diff --git a/packages/host-daemon-contract/src/protocol.ts b/packages/host-daemon-contract/src/protocol.ts
index 7e7793a875..c398b5d911 100644
--- a/packages/host-daemon-contract/src/protocol.ts
+++ b/packages/host-daemon-contract/src/protocol.ts
@@ -331,9 +331,13 @@
 // replaces the owning turn retains it. The wire shape is unchanged, but the
 // server-to-daemon payload semantics differ.
 //
+// Version 171 normalizes Claude model context-window reports against the
+// capacity implied by each model id. The usage event meaning changed across
+// the daemon boundary, so enrolled daemons must update with the server.
+//
 // The version mismatch is what triggers the enrolled daemon's automatic update
 // instead of an `invalid-message` reconnect loop.
-export const HOST_DAEMON_PROTOCOL_VERSION = 170 as const;
+export const HOST_DAEMON_PROTOCOL_VERSION = 171 as const;
 
 /**
  * Absolute ceiling for any executable artifact delivered to a host daemon —
diff --git a/packages/host-daemon-contract/test/contract.test.ts b/packages/host-daemon-contract/test/contract.test.ts
index 123b9bff45..2b3852f9c7 100644
--- a/packages/host-daemon-contract/test/contract.test.ts
+++ b/packages/host-daemon-contract/test/contract.test.ts
@@ -1046,7 +1046,7 @@ describe("host-daemon command schemas", () => {
   // mixed version. Version 113 carried the Devin Desktop open target rename
   // and remains part of the protocol lineage.
   it("uses the current host-daemon protocol version", () => {
-    expect(HOST_DAEMON_PROTOCOL_VERSION).toBe(170);
+    expect(HOST_DAEMON_PROTOCOL_VERSION).toBe(171);
     expect(HOST_ARTIFACT_MAX_BYTES).toBe(256 * 1024 * 1024);
   });
 
diff --git "a/packages/provider-bridge-protocol/recordings/claude-code/auth-failure/bridge\342\206\222runtime.current.ndjson" "b/packages/provider-bridge-protocol/recordings/claude-code/auth-failure/bridge\342\206\222runtime.current.ndjson"
index bd78bdf8e8..8c04864a41 100644
--- "a/packages/provider-bridge-protocol/recordings/claude-code/auth-failure/bridge\342\206\222runtime.current.ndjson"
+++ "b/packages/provider-bridge-protocol/recordings/claude-code/auth-failure/bridge\342\206\222runtime.current.ndjson"
@@ -6,4 +6,4 @@
 {"ts":1787279795704,"run":1787279794200,"seq":10.272727272727273,"dir":"bridge→runtime","line":"{\"jsonrpc\":\"2.0\",\"method\":\"thread/identity\",\"params\":{\"threadId\":\"thr_9e3ukzazz3\",\"providerThreadId\":\"54386450-a88e-4d9e-b4e1-8893a0c47239\",\"sessionRestorable\":true}}"}
 {"ts":1787279795705,"run":1787279794200,"seq":10.363636363636363,"dir":"bridge→runtime","line":"{\"jsonrpc\":\"2.0\",\"method\":\"thread/delta\",\"params\":{\"threadId\":\"thr_9e3ukzazz3\",\"deltas\":[{\"kind\":\"turn.open\"},{\"kind\":\"item.textClose\",\"key\":{\"channel\":\"assistant\"},\"channel\":\"agentMessage\",\"text\":\"Not logged in · Please run /login\"}]}}"}
 {"ts":1787279795706,"run":1787279794200,"seq":10.454545454545455,"dir":"bridge→runtime","line":"{\"jsonrpc\":\"2.0\",\"method\":\"provider/recovery\",\"params\":{\"threadId\":\"thr_9e3ukzazz3\",\"kind\":\"authRequired\",\"message\":\"Not logged in · Please run /login\",\"retryable\":false}}"}
-{"ts":1787279795707,"run":1787279794200,"seq":10.545454545454545,"dir":"bridge→runtime","line":"{\"jsonrpc\":\"2.0\",\"method\":\"thread/delta\",\"params\":{\"threadId\":\"thr_9e3ukzazz3\",\"deltas\":[{\"kind\":\"turn.open\"},{\"kind\":\"contextWindow\",\"used\":0,\"size\":null,\"estimated\":true,\"attach\":\"open\"},{\"kind\":\"usage\",\"total\":{\"totalTokens\":0,\"inputTokens\":0,\"cachedInputTokens\":0,\"outputTokens\":0,\"reasoningOutputTokens\":0},\"last\":{\"totalTokens\":0,\"inputTokens\":0,\"cachedInputTokens\":0,\"outputTokens\":0,\"reasoningOutputTokens\":0},\"modelContextWindow\":null},{\"kind\":\"provider.error\",\"message\":\"Provider error\",\"detail\":\"Not logged in · Please run /login\"},{\"kind\":\"turn.boundary\",\"status\":\"failed\",\"providerCheckpointId\":\"4a270486-b600-43dd-a6bd-07b72524f931\"}]}}"}
+{"ts":1787279795707,"run":1787279794200,"seq":10.545454545454545,"dir":"bridge→runtime","line":"{\"jsonrpc\":\"2.0\",\"method\":\"thread/delta\",\"params\":{\"threadId\":\"thr_9e3ukzazz3\",\"deltas\":[{\"kind\":\"turn.open\"},{\"kind\":\"contextWindow\",\"used\":0,\"size\":1000000,\"estimated\":true,\"attach\":\"open\"},{\"kind\":\"usage\",\"total\":{\"totalTokens\":0,\"inputTokens\":0,\"cachedInputTokens\":0,\"outputTokens\":0,\"reasoningOutputTokens\":0},\"last\":{\"totalTokens\":0,\"inputTokens\":0,\"cachedInputTokens\":0,\"outputTokens\":0,\"reasoningOutputTokens\":0},\"modelContextWindow\":null},{\"kind\":\"provider.error\",\"message\":\"Provider error\",\"detail\":\"Not logged in · Please run /login\"},{\"kind\":\"turn.boundary\",\"status\":\"failed\",\"providerCheckpointId\":\"4a270486-b600-43dd-a6bd-07b72524f931\"}]}}"}
diff --git a/plugins/provider-claude-code/src/bridge/__tests__/bridge.test.ts b/plugins/provider-claude-code/src/bridge/__tests__/bridge.test.ts
index a0c9b8643f..a400b8b3bd 100644
--- a/plugins/provider-claude-code/src/bridge/__tests__/bridge.test.ts
+++ b/plugins/provider-claude-code/src/bridge/__tests__/bridge.test.ts
@@ -4611,13 +4611,7 @@ describe("canonical model context-window hint", () => {
     permissionEscalation: null,
   };
 
