merge: prompt-pillar verify output-tag preservation + render maxChars [FR-004]

dmealing · claude · dmealing · commit c99880b7eefa · 2026-05-23T17:24:35.000-04:00
@requiredTags static check (ERR_OUTPUT_TAG_MISSING) across TS/C#/Python via the
shared verify-conformance corpus; render() maxChars budget (TS). Java deferred.

Co-Authored-By: Claude Opus 4.7 (1M context) &lt;noreply@anthropic.com&gt;
diff --git a/fixtures/conformance/ERROR-CODES.json b/fixtures/conformance/ERROR-CODES.json
@@ -25,6 +25,7 @@
     "ERR_VAR_NOT_ON_PAYLOAD": "Build-time verify: a template variable references a field the (contextual) payload view-object does not declare.",
     "ERR_PARTIAL_UNRESOLVED": "Build-time verify: a template partial ({{> group/source}}) does not resolve in the configured provider.",
     "ERR_REQUIRED_SLOT_UNUSED": "Build-time verify (warning): a template's declared @requiredSlots slot is never referenced by the template text.",
+    "ERR_OUTPUT_TAG_MISSING": "Build-time verify: a template declares @requiredTags but its text (including provider-resolved partials) omits a required output tag's opening (<tag) or closing (</tag>) form. path = the tag name.",
     "ERR_BAD_ATTR_FILTER": "A dataGrid @filter references a non-filterable field or uses an op disallowed for the field's subtype.",
     "ERR_STORAGE_FLATTENED_ARRAY": "@storage \"flattened\" cannot be combined with isArray=true.",
     "ERR_STORAGE_WITHOUT_OBJECT_REF": "@storage was set on a field that has no @objectRef.",
diff --git a/fixtures/verify-conformance/verify-required-tag-in-partial/expected-drift.json b/fixtures/verify-conformance/verify-required-tag-in-partial/expected-drift.json
@@ -0,0 +1 @@
+[]
diff --git a/fixtures/verify-conformance/verify-required-tag-in-partial/options.json b/fixtures/verify-conformance/verify-required-tag-in-partial/options.json
@@ -0,0 +1 @@
+{ "requiredTags": ["answer"] }
diff --git a/fixtures/verify-conformance/verify-required-tag-in-partial/partials/answer.mustache b/fixtures/verify-conformance/verify-required-tag-in-partial/partials/answer.mustache
@@ -0,0 +1 @@
+<answer>{{content}}</answer>
diff --git a/fixtures/verify-conformance/verify-required-tag-in-partial/payload.json b/fixtures/verify-conformance/verify-required-tag-in-partial/payload.json
@@ -0,0 +1,3 @@
+[
+  { "name": "content" }
+]
diff --git a/fixtures/verify-conformance/verify-required-tag-in-partial/template.mustache b/fixtures/verify-conformance/verify-required-tag-in-partial/template.mustache
@@ -0,0 +1,2 @@
+Please respond.
+{{> partials/answer}}
diff --git a/fixtures/verify-conformance/verify-required-tag-missing-close/expected-drift.json b/fixtures/verify-conformance/verify-required-tag-missing-close/expected-drift.json
@@ -0,0 +1,3 @@
+[
+  { "code": "ERR_OUTPUT_TAG_MISSING", "path": "answer" }
+]
diff --git a/fixtures/verify-conformance/verify-required-tag-missing-close/options.json b/fixtures/verify-conformance/verify-required-tag-missing-close/options.json
@@ -0,0 +1 @@
+{ "requiredTags": ["answer"] }
diff --git a/fixtures/verify-conformance/verify-required-tag-missing-close/payload.json b/fixtures/verify-conformance/verify-required-tag-missing-close/payload.json
@@ -0,0 +1,3 @@
+[
+  { "name": "content" }
+]
diff --git a/fixtures/verify-conformance/verify-required-tag-missing-close/template.mustache b/fixtures/verify-conformance/verify-required-tag-missing-close/template.mustache
@@ -0,0 +1 @@
+<answer>{{content}}
diff --git a/fixtures/verify-conformance/verify-required-tag-missing-open/expected-drift.json b/fixtures/verify-conformance/verify-required-tag-missing-open/expected-drift.json
@@ -0,0 +1,3 @@
+[
+  { "code": "ERR_OUTPUT_TAG_MISSING", "path": "answer" }
+]
diff --git a/fixtures/verify-conformance/verify-required-tag-missing-open/options.json b/fixtures/verify-conformance/verify-required-tag-missing-open/options.json
@@ -0,0 +1 @@
+{ "requiredTags": ["answer"] }
diff --git a/fixtures/verify-conformance/verify-required-tag-missing-open/payload.json b/fixtures/verify-conformance/verify-required-tag-missing-open/payload.json
@@ -0,0 +1,3 @@
+[
+  { "name": "content" }
+]
diff --git a/fixtures/verify-conformance/verify-required-tag-missing-open/template.mustache b/fixtures/verify-conformance/verify-required-tag-missing-open/template.mustache
