diff --git a/open-sse/config/agyModels.ts b/open-sse/config/agyModels.ts
index d836888b7f..919b97e957 100644
--- a/open-sse/config/agyModels.ts
+++ b/open-sse/config/agyModels.ts
@@ -19,7 +19,7 @@ export const AGY_PUBLIC_MODELS = Object.freeze([
   {
     id: "claude-opus-4-6-thinking",
     name: "Claude Opus 4.6 (Thinking)",
-    contextLength: 200000,
+    contextLength: 1048576,
     maxOutputTokens: 65536,
     supportsReasoning: true,
     supportsVision: true,
@@ -28,7 +28,7 @@ export const AGY_PUBLIC_MODELS = Object.freeze([
   {
     id: "claude-sonnet-4-6",
     name: "Claude Sonnet 4.6 (Thinking)",
-    contextLength: 200000,
+    contextLength: 1048576,
     maxOutputTokens: 65536,
     supportsReasoning: true,
     supportsVision: true,
diff --git a/open-sse/config/antigravityModelAliases.ts b/open-sse/config/antigravityModelAliases.ts
index a88ab804c0..3feebf495b 100644
--- a/open-sse/config/antigravityModelAliases.ts
+++ b/open-sse/config/antigravityModelAliases.ts
@@ -7,7 +7,7 @@ export const ANTIGRAVITY_PUBLIC_MODELS = Object.freeze([
   {
     id: "claude-sonnet-5",
     name: "Claude Sonnet 5 (Thinking)",
-    contextLength: 200000,
+    contextLength: 1048576,
     maxOutputTokens: 65536,
     supportsReasoning: true,
     supportsVision: true,
@@ -16,7 +16,7 @@ export const ANTIGRAVITY_PUBLIC_MODELS = Object.freeze([
   {
     id: "claude-opus-4-6-thinking",
     name: "Claude Opus 4.6 (Thinking)",
-    contextLength: 200000,
+    contextLength: 1048576,
     maxOutputTokens: 65536,
     supportsReasoning: true,
     supportsVision: true,
@@ -25,7 +25,7 @@ export const ANTIGRAVITY_PUBLIC_MODELS = Object.freeze([
   {
     id: "claude-sonnet-4-6",
     name: "Claude Sonnet 4.6 (Thinking)",
-    contextLength: 200000,
+    contextLength: 1048576,
     maxOutputTokens: 65536,
     supportsReasoning: true,
     supportsVision: true,
diff --git a/open-sse/config/providers/registry/claude/index.ts b/open-sse/config/providers/registry/claude/index.ts
index 19b2c5a509..d142872de8 100644
--- a/open-sse/config/providers/registry/claude/index.ts
+++ b/open-sse/config/providers/registry/claude/index.ts
@@ -81,7 +81,7 @@ export const claudeProvider: RegistryEntry = {
       id: "claude-sonnet-4-6",
       name: "Claude 4.6 Sonnet",
       supportsXHighEffort: false,
-      contextLength: 200000,
+      contextLength: 1000000,
       maxOutputTokens: 64000,
     },
     {
diff --git a/open-sse/services/claudeCodeCompatible.ts b/open-sse/services/claudeCodeCompatible.ts
index 01b021579f..a33e4cd09e 100644
--- a/open-sse/services/claudeCodeCompatible.ts
+++ b/open-sse/services/claudeCodeCompatible.ts
@@ -56,6 +56,7 @@ const CLAUDE_CODE_COMPATIBLE_DEFAULT_SYSTEM_BLOCKS = [
 const CONTEXT_1M_SUPPORTED_MODELS = [
   "claude-fable-5",
   "claude-sonnet-5",
+  "claude-sonnet-4-6",
   "claude-opus-4-8",
   "claude-opus-4-7",
   "claude-opus-4-6",
diff --git a/tests/unit/antigravity-model-aliases.test.ts b/tests/unit/antigravity-model-aliases.test.ts
index 718250c8ec..9c80666ff5 100644
--- a/tests/unit/antigravity-model-aliases.test.ts
+++ b/tests/unit/antigravity-model-aliases.test.ts
@@ -99,21 +99,27 @@ test("isUserCallableAntigravityModelId only allows public chat-capable model IDs
 
 test("ANTIGRAVITY_PUBLIC_MODELS exposes captured Antigravity 2.0.1 names and capabilities", () => {
   // #3184: Claude is exposed in the antigravity catalog (same backend as `agy`, verified).
