diff --git a/arcjet-bun/index.ts b/arcjet-bun/index.ts
index d487e3806..cdff494a3 100644
--- a/arcjet-bun/index.ts
+++ b/arcjet-bun/index.ts
@@ -197,7 +197,7 @@ function withClient<const Rules extends (Primitive | Product)[]>(
         props ?? {},
       ) as ArcjetRequest<ExtraProps<Rules>>;
 
-      return aj.protect(req);
+      return aj.protect({}, req);
     },
     handler(
       fetch: (
diff --git a/arcjet-next/index.ts b/arcjet-next/index.ts
index deffbaec5..ee8bd5dcd 100644
--- a/arcjet-next/index.ts
+++ b/arcjet-next/index.ts
@@ -300,7 +300,7 @@ function withClient<const Rules extends (Primitive | Product)[]>(
         ExtraProps<Rules>
       >;
 
-      return aj.protect(req);
+      return aj.protect({}, req);
     },
   });
 }
diff --git a/arcjet-node/index.ts b/arcjet-node/index.ts
index 79933996e..5c0f90707 100644
--- a/arcjet-node/index.ts
+++ b/arcjet-node/index.ts
@@ -212,7 +212,7 @@ function withClient<const Rules extends (Primitive | Product)[]>(
         ExtraProps<Rules>
       >;
 
-      return aj.protect(req);
+      return aj.protect({}, req);
     },
   });
 }
diff --git a/arcjet-sveltekit/index.ts b/arcjet-sveltekit/index.ts
index 23e4fb786..a05fef206 100644
--- a/arcjet-sveltekit/index.ts
+++ b/arcjet-sveltekit/index.ts
@@ -215,7 +215,7 @@ function withClient<const Rules extends (Primitive | Product)[]>(
         ExtraProps<Rules>
       >;
 
-      return aj.protect(req);
+      return aj.protect({}, req);
     },
   });
 }
diff --git a/arcjet/README.md b/arcjet/README.md
index 1b25ef2a8..cf10b5dad 100644
--- a/arcjet/README.md
+++ b/arcjet/README.md
@@ -62,6 +62,10 @@ const server = http.createServer(async function (
   req: http.IncomingMessage,
   res: http.ServerResponse,
 ) {
+  // Any sort of additional context that might want to be included for the
+  // execution of `protect()`. This is mostly only useful for writing adapters.
+  const ctx = {};
+
   // Construct an object with Arcjet request details
   const path = new URL(req.url || "", `http://${req.headers.host}`);
   const details = {
@@ -71,7 +75,7 @@ const server = http.createServer(async function (
     path: path.pathname,
   };
 
-  const decision = await aj.protect(details);
+  const decision = await aj.protect(ctx, details);
   console.log(decision);
 
   if (decision.isDenied()) {
diff --git a/arcjet/index.ts b/arcjet/index.ts
index 3a2b04cec..9431ee810 100644
--- a/arcjet/index.ts
+++ b/arcjet/index.ts
@@ -602,6 +602,14 @@ export type ExtraProps<Rules> = Rules extends []
       ? UnionToIntersection<PropsForRule<Rules[number]>>
       : never;
 
+/**
+ * Additional context that can be provided by adapters.
+ *
+ * Among other things, this could include the Arcjet API Key if it were only
+ * available in a runtime handler or IP details provided by a platform.
+ */
+export type ArcjetAdapterContext = Record<string, unknown>;
+
 /**
  * @property {string} ip - The IP address of the client.
  * @property {string} method - The HTTP method of the request.
@@ -1064,10 +1072,14 @@ export interface Arcjet<Props extends PlainObject> {
    * Make a decision about how to handle a request. This will analyze the
    * request locally where possible and call the Arcjet decision API.
    *
+   * @param {ArcjetAdapterContext} ctx - Additional context for this function call.
    * @param {ArcjetRequest} request - Details about the {@link ArcjetRequest} that Arcjet needs to make a decision.
    * @returns An {@link ArcjetDecision} indicating Arcjet's decision about the request.
    */
-  protect(request: ArcjetRequest<Props>): Promise<ArcjetDecision>;
+  protect(
+    ctx: ArcjetAdapterContext,
+    request: ArcjetRequest<Props>,
+  ): Promise<ArcjetDecision>;
 
