diff --git a/src/cache/keys.test.ts b/src/cache/keys.test.ts
index e912659b4e..d4a1e0955a 100644
--- a/src/cache/keys.test.ts
+++ b/src/cache/keys.test.ts
@@ -340,6 +340,37 @@ describe("cache/keys", () => {
       assertEquals(release.includes("release:release-1"), true);
     });
 
+    it("separates preview environments so adapter identities cannot collide", () => {
+      const unnamed = buildProxyManagerCacheKey("example-project", false, null, "main");
+      const preview = buildProxyManagerCacheKey("example-project", false, null, "main", "preview");
+
+      assertNotEquals(unnamed, preview);
+    });
+
+    it("separates distinct preview environment names on the same branch", () => {
+      const preview = buildProxyManagerCacheKey("example-project", false, null, "main", "preview");
+      const staging = buildProxyManagerCacheKey("example-project", false, null, "main", "staging");
+
+      assertNotEquals(preview, staging);
+    });
+
+    it("keeps the branch key stable when no environment is named", () => {
+      assertEquals(
+        buildProxyManagerCacheKey("example-project", false, null, "main"),
+        "proxy:example-project:preview:main",
+      );
+    });
+
+    it("escapes delimiters in an environment name", () => {
+      const forged = buildProxyManagerCacheKey("example-project", false, null, "main", "a:b");
+
+      assertEquals(forged.includes("a:b"), false);
+      assertNotEquals(
+        forged,
+        buildProxyManagerCacheKey("example-project", false, null, "main", "a"),
+      );
+    });
+
     it("separates canonical projects and credential principals", () => {
       const first = buildProxyManagerCacheKey(
         "reusable-slug",
diff --git a/src/cache/keys/builders/render.ts b/src/cache/keys/builders/render.ts
index de22c2c753..f64c0de8d7 100644
--- a/src/cache/keys/builders/render.ts
+++ b/src/cache/keys/builders/render.ts
@@ -138,7 +138,12 @@ export function buildProxyManagerCacheKey(
   }
 
   const source = encodeCacheSourceIdentity({ type: "branch", branch: branch ?? "main" });
-  return `${CacheKeyPrefix.PROXY}:${projectSlug}:${mode}:${source.qualifier}${authorityKey}`;
+  // ProxyFSAdapterManager asserts environmentName matches on reuse, so it must
+  // be part of the key. Omitted when unnamed to keep existing keys stable.
+  const environmentQualifier = environmentName
+    ? `:env:${encodeCacheKeyLiteralSegment(environmentName)}`
+    : "";
+  return `${CacheKeyPrefix.PROXY}:${projectSlug}:${mode}:${source.qualifier}${environmentQualifier}${authorityKey}`;
 }
 
 /**
diff --git a/src/platform/adapters/fs/veryfront/proxy-manager.test.ts b/src/platform/adapters/fs/veryfront/proxy-manager.test.ts
index 4d9877393c..a4cd67cfd4 100644
--- a/src/platform/adapters/fs/veryfront/proxy-manager.test.ts
+++ b/src/platform/adapters/fs/veryfront/proxy-manager.test.ts
@@ -5,6 +5,7 @@ import {
   assertExists,
   assertNotStrictEquals,
   assertRejects,
+  assertStrictEquals,
   assertThrows,
 } from "#veryfront/testing/assert.ts";
 import { describe, it } from "#veryfront/testing/bdd.ts";
@@ -138,6 +139,168 @@ describe("ProxyFSAdapterManager", () => {
     });
   });
 
