oven-sh · Jarred-Sumner · Aug 15, 2026 · Aug 15, 2026 · Aug 15, 2026 · Aug 15, 2026
diff --git a/docs/docs.json b/docs/docs.json
@@ -108,6 +108,7 @@
             "expanded": true,
             "pages": [
               "/runtime/networking/fetch",
+              "/runtime/networking/cloud-auth",
               "/runtime/http/websockets",
               "/runtime/networking/tcp",
               "/runtime/networking/udp",

diff --git a/docs/runtime/networking/cloud-auth.mdx b/docs/runtime/networking/cloud-auth.mdx
@@ -0,0 +1,169 @@
+---
+title: AWS & Google Cloud auth
+description: Call AWS and Google Cloud APIs from Bun with the machine's own credentials — no SDK required
+---
+
+Bun can authenticate requests to AWS and Google Cloud the same way their CLIs and SDKs do: from environment variables, config files, SSO sessions, or the instance / container / pod the code is running on. Bun fetches credentials without blocking the JavaScript thread on the network, caches them, and refreshes ones that are in use in the background shortly before they expire.
+
+```ts
+// SigV4-signed request with whatever credentials this machine has
+const queues = await Bun.aws.fetch("https://sqs.us-east-1.amazonaws.com/?Action=ListQueues");
+
+// Bearer token from Application Default Credentials
+const buckets = await Bun.gcp.fetch("https://storage.googleapis.com/storage/v1/b?project=my-project");
+```
+
+`Bun.aws` and `Bun.gcp` are ready-made clients using ambient credentials. For several accounts, regions or key files at once, construct more:
+
+```ts
+const prod = new Bun.AWSClient({ profile: "prod", region: "eu-west-1" });
+const deployer = new Bun.GCPClient({ keyFile: "/secrets/deployer.json" });
+```
+
+`Bun.s3`, `new S3Client()` and `fetch("s3://…")` use the AWS chain automatically when no `accessKeyId`/`secretAccessKey` is configured — see [S3 › Credentials](/runtime/s3#credentials).
+
+## AWS
+
+### Where credentials come from
+
+When a request needs AWS credentials and none were passed explicitly, Bun tries, in order:
+
+1. `AWS_ACCESS_KEY_ID` + `AWS_SECRET_ACCESS_KEY` (+ `AWS_SESSION_TOKEN`)
+2. The profile named by the `profile` option, `AWS_PROFILE`, or `default`, from `~/.aws/credentials` and `~/.aws/config` (or `AWS_SHARED_CREDENTIALS_FILE` / `AWS_CONFIG_FILE`). A profile may hold static keys, `role_arn` + `source_profile` / `credential_source` (STS `AssumeRole`), `web_identity_token_file`, `credential_process`, or IAM Identity Center settings (`sso_session` / `sso_*`, using the token that `aws sso login` cached).
+3. `AWS_WEB_IDENTITY_TOKEN_FILE` + `AWS_ROLE_ARN` — EKS service-account roles (IRSA)
+4. The container credentials endpoint — `AWS_CONTAINER_CREDENTIALS_RELATIVE_URI` or `AWS_CONTAINER_CREDENTIALS_FULL_URI` (+ `AWS_CONTAINER_AUTHORIZATION_TOKEN[_FILE]`), set by ECS, EKS Pod Identity, App Runner, …
+5. EC2 instance metadata (IMDSv2). Honours `AWS_EC2_METADATA_DISABLED`, `AWS_EC2_METADATA_SERVICE_ENDPOINT[_MODE]`, `AWS_EC2_METADATA_V1_DISABLED`, `AWS_METADATA_SERVICE_TIMEOUT` and `AWS_METADATA_SERVICE_NUM_ATTEMPTS`.
+
+A source that isn't configured is skipped. A source that _is_ configured but fails (an expired SSO session, an STS `AccessDenied`, a `credential_process` that exits non-zero) is an error — Bun does not silently fall through to the next one.
+
+As in the AWS SDKs, selecting a profile (`AWS_PROFILE` or the `profile` option) takes precedence over exported `AWS_ACCESS_KEY_ID` / `AWS_SECRET_ACCESS_KEY`. Environment variables are read from `process.env` when credentials are resolved, so setting `process.env.AWS_PROFILE` at startup works.
+
+### `new Bun.AWSClient(options?)` / `Bun.aws`
+
+An `AWSClient` bundles signing defaults: `region`, `service`, `profile` or `accessKeyId`/`secretAccessKey`/`sessionToken`, and `endpoint` (a base URL for path-only requests, e.g. LocalStack). Every method accepts the same options to override them per call. `Bun.aws` is the instance with no overrides.
+
+```ts
+const prod = new Bun.AWSClient({ profile: "prod", region: "eu-west-1" });
+prod.region; // "eu-west-1"
+prod.profile; // "prod"
+```
+
+### `client.credentials()`
+
+Resolve (or return the cached) credentials. Useful for handing them to another SDK, or just to see what Bun found.
+
+```ts
+const creds = await Bun.aws.credentials();
+// {
+//   accessKeyId: "ASIA…",
+//   secretAccessKey: "…",
+//   sessionToken: "…",          // temporary credentials only
+//   expiration: 2026-01-01T…,   // temporary credentials only
+//   region: "us-east-1",        // if AWS_REGION / the profile set one
+//   accountId: "123456789012",  // if the source reported it
+//   source: "sso",              // "env" | "profile" | "assume-role" | "web-identity" | "process" | "sso" | "container" | "imds"
+// }
+
+await Bun.aws.credentials({ refresh: true }); // ignore the cache
+await new Bun.AWSClient({ profile: "prod" }).credentials(); // a specific profile
+```
+
+When nothing is found, the promise rejects with `code: "ERR_AWS_MISSING_CREDENTIALS"` and a message listing each source and why it was skipped. A configured source that failed rejects with `code: "ERR_AWS_CREDENTIALS"`.
+
+### `client.fetch(input, init?)`
+
+`fetch()`, with the request signed using [Signature Version 4](https://docs.aws.amazon.com/IAM/latest/UserGuide/reference_sigv.html). `init` accepts everything `fetch` does plus the signing options below; with none, the service and region are inferred from `*.amazonaws.com` / `*.on.aws` hostnames and ambient credentials are used.
+
+```ts
+const res = await Bun.aws.fetch("https://dynamodb.us-east-1.amazonaws.com/", {
+  method: "POST",
+  headers: {
+    "content-type": "application/x-amz-json-1.0",
+    "x-amz-target": "DynamoDB_20120810.GetItem",
+  },
+  body: JSON.stringify({ TableName: "users", Key: { id: { S: "42" } } }),
+});
+
+// A path-only URL goes to the service's standard endpoint in the resolved
