diff --git a/.abcd/development/brief/04-surfaces/02-disembark.md b/.abcd/development/brief/04-surfaces/02-disembark.md
index ebc48a2ad..77d337e50 100644
--- a/.abcd/development/brief/04-surfaces/02-disembark.md
+++ b/.abcd/development/brief/04-surfaces/02-disembark.md
@@ -137,7 +137,7 @@ a section of its own.
 ├── _provenance.json                    # the lifeboat marker and re-pack gate key, written last
 ├── coverage.json                       # per-section status (grounded|partial|blank), evidence, what was searched
 ├── coverage.md                         # rendered
-├── brief/                              # the brief, section by section, grounded from the source
+├── brief/                              # the brief, section by section, grounded from the source; a partial one says why
 │   ├── 01-product/ … 06-delivery/
 │   └── glossary/
 ├── graveyard/                          # what the project tried and abandoned
diff --git a/.abcd/work/issues/open/iss-2610072347247487-the-disembark-probe-s-invariants-naming.md b/.abcd/work/issues/open/iss-2610072347247487-the-disembark-probe-s-invariants-naming.md
deleted file mode 100644
index c4a9127a3..000000000
--- a/.abcd/work/issues/open/iss-2610072347247487-the-disembark-probe-s-invariants-naming.md
+++ /dev/null
@@ -1,15 +0,0 @@
----
-schema_version: 1
-id: "iss-2610072347247487"
-slug: "the-disembark-probe-s-invariants-naming"
-severity: "minor"
-category: "drift"
-source: "agent-finding"
-found_during: "the disembark probe lane (run-2610072231362768), 2026-10-07"
-origin: researcher-authored
-production_mode: hand-written
-found_at: "internal/core/lifeboat"
-remedy: "Have the invariants, naming and personas sources read their own brief file as the open-questions and tradeoffs sources now do (an authored file grounds the section, a stub makes it partial), and print each partial section's reason in the pack's per-section file as the coverage report does."
----
-
-The disembark probe's invariants, naming and personas sources ignore their own brief files, unlike open-questions and tradeoffs since the probe lane, and the pack's per-section file does not print a partial section's reason, which coverage.json and the text render now carry.
diff --git a/.abcd/work/issues/resolved/iss-2610072347247487-the-disembark-probe-s-invariants-naming.md b/.abcd/work/issues/resolved/iss-2610072347247487-the-disembark-probe-s-invariants-naming.md
new file mode 100644
index 000000000..b3492ef97
--- /dev/null
+++ b/.abcd/work/issues/resolved/iss-2610072347247487-the-disembark-probe-s-invariants-naming.md
@@ -0,0 +1,23 @@
+---
+schema_version: 1
+id: "iss-2610072347247487"
+slug: "the-disembark-probe-s-invariants-naming"
+severity: "minor"
+category: "drift"
+source: "agent-finding"
+found_during: "the disembark probe lane (run-2610072231362768), 2026-10-07"
+origin: researcher-authored
+production_mode: hand-written
+found_at: "internal/core/lifeboat"
+remedy: "Have the invariants, naming and personas sources read their own brief file as the open-questions and tradeoffs sources now do (an authored file grounds the section, a stub makes it partial), and print each partial section's reason in the pack's per-section file as the coverage report does."
+resolution: "The invariants, naming and personas native adapters now read the section's own brief file through nativeWithBriefFile, as open-questions and tradeoffs do: an authored file grounds the section, a stub is cited and lifts a blank to partial with a reason. The pack's per-section brief file prints a partial section's reason as 'Why partial:', cleaned like every other untrusted field."
+impact: fix
+resolved_by:
+  commit: "aa51824ccdcbc36b188ae2e7f4dc27c5b8af7109"
+---
+
+The disembark probe's invariants, naming and personas sources ignore their own brief files, unlike open-questions and tradeoffs since the probe lane, and the pack's per-section file does not print a partial section's reason, which coverage.json and the text render now carry.
+
+## Grounds
+
+- pursued: a repository whose only signal for invariants, naming or personas is an authored brief file probes grounded for that section (a stub probes partial with a reason), and every partial section's packed brief file states its reason; TestNativeConstraintAndPersonaSectionsGroundFromTheirBriefFiles, TestPackSectionFileStatesWhyPartial and TestBriefSectionDocCleansItsPartialReason would fail if an adapter ignored its brief file or a packed partial omitted its reason
diff --git a/internal/core/lifeboat/mdrender_test.go b/internal/core/lifeboat/mdrender_test.go
index 2861f2b41..54a3c7b9e 100644
--- a/internal/core/lifeboat/mdrender_test.go
+++ b/internal/core/lifeboat/mdrender_test.go
@@ -195,3 +195,14 @@ func TestBlockValueKeepsATripleBacktickSpanAProseLine(t *testing.T) {
 		}
 	}
 }
+
+func TestBriefSectionDocCleansItsPartialReason(t *testing.T) {
+	md := string(briefSectionDoc(SectionCoverage{
+		Name: "product/context", Status: StatusPartial,
+		Reason: "Found docs/<script>x.md and [a](http://example.com) <!--c",
+	}))
+	assertNoLiveHazard(t, "brief section doc reason", md)
+	if !strings.Contains(md, "Why partial: ") {
+		t.Errorf("partial brief section doc states no reason:\n%s", md)
+	}
+}
diff --git a/internal/core/lifeboat/partial_reason_test.go b/internal/core/lifeboat/partial_reason_test.go
index 3bc99187d..a9ed3229c 100644
--- a/internal/core/lifeboat/partial_reason_test.go
+++ b/internal/core/lifeboat/partial_reason_test.go
@@ -108,3 +108,41 @@ func TestPartialIsBuiltOnlyThroughTheConstructor(t *testing.T) {
 		}
 	}
 }
+
+// TestPackSectionFileStatesWhyPartial carries the reason contract into the
+// pack: each partial section's brief file in the lifeboat says why it is
+// partial, as coverage.json and the rendered report do, and a grounded one
+// says nothing of the kind (iss-2610072347247487).
+func TestPackSectionFileStatesWhyPartial(t *testing.T) {
+	sawPartial := false
+	for name, dir := range partialReasonFixtures(t) {
+		cov, err := Probe(dir)
+		if err != nil {
+			t.Fatalf("%s: %v", name, err)
+		}
+		lb, err := Plan(dir)
+		if err != nil {
+			t.Fatalf("%s: plan: %v", name, err)
+		}
+		for _, s := range cov.Sections {
+			leaf, ok := briefLeaf(s.Name)
+			if !ok || s.Status == StatusBlank {
+				continue
+			}
+			md := string(planFile(t, lb, "brief/"+leaf).Content)
+			if s.Status != StatusPartial {
+				if strings.Contains(md, "Why partial:") {
+					t.Errorf("%s: grounded %s's brief file states a partial reason:\n%s", name, s.Name, md)
+				}
+				continue
+			}
+			sawPartial = true
+			if want := "Why partial: " + mdInline(s.Reason); !strings.Contains(md, want) {
+				t.Errorf("%s: partial %s's brief file does not state its reason %q:\n%s", name, s.Name, s.Reason, md)
+			}
+		}
+	}
+	if !sawPartial {
+		t.Fatal("no fixture packed a partial section; the contract was not exercised")
+	}
+}
diff --git a/internal/core/lifeboat/plan.go b/internal/core/lifeboat/plan.go
index b2c092ec7..e326fed92 100644
--- a/internal/core/lifeboat/plan.go
+++ b/internal/core/lifeboat/plan.go
@@ -478,8 +478,9 @@ func lifeboatPathFor(section Section) string {
 }
 
