diff --git a/package.json b/package.json
index 194a38b3..4d0ee612 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "prisma-cli",
-  "version": "8.0.0-rc.19",
+  "version": "8.0.0-rc.20",
   "private": true,
   "engines": {
     "node": ">=24"
diff --git a/packages/cli-conformance/package.json b/packages/cli-conformance/package.json
index 1d4d62ba..6c7502a1 100644
--- a/packages/cli-conformance/package.json
+++ b/packages/cli-conformance/package.json
@@ -1,7 +1,7 @@
 {
   "name": "@repo/cli-conformance",
   "private": true,
-  "version": "8.0.0-rc.19",
+  "version": "8.0.0-rc.20",
   "description": "Reusable conformance checks for the engine's consumers: import purity over built output, config-section validators that never throw, and verification of the tarballs a registry would receive. Depends on no package it checks.",
   "type": "module",
   "exports": {
@@ -24,7 +24,7 @@
     "test": "pnpm run typecheck && vitest run"
   },
   "devDependencies": {
-    "@repo/tsconfig": "workspace:8.0.0-rc.19",
+    "@repo/tsconfig": "workspace:8.0.0-rc.20",
     "@types/node": "^22.19.19",
     "es-module-lexer": "^2.1.0",
     "tsx": "^4.22.4",
diff --git a/packages/cli-engine/package.json b/packages/cli-engine/package.json
index 37f30a35..2d15f45c 100644
--- a/packages/cli-engine/package.json
+++ b/packages/cli-engine/package.json
@@ -59,8 +59,8 @@
   },
   "devDependencies": {
     "@prisma/management-api-sdk": "1.80.0",
-    "@repo/cli-conformance": "workspace:8.0.0-rc.19",
-    "@repo/tsconfig": "workspace:8.0.0-rc.19",
+    "@repo/cli-conformance": "workspace:8.0.0-rc.20",
+    "@repo/tsconfig": "workspace:8.0.0-rc.20",
     "@types/node": "^22.19.19",
     "ci-info": "^4.3.1",
     "tsdown": "^0.21.10",
diff --git a/packages/cli-telemetry/package.json b/packages/cli-telemetry/package.json
index b1ced912..92756274 100644
--- a/packages/cli-telemetry/package.json
+++ b/packages/cli-telemetry/package.json
@@ -1,7 +1,7 @@
 {
   "name": "@repo/cli-telemetry",
   "private": true,
-  "version": "8.0.0-rc.19",
+  "version": "8.0.0-rc.20",
   "description": "CLI telemetry child sender: the detached subprocess the engine hands a composed payload to, its system probes, and the POST",
   "type": "module",
   "sideEffects": [
@@ -35,7 +35,7 @@
     "@vercel/detect-agent": "^1.2.3"
   },
   "devDependencies": {
-    "@repo/tsconfig": "workspace:8.0.0-rc.19",
+    "@repo/tsconfig": "workspace:8.0.0-rc.20",
     "@types/node": "^22.19.19",
     "tsdown": "^0.21.10",
     "typescript": "^6.0.3",
diff --git a/packages/cli/package.json b/packages/cli/package.json
index ba369232..5f6da732 100644
--- a/packages/cli/package.json
+++ b/packages/cli/package.json
@@ -1,6 +1,6 @@
 {
   "name": "@prisma/cli",
-  "version": "8.0.0-rc.19",
+  "version": "8.0.0-rc.20",
   "description": "Command-line interface for the Prisma Developer Platform.",
   "type": "module",
   "bin": {
@@ -50,7 +50,7 @@
   "dependencies": {
     "@manypkg/tools": "^2.1.2",
     "@prisma/cli-engine": "workspace:0.6.2",
-    "@prisma/composer-cli": "0.25.0",
+    "@prisma/composer-cli": "0.26.0",
     "@prisma/compute-sdk": "0.43.0",
     "@prisma/management-api-sdk": "1.80.0",
     "@prisma/orm-toolchain": "8.0.0-rc.14",
@@ -62,11 +62,11 @@
     "open": "^11.0.0"
   },
   "devDependencies": {
-    "@prisma/composer": "0.25.0",
+    "@prisma/composer": "0.26.0",
     "@prisma/credentials-store": "^7.8.0",
-    "@repo/cli-conformance": "workspace:8.0.0-rc.19",
-    "@repo/cli-telemetry": "workspace:8.0.0-rc.19",
-    "@repo/tsconfig": "workspace:8.0.0-rc.19",
+    "@repo/cli-conformance": "workspace:8.0.0-rc.20",
+    "@repo/cli-telemetry": "workspace:8.0.0-rc.20",
+    "@repo/tsconfig": "workspace:8.0.0-rc.20",
     "@types/node": "^22.19.19",
     "@types/cross-spawn": "^6.0.6",
     "tsdown": "^0.21.10",
diff --git a/packages/cli/scripts/conformance.ts b/packages/cli/scripts/conformance.ts
index 0aad3038..d3f702d6 100644
--- a/packages/cli/scripts/conformance.ts
+++ b/packages/cli/scripts/conformance.ts
@@ -110,14 +110,6 @@ async function tarball(): Promise<readonly Finding[]> {
       enginePackage: "@prisma/cli-engine",
       familyPackages: ["@prisma/composer-cli", "@prisma/orm-toolchain"],
       exceptions: [
-        {
-          familyPackage: "@prisma/composer-cli",
-          familyPin: "0.6.1",
-          shellPin: "0.6.2",
-          reason: "engine 0.6.2 must publish before composer-cli can peer it",
-          removeWhen:
-            "composer-cli releases peering 0.6.2 and the follow-up bump PR pins that release",
-        },
         {
           familyPackage: "@prisma/orm-toolchain",
           familyPin: "0.6.1",
diff --git a/packages/cli/tests/bin.test.ts b/packages/cli/tests/bin.test.ts
index 689c69ef..82aa6f69 100644
--- a/packages/cli/tests/bin.test.ts
+++ b/packages/cli/tests/bin.test.ts
@@ -34,12 +34,20 @@ const MISSING_PRISMA_CONFIG_PATH = join(
   "missing-prisma.config.ts",
 );
 