+// region: https://sqs.<region>.amazonaws.com/?Action=ListQueues
+await Bun.aws.fetch("/?Action=ListQueues", { service: "sqs" });
+
+// API Gateway / Lambda function URL behind IAM auth on a custom domain
+await Bun.aws.fetch("https://api.example.com/orders", { service: "execute-api", region: "eu-west-1", profile: "prod" });
+```
+
+| Option                                           | Default                                                                                  |
+| ------------------------------------------------ | ---------------------------------------------------------------------------------------- |
+| `service`, `region`                              | inferred from the hostname; region falls back to `AWS_REGION`, then the profile's region |
+| `accessKeyId`, `secretAccessKey`, `sessionToken` | ambient credentials                                                                      |
+| `profile`                                        | `AWS_PROFILE` / `default`                                                                |
+| `signQuery`, `expiresIn`                         | `false`, `900` — put the signature in the query string                                   |
+| `unsignedPayload`                                | `false` — send `UNSIGNED-PAYLOAD` (S3-style services only)                               |
+
+Bun adds `Authorization`, `x-amz-date`, `x-amz-security-token` (temporary credentials) and, for S3, `x-amz-content-sha256`; setting those yourself is an error. `ReadableStream` bodies can only be signed for S3-style services (as `UNSIGNED-PAYLOAD`), since other services need the body's SHA-256 up front.
+
+A signature is only valid for the exact host and path it was computed for, so `redirect` defaults to `"manual"` — a `307` from S3 pointing at another region comes back as a `307` rather than being followed unsigned. Pass `redirect: "follow"` explicitly if you really want that.
+
+For `s3://` URLs keep using `fetch("s3://…", { s3: {...} })` or `Bun.s3`.
+
+### `client.presign(url, options?)`
+
+Returns a query-string-signed URL — typically an S3 object URL to hand to a browser. Takes the same signing options as `fetch`, plus `method` (default `"GET"`) and `expiresIn` (seconds, default `900`, max `604800`).
+
+```ts
+const download = await Bun.aws.presign("https://my-bucket.s3.eu-west-1.amazonaws.com/report.pdf", { expiresIn: 3600 });
+const upload = await Bun.aws.presign("https://my-bucket.s3.eu-west-1.amazonaws.com/upload.bin", { method: "PUT" });
+const queue = await Bun.aws.presign("/123456789012/jobs?Action=ReceiveMessage", { service: "sqs" });
+```
+
+It returns a promise because the credentials may still have to be fetched; the signing itself is local. For `s3://`-style paths and ACLs, [`S3File.presign()`](/runtime/s3#presigning-urls) is usually more convenient.
+
+## Google Cloud
+
+### Where tokens come from
+
+[Application Default Credentials](https://cloud.google.com/docs/authentication/application-default-credentials), in order:
+
+1. `GOOGLE_APPLICATION_CREDENTIALS` — a service-account key file, or an `authorized_user` file
+2. The file `gcloud auth application-default login` writes: `~/.config/gcloud/application_default_credentials.json` (`%APPDATA%\gcloud\…` on Windows, or under `CLOUDSDK_CONFIG`)
+3. The metadata server on Compute Engine, GKE, Cloud Run, Cloud Functions, App Engine, Cloud Build … (honours `GCE_METADATA_HOST` and `NO_GCE_CHECK`)
+
+Service-account keys are exchanged for tokens with a self-signed RS256 JWT; user credentials use their refresh token. `external_account` (workload identity federation) files are not supported yet.
+
+### `new Bun.GCPClient(options?)` / `Bun.gcp`
+
+`Bun.gcp` uses Application Default Credentials. A `GCPClient` can instead be given a `keyFile` path or the key's `credentials` (object or JSON string), plus default `scopes` or an `audience` (making `fetch()` send ID tokens by default).
+
+```ts
+const deployer = new Bun.GCPClient({ keyFile: "/secrets/deployer.json", scopes: ["cloud-platform"] });
+const invoker = new Bun.GCPClient({
+  credentials: JSON.parse(process.env.SA_KEY!),
+  audience: "https://my-service-abc123.a.run.app",
+});
+```
+
+### `client.accessToken()` / `client.idToken()`
+
+```ts
+const { token, expiration, source } = await Bun.gcp.accessToken();
+// source: "service-account" | "authorized-user" | "metadata"
+// also: email, projectId, quotaProjectId when known
+
+await Bun.gcp.accessToken({ scopes: ["bigquery", "https://www.googleapis.com/auth/pubsub"] });
+// bare scope names expand to https://www.googleapis.com/auth/<name>; the default is cloud-platform
+
+// OIDC identity token for calling Cloud Run / Cloud Functions / IAP
+const { token: idToken } = await Bun.gcp.idToken("https://my-service-abc123.a.run.app");
+```
+
+Tokens are cached per scope set / audience; pass `refresh: true` to force a new one. Failures reject with `code: "ERR_GCP_MISSING_CREDENTIALS"` (nothing configured) or `"ERR_GCP_CREDENTIALS"` (a configured source failed).
+
+### `client.fetch(input, init?)` (GCP)
+
+```ts
+await Bun.gcp.fetch("https://pubsub.googleapis.com/v1/projects/my-project/topics");
+await Bun.gcp.fetch("https://storage.googleapis.com/storage/v1/b/my-bucket/o", { scopes: "devstorage.read_only" });
+await Bun.gcp.fetch("https://my-service-abc123.a.run.app/", { audience: "https://my-service-abc123.a.run.app" });
+```
+
+`init` accepts everything `fetch` does plus `scopes` (access token, the default) or `audience` (ID token). Bun sets `Authorization: Bearer <token>`, and `x-goog-user-project` when the credentials carry a `quota_project_id` (or `GOOGLE_CLOUD_QUOTA_PROJECT` is set) unless you set it yourself.
diff --git a/docs/runtime/networking/fetch.mdx b/docs/runtime/networking/fetch.mdx
@@ -291,6 +291,17 @@ Only PUT and POST methods support request bodies when using S3. For uploads, Bun
 
