diff --git a/packages/cli/src/auth/legacy-state.ts b/packages/cli/src/auth/legacy-state.ts
index 48e76c59..3302a2d0 100644
--- a/packages/cli/src/auth/legacy-state.ts
+++ b/packages/cli/src/auth/legacy-state.ts
@@ -1,3 +1,4 @@
+import { randomUUID } from "node:crypto";
 import fs from "node:fs/promises";
 import { claimedExpiresAt, credentialWorkspaceId } from "@prisma/cli-engine";
 import type { CredentialState, StoredSession } from "./state-file";
@@ -5,6 +6,77 @@ import { getAuthContextFilePath } from "./token-storage";
 
 const LEGACY_PLACEHOLDER_NAME = "Unknown workspace";
 
+/**
+ * The sessions re-serialized in the legacy store's record shape. The
+ * 3.x CLI reads `tokens` from auth.json (`data.tokens || []`, silently
+ * empty for any other shape), so a write that dropped the key made
+ * every session invisible to `@prisma/cli@latest` on the same machine
+ * the moment this CLI first mutated the file (#204). Sessions without
+ * a refresh token still mirror; the legacy reader skips them, exactly
+ * as it skips its own unrefreshable records.
+ */
+export function legacyTokensMirror(
+  sessions: readonly StoredSession[],
+): readonly { workspaceId: string; token: string; refreshToken?: string }[] {
+  return sessions.map((session) => ({
+    workspaceId: session.workspaceId,
+    token: session.token,
+    ...(session.refreshToken === undefined
+      ? {}
+      : { refreshToken: session.refreshToken }),
+  }));
+}
+
+/**
+ * Keeps auth.context.json's `activeWorkspaceId` — the pointer the 3.x
+ * CLI selects its session with — in step with `currentWorkspaceId`.
+ * The rest of the context file (the remembered-workspace name map) is
+ * preserved verbatim; only the pointer moves.
+ */
+export async function syncLegacyContext(
+  authFilePath: string,
+  currentWorkspaceId: string | null,
+): Promise<void> {
+  const contextFilePath = getAuthContextFilePath(authFilePath);
+  const context = await readLegacyContext(contextFilePath);
+  if (context.exists && context.activeWorkspaceId === currentWorkspaceId) {
+    return;
+  }
+  // No file and nothing selected stays no file: an existing context
+  // with a null pointer reads as "explicitly signed out" to the 3.x
+  // CLI, where an absent one lets it self-activate its latest session.
+  if (!context.exists && currentWorkspaceId === null) {
+    return;
+  }
+  const raw = await fs.readFile(contextFilePath, "utf8").catch(() => null);
+  let workspaces: unknown = {};
+  if (raw !== null) {
+    try {
+      const parsed = JSON.parse(raw) as { workspaces?: unknown };
+      if (
+        typeof parsed.workspaces === "object" &&
+        parsed.workspaces !== null &&
+        !Array.isArray(parsed.workspaces)
+      ) {
+        workspaces = parsed.workspaces;
+      }
+    } catch {
+      // A corrupt context file is replaced with a fresh one.
+    }
+  }
+  // Temp + rename like the auth file itself: a torn context file makes
+  // the 3.x CLI silently self-activate its latest session.
+  const tempPath = `${contextFilePath}.${randomUUID()}.tmp`;
+  const payload = `${JSON.stringify({ activeWorkspaceId: currentWorkspaceId, workspaces }, null, 2)}\n`;
+  try {
+    await fs.writeFile(tempPath, payload, "utf8");
+    await fs.rename(tempPath, contextFilePath);
+  } catch (error) {
+    await fs.unlink(tempPath).catch(() => {});
+    throw error;
+  }
+}
+
 interface LegacyContext {
   readonly exists: boolean;
   readonly activeWorkspaceId: string | null;
diff --git a/packages/cli/src/auth/state-file.ts b/packages/cli/src/auth/state-file.ts
index b8fcd6d0..a22f4908 100644
--- a/packages/cli/src/auth/state-file.ts
+++ b/packages/cli/src/auth/state-file.ts
@@ -4,7 +4,11 @@ import fs from "node:fs/promises";
 import path from "node:path";
 import { CliStructuredError } from "@prisma/cli-engine/protocol";
 import { defaultAuthFilePath } from "./client";
-import { adoptLegacyState } from "./legacy-state";
+import {
+  adoptLegacyState,
+  legacyTokensMirror,
+  syncLegacyContext,
+} from "./legacy-state";
 
