feat: observability logs across entire query + compaction pipeline

All components now emit target="observability" structured logs:

chunk_optimizer:
  event=chunk_optimize: input, after_threshold_filter, after_dedup,
    dedup_removed, selected, budget_bytes

result_compressor:
  event=result_compress: input_count, estimated_bytes, compressed_bytes,
    budget_bytes, strategy

query_router:
  event=query_route: route, candidates, prefiltered, selected, latency_ms

cache_alignment:
  event=cache_preload: preloaded, cache_hits, cache_misses, hit_ratio

full_pipeline:
  event=full_pipeline_complete: query, candidates, prefiltered, optimized,
    dedup_removed, boosts_applied, cache_hit_ratio, budget_bytes, total_ms

compaction:
  event=compaction_complete: mode, duration_ms, duplicate_edges_deleted,
    stale_facts_deleted, semantic_merged, llm_calls, bytes_freed

781 tests pass.

crates/mem-cli/src/cache_alignment.rs

@@ -224,9 +224,20 @@ impl KvCacheAligner {
 
     /// Pre-load hot chunks into cache
     pub fn preload_hot_chunks(&self, hot_chunks: Vec<(&str, &str)>) -> Result<()> {
+        let count = hot_chunks.len();
         for (chunk_id, text) in hot_chunks {
             self.cache.put(chunk_id, text);
         }
+        let metrics = self.cache.metrics();
+        tracing::info!(
+            target: "observability",
+            event = "cache_preload",
+            preloaded = count,
+            cache_hits = metrics.hits,
+            cache_misses = metrics.misses,
+            hit_ratio = format!("{:.2}", metrics.hit_ratio()),
+            "Cache preload complete"
+        );
         Ok(())
     }
 

crates/mem-cli/src/chunk_optimizer.rs

@@ -211,17 +211,32 @@ impl ChunkOptimizer {
 
     /// End-to-end optimization pipeline
     pub fn optimize(&self, chunks: Vec<OptimizableChunk>) -> (Vec<OptimizableChunk>, SelectionMetrics) {
+        let input_count = chunks.len();
+
         // Step 1: Filter by threshold
         let filtered = self.threshold_filter.filter(chunks.clone());
+        let after_filter = filtered.len();
 
         // Step 2: Deduplicate
         let (deduplicated, dedup_removed) = self.deduplicator.deduplicate(filtered);
+        let after_dedup = deduplicated.len();
 
         // Step 3: Select within budget
         let (selected, mut metrics) = self.budget_selector.select(deduplicated);
-
         metrics.dedup_removed = dedup_removed;
 
+        tracing::info!(
+            target: "observability",
+            event = "chunk_optimize",
+            input = input_count,
+            after_threshold_filter = after_filter,
+            after_dedup = after_dedup,
+            dedup_removed = dedup_removed,
+            selected = selected.len(),
+            budget_bytes = metrics.total_bytes,
+            "Chunk optimization complete"
+        );
+
         (selected, metrics)
     }
 }

crates/mem-cli/src/compaction.rs

@@ -346,7 +346,19 @@ pub async fn compact_memory(
     }
 
     total_stats.duration_ms = start.elapsed().as_millis() as u64;
-    info!("Compaction complete in {}ms: {:?}", total_stats.duration_ms, total_stats);
+    info!(
+        target: "observability",
+        event = "compaction_complete",
+        mode = ?mode,
+        duration_ms = total_stats.duration_ms,
+        duplicate_edges_deleted = total_stats.duplicate_edges_deleted,
+        stale_facts_deleted = total_stats.stale_facts_deleted,
+        semantic_merged = total_stats.semantic_merged,
+        llm_calls = total_stats.llm_calls,
+        bytes_freed = total_stats.bytes_freed,
+        human_reviews_queued = total_stats.human_reviews_queued,
+        "Compaction complete"
+    );
 
     Ok(total_stats)
 }

crates/mem-cli/src/full_pipeline.rs

@@ -344,6 +344,22 @@ impl FullPipeline {
 
         metrics.total_latency_ms = start.elapsed().as_millis() as u64;
 
+        tracing::info!(
+            target: "observability",
+            event = "full_pipeline_complete",
+            query = query,
+            candidates = metrics.wiki_scope_docs,
+            prefiltered = metrics.prefilter_candidates,
+            optimized = metrics.post_optimization_count,
+            dedup_removed = metrics.dedup_removed,
+            boosts_applied = metrics.metadata_boosts_applied,
+            cache_hit_ratio = format!("{:.2}", metrics.cache_hit_ratio),
+            budget_bytes = metrics.budget_used_bytes,
+            total_ms = metrics.total_latency_ms,
+            "Full query pipeline complete"
+        );
+
+
         Ok(PipelineResult {
             query: query.to_string(),
             query_intent,
@@ -467,6 +483,22 @@ impl FullPipeline {
 
         metrics.total_latency_ms = start.elapsed().as_millis() as u64;
 
+        tracing::info!(
+            target: "observability",
+            event = "full_pipeline_complete",
+            query = query,
+            candidates = metrics.wiki_scope_docs,
+            prefiltered = metrics.prefilter_candidates,
+            optimized = metrics.post_optimization_count,
+            dedup_removed = metrics.dedup_removed,
+            boosts_applied = metrics.metadata_boosts_applied,
+            cache_hit_ratio = format!("{:.2}", metrics.cache_hit_ratio),
+            budget_bytes = metrics.budget_used_bytes,
+            total_ms = metrics.total_latency_ms,
+            "Full query pipeline complete"
+        );
+
+
         Ok(PipelineResult {
             query: query.to_string(),
             query_intent,

crates/mem-cli/src/query_router.rs

@@ -238,6 +238,17 @@ impl QueryRouter {
 
         let latency_ms = start.elapsed().as_millis() as u64;
 
+        tracing::info!(
+            target: "observability",
+            event = "query_route",
+            route = "direct",
+            candidates = all_candidates.len(),
+            prefiltered = prefilter_size,
+            selected = selected_chunks.len(),
+            latency_ms = latency_ms,
+            "Query routing complete"
+        );
+
         Ok(RoutedResult {
             selected_chunks,
             route,

crates/mem-cli/src/result_compressor.rs

@@ -235,6 +235,18 @@ impl BudgetCompressor {
         let strategy = self.select_strategy(estimated);
         let compressed = self.compressor.compress_batch(results, strategy);
 
+        let compressed_size: usize = compressed.iter().map(|c| c.text.as_ref().map_or(0, |t| t.len())).sum();
+        tracing::info!(
+            target: "observability",
+            event = "result_compress",
+            input_count = compressed.len(),
+            estimated_bytes = estimated,
+            compressed_bytes = compressed_size,
+            budget_bytes = self.max_budget_bytes,
+            strategy = ?strategy,
+            "Result compression complete"
+        );
+
         (compressed, strategy)
     }
 }