diff --git a/crates/grund-cli/tests/e2e.rs b/crates/grund-cli/tests/e2e.rs
index aaa094631..d65122173 100644
--- a/crates/grund-cli/tests/e2e.rs
+++ b/crates/grund-cli/tests/e2e.rs
@@ -8,6 +8,9 @@ mod case_runner;
 #[path = "support/chapter_rule_workflow.rs"]
 mod chapter_rule_workflow;
 
+#[path = "support/chapter_diagnostics.rs"]
+mod chapter_diagnostics;
+
 use case_runner::CaseKind::{E2e, Example};
 use case_runner::{
     assert_case_is_deterministic, assert_every_case_passed, discover_e2e_cases, discover_examples,
diff --git a/crates/grund-cli/tests/rules_contract/authority.rs b/crates/grund-cli/tests/rules_contract/authority.rs
index ba422e394..89ca66e13 100644
--- a/crates/grund-cli/tests/rules_contract/authority.rs
+++ b/crates/grund-cli/tests/rules_contract/authority.rs
@@ -216,7 +216,7 @@ fn a_should_level_sentence_needs_suggestions_to_be_seen() {
         ),
         0,
         "docs/fs/FS-demo.md:1: suggestion: FS-demo has 0 security chapters; \
-         --rule requires exactly one\n",
+         --rule requires exactly one; expected display name \"security\" (case-insensitive, not section handle); observed direct chapters: \"goals: Goals\", \"requirements: Requirements\"\n",
         "",
     );
 }
diff --git a/crates/grund-cli/tests/rules_contract/refusals.rs b/crates/grund-cli/tests/rules_contract/refusals.rs
index ae1ca45e8..351c13aee 100644
--- a/crates/grund-cli/tests/rules_contract/refusals.rs
+++ b/crates/grund-cli/tests/rules_contract/refusals.rs
@@ -63,7 +63,7 @@ fn every_listed_refusal_has_its_exact_rewrite_and_exit_two() {
         ),
         (
             "Each FS must have exactly one  chapter.",
-            "chapter name must be a non-empty NAME with no surrounding whitespace; accepted form: Each FS must have exactly one requirements chapter.",
+            "chapter name must be a non-empty NAME with no surrounding whitespace; accepted form: Each FS must have exactly one requirements chapter. NAME forbids whitespace anywhere.",
         ),
         (
             "Each FS must cite at least one GOAL",
diff --git a/crates/grund-cli/tests/rules_contract/regressions.rs b/crates/grund-cli/tests/rules_contract/regressions.rs
index 6a9c23ca8..9adeb8cf0 100644
--- a/crates/grund-cli/tests/rules_contract/regressions.rs
+++ b/crates/grund-cli/tests/rules_contract/regressions.rs
@@ -26,7 +26,7 @@ fn chapter_handles_and_display_names_have_distinct_meanings() {
     assert_run(
         &output,
         1,
-        "docs/fs/FS-demo.md:1: error: FS-demo has 0 requirements chapters; --rule requires exactly one\n",
+        "docs/fs/FS-demo.md:1: error: FS-demo has 0 requirements chapters; --rule requires exactly one; expected display name \"requirements\" (case-insensitive, not section handle); observed direct chapters: \"requirements: Acceptance criteria\"\n",
         "",
     );
     let output = run(&root, &["list", ".", "--selector", "FS.requirements"]);
diff --git a/crates/grund-cli/tests/rules_contract/surfaces.rs b/crates/grund-cli/tests/rules_contract/surfaces.rs
index 73b80d3cd..7377fdda2 100644
--- a/crates/grund-cli/tests/rules_contract/surfaces.rs
+++ b/crates/grund-cli/tests/rules_contract/surfaces.rs
@@ -53,7 +53,7 @@ fn ad_hoc_rule_is_additive_and_suggestions_do_not_change_the_exit() {
         &["check", ".", "--rule", sentence, "--suggestions"],
     );
     let expected = format!(
-        "{TEXT_FINDINGS}docs/fs/FS-demo.md:1: suggestion: FS-demo has 0 security chapters; --rule requires exactly one\n"
+        "{TEXT_FINDINGS}docs/fs/FS-demo.md:1: suggestion: FS-demo has 0 security chapters; --rule requires exactly one; expected display name \"security\" (case-insensitive, not section handle); observed direct chapters: \"goals: Goals\", \"requirements: Requirements\"\n"
     );
     assert_run(&output, 1, &expected, "");
 }
diff --git a/crates/grund-cli/tests/support/chapter_diagnostics.rs b/crates/grund-cli/tests/support/chapter_diagnostics.rs
new file mode 100644
index 000000000..44392f293
--- /dev/null
+++ b/crates/grund-cli/tests/support/chapter_diagnostics.rs
@@ -0,0 +1,36 @@
+//! Chapter diagnostic regressions for §FS-rules.7.2.1 and §FS-rules.3.5.1.
+//! The unchanged-selector controls prove the goal chapter is actually reached.
+
+use super::case_runner::{CaseKind::E2e, assert_every_case_passed, run_case};
+use super::repo_root;
+
+fn case(name: &str) {
+    let root = repo_root();
+    let path = root.join("tests/e2e/cases").join(name);
+    assert_every_case_passed(name, &[run_case(&root, &path, E2e)]);
+}
+
+/// §FS-rules.7.2.1, §FS-errors.3: old bytes plus display-name context in text.
+#[test]
+fn chapter_diagnostic_display_name_text() {
+    case("check-chapter-diagnostic-display-name-text");
+}
+
+/// §FS-rules.7.2.1: preserve every JSON field while explaining the zero count.
+#[test]
+fn chapter_diagnostic_display_name_json() {
+    case("check-chapter-diagnostic-display-name-json");
+}
+
+/// §FS-rules.3.5.1: keep the full refusal prefix and explain internal whitespace.
+#[test]
+fn chapter_diagnostic_whitespace_refusal() {
+    case("check-chapter-diagnostic-whitespace-refusal");
+}
+
+/// §FS-rules.2: a chapter subject selects the handle despite its display title.
+#[test]
+fn chapter_diagnostic_handle_subject_reaches_citation() {
+    case("check-chapter-diagnostic-handle-subject");
+    case("check-chapter-diagnostic-handle-subject-missing-citation");
+}
diff --git a/crates/grund-core/assets/skills/grund-init/SKILL.md b/crates/grund-core/assets/skills/grund-init/SKILL.md
index 09990cc73..10d0ab86b 100644
--- a/crates/grund-core/assets/skills/grund-init/SKILL.md
+++ b/crates/grund-core/assets/skills/grund-init/SKILL.md
@@ -618,6 +618,8 @@ Subjects select local units only:
 - `The requirements chapter of each FS` selects that named chapter in every FS.
 - `FS-login.requirements` selects one exact named chapter.
 
+Named chapter subjects select handles: `The goal chapter of each FS` reaches `## goal: Goal and hypothesis` by `goal` ([chapter subjects](https://github.com/agent-grounds/grund/blob/main/docs/functional-spec/FS-rules.md#2-subject-selectors)). Presence rules compare direct chapter display names case-insensitively: `Each FS must have exactly one goal chapter.` counts zero for that heading and one for `## goal: Goal` ([presence matching](https://github.com/agent-grounds/grund/blob/main/docs/functional-spec/FS-rules.md#31-chapter-presence)). The finding appends the expected display name and observed pairs such as `"goal: Goal and hypothesis"`, or `none` ([comparison context](https://github.com/agent-grounds/grund/blob/main/docs/functional-spec/FS-rules.md#721-display-name-comparison-context)). Presence `NAME` must be one non-empty token: `Goal and hypothesis` is refused with `NAME forbids whitespace anywhere.` appended to the existing guidance; authored display titles may still contain spaces ([whitespace refusal](https://github.com/agent-grounds/grund/blob/main/docs/functional-spec/FS-rules.md#351-presence-name-whitespace-refusal)).
