Add canonical previous-session artifact source parsing and validation

docs/config.md

@@ -249,6 +249,7 @@ Scriptorium artifact-key and dependency rules:
 Allowed `pipeline.scriptorium.artifacts.<name>.inputs.<key>.source` values:
 
 - `previous_session_artifact`
+- `narratio.previous_session.artifact.<configured_artifact_key>`
 - `narratio.transcript.merged`
 - `narratio.transcript.polished`
 - `narratio.transcript.full`

internal/artifacts/artifact_resolver.go

@@ -23,6 +23,7 @@ const (
 // ErrSessionArtifactNotFound is returned when no readable artifact exists for a known ID.
 var ErrSessionArtifactNotFound = errors.New("session artifact not found")
 var configuredArtifactSourceRE = regexp.MustCompile(`^narratio\.artifact\.[a-z][a-z0-9_]*$`)
+var previousSessionArtifactSourceRE = regexp.MustCompile(`^narratio\.previous_session\.artifact\.([a-z][a-z0-9_]*)$`)
 
 type artifactContentKind string
 
@@ -118,6 +119,21 @@ func IsConfiguredArtifactSource(source string) bool {
 	return configuredArtifactSourceRE.MatchString(strings.TrimSpace(source))
 }
 
+// IsPreviousSessionArtifactSource returns true when source is narratio.previous_session.artifact.<name>.
+func IsPreviousSessionArtifactSource(source string) bool {
+	_, ok := PreviousSessionArtifactName(source)
+	return ok
+}
+
+// PreviousSessionArtifactName extracts <name> from narratio.previous_session.artifact.<name>.
+func PreviousSessionArtifactName(source string) (string, bool) {
+	matches := previousSessionArtifactSourceRE.FindStringSubmatch(strings.TrimSpace(source))
+	if len(matches) != 2 {
+		return "", false
+	}
+	return matches[1], true
+}
+
 // ResolveSessionArtifact resolves a symbolic source to a readable local session artifact path.
 // Resolution order is manifest producer outputs first, then canonical session path fallback.
 func ResolveSessionArtifact(paths SessionPaths, m *manifest.Manifest, source string) (ResolvedSessionArtifact, error) {

internal/artifacts/artifact_resolver_test.go

@@ -45,6 +45,58 @@ func TestNormalizeSessionArtifactSource(t *testing.T) {
 	}
 }
 
+func TestPreviousSessionArtifactSourceHelpers(t *testing.T) {
+	tests := []struct {
+		name      string
+		source    string
+		wantName  string
+		wantMatch bool
+	}{
+		{
+			name:      "valid",
+			source:    "narratio.previous_session.artifact.session_recap",
+			wantName:  "session_recap",
+			wantMatch: true,
+		},
+		{
+			name:      "valid with surrounding whitespace",
+			source:    "  narratio.previous_session.artifact.quest_log  ",
+			wantName:  "quest_log",
+			wantMatch: true,
+		},
+		{
+			name:      "missing name",
+			source:    "narratio.previous_session.artifact.",
+			wantMatch: false,
+		},
+		{
+			name:      "invalid key characters",
+			source:    "narratio.previous_session.artifact.session-recap",
+			wantMatch: false,
+		},
+		{
+			name:      "wrong prefix",
+			source:    "narratio.previous.artifact.session_recap",
+			wantMatch: false,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			name, ok := PreviousSessionArtifactName(tt.source)
+			if ok != tt.wantMatch {
+				t.Fatalf("PreviousSessionArtifactName(%q) ok = %t, want %t", tt.source, ok, tt.wantMatch)
+			}
+			if name != tt.wantName {
+				t.Fatalf("PreviousSessionArtifactName(%q) name = %q, want %q", tt.source, name, tt.wantName)
+			}
+			if got := IsPreviousSessionArtifactSource(tt.source); got != tt.wantMatch {
+				t.Fatalf("IsPreviousSessionArtifactSource(%q) = %t, want %t", tt.source, got, tt.wantMatch)
+			}
+		})
+	}
+}
+
 func TestResolveSessionArtifactPrefersManifestOutput(t *testing.T) {
 	workspace := t.TempDir()
 	paths := buildSessionPaths(workspace, "campaign", "session")

