diff --git a/.dagger/config.toml b/.dagger/config.toml
index b0d2cf9..c723024 100644
--- a/.dagger/config.toml
+++ b/.dagger/config.toml
@@ -8,3 +8,6 @@ source = ".."
 
 # Marker filename that skips generate when found at or above a TypeScript SDK module root.
 # settings.skipGenerateFilename = ""
+
+[modules.e2e]
+source = "modules/e2e"
diff --git a/.dagger/lock b/.dagger/lock
new file mode 100644
index 0000000..e69de29
diff --git a/.dagger/modules/e2e/.dagger/lock b/.dagger/modules/e2e/.dagger/lock
new file mode 100644
index 0000000..e69de29
diff --git a/.dagger/modules/e2e/.dagger/modules/e2e/.dagger/lock b/.dagger/modules/e2e/.dagger/modules/e2e/.dagger/lock
new file mode 100644
index 0000000..e69de29
diff --git a/.dagger/modules/e2e/fixtures/config/.dagger-typescript-sdk-skip-generate b/.dagger/modules/e2e/fixtures/config/.dagger-typescript-sdk-skip-generate
new file mode 100644
index 0000000..e69de29
diff --git a/.dagger/modules/e2e/fixtures/config/app/dagger.json b/.dagger/modules/e2e/fixtures/config/app/dagger.json
new file mode 100644
index 0000000..585e253
--- /dev/null
+++ b/.dagger/modules/e2e/fixtures/config/app/dagger.json
@@ -0,0 +1,7 @@
+{
+  "name": "config-app",
+  "engineVersion": "latest",
+  "sdk": {
+    "source": "typescript"
+  }
+}
diff --git a/.dagger/modules/e2e/fixtures/config/app/package.json b/.dagger/modules/e2e/fixtures/config/app/package.json
new file mode 100644
index 0000000..3dbc1ca
--- /dev/null
+++ b/.dagger/modules/e2e/fixtures/config/app/package.json
@@ -0,0 +1,3 @@
+{
+  "type": "module"
+}
diff --git a/.dagger/modules/e2e/fixtures/config/app/src/index.ts b/.dagger/modules/e2e/fixtures/config/app/src/index.ts
new file mode 100644
index 0000000..e81e0f0
--- /dev/null
+++ b/.dagger/modules/e2e/fixtures/config/app/src/index.ts
@@ -0,0 +1,9 @@
+import { object, func } from "@dagger.io/dagger"
+
+@object()
+export class ConfigApp {
+  @func()
+  hello(): string {
+    return "hello"
+  }
+}
diff --git a/.dagger/modules/e2e/fixtures/config/app/tsconfig.json b/.dagger/modules/e2e/fixtures/config/app/tsconfig.json
new file mode 100644
index 0000000..44cf48f
--- /dev/null
+++ b/.dagger/modules/e2e/fixtures/config/app/tsconfig.json
@@ -0,0 +1,10 @@
+{
+  "compilerOptions": {
+    "target": "ES2020",
+    "experimentalDecorators": true,
+    "paths": {
+      "@dagger.io/dagger": ["./sdk/index.ts"],
+      "@dagger.io/dagger/telemetry": ["./sdk/telemetry.ts"]
+    }
+  }
+}
diff --git a/.dagger/modules/e2e/fixtures/config/configured-deno/dagger.json b/.dagger/modules/e2e/fixtures/config/configured-deno/dagger.json
new file mode 100644
index 0000000..0f26507
--- /dev/null
+++ b/.dagger/modules/e2e/fixtures/config/configured-deno/dagger.json
@@ -0,0 +1,7 @@
+{
+  "name": "config-configured-deno",
+  "engineVersion": "latest",
+  "sdk": {
+    "source": "typescript"
+  }
+}
diff --git a/.dagger/modules/e2e/fixtures/config/configured-deno/deno.json b/.dagger/modules/e2e/fixtures/config/configured-deno/deno.json
new file mode 100644
index 0000000..bef74ca
--- /dev/null
+++ b/.dagger/modules/e2e/fixtures/config/configured-deno/deno.json
@@ -0,0 +1,13 @@
+{
+  "nodeModulesDir": "auto",
+  "compilerOptions": {
+    "experimentalDecorators": true
+  },
+  "imports": {
+    "@dagger.io/dagger": "./sdk/index.ts",
+    "@dagger.io/dagger/telemetry": "./sdk/telemetry.ts"
+  },
+  "dagger": {
+    "baseImage": "denoland/deno:alpine-2.0.0"
+  }
+}
diff --git a/.dagger/modules/e2e/fixtures/config/configured-deno/src/index.ts b/.dagger/modules/e2e/fixtures/config/configured-deno/src/index.ts
new file mode 100644
index 0000000..aae88e6
--- /dev/null
+++ b/.dagger/modules/e2e/fixtures/config/configured-deno/src/index.ts
@@ -0,0 +1,9 @@
+import { object, func } from "@dagger.io/dagger"
+
+@object()
+export class ConfigConfiguredDeno {
+  @func()
+  hello(): string {
+    return "hello"
+  }
+}
diff --git a/.dagger/modules/e2e/fixtures/config/configured/dagger.json b/.dagger/modules/e2e/fixtures/config/configured/dagger.json
new file mode 100644
index 0000000..e97ecb8
--- /dev/null
+++ b/.dagger/modules/e2e/fixtures/config/configured/dagger.json
@@ -0,0 +1,7 @@
+{
+  "name": "config-configured",
+  "engineVersion": "latest",
+  "sdk": {
+    "source": "typescript"
+  }
+}
diff --git a/.dagger/modules/e2e/fixtures/config/configured/package.json b/.dagger/modules/e2e/fixtures/config/configured/package.json
new file mode 100644
index 0000000..f009a5a
--- /dev/null
+++ b/.dagger/modules/e2e/fixtures/config/configured/package.json
@@ -0,0 +1,7 @@
+{
+  "type": "module",
+  "packageManager": "pnpm@8.15.4",
