Preserve explicit worker counts when normalizing keys

docs/roadmap/remediation.md

@@ -100,6 +100,9 @@ chunk/extract/merge/normalize and valid reference forms remain accepted.
 
 ## Finding 3 — Restore Worker-Key Normalization Without Losing Explicitness
 
+Status: Addressed. Worker keys normalize before defaulting; original input
+presence preserves explicit counts. Regression tests cover defaults and collisions.
+
 Priority: P2. The migration introduced an unplanned restriction.
 
 The former `normalizeStageWorkers` trimmed keys and rejected normalized

internal/core/config/operational_document.go

@@ -18,7 +18,12 @@ func resolveDocumentOperations(document *Document, resolution *configkit.Resolut
 	normalizeDocumentState(document, resolution)
 	normalizeDocumentPipelines(document, resolution, state)
 	normalizeDocumentPaths(document, resolution, state)
-	deriveDocumentExtractWorkers(document, resolution)
+	if document.Concurrency != nil {
+		document.Concurrency.StageWorkers = normalizeDocumentMap(document.Concurrency.StageWorkers,
+			configkit.Keys("concurrency", "stage_workers"), "stage worker identifier",
+			documentNormalizer{Resolution: resolution}, state)
+	}
+	deriveDocumentExtractWorkers(document, resolution, state)
 	return nil
 }
 
@@ -74,7 +79,7 @@ func normalizeDocumentString(resolution *configkit.Resolution, path configkit.Pa
 	configkit.Normalize(resolution, path, target, documentValue(strings.TrimSpace(**target)), reason)
 }
 
-func deriveDocumentExtractWorkers(document *Document, resolution *configkit.Resolution) {
+func deriveDocumentExtractWorkers(document *Document, resolution *configkit.Resolution, state *documentLoadState) {
 	if document.Concurrency == nil || document.Concurrency.TotalLLM == nil {
 		return
 	}
@@ -82,6 +87,11 @@ func deriveDocumentExtractWorkers(document *Document, resolution *configkit.Reso
 		document.Concurrency.StageWorkers = make(map[string]int)
 	}
 	path := configkit.Keys("concurrency", "stage_workers", "extract")
+	// Presence belongs to the input spelling, not the key produced by trimming.
+	// A moved explicit count must never be replaced by a derived default.
+	if resolution.IsExplicit(state.originalPath(path)) {
+		return
+	}
 	workers := document.Concurrency.StageWorkers
 	value := workers["extract"]
 	configkit.Default(resolution, path, &value, *document.Concurrency.TotalLLM,

internal/core/config/operational_document_test.go

@@ -1,14 +1,54 @@
 package config
 
 import (
+	"bytes"
 	"errors"
 	"os"
 	"path/filepath"
+	"strings"
 	"testing"
 
 	configkit "gitea.maximumdirect.net/eric/ConfigKit"
 )
 
+func TestWorkerKeyNormalizationPreservesExplicitCount(t *testing.T) {
+	t.Parallel()
+	for _, test := range []struct {
+		name, workers string
+		want          int
+		errorPath     string
+	}{
+		{name: "omitted", workers: "{}", want: 4},
+		{name: "padded", workers: "{' extract ': 2}", want: 2},
+		{name: "explicit invalid", workers: "{' extract ': 0}", errorPath: "/concurrency/stage_workers/extract"},
+		{name: "collision", workers: "{' extract ': 2, extract: 3}", errorPath: "/concurrency/stage_workers/extract"},
+	} {
+		t.Run(test.name, func(t *testing.T) {
+			loaded, err := loadConfigSource(configkit.Bytes("workers.yml", []byte(
+				"version: 5\nconcurrency:\n  total_llm: 4\n  stage_workers: "+test.workers+"\n")), LoadOptions{})
+			if test.errorPath != "" {
+				assertDocumentDiagnosticAt(t, err, test.errorPath)
+				return
+			}
+			if err != nil {
+				t.Fatal(err)
+			}
+			if got := loaded.Config.Concurrency.StageWorkers["extract"]; got != test.want {
+				t.Fatalf("workers = %d, want %d", got, test.want)
+			}
+			var explanation bytes.Buffer
+			if err := loaded.WriteExplanation(&explanation, "/concurrency/stage_workers"); err != nil {
+				t.Fatal(err)
+			}
+			if test.name == "padded" && (!strings.Contains(explanation.String(), "normalization") ||
+				!strings.Contains(explanation.String(), " extract ") ||
+				strings.Contains(explanation.String(), "derived extraction workers")) {
+				t.Fatalf("explicit worker provenance = %s", explanation.String())
+			}
+		})
+	}
+}
+
 func TestDocumentLoadAppliesOperationalDefaultsAndNormalization(t *testing.T) {
 	t.Parallel()