+
 Named-chapter subjects require `[id] named_sections = true`. Phase 1 has no
 paths, files, folders, wildcards, subject namespaces, numbered-chapter subjects,
 exceptions, definitions, derived terms, settings, or source-code symbols.
@@ -704,7 +706,7 @@ Common refusals are intentional and name the exact accepted rewrite:
 - `Each FS must cite at least 1 GOAL.` → `numeric "at least 1" is not canonical; accepted form: Each FS must cite at least one GOAL.`
 - `Each FS must cite exactly 1 GOAL.` → `numeric "exactly 1" is not canonical; accepted form: Each FS must cite exactly one GOAL.`
 - `Each FS must cite at least one GOAL and must not cite any AR.` → `conjunctions are not accepted; accepted forms: "Each FS must cite at least one GOAL." and "Each FS must not cite any AR."`
-- `Each FS must have exactly one  chapter.` → `chapter name must be a non-empty NAME with no surrounding whitespace; accepted form: Each FS must have exactly one requirements chapter.`
+- `Each FS must have exactly one  chapter.` → `chapter name must be a non-empty NAME with no surrounding whitespace; accepted form: Each FS must have exactly one requirements chapter. NAME forbids whitespace anywhere.`
 - `Each FS must cite at least one GOAL` → `rule must end with "."; accepted form: Each FS must cite at least one GOAL.`
 - `each FS must cite at least one GOAL.` → `fixed word "Each" is case-sensitive; accepted form: Each FS must cite at least one GOAL.`
 - `Each file in vendor/ must cite at least one FS.` → `path subjects are not accepted in phase 1; accepted form: Each FS must cite at least one GOAL.`
diff --git a/crates/grund-core/src/rules/engine.rs b/crates/grund-core/src/rules/engine.rs
index 0c2a2be87..c0eae4784 100644
--- a/crates/grund-core/src/rules/engine.rs
+++ b/crates/grund-core/src/rules/engine.rs
@@ -137,19 +137,40 @@ fn evaluate_one(
                 return;
             };
             for subject in subjects {
-                let count = index
-                    .chapters_of(&subject)
+                let chapters = index.chapters_of(&subject);
+                let count = chapters
                     .iter()
                     .filter(|row| facts.chapter[**row].2.eq_ignore_ascii_case(name))
                     .count();
                 if !rule.cardinality.contains(count) {
+                    // §FS-rules.7.2.1: show accepted direct chapters in source order,
+                    // retaining the complete released prefix (§FS-errors.3).
+                    let mut observed = chapters.to_vec();
+                    observed.sort_by_key(|row| {
+                        facts
+                            .nodes
+                            .get(&facts.chapter[*row].0)
+                            .map(|meta| meta.anchor.line)
+                    });
+                    let observed = if observed.is_empty() {
+                        "none".to_string()
+                    } else {
+                        observed
+                            .iter()
+                            .map(|row| {
+                                let (_, coordinate, display_name) = &facts.chapter[*row];
+                                format!("\"{coordinate}: {display_name}\"")
+                            })
+                            .collect::<Vec<_>>()
+                            .join(", ")
+                    };
                     push_node(
                         out,
                         facts,
                         &subject,
                         "chapter-cardinality",
                         format!(
-                            "{} has {count} {name} chapters; {authority} requires {}",
+                            "{} has {count} {name} chapters; {authority} requires {}; expected display name \"{name}\" (case-insensitive, not section handle); observed direct chapters: {observed}",
                             label(facts, &subject),
                             rule.cardinality.wording()
                         ),
diff --git a/crates/grund-core/src/rules/sentence.rs b/crates/grund-core/src/rules/sentence.rs
index d2b2eb654..7b6b3e793 100644
--- a/crates/grund-core/src/rules/sentence.rs
+++ b/crates/grund-core/src/rules/sentence.rs
@@ -267,8 +267,9 @@ fn parse_predicate(
             ));
         };
         if name.is_empty() || name.trim() != name || name.chars().any(char::is_whitespace) {
+            // §FS-rules.3.5.1: append whitespace guidance to the released refusal prefix.
             return Err(error(
-                "chapter name must be a non-empty NAME with no surrounding whitespace; accepted form: Each FS must have exactly one requirements chapter.",
+                "chapter name must be a non-empty NAME with no surrounding whitespace; accepted form: Each FS must have exactly one requirements chapter. NAME forbids whitespace anywhere.",
             ));
         }
         let expects_plural = match spelling {
diff --git a/crates/grund-core/src/rules/tests_boundaries.rs b/crates/grund-core/src/rules/tests_boundaries.rs
index 1640390d8..1392d5368 100644
--- a/crates/grund-core/src/rules/tests_boundaries.rs
+++ b/crates/grund-core/src/rules/tests_boundaries.rs
@@ -35,6 +35,43 @@ fn rule() -> ParsedRule {
     }
 }
 
+/// §FS-rules.3.5.1, §FS-errors.3: whitespace at any position remains refused,
+/// with the entire released reason followed by actionable guidance.
+#[test]
+fn chapter_diagnostic_parser_refuses_whitespace_anywhere_in_presence_name() {
+    let vocabulary = RuleVocabulary {
+        kinds: BTreeSet::from(["FS".into()]),
+        target_kinds: BTreeSet::from(["FS".into()]),
+        target_namespaces: BTreeMap::new(),
+        named_sections: true,
+        id_grammars: Vec::new(),
+        section_separators: vec![".".into()],
+    };
+    let expected = concat!(
+        "chapter name must be a non-empty NAME with no surrounding whitespace; ",
+        "accepted form: Each FS must have exactly one requirements chapter.",
+        " NAME forbids whitespace anywhere."
+    );
+    for name in [
+        "Goal and hypothesis",
+        "Goal\tand",
+        "Goal\u{a0}and",
+        " goal",
+        "goal ",
+        "",
+    ] {
+        let sentence = format!("Each FS must have exactly one {name} chapter.");
+        let refusal = parse_rule(
+            &sentence,
+            "RULE-presence".into(),
+            anchor("docs/rules.md", 1),
+            &vocabulary,
+        )
+        .expect_err("presence NAME with whitespace or no token stays refused");
+        assert_eq!(refusal.message, expected, "presence NAME {name:?}");
+    }
+}
+
 fn facts(completeness: Completeness) -> RuleFacts {
     let fs = NodeKey("opaque-fs".into());
     let goal = NodeKey("opaque-goal".into());
diff --git a/docs/functional-spec/FS-rules.md b/docs/functional-spec/FS-rules.md
index 0232f29f3..159db8037 100644
--- a/docs/functional-spec/FS-rules.md
+++ b/docs/functional-spec/FS-rules.md
@@ -73,6 +73,11 @@ The four accepted subject spellings are:
 | `The NAME chapter of each KIND` | that named chapter of every local declaration of the kind that has one |
 | `ID.NAME[.NAME…]` | the one local named chapter with that exact coordinate |
 
+In chapter subjects, `NAME` selects the section handle, not its display name.
+For `## goal: Goal and hypothesis`, `The goal chapter of each BENCH` selects
+the `goal` coordinate even though its display name is `Goal and hypothesis`.
+Presence rules compare the other field ([§FS-rules.3.1](FS-rules.md#31-chapter-presence)).
+
 A token exactly equal to a configured citable kind name is the quantified kind
 selector; any longer token must parse as a full ID under that kind's effective
 grammar. Named components require `[id] named_sections = true` and obey the
@@ -135,6 +140,12 @@ spelling of a ceiling of one. The only accepted families are the following.
 The subject may be a kind or exact declaration, not a chapter. The rule counts
 the subject declaration's accepted direct chapters whose display name is
 `NAME`. A count outside the stated interval produces `chapter-cardinality`.