 // briefSectionDoc renders one grounded/partial brief section as a citation map:
-// its status, the tier and confidence, and the evidence it was grounded from.
-// It is deterministic and cites every source — never synthesised prose.
+// its status, the tier and confidence, why a partial is partial (the reason the
+// coverage report carries), and the evidence it was grounded from. It is
+// deterministic and cites every source — never synthesised prose.
 func briefSectionDoc(s SectionCoverage) []byte {
 	var b strings.Builder
 	fmt.Fprintf(&b, "# %s\n\n", s.Name)
@@ -488,6 +489,13 @@ func briefSectionDoc(s SectionCoverage) []byte {
 		fmt.Fprintf(&b, " (%s, %s confidence)", s.Tier, s.Confidence)
 	}
 	b.WriteString("\n\n")
+	// The reason names repository paths, which a hostile repository controls, so
+	// it is cleaned like every other untrusted field the lifeboat writes.
+	if s.Status == StatusPartial {
+		if r := mdInline(s.Reason); r != "" {
+			fmt.Fprintf(&b, "Why partial: %s\n\n", r)
+		}
+	}
 	if len(s.Evidence) > 0 {
 		b.WriteString("Grounded from:\n\n")
 		ev := append([]string(nil), s.Evidence...)
diff --git a/internal/core/lifeboat/sources_native.go b/internal/core/lifeboat/sources_native.go
index 679e99f2b..d282bbc72 100644
--- a/internal/core/lifeboat/sources_native.go
+++ b/internal/core/lifeboat/sources_native.go
@@ -186,7 +186,6 @@ const (
 	nativeIntentsDir  = ".abcd/development/intents"
 	nativeGlossaryDir = ".abcd/development/brief/glossary"
 	nativeDecisions   = ".abcd/work/DECISIONS.md"
-	nativePersonas    = ".abcd/development/brief/01-product/05-personas.md"
 )
 
