48 lines
2.0 KiB
TypeScript
48 lines
2.0 KiB
TypeScript
/**
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* Probe/teach phase derivation (vision §2 "Two phases, clearly separated").
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*
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* The session's phase is DERIVED, never stored: `plan_init` IS the transition
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* marker — the call already fires exactly once at the seam (verified live in
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* Gate 1), so no new agent tool exists. Phase = "probe" until the first
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* message containing a `plan_init` tool part; from that message onward,
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* phase = "teach". Everything after it (checks, follow-up asks) is teaching.
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*
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* Pure: no imports, no runtime deps — safe on server, client, and in tests.
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*/
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/** The two phases of a session. */
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export type Phase = "probe" | "teach";
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/** Minimal structural slice of a UI message — anything with typed parts. */
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export interface PhaseMessage {
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parts: ReadonlyArray<{ type: string }>;
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}
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const PLAN_INIT_PART = "tool-plan_init";
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/**
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* The phase at `upToIndex` (inclusive; default: the last message).
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*
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* Scans messages[0..upToIndex] for the FIRST message containing a
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* `tool-plan_init` part — any part state counts (the call itself is the
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* transition; teaching has begun even while the call's input streams). The
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* message that contains plan_init is already teach: the divider renders
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* exactly there, so probe content sits above it, teaching below.
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*
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* Boundary semantics:
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* - no plan_init anywhere → "probe" at every index (pre-plan sessions keep
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* the old auto-open behavior for every question — backward compatible).
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* - first plan_init in message i → phaseAt(m, i-1) === "probe",
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* phaseAt(m, i) === "teach", and every index after.
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* - multiple plan_init parts → the FIRST wins (a re-init attempt later in
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* the transcript never moves the seam; the tool refuses re-init anyway).
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*/
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export function phaseAt(messages: readonly PhaseMessage[], upToIndex?: number): Phase {
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const last = Math.min(upToIndex ?? messages.length - 1, messages.length - 1);
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for (let i = 0; i <= last; i++) {
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const parts = messages[i]?.parts;
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if (parts?.some((p) => p.type === PLAN_INIT_PART)) return "teach";
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}
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return "probe";
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}
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