+The comparison is case-insensitive and does not match section handles: a direct
+`## goal: Goal and hypothesis` chapter contributes zero to a presence rule for
+`goal`, while `## goal: Goal` contributes one. Presence `NAME` is a non-empty
+single token with no whitespace anywhere; the multi-word display name `Goal
+and hypothesis` cannot be used as a presence `NAME`. This restriction does not
+restrict authored display titles or change chapter-subject selection.
 This family is how a repository states the *count* of a chapter — `exactly
 one`, `at most N` — which no citation rule checks. A chapter-scoped citation
 rule reaches a declaration that has no such chapter on its own
@@ -226,6 +237,21 @@ least these exact rows:
 is not a pre-scan refusal. After scanning it produces the exact resolution
 message `literal subject FS-missing does not resolve` ([§FS-rules.4](FS-rules.md#4-validation-lifecycle)).
 
+#### 3.5.1 Presence-name whitespace refusal
+
+A presence `NAME` containing whitespace anywhere, including internal spaces,
+tabs, and Unicode whitespace, remains refused. The whole released reason,
+including its accepted-form example, remains a verbatim contiguous prefix under
+[§FS-errors.3](FS-errors.md#3-message-text); append the explanation:
+
+```text
+chapter name must be a non-empty NAME with no surrounding whitespace; accepted form: Each FS must have exactly one requirements chapter. NAME forbids whitespace anywhere.
+```
+
+An empty `NAME` uses the same refusal. This adds guidance without admitting any
+new grammar. An ad-hoc refusal still writes nothing to stdout and exits 2
+([§FS-rules.4](FS-rules.md#4-validation-lifecycle)).
+
 ## 4. Validation lifecycle
 
 `config validate` validates only the optional `rules` key and its relationship
@@ -526,6 +552,28 @@ zero and surplus chapters:
 <subject> has <actual> <name> chapters; <RULE-ID> requires <count>
 ```
 
+#### 7.2.1 Display-name comparison context
+
+Keep the complete message above as a verbatim contiguous prefix
+([§FS-errors.3](FS-errors.md#3-message-text)) and append:
+
+```text
+; expected display name "<name>" (case-insensitive, not section handle); observed direct chapters: <observed>
+```
+
+`<observed>` lists every accepted direct chapter in source order, each quoted
+as `"<coordinate>: <display name>"`, separated by `, `; when there are none it
+is `none`. Named coordinates expose the handle alongside the authored display
+name, so the reported example ends in `"goal: Goal and hypothesis"` rather
+than implying that the accepted chapter was not scanned. Nested descendants
+and rejected headings do not enter this direct-chapter list or the count.
+
+Text output and JSON `message` carry the same complete explanation. The code,
+subject-title location, authority, severity/channel, other finding fields and
+exit verdict stay unchanged. The rule guide states this display-name/handle
+distinction beside its presence and chapter-subject examples and explains the
+single-token presence `NAME` restriction using `goal: Goal and hypothesis`.
+
 ### 7.3 Outbound citation cardinality
 
 An ordinary hard `at least one` rule with zero matches reuses
diff --git a/docs/user-facing/rules.md b/docs/user-facing/rules.md
index f932bad53..6004bce4e 100644
--- a/docs/user-facing/rules.md
+++ b/docs/user-facing/rules.md
@@ -28,6 +28,12 @@ This keeps requirements tied to authority, because §GOAL-grounded-rules.
 The title is a grammar island: formatting never inserts markers, links, or
 expanded shorthand into it. The rationale remains ordinary grounded Markdown.
 
+The shared guide below explains handle selection ([§FS-rules.2](../functional-spec/FS-rules.md#2-subject-selectors)),
+display-name matching ([§FS-rules.3.1](../functional-spec/FS-rules.md#31-chapter-presence)),
+comparison diagnostics ([§FS-rules.7.2.1](../functional-spec/FS-rules.md#721-display-name-comparison-context))
+and whitespace guidance ([§FS-rules.3.5.1](../functional-spec/FS-rules.md#351-presence-name-whitespace-refusal)).
+Its shipped skill copies use public links ([§REQ-shipped-surfaces.2](../requirements/REQ-shipped-surfaces.md#2-the-grounding-moves-it-is-not-deleted)).
+
 <!-- BEGIN chapter-rules -->
 ### Chapter rules
 
@@ -44,6 +50,8 @@ Subjects select local units only:
 - `The requirements chapter of each FS` selects that named chapter in every FS.
 - `FS-login.requirements` selects one exact named chapter.
 
+Named chapter subjects select handles: `The goal chapter of each FS` reaches `## goal: Goal and hypothesis` by `goal` ([chapter subjects](https://github.com/agent-grounds/grund/blob/main/docs/functional-spec/FS-rules.md#2-subject-selectors)). Presence rules compare direct chapter display names case-insensitively: `Each FS must have exactly one goal chapter.` counts zero for that heading and one for `## goal: Goal` ([presence matching](https://github.com/agent-grounds/grund/blob/main/docs/functional-spec/FS-rules.md#31-chapter-presence)). The finding appends the expected display name and observed pairs such as `"goal: Goal and hypothesis"`, or `none` ([comparison context](https://github.com/agent-grounds/grund/blob/main/docs/functional-spec/FS-rules.md#721-display-name-comparison-context)). Presence `NAME` must be one non-empty token: `Goal and hypothesis` is refused with `NAME forbids whitespace anywhere.` appended to the existing guidance; authored display titles may still contain spaces ([whitespace refusal](https://github.com/agent-grounds/grund/blob/main/docs/functional-spec/FS-rules.md#351-presence-name-whitespace-refusal)).
+
 Named-chapter subjects require `[id] named_sections = true`. Phase 1 has no
 paths, files, folders, wildcards, subject namespaces, numbered-chapter subjects,
 exceptions, definitions, derived terms, settings, or source-code symbols.
@@ -130,7 +138,7 @@ Common refusals are intentional and name the exact accepted rewrite:
 - `Each FS must cite at least 1 GOAL.` → `numeric "at least 1" is not canonical; accepted form: Each FS must cite at least one GOAL.`
 - `Each FS must cite exactly 1 GOAL.` → `numeric "exactly 1" is not canonical; accepted form: Each FS must cite exactly one GOAL.`
 - `Each FS must cite at least one GOAL and must not cite any AR.` → `conjunctions are not accepted; accepted forms: "Each FS must cite at least one GOAL." and "Each FS must not cite any AR."`
-- `Each FS must have exactly one  chapter.` → `chapter name must be a non-empty NAME with no surrounding whitespace; accepted form: Each FS must have exactly one requirements chapter.`
+- `Each FS must have exactly one  chapter.` → `chapter name must be a non-empty NAME with no surrounding whitespace; accepted form: Each FS must have exactly one requirements chapter. NAME forbids whitespace anywhere.`
 - `Each FS must cite at least one GOAL` → `rule must end with "."; accepted form: Each FS must cite at least one GOAL.`
 - `each FS must cite at least one GOAL.` → `fixed word "Each" is case-sensitive; accepted form: Each FS must cite at least one GOAL.`
 - `Each file in vendor/ must cite at least one FS.` → `path subjects are not accepted in phase 1; accepted form: Each FS must cite at least one GOAL.`
diff --git a/examples/rules/expected.stdout b/examples/rules/expected.stdout
index f2625f994..7993b29b1 100644
--- a/examples/rules/expected.stdout
+++ b/examples/rules/expected.stdout
@@ -1,6 +1,6 @@
 docs/ar/AR-overview.md:3: error: AR-overview.system-overview cites AR-one 2 times; RULE-overview requires exactly once
 docs/ar/AR-overview.md:3: error: AR-overview.system-overview cites AR-one-more 0 times; RULE-overview requires exactly once
-docs/fs/FS-demo.md:1: error: FS-demo has 0 security chapters; RULE-security requires exactly one
+docs/fs/FS-demo.md:1: error: FS-demo has 0 security chapters; RULE-security requires exactly one; expected display name "security" (case-insensitive, not section handle); observed direct chapters: "goals: Goals", "requirements: Requirements"
 docs/fs/FS-demo.md:1: error: FS-demo must cite GOAL (citation direction)
 docs/fs/FS-demo.md:6: error: FS-demo.requirements cites REQ 0 times; RULE-requirements-count requires exactly 2
 docs/fs/FS-demo.md:6: error: FS-demo.requirements cites REQ 0 times; RULE-requirements-floor requires at least 2
diff --git a/skills/grund-init/SKILL.md b/skills/grund-init/SKILL.md
index 09990cc73..10d0ab86b 100644
--- a/skills/grund-init/SKILL.md
+++ b/skills/grund-init/SKILL.md
@@ -618,6 +618,8 @@ Subjects select local units only:
 - `The requirements chapter of each FS` selects that named chapter in every FS.
