diff --git a/README.md b/README.md
index b640b88..650ec08 100644
--- a/README.md
+++ b/README.md
@@ -10,7 +10,7 @@ Shared, language-agnostic operations — editing a module's dependencies or its
 required engine version — are owned by the core CLI (`dagger module deps`,
 `dagger module engine`) and are no longer part of this module's surface.
 
-Backed by [`github.com/dagger/sdk-sdk/polyfill`](https://github.com/dagger/sdk-sdk/tree/main/polyfill).
+It uses the engine's native `Workspace` and `ModuleSource` APIs directly.
 
 ## Install
 
diff --git a/dagger.json b/dagger.json
index 8831c47..5bcfdef 100644
--- a/dagger.json
+++ b/dagger.json
@@ -1,14 +1,7 @@
 {
   "name": "python-sdk",
-  "engineVersion": "v1.0.0-0",
+  "engineVersion": "v1.0.0-beta.10",
   "sdk": {
     "source": "dang"
-  },
-  "dependencies": [
-    {
-      "name": "polyfill",
-      "source": "github.com/dagger/polyfill@main",
-      "pin": "16627066d1852106320bdc0cfa0e5f901efe5970"
-    }
-  ]
+  }
 }
diff --git a/dagger.lock b/dagger.lock
index 7e5723d..122494c 100644
--- a/dagger.lock
+++ b/dagger.lock
@@ -1,3 +1,2 @@
 [["version","1"]]
 ["","git.head",["https://github.com/dagger/sdk-sdk"],"e1747f4b6221fa24da080701e027243e0cc5fa33","float"]
-["","git.ref",["https://github.com/dagger/polyfill","main"],"ec3ea84a2351b4beb06ecece951f2e5ef66509ff","float"]
\ No newline at end of file
diff --git a/docs/cwd-aware-discovery.md b/docs/cwd-aware-discovery.md
index e342183..f26e229 100644
--- a/docs/cwd-aware-discovery.md
+++ b/docs/cwd-aware-discovery.md
@@ -1,14 +1,13 @@
 # CWD-aware module discovery
 
-The Python SDK delegates config discovery to `github.com/dagger/polyfill`, then
-intersects the discovered directories with `currentModule.asSDK.modules`. The
-engine's managed-module list remains authoritative while the caller's current
-directory determines scope.
+The Python SDK asks
+`currentModule.asSDK(workspace: ws).modulesInScope` for the registered modules
+relevant to the caller's current directory. The engine owns both membership and
+scope selection, so the SDK does not scan config files or reconstruct the cwd
+policy.
 
-Discovery returns modules at or below the cwd and, when the cwd has no module
-config, its nearest enclosing module. Both `dagger-module.toml` and legacy
-`dagger.json` are considered together, so the nearest config wins regardless of
-filename. Virtual environments and installed packages are excluded.
+Selection returns modules at or below the cwd and, when the cwd itself is not a
+registered module, its nearest registered ancestor.
 
 ```console
 dagger check -l
@@ -16,5 +15,5 @@ dagger call e-2-e mixed-config-lookup-check
 dagger call e-2-e module-discovery-check
 ```
 
-The fixtures cover mixed nested config formats, modern and legacy configs,
-non-Python exclusion, root discovery, and discovery from inside a module.
+The fixtures cover mixed nested config formats, modern and legacy modules,
+non-Python exclusion, root selection, and selection from inside a module.
diff --git a/mod-config.dang b/mod-config.dang
index 818ced5..0d30523 100644
--- a/mod-config.dang
+++ b/mod-config.dang
@@ -83,7 +83,7 @@ type ModConfig {
     }
 
     let edited = withImage.file(toolPath).contents
-    polyfill.workspace(ws).fork.withNewFile(pyprojectPath, edited).changes
+    ws.fork.withNewFile("/" + pyprojectPath, edited).changes
   }
 