+  // #7129: Opus 4.6, Sonnet 4.6, and Sonnet 5 graduated to a 1M-token context window at GA
+  // (Anthropic docs, platform.claude.com/docs/en/build-with-claude/context-windows: "Claude
+  // Opus 4.8, Claude Opus 4.7, Claude Opus 4.6, Claude Sonnet 5, and Claude Sonnet 4.6 have a
+  // 1M-token context window ... on the Claude API, Amazon Bedrock, Google Cloud, and Microsoft
+  // Foundry" — Google Cloud coverage extends to the Antigravity-hosted ids exercised here).
   assert.deepEqual(getPublicModel("claude-opus-4-6-thinking"), {
     id: "claude-opus-4-6-thinking",
     name: "Claude Opus 4.6 (Thinking)",
-    contextLength: 200000,
+    contextLength: 1048576,
     maxOutputTokens: 65536,
     supportsReasoning: true,
     supportsVision: true,
     toolCalling: true,
   });
   assert.equal(getPublicModel("claude-sonnet-4-6").name, "Claude Sonnet 4.6 (Thinking)");
+  assert.equal(getPublicModel("claude-sonnet-4-6").contextLength, 1048576);
   // claude-sonnet-5 was added to the Antigravity catalog alongside the existing Claude entries.
   assert.deepEqual(getPublicModel("claude-sonnet-5"), {
     id: "claude-sonnet-5",
     name: "Claude Sonnet 5 (Thinking)",
-    contextLength: 200000,
+    contextLength: 1048576,
     maxOutputTokens: 65536,
     supportsReasoning: true,
     supportsVision: true,
diff --git a/tests/unit/auto-combo-context-advertising.test.ts b/tests/unit/auto-combo-context-advertising.test.ts
index e316cdae52..390b1265e7 100644
--- a/tests/unit/auto-combo-context-advertising.test.ts
+++ b/tests/unit/auto-combo-context-advertising.test.ts
@@ -64,7 +64,8 @@ test("computeAdvertisedLimits returns MAX of candidates' known context windows",
     "virtualFactory should export computeAdvertisedLimits()"
   );
 
-  // gemini has registry defaultContextLength=1048576; claude has 200000.
+  // gemini has registry defaultContextLength=1048576; claude-sonnet-4-6 has 1000000 (#7129:
+  // 1M GA per Anthropic docs) -- gemini's binary-1M window still wins as the MAX.
   const result = computeAdvertisedLimits([
     { provider: "claude", model: "claude-sonnet-4-6" },
     { provider: "gemini", model: "gemini-2.5-pro" },
@@ -171,7 +172,10 @@ test("resolveComboContextLimit regression: claude target must not be compressed
     model: "claude-sonnet-4-6",
     comboTargetLimits: [8000],
   });
-  assert.equal(result.limit, 200000);
+  // #7129: claude-sonnet-4-6's own registry limit is 1M GA (was 200000) -- the point of this
+  // regression test is that the target's OWN limit wins over the 8k sibling, not the specific
+  // magic number, so the expectation tracks the registry's current (correct) value.
+  assert.equal(result.limit, 1000000);
   assert.equal(result.source, "target");
 });
 
diff --git a/tests/unit/claude-context-1m-supported-models.test.ts b/tests/unit/claude-context-1m-supported-models.test.ts
new file mode 100644
index 0000000000..dbac4c55e2
--- /dev/null
+++ b/tests/unit/claude-context-1m-supported-models.test.ts
@@ -0,0 +1,153 @@
+import test from "node:test";
+import assert from "node:assert/strict";
+import fs from "node:fs";
+import path from "node:path";
+
+const REPO_ROOT = path.resolve(import.meta.dirname, "../..");
+
+// ─── Parse CONTEXT_1M_SUPPORTED_MODELS from source (no module import needed) ───
+
+function parseSupportedModels(): string[] {
+  const src = fs.readFileSync(
+    path.join(REPO_ROOT, "open-sse/services/claudeCodeCompatible.ts"),
+    "utf8"
+  );
+  // Strip type annotations before matching to handle `const X: string[] = [...]`
+  const match = src
+    .replace(/:\s*\w+(\[\])?/, "")
+    .match(/CONTEXT_1M_SUPPORTED_MODELS\s*=\s*\[([\s\S]*?)\]/);
+  if (!match) throw new Error("CONTEXT_1M_SUPPORTED_MODELS not found in source");
+  return match[1]
+    .split(",")
+    .map((s) => s.replace(/["'\s]/g, "").toLowerCase())
+    .filter(Boolean);
+}
+
+// ─── Parse Claude models from provider registry (source-level) ───
+// Uses brace-counting to isolate each model block within the models array,
+// avoiding false matches on the provider-level id field.
+
+function parseClaudeRegistryModels(): Array<{
+  provider: string;
+  modelId: string;
+  contextLength: number;
+}> {
+  const registryDir = path.join(REPO_ROOT, "open-sse/config/providers/registry/claude");
+  const results: Array<{
+    provider: string;
+    modelId: string;
+    contextLength: number;
+  }> = [];
+
+  for (const file of fs.readdirSync(registryDir).filter((f) => f.endsWith(".ts"))) {
+    const src = fs.readFileSync(path.join(registryDir, file), "utf8");
+
+    // Extract provider id
+    const providerIdMatch = src.match(/id:\s*["']([^"']+)["']/);
+    const providerId = providerIdMatch?.[1] ?? file.replace(".ts", "");
+
+    // Find the models array
+    const modelsStart = src.indexOf("models:");
+    if (modelsStart === -1) continue;
+    const arrayStart = src.indexOf("[", modelsStart);
+    if (arrayStart === -1) continue;
+
+    // Extract individual model objects using brace counting.