 export const STATE_FILE_ENV_VAR = "PRISMA_AUTH_FILE";
 export const DEPRECATED_STATE_FILE_ENV_VAR = "PRISMA_COMPUTE_AUTH_FILE";
@@ -188,13 +192,18 @@ function normalizeSession(session: StoredSession): StoredSession {
 }
 
 /** Temp file in the same directory, fsync, rename, mode 0600 — a reader
- *  only ever sees a complete state. */
+ *  only ever sees a complete state. The written file also carries the
+ *  legacy `tokens` mirror and the auth.context.json pointer stays in
+ *  step, so the 3.x CLI sharing this store keeps seeing the sessions
+ *  (#204). Our own reader branches on `sessions` before it ever looks
+ *  at `tokens`, so the mirror is invisible to this CLI. */
 export async function writeCredentialState(
   filePath: string,
   state: CredentialState,
 ): Promise<void> {
   await fs.mkdir(path.dirname(filePath), { recursive: true });
   const tempPath = `${filePath}.${randomUUID()}.tmp`;
+  const payload = { ...state, tokens: legacyTokensMirror(state.sessions) };
   // The temp file holds the whole state, tokens included, so no path
   // out of here may leave one behind: a write that fails after the
   // handle is open would otherwise strand a working credential copy
@@ -202,7 +211,7 @@ export async function writeCredentialState(
   try {
     const handle = await fs.open(tempPath, "wx", FILE_MODE);
     try {
-      await handle.writeFile(`${JSON.stringify(state, null, 2)}\n`, "utf8");
+      await handle.writeFile(`${JSON.stringify(payload, null, 2)}\n`, "utf8");
       await handle.sync();
     } finally {
       await handle.close();
@@ -213,6 +222,7 @@ export async function writeCredentialState(
     throw error;
   }
   await fs.chmod(filePath, FILE_MODE).catch(() => {});
+  await syncLegacyContext(filePath, state.currentWorkspaceId);
 }
 
 class StateLockTimeoutError extends CliStructuredError {
diff --git a/packages/cli/tests/credential-manager-migration.test.ts b/packages/cli/tests/credential-manager-migration.test.ts
index 43241cb4..ddb1e024 100644
--- a/packages/cli/tests/credential-manager-migration.test.ts
+++ b/packages/cli/tests/credential-manager-migration.test.ts
@@ -9,7 +9,11 @@ import { mintTestJwt } from "@prisma/cli-engine/testing";
 import { beforeEach, describe, expect, it } from "vitest";
 
 import { FileCredentialManager } from "../src/auth/credential-manager";
-import { readCredentialState } from "../src/auth/state-file";
+import {
+  EMPTY_STATE,
+  readCredentialState,
+  writeCredentialState,
+} from "../src/auth/state-file";
 import { getAuthContextFilePath } from "../src/auth/token-storage";
 