@@ -0,0 +1,2 @@
+Please respond. {{content}}
+</answer>
diff --git a/fixtures/verify-conformance/verify-required-tag-prefix-no-overmatch/expected-drift.json b/fixtures/verify-conformance/verify-required-tag-prefix-no-overmatch/expected-drift.json
@@ -0,0 +1,3 @@
+[
+  { "code": "ERR_OUTPUT_TAG_MISSING", "path": "answer" }
+]
diff --git a/fixtures/verify-conformance/verify-required-tag-prefix-no-overmatch/options.json b/fixtures/verify-conformance/verify-required-tag-prefix-no-overmatch/options.json
@@ -0,0 +1 @@
+{ "requiredTags": ["answer"] }
diff --git a/fixtures/verify-conformance/verify-required-tag-prefix-no-overmatch/payload.json b/fixtures/verify-conformance/verify-required-tag-prefix-no-overmatch/payload.json
@@ -0,0 +1,3 @@
+[
+  { "name": "content" }
+]
diff --git a/fixtures/verify-conformance/verify-required-tag-prefix-no-overmatch/template.mustache b/fixtures/verify-conformance/verify-required-tag-prefix-no-overmatch/template.mustache
@@ -0,0 +1 @@
+<answers>{{content}}</answers>
diff --git a/fixtures/verify-conformance/verify-required-tag-self-closing/expected-drift.json b/fixtures/verify-conformance/verify-required-tag-self-closing/expected-drift.json
@@ -0,0 +1,3 @@
+[
+  { "code": "ERR_OUTPUT_TAG_MISSING", "path": "answer" }
+]
diff --git a/fixtures/verify-conformance/verify-required-tag-self-closing/options.json b/fixtures/verify-conformance/verify-required-tag-self-closing/options.json
@@ -0,0 +1 @@
+{ "requiredTags": ["answer"] }
diff --git a/fixtures/verify-conformance/verify-required-tag-self-closing/payload.json b/fixtures/verify-conformance/verify-required-tag-self-closing/payload.json
@@ -0,0 +1,3 @@
+[
+  { "name": "content" }
+]
diff --git a/fixtures/verify-conformance/verify-required-tag-self-closing/template.mustache b/fixtures/verify-conformance/verify-required-tag-self-closing/template.mustache
@@ -0,0 +1,2 @@
+Please respond. {{content}}
+<answer/>
diff --git a/fixtures/verify-conformance/verify-required-tags-present/expected-drift.json b/fixtures/verify-conformance/verify-required-tags-present/expected-drift.json
@@ -0,0 +1 @@
+[]
diff --git a/fixtures/verify-conformance/verify-required-tags-present/options.json b/fixtures/verify-conformance/verify-required-tags-present/options.json
@@ -0,0 +1 @@
+{ "requiredTags": ["answer", "result"] }
diff --git a/fixtures/verify-conformance/verify-required-tags-present/payload.json b/fixtures/verify-conformance/verify-required-tags-present/payload.json
@@ -0,0 +1,3 @@
+[
+  { "name": "content" }
+]
diff --git a/fixtures/verify-conformance/verify-required-tags-present/template.mustache b/fixtures/verify-conformance/verify-required-tags-present/template.mustache
@@ -0,0 +1,2 @@
+<answer>{{content}}</answer>
+<result tone="warm">{{content}}</result>
diff --git a/server/csharp/MetaObjects.Cli.Tests/VerifyCommandTests.cs b/server/csharp/MetaObjects.Cli.Tests/VerifyCommandTests.cs
@@ -68,4 +68,21 @@ public void Unresolved_textref_fails()
         Assert.False(o.Ok);
         Assert.NotEmpty(o.UnresolvedText);
     }
+
+    [Fact]
+    public void Missing_required_tag_is_caught()
+    {
+        // Override the metadata with a template that contracts a <answer> output tag.
+        const string tagged = """
+        { "metadata.root": { "package": "acme::ai", "children": [
+          { "object.value": { "name": "Payload", "children": [ { "field.string": { "name": "name" } } ] } },
+          { "template.prompt": { "name": "greeting", "@payloadRef": "Payload", "@textRef": "t/main", "@requiredTags": ["answer"] } }
+        ]}}
+        """;
+        File.WriteAllText(Path.Combine(MetaDir, "meta.ai.json"), tagged);
+        WriteTemplate("Hi {{name}}."); // references the var cleanly but omits the <answer> tag
+        var o = VerifyCommand.Run(MetaDir, TplDir);
+        Assert.False(o.Ok);
+        Assert.Contains(o.Errors, d => d.Code == Render.Verify.ERR_OUTPUT_TAG_MISSING && d.Path == "answer");
+    }
 }
diff --git a/server/csharp/MetaObjects.Cli/VerifyCommand.cs b/server/csharp/MetaObjects.Cli/VerifyCommand.cs
@@ -30,6 +30,15 @@ public sealed record Outcome(
         public bool Ok => LoadErrors.Count == 0 && Errors.Count == 0 && UnresolvedText.Count == 0;
     }
 