 - `FS-login.requirements` selects one exact named chapter.
 
+Named chapter subjects select handles: `The goal chapter of each FS` reaches `## goal: Goal and hypothesis` by `goal` ([chapter subjects](https://github.com/agent-grounds/grund/blob/main/docs/functional-spec/FS-rules.md#2-subject-selectors)). Presence rules compare direct chapter display names case-insensitively: `Each FS must have exactly one goal chapter.` counts zero for that heading and one for `## goal: Goal` ([presence matching](https://github.com/agent-grounds/grund/blob/main/docs/functional-spec/FS-rules.md#31-chapter-presence)). The finding appends the expected display name and observed pairs such as `"goal: Goal and hypothesis"`, or `none` ([comparison context](https://github.com/agent-grounds/grund/blob/main/docs/functional-spec/FS-rules.md#721-display-name-comparison-context)). Presence `NAME` must be one non-empty token: `Goal and hypothesis` is refused with `NAME forbids whitespace anywhere.` appended to the existing guidance; authored display titles may still contain spaces ([whitespace refusal](https://github.com/agent-grounds/grund/blob/main/docs/functional-spec/FS-rules.md#351-presence-name-whitespace-refusal)).
+
 Named-chapter subjects require `[id] named_sections = true`. Phase 1 has no
 paths, files, folders, wildcards, subject namespaces, numbered-chapter subjects,
 exceptions, definitions, derived terms, settings, or source-code symbols.
@@ -704,7 +706,7 @@ Common refusals are intentional and name the exact accepted rewrite:
 - `Each FS must cite at least 1 GOAL.` → `numeric "at least 1" is not canonical; accepted form: Each FS must cite at least one GOAL.`
 - `Each FS must cite exactly 1 GOAL.` → `numeric "exactly 1" is not canonical; accepted form: Each FS must cite exactly one GOAL.`
 - `Each FS must cite at least one GOAL and must not cite any AR.` → `conjunctions are not accepted; accepted forms: "Each FS must cite at least one GOAL." and "Each FS must not cite any AR."`
-- `Each FS must have exactly one  chapter.` → `chapter name must be a non-empty NAME with no surrounding whitespace; accepted form: Each FS must have exactly one requirements chapter.`
+- `Each FS must have exactly one  chapter.` → `chapter name must be a non-empty NAME with no surrounding whitespace; accepted form: Each FS must have exactly one requirements chapter. NAME forbids whitespace anywhere.`
 - `Each FS must cite at least one GOAL` → `rule must end with "."; accepted form: Each FS must cite at least one GOAL.`
 - `each FS must cite at least one GOAL.` → `fixed word "Each" is case-sensitive; accepted form: Each FS must cite at least one GOAL.`
 - `Each file in vendor/ must cite at least one FS.` → `path subjects are not accepted in phase 1; accepted form: Each FS must cite at least one GOAL.`
diff --git a/tests/e2e/cases/check-chapter-diagnostic-display-name-json/command.args b/tests/e2e/cases/check-chapter-diagnostic-display-name-json/command.args
new file mode 100644
index 000000000..990bd30d8
--- /dev/null
+++ b/tests/e2e/cases/check-chapter-diagnostic-display-name-json/command.args
@@ -0,0 +1 @@
+check {repo} --format json
diff --git a/tests/e2e/cases/check-chapter-diagnostic-display-name-json/expected.exit b/tests/e2e/cases/check-chapter-diagnostic-display-name-json/expected.exit
new file mode 100644
index 000000000..d00491fd7
--- /dev/null
+++ b/tests/e2e/cases/check-chapter-diagnostic-display-name-json/expected.exit
@@ -0,0 +1 @@
+1
diff --git a/tests/e2e/cases/check-chapter-diagnostic-display-name-json/expected.stderr b/tests/e2e/cases/check-chapter-diagnostic-display-name-json/expected.stderr
new file mode 100644
index 000000000..8b1378917
--- /dev/null
+++ b/tests/e2e/cases/check-chapter-diagnostic-display-name-json/expected.stderr
@@ -0,0 +1 @@
+
diff --git a/tests/e2e/cases/check-chapter-diagnostic-display-name-json/expected.stdout b/tests/e2e/cases/check-chapter-diagnostic-display-name-json/expected.stdout
new file mode 100644
index 000000000..694285d19
--- /dev/null
+++ b/tests/e2e/cases/check-chapter-diagnostic-display-name-json/expected.stdout
@@ -0,0 +1 @@
+{"severity":"error","path":"docs/bench/BENCH-001-example-benchmark.md","line":1,"code":"chapter-cardinality","message":"BENCH-001-example-benchmark has 0 goal chapters; RULE-012-bench-goal requires exactly one; expected display name \"goal\" (case-insensitive, not section handle); observed direct chapters: \"goal: Goal and hypothesis\"","sites":null,"authority":["RULE-012-bench-goal"]}
diff --git a/tests/e2e/cases/check-chapter-diagnostic-display-name-json/repo/docs/bench/BENCH-001-example-benchmark.md b/tests/e2e/cases/check-chapter-diagnostic-display-name-json/repo/docs/bench/BENCH-001-example-benchmark.md
new file mode 100644
index 000000000..1e51e50cb
--- /dev/null
+++ b/tests/e2e/cases/check-chapter-diagnostic-display-name-json/repo/docs/bench/BENCH-001-example-benchmark.md
@@ -0,0 +1,5 @@
+# BENCH-001-example-benchmark: Example benchmark
+
+## goal: Goal and hypothesis
+
+This chapter cites §GOAL-001-example-goal.
diff --git a/tests/e2e/cases/check-chapter-diagnostic-display-name-json/repo/docs/goals/GOAL-001-example-goal.md b/tests/e2e/cases/check-chapter-diagnostic-display-name-json/repo/docs/goals/GOAL-001-example-goal.md
new file mode 100644
index 000000000..2bb2dee49
--- /dev/null
+++ b/tests/e2e/cases/check-chapter-diagnostic-display-name-json/repo/docs/goals/GOAL-001-example-goal.md
@@ -0,0 +1,3 @@
+# GOAL-001-example-goal: Example goal
+
+The benchmark explains its goal.
diff --git a/tests/e2e/cases/check-chapter-diagnostic-display-name-json/repo/docs/references.md b/tests/e2e/cases/check-chapter-diagnostic-display-name-json/repo/docs/references.md
new file mode 100644
index 000000000..2e744b6b8
--- /dev/null
+++ b/tests/e2e/cases/check-chapter-diagnostic-display-name-json/repo/docs/references.md
@@ -0,0 +1 @@
+The scenario exercises §BENCH-001-example-benchmark, §RULE-012-bench-goal and §RULE-013-bench-goal-citation.
diff --git a/tests/e2e/cases/check-chapter-diagnostic-display-name-json/repo/docs/rules/RULE-012-bench-goal.md b/tests/e2e/cases/check-chapter-diagnostic-display-name-json/repo/docs/rules/RULE-012-bench-goal.md
new file mode 100644
index 000000000..2a38ed4b8
--- /dev/null
+++ b/tests/e2e/cases/check-chapter-diagnostic-display-name-json/repo/docs/rules/RULE-012-bench-goal.md
@@ -0,0 +1,3 @@
+# RULE-012-bench-goal: Each BENCH must have exactly one goal chapter.
