|-------------|----------------------------------------------------------------------|
+| `scanned`   | Items yielded by `_iter_candidates`.                                 |
+| `matched`   | Items that survived the dedupe-vs-`already_posted` check.            |
+| `posted`    | Items newly recorded in `posted.json` during this run.               |
+| `skipped`   | Items that matched but were already in `posted.json` (deduped).      |
+| `posted_ids`| The list of post identifiers written to state.                       |
+
+`state.save_posted` is called **only** when `posted_ids` is non-empty,
+so a no-op run does not touch `posted.json` on disk.
+
+# Retry Behaviour (`_run_with_retry`)
+
+* `attempts = max(1, config.max_retries + 1)` — at least one attempt
+  even if `MAX_RETRIES=0`.
+* Any exception inside `_run_once` is caught (`noqa: BLE001` —
+  intentional, the whole pass is opaque to the runner).
+* Each failed attempt is recorded via
+  `log_error("pipeline_error", exc=exc, attempt=attempt, max_attempts=attempts)`.
+* When the budget is exhausted, the runner emits
+  `log_error("pipeline_failed", exc=last_exc, attempts=attempts)` and
+  returns `None` so `main` can translate it to `exit 1`.
+* `time.sleep(0)` between attempts is the placeholder seam where the
+  next job can introduce real backoff.
+
+# Silent-on-No-Matches Contract
+
+A run with zero candidates produces exactly one line:
+
+```json
+{"ts":"...","level":"INFO","message":"startup","event":"startup",...}
+```
+
+No `run_complete` line is emitted. Tests assert this by counting log
+records (`tests/test_run_logging.py::test_run_summary_silent_when_no_candidates`).
+
+# Example Sequence (Healthy Run)
+
+1.  `startup` line at INFO.
+2.  `_run_with_retry` returns `(0, 0, 0, 0, [])` (no candidates yet
+    because `_iter_candidates` is empty) → `main` exits `0`
+    **without** a `run_complete` line.
+3.  Next-day tick repeats the cycle.
+
+# Example Sequence (Future Blog Step in Place)
+
+1.  `startup` line at INFO.
+2.  `_iter_candidates` yields `[id-1, id-2]`. `id-1` is already in
+    `posted.json`, so `skipped += 1`. `id-2` is new and appended to
+    `posted_ids` and persisted.
+3.  `run_complete` line at INFO with
+    `scanned=2, matched=2, posted=1, skipped=1, posted_ids=["id-2"]`.
+
+# Related
+
+* [Logging & Run Summary](/architecture/logging.md)
+* [Config Schema](/architecture/config-schema.md)
+* [Cron Lifecycle](/operations/cron-lifecycle.md)