+    /// <summary>Coerce a string-array attr (array, or a single string) into a string list.</summary>
+    private static IReadOnlyList<string> AsStringList(object? attr) => attr switch
+    {
+        IReadOnlyList<string> ss => ss.ToList(),
+        IReadOnlyList<object?> os => os.OfType<string>().ToList(),
+        string s => [s],
+        _ => [],
+    };
+
     public static Outcome Run(string metadataDir, string templatesRoot)
     {
         var load = new FileMetaDataLoader().LoadDirectory(metadataDir);
@@ -55,15 +64,15 @@ public static Outcome Run(string metadataDir, string templatesRoot)
             }
 
             var fields = PayloadCodegen.BuildPayloadFieldTree(load.Root, payloadRef);
-            IReadOnlyList<string> requiredSlots = tmpl.OwnAttr(TEMPLATE_ATTR_REQUIRED_SLOTS) switch
+            var requiredSlots = AsStringList(tmpl.OwnAttr(TEMPLATE_ATTR_REQUIRED_SLOTS));
+            var requiredTags = AsStringList(tmpl.OwnAttr(TEMPLATE_ATTR_REQUIRED_TAGS));
+
+            var verifyOptions = new VerifyOptions
             {
-                IReadOnlyList<string> ss => ss.ToList(),
-                IReadOnlyList<object?> os => os.OfType<string>().ToList(),
-                string s => [s],
-                _ => [],
+                Provider = provider,
+                RequiredSlots = requiredSlots,
+                RequiredTags = requiredTags,
             };
-
-            var verifyOptions = new VerifyOptions { Provider = provider, RequiredSlots = requiredSlots };
             foreach (var e in Verify.Check(text, fields, verifyOptions))
             {
                 var drift = new Drift(tmpl.Name, e.Code, e.Path);
diff --git a/server/csharp/MetaObjects.Render.Tests/VerifyConformanceTests.cs b/server/csharp/MetaObjects.Render.Tests/VerifyConformanceTests.cs
@@ -9,21 +9,22 @@ namespace MetaObjects.Render.Tests;
 ///   payload.json         the payload FIELD-TREE (PayloadField[], declared shape — not render data)
 ///   template.mustache    the template text whose vars are drift-checked
 ///   partials/*.mustache  optional partial bodies, referenced as `partials/&lt;name&gt;`
-///   options.json         optional { "requiredSlots"?: string[], "provider"?: "with" | "without" }
+///   options.json         optional { "requiredSlots"?, "requiredTags"?: string[], "provider"?: "with" | "without" }
 ///   expected-drift.json  array of { "code", "path" } findings (compared as a sorted multiset)
 /// The same (payload-tree + template + options) MUST yield the same drift set in TS and C#.
 /// Mirrors typescript/packages/render/test/verify-conformance.test.ts and the sibling
 /// RenderConformanceTests.cs.
 /// </summary>
 public class VerifyConformanceTests
 {
-    // The three stable verify codes a fixture may legitimately expect
+    // The stable verify codes a fixture may legitimately expect
     // (documented in fixtures/conformance/ERROR-CODES.json). Anything else is a typo.
     private static readonly HashSet<string> VerifyCodes = new(StringComparer.Ordinal)
     {
         Verify.ERR_VAR_NOT_ON_PAYLOAD,
         Verify.ERR_PARTIAL_UNRESOLVED,
         Verify.ERR_REQUIRED_SLOT_UNUSED,
+        Verify.ERR_OUTPUT_TAG_MISSING,
     };
 
