diff --git a/.jp/config.toml b/.jp/config.toml
index c4b572d33..5f10ad450 100644
--- a/.jp/config.toml
+++ b/.jp/config.toml
@@ -34,7 +34,7 @@ anthropic = "anthropic/claude-sonnet-5"
 claude = "anthropic/claude-sonnet-5"
 sonnet = "anthropic/claude-sonnet-5"
 opus = "anthropic/claude-opus-5"
-fable = "anthropic/claude-fable-5"
+fable = "anthropic/claude-fable-5-1"
 haiku = "anthropic/claude-haiku-4-5"
 zai = "cerebras/zai-glm-4.7"
 # OpenAI aliases
diff --git a/crates/jp_llm/src/provider/anthropic.rs b/crates/jp_llm/src/provider/anthropic.rs
index c55abbe5d..33d8e76fd 100644
--- a/crates/jp_llm/src/provider/anthropic.rs
+++ b/crates/jp_llm/src/provider/anthropic.rs
@@ -1811,6 +1811,11 @@ fn model_overrides(id: &str) -> Option<ModelOverrides> {
     let cutoff = |year, month| NaiveDate::from_ymd_opt(year, month, 1);
 
     Some(match id {
+        "claude-fable-5-1" => ModelOverrides {
+            knowledge_cutoff: cutoff(2026, 6),
+            always_on: true,
+            ..Default::default()
+        },
         "claude-fable-5" => ModelOverrides {
             knowledge_cutoff: cutoff(2026, 1),
             always_on: true,
diff --git a/crates/jp_llm/src/provider/anthropic_tests.rs b/crates/jp_llm/src/provider/anthropic_tests.rs
index a89f705f6..a044907c9 100644
--- a/crates/jp_llm/src/provider/anthropic_tests.rs
+++ b/crates/jp_llm/src/provider/anthropic_tests.rs
@@ -530,6 +530,40 @@ fn test_map_model_opus_5() {
     assert!(!details.supports_prefill());
 }
 
+/// Verify the `map_model` arm for Claude Fable 5.1 produces the expected
+/// `ModelDetails`, including the `thinking-always-on` capability that stops JP
+/// from sending `thinking: disabled` and from hard-forcing a `tool_choice`,
+/// both of which Fable 5.1 rejects with a 400.
+#[test]
+fn test_map_model_fable_5_1() {
+    let model = adaptive_api_model("claude-fable-5-1", "Claude Fable 5.1", true, true);
+
+    let details = map_model(model).unwrap();
+
+    assert_eq!(
+        details.id,
+        (PROVIDER, "claude-fable-5-1").try_into().unwrap()
+    );
+    assert_eq!(details.display_name.as_deref(), Some("Claude Fable 5.1"));
+    assert_eq!(details.context_window, Some(1_000_000));
+    assert_eq!(details.max_output_tokens, Some(128_000));
+    assert_eq!(
+        details.knowledge_cutoff,
+        NaiveDate::from_ymd_opt(2026, 6, 1)
+    );
+    assert_eq!(
+        details.reasoning,
+        Some(ReasoningDetails::adaptive(true, true).always_on())
+    );
+    assert_eq!(details.structured_output, Some(true));
+    assert_eq!(details.deprecated, Some(ModelDeprecation::Active));
+    assert!(details.features.contains(&"adaptive-thinking"));
+    assert!(details.features.contains(&"interleaved-thinking"));
+    assert!(details.features.contains(&"context-editing"));
+    assert!(!details.supports_disabling_thinking());
+    assert!(!details.supports_prefill());
+}
+
 /// Verify the `map_model` arm for Claude Fable 5 produces the expected
 /// `ModelDetails`, including the `thinking-always-on` capability that stops JP
 /// from sending `thinking: disabled` (which Fable rejects).