 const WORKSPACE_A = "wksp_a";
@@ -291,3 +295,200 @@ describe("adopting the legacy store", () => {
     await unlink(authFilePath);
   });
 });
+
+describe("the legacy mirror", () => {
+  /** Reads the store exactly as the 3.x CLI does (#204): sessions come
+   *  from auth.json's `tokens` array (`data.tokens || []`), selected by
+   *  auth.context.json's `activeWorkspaceId`, and a record without a
+   *  workspaceId, token, and refreshToken is skipped. */
+  async function readAsLegacyCli() {
+    const data = JSON.parse(await readFile(authFilePath, "utf8")) as {
+      tokens?: unknown[];
+    };
+    const tokens = data.tokens || [];
+    const context = JSON.parse(await readFile(contextFilePath, "utf8")) as {
+      activeWorkspaceId?: string | null;
+      workspaces?: Record<string, { name?: string }>;
+    };
+    const active = context.activeWorkspaceId;
+    if (!active) return null;
+    const credential = tokens.find(
+      (entry) => (entry as { workspaceId?: string })?.workspaceId === active,
+    ) as
+      | { workspaceId: string; token?: string; refreshToken?: string }
+      | undefined;
+    if (!credential?.token || !credential.refreshToken) return null;
+    return {
+      workspaceId: credential.workspaceId,
+      accessToken: credential.token,
+      refreshToken: credential.refreshToken,
+    };
+  }
+
+  it("a token refresh keeps the session visible to the 3.x reader", async () => {
+    await writeLegacyStore([legacyEntry(WORKSPACE_A, "legacy-refresh")]);
+    await writeLegacyContext({
+      activeWorkspaceId: WORKSPACE_A,
+      workspaces: { [WORKSPACE_A]: { name: "Alpha" } },
+    });
+
+    const manager = makeManager();
+    await manager.activeCredential();
+    const storage = await manager.activeCredentialStorage();
+    const rotatedToken = mintToken(WORKSPACE_A);
+    await storage.setTokens({
+      workspaceId: WORKSPACE_A,
+      accessToken: rotatedToken,
+      refreshToken: "rotated-refresh",
+    });
+
+    expect(await readAsLegacyCli()).toEqual({
+      workspaceId: WORKSPACE_A,
+      accessToken: rotatedToken,
+      refreshToken: "rotated-refresh",
+    });
+
+    const context = JSON.parse(await readFile(contextFilePath, "utf8")) as {
+      workspaces: Record<string, { name?: string }>;
+    };
+    expect(context.workspaces[WORKSPACE_A]?.name).toBe("Alpha");
+  });
+
+  it("creating and selecting sessions moves the 3.x active pointer with them", async () => {
+    const manager = makeManager();
+    const tokenA = mintToken(WORKSPACE_A);
+    const tokenB = mintToken(WORKSPACE_B);
+    await manager.createSession(
+      { token: tokenA, refreshToken: "ra", expiresAt: undefined },
+      WORKSPACE_A,
+    );
+    await manager.createSession(
+      { token: tokenB, refreshToken: "rb", expiresAt: undefined },
+      WORKSPACE_B,
+    );
+
+    expect((await readAsLegacyCli())?.workspaceId).toBe(WORKSPACE_B);
+
+    await manager.selectSession(WORKSPACE_A);
+    expect(await readAsLegacyCli()).toEqual({
+      workspaceId: WORKSPACE_A,
+      accessToken: tokenA,
+      refreshToken: "ra",
+    });
+  });
+
+  it("the mirror is invisible to this CLI's own reader", async () => {
+    const manager = makeManager();
+    await manager.createSession(
+      {
+        token: mintToken(WORKSPACE_A),
+        refreshToken: "r",
+        expiresAt: undefined,
+      },
+      WORKSPACE_A,
+    );
+
+    const state = await readCredentialState(authFilePath);
+    expect(Object.keys(state)).toEqual([
+      "version",
+      "sessions",
+      "currentWorkspaceId",
+    ]);
+    expect(state.sessions).toHaveLength(1);
+  });
+});
+
+describe("the legacy mirror's context sync", () => {
+  it("a pointer move preserves the remembered-workspace name map", async () => {