+
+Keep the benchmark grounded in §GOAL-001-example-goal.
diff --git a/tests/e2e/cases/check-chapter-diagnostic-display-name-json/repo/docs/rules/RULE-013-bench-goal-citation.md b/tests/e2e/cases/check-chapter-diagnostic-display-name-json/repo/docs/rules/RULE-013-bench-goal-citation.md
new file mode 100644
index 000000000..4c5780762
--- /dev/null
+++ b/tests/e2e/cases/check-chapter-diagnostic-display-name-json/repo/docs/rules/RULE-013-bench-goal-citation.md
@@ -0,0 +1,3 @@
+# RULE-013-bench-goal-citation: The goal chapter of each BENCH must cite at least one GOAL.
+
+Make the goal explicit with §GOAL-001-example-goal.
diff --git a/tests/e2e/cases/check-chapter-diagnostic-display-name-json/repo/grund.toml b/tests/e2e/cases/check-chapter-diagnostic-display-name-json/repo/grund.toml
new file mode 100644
index 000000000..c06fef45b
--- /dev/null
+++ b/tests/e2e/cases/check-chapter-diagnostic-display-name-json/repo/grund.toml
@@ -0,0 +1,22 @@
+grund_config_version = 1
+project_name = "chapter-diagnostic"
+[reference]
+strict = true
+[id]
+format = "{kind}-{slug}"
+named_sections = true
+[[kinds]]
+kind = "BENCH"
+folder = "docs/bench"
+index = false
+[[kinds]]
+kind = "GOAL"
+folder = "docs/goals"
+index = false
+[[kinds]]
+kind = "RULE"
+folder = "docs/rules"
+index = false
+rules = true
+[scan]
+include = ["docs"]
diff --git a/tests/e2e/cases/check-chapter-diagnostic-display-name-json/spec.refs b/tests/e2e/cases/check-chapter-diagnostic-display-name-json/spec.refs
new file mode 100644
index 000000000..faa6a2b36
--- /dev/null
+++ b/tests/e2e/cases/check-chapter-diagnostic-display-name-json/spec.refs
@@ -0,0 +1,2 @@
+FS-rules.7.2.1
+FS-errors.3
diff --git a/tests/e2e/cases/check-chapter-diagnostic-display-name-text/command.args b/tests/e2e/cases/check-chapter-diagnostic-display-name-text/command.args
new file mode 100644
index 000000000..9c39f98bb
--- /dev/null
+++ b/tests/e2e/cases/check-chapter-diagnostic-display-name-text/command.args
@@ -0,0 +1 @@
+check {repo}
diff --git a/tests/e2e/cases/check-chapter-diagnostic-display-name-text/expected.exit b/tests/e2e/cases/check-chapter-diagnostic-display-name-text/expected.exit
new file mode 100644
index 000000000..d00491fd7
--- /dev/null
+++ b/tests/e2e/cases/check-chapter-diagnostic-display-name-text/expected.exit
@@ -0,0 +1 @@
+1
diff --git a/tests/e2e/cases/check-chapter-diagnostic-display-name-text/expected.stderr b/tests/e2e/cases/check-chapter-diagnostic-display-name-text/expected.stderr
new file mode 100644
index 000000000..8b1378917
--- /dev/null
+++ b/tests/e2e/cases/check-chapter-diagnostic-display-name-text/expected.stderr
@@ -0,0 +1 @@
+
diff --git a/tests/e2e/cases/check-chapter-diagnostic-display-name-text/expected.stdout b/tests/e2e/cases/check-chapter-diagnostic-display-name-text/expected.stdout
new file mode 100644
index 000000000..d12d6b570
--- /dev/null
+++ b/tests/e2e/cases/check-chapter-diagnostic-display-name-text/expected.stdout
@@ -0,0 +1 @@
+docs/bench/BENCH-001-example-benchmark.md:1: error: BENCH-001-example-benchmark has 0 goal chapters; RULE-012-bench-goal requires exactly one; expected display name "goal" (case-insensitive, not section handle); observed direct chapters: "goal: Goal and hypothesis"
diff --git a/tests/e2e/cases/check-chapter-diagnostic-display-name-text/repo/docs/bench/BENCH-001-example-benchmark.md b/tests/e2e/cases/check-chapter-diagnostic-display-name-text/repo/docs/bench/BENCH-001-example-benchmark.md
new file mode 100644
index 000000000..1e51e50cb
--- /dev/null
+++ b/tests/e2e/cases/check-chapter-diagnostic-display-name-text/repo/docs/bench/BENCH-001-example-benchmark.md
@@ -0,0 +1,5 @@
+# BENCH-001-example-benchmark: Example benchmark
+
+## goal: Goal and hypothesis
+
+This chapter cites §GOAL-001-example-goal.
diff --git a/tests/e2e/cases/check-chapter-diagnostic-display-name-text/repo/docs/goals/GOAL-001-example-goal.md b/tests/e2e/cases/check-chapter-diagnostic-display-name-text/repo/docs/goals/GOAL-001-example-goal.md
new file mode 100644
index 000000000..2bb2dee49
--- /dev/null
+++ b/tests/e2e/cases/check-chapter-diagnostic-display-name-text/repo/docs/goals/GOAL-001-example-goal.md
@@ -0,0 +1,3 @@
+# GOAL-001-example-goal: Example goal
+
+The benchmark explains its goal.
diff --git a/tests/e2e/cases/check-chapter-diagnostic-display-name-text/repo/docs/references.md b/tests/e2e/cases/check-chapter-diagnostic-display-name-text/repo/docs/references.md
new file mode 100644
index 000000000..2e744b6b8
--- /dev/null
+++ b/tests/e2e/cases/check-chapter-diagnostic-display-name-text/repo/docs/references.md
@@ -0,0 +1 @@
+The scenario exercises §BENCH-001-example-benchmark, §RULE-012-bench-goal and §RULE-013-bench-goal-citation.
diff --git a/tests/e2e/cases/check-chapter-diagnostic-display-name-text/repo/docs/rules/RULE-012-bench-goal.md b/tests/e2e/cases/check-chapter-diagnostic-display-name-text/repo/docs/rules/RULE-012-bench-goal.md
new file mode 100644
index 000000000..2a38ed4b8
--- /dev/null
+++ b/tests/e2e/cases/check-chapter-diagnostic-display-name-text/repo/docs/rules/RULE-012-bench-goal.md
@@ -0,0 +1,3 @@
+# RULE-012-bench-goal: Each BENCH must have exactly one goal chapter.
+
+Keep the benchmark grounded in §GOAL-001-example-goal.
diff --git a/tests/e2e/cases/check-chapter-diagnostic-display-name-text/repo/docs/rules/RULE-013-bench-goal-citation.md b/tests/e2e/cases/check-chapter-diagnostic-display-name-text/repo/docs/rules/RULE-013-bench-goal-citation.md
new file mode 100644
index 000000000..4c5780762
--- /dev/null
+++ b/tests/e2e/cases/check-chapter-diagnostic-display-name-text/repo/docs/rules/RULE-013-bench-goal-citation.md
@@ -0,0 +1,3 @@
+# RULE-013-bench-goal-citation: The goal chapter of each BENCH must cite at least one GOAL.
