diff --git a/extensions/signal/src/setup-core.test.ts b/extensions/signal/src/setup-core.test.ts
index 48af4625a986..9c57c28e0b4f 100644
--- a/extensions/signal/src/setup-core.test.ts
+++ b/extensions/signal/src/setup-core.test.ts
@@ -145,6 +145,47 @@ describe("signalSetupAdapter", () => {
     },
   );
 
+  it("clears the UUID when setup replaces the normalized Signal account", () => {
+    const next = signalSetupAdapter.applyAccountConfig?.({
+      cfg: {
+        channels: {
+          signal: {
+            accounts: {
+              work: {
+                account: "+15555550123",
+                accountUuid: "123e4567-e89b-12d3-a456-426614174000",
+              },
+            },
+          },
+        },
+      },
+      accountId: "work",
+      input: { signalNumber: "+15555550124" },
+    });
+
+    expect(next?.channels?.signal?.accounts?.work?.account).toBe("+15555550124");
+    expect(next?.channels?.signal?.accounts?.work?.accountUuid).toBeUndefined();
+  });
+
+  it("preserves the UUID when setup keeps the same normalized Signal account", () => {
+    const accountUuid = "123e4567-e89b-12d3-a456-426614174000";
+    const next = signalSetupAdapter.applyAccountConfig?.({
+      cfg: {
+        channels: {
+          signal: {
+            account: "+15555550123",
+            accountUuid,
+          },
+        },
+      },
+      accountId: "default",
+      input: { signalNumber: "signal: +1 (555) 555-0123" },
+    });
+
+    expect(next?.channels?.signal?.account).toBe("+15555550123");
+    expect(next?.channels?.signal?.accountUuid).toBe(accountUuid);
+  });
+
   it("restores a generically promoted default account before writing a named account", () => {
     const next = signalSetupAdapter.applyAccountConfig?.({
       cfg: {
diff --git a/extensions/signal/src/setup-core.ts b/extensions/signal/src/setup-core.ts
index 92a0fa320b91..a072ac53a48e 100644
--- a/extensions/signal/src/setup-core.ts
+++ b/extensions/signal/src/setup-core.ts
@@ -10,6 +10,7 @@ import {
   createPatchedAccountSetupAdapter,
   createSetupInputPresenceValidator,
   DEFAULT_ACCOUNT_ID,
+  patchChannelConfigForAccount,
   promptParsedAllowFromForAccount,
   setAccountAllowFromForChannel,
   setSetupChannelEnabled,
@@ -169,6 +170,10 @@ export function normalizeSignalAccountInput(value: string | null | undefined): s
   return `+${digits}`;
 }
 
+export function isSameSignalAccount(left: string | null | undefined, right: string): boolean {
+  return normalizeSignalAccountInput(left) === normalizeSignalAccountInput(right);
+}
+
 function isUuidLike(value: string): boolean {
   return /^[0-9a-f]{8}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{12}$/i.test(value);
 }
@@ -504,7 +509,18 @@ export const signalSetupAdapter: ChannelSetupAdapter<SignalSetupInput> = {
     // transport. Rejoin that pair here so Signal keeps one canonical default-account shape.
     const cfg = restorePromotedSignalDefaultAccount(params.cfg);
     const previousTransport = resolveConfiguredSignalTransport(cfg, accountId);
-    const next = signalSetupAdapterBase.applyAccountConfig?.({ ...params, cfg, accountId }) ?? cfg;
+    let next = signalSetupAdapterBase.applyAccountConfig?.({ ...params, cfg, accountId }) ?? cfg;
+    if (
+      suppliedAccount &&
+      !isSameSignalAccount(resolveSignalAccount({ cfg, accountId }).config.account, suppliedAccount)
+    ) {
+      next = patchChannelConfigForAccount({
+        cfg: next,
+        channel,
+        accountId,
+        patch: { accountUuid: undefined },
+      });
+    }
     const configuredTransport = resolveConfiguredSignalTransport(next, accountId);
     if (configuredTransport && configuredTransport.kind !== "managed-native") {
       const transport =
diff --git a/extensions/signal/src/setup-interactive.test.ts b/extensions/signal/src/setup-interactive.test.ts
index 0250fc3c52c5..b2f848d8d703 100644
--- a/extensions/signal/src/setup-interactive.test.ts
+++ b/extensions/signal/src/setup-interactive.test.ts
@@ -308,6 +308,39 @@ describe("Signal existing-server setup", () => {
     expect(finalized?.cfg?.channels?.signal?.account).toBe("+15555550123");
   });
 
+  it("preserves the UUID when recovery keeps the same normalized account", async () => {
+    mocks.probeSignalTransport.mockResolvedValueOnce({
+      ok: false,
+      error: "selected account is unavailable",
+    });
+    const accountUuid = "123e4567-e89b-12d3-a456-426614174000";
+    const queued = createQueuedWizardPrompter({
+      selectValues: ["account"],
+      textValues: ["signal: +1 (555) 555-0123"],
+    });
+
+    const finalized = await runSetupWizardFinalize({
+      finalize: signalSetupWizard.finalize,
+      cfg: {
+        channels: {
+          signal: {
+            account: "+15555550123",
+            accountUuid,
+          },
+        },
+      },
+      credentialValues: {
+        signalTransportKind: "external-native",
+        signalServerUrl: "http://signal-helper:8080",
+      },
+      prompter: queued.prompter,
+      runtime: createRuntimeEnv({ throwOnExit: false }),
+    });
+
+    expect(finalized?.cfg?.channels?.signal?.account).toBe("+15555550123");
+    expect(finalized?.cfg?.channels?.signal?.accountUuid).toBe(accountUuid);
+  });
+
   it("rejects an existing-server recovery account owned by a sibling", async () => {
     mocks.probeSignalTransport.mockResolvedValueOnce({
       ok: false,
diff --git a/extensions/signal/src/setup-interactive.ts b/extensions/signal/src/setup-interactive.ts
index 7157dcc00343..d1b4e9e6b6f8 100644
--- a/extensions/signal/src/setup-interactive.ts
+++ b/extensions/signal/src/setup-interactive.ts
@@ -15,6 +15,7 @@ import {
 } from "./accounts.js";
 import {
   assertSignalAccountNotAssignedToSibling,
+  isSameSignalAccount,
   normalizeSignalAccountInput,
   signalSetupStateKeys,
 } from "./setup-core.js";
@@ -67,7 +68,15 @@ export async function finalizeSignalExistingServerSetup(params: SignalFinalizePa
         cfg,
         channel: "signal",
         accountId: params.accountId,
-        patch: { account, accountUuid: undefined },
+        patch: {
+          account,
+          ...(isSameSignalAccount(
+            resolveSignalAccount({ cfg, accountId: params.accountId }).config.account,
+            account,
+          )
+            ? {}
+            : { accountUuid: undefined }),
+        },
       });
       shouldPromptAccount = false;
     }