docs/architecture/system-overview.md

@@ -0,0 +1,98 @@
+---
+type: architecture
+title: System Architecture
+description: Component map of 10Backward — how config, logging, the pipeline runner, state persistence, and container entrypoint are wired together.
+tags: [architecture, overview]
+timestamp: 2026-08-04T17:51:00Z
+---
+
+# Overview
+
+`10Backward` is a Mastodon daily-throwback bot that runs as a single
+containerised cron job. Job 1083 adds a structured logging layer and a
+retry-capable pipeline runner on top of the scaffold shipped by Job 1082.
+
+The container boots, validates environment configuration, renders a
+`/etc/cron.d/tenbackward` entry that fires once per day at the
+configured `RUN_AT`, and then runs `python -m tenbackward` in the
+foreground of the `cron` process. Each scheduled invocation calls
+`tenbackward.main.main()`, which:
+
+1. Installs the JSON logging formatter on the root logger.
+2. Loads and validates the `Config`.
+3. Ensures the data directory exists.
+4. Emits a `startup` log line.
+5. Executes one pipeline pass wrapped in a retry loop.
+6. Emits a `run_complete` summary (skipped silently if there were no candidates).
+
+# Components
+
+| Component                | Responsibility                                                                                             |
+|--------------------------|------------------------------------------------------------------------------------------------------------|
+| `entrypoint.sh`          | Validates required env vars, renders the cron file from `RUN_AT`/`TZ`, then `exec cron -f`.                |
+| `tenbackward.main`       | CLI entry point; orchestrates startup logging, retry-wrapped pipeline pass, and run summary.               |
+| `tenbackward.config`     | Loads `.env` + process env, applies defaults, validates schema, produces a typed `Config` dataclass.       |
+| `tenbackward.logging_setup` | JSON formatter (one log record per line), secret redaction, and `log_startup` / `log_error` / `log_run_summary` helpers. |
+| `tenbackward.state`      | Read/write of `posted.json` (atomic temp-file replace).                                                    |
+| `tenbackward.blog`       | Stubbed blog clone/update helper (lands in a follow-up job).                                              |
+| `/etc/cron.d/tenbackward`| Rendered cron file. One daily line that `cd /app` and runs `python -m tenbackward`.                        |
+
+# Communication & Wiring
+
+```
++-------------------+      env vars       +-------------------------+
+|     entrypoint    | -------------------> |   config.load_config    |
+|     (.sh)         |                     |   (Config dataclass)    |
++---------+---------+                     +-----------+-------------+
+          |                                           |
+          |  installs cron file                        |  feeds
+          v                                           v
++-------------------+                     +-------------------------+
+| /etc/cron.d/       | -- daily fires --> |   tenbackward.main.main |
+| tenbackward        |                    |   - configure logging   |
++-------------------+                    |   - retry-wrapped pass  |
+                                         +-----------+-------------+
+                                                     |
+                                                     v
+                                         +-------------------------+
+                                         | _run_with_retry(...)    |
+                                         |  -> _run_once(...)      |
+                                         |     -> state.{load,save}|
+                                         +-------------------------+
+```
+
+* **Env → Config.** `load_config()` merges a `.env` file (when
+  present) under the process environment via `dotenv_values` + `load_dotenv`,
+  applies defaults, then validates the merged map before producing the
+  `Config` dataclass.
+* **Cron → main.** Each scheduled tick re-runs `python -m tenbackward`,
+  so every run is a fresh interpreter invocation.
+* **Pipeline state.** `_run_once` reads `posted.json` via
+  `state.load_posted()` for dedupe, then writes it back via
+  `state.save_posted()` only when at least one new post was recorded.
+
+# Key Files
+
+| Path                                | Responsibility                                                                  |
+|-------------------------------------|---------------------------------------------------------------------------------|
+| `/repo/entrypoint.sh`               | Bootstraps cron; validates required env vars; renders `/etc/cron.d/tenbackward`. |
+| `/repo/src/tenbackward/main.py`     | CLI entry, retry wrapper, pipeline counters.                                     |
+| `/repo/src/tenbackward/config.py`   | Env merging, defaults, validation, `Config` dataclass, `ConfigError`.            |
+| `/repo/src/tenbackward/logging_setup.py` | JSON formatter, secret redaction, structured event helpers.                 |
+| `/repo/src/tenbackward/state.py`    | `posted.json` read/write with atomic temp-file replace.                         |
+| `/repo/src/tenbackward/blog.py`     | Stubbed blog clone helper (not yet wired into the pipeline).                    |
+| `/repo/.env.example`                | Canonical list of environment variables.                                        |
+| `/repo/docker-compose.yml`          | Service definition; binds env vars from the host `.env`.                        |
+| `/repo/Dockerfile`                  | Builds the runtime image.                                                       |
+| `/repo/crontab/tenbackward.cron`    | Cron template shipped in the image.                                             |
+| `/repo/crontab/install-cron.sh`     | Installs the rendered cron file with mode 0644; refuses placeholder leftovers.  |
+| `/repo/tests/`                       | Pytest suite covering config, logging, runner, cron, and entrypoint validation. |
+
+# Related
+
+* [Config Schema](/architecture/config-schema.md)
+* [Logging & Run Summary](/architecture/logging.md)
+* [Pipeline Runner](/architecture/pipeline-runner.md)
+* [Daily Run Guide](/guides/daily-run.md)
+* [Environment Variable Setup](/operations/environment-setup.md)
+* [Cron Lifecycle](/operations/cron-lifecycle.md)