   /**
    * Augments the client with another rule. Useful for varying rules based on
@@ -1112,6 +1124,7 @@ export default function arcjet<
 
   async function protect<Props extends PlainObject>(
     rules: ArcjetRule[],
+    ctx: ArcjetAdapterContext,
     request: ArcjetRequest<Props>,
   ) {
     // This goes against the type definition above, but users might call
@@ -1149,7 +1162,7 @@ export default function arcjet<
     logger.debug("fingerprint (%s): %s", runtime(), fingerprint);
     logger.timeEnd("fingerprint");
 
-    const context: ArcjetContext = { key, fingerprint };
+    const context: ArcjetContext = { key, ...ctx, fingerprint };
 
     if (rules.length < 1) {
       // TODO(#607): Error if no rules configured after deprecation period
@@ -1372,9 +1385,10 @@ export default function arcjet<
         return withRule(rule);
       },
       async protect(
+        ctx: ArcjetContext,
         request: ArcjetRequest<ExtraProps<typeof rules>>,
       ): Promise<ArcjetDecision> {
-        return protect(rules, request);
+        return protect(rules, ctx, request);
       },
     });
   }
@@ -1387,9 +1401,10 @@ export default function arcjet<
       return withRule(rule);
     },
     async protect(
+      ctx: ArcjetContext,
       request: ArcjetRequest<ExtraProps<typeof rootRules>>,
     ): Promise<ArcjetDecision> {
-      return protect(rootRules, request);
+      return protect(rootRules, ctx, request);
     },
   });
 }
diff --git a/arcjet/test/index.edge.test.ts b/arcjet/test/index.edge.test.ts
index 25fb19f23..9486f6ae4 100644
--- a/arcjet/test/index.edge.test.ts
+++ b/arcjet/test/index.edge.test.ts
@@ -69,20 +69,23 @@ describe("Arcjet: Env = Edge runtime", () => {
 
     const aj2 = aj.withRule(foobarbaz());
 
-    const decision = await aj2.protect({
-      abc: 123,
-      requested: 1,
-      email: "",
-      ip: "",
-      method: "",
-      protocol: "",
-      host: "",
-      path: "",
-      headers: new Headers(),
-      extra: {},
-      userId: "user123",
-      foobar: 123,
-    });
+    const decision = await aj2.protect(
+      {},
+      {
+        abc: 123,
+        requested: 1,
+        email: "",
+        ip: "",
+        method: "",
+        protocol: "",
+        host: "",
+        path: "",
+        headers: new Headers(),
+        extra: {},
+        userId: "user123",
+        foobar: 123,
+      },
+    );
 
     expect(decision.isErrored()).toBe(false);
   });
diff --git a/arcjet/test/index.node.test.ts b/arcjet/test/index.node.test.ts
index 3c4d539b7..3878acaf5 100644
--- a/arcjet/test/index.node.test.ts
+++ b/arcjet/test/index.node.test.ts
@@ -3440,7 +3440,7 @@ describe("SDK", () => {
       client,
     });
 
-    const decision = await aj.protect(request);
+    const decision = await aj.protect({}, request);
     expect(decision.conclusion).toEqual("DENY");
 
     expect(allowed.validate).toHaveBeenCalledTimes(1);
@@ -3469,7 +3469,7 @@ describe("SDK", () => {
       client,
     });
 
-    const decision = await aj.protect(request);
+    const decision = await aj.protect({}, request);
     expect(decision.conclusion).toEqual("ALLOW");
   });
 
@@ -3522,7 +3522,7 @@ describe("SDK", () => {
       client,
     });
 
-    const decision = await aj.protect(request);
+    const decision = await aj.protect({}, request);
     expect(decision.conclusion).toEqual("ERROR");
   });
 
@@ -3556,7 +3556,7 @@ describe("SDK", () => {
       client,
     });
 