-  // Claude reports `modelUsage.contextWindow` on some results and omits it on
-  // others. The legacy adapter seeded a model-derived fallback on every
-  // command plan that carried a model; the canonical bridge has no command
-  // plan, so it seeds the translator at session construction instead. Without
-  // that seeding, capacity read as unknown for every result Claude sent
-  // without the field — notably the 1M `[1m]` aliases.
-  it("seeds the model-derived context window for canonical sessions", async () => {
+  it("uses Fable's Claude Code capacity through a custom API endpoint", async () => {
     const bridge = createBridgeJsonRpcTestHarness(handleLine);
     const queries: ControlledClaudeQuery[] = [];
     queryMock.mockImplementation(() => {
@@ -4631,22 +4625,32 @@ describe("canonical model context-window hint", () => {
         threadId: "thread-context-hint",
         cwd: "/tmp/worktree",
         instructionMode: "append",
-        options: { ...canonicalOptions, model: "claude-opus-4-7[1m]" },
+        options: {
+          ...canonicalOptions,
+          model: "claude-fable-5",
+          envVars: {
+            ANTHROPIC_BASE_URL: "http://127.0.0.1:8317",
+          },
+        },
       });
       await bridge.waitForResponse(1);
 
+      expect(getLatestQueryOptions().env?.ANTHROPIC_BASE_URL).toBe(
+        "http://127.0.0.1:8317",
+      );
+
       bridge.sendRequest(2, "turn/start", {
         threadId: "thread-context-hint",
         providerThreadId: "thread-context-hint",
         clientRequestId: "creq_23456789ab",
         input: [{ type: "text", text: "hello", mentions: [] }],
-        options: { ...canonicalOptions, model: "claude-opus-4-7[1m]" },
+        options: { ...canonicalOptions, model: "claude-fable-5" },
       });
       await readNextPrompt(getLatestQueryCall());
       await bridge.waitForResponse(2);
 
-      // A result with token usage but no `modelUsage`: the only capacity
-      // source left is the seeded hint.
+      // The SDK reports its legacy 200k BYOK fallback through a custom endpoint,
+      // although current Fable providers support 1M.
       queries[0]?.emit({
         type: "result",
         subtype: "success",
@@ -4663,6 +4667,11 @@ describe("canonical model context-window hint", () => {
           cache_creation_input_tokens: 30,
           cache_read_input_tokens: 40,
         },
+        modelUsage: {
+          "claude-fable-5": {
+            contextWindow: 200_000,
+          },
+        },
         session_id: "session-1",
       } as unknown as SDKMessage);
       await bridge.flushWork();
@@ -4682,6 +4691,21 @@ describe("canonical model context-window hint", () => {
       expect(contextWindowEvents.at(-1)?.contextWindowUsage).toMatchObject({
         modelContextWindow: 1_000_000,
       });
+
+      const tokenUsageEvents = assembleCapturedThreadEvents(
+        bridge.messages,
+        "claude-code",
+      ).filter(
+        (
+          event,
+        ): event is Extract<
+          ThreadEvent,
+          { type: "thread/tokenUsage/updated" }
+        > => event.type === "thread/tokenUsage/updated",
+      );
+      expect(tokenUsageEvents.at(-1)?.tokenUsage).toMatchObject({
+        modelContextWindow: 1_000_000,
+      });
     } finally {
       queries[0]?.finish();
       bridge.restore();
diff --git a/plugins/provider-claude-code/src/bridge/bridge.ts b/plugins/provider-claude-code/src/bridge/bridge.ts
index 88b635e352..4752902f63 100644
--- a/plugins/provider-claude-code/src/bridge/bridge.ts
+++ b/plugins/provider-claude-code/src/bridge/bridge.ts
@@ -969,13 +969,10 @@ function withTrackedPermissionEscalation(
 }
 