-/** A prisma.config.ts whose only section is composer's. */
-const COMPOSER_SECTION_CONFIG_PATH = join(
+/** A composer section that still carries the retired `configPath`. */
+const COMPOSER_CONFIG_PATH_CONFIG_PATH = join(
   dirname(fileURLToPath(import.meta.url)),
   "fixtures",
   "config",
-  "composer-section.config.ts",
+  "composer-config-path.config.ts",
+);
+
+/** A composer section built with `@prisma/composer/config`. */
+const COMPOSER_VALID_CONFIG_PATH = join(
+  dirname(fileURLToPath(import.meta.url)),
+  "fixtures",
+  "config",
+  "composer-valid.config.ts",
 );
 
 const SEMVER_PREFIX = /^\d+\.\d+\.\d+/;
@@ -492,7 +500,10 @@ describe("buildCli", () => {
    *  stdout is not a TTY here, so the stream is JSON, and JSON escapes
    *  every separator in a Windows path — no path the CLI printed is a
    *  substring of the stream that carried it. */
-  function resultError(stdoutText: string): Diagnostic {
+  function resultFailure(stdoutText: string): {
+    readonly error: Diagnostic;
+    readonly diagnostics: readonly Diagnostic[];
+  } {
     const frames = stdoutText
       .split("\n")
       .filter((line) => line !== "")
@@ -501,81 +512,74 @@ describe("buildCli", () => {
     if (last?.kind !== "result" || last.envelope.ok) {
       throw new Error(`expected a failed result frame, got: ${stdoutText}`);
     }
-    return last.envelope.error;
+    return {
+      error: last.envelope.error,
+      diagnostics: last.envelope.diagnostics,
+    };
   }
 
-  /** Composer's `dev` through the real bin, against the fixture whose
-   *  composer section names a config file that is not there. */
-  async function runComposerDev(): Promise<{
+  /** Composer's `dev` through the real bin, reading the given config. */
+  async function runComposerDev(configPath: string): Promise<{
     readonly exitCode: number;
     readonly error: Diagnostic;
+    readonly diagnostics: readonly Diagnostic[];
   }> {
     const proc = makeProcess({
-      argv: [
-        "node",
-        "bin.js",
-        "dev",
-        "--config",
-        COMPOSER_SECTION_CONFIG_PATH,
-        "src/service.ts",
-      ],
+      argv: ["node", "bin.js", "dev", "--config", configPath, "src/service.ts"],
     });
 
     const exitCode = await main(proc);
-    return { exitCode, error: resultError(proc.stdoutText) };
+    return { exitCode, ...resultFailure(proc.stdoutText) };
   }
 
