diff --git a/docs/development/testing-and-quality.md b/docs/development/testing-and-quality.md
index 4f2fa4be39..8ce3645802 100644
--- a/docs/development/testing-and-quality.md
+++ b/docs/development/testing-and-quality.md
@@ -1313,6 +1313,25 @@ fields; this does not introduce a new telemetry system or receipt gate.
 
 ### Budget Failure Decisions
 
+The thin heartbeat's 4,500-character presentation allowance did not cover the
+complete combination of a 320-character scope, all five runtime capability
+flags, Codex App transport and an explicit CLI route. The existing public CLI
+fixture with `/opt/loopx/qualified-tools/bin/loopx` emits 4,851 normalized body
+characters at `a36e01c32`; its instructions and command arguments are complete.
+Calibrate only this presentation allowance to 4,900, leaving 49 characters above
+that input. Retain the original over-budget observation and add the complete
+CLI combination plus an oversized-route negative case. Prompt text, capability
+flags, the visible Goal's 4,000-character host limit, existing JSON/body fixture
+ceilings, execution authority and frozen qualification results remain unchanged.
+This corrects diagnostic coverage; it is not an output reduction or a claim of
+model compliance, runtime recovery or lower cost.
+
+薄提示原 4,500 字符展示预算未覆盖完整能力与显式 CLI 路由的组合；同一公开夹具
+保留 320 字符 scope、五项能力和完整指令时为 4,851。仅将该展示预算校准为
+4,900，保留原超限记录，并加入完整组合及更长路由仍超限的反例。正文、参数、
+4,000 字符宿主硬边界、既有 JSON/正文夹具上限及执行权限不变；不据此声称节省
+输出、恢复运行或改善模型行为。
+
 The fixed visible-Goal host fixture's 3,200-character regression guard predates
 `1d5d2d0f6`, which adds the known Todo choice to the first current guard. On the
 same four host inputs at `b201da8ba`, substituting only the pre-change dispatch
diff --git a/loopx/control_plane/heartbeat/budget.py b/loopx/control_plane/heartbeat/budget.py
index 77ad3c5ab7..fc261fd7d2 100644
--- a/loopx/control_plane/heartbeat/budget.py
+++ b/loopx/control_plane/heartbeat/budget.py
@@ -23,7 +23,10 @@
     # The same generic CLI + 320-char scope with explicit runtime also needs
     # 5,715 chars; retain those routes instead of shortening the instructions.
     "brief": 5_800,
-    "thin": 4_500,
+    # Full runtime capability flags plus an explicit CLI route and 320-char
+    # scope emit 4,851 normalized chars with unchanged guidance. Keep that
+    # supported combination; this is not a transport or execution limit.
+    "thin": 4_900,
     "visible_goal": 4_000,
 }
 NATIVE_GOAL_HOST_MAX_CHARS = INTERFACE_BUDGET_CHARS["visible_goal"]
diff --git a/tests/control_plane/test_cli_output_budget.py b/tests/control_plane/test_cli_output_budget.py
index 497d7018b8..dccc946edf 100644
--- a/tests/control_plane/test_cli_output_budget.py
+++ b/tests/control_plane/test_cli_output_budget.py
@@ -1712,12 +1712,50 @@ def test_thin_json_budget_retains_full_supported_scope(tmp_path: Path) -> None:
         )
         payload = measurement["payload"]
         assert scope in payload["task_body"]
-        assert payload["interface_budget"]["max_chars"] == 4500
+        assert payload["interface_budget"]["max_chars"] == 4900
         assert payload["interface_budget"]["within_budget"] is True
         assert "refresh-state --goal-outcome-update-json" in payload["task_body"]
         assert "Local outcomes never replace root continuation, budget or stop criteria." in payload["task_body"]
 
 
+@pytest.mark.parametrize("route_padding, within_budget", [("", True), ("x" * 48, False)])
+def test_thin_budget_covers_complete_capability_and_cli_routes(
+    tmp_path: Path, route_padding: str, within_budget: bool,
+) -> None:
+    # Exercise the actual CLI composition, not a shortened instruction or an
+    # estimated sum. An oversized route must still report a budget failure.
+    with _stable_budget_fixture_root(tmp_path) as root:
+        project, runtime, registry_path, state_file = _write_fixture(root, SCENARIOS[0])
+        import_fixture_authority(registry_path, GOAL_ID)
+        command = _surface_commands(
+            project=project, runtime=runtime, registry_path=registry_path,
+            state_file=state_file, output_format="json",
+        )["heartbeat_prompt_thin"]
+        scope = "x" * 320
+        command[command.index("--agent-scope") + 1] = scope
+        cli_route = f"/opt/loopx/{route_padding}qualified-tools/bin/loopx"
+        command.extend(["--codex-app", "--cli-bin", cli_route])
+        capabilities = ("shell", "filesystem", "network", "external_evidence_poll", "browser")
+        for capability in capabilities:
+            command.extend(["--available-capability", capability])
+        exit_code, text = _invoke_cli(command)
+        assert exit_code == 0, text
+        payload = json.loads(text)
+        body, budget = payload["task_body"], payload["interface_budget"]
+        assert scope in body and body.count(cli_route) >= 2
+        assert all(f"--available-capability {capability}" in body for capability in capabilities)
+        assert "--codex-app" in body and "--runtime-root" in body and "--registry" in body
+        assert "--todo-id <id>" in body and "settlement_plan.ordered_steps" in body
+        assert "ambiguous effects need readback/recovery, not blind retry" in body
+        assert "refresh-state --goal-outcome-update-json" in body
+        assert "Local outcomes never replace root continuation, budget or stop criteria." in body
+        # Preserve the historical 4,500-character failure as a characterized
+        # input; the allowance changes, not the complete emitted instructions.
+        assert budget["budget_char_count"] > 4500
+        assert budget["max_chars"] == 4900
+        assert budget["within_budget"] is within_budget
+
+
 def test_brief_budget_retains_full_commands_on_real_long_paths() -> None:
     # A reproducible 128-character absolute root; directory depth can still
     # change JSON escaping cost. Keep full routes and this workload;
diff --git a/tests/control_plane/test_heartbeat_prompt_support.py b/tests/control_plane/test_heartbeat_prompt_support.py
index 857e126191..a31d282301 100644
--- a/tests/control_plane/test_heartbeat_prompt_support.py
+++ b/tests/control_plane/test_heartbeat_prompt_support.py
@@ -98,7 +98,7 @@ def test_native_profile_long_routes_retain_one_complete_settlement_contract() ->
 
 @pytest.mark.parametrize("mode,limit", [
     ("full", 13100), ("compact", 8000), ("brief", 5800),
-    ("thin", 4500), ("visible_goal", 4000),
+    ("thin", 4900), ("visible_goal", 4000),
 ])
 def test_prompt_body_limit_remains_independent_of_json_envelope(mode: str, limit: int) -> None:
     for size in (limit, limit + 1):
@@ -356,7 +356,7 @@ def test_brief_diagnostics_keep_only_the_selected_prompt_command() -> None:
 
 @pytest.mark.parametrize(
     ("mode", "base_budget"),
-    [("full", 13100), ("compact", 8000), ("brief", 5800), ("thin", 4500)],
+    [("full", 13100), ("compact", 8000), ("brief", 5800), ("thin", 4900)],
 )
 @pytest.mark.parametrize("scope_chars", [0, 320])
 @pytest.mark.parametrize("runtime_profile", ["codex_app_heartbeat", "generic_cli"])