+  "dagger": {
+    "baseImage": "node:23.2.0-alpine"
+  }
+}
diff --git a/.dagger/modules/e2e/fixtures/config/configured/src/index.ts b/.dagger/modules/e2e/fixtures/config/configured/src/index.ts
new file mode 100644
index 0000000..b992f8d
--- /dev/null
+++ b/.dagger/modules/e2e/fixtures/config/configured/src/index.ts
@@ -0,0 +1,9 @@
+import { object, func } from "@dagger.io/dagger"
+
+@object()
+export class ConfigConfigured {
+  @func()
+  hello(): string {
+    return "hello"
+  }
+}
diff --git a/.dagger/modules/e2e/fixtures/config/configured/tsconfig.json b/.dagger/modules/e2e/fixtures/config/configured/tsconfig.json
new file mode 100644
index 0000000..44cf48f
--- /dev/null
+++ b/.dagger/modules/e2e/fixtures/config/configured/tsconfig.json
@@ -0,0 +1,10 @@
+{
+  "compilerOptions": {
+    "target": "ES2020",
+    "experimentalDecorators": true,
+    "paths": {
+      "@dagger.io/dagger": ["./sdk/index.ts"],
+      "@dagger.io/dagger/telemetry": ["./sdk/telemetry.ts"]
+    }
+  }
+}
diff --git a/.dagger/modules/e2e/fixtures/generate/app/.gitattributes b/.dagger/modules/e2e/fixtures/generate/app/.gitattributes
new file mode 100644
index 0000000..8274184
--- /dev/null
+++ b/.dagger/modules/e2e/fixtures/generate/app/.gitattributes
@@ -0,0 +1 @@
+/sdk/** linguist-generated
diff --git a/.dagger/modules/e2e/fixtures/generate/app/.gitignore b/.dagger/modules/e2e/fixtures/generate/app/.gitignore
new file mode 100644
index 0000000..040187c
--- /dev/null
+++ b/.dagger/modules/e2e/fixtures/generate/app/.gitignore
@@ -0,0 +1,4 @@
+/sdk
+/**/node_modules/**
+/**/.pnpm-store/**
+/.env
diff --git a/.dagger/modules/e2e/fixtures/generate/app/package.json b/.dagger/modules/e2e/fixtures/generate/app/package.json
new file mode 100644
index 0000000..fe4de26
--- /dev/null
+++ b/.dagger/modules/e2e/fixtures/generate/app/package.json
@@ -0,0 +1,3 @@
+{
+  "type": "module"
+,"dependencies":{"typescript":"5.9.3"}}
\ No newline at end of file
diff --git a/.dagger/modules/e2e/fixtures/generate/app/src/index.ts b/.dagger/modules/e2e/fixtures/generate/app/src/index.ts
new file mode 100644
index 0000000..dc8ca25
--- /dev/null
+++ b/.dagger/modules/e2e/fixtures/generate/app/src/index.ts
@@ -0,0 +1,41 @@
+/**
+ * A generated module for GenerateApp functions
+ *
+ * This module has been generated via dagger module init and serves as a reference to
+ * basic module structure as you get started with Dagger.
+ *
+ * Two functions have been pre-created. You can modify, delete, or add to them,
+ * as needed. They demonstrate usage of arguments and return types using simple
+ * echo and grep commands. The functions can be called from the dagger CLI or
+ * from one of the SDKs.
+ *
+ * The first line in this comment block is a short description line and the
+ * rest is a long description with more detail on the module's purpose or usage,
+ * if appropriate. All modules should have a short description.
+ */
+import { dag, Container, Directory, object, func } from "@dagger.io/dagger"
+
+@object()
+export class GenerateApp {
+  /**
+   * Returns a container that echoes whatever string argument is provided
+   */
+  @func()
+  containerEcho(stringArg: string): Container {
+    return dag.container().from("alpine:latest").withExec(["echo", stringArg])
+  }
+
+  /**
+   * Returns lines that match a pattern in the files of the provided Directory
+   */
+  @func()
+  async grepDir(directoryArg: Directory, pattern: string): Promise<string> {
+    return dag
+      .container()
+      .from("alpine:latest")
+      .withMountedDirectory("/mnt", directoryArg)
+      .withWorkdir("/mnt")
+      .withExec(["grep", "-R", pattern, "."])
+      .stdout()
+  }
+}
diff --git a/.dagger/modules/e2e/fixtures/generate/app/tsconfig.json b/.dagger/modules/e2e/fixtures/generate/app/tsconfig.json
new file mode 100644
index 0000000..4ec0c2d
--- /dev/null
+++ b/.dagger/modules/e2e/fixtures/generate/app/tsconfig.json
@@ -0,0 +1,13 @@
+{
+  "compilerOptions": {
+    "target": "ES2022",
+    "moduleResolution": "Node",
+    "experimentalDecorators": true,
+    "strict": true,
+    "skipLibCheck": true,
+    "paths": {
+      "@dagger.io/dagger": ["./sdk/index.ts"],
+      "@dagger.io/dagger/telemetry": ["./sdk/telemetry.ts"]
+    }
+  }
+}
diff --git a/.dagger/modules/e2e/fixtures/generate/app/yarn.lock b/.dagger/modules/e2e/fixtures/generate/app/yarn.lock
new file mode 100644
index 0000000..07e8392
--- /dev/null
+++ b/.dagger/modules/e2e/fixtures/generate/app/yarn.lock
@@ -0,0 +1,8 @@
+# THIS IS AN AUTOGENERATED FILE. DO NOT EDIT THIS FILE DIRECTLY.