+    // Skips any non-model nested braces by requiring both id and contextLength
+    // in the same brace-delimited block.
+    let braceDepth = 0;
+    let objStart = -1;
+    const modelBlocks: string[] = [];
+    for (let i = arrayStart; i < src.length; i++) {
+      if (src[i] === "{") {
+        if (braceDepth === 0) objStart = i;
+        braceDepth++;
+      } else if (src[i] === "}") {
+        braceDepth--;
+        if (braceDepth === 0 && objStart !== -1) {
+          modelBlocks.push(src.slice(objStart, i + 1));
+          objStart = -1;
+        }
+      } else if (src[i] === "]" && braceDepth === 0) {
+        break;
+      }
+    }
+
+    for (const block of modelBlocks) {
+      const idMatch = block.match(/id:\s*["']([^"']+)["']/);
+      const ctxMatch = block.match(/contextLength:\s*(\d+)/);
+      if (idMatch && ctxMatch) {
+        results.push({
+          provider: providerId,
+          modelId: idMatch[1].toLowerCase(),
+          contextLength: parseInt(ctxMatch[1], 10),
+        });
+      }
+    }
+  }
+  return results;
+}
+
+const CONTEXT_1M_THRESHOLD = 200_000;
+
+function isModel1mSupported(modelId: string, supportedModels: string[]): boolean {
+  const normalized = modelId.replace(/:.*$/, "").toLowerCase();
+  return supportedModels.some((s) => normalized === s || normalized.startsWith(`${s}-`));
+}
+
+// ─── Sanity: parser must find at least one model ───
+
+test("parser finds at least one Claude model in the registry", () => {
+  const models = parseClaudeRegistryModels();
+  assert.ok(
+    models.length > 0,
+    "parseClaudeRegistryModels returned 0 models — check that open-sse/config/providers/registry/claude/ exists and contains model definitions"
+  );
+});
+
+// ─── Forward: every high-context Claude model must be in the allowlist ───
+
+test("every Claude model with contextLength > 200K is in CONTEXT_1M_SUPPORTED_MODELS", () => {
+  const supportedModels = parseSupportedModels();
+  const claudeModels = parseClaudeRegistryModels();
+  const violations: string[] = [];
+
+  for (const m of claudeModels) {
+    if (m.contextLength > CONTEXT_1M_THRESHOLD && !isModel1mSupported(m.modelId, supportedModels)) {
+      violations.push(`${m.provider}/${m.modelId} (contextLength=${m.contextLength})`);
+    }
+  }
+
+  assert.deepEqual(
+    violations,
+    [],
+    `Claude models with contextLength > 200K missing from CONTEXT_1M_SUPPORTED_MODELS.\n` +
+      `Add the model prefix to the allowlist in claudeCodeCompatible.ts.\n` +
+      `Violations:\n  ${violations.join("\n  ")}`
+  );
+});
+
+// ─── Reverse: every allowlist entry must have a matching high-context model ───
+
+test("every CONTEXT_1M_SUPPORTED_MODELS entry has a matching Claude model with contextLength > 200K", () => {
+  const supportedModels = parseSupportedModels();
+  const claudeModels = parseClaudeRegistryModels();
+  const orphans: string[] = [];
+
+  for (const supported of supportedModels) {
+    const found = claudeModels.some(
+      (m) =>
+        m.contextLength > CONTEXT_1M_THRESHOLD &&
+        (m.modelId === supported || m.modelId.startsWith(`${supported}-`))
+    );
+    if (!found) orphans.push(supported);
+  }
+
+  assert.deepEqual(
+    orphans,
+    [],
+    `CONTEXT_1M_SUPPORTED_MODELS entries with no matching high-context Claude model.\n` +
+      `Remove stale entries or check model id spelling.\n` +
+      `Orphans:\n  ${orphans.join("\n  ")}`
+  );
+});
diff --git a/tests/unit/models-catalog-route.test.ts b/tests/unit/models-catalog-route.test.ts
index 0a7b1f897e..1a51272b69 100644
--- a/tests/unit/models-catalog-route.test.ts
+++ b/tests/unit/models-catalog-route.test.ts
@@ -1419,7 +1419,7 @@ test("v1 models catalog auto-calculates combo context_length from targets when n
   });
 
   // Create a combo with targets having different context limits.
-  // openai/gpt-4o context = 128000, claude/claude-sonnet-4-6 = 200000.
+  // openai/gpt-4o context = 128000, claude/claude-sonnet-4-6 = 1000000 (#7129: 1M GA).
   // The combo should expose context_length = min = 128000.
   const combo = await combosDb.createCombo({
     name: "auto-context-combo",