   /**
    * The mount's config wiring, end to end: the section name composer's
-   * family declares, read by the bin's real disk loader, reaching
-   * composer's own handler as the path it acts on.
-   *
-   * Every platform but Windows. `dev` is the only composer command
-   * that reaches config discovery without credentials — `deploy` stops
-   * at the credential check — and it refuses Windows before it reads
-   * the section it was handed, so no shipped command can show the
-   * section arriving there. The test after this one pins what Windows
-   * can still show.
+   * family declares, read by the bin's real disk loader and checked by
+   * composer's own validator before any handler runs, so every
+   * platform sees the same refusal.
    */
-  it.skipIf(process.platform === "win32")(
-    "hands the composer section of prisma.config.ts to the composer family",
-    async () => {
-      const { exitCode, error } = await runComposerDev();
-
-      expect(exitCode).toBe(2);
-      expect(error.code).toBe("CONFIG.FILE_MISSING");
-      // Composer resolves the section's relative path against the
-      // prisma.config.ts that declared it, not against the cwd.
-      expect(error.where?.path).toBe(
-        join(
-          dirname(COMPOSER_SECTION_CONFIG_PATH),
-          "named-by-the-section.config.ts",
-        ),
-      );
-      expect(error.why).toContain("there is no walk to fall back on");
-    },
-  );
+  it("refuses a composer section that still names a config file", async () => {
+    const { exitCode, error, diagnostics } = await runComposerDev(
+      COMPOSER_CONFIG_PATH_CONFIG_PATH,
+    );
+
+    expect(exitCode).toBe(2);
+    expect(error).toMatchObject({
+      code: "CLI.CONFIG_SECTION_INVALID",
+      summary: `The 'composer' section of ${COMPOSER_CONFIG_PATH_CONFIG_PATH} is invalid.`,
+    });
+    expect(diagnostics).toEqual([
+      expect.objectContaining({
+        code: "CONFIG.FIELD_RETIRED",
+        severity: "error",
+        meta: { field: "configPath" },
+        where: { path: COMPOSER_CONFIG_PATH_CONFIG_PATH },
+      }),
+    ]);
+  });
 
   /**
-   * What Windows still shows: the bin evaluated the config file, the
-   * engine accepted its `composer` section, and the command reached
-   * composer's own operation — which then refuses the platform. A
-   * mis-wired section would fail here as a config diagnostic instead.
-   * What it does not show is the section's path reaching composer's
-   * config discovery, since the refusal comes first.
-   *
-   * When composer supports Windows this test fails, and the pair
-   * collapses back into the one above.
+   * `dev --help` never evaluates the config, so a valid section shows
+   * only on a run that validates it: composer's validator accepts the
+   * section and the handler runs. Its first step imports the entry the
+   * host passed, which does not exist; on Windows the handler refuses
+   * the platform before that.
    */
-  it.runIf(process.platform === "win32")(
-    "on Windows, composer's dev refuses the platform before it reads the section",
-    async () => {
-      const { exitCode, error } = await runComposerDev();
+  it("hands a valid composer section to composer's dev", async () => {
+    const { exitCode, error } = await runComposerDev(
+      COMPOSER_VALID_CONFIG_PATH,
+    );
 
-      expect(exitCode).toBe(2);
-      expect(error.code).toBe("DEV.PLATFORM_UNSUPPORTED");
-    },
-  );
+    expect(exitCode).toBe(2);
+    expect(error).toMatchObject(
+      process.platform === "win32"
+        ? { code: "DEV.PLATFORM_UNSUPPORTED" }
+        : {
+            code: "COMPOSE.ENTRY_UNLOADABLE",
+            summary: expect.stringContaining(join("src", "service.ts")),
+          },
+    );
+  });
 