-    const decision = await aj.protect(request);
+    const decision = await aj.protect({}, request);
     expect(decision.conclusion).toEqual("DENY");
 
     expect(denied.validate).toHaveBeenCalledTimes(1);
@@ -3599,7 +3599,7 @@ describe("SDK", () => {
       client,
     });
 
-    const decision = await aj.protect(request);
+    const decision = await aj.protect({}, request);
     expect(client.decide).toHaveBeenCalledTimes(1);
     expect(client.decide).toHaveBeenCalledWith(
       expect.objectContaining(context),
@@ -3652,7 +3652,7 @@ describe("SDK", () => {
       client,
     });
 
-    const decision = await aj.protect(request);
+    const decision = await aj.protect({}, request);
     expect(client.decide).toHaveBeenCalledTimes(1);
     expect(client.decide).toHaveBeenCalledWith(
       expect.objectContaining(context),
@@ -3711,7 +3711,7 @@ describe("SDK", () => {
       client,
     });
 
-    const decision = await aj.protect(request);
+    const decision = await aj.protect({}, request);
     expect(client.decide).toHaveBeenCalledTimes(1);
     expect(client.decide).toHaveBeenCalledWith(
       expect.objectContaining(context),
@@ -3762,7 +3762,7 @@ describe("SDK", () => {
       client,
     });
 
-    const _ = await aj.protect(request);
+    const _ = await aj.protect({}, request);
     expect(client.report).toHaveBeenCalledTimes(0);
     expect(client.decide).toHaveBeenCalledTimes(1);
     // TODO: Validate correct `ruleResults` are sent with `decide` when available
@@ -3803,7 +3803,7 @@ describe("SDK", () => {
       client,
     });
 
-    const decision = await aj.protect(request);
+    const decision = await aj.protect({}, request);
     expect(client.decide).toHaveBeenCalledTimes(1);
     expect(client.decide).toHaveBeenCalledWith(
       expect.objectContaining(context),
@@ -3857,7 +3857,7 @@ describe("SDK", () => {
       client,
     });
 
-    const _ = await aj.protect(request);
+    const _ = await aj.protect({}, request);
     expect(client.report).toHaveBeenCalledTimes(1);
     expect(client.report).toHaveBeenCalledWith(
       expect.objectContaining(context),
@@ -3908,7 +3908,7 @@ describe("SDK", () => {
       client,
     });
 
-    const _ = await aj.protect(request);
+    const _ = await aj.protect({}, request);
     expect(client.decide).toHaveBeenCalledTimes(0);
   });
 
@@ -3946,7 +3946,7 @@ describe("SDK", () => {
       client,
     });
 
-    const _ = await aj.protect(request);
+    const _ = await aj.protect({}, request);
 
     expect(client.report).toHaveBeenCalledTimes(0);
     expect(client.decide).toHaveBeenCalledTimes(1);
@@ -3995,7 +3995,7 @@ describe("SDK", () => {
       client,
     });
 
-    const decision = await aj.protect(request);
+    const decision = await aj.protect({}, request);
 
     expect(decision.isErrored()).toBe(false);
 
@@ -4004,7 +4004,7 @@ describe("SDK", () => {
 
     expect(decision.conclusion).toEqual("DENY");
 
-    const decision2 = await aj.protect(request);
+    const decision2 = await aj.protect({}, request);
 
     expect(decision2.isErrored()).toBe(false);
     expect(client.decide).toHaveBeenCalledTimes(1);
@@ -4062,7 +4062,7 @@ describe("SDK", () => {
       client,
     });
 
-    const _ = await aj.protect(request);
+    const _ = await aj.protect({}, request);
 
     expect(client.report).toHaveBeenCalledTimes(0);
     expect(client.decide).toHaveBeenCalledTimes(1);
@@ -4111,7 +4111,7 @@ describe("SDK", () => {
       client,
     });
 
-    const _ = await aj.protect(request);
+    const _ = await aj.protect({}, request);
 
     expect(errorLogSpy).toHaveBeenCalledTimes(1);
     expect(errorLogSpy).toHaveBeenCalledWith(
@@ -4163,7 +4163,7 @@ describe("SDK", () => {
       client,
     });
 
