diff --git a/desktop/playwright.config.ts b/desktop/playwright.config.ts
index 446f3ecd40..2659a747ee 100644
--- a/desktop/playwright.config.ts
+++ b/desktop/playwright.config.ts
@@ -39,6 +39,7 @@ export default defineConfig({
         "**/activity-scope-label-screenshots.spec.ts",
         "**/local-archive-screenshots.spec.ts",
         "**/agent-readiness-screenshots.spec.ts",
+        "**/edit-agent.spec.ts",
         "**/pubkey-display-screenshots.spec.ts",
         "**/file-attachment.spec.ts",
         "**/image-attachment-gallery.spec.ts",
diff --git a/desktop/tests/e2e/edit-agent.spec.ts b/desktop/tests/e2e/edit-agent.spec.ts
new file mode 100644
index 0000000000..28a5b8a579
--- /dev/null
+++ b/desktop/tests/e2e/edit-agent.spec.ts
@@ -0,0 +1,201 @@
+import { expect, test } from "@playwright/test";
+
+import { installMockBridge, TEST_IDENTITIES } from "../helpers/bridge";
+
+// Edit-agent dialog coverage (Phase 1B.3b-pre). Written against TODAY'S
+// EditAgentDialog, before the B3b re-host, so the re-host is guarded by a
+// pre-existing spec rather than one written alongside it.
+//
+// Mock-boundary caveat: the e2eBridge `update_managed_agent` handler echoes
+// name/model/systemPrompt/envVars/respondTo/respondToAllowlist into the
+// mock store — it does NOT
+// model the diff-based partial-update wire semantics (change-detected-or-omit,
+// tri-state provider, harnessOverride derivation), and it ignores
+// agentCommand/harnessOverride entirely. This spec therefore pins UI behavior
+// (open → edit → save → persisted in UI), not wire semantics. The inherit
+// toggle is not reachable here at all (see the routing pin below) — its
+// behavior is covered by B3b's component-level pinning test (inherit-toggle
+// → gate → submit); wire semantics stay component-test territory
+// (personaRuntimeModel.test.mjs).
+
+// Tyler's pubkey maps to gooseSurface in the mock bridge (runtimeId "goose"),
+// which supports LLM provider selection — same seed the readiness-screenshot
+// spec uses for its edit-dialog shot.
+const AGENT_PUBKEY = TEST_IDENTITIES.tyler.pubkey;
+const AGENT_NAME = "Tyler Agent";
+const PERSONA_ID = "persona-edit-e2e";
+
+/**
+ * Open the Edit Agent dialog for the seeded managed agent via the profile
+ * panel (agents view → agent card → Edit quick action) — EditAgentDialog's
+ * only mount path.
+ */
+async function openEditDialog(page: import("@playwright/test").Page) {
+  await page.goto("/");
+  await page.getByTestId("open-agents-view").click();
+
+  const agentButton = page.getByRole("button", {
+    name: `${AGENT_NAME} agent profile`,
+  });
+  await expect(agentButton).toBeVisible({ timeout: 10_000 });
+  await agentButton.click();
+
+  await expect(page.getByTestId("user-profile-panel")).toBeVisible({
+    timeout: 10_000,
+  });
+  await page.getByTestId("user-profile-edit-agent").click();
+
+  await expect(page.getByTestId("edit-agent-dialog")).toBeVisible({
+    timeout: 10_000,
+  });
+  // Provider field visible = runtime catalog loaded and form settled.
+  await expect(page.locator("#edit-agent-llm-provider")).toBeVisible({
+    timeout: 10_000,
+  });
+}
+
+/**
+ * Pick an option from a PersonaDropdownField (menu-based, not a native
+ * <select> — Create's fields are selects, Edit's are not).
+ */
+async function pickDropdownOption(
+  page: import("@playwright/test").Page,
+  triggerId: string,
+  optionName: string | RegExp,
+) {
+  await page.locator(`#${triggerId}`).click();
+  await page.getByRole("menuitemradio", { name: optionName }).click();
+}
+
+test.describe("edit agent dialog", () => {
+  test("edits the agent name and persists it across a dialog reopen", async ({
+    page,
+  }) => {
+    await installMockBridge(page, {
+      managedAgents: [
+        {
+          pubkey: AGENT_PUBKEY,
+          name: AGENT_NAME,
+          status: "stopped",
+          channelNames: ["agents"],
+        },
+      ],
+    });
+
+    await openEditDialog(page);
+
+    const nameInput = page.locator("#edit-agent-name");
+    await expect(nameInput).toHaveValue(AGENT_NAME);
+    await nameInput.fill("Tyler Agent Renamed");
+
+    await page.getByTestId("edit-agent-dialog-submit").click();
+    await expect(page.getByTestId("edit-agent-dialog")).not.toBeVisible();
+
+    // Reopen: the dialog re-reads the managed-agents store, proving the save
+    // survived the dialog lifecycle rather than living in local state. (The
+    // panel HEADER is not asserted — it renders the relay profile name, which
+    // the update path does not touch.)
