diff --git a/src/usage/openai_helpers.rs b/src/usage/openai_helpers.rs
index 448c6ca1f4..9b33b7bd2a 100644
--- a/src/usage/openai_helpers.rs
+++ b/src/usage/openai_helpers.rs
@@ -8,15 +8,18 @@ pub(super) struct ParsedOpenAIUsageReport {
     pub(super) hard_limit_reached: bool,
 }
 
-fn normalize_ratio_value(raw: f32) -> f32 {
+pub(super) fn normalize_ratio_value(raw: f32) -> f32 {
     if !raw.is_finite() {
         return 0.0;
     }
-    if raw > 1.0 {
-        (raw / 100.0).clamp(0.0, 1.0)
-    } else {
-        raw.clamp(0.0, 1.0)
-    }
+    // The ChatGPT `wham/usage` endpoint (and equivalent OpenAI account usage
+    // endpoints) always report `used_percent` as a value in `[0, 100]`. The
+    // previous implementation tried to auto-detect ratio-vs-percent based on
+    // `raw > 1.0`, which incorrectly mapped the legitimate response
+    // `used_percent: 1` (1% used) to a ratio of `1.0` (100% used). Treating
+    // the value as a percent unconditionally avoids that misclassification
+    // and matches the documented API contract.
+    (raw / 100.0).clamp(0.0, 1.0)
 }
 
 fn normalize_percent(raw: f32) -> f32 {
diff --git a/src/usage/tests.rs b/src/usage/tests.rs
index ea246bdbfa..ca8ebd9c18 100644
--- a/src/usage/tests.rs
+++ b/src/usage/tests.rs
@@ -641,3 +641,66 @@ fn test_account_usage_probe_detects_all_accounts_exhausted() {
     assert!(probe.best_available_alternative().is_none());
     assert!(probe.switch_guidance().is_none());
 }
+
+#[test]
+fn test_normalize_ratio_value_treats_low_integer_values_as_percent() {
+    // Direct unit test for the normalization helper to lock in the contract:
+    // `wham/usage` and OpenAI account-usage endpoints report `used_percent`
+    // in `[0, 100]`. Inputs must always be divided by 100, never treated as
+    // an already-normalized ratio.
+    assert!((openai_helpers::normalize_ratio_value(0.0) - 0.0).abs() < 1e-6);
+    assert!((openai_helpers::normalize_ratio_value(1.0) - 0.01).abs() < 1e-6);
+    assert!((openai_helpers::normalize_ratio_value(5.0) - 0.05).abs() < 1e-6);
+    assert!((openai_helpers::normalize_ratio_value(50.0) - 0.5).abs() < 1e-6);
+    assert!((openai_helpers::normalize_ratio_value(100.0) - 1.0).abs() < 1e-6);
+    // Out of range / weird inputs are clamped, not exploded.
+    assert!((openai_helpers::normalize_ratio_value(150.0) - 1.0).abs() < 1e-6);
+    assert!((openai_helpers::normalize_ratio_value(-5.0) - 0.0).abs() < 1e-6);
+    assert!((openai_helpers::normalize_ratio_value(f32::NAN) - 0.0).abs() < 1e-6);
+}
+
+#[test]
+fn test_parse_openai_usage_payload_reports_low_percentages_correctly() {
+    // Regression for upstream PR #178 / issue #137.
+    // The live `wham/usage` payload returns `used_percent` values in
+    // `[0, 100]`. A weekly bucket reporting `1` (1% used) must not be
+    // misclassified as a fully exhausted ratio of `1.0` (100% used). This
+    // mirrors the shape of a real production response from
+    // `https://chatgpt.com/backend-api/wham/usage`.
+    let json = serde_json::json!({
+        "plan_type": "prolite",
+        "rate_limit": {
+            "allowed": true,
+            "limit_reached": false,
+            "primary_window": {
+                "used_percent": 5,
+                "reset_at": 1_778_283_299_i64
+            },
+            "secondary_window": {
+                "used_percent": 1,
+                "reset_at": 1_778_870_099_i64
+            }
+        },
+        "additional_rate_limits": [{
+            "limit_name": "GPT-5.3-Codex-Spark",
+            "rate_limit": {
+                "allowed": true,
+                "primary_window": { "used_percent": 5, "reset_at": 1_778_283_310_i64 },
+                "secondary_window": { "used_percent": 1, "reset_at": 1_778_870_110_i64 }
+            }
+        }]
+    });
+
+    let parsed = openai_helpers::parse_openai_usage_payload(&json);
+
+    assert!(!parsed.hard_limit_reached);
+    let by_name: std::collections::HashMap<_, _> = parsed
+        .limits
+        .iter()
+        .map(|l| (l.name.as_str(), l.usage_percent))
+        .collect();
+    assert_eq!(by_name.get("5-hour window"), Some(&5.0));
+    assert_eq!(by_name.get("7-day window"), Some(&1.0));
+    assert_eq!(by_name.get("GPT-5.3-Codex-Spark (5h)"), Some(&5.0));
+    assert_eq!(by_name.get("GPT-5.3-Codex-Spark (7d)"), Some(&1.0));
+}
diff --git a/src/usage_openai.rs b/src/usage_openai.rs
index 448c6ca1f4..b1e794991e 100644
--- a/src/usage_openai.rs
+++ b/src/usage_openai.rs
@@ -12,11 +12,14 @@ fn normalize_ratio_value(raw: f32) -> f32 {
     if !raw.is_finite() {
         return 0.0;
     }
-    if raw > 1.0 {
-        (raw / 100.0).clamp(0.0, 1.0)
-    } else {
-        raw.clamp(0.0, 1.0)
-    }
+    // The ChatGPT `wham/usage` endpoint (and equivalent OpenAI account usage
+    // endpoints) always report `used_percent` as a value in `[0, 100]`. The
+    // previous implementation tried to auto-detect ratio-vs-percent based on
+    // `raw > 1.0`, which incorrectly mapped the legitimate response
+    // `used_percent: 1` (1% used) to a ratio of `1.0` (100% used). Treating
+    // the value as a percent unconditionally avoids that misclassification
+    // and matches the documented API contract.
+    (raw / 100.0).clamp(0.0, 1.0)
 }
 
 fn normalize_percent(raw: f32) -> f32 {