   it("runs --version through the real tree, printing the version with exit 0", async () => {
     const proc = makeProcess({
diff --git a/packages/cli/tests/fixtures/config/composer-section.config.ts b/packages/cli/tests/fixtures/config/composer-config-path.config.ts
similarity index 82%
rename from packages/cli/tests/fixtures/config/composer-section.config.ts
rename to packages/cli/tests/fixtures/config/composer-config-path.config.ts
index cbe4c293..fa5cfa37 100644
--- a/packages/cli/tests/fixtures/config/composer-section.config.ts
+++ b/packages/cli/tests/fixtures/config/composer-config-path.config.ts
@@ -4,6 +4,6 @@ import { definePrismaConfig } from "@prisma/cli-engine";
 // appearing in one of this repository's directories above these
 // fixtures can never join a test's chain.
 export default definePrismaConfig({
-  composer: { configPath: "./named-by-the-section.config.ts" },
+  composer: { configPath: "./prisma-composer.config.ts" },
   parent: false,
 });
diff --git a/packages/cli/tests/fixtures/config/composer-valid.config.ts b/packages/cli/tests/fixtures/config/composer-valid.config.ts
new file mode 100644
index 00000000..d4a31786
--- /dev/null
+++ b/packages/cli/tests/fixtures/config/composer-valid.config.ts
@@ -0,0 +1,18 @@
+import { definePrismaConfig } from "@prisma/cli-engine";
+import { defineConfig as composer } from "@prisma/composer/config";
+import { nodeBuild } from "@prisma/composer/node/control";
+
+const build = nodeBuild();
+
+export default definePrismaConfig({
+  composer: composer({
+    extensions: [build],
+    state: {
+      extension: build.id,
+      create: () => {
+        throw new Error("no command in these tests reaches the state store");
+      },
+    },
+  }),
+  parent: false,
+});
diff --git a/packages/compute/package.json b/packages/compute/package.json
index 5a6df494..3a75078b 100644
--- a/packages/compute/package.json
+++ b/packages/compute/package.json
@@ -42,7 +42,7 @@
     "test": "vitest run"
   },
   "devDependencies": {
-    "@repo/tsconfig": "workspace:8.0.0-rc.19",
+    "@repo/tsconfig": "workspace:8.0.0-rc.20",
     "@types/node": "^22.19.19",
     "tsdown": "^0.21.10",
     "typescript": "^6.0.3",
diff --git a/packages/prisma/package.json b/packages/prisma/package.json
index 34417d55..3361fe89 100644
--- a/packages/prisma/package.json
+++ b/packages/prisma/package.json
@@ -1,6 +1,6 @@
 {
   "name": "prisma",
-  "version": "8.0.0-rc.19",
+  "version": "8.0.0-rc.20",
   "description": "The Prisma CLI: one binary for the ORM, Composer, and the Prisma Developer Platform.",
   "type": "module",
   "bin": {
@@ -51,7 +51,7 @@
   "dependencies": {
     "@manypkg/tools": "^2.1.2",
     "@prisma/cli-engine": "workspace:0.6.2",
-    "@prisma/composer-cli": "0.25.0",
+    "@prisma/composer-cli": "0.26.0",
     "@prisma/compute-sdk": "0.43.0",
     "@prisma/management-api-sdk": "1.80.0",
     "@prisma/orm-toolchain": "8.0.0-rc.14",
@@ -63,10 +63,10 @@
     "open": "^11.0.0"
   },
   "devDependencies": {
-    "@prisma/cli": "workspace:8.0.0-rc.19",
+    "@prisma/cli": "workspace:8.0.0-rc.20",
     "@prisma/credentials-store": "^7.8.0",
-    "@repo/cli-telemetry": "workspace:8.0.0-rc.19",
-    "@repo/tsconfig": "workspace:8.0.0-rc.19",
+    "@repo/cli-telemetry": "workspace:8.0.0-rc.20",
+    "@repo/tsconfig": "workspace:8.0.0-rc.20",
     "@types/node": "^22.19.19",
     "tsdown": "^0.21.10",
     "typescript": "^6.0.3",
diff --git a/packages/tsconfig/package.json b/packages/tsconfig/package.json
index 816ac896..ad43a0f8 100644
--- a/packages/tsconfig/package.json
+++ b/packages/tsconfig/package.json
@@ -1,7 +1,7 @@
 {
   "name": "@repo/tsconfig",
   "private": true,
-  "version": "8.0.0-rc.19",
+  "version": "8.0.0-rc.20",
   "description": "Base tsconfig providing package for the monorepo",
   "license": "Apache-2.0",
   "files": [
diff --git a/pnpm-lock.yaml b/pnpm-lock.yaml
index 3bb09696..9fc6801d 100644
--- a/pnpm-lock.yaml
+++ b/pnpm-lock.yaml
@@ -30,8 +30,8 @@ importers:
         specifier: workspace:0.6.2
         version: link:../cli-engine
       '@prisma/composer-cli':
-        specifier: 0.25.0
-        version: 0.25.0(@prisma/cli-engine@packages+cli-engine)(@types/node@22.19.19)(@vercel/nft@1.10.2(rollup@4.62.2))(magicast@0.5.3)(mongodb@6.21.0(@aws-sdk/credential-providers@3.1107.0))(pg@8.23.0)(typescript@6.0.3)(vite@7.3.5(@types/node@22.19.19)(jiti@2.7.0)(tsx@4.22.4)(yaml@2.9.0))(vitest@4.1.8(@types/node@22.19.19)(vite@7.3.5(@types/node@22.19.19)(jiti@2.7.0)(tsx@4.22.4)(yaml@2.9.0)))(ws@8.21.0)
+        specifier: 0.26.0
+        version: 0.26.0(@prisma/cli-engine@packages+cli-engine)(@types/node@22.19.19)(@vercel/nft@1.10.2(rollup@4.62.2))(mongodb@6.21.0(@aws-sdk/credential-providers@3.1107.0))(pg@8.23.0)(typescript@6.0.3)(vite@7.3.5(@types/node@22.19.19)(jiti@2.7.0)(tsx@4.22.4)(yaml@2.9.0))(vitest@4.1.8(@types/node@22.19.19)(vite@7.3.5(@types/node@22.19.19)(jiti@2.7.0)(tsx@4.22.4)(yaml@2.9.0)))(ws@8.21.0)