+
+Make the goal explicit with §GOAL-001-example-goal.
diff --git a/tests/e2e/cases/check-chapter-diagnostic-display-name-text/repo/grund.toml b/tests/e2e/cases/check-chapter-diagnostic-display-name-text/repo/grund.toml
new file mode 100644
index 000000000..c06fef45b
--- /dev/null
+++ b/tests/e2e/cases/check-chapter-diagnostic-display-name-text/repo/grund.toml
@@ -0,0 +1,22 @@
+grund_config_version = 1
+project_name = "chapter-diagnostic"
+[reference]
+strict = true
+[id]
+format = "{kind}-{slug}"
+named_sections = true
+[[kinds]]
+kind = "BENCH"
+folder = "docs/bench"
+index = false
+[[kinds]]
+kind = "GOAL"
+folder = "docs/goals"
+index = false
+[[kinds]]
+kind = "RULE"
+folder = "docs/rules"
+index = false
+rules = true
+[scan]
+include = ["docs"]
diff --git a/tests/e2e/cases/check-chapter-diagnostic-display-name-text/spec.refs b/tests/e2e/cases/check-chapter-diagnostic-display-name-text/spec.refs
new file mode 100644
index 000000000..faa6a2b36
--- /dev/null
+++ b/tests/e2e/cases/check-chapter-diagnostic-display-name-text/spec.refs
@@ -0,0 +1,2 @@
+FS-rules.7.2.1
+FS-errors.3
diff --git a/tests/e2e/cases/check-chapter-diagnostic-handle-subject-missing-citation/command.args b/tests/e2e/cases/check-chapter-diagnostic-handle-subject-missing-citation/command.args
new file mode 100644
index 000000000..6000aa334
--- /dev/null
+++ b/tests/e2e/cases/check-chapter-diagnostic-handle-subject-missing-citation/command.args
@@ -0,0 +1 @@
+check {repo} --rule "The goal chapter of each BENCH must cite at least one GOAL." --only-rule
diff --git a/tests/e2e/cases/check-chapter-diagnostic-handle-subject-missing-citation/expected.exit b/tests/e2e/cases/check-chapter-diagnostic-handle-subject-missing-citation/expected.exit
new file mode 100644
index 000000000..d00491fd7
--- /dev/null
+++ b/tests/e2e/cases/check-chapter-diagnostic-handle-subject-missing-citation/expected.exit
@@ -0,0 +1 @@
+1
diff --git a/tests/e2e/cases/check-chapter-diagnostic-handle-subject-missing-citation/expected.stderr b/tests/e2e/cases/check-chapter-diagnostic-handle-subject-missing-citation/expected.stderr
new file mode 100644
index 000000000..8b1378917
--- /dev/null
+++ b/tests/e2e/cases/check-chapter-diagnostic-handle-subject-missing-citation/expected.stderr
@@ -0,0 +1 @@
+
diff --git a/tests/e2e/cases/check-chapter-diagnostic-handle-subject-missing-citation/expected.stdout b/tests/e2e/cases/check-chapter-diagnostic-handle-subject-missing-citation/expected.stdout
new file mode 100644
index 000000000..9d30210b7
--- /dev/null
+++ b/tests/e2e/cases/check-chapter-diagnostic-handle-subject-missing-citation/expected.stdout
@@ -0,0 +1 @@
+docs/bench/BENCH-001-example-benchmark.md:3: error: BENCH-001-example-benchmark.goal must cite GOAL (--rule, RULE-013-bench-goal-citation)
diff --git a/tests/e2e/cases/check-chapter-diagnostic-handle-subject-missing-citation/repo/docs/bench/BENCH-001-example-benchmark.md b/tests/e2e/cases/check-chapter-diagnostic-handle-subject-missing-citation/repo/docs/bench/BENCH-001-example-benchmark.md
new file mode 100644
index 000000000..41cb867bf
--- /dev/null
+++ b/tests/e2e/cases/check-chapter-diagnostic-handle-subject-missing-citation/repo/docs/bench/BENCH-001-example-benchmark.md
@@ -0,0 +1,5 @@
+# BENCH-001-example-benchmark: Example benchmark
+
+## goal: Goal and hypothesis
+
+This chapter has no citation.
diff --git a/tests/e2e/cases/check-chapter-diagnostic-handle-subject-missing-citation/repo/docs/goals/GOAL-001-example-goal.md b/tests/e2e/cases/check-chapter-diagnostic-handle-subject-missing-citation/repo/docs/goals/GOAL-001-example-goal.md
new file mode 100644
index 000000000..2bb2dee49
--- /dev/null
+++ b/tests/e2e/cases/check-chapter-diagnostic-handle-subject-missing-citation/repo/docs/goals/GOAL-001-example-goal.md
@@ -0,0 +1,3 @@
+# GOAL-001-example-goal: Example goal
+
+The benchmark explains its goal.
diff --git a/tests/e2e/cases/check-chapter-diagnostic-handle-subject-missing-citation/repo/docs/references.md b/tests/e2e/cases/check-chapter-diagnostic-handle-subject-missing-citation/repo/docs/references.md
new file mode 100644
index 000000000..2e744b6b8
--- /dev/null
+++ b/tests/e2e/cases/check-chapter-diagnostic-handle-subject-missing-citation/repo/docs/references.md
@@ -0,0 +1 @@
+The scenario exercises §BENCH-001-example-benchmark, §RULE-012-bench-goal and §RULE-013-bench-goal-citation.
diff --git a/tests/e2e/cases/check-chapter-diagnostic-handle-subject-missing-citation/repo/docs/rules/RULE-012-bench-goal.md b/tests/e2e/cases/check-chapter-diagnostic-handle-subject-missing-citation/repo/docs/rules/RULE-012-bench-goal.md
new file mode 100644
index 000000000..2a38ed4b8
--- /dev/null
+++ b/tests/e2e/cases/check-chapter-diagnostic-handle-subject-missing-citation/repo/docs/rules/RULE-012-bench-goal.md
@@ -0,0 +1,3 @@
+# RULE-012-bench-goal: Each BENCH must have exactly one goal chapter.
+
+Keep the benchmark grounded in §GOAL-001-example-goal.
diff --git a/tests/e2e/cases/check-chapter-diagnostic-handle-subject-missing-citation/repo/docs/rules/RULE-013-bench-goal-citation.md b/tests/e2e/cases/check-chapter-diagnostic-handle-subject-missing-citation/repo/docs/rules/RULE-013-bench-goal-citation.md
new file mode 100644
index 000000000..4c5780762
--- /dev/null
+++ b/tests/e2e/cases/check-chapter-diagnostic-handle-subject-missing-citation/repo/docs/rules/RULE-013-bench-goal-citation.md
@@ -0,0 +1,3 @@
+# RULE-013-bench-goal-citation: The goal chapter of each BENCH must cite at least one GOAL.
+
+Make the goal explicit with §GOAL-001-example-goal.