+    await page.getByTestId("user-profile-edit-agent").click();
+    await expect(page.locator("#edit-agent-name")).toHaveValue(
+      "Tyler Agent Renamed",
+      { timeout: 10_000 },
+    );
+  });
+
+  test("changes the model via custom entry and persists it", async ({
+    page,
+  }) => {
+    await installMockBridge(page, {
+      managedAgents: [
+        {
+          pubkey: AGENT_PUBKEY,
+          name: AGENT_NAME,
+          status: "stopped",
+          channelNames: ["agents"],
+        },
+      ],
+    });
+
+    await openEditDialog(page);
+
+    // Pick a provider so model discovery has a scope, then set a custom model.
+    await pickDropdownOption(page, "edit-agent-llm-provider", "Anthropic");
+    await pickDropdownOption(page, "edit-agent-model", "Custom model...");
+    await page.locator("#edit-agent-custom-model").fill("claude-opus-4-5");
+    // Anthropic requires a credential before save unlocks.
+    await page
+      .getByTestId("env-vars-required-value")
+      .fill("sk-test-edit-agent-e2e");
+
+    const submit = page.getByTestId("edit-agent-dialog-submit");
+    await expect(submit).toBeEnabled({ timeout: 10_000 });
+    await submit.click();
+    await expect(page.getByTestId("edit-agent-dialog")).not.toBeVisible();
+
+    await page.getByTestId("user-profile-edit-agent").click();
+    await expect(page.getByTestId("edit-agent-dialog")).toBeVisible({
+      timeout: 10_000,
+    });
+    // Custom model round-trips: the reopened dialog shows it in the custom
+    // input (the discovered-model lists don't contain it).
+    await expect(page.locator("#edit-agent-custom-model")).toHaveValue(
+      "claude-opus-4-5",
+      { timeout: 10_000 },
+    );
+  });
+
+  test("profile Edit routes persona-linked agents to the definition editor", async ({
+    page,
+  }) => {
+    // Routing pin for handleEditAgent (UserProfilePanel): when the agent has
+    // a resolvable non-built-in persona, the Edit quick action opens the
+    // DEFINITION editor (persona dialog), not EditAgentDialog. The instance
+    // editor (and its inherit-runtime toggle) is reachable for persona-linked
+    // agents only via the requestOpenEditAgent event (ConfigNudgeCard) — no
+    // plain UI path — so its inherit-toggle behavior is covered by B3b's
+    // component-level pinning test, not e2e.
+    await installMockBridge(page, {
+      managedAgents: [
+        {
+          pubkey: AGENT_PUBKEY,
+          name: AGENT_NAME,
+          personaId: PERSONA_ID,
+          status: "stopped",
+          channelNames: ["agents"],
+        },
+      ],
+      personas: [
+        {
+          id: PERSONA_ID,
+          displayName: "Edit E2E Persona",
+          systemPrompt: "You are the edit-agent e2e persona.",
+        },
+      ],
+    });
+
+    await page.goto("/");
+    await page.getByTestId("open-agents-view").click();
+
+    // Persona-linked agents render grouped under the persona's card name.
+    const agentButton = page.getByRole("button", {
+      name: "Edit E2E Persona agent profile",
+    });
+    await expect(agentButton).toBeVisible({ timeout: 10_000 });
+    await agentButton.click();
+
+    await expect(page.getByTestId("user-profile-panel")).toBeVisible({
+      timeout: 10_000,
+    });
+    await page.getByTestId("user-profile-edit-agent").click();
+
+    // Definition editor opens; the instance editor does not.
+    await expect(page.getByTestId("persona-dialog")).toBeVisible({
+      timeout: 10_000,
+    });
+    await expect(page.getByTestId("edit-agent-dialog")).not.toBeVisible();
+    // And it is the persona's record that's being edited.
+    await expect(page.locator("#persona-display-name")).toHaveValue(
+      "Edit E2E Persona",
+    );
+  });
+});