+# yarn lockfile v1
+
+
+typescript@5.9.3:
+  version "5.9.3"
+  resolved "https://registry.yarnpkg.com/typescript/-/typescript-5.9.3.tgz#5b4f59e15310ab17a216f5d6cf53ee476ede670f"
+  integrity sha512-jl1vZzPDinLr9eUt3J/t7V6FgNEw9QjvBPdysz9KfQDD41fQrC2Y4vKQdiaUpFT4bXlb1RHhLpp8wtm6M5TgSw==
diff --git a/.dagger/modules/e2e/main.dang b/.dagger/modules/e2e/main.dang
index 103676a..4b4b3ea 100644
--- a/.dagger/modules/e2e/main.dang
+++ b/.dagger/modules/e2e/main.dang
@@ -14,6 +14,9 @@ type E2e {
   let existingNodePath: String! = fixtureRoot + "/init-existing/node-app"
   let existingDenoPath: String! = fixtureRoot + "/init-existing/deno-app"
   let existingBunPath: String! = fixtureRoot + "/init-existing/bun-app"
+  let configModulePath: String! = fixtureRoot + "/config/app"
+  let configuredModulePath: String! = fixtureRoot + "/config/configured"
+  let configuredDenoModulePath: String! = fixtureRoot + "/config/configured-deno"
 
   """
   Fail the current check when a condition is false.
@@ -65,6 +68,16 @@ type E2e {
     assert(changes.removedPaths.length == 0, "dependency edit should not remove generated files")
   }
 
+  """
+  Assert that a config edit modified only the named file (no adds, no removes).
+  """
+  let assertOnlyFileChanged(changes: Changeset!, path: String!, message: String!): Void {
+    assert(contains(changes.modifiedPaths, path), message + ": did not modify " + path)
+    assert(changes.modifiedPaths.length == 1, message + ": modified more than one file")
+    assert(changes.addedPaths.length == 0, message + ": should not add files")
+    assert(changes.removedPaths.length == 0, message + ": should not remove files")
+  }
+
   """
   The helper should expose the generate skip marker used by callers.
   """
@@ -185,7 +198,7 @@ type E2e {
   pub generateCheck(ws: Workspace!): Void @check {
     let changes = typescriptSdk.mod(ws, path: generateModulePath).generate(ws)
 
-    assertAdded(changes, generateModulePath + "/src/index.ts")
+    assertAdded(changes, generateModulePath + "/sdk/index.ts")
 
     null
   }
@@ -196,7 +209,7 @@ type E2e {
   pub generateAllCheck(ws: Workspace!): Void @check {
     let changes = typescriptSdk.generateAll(ws)
 
-    assertAdded(changes, generateModulePath + "/src/index.ts")
+    assertAdded(changes, generateModulePath + "/sdk/index.ts")
     assert(contains(changes.addedPaths, lookupModulePath + "/src/index.ts") == false, "generateAll generated a lookup fixture that should be skipped")
     assert(contains(changes.addedPaths, depsModulePath + "/src/index.ts") == false, "generateAll generated dependency fixtures that should be skipped")
     assert(contains(changes.addedPaths, skipModulePath + "/src/index.ts") == false, "generateAll generated a skipped module")
@@ -288,6 +301,100 @@ type E2e {
     null
   }
 
+  """
+  Config readers should reflect package.json (or deno.json), and mutators
+  should edit only the targeted config file while preserving unrelated keys.
+  """
+  pub configCheck(ws: Workspace!): Void @check {
+    let app = typescriptSdk.mod(ws, path: configModulePath).config
+    let configured = typescriptSdk.mod(ws, path: configuredModulePath).config
+    let configuredDeno = typescriptSdk.mod(ws, path: configuredDenoModulePath).config
+
+    # Defaults: unconfigured node module reads empty.
+    assert(app.packageManager == "", "default packageManager should be empty")
+    assert(app.baseImage == "", "default baseImage should be empty")
+
+    # Configured node module reads the override values.
+    assert(configured.packageManager == "pnpm@8.15.4", "configured packageManager should read pnpm@8.15.4")
+    assert(configured.baseImage == "node:23.2.0-alpine", "configured baseImage should read the override")
+
+    # Deno module: no package.json, baseImage comes from deno.json.
+    assert(configuredDeno.packageManager == "", "deno-only module should expose no packageManager")
+    assert(configuredDeno.baseImage == "denoland/deno:alpine-2.0.0", "deno baseImage should read from deno.json")
+
+    let appPkg = configModulePath + "/package.json"
+
+    let pm = app.setPackageManager("yarn@1.22.22")
+    assertOnlyFileChanged(pm, appPkg, "setPackageManager")
+    assertContains(pm.after.file(appPkg).contents, "yarn@1.22.22", "setPackageManager did not write the new value")
+    assertContains(pm.after.file(appPkg).contents, "\"type\": \"module\"", "setPackageManager dropped unrelated keys")
+
+    let img = app.setBaseImage("node:23.2.0-alpine")
+    assertOnlyFileChanged(img, appPkg, "setBaseImage")
+    assertContains(img.after.file(appPkg).contents, "node:23.2.0-alpine", "setBaseImage did not write the image")
+
+    let configuredPkg = configuredModulePath + "/package.json"
+
+    let unsetPm = configured.unsetPackageManager
+    assertOnlyFileChanged(unsetPm, configuredPkg, "unsetPackageManager")
+    assertNotContains(unsetPm.after.file(configuredPkg).contents, "packageManager", "unsetPackageManager left the field")
+    assertContains(unsetPm.after.file(configuredPkg).contents, "node:23.2.0-alpine", "unsetPackageManager clobbered dagger.baseImage")
+
+    let unsetImg = configured.unsetBaseImage
+    assertOnlyFileChanged(unsetImg, configuredPkg, "unsetBaseImage")
+    assertNotContains(unsetImg.after.file(configuredPkg).contents, "baseImage", "unsetBaseImage left the override")
+    assertContains(unsetImg.after.file(configuredPkg).contents, "pnpm@8.15.4", "unsetBaseImage clobbered packageManager")
+
+    # Deno modules: baseImage edits route to deno.json, not package.json.