docs/guides/daily-run.md

@@ -0,0 +1,118 @@
+---
+type: guide
+title: Daily Run Guide
+description: Operator- and tester-focused walkthrough of one daily cron tick — startup, pipeline pass, silent-on-no-matches, and retry behaviour.
+tags: [guide, run, daily, tester]
+timestamp: 2026-08-04T17:51:00Z
+---
+
+# Purpose
+
+A tester or operator needs to know **what should happen** each time
+the cron tick fires. This guide describes the contract from the
+outside of the container, in observable terms: log lines, exit codes,
+files appearing on the volume, and the "silent on no matches"
+behaviour that the runner enforces.
+
+# Triggering a Run Manually
+
+```bash
+docker compose exec tenbackward /usr/local/bin/python -m tenbackward
+```
+
+This is the same command the container's cron entry issues once per
+day at `RUN_AT`. Use it to verify behaviour without waiting for the
+scheduled tick.
+
+# What You Should See
+
+The bot uses a **JSON-per-line** logger that writes to
+`/app/data/cron.log` (because the cron line redirects with
+`>> /app/data/cron.log 2>&1`). Inspecting the file with
+`docker compose exec tenbackward tail -n 100 /app/data/cron.log`
+should show output similar to:
+
+```json
+{"ts": "2026-08-04T09:00:00+00:00", "level": "INFO", "logger": "tenbackward", "message": "startup", "event": "startup", "version": "0.1.0", "site_url": "https://blog.example.com", "run_at": "09:00", "tz": "Europe/Berlin", "hashtags": "#throwback,#10backward", "throwback_prefix": "Throwback:"}
+```
+
+On the current scaffold (`_iter_candidates` is intentionally empty),
+this is the **only** line you should see — the runner emits no
+`run_complete` when no candidates were found. This is the
+"silent on no matches" contract.
+
+# Expected Container Behaviour
+
+| Scenario                                  | Lines in `cron.log`                                            | Container exit   |
+|-------------------------------------------|----------------------------------------------------------------|------------------|
+| Config valid, zero candidates (scaffold) | 1× `startup`                                                   | `0`              |
+| Config valid, future blog step posts N≥1  | 1× `startup`, then 1× `run_complete` with `posted=N`           | `0`              |
+| Pipeline raises once, recovers            | 1× `pipeline_error`, then 1× `run_complete`                    | `0`              |
+| Pipeline keeps raising (budget exhausted) | `MAX_RETRIES + 1` × `pipeline_error`, then 1× `pipeline_failed` | `1`              |
+| Config invalid                            | 1× `configuration_error` (extras describe what failed)          | `2`              |
+
+> **Tester tip** — `docker compose ps` should report the container as
+> `running` after a `pipeline_failed` exit *only* if cron has not yet
+> fired again. A single failed pipeline tick does not kill the container
+> itself; cron re-runs it the next day.
+
+# Files the Tester Should Look For
+
+| Path (inside container) | When it appears                            |
+|-------------------------|--------------------------------------------|
+| `/app/data/cron.log`    | Always (cron appends stdout/stderr here).  |
+| `/app/data/posted.json` | Created on first persist; only rewritten when a new id is posted. The scaffold run does **not** create this file. |
+
+To verify these from the host:
+
+```bash
+docker compose exec tenbackward ls -la /app/data
+docker compose exec tenbackward cat /app/data/cron.log
+```
+
+# Visual Elements
+
+This is a server-side bot, so there is no UI. The "UI" consists of:
+
+* **Log lines on stdout** — one JSON object per `INFO`/`ERROR` event.
+* **Exit code** — `0` (healthy), `1` (pipeline exhausted), or `2` (config).
+* **`posted.json`** — JSON state file; its mtime changes whenever a new id is persisted.
+
+# Examples
+
+## Healthy scaffold tick
+
+```bash
+$ docker compose exec tenbackward python -m tenbackward
+{"ts":"...","event":"startup",...}
+$ echo $?
+0
+```
+
+## Bad `RUN_AT`
+
+```bash
+$ RUN_AT=25:99 docker compose exec tenbackward python -m tenbackward
+ERROR: RUN_AT='25:99' must be in HH:MM (24-hour) format
+$ docker compose ps
+tenbackward  Exit 1
+```
+
+(The error message lands on stderr in the entrypoint path and is
+captured by `cron.log`.)
+
+## Missing required env var
+
+Unset `MAX_RETRIES`, restart the container:
+
+```bash
+$ docker compose up --build
+tenbackward  | ERROR: missing required environment variable(s): MAX_RETRIES
+tenbackward  exited with code 1
+```
+
+# Related
+
+* [Environment Variable Setup](/operations/environment-setup.md)
+* [Pipeline Runner](/architecture/pipeline-runner.md)
+* [Logging & Run Summary](/architecture/logging.md)