 /**
- * Seed the translator's context-window fallback from the selected model.
+ * Seed the translator's context-window hint from the selected model.
  *
- * Claude reports `modelUsage.contextWindow` on some results and omits it on
- * others; when it is missing the translator falls back to the capacity implied
- * by the model id (notably the 1M `[1m]` aliases). The bridge seeds the hint
- * here, on every session construction and every turn that carries a model —
- * without it, capacity reads as unknown whenever Claude omits the field.
+ * Claude can omit `modelUsage.contextWindow`. Seed the selected model as its
+ * fallback; reported model entries normalize their own known capacity.
  */
 function seedModelContextWindowHint(
   threadSession: ThreadSession,
diff --git a/plugins/provider-claude-code/src/delta-translation.ts b/plugins/provider-claude-code/src/delta-translation.ts
index 1ef8fb4970..d8284fcc22 100644
--- a/plugins/provider-claude-code/src/delta-translation.ts
+++ b/plugins/provider-claude-code/src/delta-translation.ts
@@ -1495,10 +1495,10 @@ export function createClaudeDeltaTranslator(
   }
 
   /**
-   * Seed the context-window fallback from the selected model. Claude reports
-   * `modelUsage.contextWindow` on some results and omits it on others; when
-   * missing, capacity falls back to what the model id implies (notably the 1M
-   * `[1m]` aliases). Called at session construction and live model changes.
+   * Seed the context-window hint from the selected model. The model's known
+   * Claude Code capacity is a floor for `modelUsage.contextWindow`, which can
+   * report the generic 200k window through custom Anthropic endpoints. Called
+   * at session construction and live model changes.
    */
   function setClaudeModelContextWindowHint(
     threadId: string,
diff --git a/plugins/provider-claude-code/src/delta-translation.usage.test.ts b/plugins/provider-claude-code/src/delta-translation.usage.test.ts
index ef2da38988..0ebdaa8c34 100644
--- a/plugins/provider-claude-code/src/delta-translation.usage.test.ts
+++ b/plugins/provider-claude-code/src/delta-translation.usage.test.ts
@@ -375,7 +375,7 @@ describe("claude usage and fixture translation (delta path)", () => {
     );
   });
 
-  // The four cases below pin the translator's use of sdk-extraction.ts's
+  // The cases below pin the translator's use of sdk-extraction.ts's
   // resolveClaudeModelContextWindowHint. The canonical bridge calls
   // setClaudeModelContextWindowHint from session construction and from the
   // live model change; that the bridge really calls it is pinned separately
diff --git a/plugins/provider-claude-code/src/sdk-extraction.ts b/plugins/provider-claude-code/src/sdk-extraction.ts
index fd61d72878..f694e73b99 100644
--- a/plugins/provider-claude-code/src/sdk-extraction.ts
+++ b/plugins/provider-claude-code/src/sdk-extraction.ts
@@ -294,7 +294,8 @@ export function extractClaudeContextWindowUsage(
     args.message.modelUsage,
   );
   const modelContextWindow = parsedModelUsage.success
-    ? extractModelContextWindow(parsedModelUsage.data)
+    ? (extractModelContextWindow(parsedModelUsage.data) ??
+      args.fallbackModelContextWindow)
     : args.fallbackModelContextWindow;
   const usedTokens = args.latestRequestContextTokens ?? null;
 
@@ -356,9 +357,17 @@ function extractModelContextWindow(
   if (!modelUsage) return null;
 
   let largestContextWindow: number | null = null;
-  for (const usage of Object.values(modelUsage)) {
-    const contextWindow = toPositiveNumber(usage.contextWindow);
-    if (contextWindow === undefined) continue;
+  for (const [model, usage] of Object.entries(modelUsage)) {
+    const reportedContextWindow = toPositiveNumber(usage.contextWindow);
+    if (reportedContextWindow === undefined) continue;
+
+    // The SDK's 200k custom-endpoint value is a legacy BYOK fallback. Current
+    // Fable providers, including Bedrock, support 1M.
+    const modelContextWindow = resolveClaudeModelContextWindowHint(model);
+    const contextWindow =
+      modelContextWindow === null
+        ? reportedContextWindow
+        : Math.max(reportedContextWindow, modelContextWindow);
     if (largestContextWindow === null || contextWindow > largestContextWindow) {
       largestContextWindow = contextWindow;
     }