-    const _ = await aj.protect(request);
+    const _ = await aj.protect({}, request);
 
     expect(errorLogSpy).toHaveBeenCalledTimes(1);
     expect(errorLogSpy).toHaveBeenCalledWith(
@@ -4201,14 +4201,14 @@ describe("SDK", () => {
       client,
     });
 
-    const decision = await aj.protect(request);
+    const decision = await aj.protect({}, request);
 
     expect(decision.isDenied()).toBe(false);
 
     expect(client.decide).toBeCalledTimes(1);
     expect(client.report).toBeCalledTimes(1);
 
-    const decision2 = await aj.protect(request);
+    const decision2 = await aj.protect({}, request);
 
     expect(decision2.isDenied()).toBe(false);
 
@@ -4252,7 +4252,7 @@ describe("SDK", () => {
       client,
     });
 
-    const decision = await aj.protect(request);
+    const decision = await aj.protect({}, request);
 
     expect(decision.isErrored()).toBe(false);
 
@@ -4274,6 +4274,64 @@ describe("SDK", () => {
     );
   });
 
+  test("overrides `key` with custom context", async () => {
+    const client = {
+      decide: jest.fn(async () => {
+        return new ArcjetAllowDecision({
+          ttl: 0,
+          reason: new ArcjetTestReason(),
+          results: [],
+        });
+      }),
+      report: jest.fn(),
+    };
+
+    const key = "test-key";
+    const context = {
+      key,
+      fingerprint:
+        "fp_1_ac8547705f1f45c5050f1424700dfa3f6f2f681b550ca4f3c19571585aea7a2c",
+    };
+    const request = {
+      ip: "172.100.1.1",
+      method: "GET",
+      protocol: "http",
+      host: "example.com",
+      path: "/",
+      headers: new Headers([["User-Agent", "Mozilla/5.0"]]),
+      "extra-test": "extra-test-value",
+    };
+
+    const rule = testRuleRemote();
+
+    const aj = arcjet({
+      key,
+      rules: [[rule]],
+      client,
+    });
+
+    const decision = await aj.protect({ key: "overridden-key" }, request);
+
+    expect(decision.isErrored()).toBe(false);
+
+    expect(client.decide).toHaveBeenCalledTimes(1);
+    expect(client.decide).toHaveBeenCalledWith(
+      expect.objectContaining({ ...context, key: "overridden-key" }),
+      expect.objectContaining({
+        ip: request.ip,
+        method: request.method,
+        protocol: request.protocol,
+        host: request.host,
+        path: request.path,
+        headers: request.headers,
+        extra: {
+          "extra-test": "extra-test-value",
+        },
+      }),
+      [rule],
+    );
+  });
+
   test("reports and returns an ERROR decision if a `client.decide()` fails", async () => {
     const client = {
       decide: jest.fn(async () => {
@@ -4304,7 +4362,7 @@ describe("SDK", () => {
       client,
     });
 
-    const decision = await aj.protect(request);
+    const decision = await aj.protect({}, request);
 
     expect(decision.isErrored()).toBe(true);
 
@@ -4393,15 +4451,18 @@ describe("Arcjet: Env = Serverless Node runtime on Vercel", () => {
       rules: [rateLimit(config)],
       client,
     });
-    const decision = await aj.protect({
-      ip,
-      method,
-      protocol,
-      host,
-      path,
-      headers,
-      "extra-test": "extra-test-value",
-    });
+    const decision = await aj.protect(
+      {},
+      {
+        ip,
+        method,
+        protocol,
+        host,
+        path,
+        headers,
+        "extra-test": "extra-test-value",
+      },
+    );
 
     // If this fails, check the console an error related to the args passed to
     // the mocked decide service method above.
diff --git a/protocol/index.ts b/protocol/index.ts
index 2b4276b1c..000914680 100644
--- a/protocol/index.ts
+++ b/protocol/index.ts
@@ -745,6 +745,7 @@ export interface ArcjetShieldRule<Props extends {}> extends ArcjetRule<Props> {
 }
 
 export type ArcjetContext = {
+  [key: string]: unknown;
   key: string;
   fingerprint: string;
 };