refactor(frontend): extract attention scorer and shared type guards

v2/src/lib/adapters/claude-messages.ts

@@ -72,15 +72,7 @@ export interface ErrorContent {
   message: string;
 }
 
-/** Runtime guard — returns value if it's a string, fallback otherwise */
-function str(v: unknown, fallback = ''): string {
-  return typeof v === 'string' ? v : fallback;
-}
-
-/** Runtime guard — returns value if it's a number, fallback otherwise */
-function num(v: unknown, fallback = 0): number {
-  return typeof v === 'number' ? v : fallback;
-}
+import { str, num } from '../utils/type-guards';
 
 /**
  * Adapt a raw SDK stream-json message to our internal format.

v2/src/lib/adapters/codex-messages.ts

@@ -13,13 +13,7 @@ import type {
   ErrorContent,
 } from './claude-messages';
 
-function str(v: unknown, fallback = ''): string {
-  return typeof v === 'string' ? v : fallback;
-}
-
-function num(v: unknown, fallback = 0): number {
-  return typeof v === 'number' ? v : fallback;
-}
+import { str, num } from '../utils/type-guards';
 
 export function adaptCodexMessage(raw: Record<string, unknown>): AgentMessage[] {
   const timestamp = Date.now();

v2/src/lib/adapters/ollama-messages.ts

@@ -11,13 +11,7 @@ import type {
   ErrorContent,
 } from './claude-messages';
 
-function str(v: unknown, fallback = ''): string {
-  return typeof v === 'string' ? v : fallback;
-}
-
-function num(v: unknown, fallback = 0): number {
-  return typeof v === 'number' ? v : fallback;
-}
+import { str, num } from '../utils/type-guards';
 
 /**
  * Adapt a raw Ollama runner event to AgentMessage[].

v2/src/lib/stores/health.svelte.ts

@@ -3,6 +3,7 @@
 
 import { getAgentSession, type AgentSession } from './agents.svelte';
 import { getProjectConflicts } from './conflicts.svelte';
+import { scoreAttention } from '../utils/attention-scorer';
 
 // --- Types ---
 
@@ -51,13 +52,6 @@ const MODEL_CONTEXT_LIMITS: Record<string, number> = {
 };
 const DEFAULT_CONTEXT_LIMIT = 200_000;
 
-// Attention score weights (higher = more urgent)
-const SCORE_STALLED = 100;
-const SCORE_CONTEXT_CRITICAL = 80; // >90% context
-const SCORE_CONTEXT_HIGH = 40; // >75% context
-const SCORE_ERROR = 90;
-const SCORE_FILE_CONFLICT = 70; // 2+ agents writing same file
-const SCORE_IDLE_LONG = 20; // >2x stall threshold but not stalled (shouldn't happen, safety)
 
 // --- State ---
 
@@ -251,28 +245,16 @@ function computeHealth(tracker: ProjectTracker, now: number): ProjectHealth {
   const fileConflictCount = conflicts.conflictCount;
   const externalConflictCount = conflicts.externalConflictCount;
 
-  // Attention scoring — highest-priority signal wins
-  let attentionScore = 0;
-  let attentionReason: string | null = null;
-
-  if (session?.status === 'error') {
-    attentionScore = SCORE_ERROR;
-    attentionReason = `Error: ${session.error?.slice(0, 60) ?? 'Unknown'}`;
-  } else if (activityState === 'stalled') {
-    attentionScore = SCORE_STALLED;
-    const mins = Math.floor(idleDurationMs / 60_000);
-    attentionReason = `Stalled — ${mins} min since last activity`;
-  } else if (contextPressure !== null && contextPressure > 0.9) {
-    attentionScore = SCORE_CONTEXT_CRITICAL;
-    attentionReason = `Context ${Math.round(contextPressure * 100)}% — near limit`;
-  } else if (fileConflictCount > 0) {
-    attentionScore = SCORE_FILE_CONFLICT;
-    const extNote = externalConflictCount > 0 ? ` (${externalConflictCount} external)` : '';
-    attentionReason = `${fileConflictCount} file conflict${fileConflictCount > 1 ? 's' : ''}${extNote}`;
-  } else if (contextPressure !== null && contextPressure > 0.75) {
-    attentionScore = SCORE_CONTEXT_HIGH;
-    attentionReason = `Context ${Math.round(contextPressure * 100)}%`;
-  }
+  // Attention scoring — delegated to pure function
+  const attention = scoreAttention({
+    sessionStatus: session?.status,
+    sessionError: session?.error,
+    activityState,
+    idleDurationMs,
+    contextPressure,
+    fileConflictCount,
+    externalConflictCount,
+  });
 