+    let configuredDenoFile = configuredDenoModulePath + "/deno.json"
+
+    let denoImg = configuredDeno.setBaseImage("denoland/deno:latest")
+    assertOnlyFileChanged(denoImg, configuredDenoFile, "setBaseImage on deno module")
+    assertContains(denoImg.after.file(configuredDenoFile).contents, "denoland/deno:latest", "setBaseImage did not write to deno.json")
+
+    let unsetDenoImg = configuredDeno.unsetBaseImage
+    assertOnlyFileChanged(unsetDenoImg, configuredDenoFile, "unsetBaseImage on deno module")
+    assertNotContains(unsetDenoImg.after.file(configuredDenoFile).contents, "baseImage", "unsetBaseImage left the override in deno.json")
+    assertContains(unsetDenoImg.after.file(configuredDenoFile).contents, "nodeModulesDir", "unsetBaseImage clobbered unrelated deno keys")
+
+    null
+  }
+
+  """
+  Init flags should write configuration into the generated config files. By
+  default, no config keys are written; the runtime decides which file the
+  base image override lands in.
+  """
+  pub initConfigCheck(ws: Workspace!): Void @check {
+    let configuredPath = outputRoot + "/init-configured"
+    let configuredDenoPath = outputRoot + "/init-configured-deno"
+    let defaultPath = outputRoot + "/init-config-default"
+
+    let configured = typescriptSdk.init(ws, name: "init-configured", path: configuredPath, packageManager: "pnpm@8.15.4", baseImage: "node:23.2.0-alpine")
+    let pkg = configuredPath + "/package.json"
+    assertAdded(configured, pkg)
+    assert(configured.modifiedPaths.length == 0, "configured init should not modify existing files")
+    assert(configured.removedPaths.length == 0, "configured init should not remove files")
+    assertContains(configured.layer.file(pkg).contents, "pnpm@8.15.4", "init --package-manager not written")
+    assertContains(configured.layer.file(pkg).contents, "node:23.2.0-alpine", "init --base-image not written")
+
+    # Deno init with baseImage routes to deno.json; no package.json is created.
+    let configuredDeno = typescriptSdk.init(ws, name: "init-configured-deno", path: configuredDenoPath, runtime: TypescriptSdkRuntime.DENO, baseImage: "denoland/deno:alpine-2.0.0")
+    let denoFile = configuredDenoPath + "/deno.json"
+    assertAdded(configuredDeno, denoFile)
+    assertContains(configuredDeno.layer.file(denoFile).contents, "denoland/deno:alpine-2.0.0", "init deno --base-image not written")
+    assert(contains(configuredDeno.addedPaths, configuredDenoPath + "/package.json") == false, "deno init should not generate package.json even with baseImage")
+
+    # Default init has no config keys.
+    let default = typescriptSdk.init(ws, name: "init-config-default", path: defaultPath)
+    let defaultPkg = defaultPath + "/package.json"
+    assertAdded(default, defaultPkg)
+    assertNotContains(default.layer.file(defaultPkg).contents, "packageManager", "default init should not write packageManager")
+    assertNotContains(default.layer.file(defaultPkg).contents, "baseImage", "default init should not write baseImage")
+
+    null
+  }
+
   """
   Listing modules in a workspace should return every module whose
   dagger.json declares the TypeScript SDK, and nothing else.
diff --git a/README.md b/README.md
index afe9f98..cfdb633 100644
--- a/README.md
+++ b/README.md
@@ -55,6 +55,44 @@ settings are preserved.
 `init` only seeds template and config files. Run `mod ... generate` to
 produce the generated SDK.
 
+### Configure a module at creation
+
+`init` accepts configuration flags written into the module's `package.json`
+(or `deno.json` for Deno modules):
+
+```sh
+dagger call typescript-sdk init --name my-module \
+    --package-manager pnpm@8.15.4 \
+    --base-image node:23.2.0-alpine
+```
+
+Both flags are optional. By default no `packageManager` field is written and
+no base image override is set. `--package-manager` is not valid with
+`--runtime DENO`.
+
+## Configure an existing module
+
+Read current configuration:
+
+```sh
+dagger call typescript-sdk mod --path my-module config package-manager
+dagger call typescript-sdk mod --path my-module config base-image
+```
+
+Change configuration (each prints a diff to confirm before writing):
+
+```sh
+dagger call typescript-sdk mod --path my-module \
+    config set-package-manager --value pnpm@8.15.4
+dagger call typescript-sdk mod --path my-module \
+    config set-base-image --image node:23.2.0-alpine
+dagger call typescript-sdk mod --path my-module config unset-package-manager
+dagger call typescript-sdk mod --path my-module config unset-base-image
+```
+
+`base-image` writes to `deno.json` for Deno modules and to `package.json`
+otherwise — matching where the engine reads it from.
+
 ## Generate SDK files
 
 For a single module:
diff --git a/dagger.json b/dagger.json
index 1c8156e..3c91b01 100644
--- a/dagger.json
+++ b/dagger.json
@@ -8,7 +8,7 @@
     {
       "name": "polyfill",
       "source": "github.com/dagger/sdk-sdk/polyfill@main",
-      "pin": "d6ab6406586e6b3853b8936b2b3a96bba2554071"
+      "pin": "09da9576688ec4b495ae4a9443a4719da86ed25e"
     }
   ],
   "source": "."
diff --git a/helpers/module-config/config.go b/helpers/module-config/config.go
new file mode 100644
index 0000000..c534c18
--- /dev/null
+++ b/helpers/module-config/config.go
@@ -0,0 +1,49 @@
+package main
+
+import (
+	"github.com/tidwall/gjson"
+	"github.com/tidwall/sjson"
+)
+
+// getPackageManager reads the top-level "packageManager" field from a
+// package.json. Returns "" when the key is absent.