+  describe("adapter identity", () => {
+    function stubbedManager(): ProxyFSAdapterManager {
+      return createManager({
+        adapterFactory: (config) => {
+          const adapter = new VeryfrontFSAdapter(config);
+          adapter.initialize = () => Promise.resolve();
+          return adapter;
+        },
+      });
+    }
+
+    it("keeps distinct preview environments on separate adapters", async () => {
+      const manager = stubbedManager();
+      try {
+        const unnamed = await manager.getAdapter(
+          "my-project",
+          "test-token",
+          undefined,
+          false,
+          null,
+          null,
+          "main",
+        );
+        const preview = await manager.getAdapter(
+          "my-project",
+          "test-token",
+          undefined,
+          false,
+          null,
+          "preview",
+          "main",
+        );
+
+        assertNotStrictEquals(unnamed, preview);
+      } finally {
+        manager.dispose();
+      }
+    });
+
+    it("reuses an unnamed preview adapter after a named one is created", async () => {
+      const manager = stubbedManager();
+      try {
+        const first = await manager.getAdapter(
+          "my-project",
+          "test-token",
+          undefined,
+          false,
+          null,
+          null,
+          "main",
+        );
+        const named = await manager.getAdapter(
+          "my-project",
+          "test-token",
+          undefined,
+          false,
+          null,
+          "preview",
+          "main",
+        );
+        const again = await manager.getAdapter(
+          "my-project",
+          "test-token",
+          undefined,
+          false,
+          null,
+          null,
+          "main",
+        );
+
+        assertNotStrictEquals(first, named);
+        assertStrictEquals(first, again);
+      } finally {
+        manager.dispose();
+      }
+    });
+
+    it("treats an empty environment name as unnamed", async () => {
+      const manager = stubbedManager();
+      try {
+        const empty = await manager.getAdapter(
+          "my-project",
+          "test-token",
+          undefined,
+          false,
+          null,
+          "",
+          "main",
+        );
+        const unnamed = await manager.getAdapter(
+          "my-project",
+          "test-token",
+          undefined,
+          false,
+          null,
+          null,
+          "main",
+        );
+
+        assertStrictEquals(empty, unnamed);
+      } finally {
+        manager.dispose();
+      }
+    });
+
+    it("ignores releaseId when resolving a preview adapter identity", async () => {
+      const manager = stubbedManager();
+      try {
+        const withRelease = await manager.getAdapter(
+          "my-project",
+          "test-token",
+          undefined,
+          false,
+          "release-7",
+          null,
+          "main",
+        );
+        const withoutRelease = await manager.getAdapter(
+          "my-project",
+          "test-token",
+          undefined,
+          false,
+          null,
+          null,
+          "main",
+        );
+
+        assertStrictEquals(withRelease, withoutRelease);
+      } finally {
+        manager.dispose();
+      }
+    });
+
+    it("ignores branch when resolving a production adapter identity", async () => {
+      const manager = stubbedManager();
+      try {
+        const withBranch = await manager.getAdapter(
+          "my-project",
+          "test-token",
+          undefined,
+          true,
+          "release-42",
+          "Production",
+          "main",
+        );
+        const withoutBranch = await manager.getAdapter(
+          "my-project",
+          "test-token",
+          undefined,
+          true,
+          "release-42",
+          "Production",
+          null,
+        );
+
+        assertStrictEquals(withBranch, withoutBranch);
+      } finally {
+        manager.dispose();
+      }
+    });
+  });
+
   describe("exact production source", () => {
     it("rejects mutable environment selection without an immutable release", async () => {
       const manager = createManager();
diff --git a/src/platform/adapters/fs/veryfront/proxy-manager.ts b/src/platform/adapters/fs/veryfront/proxy-manager.ts
index 4e9d5076f2..c17b605733 100644
--- a/src/platform/adapters/fs/veryfront/proxy-manager.ts
+++ b/src/platform/adapters/fs/veryfront/proxy-manager.ts
@@ -123,9 +123,11 @@ export class ProxyFSAdapterManager {
     const getAdapterStartTime = performance.now();
 
     const effectiveProductionMode = productionMode ?? false;
-    const effectiveReleaseId = releaseId ?? null;
-    const effectiveEnvironmentName = environmentName ?? null;
-    const effectiveBranch = branch ?? (effectiveProductionMode ? null : "main");
+    // All three must use the same predicate the cache key uses, or an identity
+    // that is not part of the key can still differ and fail the reuse assertion.
+    const effectiveReleaseId = effectiveProductionMode ? (releaseId ?? null) : null;
+    const effectiveEnvironmentName = environmentName || null;
+    const effectiveBranch = effectiveProductionMode ? null : (branch ?? "main");
 
     if (
       this.baseConfig.veryfront?.proxyMode === true &&
diff --git a/src/server/handlers/preview/hmr.handler.test.ts b/src/server/handlers/preview/hmr.handler.test.ts
index 0718ba8bb9..01c1210d32 100644
--- a/src/server/handlers/preview/hmr.handler.test.ts
+++ b/src/server/handlers/preview/hmr.handler.test.ts
@@ -547,4 +547,43 @@ describe("server/handlers/preview/hmr.handler", () => {
       assertEquals(result.response!.status, 501);
     });
   });
+
+  describe("ensureAdapterInitialized", () => {
+    it("warms the adapter for the named environment, not the mode", async () => {
+      let observed: Record<string, unknown> | undefined;
+      const handler = new HMRHandler();
+      const ctx = {
+        projectSlug: "demo-project",
+        proxyToken: "test-token",
+        projectId: "proj_123",
+        resolvedEnvironment: "preview",
+        environmentName: "Development",
+        requestContext: { branch: "main" },
+        adapter: {
+          fs: {
+            isVeryfrontAdapter: () => true,
+            getUnderlyingAdapter: () => undefined,
+            isMultiProjectMode: () => true,
+            runWithContext: (
+              _slug: string,
+              _token: string,
+              run: () => Promise<void>,
+              _projectId: string,
+              options: Record<string, unknown>,
+            ) => {
+              observed = options;
+              return run();
+            },
+            exists: () => Promise.resolve(true),
+          },
+        },
+      } as unknown as HandlerContext;
+
+      await (handler as unknown as {
+        ensureAdapterInitialized(ctx: HandlerContext): Promise<void>;
+      }).ensureAdapterInitialized(ctx);
+
+      assertEquals(observed?.environmentName, "Development");
+    });
+  });
 });
diff --git a/src/server/handlers/preview/hmr.handler.ts b/src/server/handlers/preview/hmr.handler.ts
index 6aa325ebd3..cfd9bce69b 100644
--- a/src/server/handlers/preview/hmr.handler.ts
+++ b/src/server/handlers/preview/hmr.handler.ts
@@ -248,6 +248,10 @@ export class HMRHandler extends BaseHandler {
         {
           productionMode: false,
           branch: ctx.requestContext?.branch ?? "main",
+          // The named environment, not the mode in `resolvedEnvironment`. Must
+          // match what renders resolve, or HMR warms a different adapter and
+          // its WebSocketManager never receives pokes.
+          environmentName: ctx.environmentName ?? null,
         },
       );
     } catch (error) {