diff --git a/.trinity/seals/src_port::trios::crates::trios_chat::rings::CR_CHAT_01::src::identity_key_usage_count_guard.json b/.trinity/seals/src_port::trios::crates::trios_chat::rings::CR_CHAT_01::src::identity_key_usage_count_guard.json
new file mode 100644
index 0000000000..4635db2601
--- /dev/null
+++ b/.trinity/seals/src_port::trios::crates::trios_chat::rings::CR_CHAT_01::src::identity_key_usage_count_guard.json
@@ -0,0 +1,28 @@
+{
+  "built_by": "t27c-bootstrap@0.5.2+82de5086e",
+  "closure": [],
+  "config": "gen=c,rust,verilog,zig;tests=zig",
+  "gen_hash_c": "sha256:b9b86d1f9e32e855d5bbbf5fca81628179ef08784f85265eef3ba734c7264daf",
+  "gen_hash_rust": "sha256:8ddc835042c8843a304a23eb50ae4bd35d99ee6ff5af903ab38fb095588da1ce",
+  "gen_hash_verilog": "sha256:26f87391c7247b606d68126d94310a335bc71a7785651aa33f05b5c394a6539b",
+  "gen_hash_zig": "sha256:503d01702e1f7491d34e824db50bf5f51a60cdc043751664819ed1e1cf906893",
+  "module": "port::trios::crates::trios_chat::rings::CR_CHAT_01::src::identity_key_usage_count_guard",
+  "ring": 12,
+  "seal_schema": 2,
+  "sealed_at": "2026-10-30T19:37:50Z",
+  "sealed_by": "t27c-bootstrap@0.5.2",
+  "spec_hash": "sha256:984e6a910b01246515a548dab1f3c0cd38701dafb84398f60c9feb8b57d189b6",
+  "spec_path": "specs/port/trios/crates/trios-chat/rings/CR-CHAT-01/src/identity_key_usage_count_guard.t27",
+  "tests": {
+    "failed": 0,
+    "failing": [],
+    "forced": false,
+    "passed": 10,
+    "total": 10,
+    "vacuous": 0
+  },
+  "toolchain": {
+    "test_runner": "sha256:1a50286d6170ef41c779d26385a1be59823925d7131497c93d84194144ba93b3",
+    "zig": "0.16.0"
+  }
+}
\ No newline at end of file
diff --git a/specs/port/trios/crates/trios-chat/rings/CR-CHAT-01/src/identity_key_usage_count_guard.t27 b/specs/port/trios/crates/trios-chat/rings/CR-CHAT-01/src/identity_key_usage_count_guard.t27
new file mode 100644
index 0000000000..851b365792
--- /dev/null
+++ b/specs/port/trios/crates/trios-chat/rings/CR-CHAT-01/src/identity_key_usage_count_guard.t27
@@ -0,0 +1,91 @@
+module port::trios::crates::trios_chat::rings::CR_CHAT_01::src::identity_key_usage_count_guard;
+
+// Port of gHashTag/trios
+// crates/trios-chat/rings/CR-CHAT-01/src/identity_key_usage_count_guard.rs (138 lines).
+//
+// The Rust original returns Result<(), KeyUsageError>. The .t27 language has no
+// Result/Option, so the same decision is carried by a closed enum with one honest
+// "accepted" variant. `NegativeCount` and `MustRotate` are declared in Rust
+// (lines 40-47) but `validate_key_usage` never constructs them: u64 cannot be
+// negative, and rotation is reported by `key_needs_rotation` instead. They are
+// therefore documented here rather than invented as reachable outcomes.
+
+// Lines 31 and 34: the two pre-registered thresholds.
+const IKUC_MAX_SIGNATURES: u64 = 100_000;
+const IKUC_WARN_SIGNATURES: u64 = 80_000;
+
+// Lines 39-48: `Result<(), KeyUsageError>` collapsed to a single code.
+enum KeyUsageError {
+    Accepted,
+    SignatureCountExceeded,
+    ZeroKeyId,
+}
+
+// Lines 51-62: zero key id is checked first, so a zero key with an over-limit
+// count reports ZeroKeyId, not SignatureCountExceeded. The count bound is
+// inclusive: exactly IKUC_MAX_SIGNATURES is still accepted.
+pub fn validate_key_usage(key_id: u64, signature_count: u64) -> KeyUsageError {
+    if (key_id == 0) {
+        return .ZeroKeyId;
+    }
+    if (signature_count > IKUC_MAX_SIGNATURES) {
+        return .SignatureCountExceeded;
+    }
+    return .Accepted;
+}
+
+// Lines 65-67: the warning threshold is inclusive (>=), and it is independent of
+// the hard maximum: 80_000 already asks for rotation, 99_999 does not exceed max.
+pub fn key_needs_rotation(signature_count: u64) -> bool {
+    return signature_count >= IKUC_WARN_SIGNATURES;
+}
+
+// IKUC-01 (lines 74-80): one past the max is rejected.
+test ikuc_01_exceeded_rejected {
+    assert(validate_key_usage(1, IKUC_MAX_SIGNATURES + 1) == .SignatureCountExceeded);
+}
+
+// IKUC-02 (lines 83-88): zero key id is rejected.
+test ikuc_02_zero_key_rejected {
+    assert(validate_key_usage(0, 10) == .ZeroKeyId);
+}
+
+// IKUC-03 (lines 91-95): the maximum itself is accepted.
+test ikuc_03_at_max_accepted {
+    assert(validate_key_usage(1, IKUC_MAX_SIGNATURES) == .Accepted);
+}
+
+// IKUC-04 (lines 98-101): a fresh key with no signatures is accepted.
+test ikuc_04_zero_sigs_accepted {
+    assert(validate_key_usage(1, 0) == .Accepted);
+}
+
+// IKUC-05 (lines 104-107): the warning threshold triggers rotation.
+test ikuc_05_warning_triggers {
+    assert(key_needs_rotation(IKUC_WARN_SIGNATURES));
+}
+
+// IKUC-06 (lines 110-113): one below the warning threshold does not.
+test ikuc_06_below_warning {
+    assert(!key_needs_rotation(IKUC_WARN_SIGNATURES - 1));
+}
+
+// IKUC-07 (lines 116-119): a valid mid-range count is accepted.
+test ikuc_07_mid_range_accepted {
+    assert(validate_key_usage(42, 50_000) == .Accepted);
+}
+
+// IKUC-08 (lines 122-125): a single signature is accepted.
+test ikuc_08_single_accepted {
+    assert(validate_key_usage(1, 1) == .Accepted);
+}
+
+// IKUC-09 (lines 128-131): the hard maximum also needs rotation.
+test ikuc_09_max_needs_rotation {
+    assert(key_needs_rotation(IKUC_MAX_SIGNATURES));
+}
+
+// IKUC-10 (lines 134-137): a huge key id is still a valid key id.
+test ikuc_10_large_key_accepted {
+    assert(validate_key_usage(18_446_744_073_709_551_615, 1000) == .Accepted);
+}