+func getPackageManager(input string) string {
+	return gjson.Get(input, "packageManager").String()
+}
+
+// setPackageManager writes the top-level "packageManager" field.
+func setPackageManager(input, value string) (string, error) {
+	return sjson.Set(input, "packageManager", value)
+}
+
+// unsetPackageManager removes the top-level "packageManager" field.
+func unsetPackageManager(input string) (string, error) {
+	return sjson.Delete(input, "packageManager")
+}
+
+// getBaseImage reads "dagger.baseImage" from either a package.json or a
+// deno.json (the engine accepts the same key in both). Returns "" when absent.
+func getBaseImage(input string) string {
+	return gjson.Get(input, "dagger.baseImage").String()
+}
+
+// setBaseImage writes "dagger.baseImage", creating the nested "dagger" object
+// when necessary.
+func setBaseImage(input, value string) (string, error) {
+	return sjson.Set(input, "dagger.baseImage", value)
+}
+
+// unsetBaseImage removes "dagger.baseImage" and prunes the "dagger" object
+// when it would otherwise be left empty, so the file does not carry an empty
+// table after the round-trip.
+func unsetBaseImage(input string) (string, error) {
+	out, err := sjson.Delete(input, "dagger.baseImage")
+	if err != nil {
+		return "", err
+	}
+	dagger := gjson.Get(out, "dagger")
+	if dagger.IsObject() && len(dagger.Map()) == 0 {
+		return sjson.Delete(out, "dagger")
+	}
+	return out, nil
+}
diff --git a/helpers/module-config/config_test.go b/helpers/module-config/config_test.go
new file mode 100644
index 0000000..f3e775a
--- /dev/null
+++ b/helpers/module-config/config_test.go
@@ -0,0 +1,97 @@
+package main
+
+import (
+	"strings"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+const samplePackageJSON = `{
+  "type": "module",
+  "name": "demo",
+  "dependencies": {
+    "typescript": "5.9.3"
+  }
+}`
+
+const configuredPackageJSON = `{
+  "type": "module",
+  "packageManager": "pnpm@8.15.4",
+  "dagger": {
+    "baseImage": "node:23.2.0-alpine"
+  }
+}`
+
+const sampleDenoJSON = `{
+  "imports": {
+    "@user/lib": "./lib.ts"
+  }
+}`
+
+func TestGetPackageManager(t *testing.T) {
+	require.Equal(t, "", getPackageManager(samplePackageJSON))
+	require.Equal(t, "pnpm@8.15.4", getPackageManager(configuredPackageJSON))
+	require.Equal(t, "", getPackageManager(""))
+}
+
+func TestGetBaseImage(t *testing.T) {
+	require.Equal(t, "", getBaseImage(samplePackageJSON))
+	require.Equal(t, "node:23.2.0-alpine", getBaseImage(configuredPackageJSON))
+	require.Equal(t, "", getBaseImage(sampleDenoJSON))
+}
+
+func TestSetPackageManagerPreservesData(t *testing.T) {
+	out, err := setPackageManager(samplePackageJSON, "yarn@1.22.22")
+	require.NoError(t, err)
+	require.Contains(t, out, `"packageManager":"yarn@1.22.22"`)
+	require.Contains(t, out, `"typescript": "5.9.3"`, "unrelated keys were dropped")
+}
+
+func TestUnsetPackageManager(t *testing.T) {
+	out, err := unsetPackageManager(configuredPackageJSON)
+	require.NoError(t, err)
+	require.NotContains(t, out, "packageManager")
+	require.Contains(t, out, `"baseImage"`, "unrelated dagger config should be preserved")
+}
+
+func TestSetBaseImageOnEmpty(t *testing.T) {
+	out, err := setBaseImage("{}", "node:23.2.0-alpine")
+	require.NoError(t, err)
+	require.Equal(t, "node:23.2.0-alpine", getBaseImage(out))
+}
+
+func TestSetBaseImagePreservesSiblings(t *testing.T) {
+	out, err := setBaseImage(samplePackageJSON, "node:23.2.0-alpine")
+	require.NoError(t, err)
+	require.Equal(t, "node:23.2.0-alpine", getBaseImage(out))
+	require.Contains(t, out, `"typescript": "5.9.3"`, "unrelated keys were dropped")
+}
+
+func TestUnsetBaseImagePrunesEmptyDagger(t *testing.T) {
+	in := `{"dagger":{"baseImage":"foo"}}`
+	out, err := unsetBaseImage(in)
+	require.NoError(t, err)
+	require.NotContains(t, out, "dagger", "empty dagger object should be pruned")
+}
+
+func TestUnsetBaseImageKeepsSiblings(t *testing.T) {
+	in := `{"dagger":{"baseImage":"foo","runtime":"node@20.15.0"}}`
+	out, err := unsetBaseImage(in)
+	require.NoError(t, err)
+	require.NotContains(t, out, "baseImage")
+	require.Contains(t, out, "runtime", "sibling dagger keys should survive an unset")
+}
+
+func TestUnsetBaseImageOnEmptyDoc(t *testing.T) {
+	out, err := unsetBaseImage("{}")
+	require.NoError(t, err)
+	require.Equal(t, "", strings.TrimSpace(strings.Trim(out, "{}")))
+}
+
+func TestSetBaseImageOnDenoJSON(t *testing.T) {
+	out, err := setBaseImage(sampleDenoJSON, "denoland/deno:alpine")
+	require.NoError(t, err)
+	require.Equal(t, "denoland/deno:alpine", getBaseImage(out))
+	require.Contains(t, out, "@user/lib", "unrelated deno keys should be preserved")
+}
diff --git a/helpers/module-config/go.mod b/helpers/module-config/go.mod