 See the [S3](/runtime/s3) documentation.
 
+### AWS- and Google-authenticated requests
+
+`Bun.aws.fetch` and `Bun.gcp.fetch` are `fetch` with the request SigV4-signed for AWS, or carrying a Google Cloud bearer token, using the machine's ambient credentials:
+
+```ts
+await Bun.aws.fetch("https://sqs.us-east-1.amazonaws.com/?Action=ListQueues");
+await Bun.gcp.fetch("https://storage.googleapis.com/storage/v1/b?project=my-project");
+```
+
+See [AWS & Google Cloud auth](/runtime/networking/cloud-auth) for the options and where credentials come from.
+
-### AWS- and Google-authenticated requests
-
-`Bun.aws.fetch` and `Bun.gcp.fetch` are `fetch` with the request SigV4-signed for AWS, or carrying a Google Cloud bearer token, using the machine's ambient credentials:
-
-```ts
-await Bun.aws.fetch("https://sqs.us-east-1.amazonaws.com/?Action=ListQueues");
-await Bun.gcp.fetch("https://storage.googleapis.com/storage/v1/b?project=my-project");
-```
-
-See [AWS & Google Cloud auth](/runtime/networking/cloud-auth) for the options and where credentials come from.
+#### AWS- and Google-authenticated requests
+
+`Bun.aws.fetch` and `Bun.gcp.fetch` are `fetch` with the request SigV4-signed for AWS, or carrying a Google Cloud bearer token, using the machine's ambient credentials:
+
-### AWS- and Google-authenticated requests
-
-`Bun.aws.fetch` and `Bun.gcp.fetch` are `fetch` with the request SigV4-signed for AWS, or carrying a Google Cloud bearer token, using the machine's ambient credentials:
-
-```ts
-await Bun.aws.fetch("https://sqs.us-east-1.amazonaws.com/?Action=ListQueues");
-await Bun.gcp.fetch("https://storage.googleapis.com/storage/v1/b?project=my-project");
-```
-
-See [AWS & Google Cloud auth](/runtime/networking/cloud-auth) for the options and where credentials come from.
+#### AWS- and Google-authenticated requests
+
+`Bun.aws.fetch` and `Bun.gcp.fetch` are `fetch` with the request SigV4-signed for AWS, or carrying a Google Cloud bearer token, using the machine's ambient credentials:
+
 #### File URLs - `file://`
 