+    await writeLegacyStore([
+      legacyEntry(WORKSPACE_A, "ra"),
+      legacyEntry(WORKSPACE_B, "rb"),
+    ]);
+    await writeLegacyContext({
+      activeWorkspaceId: WORKSPACE_A,
+      workspaces: {
+        [WORKSPACE_A]: { name: "Alpha" },
+        [WORKSPACE_B]: { name: "Bravo" },
+      },
+    });
+
+    await makeManager().selectSession(WORKSPACE_B);
+
+    const context = JSON.parse(await readFile(contextFilePath, "utf8")) as {
+      activeWorkspaceId: string | null;
+      workspaces: Record<string, { name?: string }>;
+    };
+    expect(context.activeWorkspaceId).toBe(WORKSPACE_B);
+    expect(context.workspaces[WORKSPACE_A]?.name).toBe("Alpha");
+    expect(context.workspaces[WORKSPACE_B]?.name).toBe("Bravo");
+  });
+
+  it("writes no context file when none exists and nothing is selected", async () => {
+    await writeCredentialState(authFilePath, EMPTY_STATE);
+
+    await expect(readFile(contextFilePath, "utf8")).rejects.toMatchObject({
+      code: "ENOENT",
+    });
+  });
+});
+
+describe("ending sessions and the legacy mirror", () => {
+  async function readLegacyView() {
+    const data = JSON.parse(await readFile(authFilePath, "utf8")) as {
+      tokens?: { workspaceId: string }[];
+    };
+    const context = JSON.parse(await readFile(contextFilePath, "utf8")) as {
+      activeWorkspaceId?: string | null;
+    };
+    return {
+      tokenWorkspaces: (data.tokens ?? []).map((entry) => entry.workspaceId),
+      activeWorkspaceId: context.activeWorkspaceId ?? null,
+    };
+  }
+
+  it("ending a non-active session keeps the active one visible to the 3.x reader", async () => {
+    const manager = makeManager();
+    await manager.createSession(
+      {
+        token: mintToken(WORKSPACE_A),
+        refreshToken: "ra",
+        expiresAt: undefined,
+      },
+      WORKSPACE_A,
+    );
+    await manager.createSession(
+      {
+        token: mintToken(WORKSPACE_B),
+        refreshToken: "rb",
+        expiresAt: undefined,
+      },
+      WORKSPACE_B,
+    );
+
+    await manager.endSession(WORKSPACE_A);
+
+    expect(await readLegacyView()).toEqual({
+      tokenWorkspaces: [WORKSPACE_B],
+      activeWorkspaceId: WORKSPACE_B,
+    });
+  });
+
+  it("ending the active session clears the 3.x pointer with it", async () => {
+    const manager = makeManager();
+    await manager.createSession(
+      {
+        token: mintToken(WORKSPACE_A),
+        refreshToken: "ra",
+        expiresAt: undefined,
+      },
+      WORKSPACE_A,
+    );
+
+    await manager.endSession(WORKSPACE_A);
+
+    expect(await readLegacyView()).toEqual({
+      tokenWorkspaces: [],
+      activeWorkspaceId: null,
+    });
+  });
+});
diff --git a/packages/cli/tests/credential-manager.test.ts b/packages/cli/tests/credential-manager.test.ts
index 1b3abfcf..ed15458c 100644
--- a/packages/cli/tests/credential-manager.test.ts
+++ b/packages/cli/tests/credential-manager.test.ts
@@ -251,6 +251,8 @@ describe("the state file", () => {
     }
 
     const stateDir = path.dirname(stateFilePath);
+    // The trailing rename is the legacy auth.context.json mirror, which
+    // goes through its own temp file in the same directory.
     expect(order).toEqual([
       expect.stringMatching(
         new RegExp(`^open ${escapeForRegExp(stateFilePath)}\\..+\\.tmp$`),
@@ -261,6 +263,11 @@ describe("the state file", () => {
           `^rename ${escapeForRegExp(stateFilePath)}\\..+\\.tmp -> ${escapeForRegExp(stateFilePath)}$`,
         ),
       ),
+      expect.stringMatching(
+        new RegExp(
+          `\\.tmp -> ${escapeForRegExp(stateDir)}.*\\.context\\.json$`,
+        ),
+      ),
     ]);
     expect(
       (await readdir(stateDir)).filter((entry) => entry.endsWith(".tmp")),