diff --git a/agent/bedrock_adapter.py b/agent/bedrock_adapter.py
index d3e6dfcd101e..50f05e3aa29f 100644
--- a/agent/bedrock_adapter.py
+++ b/agent/bedrock_adapter.py
@@ -1352,12 +1352,16 @@ BEDROCK_CONTEXT_LENGTHS: Dict[str, int] = {
     # Anthropic Claude models on Bedrock.
     # Context windows per Anthropic's official models comparison
     # (https://platform.claude.com/docs/en/about-claude/models/overview).
-    # Sonnet 5 / Opus 4.8 / 4.7 / 4.6 / Sonnet 4.6 have 1M generally
+    # Fable / Sonnet 5 / Opus 4.8 / 4.7 / 4.6 / Sonnet 4.6 have 1M generally
     # available (no beta header required as of April 2026). Sonnet 4.5 and
     # Sonnet 4 had their `context-1m-2025-08-07` beta retired on
     # April 30, 2026, so they are standard 200K; Haiku 4.5 is 200K.
+    # These 1M entries must match agent/model_metadata.py
+    # DEFAULT_CONTEXT_LENGTHS or the agent compresses context prematurely.
     # Keys are matched by longest-substring, so the versioned 4-6/4-7/4-8
     # entries win over the generic "anthropic.claude-opus-4" fallback.
+    "anthropic.claude-fable-5":      1_000_000,
+    "anthropic.claude-fable":        1_000_000,
     "anthropic.claude-sonnet-5":     1_000_000,
     "anthropic.claude-opus-4-8":     1_000_000,
     "anthropic.claude-opus-4-7":     1_000_000,
diff --git a/agent/model_metadata.py b/agent/model_metadata.py
index 19e58e3d738f..7e193aab09a6 100644
--- a/agent/model_metadata.py
+++ b/agent/model_metadata.py
@@ -2175,6 +2175,12 @@ def get_model_context_length(
     if endpoint_context is not None:
         return endpoint_context
 
+    is_bedrock_context = provider == "bedrock" or (
+        base_url
+        and base_url_hostname(base_url).startswith("bedrock-runtime.")
+        and base_url_host_matches(base_url, "amazonaws.com")
+    )
+
     # 1. Check persistent cache (model+provider)
     # LM Studio is excluded — its loaded context length is transient (the
     # user can reload the model with a different context_length at any time
@@ -2243,6 +2249,26 @@ def get_model_context_length(
                     model, base_url,
                 )
                 # Fall through; step 5b reconciles and overwrites if portal responds.
+            # Invalidate stale Bedrock entries seeded before the Claude 4.6+
+            # long-context table was corrected to 1M.
+            elif is_bedrock_context:
+                try:
+                    from agent.bedrock_adapter import get_bedrock_context_length
+                    bedrock_ctx = get_bedrock_context_length(model)
+                    if cached != bedrock_ctx:
+                        logger.info(
+                            "Dropping stale Bedrock cache entry %s@%s -> %s; "
+                            "using static Bedrock table value %s",
+                            model,
+                            base_url,
+                            f"{cached:,}",
+                            f"{bedrock_ctx:,}",
+                        )
+                        _invalidate_cached_context_length(model, base_url)
+                        return bedrock_ctx
+                except ImportError:
+                    pass
+                return cached
             else:
                 if is_local_endpoint(base_url):
                     return _reconcile_local_cached_context_length(
@@ -2253,17 +2279,13 @@ def get_model_context_length(
     # 1b. AWS Bedrock — use static context length table.
     # Bedrock's ListFoundationModels API doesn't expose context window sizes,
     # so we maintain a curated table in bedrock_adapter.py that reflects
-    # AWS-imposed limits (e.g. 200K for Claude models vs 1M on the native
-    # Anthropic API).  This must run BEFORE the custom-endpoint probe at
+    # Bedrock-hosted model limits (e.g. older Claude 4 at 200K; Claude
+    # Opus/Sonnet 4.6+ at 1M).  This must run BEFORE the custom-endpoint probe at
     # step 2 — bedrock-runtime.<region>.amazonaws.com is not in
     # _URL_TO_PROVIDER, so it would otherwise be treated as a custom endpoint,
     # fail the /models probe (Bedrock doesn't expose that shape), and fall
     # back to the 128K default before reaching the original step 4b branch.
-    if provider == "bedrock" or (
-        base_url
-        and base_url_hostname(base_url).startswith("bedrock-runtime.")
-        and base_url_host_matches(base_url, "amazonaws.com")
-    ):
+    if is_bedrock_context:
         try:
             from agent.bedrock_adapter import get_bedrock_context_length
             return get_bedrock_context_length(model)
diff --git a/tests/agent/test_bedrock_adapter.py b/tests/agent/test_bedrock_adapter.py
index 16d771d8806b..2f8a6dc652fa 100644
--- a/tests/agent/test_bedrock_adapter.py
+++ b/tests/agent/test_bedrock_adapter.py
@@ -1181,6 +1181,22 @@ class TestBedrockContextLength:
         # Opus 4.6 has 1M context generally available (no beta header required).
         assert get_bedrock_context_length("anthropic.claude-opus-4-6-20250514-v1:0") == 1_000_000
 