internal/config/scriptorium_test.go

@@ -116,6 +116,75 @@ func TestScriptoriumLoadAndValidate(t *testing.T) {
         output_kind: session_recap
 `,
 		},
+		{
+			name: "canonical previous-session source is accepted",
+			scriptoriumYAML: `scriptorium:
+  binary: scriptorium
+  artifacts:
+    session_recap:
+      enabled: true
+      prompt_id: dnd.session_recap
+      output_path: artifacts/session_recap.md
+      inputs:
+        transcript:
+          source: narratio.transcript.polished
+          required: true
+        previous_recap:
+          source: narratio.previous_session.artifact.session_recap
+          required: false
+      vars:
+        session_id: true
+        output_kind: session_recap
+`,
+		},
+		{
+			name: "canonical previous-session source missing artifact key fails validation",
+			scriptoriumYAML: `scriptorium:
+  binary: scriptorium
+  artifacts:
+    session_recap:
+      enabled: true
+      prompt_id: dnd.session_recap
+      output_path: artifacts/session_recap.md
+      inputs:
+        previous_recap:
+          source: narratio.previous_session.artifact.
+          required: false
+`,
+			wantValidateErr: `pipeline.scriptorium.artifacts.session_recap.inputs.previous_recap.source "narratio.previous_session.artifact." must reference configured artifact key matching ^[a-z][a-z0-9_]*$`,
+		},
+		{
+			name: "canonical previous-session source invalid artifact key fails validation",
+			scriptoriumYAML: `scriptorium:
+  binary: scriptorium
+  artifacts:
+    session_recap:
+      enabled: true
+      prompt_id: dnd.session_recap
+      output_path: artifacts/session_recap.md
+      inputs:
+        previous_recap:
+          source: narratio.previous_session.artifact.session-recap
+          required: false
+`,
+			wantValidateErr: `pipeline.scriptorium.artifacts.session_recap.inputs.previous_recap.source "narratio.previous_session.artifact.session-recap" must reference configured artifact key matching ^[a-z][a-z0-9_]*$`,
+		},
+		{
+			name: "canonical previous-session source unknown artifact fails validation",
+			scriptoriumYAML: `scriptorium:
+  binary: scriptorium
+  artifacts:
+    session_recap:
+      enabled: true
+      prompt_id: dnd.session_recap
+      output_path: artifacts/session_recap.md
+      inputs:
+        previous_recap:
+          source: narratio.previous_session.artifact.quest_log
+          required: false
+`,
+			wantValidateErr: `pipeline.scriptorium.artifacts.session_recap.inputs.previous_recap.source "narratio.previous_session.artifact.quest_log" references unknown artifact "quest_log"`,
+		},
 		{
 			name: "canonical artifact source is accepted",
 			scriptoriumYAML: `scriptorium:

internal/config/validate.go

@@ -579,12 +579,38 @@ var windowsAbsPathRE = regexp.MustCompile(`^[A-Za-z]:[\\/].*`)
 var envVarNameRE = regexp.MustCompile(`^[A-Za-z_][A-Za-z0-9_]*$`)
 var scriptoriumArtifactKeyRE = regexp.MustCompile(`^[a-z][a-z0-9_]*$`)
 var narratioArtifactSourceRE = regexp.MustCompile(`^narratio\.artifact\.([a-z][a-z0-9_]*)$`)
+var narratioPreviousSessionArtifactSourceRE = regexp.MustCompile(`^narratio\.previous_session\.artifact\.([a-z][a-z0-9_]*)$`)
 
 func validateScriptoriumInputSource(artifactName, inputName, source string, configuredArtifacts map[string]struct{}) (string, error) {
-	if isStaticSupportedScriptoriumInputSource(source) {
+	trimmedSource := strings.TrimSpace(source)
+	if isStaticSupportedScriptoriumInputSource(trimmedSource) {
 		return "", nil
 	}
-	matches := narratioArtifactSourceRE.FindStringSubmatch(source)
+
+	if strings.HasPrefix(trimmedSource, "narratio.previous_session.artifact") {
+		matches := narratioPreviousSessionArtifactSourceRE.FindStringSubmatch(trimmedSource)
+		if len(matches) != 2 {
+			return "", fmt.Errorf(
+				"pipeline.scriptorium.artifacts.%s.inputs.%s.source %q must reference configured artifact key matching ^[a-z][a-z0-9_]*$",
+				artifactName,
+				inputName,
+				source,
+			)
+		}
+		referenced := matches[1]
+		if _, ok := configuredArtifacts[referenced]; !ok {
+			return "", fmt.Errorf(
+				"pipeline.scriptorium.artifacts.%s.inputs.%s.source %q references unknown artifact %q",
+				artifactName,
+				inputName,
+				source,
+				referenced,
+			)
+		}
+		return "", nil
+	}
+
+	matches := narratioArtifactSourceRE.FindStringSubmatch(trimmedSource)
 	if len(matches) != 2 {
 		return "", fmt.Errorf(
 			"pipeline.scriptorium.artifacts.%s.inputs.%s.source %q is unsupported",
@@ -607,7 +633,7 @@ func validateScriptoriumInputSource(artifactName, inputName, source string, conf
 }
 
 func isStaticSupportedScriptoriumInputSource(source string) bool {
-	switch strings.TrimSpace(source) {
+	switch source {
 	case "previous_session_artifact":
 		return true
 	case "narratio.transcript.merged":