       '@prisma/compute-sdk':
         specifier: 0.43.0
         version: 0.43.0(@prisma/management-api-sdk@1.80.0)(rollup@4.62.2)
@@ -61,19 +61,19 @@ importers:
         version: 11.0.0
     devDependencies:
       '@prisma/composer':
-        specifier: 0.25.0
-        version: 0.25.0(@types/node@22.19.19)(@vercel/nft@1.10.2(rollup@4.62.2))(magicast@0.5.3)(mongodb@6.21.0(@aws-sdk/credential-providers@3.1107.0))(pg@8.23.0)(typescript@6.0.3)(vite@7.3.5(@types/node@22.19.19)(jiti@2.7.0)(tsx@4.22.4)(yaml@2.9.0))(vitest@4.1.8(@types/node@22.19.19)(vite@7.3.5(@types/node@22.19.19)(jiti@2.7.0)(tsx@4.22.4)(yaml@2.9.0)))(ws@8.21.0)
+        specifier: 0.26.0
+        version: 0.26.0(@types/node@22.19.19)(@vercel/nft@1.10.2(rollup@4.62.2))(mongodb@6.21.0(@aws-sdk/credential-providers@3.1107.0))(pg@8.23.0)(typescript@6.0.3)(vite@7.3.5(@types/node@22.19.19)(jiti@2.7.0)(tsx@4.22.4)(yaml@2.9.0))(vitest@4.1.8(@types/node@22.19.19)(vite@7.3.5(@types/node@22.19.19)(jiti@2.7.0)(tsx@4.22.4)(yaml@2.9.0)))(ws@8.21.0)
       '@prisma/credentials-store':
         specifier: ^7.8.0
         version: 7.8.0
       '@repo/cli-conformance':
-        specifier: workspace:8.0.0-rc.19
+        specifier: workspace:8.0.0-rc.20
         version: link:../cli-conformance
       '@repo/cli-telemetry':
-        specifier: workspace:8.0.0-rc.19
+        specifier: workspace:8.0.0-rc.20
         version: link:../cli-telemetry
       '@repo/tsconfig':
-        specifier: workspace:8.0.0-rc.19
+        specifier: workspace:8.0.0-rc.20
         version: link:../tsconfig
       '@types/cross-spawn':
         specifier: ^6.0.6
@@ -97,7 +97,7 @@ importers:
   packages/cli-conformance:
     devDependencies:
       '@repo/tsconfig':
-        specifier: workspace:8.0.0-rc.19
+        specifier: workspace:8.0.0-rc.20
         version: link:../tsconfig
       '@types/node':
         specifier: ^22.19.19
@@ -143,10 +143,10 @@ importers:
         specifier: 1.80.0
         version: 1.80.0
       '@repo/cli-conformance':
-        specifier: workspace:8.0.0-rc.19
+        specifier: workspace:8.0.0-rc.20
         version: link:../cli-conformance
       '@repo/tsconfig':
-        specifier: workspace:8.0.0-rc.19
+        specifier: workspace:8.0.0-rc.20
         version: link:../tsconfig
       '@types/node':
         specifier: ^22.19.19
@@ -171,7 +171,7 @@ importers:
         version: 1.2.4
     devDependencies:
       '@repo/tsconfig':
-        specifier: workspace:8.0.0-rc.19
+        specifier: workspace:8.0.0-rc.20
         version: link:../tsconfig
       '@types/node':
         specifier: ^22.19.19
@@ -189,7 +189,7 @@ importers:
   packages/compute:
     devDependencies:
       '@repo/tsconfig':
-        specifier: workspace:8.0.0-rc.19
+        specifier: workspace:8.0.0-rc.20
         version: link:../tsconfig
       '@types/node':
         specifier: ^22.19.19
@@ -213,8 +213,8 @@ importers:
         specifier: workspace:0.6.2
         version: link:../cli-engine
       '@prisma/composer-cli':
-        specifier: 0.25.0
-        version: 0.25.0(@prisma/cli-engine@packages+cli-engine)(@types/node@22.19.19)(@vercel/nft@1.10.2(rollup@4.62.2))(magicast@0.5.3)(mongodb@6.21.0(@aws-sdk/credential-providers@3.1107.0))(pg@8.23.0)(typescript@6.0.3)(vite@7.3.5(@types/node@22.19.19)(jiti@2.7.0)(tsx@4.22.4)(yaml@2.9.0))(vitest@4.1.8(@types/node@22.19.19)(vite@7.3.5(@types/node@22.19.19)(jiti@2.7.0)(tsx@4.22.4)(yaml@2.9.0)))(ws@8.21.0)
+        specifier: 0.26.0
+        version: 0.26.0(@prisma/cli-engine@packages+cli-engine)(@types/node@22.19.19)(@vercel/nft@1.10.2(rollup@4.62.2))(mongodb@6.21.0(@aws-sdk/credential-providers@3.1107.0))(pg@8.23.0)(typescript@6.0.3)(vite@7.3.5(@types/node@22.19.19)(jiti@2.7.0)(tsx@4.22.4)(yaml@2.9.0))(vitest@4.1.8(@types/node@22.19.19)(vite@7.3.5(@types/node@22.19.19)(jiti@2.7.0)(tsx@4.22.4)(yaml@2.9.0)))(ws@8.21.0)
       '@prisma/compute-sdk':
         specifier: 0.43.0
         version: 0.43.0(@prisma/management-api-sdk@1.80.0)(rollup@4.62.2)
@@ -244,16 +244,16 @@ importers:
         version: 11.0.0
     devDependencies:
       '@prisma/cli':
-        specifier: workspace:8.0.0-rc.19
+        specifier: workspace:8.0.0-rc.20
         version: link:../cli
       '@prisma/credentials-store':
         specifier: ^7.8.0
         version: 7.8.0
       '@repo/cli-telemetry':
-        specifier: workspace:8.0.0-rc.19
+        specifier: workspace:8.0.0-rc.20
         version: link:../cli-telemetry
       '@repo/tsconfig':
-        specifier: workspace:8.0.0-rc.19
+        specifier: workspace:8.0.0-rc.20
         version: link:../tsconfig
       '@types/node':
         specifier: ^22.19.19
@@ -1301,15 +1301,14 @@ packages:
   '@oxc-project/types@0.146.0':
     resolution: {integrity: sha512-XC0QsnnhVe7sLIWmYmdPw7x5P0h4W8vUU3Nv1ySgWXtvCz8NizoAEpGXA0sOYoJQV2Rl13LgURAHQ5cI5ILCSA==}
 