new file mode 100644
index 0000000..741ee81
--- /dev/null
+++ b/helpers/module-config/go.mod
@@ -0,0 +1,17 @@
+module module-config
+
+go 1.25.1
+
+require (
+	github.com/stretchr/testify v1.11.1
+	github.com/tidwall/gjson v1.19.0
+	github.com/tidwall/sjson v1.2.5
+)
+
+require (
+	github.com/davecgh/go-spew v1.1.1 // indirect
+	github.com/pmezard/go-difflib v1.0.0 // indirect
+	github.com/tidwall/match v1.1.1 // indirect
+	github.com/tidwall/pretty v1.2.0 // indirect
+	gopkg.in/yaml.v3 v3.0.1 // indirect
+)
diff --git a/helpers/module-config/go.sum b/helpers/module-config/go.sum
new file mode 100644
index 0000000..7fe7087
--- /dev/null
+++ b/helpers/module-config/go.sum
@@ -0,0 +1,19 @@
+github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
+github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
+github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
+github.com/stretchr/testify v1.11.1 h1:7s2iGBzp5EwR7/aIZr8ao5+dra3wiQyKjjFuvgVKu7U=
+github.com/stretchr/testify v1.11.1/go.mod h1:wZwfW3scLgRK+23gO65QZefKpKQRnfz6sD981Nm4B6U=
+github.com/tidwall/gjson v1.14.2/go.mod h1:/wbyibRr2FHMks5tjHJ5F8dMZh3AcwJEMf5vlfC0lxk=
+github.com/tidwall/gjson v1.19.0 h1:xwxm7n691Uf3u5OFjzngavjGTh55KX5q/9w9xHW88JU=
+github.com/tidwall/gjson v1.19.0/go.mod h1:V37/opeE/JbLUOfH0QTXiNez2l0RUjYUhpT4szFQAfc=
+github.com/tidwall/match v1.1.1 h1:+Ho715JplO36QYgwN9PGYNhgZvoUSc9X2c80KVTi+GA=
+github.com/tidwall/match v1.1.1/go.mod h1:eRSPERbgtNPcGhD8UCthc6PmLEQXEWd3PRB5JTxsfmM=
+github.com/tidwall/pretty v1.2.0 h1:RWIZEg2iJ8/g6fDDYzMpobmaoGh5OLl4AXtGUGPcqCs=
+github.com/tidwall/pretty v1.2.0/go.mod h1:ITEVvHYasfjBbM0u2Pg8T2nJnzm8xPwvNhhsoaGGjNU=
+github.com/tidwall/sjson v1.2.5 h1:kLy8mja+1c9jlljvWTlSazM7cKDRfJuR/bOJhcY5NcY=
+github.com/tidwall/sjson v1.2.5/go.mod h1:Fvgq9kS/6ociJEDnK0Fk1cpYF4FIW6ZF7LAe+6jwd28=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405 h1:yhCVgyC4o1eVCa2tZl7eS0r+SDo693bJlVdllGtEeKM=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
+gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
+gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
diff --git a/helpers/module-config/main.go b/helpers/module-config/main.go
new file mode 100644
index 0000000..480f00a
--- /dev/null
+++ b/helpers/module-config/main.go
@@ -0,0 +1,99 @@
+// module-config edits Dagger module configuration written into a JSON config
+// file (package.json or deno.json). get-* commands print the current value;
+// set-*/unset-* commands edit the file in place, preserving unrelated keys.
+package main
+
+import (
+	"bytes"
+	"errors"
+	"fmt"
+	"io/fs"
+	"os"
+)
+
+func main() {
+	if err := run(os.Args[1:]); err != nil {
+		fmt.Fprintln(os.Stderr, err)
+		os.Exit(1)
+	}
+}
+
+// run dispatches a subcommand. get-* commands print to stdout (no trailing
+// newline). set-*/unset-* commands rewrite the file in place.
+//
+// usage: module-config <command> <file> [value]
+func run(args []string) error {
+	if len(args) < 2 {
+		return fmt.Errorf("usage: module-config <command> <file> [value]")
+	}
+	cmd, path := args[0], args[1]
+
+	input, err := readOrEmpty(path)
+	if err != nil {
+		return err
+	}
+
+	switch cmd {
+	case "get-package-manager":
+		fmt.Print(getPackageManager(input))
+		return nil
+	case "get-base-image":
+		fmt.Print(getBaseImage(input))
+		return nil
+	case "set-package-manager":
+		v, err := value(args)
+		if err != nil {
+			return err
+		}
+		out, err := setPackageManager(input, v)
+		if err != nil {
+			return err
+		}
+		return os.WriteFile(path, []byte(out), 0o644)
+	case "set-base-image":
+		v, err := value(args)
+		if err != nil {
+			return err
+		}
+		out, err := setBaseImage(input, v)
+		if err != nil {
+			return err
+		}
+		return os.WriteFile(path, []byte(out), 0o644)
+	case "unset-package-manager":
+		out, err := unsetPackageManager(input)
+		if err != nil {
+			return err
+		}
+		return os.WriteFile(path, []byte(out), 0o644)
+	case "unset-base-image":
+		out, err := unsetBaseImage(input)
+		if err != nil {
+			return err
+		}
+		return os.WriteFile(path, []byte(out), 0o644)
+	default:
+		return fmt.Errorf("unknown command: %s", cmd)
+	}
+}
+
+func value(args []string) (string, error) {
+	if len(args) < 3 {
+		return "", fmt.Errorf("%s requires a value", args[0])
+	}
+	return args[2], nil
+}
+
+func readOrEmpty(path string) (string, error) {
+	contents, err := os.ReadFile(path)
+	switch {
+	case errors.Is(err, fs.ErrNotExist):
+		return "{}", nil
+	case err != nil:
+		return "", fmt.Errorf("read %s: %w", path, err)
+	}
+	if len(bytes.TrimSpace(contents)) == 0 {
+		return "{}", nil
+	}
+	return string(contents), nil
+}
diff --git a/helpers/module-config/main_test.go b/helpers/module-config/main_test.go
new file mode 100644
