diff --git a/open-sse/executors/kiro.js b/open-sse/executors/kiro.js
index 3034f725..bc8df516 100644
--- a/open-sse/executors/kiro.js
+++ b/open-sse/executors/kiro.js
@@ -1,8 +1,10 @@
 import { BaseExecutor } from "./base.js";
 import { PROVIDERS } from "../config/providers.js";
+import { resolveKiroModel } from "../config/kiroConstants.js";
 import { v4 as uuidv4 } from "uuid";
 import { refreshKiroToken } from "../services/tokenRefresh.js";
 import { SSE_DONE, SSE_HEADERS } from "../utils/sseConstants.js";
+import { getCapabilitiesForModel } from "../providers/capabilities.js";
 
 /**
  * KiroExecutor - Executor for Kiro AI (AWS CodeWhisperer)
@@ -101,6 +103,8 @@ export class KiroExecutor extends BaseExecutor {
     let chunkIndex = 0;
     const responseId = `chatcmpl-${Date.now()}`;
     const created = Math.floor(Date.now() / 1000);
+    const capabilityModel = resolveKiroModel(model).upstream;
+    const contextWindow = getCapabilitiesForModel("kiro", capabilityModel).contextWindow || 200000;
     const state = {
       endDetected: false,
       finishEmitted: false,
@@ -357,9 +361,8 @@ export class KiroExecutor extends BaseExecutor {
                 : 0;
 
               // Estimate input tokens from contextUsagePercentage
-              // Kiro models typically have 200k context window
               const estimatedInputTokens = state.contextUsagePercentage > 0
-                ? Math.floor(state.contextUsagePercentage * 200000 / 100)
+                ? Math.floor(state.contextUsagePercentage * contextWindow / 100)
                 : 0;
 
               state.usage = {
diff --git a/open-sse/providers/capabilities.js b/open-sse/providers/capabilities.js
index 2cc61036..bc5a69f3 100644
--- a/open-sse/providers/capabilities.js
+++ b/open-sse/providers/capabilities.js
@@ -71,10 +71,14 @@ export function capabilitiesFromServiceKind(kind) {
  * otherwise mis-match. Only declare deltas vs DEFAULT.
  */
 export const MODEL_CAPABILITIES = {
-  // Claude 4.6/4.7 have 1M context + adaptive thinking (override generic claude pattern)
+  // Claude 4.6/4.7/4.8 have 1M context + adaptive thinking (override generic claude pattern)
   "claude-opus-4.6":   { vision: true, reasoning: true, search: true, thinkingFormat: "claude-adaptive", contextWindow: 1000000, maxOutput: 128000 },
   "claude-opus-4.7":   { vision: true, reasoning: true, search: true, thinkingFormat: "claude-adaptive", contextWindow: 1000000, maxOutput: 128000 },
+  "claude-opus-4.8":   { vision: true, reasoning: true, search: true, thinkingFormat: "claude-adaptive", contextWindow: 1000000, maxOutput: 128000 },
   "claude-opus-4-6":   { vision: true, reasoning: true, search: true, thinkingFormat: "claude-adaptive", contextWindow: 1000000, maxOutput: 128000 },
+  "claude-opus-4-8":   { vision: true, reasoning: true, search: true, thinkingFormat: "claude-adaptive", contextWindow: 1000000, maxOutput: 128000 },
+  "claude-opus-4.8-thinking": { vision: true, reasoning: true, search: true, thinkingFormat: "claude-adaptive", contextWindow: 1000000, maxOutput: 128000 },
+  "claude-opus-4-8-thinking": { vision: true, reasoning: true, search: true, thinkingFormat: "claude-adaptive", contextWindow: 1000000, maxOutput: 128000 },
   "claude-sonnet-4.6": { vision: true, reasoning: true, search: true, thinkingFormat: "claude-adaptive", contextWindow: 1000000, maxOutput: 64000 },
   "claude-sonnet-4-6": { vision: true, reasoning: true, search: true, thinkingFormat: "claude-adaptive", contextWindow: 1000000, maxOutput: 64000 },
 
diff --git a/tests/unit/capabilities.test.js b/tests/unit/capabilities.test.js
new file mode 100644
index 00000000..3839809b
--- /dev/null
+++ b/tests/unit/capabilities.test.js
@@ -0,0 +1,12 @@
+import { describe, expect, it } from "vitest";
+import { getCapabilitiesForModel } from "../../open-sse/providers/capabilities.js";
+
+describe("getCapabilitiesForModel", () => {
+  it("reports Kiro Claude Opus 4.8 as a 1M context model", () => {
+    expect(getCapabilitiesForModel("kiro", "claude-opus-4.8").contextWindow).toBe(1000000);
+    expect(getCapabilitiesForModel("kiro", "anthropic/claude-opus-4.8").contextWindow).toBe(1000000);
+    expect(getCapabilitiesForModel("kiro", "claude-opus-4-8").contextWindow).toBe(1000000);
+    expect(getCapabilitiesForModel("kiro", "claude-opus-4.8-thinking").contextWindow).toBe(1000000);
+    expect(getCapabilitiesForModel("kiro", "claude-opus-4-8-thinking").contextWindow).toBe(1000000);
+  });
+});