 // nativeIssueStates are the capture-ledger subdirectories, in a fixed order so
@@ -424,15 +423,23 @@ func (nativeSpineSource) Probe(ctx *SourceContext) Evidence {
 	}
 }
 
-// nativeInvariantsSource grounds "constraints/invariants" from the conventions
-// router (AGENTS.md / CLAUDE.md) and any lint configuration under .abcd/. The
-// router grounds it; lint config alone is partial. Blank when neither exists.
+// nativeInvariantsSource grounds "constraints/invariants" from the section's own
+// brief file, the conventions router (AGENTS.md / CLAUDE.md) and any lint
+// configuration under .abcd/. An authored brief file or the router grounds it;
+// lint config alone, or a stub brief file, is partial. Blank when the record has
+// none of them.
 type nativeInvariantsSource struct{}
 
 func (nativeInvariantsSource) Section() Section { return "constraints/invariants" }
 func (nativeInvariantsSource) Tier() Tier       { return TierNative }
 
-func (nativeInvariantsSource) Probe(ctx *SourceContext) Evidence {
+func (s nativeInvariantsSource) Probe(ctx *SourceContext) Evidence {
+	return nativeWithBriefFile(ctx, s.Section(), s.probeRecord(ctx))
+}
+
+// probeRecord is the invariants reading from the conventions router and lint
+// configuration alone, before the brief file is consulted.
+func (nativeInvariantsSource) probeRecord(ctx *SourceContext) Evidence {
 	var sources []string
 	hasRouter := false
 	for _, f := range []string{"AGENTS.md", "CLAUDE.md"} {
@@ -455,20 +462,27 @@ func (nativeInvariantsSource) Probe(ctx *SourceContext) Evidence {
 	sort.Strings(sources)
 	if !hasRouter {
 		return partial(ConfidenceMedium, sources,
-			"Found lint configuration under .abcd/ but no conventions router, so some rules are enforced but none is stated; an AGENTS.md or CLAUDE.md stating the invariants would ground it.")
+			"Found lint configuration under .abcd/ but no conventions router, so some rules are enforced but none is stated; an AGENTS.md or CLAUDE.md stating the invariants, or an authored "+nativeSectionBriefFile("constraints/invariants")+", would ground it.")
 	}
 	return Evidence{Status: StatusGrounded, Confidence: ConfidenceHigh, Sources: sources}
 }
 