index 0000000..b3da613
--- /dev/null
+++ b/helpers/module-config/main_test.go
@@ -0,0 +1,60 @@
+package main
+
+import (
+	"os"
+	"path/filepath"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func writeTemp(t *testing.T, contents string) string {
+	t.Helper()
+	dir := t.TempDir()
+	p := filepath.Join(dir, "package.json")
+	require.NoError(t, os.WriteFile(p, []byte(contents), 0o644))
+	return p
+}
+
+func TestRunSetThenGet(t *testing.T) {
+	p := writeTemp(t, samplePackageJSON)
+
+	require.NoError(t, run([]string{"set-base-image", p, "node:23.2.0-alpine"}))
+
+	data, err := os.ReadFile(p)
+	require.NoError(t, err)
+	require.Contains(t, string(data), "node:23.2.0-alpine")
+}
+
+func TestRunGetDoesNotWrite(t *testing.T) {
+	p := writeTemp(t, configuredPackageJSON)
+	before, err := os.ReadFile(p)
+	require.NoError(t, err)
+
+	require.NoError(t, run([]string{"get-package-manager", p}))
+
+	after, err := os.ReadFile(p)
+	require.NoError(t, err)
+	require.Equal(t, before, after, "get-* must not modify the file")
+}
+
+func TestRunUnknownCommand(t *testing.T) {
+	p := writeTemp(t, samplePackageJSON)
+	require.Error(t, run([]string{"bogus", p}))
+}
+
+func TestRunRequiresValue(t *testing.T) {
+	p := writeTemp(t, samplePackageJSON)
+	require.Error(t, run([]string{"set-base-image", p}))
+}
+
+func TestRunOnMissingFileTreatsAsEmpty(t *testing.T) {
+	dir := t.TempDir()
+	p := filepath.Join(dir, "package.json")
+
+	require.NoError(t, run([]string{"set-base-image", p, "node:23.2.0-alpine"}))
+
+	data, err := os.ReadFile(p)
+	require.NoError(t, err)
+	require.Equal(t, "node:23.2.0-alpine", getBaseImage(string(data)))
+}
diff --git a/mod-config.dang b/mod-config.dang
new file mode 100644
index 0000000..8deaeef
--- /dev/null
+++ b/mod-config.dang
@@ -0,0 +1,124 @@
+"""
+TypeScript SDK build configuration stored in a module's package.json
+or deno.json.
+"""
+type ModConfig {
+  """
+  Workspace-relative path of the module root.
+  """
+  let path: String!
+
+  """
+  The workspace this module belongs to.
+  """
+  let ws: Workspace!
+
+  """
+  The Node-standard packageManager field (e.g. "pnpm@8.15.4"), read from
+  package.json. Empty when unset, or when the module has no package.json.
+  """
+  pub packageManager: String! {
+    if (hasFile(packageJsonPath)) {
+      tool(packageJsonPath).withExec(["module-config", "get-package-manager", toolPath]).stdout
+    } else {
+      ""
+    }
+  }
+
+  """
+  The base container image override, read from dagger.baseImage. For Deno
+  modules (deno.json present) the value comes from deno.json; otherwise from
+  package.json. Empty when no override is set.
+  """
+  pub baseImage: String! {
+    let file = baseImageFile
+    if (hasFile(file)) {
+      tool(file).withExec(["module-config", "get-base-image", toolPath]).stdout
+    } else {
+      ""
+    }
+  }
+
+  """
+  Set the Node-standard packageManager field in package.json.
+  """
+  pub setPackageManager(value: String!): Changeset! {
+    edit(packageJsonPath, ["module-config", "set-package-manager", toolPath, value])
+  }
+
+  """
+  Remove the packageManager field from package.json.
+  """
+  pub unsetPackageManager: Changeset! {
+    edit(packageJsonPath, ["module-config", "unset-package-manager", toolPath])
+  }
+
+  """
+  Override the base container image. Writes to deno.json for Deno modules,
+  otherwise to package.json.
+  """
+  pub setBaseImage(image: String!): Changeset! {
+    edit(baseImageFile, ["module-config", "set-base-image", toolPath, image])
+  }
+
+  """
+  Remove the base image override and fall back to the SDK default. Edits
+  whichever file currently holds dagger.baseImage.
+  """
+  pub unsetBaseImage: Changeset! {
+    edit(baseImageFile, ["module-config", "unset-base-image", toolPath])
+  }
+
+  let packageJsonPath: String! {
+    if (path == ".") { "package.json" } else { path + "/package.json" }
+  }
+
+  let denoJsonPath: String! {
+    if (path == ".") { "deno.json" } else { path + "/deno.json" }
+  }
+
+  """
+  The config file that owns dagger.baseImage for this module: deno.json
+  when present at the module root, otherwise package.json. The engine reads
+  either, but per-module we keep one source of truth.
+  """
+  let baseImageFile: String! {
+    if (hasFile(denoJsonPath)) { denoJsonPath } else { packageJsonPath }
+  }
+
+  let toolPath: String! = "/work/config.json"
+
+  let hasFile(file: String!): Boolean! {
+    ws.directory("/", include: [file]).exists(file)
+  }
+
+  """
+  Container with the module-config helper built and the requested config file
+  mounted at toolPath. Missing files are seeded as "{}" so set-* commands
+  can materialize a new file (e.g. set-package-manager on a deno-only
+  module).