-  '@prisma/composer-cli@0.25.0':
-    resolution: {integrity: sha512-f/v2S7eeCV7Nvqkb7+/BhHKfT3rtLq4nD/icE15FdkoN8CVysZZd2mUJXyBaAz6835lP3KfP9KGsIH7qnnTFpw==}
+  '@prisma/composer-cli@0.26.0':
+    resolution: {integrity: sha512-oBMN5FaAj0nyYGuVxfAaOMH4+74myWfb0YcPZAi4CndSe/WeAWyMWu4tieSe67o0lcED77dKaRb57cMDfrdvVg==}
     engines: {node: '>=22.18.0'}
-    hasBin: true
     peerDependencies:
-      '@prisma/cli-engine': 0.6.1
+      '@prisma/cli-engine': 0.6.2
 
-  '@prisma/composer@0.25.0':
-    resolution: {integrity: sha512-il4IFTKvmLTU8LSLSqJD/q8EzEqUuIw+ZPJ4v7ZJd1yMW0uiwWnD5knrbVgftXytbTTjzgzgaO8Fq6s8+d9r1A==}
+  '@prisma/composer@0.26.0':
+    resolution: {integrity: sha512-ttALY7KPD8NkecI4vJP0q50FkD7Q7v77TftU34gBA312hqyJKxD3hk4wY6H+NmDBfQAW7VDq8JCv1hGxx/aXJw==}
     engines: {node: '>=22.18.0'}
 
   '@prisma/compute-sdk@0.43.0':
@@ -4013,12 +4012,11 @@ snapshots:
 