docs/index.md

@@ -0,0 +1,16 @@
+---
+okf_version: "0.1"
+---
+
+# Architecture
+* [System Architecture](/architecture/system-overview.md) — Component map of 10Backward: entrypoint, config, logging, runner, state, and cron wiring.
+* [Config Schema](/architecture/config-schema.md) — Required/optional env vars, validation rules, and the typed Config dataclass.
+* [Logging & Run Summary](/architecture/logging.md) — JSON formatter, secret redaction, and structured event helpers.
+* [Pipeline Runner](/architecture/pipeline-runner.md) — How a cron tick becomes startup + retry-wrapped pass + run_complete.
+
+# Operations
+* [Environment Variable Setup](/operations/environment-setup.md) — Required env vars, renamed keys, and how to populate `.env`.
+* [Cron Lifecycle](/operations/cron-lifecycle.md) — How `entrypoint.sh` renders `/etc/cron.d/tenbackward` and hands off to `cron -f`.
+
+# User Guides
+* [Daily Run Guide](/guides/daily-run.md) — Tester/operator walkthrough of a manual daily cron tick and expected log/output behaviour.

docs/operations/cron-lifecycle.md

@@ -0,0 +1,96 @@
+---
+type: operations
+title: Cron Lifecycle
+description: How entrypoint.sh validates env, renders /etc/cron.d/tenbackward from RUN_AT/TZ, and hands off to cron -f.
+tags: [cron, entrypoint, ops]
+timestamp: 2026-08-04T17:51:00Z
+---
+
+# Purpose
+
+`entrypoint.sh` is the first process inside the container. Its job is
+to refuse to boot when something is wrong with env config and to
+materialise a cron file from the templated values.
+
+# Sequence
+
+1. Set `DEBIAN_FRONTEND=noninteractive`.
+2. Set `TZ` (default `Europe/Berlin`) and link `/etc/localtime` if
+   `/usr/share/zoneinfo/${TZ}` exists and `/etc/localtime` does not.
+3. Iterate over `required_vars`. Any empty variable aborts with
+   `ERROR: missing required environment variable(s): ...` and exits
+   `1`. The current required set is listed in
+   [Environment Variable Setup](/operations/environment-setup.md).
+4. Validate `RUN_AT` against
+   `^([01][0-9]|2[0-3]):[0-5][0-9]$`. Invalid input exits `1` with
+   `ERROR: RUN_AT='X' must be in HH:MM (24-hour) format`.
+5. Render `/etc/cron.d/tenbackward` into a `mktemp` file with:
+
+    ```cron
+    SHELL=/bin/bash
+    PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
+    TZ=${TZ}
+    ${minute} ${hour} * * * cd /app && /usr/local/bin/python -m tenbackward >> /app/data/cron.log 2>&1
+    ```
+
+6. Install the rendered file with mode `0644`, root:root.
+7. Run `crontab/install-cron.sh /etc/cron.d/tenbackward`. The helper
+   refuses files that still contain the `__RUN_AT__` placeholder and
+   files that do not start with an `^[A-Z_]+=` cron env line.
+8. Print a one-line confirmation: `tenbackward: starting cron
+   (RUN_AT=..., TZ=...)`.
+9. `exec cron -f`.
+
+# Output Files
+
+| Path                         | Owner / Mode | Purpose                                              |
+|------------------------------|--------------|------------------------------------------------------|
+| `/etc/cron.d/tenbackward`    | root / 0644  | The rendered cron file.                              |
+| `/app/data/cron.log`         | container user / append | `python -m tenbackward` stdout+stderr.       |
+| `/app/data/posted.json`      | container user / rw     | Persisted state from `tenbackward.state`.    |
+
+# Cron Helpers
+
+| File                            | Purpose                                                                |
+|---------------------------------|------------------------------------------------------------------------|
+| `crontab/tenbackward.cron`      | Static template (env + PATH) shipped in the image.                     |
+| `crontab/install-cron.sh`       | Validates and installs a rendered cron file with mode 0644.            |
+
+# Operator Recipes
+
+* **Trigger a manual run** without waiting for the cron tick:
+
+    ```bash
+    docker compose exec tenbackward /usr/local/bin/python -m tenbackward
+    ```
+
+* **Inspect the rendered cron file** (the file the container actually
+  installed):
+
+    ```bash
+    docker compose exec tenbackward cat /etc/cron.d/tenbackward
+    ```
+
+* **Tail the structured logs** produced by the bot:
+
+    ```bash
+    docker compose exec tenbackward tail -n 100 /app/data/cron.log
+    ```
+
+    Expect one JSON object per line (`startup`, optional `run_complete`,
+    or `pipeline_error` / `pipeline_failed`).
+
+# Build Script Notes
+
+`build.sh` now `cd`s into its own script directory (so it works
+no matter where it is invoked from) and, when possible, symlinks
+itself to `/usr/local/bin/build.sh` so the build can also be run as a
+plain `build.sh` command inside the build context. The symlink is a
+best-effort `|| true`, so a read-only filesystem will not break the
+build.
+
+# Related
+
+* [Environment Variable Setup](/operations/environment-setup.md)
+* [Pipeline Runner](/architecture/pipeline-runner.md)
+* [Logging & Run Summary](/architecture/logging.md)