     private static string CorpusRoot()
@@ -87,15 +88,18 @@ public void VerifyMatchesExpected(string name)
             File.ReadAllText(Path.Combine(dir, "payload.json"))).RootElement);
         var template = File.ReadAllText(Path.Combine(dir, "template.mustache"));
 
-        // options.json (optional): requiredSlots + provider toggle.
+        // options.json (optional): requiredSlots + requiredTags + provider toggle.
         string[]? requiredSlots = null;
+        string[]? requiredTags = null;
         string? providerMode = null;
         var optionsPath = Path.Combine(dir, "options.json");
         if (File.Exists(optionsPath))
         {
             var opts = JsonDocument.Parse(File.ReadAllText(optionsPath)).RootElement;
             if (opts.TryGetProperty("requiredSlots", out var rs) && rs.ValueKind == JsonValueKind.Array)
                 requiredSlots = rs.EnumerateArray().Select(e => e.GetString()!).ToArray();
+            if (opts.TryGetProperty("requiredTags", out var rt) && rt.ValueKind == JsonValueKind.Array)
+                requiredTags = rt.EnumerateArray().Select(e => e.GetString()!).ToArray();
             if (opts.TryGetProperty("provider", out var p) && p.ValueKind == JsonValueKind.String)
                 providerMode = p.GetString();
         }
@@ -115,7 +119,7 @@ public void VerifyMatchesExpected(string name)
         foreach (var e in expected)
             Assert.Contains(e.Code, VerifyCodes);
 
-        var options = new VerifyOptions { Provider = provider, RequiredSlots = requiredSlots };
+        var options = new VerifyOptions { Provider = provider, RequiredSlots = requiredSlots, RequiredTags = requiredTags };
         var actual = Verify.Check(template, fields, options);
 
         Assert.Equal(Sorted(expected), Sorted(actual));
diff --git a/server/csharp/MetaObjects.Render.Tests/VerifyTests.cs b/server/csharp/MetaObjects.Render.Tests/VerifyTests.cs
@@ -122,6 +122,54 @@ [Fact] public void Required_slot_unreferenced_warns() =>
     [Fact] public void Required_slot_via_section_counts_as_used() =>
         Assert.Empty(Verify.Check("{{#posts}}{{title}}{{/posts}}", AuthorBrief, new VerifyOptions { RequiredSlots = ["posts"] }));
 
