assemblePrompt used template.replace("{{GATE}}", ...), and String.replace
with a string argument substitutes only the FIRST occurrence. All three
placeholders appear twice in tutor-system.md, because the document names
them in its own header paragraph before using them:
Assembled per turn. `{{GATE}}` is `renderGate()` from `lib/gate.js`;
`{{VARIETY}}` and `{{FOCUS}}` are one-liners built from recent state.
So the rendered gate replaced the backticked mention mid-sentence, and the
real slot further down was sent to the model as the literal text "{{GATE}}".
The mechanism that decides what the tutor is allowed to teach was delivered
in the wrong place, with a template token standing where it belonged, and
the same for VARIETY and FOCUS. Confirmed by capturing what the app
actually put on the wire: three unfilled placeholders at lines 60, 86 and
141.
Substitution is now anchored to a whole line, which is what distinguishes a
slot from a mention -- the header's are inline and backticked. The
replacement is a function because renderGate() output contains "$"
sequences that String.replace would otherwise interpret.
The existing tests could not have caught this. They ran against a synthetic
template naming each placeholder exactly once, which is precisely the
property the shipped file lacks. The new ones run against
prompt/tutor-system.md itself: no slot may survive unfilled, the header
must come through intact, and the gate must land between the profile and
the pre-flight check. Both fail against the old code.
Also appends a HOUSE STYLE section after the shipped prompt -- an addition
by the app, not an edit to the file, which still ships byte-identical.
It covers two things the prompt leaves to inference. The language of
explanation is never actually stated: "한글 and English only" is a rule
about retiring romanization, and everything else only implies English. A
strong model infers it; gpt-oss-20b delivered a full grammar lesson in
Korean to a student on unit 1.1 who cannot yet read it. And no-markdown is
stated outright at line 96 and was ignored anyway, so it is restated where
the consequence is visible: the app renders **bold** and nothing else, so a
table arrives as rows of literal pipes.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
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