feat: thread-detection service (T55)

2026-04-26 20:10:36 -04:00
parent da1f67fb6a
commit 7857da4112
2 changed files with 217 additions and 0 deletions
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+"""Thread-detection service (T55).
+
+On scene close, classify the transcript into thread open/update/close
+candidates. Returns ThreadCandidate list; caller (T58 scene compression)
+emits one thread_opened/thread_updated/thread_closed event per candidate.
+"""
+
+from __future__ import annotations
+
+from pydantic import BaseModel, Field
+
+from chat.llm.classify import classify
+from chat.llm.client import LLMClient
+
+
+class ThreadCandidate(BaseModel):
+    action: str  # "open" | "update" | "close"
+    title: str = ""        # required for "open"; ignored otherwise
+    summary: str = ""
+    existing_thread_id: str | None = None  # required for "update" / "close"
+
+
+class ThreadDetectionResult(BaseModel):
+    candidates: list[ThreadCandidate] = Field(default_factory=list)
+
+
+_SYSTEM = (
+    "You analyze a closed scene's transcript to identify narrative "
+    "threads (unresolved arcs, dangling questions, promises made, "
+    "open obligations). Choose actions:\n"
+    "- 'open': a NEW thread the scene introduced. Provide title (short "
+    "noun phrase) + summary (one sentence).\n"
+    "- 'update': an EXISTING open thread that the scene developed. "
+    "Provide existing_thread_id + new summary.\n"
+    "- 'close': an EXISTING open thread that the scene resolved. "
+    "Provide existing_thread_id; summary may capture the resolution.\n"
+    "Conservative bias: most scenes do NOT open new threads. Only "
+    "produce candidates when the transcript clearly justifies them. "
+    "Output strict JSON matching the schema."
+)
+
+
+async def detect_threads(
+    client: LLMClient,
+    *,
+    classifier_model: str,
+    scene_transcript: list[dict],   # [{speaker, text}, ...]
+    open_threads: list[dict],       # [{thread_id, title, summary}, ...]
+    timeout_s: float = 30.0,
+) -> ThreadDetectionResult:
+    """Classify scene close into thread open/update/close candidates."""
+    if not scene_transcript:
+        return ThreadDetectionResult()
+
+    transcript_lines = [
+        f"{turn.get('speaker', 'unknown')}: {turn.get('text', '')}"
+        for turn in scene_transcript
+    ]
+    threads_lines = []
+    if open_threads:
+        threads_lines.append("Currently open threads:")
+        for t in open_threads:
+            threads_lines.append(
+                f"- thread_id={t['thread_id']} "
+                f"title={t.get('title', '')} "
+                f"summary={t.get('summary', '')}"
+            )
+    else:
+        threads_lines.append("No currently open threads.")
+
+    user = (
+        "Scene transcript:\n"
+        + "\n".join(transcript_lines)
+        + "\n\n"
+        + "\n".join(threads_lines)
+    )
+
+    return await classify(
+        client,
+        model=classifier_model,
+        system=_SYSTEM,
+        user=user,
+        schema=ThreadDetectionResult,
+        default=ThreadDetectionResult(),
+        timeout_s=timeout_s,
+    )
+
+
+__all__ = ["ThreadCandidate", "ThreadDetectionResult", "detect_threads"]