+    // --- required output tags (@requiredTags) ---
+
+    private static readonly IReadOnlyList<PayloadField> Content = [new PayloadField("content")];
+
+    [Fact] public void No_required_tags_no_check() =>
+        Assert.Empty(Verify.Check("plain text, no tags", Content));
+
+    [Fact] public void Empty_required_tags_checks_nothing() =>
+        Assert.Empty(Verify.Check("plain text", Content, new VerifyOptions { RequiredTags = [] }));
+
+    [Fact] public void Tag_present_as_open_and_close_no_drift() =>
+        Assert.Empty(Verify.Check("<answer>{{content}}</answer>", Content, new VerifyOptions { RequiredTags = ["answer"] }));
+
+    [Fact] public void Opening_tag_may_carry_attributes() =>
+        Assert.Empty(Verify.Check("<answer tone=\"warm\">{{content}}</answer>", Content, new VerifyOptions { RequiredTags = ["answer"] }));
+
+    [Fact] public void Missing_open_tag_is_drift() =>
+        Assert.Equal(new VerifyError(Verify.ERR_OUTPUT_TAG_MISSING, "answer"),
+            Assert.Single(Verify.Check("{{content}}</answer>", Content, new VerifyOptions { RequiredTags = ["answer"] })));
+
+    [Fact] public void Missing_close_tag_is_drift() =>
+        Assert.Equal(new VerifyError(Verify.ERR_OUTPUT_TAG_MISSING, "answer"),
+            Assert.Single(Verify.Check("<answer>{{content}}", Content, new VerifyOptions { RequiredTags = ["answer"] })));
+
+    [Fact] public void Self_closing_tag_does_not_satisfy() =>
+        Assert.Equal(new VerifyError(Verify.ERR_OUTPUT_TAG_MISSING, "answer"),
+            Assert.Single(Verify.Check("<answer/>", Content, new VerifyOptions { RequiredTags = ["answer"] })));
+
+    [Fact] public void Open_tag_prefix_does_not_overmatch_longer_name() =>
+        Assert.Equal(new VerifyError(Verify.ERR_OUTPUT_TAG_MISSING, "answer"),
+            Assert.Single(Verify.Check("<answers>{{content}}</answers>", Content, new VerifyOptions { RequiredTags = ["answer"] })));
+
+    [Fact] public void Each_missing_tag_reported_independently() =>
+        Assert.Equal(new VerifyError(Verify.ERR_OUTPUT_TAG_MISSING, "reasoning"),
+            Assert.Single(Verify.Check("<answer>{{content}}</answer>", Content, new VerifyOptions { RequiredTags = ["answer", "reasoning"] })));
+
+    [Fact] public void Tag_supplied_by_resolved_partial_counts_as_present() =>
+        Assert.Empty(Verify.Check("{{> g/ans}}", Content,
+            new VerifyOptions { Provider = P(new() { ["g/ans"] = "<answer>{{content}}</answer>" }), RequiredTags = ["answer"] }));
+
+    [Fact] public void Tag_straddling_body_and_partial_boundary_is_satisfied() =>
+        Assert.Empty(Verify.Check("<answer>{{> g/close}}", Content,
+            new VerifyOptions { Provider = P(new() { ["g/close"] = "{{content}}</answer>" }), RequiredTags = ["answer"] }));
+
+    [Fact] public void Without_provider_tag_only_in_partial_is_missing() =>
+        Assert.Equal(new VerifyError(Verify.ERR_OUTPUT_TAG_MISSING, "answer"),
+            Assert.Single(Verify.Check("{{> g/ans}}", Content, new VerifyOptions { RequiredTags = ["answer"] })));
+
     // --- render verify-on-resolve guard (render.test.ts) ---
 
     private static readonly IReadOnlyList<PayloadField> Author =
diff --git a/server/csharp/MetaObjects.Render/Verify.cs b/server/csharp/MetaObjects.Render/Verify.cs
@@ -30,6 +30,13 @@ public sealed record VerifyOptions
     public IProvider? Provider { get; init; }
     /// <summary>Slots that MUST be referenced; an unused one is reported as a warning.</summary>
     public IReadOnlyList<string>? RequiredSlots { get; init; }
+    /// <summary>
+    /// Output tags the rendered text is contracted to contain. Each must appear as
+    /// both an opening form (<c>&lt;tag</c> followed by <c>&gt;</c> or whitespace, so
+    /// attributes are allowed) and a closing <c>&lt;/tag&gt;</c> — across the body AND
+    /// resolved partials.
+    /// </summary>
+    public IReadOnlyList<string>? RequiredTags { get; init; }
 }
 
 /// <summary>Template-side drift check against a payload field tree.</summary>
@@ -41,6 +48,8 @@ public static class Verify
     public const string ERR_PARTIAL_UNRESOLVED = "ERR_PARTIAL_UNRESOLVED";
     /// <summary>A declared @requiredSlots slot is never referenced by the template (warning).</summary>
     public const string ERR_REQUIRED_SLOT_UNUSED = "ERR_REQUIRED_SLOT_UNUSED";
+    /// <summary>A declared @requiredTags output tag is absent from the template text.</summary>
+    public const string ERR_OUTPUT_TAG_MISSING = "ERR_OUTPUT_TAG_MISSING";
 
     private const int MaxDepth = 32;
 