+    def test_claude_fable_5(self):
+        from agent.bedrock_adapter import get_bedrock_context_length
+        # Fable is a 1M-context model. DEFAULT_CONTEXT_LENGTHS already maps
+        # claude-fable-5 -> 1M, but the Bedrock resolution path short-circuits
+        # to this table before consulting it, so without entries here every
+        # Fable inference profile fell through to
+        # BEDROCK_DEFAULT_CONTEXT_LENGTH (128K).
+        assert get_bedrock_context_length("us.anthropic.claude-fable-5") == 1_000_000
+        assert get_bedrock_context_length("global.anthropic.claude-fable-5") == 1_000_000
+        assert get_bedrock_context_length("anthropic.claude-fable-5-v1:0") == 1_000_000
+
+    def test_claude_opus_4_base_stays_200k(self):
+        from agent.bedrock_adapter import get_bedrock_context_length
+        # The original Opus 4 (no minor version) keeps the 200K window.
+        assert get_bedrock_context_length("anthropic.claude-opus-4-20250514-v1:0") == 200_000
+
     def test_claude_sonnet_versioned(self):
         from agent.bedrock_adapter import get_bedrock_context_length
         # Sonnet 4.6 has 1M context generally available (no beta header required).
diff --git a/tests/agent/test_model_metadata.py b/tests/agent/test_model_metadata.py
index 64f7573afcc2..166e0c1f97fa 100644
--- a/tests/agent/test_model_metadata.py
+++ b/tests/agent/test_model_metadata.py
@@ -1117,6 +1117,49 @@ class TestBedrockContextResolution:
         assert ctx == 200000
         mock_fetch.assert_not_called()
 
+    @patch("agent.model_metadata.fetch_endpoint_model_metadata")
+    def test_bedrock_claude_4_6_resolves_to_1m_before_probe(self, mock_fetch):
+        """Claude 4.6 Bedrock IDs resolve to the 1M table entry."""
+        ctx = get_model_context_length(
+            "us.anthropic.claude-sonnet-4-6",
+            provider="bedrock",
+            base_url="https://bedrock-runtime.us-east-2.amazonaws.com",
+        )
+        assert ctx == 1_000_000
+        mock_fetch.assert_not_called()
+
+    @patch("agent.model_metadata.fetch_endpoint_model_metadata")
+    def test_bedrock_claude_fable_resolves_to_1m_not_128k_default(self, mock_fetch):
+        """Fable on Bedrock must hit its own table entry, not the 128K default.
+
+        DEFAULT_CONTEXT_LENGTHS maps claude-fable-5 -> 1M, but the Bedrock
+        branch at step 1b returns get_bedrock_context_length() before that
+        catalog is ever consulted — so a missing BEDROCK_CONTEXT_LENGTHS
+        entry silently reported 128K for a 1M model.
+        """
+        ctx = get_model_context_length(
+            "global.anthropic.claude-fable-5",
+            provider="bedrock",
+            base_url="https://bedrock-runtime.us-east-2.amazonaws.com",
+        )
+        assert ctx == 1_000_000
+        mock_fetch.assert_not_called()
+
+    @patch("agent.model_metadata.fetch_endpoint_model_metadata")
+    def test_bedrock_claude_4_6_ignores_stale_200k_cache(self, mock_fetch, tmp_path):
+        """Old 200K Bedrock cache entries must not mask the 1M table entry."""
+        cache_file = tmp_path / "context_length_cache.yaml"
+        base_url = "https://bedrock-runtime.us-east-2.amazonaws.com"
+        with patch("agent.model_metadata._get_context_cache_path", return_value=cache_file):
+            save_context_length("us.anthropic.claude-sonnet-4-6", base_url, 200_000)
+            ctx = get_model_context_length(
+                "us.anthropic.claude-sonnet-4-6",
+                provider="bedrock",
+                base_url=base_url,
+            )
+        assert ctx == 1_000_000
+        mock_fetch.assert_not_called()
+
     @patch("agent.model_metadata.fetch_endpoint_model_metadata")
     def test_bedrock_url_without_provider_hint(self, mock_fetch):
         """bedrock-runtime host infers Bedrock even when provider is omitted."""