   return {
     projectId: tracker.projectId,
@@ -284,8 +266,8 @@ function computeHealth(tracker: ProjectTracker, now: number): ProjectHealth {
     contextPressure,
     fileConflictCount,
     externalConflictCount,
-    attentionScore,
-    attentionReason,
+    attentionScore: attention.score,
+    attentionReason: attention.reason,
   };
 }
 

v2/src/lib/utils/attention-scorer.ts

@@ -0,0 +1,68 @@
+// Attention scoring — pure function extracted from health store
+// Determines which project needs attention most urgently
+
+import type { ActivityState } from '../stores/health.svelte';
+
+// Attention score weights (higher = more urgent)
+const SCORE_STALLED = 100;
+const SCORE_ERROR = 90;
+const SCORE_CONTEXT_CRITICAL = 80; // >90% context
+const SCORE_FILE_CONFLICT = 70;
+const SCORE_CONTEXT_HIGH = 40; // >75% context
+
+export interface AttentionInput {
+  sessionStatus: string | undefined;
+  sessionError: string | undefined;
+  activityState: ActivityState;
+  idleDurationMs: number;
+  contextPressure: number | null;
+  fileConflictCount: number;
+  externalConflictCount: number;
+}
+
+export interface AttentionResult {
+  score: number;
+  reason: string | null;
+}
+
+/** Score how urgently a project needs human attention. Highest-priority signal wins. */
+export function scoreAttention(input: AttentionInput): AttentionResult {
+  if (input.sessionStatus === 'error') {
+    return {
+      score: SCORE_ERROR,
+      reason: `Error: ${input.sessionError?.slice(0, 60) ?? 'Unknown'}`,
+    };
+  }
+
+  if (input.activityState === 'stalled') {
+    const mins = Math.floor(input.idleDurationMs / 60_000);
+    return {
+      score: SCORE_STALLED,
+      reason: `Stalled — ${mins} min since last activity`,
+    };
+  }
+
+  if (input.contextPressure !== null && input.contextPressure > 0.9) {
+    return {
+      score: SCORE_CONTEXT_CRITICAL,
+      reason: `Context ${Math.round(input.contextPressure * 100)}% — near limit`,
+    };
+  }
+
+  if (input.fileConflictCount > 0) {
+    const extNote = input.externalConflictCount > 0 ? ` (${input.externalConflictCount} external)` : '';
+    return {
+      score: SCORE_FILE_CONFLICT,
+      reason: `${input.fileConflictCount} file conflict${input.fileConflictCount > 1 ? 's' : ''}${extNote}`,
+    };
+  }
+
+  if (input.contextPressure !== null && input.contextPressure > 0.75) {
+    return {
+      score: SCORE_CONTEXT_HIGH,
+      reason: `Context ${Math.round(input.contextPressure * 100)}%`,
+    };
+  }
+
+  return { score: 0, reason: null };
+}

v2/src/lib/utils/type-guards.ts

@@ -0,0 +1,11 @@
+// Runtime type guards for safely extracting values from untyped wire formats
+
+/** Returns value if it's a string, fallback otherwise */
+export function str(v: unknown, fallback = ''): string {
+  return typeof v === 'string' ? v : fallback;
+}
+
+/** Returns value if it's a number, fallback otherwise */
+export function num(v: unknown, fallback = 0): number {
+  return typeof v === 'number' ? v : fallback;
+}