   """
diff --git a/mod.dang b/mod.dang
index eac112e..bf9d754 100644
--- a/mod.dang
+++ b/mod.dang
@@ -56,12 +56,12 @@ type Mod {
   """
   pub generate: Changeset! {
     if (skipGenerate) {
-      polyfill.workspace(ws).fork.changes
+      ws.fork.changes
     } else {
       # Stage the local dependency closure so this module's codegen sees
       # up-to-date dependency bindings before generating it.
-      let stagedWs = ws.withChanges(polyfill.workspace(ws).moduleSource("/" + rootPath).core.generateLocalDependencies(ws))
-      polyfill.workspace(stagedWs).moduleSource("/" + rootPath).generate.changes
+      let stagedWs = ws.withChanges(ws.moduleSource("/" + rootPath).generateLocalDependencies(ws))
+      stagedWs.moduleSource("/" + rootPath).generatedContextChangeset
     }
   }
 }
diff --git a/python-sdk.dang b/python-sdk.dang
index 100d94f..8d2d7b4 100644
--- a/python-sdk.dang
+++ b/python-sdk.dang
@@ -17,34 +17,16 @@ type PythonSdk {
   pub targetRuntime: String! { "python" }
 
   """
-  Return every managed Python SDK module visible from the client's cwd: the
-  nearest enclosing module plus modules at or below the cwd. Discovery uses the
-  shared polyfill and intersects its results with the SDK list on the passed
-  workspace.
+  Return every managed Python SDK module in the client's cwd scope: every module
+  at or below the cwd, plus the nearest enclosing module when the cwd itself is
+  not managed. The engine selects this directly from the workspace's registered
+  SDK modules; no filesystem discovery is required.
   """
   pub modules(ws: Workspace!): [Mod!]! {
-    let managed = currentModule.asSDK(workspace: ws).modules.{{path}}
-    let cwd = normalizePath(ws.cwd)
-    polyfill.workspace(ws)
-      .findConfigDirs(moduleConfigFilenames, exclude: ["**/.venv/**", "**/site-packages/**"])
-      .map { dir => workspacePath(cwd, dir) }
-      .uniq
-      .filter { path => managed.filter { m => normalizePath(m.path) == path }.length > 0 }
-      .map { path => Mod(rootPath: path, ws: ws, skipGenerateFilename: skipGenerateFilename) }
-  }
-
-  let workspacePath(cwd: String!, path: String!): String! {
-    let base = if (cwd == ".") { [] } else { cwd.split("/") }
-    let segments = path.split("/").reduce(base) { acc, segment =>
-      if (segment == "..") {
-        acc.dropLast(1)
-      } else if (segment == "." or segment == "") {
-        acc
-      } else {
-        acc + [segment]
-      }
-    }
-    if (segments.length == 0) { "." } else { segments.join("/") }
+    currentModule
+      .asSDK(workspace: ws)
+      .modulesInScope.{{path}}
+      .map { module => Mod(rootPath: module.path, ws: ws, skipGenerateFilename: skipGenerateFilename) }
   }
 
   let normalizePath(path: String!): String! {
@@ -162,8 +144,8 @@ type PythonSdk {
     } else {
       let templateSource = configuredTemplate(renderedTemplate(name, selectedTemplate), pythonVersion, useUv, baseImage)
 
-      polyfill.workspace(ws).fork
-        .withDirectory(modPath, templateSource)
+      ws.fork
+        .withNewDirectory("/" + modPath, templateSource)
         .changes
     }
   }
@@ -219,18 +201,17 @@ type PythonSdk {
   Modules with the generate skip marker are skipped.
   """
   pub generateAll(ws: Workspace!): Changeset! @generate {
-    let pws = polyfill.workspace(ws)
-
-    modules(ws)
-      .filter { mod => mod.skipGenerate == false }
-      .reduce(pws.fork) { fork, mod =>
-        # Stage this module's local dependency closure first (leaf-first, possibly
-        # across SDKs) so its codegen sees up-to-date dependency bindings. The dep
-        # codegen is ephemeral: it appears in both the fork's before and after, so
-        # it cancels in the merge, leaving only each module's own changes.
-        let stagedWs = ws.withChanges(pws.moduleSource("/" + mod.rootPath).core.generateLocalDependencies(ws))
-        fork.merge(polyfill.workspace(stagedWs).moduleSource("/" + mod.rootPath).generate)
-      }
-      .changes
+    changeset.withChangesets(
+      modules(ws)
+        .filter { mod => mod.skipGenerate == false }
+        .map { mod =>
+          # Stage this module's local dependency closure first (leaf-first, possibly
+          # across SDKs) so its codegen sees up-to-date dependency bindings. The dep
+          # codegen is ephemeral: taking the changeset against the staged workspace
+          # cancels it out, leaving only each module's own changes.
+          let stagedWs = ws.withChanges(ws.moduleSource("/" + mod.rootPath).generateLocalDependencies(ws))
+          stagedWs.moduleSource("/" + mod.rootPath).generatedContextChangeset
+        },
+    )
   }
 }