-// nativeNamingSource grounds "constraints/naming" from the brief glossary. A
-// glossary carrying real prose grounds it; an empty or stub glossary is partial;
-// no glossary directory is a blank.
+// nativeNamingSource grounds "constraints/naming" from the section's own brief
+// file and the brief glossary. An authored brief file or a glossary carrying
+// real prose grounds it; a stub glossary or a stub brief file is partial. Blank
+// when the record has neither.
 type nativeNamingSource struct{}
 
 func (nativeNamingSource) Section() Section { return "constraints/naming" }
 func (nativeNamingSource) Tier() Tier       { return TierNative }
 
-func (nativeNamingSource) Probe(ctx *SourceContext) Evidence {
+func (s nativeNamingSource) Probe(ctx *SourceContext) Evidence {
+	return nativeWithBriefFile(ctx, s.Section(), s.probeRecord(ctx))
+}
+
+// probeRecord is the naming reading from the brief glossary alone, before the
+// section's brief file is consulted.
+func (nativeNamingSource) probeRecord(ctx *SourceContext) Evidence {
 	if !ctx.IsDir(nativeGlossaryDir) {
 		return blank(
 			[]string{nativeGlossaryDir},
@@ -495,29 +509,27 @@ func (nativeNamingSource) Probe(ctx *SourceContext) Evidence {
 	}
 	if body < nativeGroundedBodyBytes {
 		return partial(ConfidenceMedium, dedupeSorted(files),
-			fmt.Sprintf("Found %d glossary file(s) under %s carrying %d characters of body prose, under the %d an authored glossary carries; defining the project's terms there in prose would ground it.",
-				len(files), nativeGlossaryDir, body, nativeGroundedBodyBytes))
+			fmt.Sprintf("Found %d glossary file(s) under %s carrying %d characters of body prose, under the %d an authored glossary carries; defining the project's terms there in prose, or an authored %s, would ground it.",
+				len(files), nativeGlossaryDir, body, nativeGroundedBodyBytes, nativeSectionBriefFile("constraints/naming")))
 	}
 	return Evidence{Status: StatusGrounded, Confidence: ConfidenceHigh, Sources: dedupeSorted(files)}
 }
 
-// nativePersonasSource is the deliberately hard case: "product/personas" is a
-// human question rarely written down anywhere. It reaches at most PARTIAL, and
-// only when an authored personas file exists; otherwise it returns a blank —
-// the expected, correct result for a section a repository cannot supply.
+// nativePersonasSource grounds "product/personas" from the section's own brief
+// file, as every other brief section is grounded: an authored file grounds it, a
+// stub one is partial, and a missing one is a blank. The section is human-owned
+// (adr-36) — who a product serves is not derivable from a repository — so the
+// record holds no other signal for it, and the blank, the expected result where
+// no one has written the personas down, carries the question only a person can
+// answer.
 type nativePersonasSource struct{}
 
 func (nativePersonasSource) Section() Section { return "product/personas" }
 func (nativePersonasSource) Tier() Tier       { return TierNative }
 