   '@oxc-project/types@0.146.0': {}
 
-  '@prisma/composer-cli@0.25.0(@prisma/cli-engine@packages+cli-engine)(@types/node@22.19.19)(@vercel/nft@1.10.2(rollup@4.62.2))(magicast@0.5.3)(mongodb@6.21.0(@aws-sdk/credential-providers@3.1107.0))(pg@8.23.0)(typescript@6.0.3)(vite@7.3.5(@types/node@22.19.19)(jiti@2.7.0)(tsx@4.22.4)(yaml@2.9.0))(vitest@4.1.8(@types/node@22.19.19)(vite@7.3.5(@types/node@22.19.19)(jiti@2.7.0)(tsx@4.22.4)(yaml@2.9.0)))(ws@8.21.0)':
+  '@prisma/composer-cli@0.26.0(@prisma/cli-engine@packages+cli-engine)(@types/node@22.19.19)(@vercel/nft@1.10.2(rollup@4.62.2))(mongodb@6.21.0(@aws-sdk/credential-providers@3.1107.0))(pg@8.23.0)(typescript@6.0.3)(vite@7.3.5(@types/node@22.19.19)(jiti@2.7.0)(tsx@4.22.4)(yaml@2.9.0))(vitest@4.1.8(@types/node@22.19.19)(vite@7.3.5(@types/node@22.19.19)(jiti@2.7.0)(tsx@4.22.4)(yaml@2.9.0)))(ws@8.21.0)':
     dependencies:
       '@prisma/cli-engine': link:packages/cli-engine
-      '@prisma/composer': 0.25.0(@types/node@22.19.19)(@vercel/nft@1.10.2(rollup@4.62.2))(magicast@0.5.3)(mongodb@6.21.0(@aws-sdk/credential-providers@3.1107.0))(pg@8.23.0)(typescript@6.0.3)(vite@7.3.5(@types/node@22.19.19)(jiti@2.7.0)(tsx@4.22.4)(yaml@2.9.0))(vitest@4.1.8(@types/node@22.19.19)(vite@7.3.5(@types/node@22.19.19)(jiti@2.7.0)(tsx@4.22.4)(yaml@2.9.0)))(ws@8.21.0)
+      '@prisma/composer': 0.26.0(@types/node@22.19.19)(@vercel/nft@1.10.2(rollup@4.62.2))(mongodb@6.21.0(@aws-sdk/credential-providers@3.1107.0))(pg@8.23.0)(typescript@6.0.3)(vite@7.3.5(@types/node@22.19.19)(jiti@2.7.0)(tsx@4.22.4)(yaml@2.9.0))(vitest@4.1.8(@types/node@22.19.19)(vite@7.3.5(@types/node@22.19.19)(jiti@2.7.0)(tsx@4.22.4)(yaml@2.9.0)))(ws@8.21.0)
       alchemy: 2.0.0-beta.78(@types/node@22.19.19)(@vercel/nft@1.10.2(rollup@4.62.2))(effect@4.0.0-rc.115)(mongodb@6.21.0(@aws-sdk/credential-providers@3.1107.0))(pg@8.23.0)(typescript@6.0.3)(vite@7.3.5(@types/node@22.19.19)(jiti@2.7.0)(tsx@4.22.4)(yaml@2.9.0))(vitest@4.1.8(@types/node@22.19.19)(vite@7.3.5(@types/node@22.19.19)(jiti@2.7.0)(tsx@4.22.4)(yaml@2.9.0)))(ws@8.21.0)
-      c12: 3.3.4(magicast@0.5.3)
       cross-spawn: 7.0.6
       effect: 4.0.0-rc.115
       esbuild: 0.28.2
@@ -4035,7 +4033,6 @@ snapshots:
       - bufferutil
       - drizzle-kit
       - drizzle-orm
-      - magicast
       - mongodb
       - mysql2
       - pg
@@ -4047,7 +4044,7 @@ snapshots:
       - vitest
       - ws
 
