development: code relying on another component cites its source; stage 2c: the heuristics review

Owner, 2026-10-14: "нам нужно полное ревью кода на предмет всей этой
эвристики. Её не должно там, где можно посмотреть код и ответить точно и
однозначно", and "в коде таких наших блоков должно быть обоснование со
ссылкой на код компонента".

- development.md § Code that relies on another component's behaviour: the
  rule, with the form of the comment (component, the image's version, file,
  function; or a document's URL and section; or "measured on the stand,
  date" said as such), and fixtures saying whether they were seen or
  composed.
- Audit stage 2c: the line "what was taken on trust" becomes the heuristics
  review - an inventory over the whole tree written down as
  docs/assumptions-2026-10-14.md, then each answered from the source of the
  version the image runs, the comment added, the code fixed where it
  contradicts. Plan still 66 lines.

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

docs/audit-2026-10-12.md

@@ -873,20 +873,26 @@ those after it move up one patch number each.
    shared files of lines (`from-lines-passed.txt`, `from-lines-other.txt`)
    are kept: the second one's test becomes "never signed for {other}"
    rather than "refused". - **Opus**
-- [ ] **What was taken on trust, read in Postfix's source** (owner,
-   2026-10-14: "запиши себе правило не гадать, как работает код, если можно
-   посмотреть в его документацию или исходный код"; then "Есть ли ещё у нас
-   места, где мы угадывали?"). Postfix 3.7.11 - the image's version - read
-   for: (1) when qmgr expires a message against maximal_queue_lifetime - the
-   "+ maximal_backoff" margin of queued_over_lifetime is a guess; (2) whether
-   postlogd goes on writing to the renamed mail.log until the reload - the
-   rotation window the deferred tailer fix is about; (3) why an smtpd from
-   before a reload takes one more connection, and for how long - measured
-   (under 2 s), not understood; (4) the NOQUEUE reject line's fields - two
-   test fixtures carry a sasl_username= that Postfix does not write, one
-   of them presented as seen on the stand; they are corrected. What is read
-   goes into architecture.md with the file it is in; where it contradicts
-   the code, the code is fixed in this stage. - **Opus**
+- [ ] **The heuristics review: every assumption about another component,
+   answered from its source** (owner, 2026-10-14: "нам нужно полное ревью
+   кода на предмет всей этой эвристики. Её не должно там, где можно
+   посмотреть код и ответить точно и однозначно" and "в коде таких наших
+   блоков должно быть обоснование со ссылкой на код компонента"; the rule is
+   in development.md § Code that relies on another component's behaviour).
+   First an inventory, over the whole tree (Go, build scripts, configs,
+   tests' fixtures, docs' claims): each place SelfPost relies on what
+   Postfix, OpenDKIM, Cyrus SASL, rspamd, supervisord, logrotate, Docker,
+   SQLite/modernc, go-milter or a browser does, with what is assumed and
+   what justifies it today (read, measured, nothing). It is written down as
+   `docs/assumptions-2026-10-14.md`. Then each is answered from the source
+   or documentation of the version the image runs, and the code gets the
+   comment that cites it; a measurement stays a measurement and says so;
+   where the source contradicts the code, the code is fixed in this stage.
+   Known before the inventory: qmgr's expiry against the queue lifetime (the
+   margin of queued_over_lifetime), postlogd after a rename (the rotation
+   window), the smtpd that outlives a reload (measured, not understood), the
+   NOQUEUE line's fields (two fixtures carry a sasl_username= Postfix does
+   not write, one presented as seen on the stand). - **Opus**
 - [ ] Docs and wording: help topic sender-check and guide § Who an
    application may send as (mockup first), security.md § Mail path,
    CHANGELOG. - **Sonnet**

docs/development.md

@@ -215,6 +215,30 @@ Plex [OFL.txt](../internal/web/view/static/OFL.txt) under
 `/usr/share/doc/selfpost/`. The panel serves the AGPL text at `/license` and
 the OFL text at `/static/OFL.txt`.
 
+### Code that relies on another component's behaviour
+
+The owner's rule (2026-10-14): what another program does is read in its
+documentation or its source - never guessed. SelfPost reads Postfix's log
+lines and reply codes, feeds OpenDKIM's tables, parses `postqueue`,
+`postconf`, `supervisorctl` and `db_dump` output, talks the milter protocol
+through go-milter, relies on SQLite's locking, on logrotate's and Docker's
+behaviour. Every block of code that does so carries a comment that says
+what it relies on and where that is written, for the version the image runs
+(the Debian bookworm package, not upstream's head):
+
+```go
+// Postfix 3.7.11, src/smtpd/smtpd_check.c, check_sender_login():
+// the SASL login is compared with the sender map's owners by strcasecmp.
+```
+
+A document instead of source: its URL and section. Where neither answers the
+question, the comment says so and what was measured instead - "measured on
+the e2e stand, 2026-10-14: ..." - and a measurement is never written as if
+it were read. A test fixture copied from a real log says where and when it
+was seen; one composed by hand says that it was composed. The heuristics
+review of 2026-10-14 (audit-2026-10-12, stage 2c) brought the code that
+existed then up to this rule.
+
 ---
 
 ## Building binaries and the image