 You can fetch local files using the `file:` protocol:

diff --git a/docs/runtime/s3.mdx b/docs/runtime/s3.mdx
@@ -185,7 +185,7 @@ When your production service needs to let users upload files to your server, it'
 
 To let users upload directly to S3, presign URLs for S3 files. Presigning generates a URL with a signature that lets a user upload that specific file to S3, without exposing your credentials or granting them unnecessary access to your bucket.
 
-By default, Bun generates a `GET` URL that expires in 24 hours.
+By default, Bun generates a `GET` URL that expires in 24 hours. Presigning is synchronous and never touches the network. [Ambient credentials](#ambient-credentials-profiles-sso-iam-roles) from SSO, STS, a container endpoint or instance metadata need one network round-trip first: run any S3 operation or `await Bun.aws.credentials()` at startup. Until that has happened, `presign()` throws `ERR_S3_MISSING_CREDENTIALS`. Bun refreshes credentials that are in use in the background before they expire.
 
 ```ts s3.ts icon="/icons/typescript.svg"
 import { s3 } from "bun";
@@ -273,7 +273,7 @@ const url = s3file.presign({
 
 To redirect users to a presigned URL for an S3 file, pass an `S3File` instance to a `Response` object as the body.
 
-The response redirects the user to a presigned URL for the S3 file. The redirect saves you the memory, time, and bandwidth cost of downloading the file to your server and sending it back to the user.
+The response redirects the user to a presigned URL for the S3 file (so, like [`presign()`](#presigning-urls), it needs credentials that are already at hand). The redirect saves you the memory, time, and bandwidth cost of downloading the file to your server and sending it back to the user.
 
 ```ts s3.ts icon="/icons/typescript.svg"
 const response = new Response(s3file);
@@ -467,6 +467,24 @@ For each option, if the `S3_*` environment variable is not set, Bun falls back t
 
 Bun reads these environment variables from [`.env` files](/runtime/environment-variables) or from the process environment at initialization time (Bun does not use `process.env` for this).
 
+### Ambient credentials (profiles, SSO, IAM roles)
+
+When no access key is configured — neither in options nor in the environment — Bun resolves credentials the way the AWS CLI does: from `~/.aws/credentials` / `~/.aws/config` (static keys, `role_arn` + `source_profile`, `credential_process`, `aws sso login` sessions, `web_identity_token_file`), then `AWS_WEB_IDENTITY_TOKEN_FILE` (EKS), the container credentials endpoint (ECS, EKS Pod Identity), and finally EC2 instance metadata. So on AWS infrastructure with an IAM role attached, this just works:
+
+```ts
+import { s3 } from "bun";
+
+await s3.file("report.csv", { bucket: "my-bucket", region: "us-east-1" }).text();
+```
+
+Pick a profile with `AWS_PROFILE` or the `profile` option (which takes precedence over `AWS_*` key variables):
+
+```ts
+const prod = new S3Client({ profile: "prod", bucket: "my-bucket" });
+```
+
+Bun resolves them on first use without blocking the JavaScript thread on the network. It caches the result and refreshes it in the background a few minutes before it expires. See [AWS & Google Cloud auth](/runtime/networking/cloud-auth) for the full order, `Bun.aws.credentials()`, and signing arbitrary AWS requests with `Bun.aws.fetch`.
+
 Options you pass to `s3.file(credentials)`, `new Bun.S3Client(credentials)`, or any of the methods that accept credentials override these defaults. So if you use the same credentials for different buckets, you can set the credentials once in your `.env` file and pass only `bucket: "my-bucket"` to `s3.file()`.
 
 ### `S3Client` objects