-  '@prisma/composer@0.25.0(@types/node@22.19.19)(@vercel/nft@1.10.2(rollup@4.62.2))(magicast@0.5.3)(mongodb@6.21.0(@aws-sdk/credential-providers@3.1107.0))(pg@8.23.0)(typescript@6.0.3)(vite@7.3.5(@types/node@22.19.19)(jiti@2.7.0)(tsx@4.22.4)(yaml@2.9.0))(vitest@4.1.8(@types/node@22.19.19)(vite@7.3.5(@types/node@22.19.19)(jiti@2.7.0)(tsx@4.22.4)(yaml@2.9.0)))(ws@8.21.0)':
+  '@prisma/composer@0.26.0(@types/node@22.19.19)(@vercel/nft@1.10.2(rollup@4.62.2))(mongodb@6.21.0(@aws-sdk/credential-providers@3.1107.0))(pg@8.23.0)(typescript@6.0.3)(vite@7.3.5(@types/node@22.19.19)(jiti@2.7.0)(tsx@4.22.4)(yaml@2.9.0))(vitest@4.1.8(@types/node@22.19.19)(vite@7.3.5(@types/node@22.19.19)(jiti@2.7.0)(tsx@4.22.4)(yaml@2.9.0)))(ws@8.21.0)':
     dependencies:
       '@effect/sql-d1': 4.0.0-rc.115(effect@4.0.0-rc.115)
       '@effect/sql-sqlite-do': 4.0.0-rc.115(effect@4.0.0-rc.115)
@@ -4056,7 +4053,6 @@ snapshots:
       '@standard-schema/spec': 1.1.0
       alchemy: 2.0.0-beta.78(@types/node@22.19.19)(@vercel/nft@1.10.2(rollup@4.62.2))(effect@4.0.0-rc.115)(mongodb@6.21.0(@aws-sdk/credential-providers@3.1107.0))(pg@8.23.0)(typescript@6.0.3)(vite@7.3.5(@types/node@22.19.19)(jiti@2.7.0)(tsx@4.22.4)(yaml@2.9.0))(vitest@4.1.8(@types/node@22.19.19)(vite@7.3.5(@types/node@22.19.19)(jiti@2.7.0)(tsx@4.22.4)(yaml@2.9.0)))(ws@8.21.0)
       arktype: 2.2.3
-      c12: 3.3.4(magicast@0.5.3)
       cross-spawn: 7.0.6
       effect: 4.0.0-rc.115
       esbuild: 0.28.2
@@ -4073,7 +4069,6 @@ snapshots:
       - bufferutil
       - drizzle-kit
       - drizzle-orm
-      - magicast
       - mongodb
       - mysql2
       - pg
diff --git a/skills/prisma-platform-core-concepts/SKILL.md b/skills/prisma-platform-core-concepts/SKILL.md
index c24971fb..74ca3d3f 100644
--- a/skills/prisma-platform-core-concepts/SKILL.md
+++ b/skills/prisma-platform-core-concepts/SKILL.md
@@ -2,7 +2,7 @@
 name: prisma-platform-core-concepts
 metadata:
   library: "prisma"
-  library_version: "8.0.0-rc.19"
+  library_version: "8.0.0-rc.20"
   version: 2026.9.2
 description: >-
   Use when hosting, deploying, or operating an app on the Prisma Platform:
@@ -71,26 +71,42 @@ packages (`prisma-composer-core-concepts` in `@prisma/composer`,
 `prisma-orm-core-concepts` in `@prisma/orm-postgres`), so they appear after
 this install plus `prisma skills sync`, not before.
 
-Two config files with different owners:
-
-1. `prisma.config.ts` configures the CLI. Each top-level key is a section
-   owned by one product, and this CLI recognises exactly three: `orm`,
-   `composer`, and `skills`. The composed shape:
-
-   ```ts
-   import { definePrismaConfig } from "prisma/config";
-   import { defineConfig } from "@prisma/orm-postgres/config";
-
-   export default definePrismaConfig({
-     orm: defineConfig({ contract: "./src/prisma/contract.prisma" }),
-     skills: { agents: ["claude"] },
-   });
-   ```
+One config file, `prisma.config.ts`, configures the CLI and every product
+it runs. Each top-level key is a section owned by one product, and this CLI
+recognises exactly three: `orm`, `composer`, and `skills`. The composed
+shape:
+
+```ts
+import { definePrismaConfig } from "prisma/config";
+import { defineConfig as composer } from "@prisma/composer/config";
+import { nodeBuild } from "@prisma/composer/node/control";
+import {
+  prismaCloud,
+  prismaState,
+} from "@prisma/composer-prisma-cloud/control";
+import { defineConfig as orm } from "@prisma/orm-postgres/config";
+
+export default definePrismaConfig({
+  composer: composer({
+    extensions: [prismaCloud(), nodeBuild()],
+    state: prismaState(),
+  }),
+  orm: orm({ contract: "./src/prisma/contract.prisma" }),
+  skills: { agents: ["claude"] },
+});
+```
 
-2. `prisma-composer.config.ts` configures Composer itself and is a separate,
-   mandatory file for `dev` and `deploy`: without it `dev` fails with
-   `CONFIG.FILE_MISSING`. Its contents belong to
-   `prisma-composer-core-concepts`.
+`dev` and `deploy` read the `composer` section and nothing else; what goes
+in it belongs to `prisma-composer-core-concepts`. A separate
+`prisma-composer.config.ts` is no longer read, and the old setup is refused,
+never silently ignored: `CONFIG.SECTION_MISSING` when no loaded
+`prisma.config.ts` declares a `composer` section, `CONFIG.FIELD_RETIRED`
+when the section still has `configPath`, and `CONFIG.FILE_RETIRED` when a
+`prisma-composer.config.*` sits next to the declaring `prisma.config.ts`.
+All three arrive under the CLI's `CLI.CONFIG_SECTION_INVALID`. For
+`CONFIG.SECTION_MISSING`, write the section. For the other two, move the
+old file's `extensions` and `state` into the section, then delete the
+`configPath` field or the old file.
 
 ## The resource model