@@ -139,6 +148,10 @@ public static IReadOnlyList<VerifyError> Check(
         var provider = options?.Provider;
         var root = fields;
         var referencedAtRoot = new HashSet<string>(StringComparer.Ordinal);
+        // The static text the output-tag check scans: the body plus every
+        // provider-resolved partial body, collected during the single walk below
+        // (no second resolution pass).
+        var staticTexts = new List<string> { templateText };
 
         void Walk(IReadOnlyList<Tok> tokens, List<IReadOnlyList<PayloadField>> stack, List<string> seen)
         {
@@ -185,6 +198,7 @@ void Walk(IReadOnlyList<Tok> tokens, List<IReadOnlyList<PayloadField>> stack, Li
                             errors.Add(new VerifyError(ERR_PARTIAL_UNRESOLVED, p.Value));
                             break;
                         }
+                        staticTexts.Add(text);
                         Walk(Tokenize(text), stack, new List<string>(seen) { p.Value });
                         break;
                 }
@@ -197,6 +211,41 @@ void Walk(IReadOnlyList<Tok> tokens, List<IReadOnlyList<PayloadField>> stack, Li
             if (!referencedAtRoot.Contains(slot))
                 errors.Add(new VerifyError(ERR_REQUIRED_SLOT_UNUSED, slot));
 
+        var requiredTags = options?.RequiredTags ?? [];
+        if (requiredTags.Count > 0)
+        {
+            // Scan body + resolved partials as one joined string: the open and close
+            // forms are located independently, so a tag may legitimately straddle the
+            // boundary. The "\n" separator only blocks a spurious tag spliced together
+            // from two fragments (a real tag is always contiguous within one body).
+            var haystack = string.Join('\n', staticTexts);
+            foreach (var tag in requiredTags)
+                if (!HasOpenTag(haystack, tag) || !HasCloseTag(haystack, tag))
+                    errors.Add(new VerifyError(ERR_OUTPUT_TAG_MISSING, tag));
+        }
+
         return errors;
     }
+
+    // An opening tag is `<tag` immediately followed by `>` or XML whitespace, so
+    // attributes are allowed (`<answer foo="1">`) but a longer name is not over-matched
+    // (`<answers>` does not satisfy `answer`).
+    private static readonly char[] TagOpenDelims = ['>', ' ', '\t', '\n', '\r'];
+
+    private static bool HasOpenTag(string text, string tag)
+    {
+        var needle = "<" + tag;
+        for (int i = text.IndexOf(needle, StringComparison.Ordinal); i >= 0;
+             i = text.IndexOf(needle, i + 1, StringComparison.Ordinal))
+        {
+            int after = i + needle.Length;
+            if (after < text.Length && Array.IndexOf(TagOpenDelims, text[after]) >= 0) return true;
+        }
+        return false;
+    }
+
+    // A closing tag is the exact literal `</tag>`. A self-closing `<tag/>` has no such
+    // form, so it never satisfies a required tag — these wrap content a parser reads.
+    private static bool HasCloseTag(string text, string tag) =>
+        text.Contains("</" + tag + ">", StringComparison.Ordinal);
 }
diff --git a/server/csharp/MetaObjects/Template/TemplateConstants.cs b/server/csharp/MetaObjects/Template/TemplateConstants.cs
@@ -40,6 +40,10 @@ public static class TemplateConstants
     public const string TEMPLATE_ATTR_MAX_CHARS   = "maxChars";
     public const string TEMPLATE_ATTR_OWNER       = "owner";
     public const string TEMPLATE_ATTR_SINCE       = "since";
+    // Output tags the rendered text must contain (drives the verify output-tag check).
+    // Generic — not prompt-only: any rendered artifact (email, export, prompt) can
+    // carry a tag contract a downstream parser depends on.
+    public const string TEMPLATE_ATTR_REQUIRED_TAGS = "requiredTags";
 
     // Prompt-overlay attrs (template.prompt only).
     public const string TEMPLATE_ATTR_MAX_TOKENS     = "maxTokens";
diff --git a/server/csharp/MetaObjects/Template/TemplateSchema.cs b/server/csharp/MetaObjects/Template/TemplateSchema.cs
@@ -56,6 +56,12 @@ public static class TemplateSchema
             ValueType: AttrConstants.ATTR_SUBTYPE_STRING,
             Required: false,
             Description: "Governance: the version this template was introduced in."),
+
+        new AttrSchema(
+            Name: TemplateConstants.TEMPLATE_ATTR_REQUIRED_TAGS,
+            ValueType: AttrConstants.ATTR_SUBTYPE_STRINGARRAY,
+            Required: false,
+            Description: "Output tags the rendered text must contain (drives the verify output-tag check)."),
     ];
 