docs/operations/environment-setup.md

@@ -0,0 +1,95 @@
+---
+type: operations
+title: Environment Variable Setup
+description: How to provide and validate the required env vars for the 10Backward container — .env, docker-compose, and the runtime check in entrypoint.sh.
+tags: [env, ops, setup]
+timestamp: 2026-08-04T17:51:00Z
+---
+
+# Purpose
+
+Job 1083 promoted every previously-optional knob in `.env.example`
+to required, and renamed three of them. Operators must populate the
+full set before the container will boot.
+
+# Required Variables
+
+| Variable                 | Example value                  | Purpose                                           |
+|--------------------------|--------------------------------|---------------------------------------------------|
+| `MASTODON_BASE_URL`      | `https://mastodon.social`      | Mastodon instance to post against.                |
+| `MASTODON_ACCESS_TOKEN`  | _(from your Mastodon account)_ | OAuth access token.                               |
+| `VISIBILITY`             | `public`                       | Post visibility (`public` or `unlisted`).         |
+| `SITE_URL`               | `https://blog.example.com`     | Source blog URL (used by the future clone step).  |
+| `HASHTAGS`               | `#throwback,#10backward`       | Hashtags appended to every throwback post.        |
+| `THROWNBACK_PREFIX`      | `Throwback:`                   | Prefix prepended to every post.                   |
+| `MAX_RETRIES`            | `3`                            | Non-negative retry count for the pipeline.        |
+| `RUN_AT`                 | `09:00`                        | Daily fire time (HH:MM, 24-hour).                 |
+| `TZ`                     | `Europe/Berlin`                | IANA timezone for cron + container clock.         |
+
+# Where Each Name Is Enforced
+
+* `entrypoint.sh` — exports `TZ`, validates all nine are non-empty,
+  and validates `RUN_AT` matches `^([01][0-9]|2[0-3]):[0-5][0-9]$`
+  before writing the cron file. A missing var aborts the container
+  with `ERROR: missing required environment variable(s): ...` and
+  exits `1`.
+* `tenbackward.config.validate_config` — same set, plus URL/visibility/
+  TZ/MAX_RETRIES validation. Failures surface as a single
+  `ConfigError` listing every problem.
+* The `kilo.json` config file is **not** an env-var file — it is the
+  agent runtime configuration.
+
+# Setup Steps
+
+1. Copy the template:
+
+    ```bash
+    cp .env.example .env
+    ```
+
+2. Replace placeholder values in `.env` (the example ships with
+   `MASTODON_ACCESS_TOKEN=replace-me` and `https://mastodon.example`).
+
+3. Verify the file parses by running the validator directly:
+
+    ```bash
+    python -m tenbackward
+    ```
+
+    A successful validation run emits one `startup` JSON log line and
+    exits `0`. Missing/invalid config exits `2`.
+
+4. Bring up the container:
+
+    ```bash
+    docker compose up --build
+    ```
+
+    The required-var check in `entrypoint.sh` runs first; if any
+    variable is empty, the container exits before `cron` starts.
+
+# Renames vs. Job 1082
+
+| Old key                | New key                  |
+|------------------------|--------------------------|
+| `MASTODON_VISIBILITY`  | `VISIBILITY`             |
+| `THROWBACK_PREFIX`     | `THROWNBACK_PREFIX`      |
+| `RETRY_COUNT`          | `MAX_RETRIES`            |
+
+If you have an existing `.env` from the scaffold, rename these
+manually. The renamed variables are **not** backwards compatible — the
+container will refuse to start with both versions set.
+
+# Defaults That Can Be Removed
+
+`DEFAULTS` provides fallbacks for `VISIBILITY`, `THROWNBACK_PREFIX`,
+`MAX_RETRIES`, `TZ`, and `RUN_AT`. You may leave them out of your
+`.env`, but the operator contract is "every required key is set" —
+prod deployments should set them explicitly so a missing key is
+caught at boot instead of silently used as a default.
+
+# Related
+
+* [Config Schema](/architecture/config-schema.md)
+* [System Architecture](/architecture/system-overview.md)
+* [Cron Lifecycle](/operations/cron-lifecycle.md)