-func (nativePersonasSource) Probe(ctx *SourceContext) Evidence {
-	data, ok := ctx.ReadFile(nativePersonas)
-	if !ok || nativeBodyBytes(data) < nativeGroundedBodyBytes {
-		return blank(
-			[]string{nativePersonas},
-			"Who are the personas this product serves? Personas are a human question, rarely derivable from a repository.",
-		)
-	}
-	return partial(ConfidenceLow, []string{nativePersonas},
-		"Found an authored "+nativePersonas+"; personas stay partial by design, because who a product serves is confirmed by a person, not derived from a repository — a person's confirmation would ground it.")
+func (s nativePersonasSource) Probe(ctx *SourceContext) Evidence {
+	return nativeWithBriefFile(ctx, s.Section(), blank(
+		nil,
+		"Who are the personas this product serves? Personas are a human question, rarely derivable from a repository.",
+	))
 }
diff --git a/internal/core/lifeboat/sources_native_test.go b/internal/core/lifeboat/sources_native_test.go
index 848192f1c..4260188d3 100644
--- a/internal/core/lifeboat/sources_native_test.go
+++ b/internal/core/lifeboat/sources_native_test.go
@@ -207,9 +207,9 @@ func TestNativeInvariantsGround(t *testing.T) {
 	}
 }
 
-// TestNativePersonasBlank holds the deliberately-hard case: with no personas file
-// in the fixture, "product/personas" returns a blank naming what it searched and
-// the question a human must answer — never grounded.
+// TestNativePersonasBlank holds the human-owned case: with no personas file in
+// the fixture, "product/personas" returns a blank naming what it searched and the
+// question a human must answer.
 func TestNativePersonasBlank(t *testing.T) {
 	ctx, err := newSourceContext(nativeTierFixture(t))
 	if err != nil {
@@ -316,3 +316,59 @@ func TestNativeEvidenceSectionsGroundFromTheirBriefFiles(t *testing.T) {
 		t.Errorf("stub open-questions = %s (reason %q), want partial with a reason", ev.Status, ev.Reason)
 	}
 }
+
+// TestNativeConstraintAndPersonaSectionsGroundFromTheirBriefFiles: the
+// invariants, naming and personas adapters read the section's own brief file,
+// as the evidence adapters do — an authored file grounds the section even when
+// the record holds no conventions router, glossary or other signal, and a stub
+// one alone is partial and says why (iss-2610072347247487).
+func TestNativeConstraintAndPersonaSectionsGroundFromTheirBriefFiles(t *testing.T) {
+	prose := "This section is authored by the project, not scaffolded. It states what " +
+		"the team holds fixed and who the work is for, each with the reason it was " +
+		"settled that way, so a reader can pick the work up without reconstructing " +
+		"it from history or asking the people who wrote it.\n"
+	files := map[Section]string{
+		"constraints/invariants": ".abcd/development/brief/02-constraints/03-invariants.md",
+		"constraints/naming":     ".abcd/development/brief/02-constraints/04-naming.md",
+		"product/personas":       ".abcd/development/brief/01-product/05-personas.md",
+	}
+
+	authored := map[string]string{}
+	stubbed := map[string]string{}
+	for _, file := range files {
+		authored[file] = "# Section\n\n" + prose
+		stubbed[file] = "# Section\n\nTODO.\n"
+	}
+	dir := t.TempDir()
+	writeTree(t, dir, authored)
+	ctx, err := newSourceContext(dir)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer ctx.Close()
+	stub := t.TempDir()
+	writeTree(t, stub, stubbed)
+	sctx, err := newSourceContext(stub)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer sctx.Close()
+
+	for section, file := range files {
+		ev := nativeSourceForSection(t, section).Probe(ctx)
+		if ev.Status != StatusGrounded {
+			t.Errorf("%s = %s with an authored %s, want grounded", section, ev.Status, file)
+		}
+		if !containsSource(ev.Sources, file) {
+			t.Errorf("%s evidence = %v, want %s cited", section, ev.Sources, file)
+		}
+
+		ev = nativeSourceForSection(t, section).Probe(sctx)
+		if ev.Status != StatusPartial || ev.Reason == "" {
+			t.Errorf("stub %s = %s (reason %q), want partial with a reason", section, ev.Status, ev.Reason)
+		}
+		if !containsSource(ev.Sources, file+" (stub)") {
+			t.Errorf("stub %s evidence = %v, want %s cited as a stub", section, ev.Sources, file)
+		}
+	}
+}