     // LLM-overlay attrs (template.prompt only).
diff --git a/server/python/src/metaobjects/errors.py b/server/python/src/metaobjects/errors.py
@@ -34,6 +34,7 @@ class ErrorCode(str, Enum):
     ERR_PARTIAL_UNRESOLVED = "ERR_PARTIAL_UNRESOLVED"
     ERR_REQUIRED_SLOT_UNUSED = "ERR_REQUIRED_SLOT_UNUSED"
     ERR_VAR_NOT_ON_PAYLOAD = "ERR_VAR_NOT_ON_PAYLOAD"
+    ERR_OUTPUT_TAG_MISSING = "ERR_OUTPUT_TAG_MISSING"
     ERR_UNKNOWN = "ERR_UNKNOWN"
 
 
diff --git a/server/python/src/metaobjects/render/__init__.py b/server/python/src/metaobjects/render/__init__.py
@@ -1,6 +1,7 @@
 """Render-tier engine (FR-004): the build-time template drift-check ``verify``."""
 
 from metaobjects.render.verify import (
+    ERR_OUTPUT_TAG_MISSING,
     ERR_PARTIAL_UNRESOLVED,
     ERR_REQUIRED_SLOT_UNUSED,
     ERR_VAR_NOT_ON_PAYLOAD,
@@ -12,6 +13,7 @@
 )
 
 __all__ = [
+    "ERR_OUTPUT_TAG_MISSING",
     "ERR_PARTIAL_UNRESOLVED",
     "ERR_REQUIRED_SLOT_UNUSED",
     "ERR_VAR_NOT_ON_PAYLOAD",
diff --git a/server/python/src/metaobjects/render/verify.py b/server/python/src/metaobjects/render/verify.py
diff --git a/server/python/tests/render/test_verify.py b/server/python/tests/render/test_verify.py
diff --git a/server/python/tests/render/test_verify_conformance.py b/server/python/tests/render/test_verify_conformance.py
diff --git a/server/typescript/packages/cli/src/commands/verify.ts b/server/typescript/packages/cli/src/commands/verify.ts
diff --git a/server/typescript/packages/cli/test/integration/verify.test.ts b/server/typescript/packages/cli/test/integration/verify.test.ts
diff --git a/server/typescript/packages/metadata/src/errors.ts b/server/typescript/packages/metadata/src/errors.ts
diff --git a/server/typescript/packages/metadata/src/template/template-constants.ts b/server/typescript/packages/metadata/src/template/template-constants.ts
diff --git a/server/typescript/packages/metadata/src/template/template-schema.ts b/server/typescript/packages/metadata/src/template/template-schema.ts
diff --git a/server/typescript/packages/metadata/test/template.test.ts b/server/typescript/packages/metadata/test/template.test.ts
diff --git a/server/typescript/packages/render/src/index.ts b/server/typescript/packages/render/src/index.ts
diff --git a/server/typescript/packages/render/src/render.ts b/server/typescript/packages/render/src/render.ts
diff --git a/server/typescript/packages/render/src/verify.ts b/server/typescript/packages/render/src/verify.ts
diff --git a/server/typescript/packages/render/test/render.test.ts b/server/typescript/packages/render/test/render.test.ts
diff --git a/server/typescript/packages/render/test/verify-conformance.test.ts b/server/typescript/packages/render/test/verify-conformance.test.ts
diff --git a/server/typescript/packages/render/test/verify.test.ts b/server/typescript/packages/render/test/verify.test.ts

Original file line number	Diff line number	Diff line change
`@@ -0,0 +1,2 @@`
	`1`	`+Please respond.`
	`2`	`+{{> partials/answer}}`
Original file line number	Diff line number	Diff line change
`@@ -0,0 +1,3 @@`
	`1`	`+[`
	`2`	`+ { "code": "ERR_OUTPUT_TAG_MISSING", "path": "answer" }`
	`3`	`+]`