Replace the CompletionParams { systemPrompt, userPrompt } string pair with a
structured { system, messages[] } request across all five AI clients. One
refactor unlocks three things: provider prompt-caching (Anthropic cache_control
on the stable system prefix, OpenAI/Codex automatic prefix cache, with
cachedInputTokens surfaced for observability), the tool-calling wire surface,
and clean multi-turn.
Each client maps the new shape to its own wire and degrades unsupported
features silently: the local OpenAI-compatible server never receives a tools
field (most reject unknown keys), and prompt-caching is best-effort everywhere.
CompletionResult gains toolCalls, finishReason and cachedInputTokens; the tool
types and per-provider mapping ship now, the tool-use loop does not.
Vision inputs fold into the user turn's content parts via singleUserTurn, with
each provider's pre-existing block ordering preserved. The corrective-retry
paths append to the last user message rather than a flat string. The Coach
keeps assembling one user turn so its snapshot-once and grounding behaviour is
unchanged. No wire schema visible to API consumers changed.
Behaviour is unchanged across every surface; the full suite stays green.
When a first-attempt response omits the rationale object (or emits
empty comparedTo / deviation strings), the corrective reprompt
now names the three rationale fields explicitly so the model has
a targeted fix instead of guessing what changed. The reprompt also
restates that rationale.dataWindow MUST equal metricSource.timeRange
— bracket-mismatch is the most likely model-side bug now that the
shape is new.
The wrapper's post-validation `annotate()` block additionally
emits three new Wide-Event meta fields:
- ai_rationale_total_recommendations
- ai_rationale_with_rationale
- ai_rationale_missing_recommendation_ids
Strict-parsed payloads always have rationale on every rec (the
schema rejects otherwise), so the missing-ids array is an
observability tripwire — it will only populate if a legacy payload
ever rides through .passthrough() on a back-compat path.
v1.4.17 admin AI dashboard plots rationale-coverage alongside the
existing citation-coverage breakdown.
4 new tests in `rationale-wrapper.test.ts` pin the contract:
- corrective retry message names dataWindow / comparedTo / deviation
- empty deviation triggers retry (not just absent rationale)
- annotate() carries the new ai_rationale_* keys on success
- rationale-coverage = totalRecommendations on a fully-shaped payload
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Marc-André Bombeck