diff --git a/cmd/creator-web/responsive_test.go b/cmd/creator-web/responsive_test.go
index 12248ee..49ff43a 100644
--- a/cmd/creator-web/responsive_test.go
+++ b/cmd/creator-web/responsive_test.go
@@ -43,6 +43,8 @@ func TestChatResponsiveGuardrailsConstrainMobileGridItem(t *testing.T) {
 		".chat-view { width: 100%; min-width: 0;",
 		"@media (max-width: 640px)",
 		".chat-layout { height: auto; display: block; }",
+		".chat-header > .operator-link, .build-meta { display: none; }",
+		".chat-header .cognitive-console-link { flex: 0 1 110px;",
 	} {
 		if !strings.Contains(stylesheet, guard) {
 			t.Fatalf("chat responsive guardrail missing: %s", guard)
diff --git a/cmd/creator-web/static/assets/chat.css b/cmd/creator-web/static/assets/chat.css
index b6fe4e4..525649d 100644
--- a/cmd/creator-web/static/assets/chat.css
+++ b/cmd/creator-web/static/assets/chat.css
@@ -107,9 +107,10 @@ textarea { resize: vertical; min-height: 84px; max-height: 240px; padding: 14px;
   .conversation-starters { align-items: stretch; }
   .conversation-starters span { width: 100%; }
   .chat-header { gap: 10px; padding: 0 12px; }
-  .chat-header .cognitive-status { display: inline-flex; max-width: 150px; overflow: hidden; text-overflow: ellipsis; }
-  .build-meta { font-size: 8px; letter-spacing: .04em; }
-  .build-meta time { font-size: 7px; }
+  .chat-header .cognitive-status { display: inline-flex; flex: 1 1 110px; min-width: 0; max-width: 110px; overflow: hidden; text-overflow: ellipsis; }
+  .chat-header .cognitive-console-link { flex: 0 1 110px; min-width: 0; overflow: hidden; text-overflow: ellipsis; }
+  .chat-header > .operator-link, .build-meta { display: none; }
+  .chat-header > #logout { flex: 0 0 38px; }
   .chat-layout { height: auto; display: block; }
   .chat-side, .chat-main { min-height: auto; max-height: none; overflow: visible; }
   .chat-left, .chat-right { border: 0; border-bottom: 1px solid var(--line); }
diff --git a/dev/ACTIVE_TASK.json b/dev/ACTIVE_TASK.json
index c842cd2..925a019 100644
--- a/dev/ACTIVE_TASK.json
+++ b/dev/ACTIVE_TASK.json
@@ -1,5 +1,5 @@
 {
-  "task_file": "dev/tasks/DEV-000289-chat-mobile-overflow-fix.json",
-  "task_id": "DEV-000289",
+  "task_file": "dev/tasks/DEV-000290-chat-mobile-header-overflow.json",
+  "task_id": "DEV-000290",
   "task_revision": 1
 }
diff --git a/dev/tasks/DEV-000290-chat-mobile-header-overflow.json b/dev/tasks/DEV-000290-chat-mobile-header-overflow.json
new file mode 100644
index 0000000..5f1ebd4
--- /dev/null
+++ b/dev/tasks/DEV-000290-chat-mobile-header-overflow.json
@@ -0,0 +1,23 @@
+{
+  "task_id": "DEV-000290",
+  "task_revision": 1,
+  "architecture_revision": "ADR-0018",
+  "base_repo_revision": "e9d5b1ca8a2aa14fb11241c2766e79547a469078",
+  "risk_tier": "E",
+  "intent": "Constrain authenticated chat header controls at mobile viewport widths after live acceptance found a second horizontal overflow source.",
+  "requirement_ids": ["authenticated mobile UI acceptance", "no horizontal overflow at 390px"],
+  "allowed_change_scope": {"modules": ["creator-web"], "paths": ["dev/ACTIVE_TASK.json", "dev/tasks/DEV-000290-chat-mobile-header-overflow.json", "cmd/creator-web/static/assets/chat.css", "cmd/creator-web/responsive_test.go"]},
+  "forbidden_change_scope": {"paths": ["architecture/**", "security/**", "database/**", "LLM-local/**", "modules/**", "adapters/**"]},
+  "allowed_architecture_delta": {"new_cross_module_dependencies": 0, "new_canonical_owners": 0, "new_privileges": 0, "new_third_party_dependencies": 0, "new_database_owner_roles": 0},
+  "contracts": {"consume": ["existing creator-web header controls"], "may_change": []},
+  "semantic_owner": "creator-web presentation",
+  "canonical_state": ["none"],
+  "state_transitions": ["header intrinsic controls -> bounded mobile controls"],
+  "side_effects_and_privileges": ["none"],
+  "persistence_and_migrations": ["none"],
+  "failure_retry_restart": ["CSS-only; no runtime state or recovery semantics changed"],
+  "assumptions": ["desktop header remains unchanged", "the settings link remains available through the cognitive console link"],
+  "acceptance_scenarios": ["authenticated chat has no horizontal overflow at 390px", "settings navigation remains available", "logout remains visible", "desktop static layout remains unchanged"],
+  "required_tests": ["go test ./cmd/creator-web", "go vet ./cmd/creator-web", "preflight", "check-diff", "check-architecture", "independent", "git diff --check", "CI", "production health smoke", "one authenticated mobile smoke"],
+  "terminal_gap_states": ["BLOCKED_BY_SPEC_GAP", "BLOCKED_BY_ARCHITECTURE_GAP", "BLOCKED_BY_MISSING_CAPABILITY"]
+}