fix(parser): bound Gemini reconciliation work

Rehydrate exact Gemini sources from the project hint captured during streamed discovery. This avoids rebuilding root-wide project metadata for every candidate after lost filesystem events.

Author: wesm

internal/parser/gemini_copilot_provider_test.go

@@ -87,6 +87,55 @@ func TestGeminiProviderSourceMethods(t *testing.T) {
 	require.Empty(t, fingerprint)
 }
 
+func TestGeminiProviderReconciliationProjectMapWorkIsArchiveBounded(t *testing.T) {
+	var projectMapBuilds int
+	orig := buildGeminiProjectMap
+	buildGeminiProjectMap = func(string) map[string]string {
+		projectMapBuilds++
+		return map[string]string{}
+	}
+	t.Cleanup(func() { buildGeminiProjectMap = orig })
+
+	for _, sourceCount := range []int{1, 64} {
+		t.Run(fmt.Sprintf("sources_%d", sourceCount), func(t *testing.T) {
+			root := t.TempDir()
+			sourcePaths := make([]string, sourceCount)
+			for i := range sourcePaths {
+				sourcePaths[i] = filepath.Join(
+					root,
+					"tmp",
+					fmt.Sprintf("project-hash-%03d", i),
+					geminiChatsDir,
+					fmt.Sprintf("session-2026-06-19T12-%02d-source.json", i),
+				)
+				writeSourceFile(t, sourcePaths[i], "{}")
+			}
+
+			provider, ok := NewProvider(AgentGemini, ProviderConfig{
+				Roots: []string{root},
+			})
+			require.True(t, ok)
+			resolver, ok := provider.(ReconciliationSourceResolver)
+			require.True(t, ok)
+
+			projectMapBuilds = 0
+			for i, path := range sourcePaths {
+				project := fmt.Sprintf("spooled_project_%d", i)
+				source, found, err := resolver.SourceForReconciliation(
+					t.Context(), path, project,
+				)
+				require.NoError(t, err)
+				require.True(t, found)
+				assert.Equal(t, path, source.DisplayPath)
+				assert.Equal(t, path, source.FingerprintKey)
+				assert.Equal(t, project, source.ProjectHint)
+			}
+			assert.Zero(t, projectMapBuilds,
+				"exact reconciliation must not rebuild root-wide metadata per source")
+		})
+	}
+}
+
 func TestGeminiProviderProjectMetadataChangesClassifyAndFingerprint(t *testing.T) {
 	root := t.TempDir()
 	sessionID := "gemini-project-metadata"

internal/parser/gemini_provider.go

@@ -66,6 +66,13 @@ func (p *geminiProvider) SourcesForChangedPath(
 	return p.sources.SourcesForChangedPath(ctx, req)
 }
 
+func (p *geminiProvider) SourceForReconciliation(
+	ctx context.Context,
+	path, project string,
+) (SourceRef, bool, error) {
+	return p.sources.SourceForReconciliation(ctx, path, project)
+}
+
 func (p *geminiProvider) FindSource(
 	ctx context.Context,
 	req FindSourceRequest,
@@ -498,6 +505,30 @@ func (s geminiSourceSet) sourceRef(root, path string) (SourceRef, bool) {
 	return s.sourceRefForPath(root, path, true)
 }
 
+// SourceForReconciliation rebuilds an exact source already admitted by
+// streaming discovery. The discovered project hint is authoritative here, so
+// rehydration must not rebuild root-wide Gemini project metadata per source.
+func (s geminiSourceSet) SourceForReconciliation(
+	ctx context.Context, path, project string,
+) (SourceRef, bool, error) {
+	if err := ctx.Err(); err != nil {
+		return SourceRef{}, false, err
+	}
+	for _, root := range s.roots {
+		source, ok := s.sourceRefForPathWithProjectMap(
+			root, path, true, map[string]string{},
+		)
+		if !ok {
+			continue
+		}
+		if project != "" {
+			source.ProjectHint = project
+		}
+		return source, true, nil
+	}
+	return SourceRef{}, false, nil
+}
+
 func (s geminiSourceSet) sourceRefForPath(
 	root, path string,
 	requireRegular bool,