diff --git a/tests/e2e/cases/check-chapter-diagnostic-handle-subject-missing-citation/repo/grund.toml b/tests/e2e/cases/check-chapter-diagnostic-handle-subject-missing-citation/repo/grund.toml
new file mode 100644
index 000000000..c06fef45b
--- /dev/null
+++ b/tests/e2e/cases/check-chapter-diagnostic-handle-subject-missing-citation/repo/grund.toml
@@ -0,0 +1,22 @@
+grund_config_version = 1
+project_name = "chapter-diagnostic"
+[reference]
+strict = true
+[id]
+format = "{kind}-{slug}"
+named_sections = true
+[[kinds]]
+kind = "BENCH"
+folder = "docs/bench"
+index = false
+[[kinds]]
+kind = "GOAL"
+folder = "docs/goals"
+index = false
+[[kinds]]
+kind = "RULE"
+folder = "docs/rules"
+index = false
+rules = true
+[scan]
+include = ["docs"]
diff --git a/tests/e2e/cases/check-chapter-diagnostic-handle-subject-missing-citation/spec.refs b/tests/e2e/cases/check-chapter-diagnostic-handle-subject-missing-citation/spec.refs
new file mode 100644
index 000000000..4f45549b5
--- /dev/null
+++ b/tests/e2e/cases/check-chapter-diagnostic-handle-subject-missing-citation/spec.refs
@@ -0,0 +1,2 @@
+FS-rules.2
+FS-rules.7.3
diff --git a/tests/e2e/cases/check-chapter-diagnostic-handle-subject/command.args b/tests/e2e/cases/check-chapter-diagnostic-handle-subject/command.args
new file mode 100644
index 000000000..6000aa334
--- /dev/null
+++ b/tests/e2e/cases/check-chapter-diagnostic-handle-subject/command.args
@@ -0,0 +1 @@
+check {repo} --rule "The goal chapter of each BENCH must cite at least one GOAL." --only-rule
diff --git a/tests/e2e/cases/check-chapter-diagnostic-handle-subject/expected.exit b/tests/e2e/cases/check-chapter-diagnostic-handle-subject/expected.exit
new file mode 100644
index 000000000..573541ac9
--- /dev/null
+++ b/tests/e2e/cases/check-chapter-diagnostic-handle-subject/expected.exit
@@ -0,0 +1 @@
+0
diff --git a/tests/e2e/cases/check-chapter-diagnostic-handle-subject/expected.stderr b/tests/e2e/cases/check-chapter-diagnostic-handle-subject/expected.stderr
new file mode 100644
index 000000000..8b1378917
--- /dev/null
+++ b/tests/e2e/cases/check-chapter-diagnostic-handle-subject/expected.stderr
@@ -0,0 +1 @@
+
diff --git a/tests/e2e/cases/check-chapter-diagnostic-handle-subject/expected.stdout b/tests/e2e/cases/check-chapter-diagnostic-handle-subject/expected.stdout
new file mode 100644
index 000000000..2e9ba477f
--- /dev/null
+++ b/tests/e2e/cases/check-chapter-diagnostic-handle-subject/expected.stdout
@@ -0,0 +1 @@
+success
diff --git a/tests/e2e/cases/check-chapter-diagnostic-handle-subject/repo/docs/bench/BENCH-001-example-benchmark.md b/tests/e2e/cases/check-chapter-diagnostic-handle-subject/repo/docs/bench/BENCH-001-example-benchmark.md
new file mode 100644
index 000000000..1e51e50cb
--- /dev/null
+++ b/tests/e2e/cases/check-chapter-diagnostic-handle-subject/repo/docs/bench/BENCH-001-example-benchmark.md
@@ -0,0 +1,5 @@
+# BENCH-001-example-benchmark: Example benchmark
+
+## goal: Goal and hypothesis
+
+This chapter cites §GOAL-001-example-goal.
diff --git a/tests/e2e/cases/check-chapter-diagnostic-handle-subject/repo/docs/goals/GOAL-001-example-goal.md b/tests/e2e/cases/check-chapter-diagnostic-handle-subject/repo/docs/goals/GOAL-001-example-goal.md
new file mode 100644
index 000000000..2bb2dee49
--- /dev/null
+++ b/tests/e2e/cases/check-chapter-diagnostic-handle-subject/repo/docs/goals/GOAL-001-example-goal.md
@@ -0,0 +1,3 @@
+# GOAL-001-example-goal: Example goal
+
+The benchmark explains its goal.
diff --git a/tests/e2e/cases/check-chapter-diagnostic-handle-subject/repo/docs/references.md b/tests/e2e/cases/check-chapter-diagnostic-handle-subject/repo/docs/references.md
new file mode 100644
index 000000000..2e744b6b8
--- /dev/null
+++ b/tests/e2e/cases/check-chapter-diagnostic-handle-subject/repo/docs/references.md
@@ -0,0 +1 @@
+The scenario exercises §BENCH-001-example-benchmark, §RULE-012-bench-goal and §RULE-013-bench-goal-citation.
diff --git a/tests/e2e/cases/check-chapter-diagnostic-handle-subject/repo/docs/rules/RULE-012-bench-goal.md b/tests/e2e/cases/check-chapter-diagnostic-handle-subject/repo/docs/rules/RULE-012-bench-goal.md
new file mode 100644
index 000000000..2a38ed4b8
--- /dev/null
+++ b/tests/e2e/cases/check-chapter-diagnostic-handle-subject/repo/docs/rules/RULE-012-bench-goal.md
@@ -0,0 +1,3 @@
+# RULE-012-bench-goal: Each BENCH must have exactly one goal chapter.
+
+Keep the benchmark grounded in §GOAL-001-example-goal.
diff --git a/tests/e2e/cases/check-chapter-diagnostic-handle-subject/repo/docs/rules/RULE-013-bench-goal-citation.md b/tests/e2e/cases/check-chapter-diagnostic-handle-subject/repo/docs/rules/RULE-013-bench-goal-citation.md
new file mode 100644
index 000000000..4c5780762
--- /dev/null
+++ b/tests/e2e/cases/check-chapter-diagnostic-handle-subject/repo/docs/rules/RULE-013-bench-goal-citation.md
@@ -0,0 +1,3 @@
+# RULE-013-bench-goal-citation: The goal chapter of each BENCH must cite at least one GOAL.
+
+Make the goal explicit with §GOAL-001-example-goal.
diff --git a/tests/e2e/cases/check-chapter-diagnostic-handle-subject/repo/grund.toml b/tests/e2e/cases/check-chapter-diagnostic-handle-subject/repo/grund.toml
new file mode 100644
index 000000000..c06fef45b
--- /dev/null
+++ b/tests/e2e/cases/check-chapter-diagnostic-handle-subject/repo/grund.toml
@@ -0,0 +1,22 @@
+grund_config_version = 1
+project_name = "chapter-diagnostic"
+[reference]
+strict = true
+[id]
+format = "{kind}-{slug}"
+named_sections = true
+[[kinds]]
+kind = "BENCH"
+folder = "docs/bench"
+index = false
+[[kinds]]
+kind = "GOAL"
+folder = "docs/goals"
+index = false
+[[kinds]]
+kind = "RULE"
+folder = "docs/rules"
+index = false
+rules = true
+[scan]
+include = ["docs"]
diff --git a/tests/e2e/cases/check-chapter-diagnostic-handle-subject/spec.refs b/tests/e2e/cases/check-chapter-diagnostic-handle-subject/spec.refs
new file mode 100644
index 000000000..dafd77de9
--- /dev/null
+++ b/tests/e2e/cases/check-chapter-diagnostic-handle-subject/spec.refs
@@ -0,0 +1,2 @@
+FS-rules.2
+FS-rules.3.1
diff --git a/tests/e2e/cases/check-chapter-diagnostic-whitespace-refusal/command.args b/tests/e2e/cases/check-chapter-diagnostic-whitespace-refusal/command.args
new file mode 100644
index 000000000..9c5b5857c
--- /dev/null
+++ b/tests/e2e/cases/check-chapter-diagnostic-whitespace-refusal/command.args
@@ -0,0 +1 @@
+check {repo} --rule "Each BENCH must have exactly one Goal and hypothesis chapter." --only-rule
diff --git a/tests/e2e/cases/check-chapter-diagnostic-whitespace-refusal/expected.exit b/tests/e2e/cases/check-chapter-diagnostic-whitespace-refusal/expected.exit
new file mode 100644
index 000000000..0cfbf0888
--- /dev/null
+++ b/tests/e2e/cases/check-chapter-diagnostic-whitespace-refusal/expected.exit
@@ -0,0 +1 @@
+2
diff --git a/tests/e2e/cases/check-chapter-diagnostic-whitespace-refusal/expected.stderr b/tests/e2e/cases/check-chapter-diagnostic-whitespace-refusal/expected.stderr
new file mode 100644
index 000000000..776524909
--- /dev/null
+++ b/tests/e2e/cases/check-chapter-diagnostic-whitespace-refusal/expected.stderr
@@ -0,0 +1 @@
+error: chapter name must be a non-empty NAME with no surrounding whitespace; accepted form: Each FS must have exactly one requirements chapter. NAME forbids whitespace anywhere.