+  """
+  let tool(file: String!): Container! {
+    let base = container
+      .from("golang:1.25-alpine")
+      .withoutEntrypoint
+      .withMountedCache("/go/pkg/mod", cacheVolume("go-mod"))
+      .withMountedCache("/root/.cache/go-build", cacheVolume("go-build"))
+      .withDirectory("/helper", currentModule.source.directory("helpers/module-config"))
+      .withWorkdir("/helper")
+      .withExec(["go", "build", "-o", "/usr/local/bin/module-config", "."])
+    if (hasFile(file)) {
+      base.withFile(toolPath, ws.directory("/", include: [file]).file(file))
+    } else {
+      base.withNewFile(toolPath, "{}")
+    }
+  }
+
+  """
+  Run an edit command on a config file and return the resulting change.
+  """
+  let edit(file: String!, args: [String!]!): Changeset! {
+    let edited = tool(file).withExec(args).file(toolPath).contents
+    polyfill.workspace(ws).fork.withNewFile(file, edited).changes
+  }
+}
diff --git a/mod.dang b/mod.dang
index 131c46b..8485212 100644
--- a/mod.dang
+++ b/mod.dang
@@ -44,6 +44,17 @@ type Mod {
     )
   }
 
+  """
+  Manage this module's TypeScript SDK build configuration (package.json,
+  deno.json).
+  """
+  pub config: ModConfig! {
+    ModConfig(
+      path: path,
+      ws: ws,
+    )
+  }
+
   """
   Whether this module root or an ancestor contains a marker filename.
   """
diff --git a/typescript-sdk.dang b/typescript-sdk.dang
index 9c5ff1c..04675c5 100644
--- a/typescript-sdk.dang
+++ b/typescript-sdk.dang
@@ -95,8 +95,13 @@ type TypescriptSdk {
   By default, future generated SDK files are checked into version control. Pass
   `ignoreGenerated` to configure generation to add generated SDK paths to
   .gitignore instead.
+
+  Pass `packageManager` or `baseImage` to customize the generated config.
+  Defaults leave the template unconfigured: no `packageManager` field is
+  written, and no base image override is set. `packageManager` is invalid
+  with `runtime = DENO` since Deno does not use a Node package manager.
   """
-  pub init(ws: Workspace!, name: String!, path: String! = "", template: String! = "", runtime: Runtime! = Runtime.NODE, ignoreGenerated: Boolean! = false): Changeset! {
+  pub init(ws: Workspace!, name: String!, path: String! = "", template: String! = "", runtime: Runtime! = Runtime.NODE, ignoreGenerated: Boolean! = false, packageManager: String! = "", baseImage: String! = ""): Changeset! {
     let rawPath = if (path == "") {
       let daggerDir = ws.findUp(".dagger", ".")
       if (daggerDir == null) {
@@ -124,6 +129,8 @@ type TypescriptSdk {
       raise "module already exists: " + modPath
     } else if (currentModule.source.exists("templates/" + selectedTemplate) == false) {
       raise "unknown init template: " + template
+    } else if (runtime == Runtime.DENO and packageManager != "") {
+      raise "packageManager is only supported for node/bun runtimes; omit --package-manager when --runtime is DENO"
     } else {
       let includePrefix = if (modPath == ".") { "" } else { modPath + "/" }
       let existing = ws.directory("/", include: [
@@ -134,11 +141,12 @@ type TypescriptSdk {
       ])
 
       let config = "{\n  \"name\": " + toJSON(name) + ",\n  \"engineVersion\": \"latest\",\n  \"sdk\": {\n    \"source\": \"typescript\"\n  },\n  \"codegen\": {\n    \"automaticGitignore\": " + toJSON(ignoreGenerated) + "\n  }\n}\n"
-      let templateSource = if (selectedTemplate == "default") {
+      let renderedSource = if (selectedTemplate == "default") {
         renderedDefaultTemplate(name, runtime, existing, modPath)
       } else {
         currentModule.source.directory("templates/" + selectedTemplate)
       }
+      let templateSource = configuredTemplate(renderedSource, runtime, packageManager, baseImage)
       let seeded = fork
         .withDirectory(modPath, templateSource)
         .withNewFile(configPath, config)
@@ -224,6 +232,43 @@ type TypescriptSdk {
     withConfig.directory("/rendered")
   }
 
+  """
+  Apply non-default `packageManager` / `baseImage` flags to a rendered template.
+
+  When both flags are empty the source is returned unchanged (no helper run,
+  no reformatting). Otherwise the module-config helper edits the rendered
+  config files in place: `packageManager` always writes to package.json,
+  `baseImage` writes to deno.json for the DENO runtime and to package.json
+  otherwise — matching where ModConfig later reads from.
+  """
+  let configuredTemplate(source: Directory!, runtime: Runtime!, packageManager: String!, baseImage: String!): Directory! {
+    if (packageManager == "" and baseImage == "") {
+      source
+    } else {
+      let baseImageFile = if (runtime == Runtime.DENO) { "/rendered/deno.json" } else { "/rendered/package.json" }
+      let built = container
+        .from("golang:1.25-alpine")
+        .withoutEntrypoint
+        .withMountedCache("/go/pkg/mod", cacheVolume("go-mod"))
+        .withMountedCache("/root/.cache/go-build", cacheVolume("go-build"))
+        .withDirectory("/helper", currentModule.source.directory("helpers/module-config"))
+        .withWorkdir("/helper")
+        .withExec(["go", "build", "-o", "/usr/local/bin/module-config", "."])
+        .withDirectory("/rendered", source)
+      let withPm = if (packageManager == "") {
+        built
+      } else {
+        built.withExec(["module-config", "set-package-manager", "/rendered/package.json", packageManager])
+      }
+      let withImg = if (baseImage == "") {
+        withPm
+      } else {
+        withPm.withExec(["module-config", "set-base-image", baseImageFile, baseImage])
+      }
+      withImg.directory("/rendered")
+    }
+  }
+
   """
   Generate all discovered Go SDK modules.
   Modules with the generate skip marker are skipped.