diff --git a/tests/e2e/cases/check-chapter-diagnostic-whitespace-refusal/expected.stdout b/tests/e2e/cases/check-chapter-diagnostic-whitespace-refusal/expected.stdout
new file mode 100644
index 000000000..8b1378917
--- /dev/null
+++ b/tests/e2e/cases/check-chapter-diagnostic-whitespace-refusal/expected.stdout
@@ -0,0 +1 @@
+
diff --git a/tests/e2e/cases/check-chapter-diagnostic-whitespace-refusal/repo/docs/bench/BENCH-001-example-benchmark.md b/tests/e2e/cases/check-chapter-diagnostic-whitespace-refusal/repo/docs/bench/BENCH-001-example-benchmark.md
new file mode 100644
index 000000000..1e51e50cb
--- /dev/null
+++ b/tests/e2e/cases/check-chapter-diagnostic-whitespace-refusal/repo/docs/bench/BENCH-001-example-benchmark.md
@@ -0,0 +1,5 @@
+# BENCH-001-example-benchmark: Example benchmark
+
+## goal: Goal and hypothesis
+
+This chapter cites §GOAL-001-example-goal.
diff --git a/tests/e2e/cases/check-chapter-diagnostic-whitespace-refusal/repo/docs/goals/GOAL-001-example-goal.md b/tests/e2e/cases/check-chapter-diagnostic-whitespace-refusal/repo/docs/goals/GOAL-001-example-goal.md
new file mode 100644
index 000000000..2bb2dee49
--- /dev/null
+++ b/tests/e2e/cases/check-chapter-diagnostic-whitespace-refusal/repo/docs/goals/GOAL-001-example-goal.md
@@ -0,0 +1,3 @@
+# GOAL-001-example-goal: Example goal
+
+The benchmark explains its goal.
diff --git a/tests/e2e/cases/check-chapter-diagnostic-whitespace-refusal/repo/docs/references.md b/tests/e2e/cases/check-chapter-diagnostic-whitespace-refusal/repo/docs/references.md
new file mode 100644
index 000000000..2e744b6b8
--- /dev/null
+++ b/tests/e2e/cases/check-chapter-diagnostic-whitespace-refusal/repo/docs/references.md
@@ -0,0 +1 @@
+The scenario exercises §BENCH-001-example-benchmark, §RULE-012-bench-goal and §RULE-013-bench-goal-citation.
diff --git a/tests/e2e/cases/check-chapter-diagnostic-whitespace-refusal/repo/docs/rules/RULE-012-bench-goal.md b/tests/e2e/cases/check-chapter-diagnostic-whitespace-refusal/repo/docs/rules/RULE-012-bench-goal.md
new file mode 100644
index 000000000..2a38ed4b8
--- /dev/null
+++ b/tests/e2e/cases/check-chapter-diagnostic-whitespace-refusal/repo/docs/rules/RULE-012-bench-goal.md
@@ -0,0 +1,3 @@
+# RULE-012-bench-goal: Each BENCH must have exactly one goal chapter.
+
+Keep the benchmark grounded in §GOAL-001-example-goal.
diff --git a/tests/e2e/cases/check-chapter-diagnostic-whitespace-refusal/repo/docs/rules/RULE-013-bench-goal-citation.md b/tests/e2e/cases/check-chapter-diagnostic-whitespace-refusal/repo/docs/rules/RULE-013-bench-goal-citation.md
new file mode 100644
index 000000000..4c5780762
--- /dev/null
+++ b/tests/e2e/cases/check-chapter-diagnostic-whitespace-refusal/repo/docs/rules/RULE-013-bench-goal-citation.md
@@ -0,0 +1,3 @@
+# RULE-013-bench-goal-citation: The goal chapter of each BENCH must cite at least one GOAL.
+
+Make the goal explicit with §GOAL-001-example-goal.
diff --git a/tests/e2e/cases/check-chapter-diagnostic-whitespace-refusal/repo/grund.toml b/tests/e2e/cases/check-chapter-diagnostic-whitespace-refusal/repo/grund.toml
new file mode 100644
index 000000000..c06fef45b
--- /dev/null
+++ b/tests/e2e/cases/check-chapter-diagnostic-whitespace-refusal/repo/grund.toml
@@ -0,0 +1,22 @@
+grund_config_version = 1
+project_name = "chapter-diagnostic"
+[reference]
+strict = true
+[id]
+format = "{kind}-{slug}"
+named_sections = true
+[[kinds]]
+kind = "BENCH"
+folder = "docs/bench"
+index = false
+[[kinds]]
+kind = "GOAL"
+folder = "docs/goals"
+index = false
+[[kinds]]
+kind = "RULE"
+folder = "docs/rules"
+index = false
+rules = true
+[scan]
+include = ["docs"]
diff --git a/tests/e2e/cases/check-chapter-diagnostic-whitespace-refusal/spec.refs b/tests/e2e/cases/check-chapter-diagnostic-whitespace-refusal/spec.refs
new file mode 100644
index 000000000..dd25eedbd
--- /dev/null
+++ b/tests/e2e/cases/check-chapter-diagnostic-whitespace-refusal/spec.refs
@@ -0,0 +1,3 @@
+FS-rules.3.5.1
+FS-rules.4
+FS-errors.3
diff --git a/tests/e2e/cases/check-rules-chapter-absent-paired/expected.stdout b/tests/e2e/cases/check-rules-chapter-absent-paired/expected.stdout
index dcf9fad37..7090ff6c6 100644
--- a/tests/e2e/cases/check-rules-chapter-absent-paired/expected.stdout
+++ b/tests/e2e/cases/check-rules-chapter-absent-paired/expected.stdout
@@ -1,2 +1,2 @@
-docs/fs/FS-silent.md:1: error: FS-silent has 0 requirements chapters; RULE-presence requires at least one
+docs/fs/FS-silent.md:1: error: FS-silent has 0 requirements chapters; RULE-presence requires at least one; expected display name "requirements" (case-insensitive, not section handle); observed direct chapters: none
 docs/fs/FS-silent.md:1: error: FS-silent has no requirements chapter, so RULE-requirements cannot reach it; add the chapter, or narrow the rule to the declarations that have one; this became an error in grund 0.16.0
diff --git a/tests/e2e/cases/check-rules-chapter-block-closer-live/expected.stdout b/tests/e2e/cases/check-rules-chapter-block-closer-live/expected.stdout
index 55cd60159..45f69b63c 100644
--- a/tests/e2e/cases/check-rules-chapter-block-closer-live/expected.stdout
+++ b/tests/e2e/cases/check-rules-chapter-block-closer-live/expected.stdout
@@ -1 +1 @@
-docs/ar/AR-none.md:1: error: AR-none has 0 Terms chapters; RULE-ar-terms requires exactly one
+docs/ar/AR-none.md:1: error: AR-none has 0 Terms chapters; RULE-ar-terms requires exactly one; expected display name "Terms" (case-insensitive, not section handle); observed direct chapters: none
diff --git a/tests/e2e/cases/check-rules-chapter-source-declaration-reached/expected.stdout b/tests/e2e/cases/check-rules-chapter-source-declaration-reached/expected.stdout
index 00600aaf8..4f70d1b7f 100644
--- a/tests/e2e/cases/check-rules-chapter-source-declaration-reached/expected.stdout
+++ b/tests/e2e/cases/check-rules-chapter-source-declaration-reached/expected.stdout
@@ -1,2 +1,2 @@
-docs/ar/AR-markdown.md:1: error: AR-markdown has 0 Nonexistent chapters; RULE-nonexistent requires exactly one
-src/inline.rs:1: error: AR-inline has 0 Nonexistent chapters; RULE-nonexistent requires exactly one
+docs/ar/AR-markdown.md:1: error: AR-markdown has 0 Nonexistent chapters; RULE-nonexistent requires exactly one; expected display name "Nonexistent" (case-insensitive, not section handle); observed direct chapters: "terms: Terms"
+src/inline.rs:1: error: AR-inline has 0 Nonexistent chapters; RULE-nonexistent requires exactly one; expected display name "Nonexistent" (case-insensitive, not section handle); observed direct chapters: "terms: Terms"