diff --git a/packages/server/src/server/agent/providers/codex-app-server-agent.test.ts b/packages/server/src/server/agent/providers/codex-app-server-agent.test.ts
index f0a7feca14..d7868b5438 100644
--- a/packages/server/src/server/agent/providers/codex-app-server-agent.test.ts
+++ b/packages/server/src/server/agent/providers/codex-app-server-agent.test.ts
@@ -1,4 +1,4 @@
-import { describe, expect, test, vi } from "vitest";
+import { beforeEach, describe, expect, test, vi } from "vitest";
 import type { ChildProcessWithoutNullStreams } from "node:child_process";
 import { EventEmitter } from "node:events";
 import { type Dirent, existsSync, mkdirSync, readFileSync, rmSync, writeFileSync } from "node:fs";
@@ -100,6 +100,12 @@ import { createTestLogger } from "../../../test-utils/test-logger.js";
 import { asInternals as castInternals, createStub } from "../../test-utils/class-mocks.js";
 import { AgentManager } from "../agent-manager.js";
 import { buildProviderRegistry } from "../provider-registry.js";
+import { sessionTurnIds } from "./test-utils/turn-ids.js";
+
+let codexTurnId = sessionTurnIds("codex");
+beforeEach(() => {
+  codexTurnId = sessionTurnIds("codex");
+});
 
 interface CollaborationModeRecord {
   name: string;
@@ -4634,7 +4640,7 @@ describe("Codex app-server provider", () => {
       await expect(child).resolves.toMatchObject({
         type: "provider_subagent",
         provider: "codex",
-        turnId: expect.stringMatching(/^codex-turn-[0-9a-f]+-0$/),
+        turnId: codexTurnId(0),
         event: {
           type: "upsert",
           id: "legacy-only-child-thread",
@@ -4644,7 +4650,7 @@ describe("Codex app-server provider", () => {
       await expect(spawn).resolves.toMatchObject({
         type: "timeline",
         provider: "codex",
-        turnId: expect.stringMatching(/^codex-turn-[0-9a-f]+-0$/),
+        turnId: codexTurnId(0),
         item: {
           type: "tool_call",
           callId: "spawn-legacy-only-child",
diff --git a/packages/server/src/server/agent/providers/opencode-agent.test.ts b/packages/server/src/server/agent/providers/opencode-agent.test.ts
index 7bb6055761..6bf4b77e2e 100644
--- a/packages/server/src/server/agent/providers/opencode-agent.test.ts
+++ b/packages/server/src/server/agent/providers/opencode-agent.test.ts
@@ -1,4 +1,4 @@
-import { describe, expect, test, vi } from "vitest";
+import { beforeEach, describe, expect, test, vi } from "vitest";
 import { mkdtempSync, realpathSync, rmSync, writeFileSync } from "node:fs";
 import os from "node:os";
 import path from "node:path";
@@ -25,6 +25,7 @@ import type {
   AssistantMessageTimelineItem,
   AgentTimelineItem,
 } from "../agent-sdk-types.js";
+import { sessionTurnIds } from "./test-utils/turn-ids.js";
 
 // Deliberately an independent literal rather than the production constant these tests
 // guard: deriving the boundary from OPENCODE_SERVER_STARTUP_TIMEOUT_MS would keep the
@@ -32,14 +33,10 @@ import type {
 const EXPECTED_STARTUP_BUDGET_MS = 30_000;
 const EXPECTED_EVENT_READINESS_BUDGET_MS = 45_000;
 
-/** Matches the ordinal of an OpenCode turn id; the instance nonce in the middle is random. */
-function openCodeTurnId(ordinal: number) {
-  return expect.stringMatching(new RegExp(`^opencode-turn-[0-9a-f]+-${ordinal}$`));
-}
-
-function isOpenCodeTurn(turnId: string | undefined, ordinal: number): boolean {
-  return new RegExp(`^opencode-turn-[0-9a-f]+-${ordinal}$`).test(turnId ?? "");
-}
+let openCodeTurnId = sessionTurnIds("opencode");
+beforeEach(() => {
+  openCodeTurnId = sessionTurnIds("opencode");
+});
 
 function tmpCwd(): string {
   const dir = mkdtempSync(path.join(os.tmpdir(), "opencode-agent-test-"));
@@ -2896,7 +2893,8 @@ describe("OpenCode adapter startTurn error handling", () => {
         }),
       );
       const autonomousCompletion = events.find(
-        (event) => event.type === "turn_completed" && isOpenCodeTurn(event.turnId, 1),
+        (event) =>
+          event.type === "turn_completed" && openCodeTurnId(1).asymmetricMatch(event.turnId),
       );
       expect(autonomousCompletion?.type).toBe("turn_completed");
       if (autonomousCompletion?.type === "turn_completed") {
diff --git a/packages/server/src/server/agent/providers/test-utils/turn-ids.ts b/packages/server/src/server/agent/providers/test-utils/turn-ids.ts
new file mode 100644
index 0000000000..c9e5e35cc1
--- /dev/null
+++ b/packages/server/src/server/agent/providers/test-utils/turn-ids.ts
@@ -0,0 +1,30 @@
+/** A Vitest asymmetric matcher for one provider turn id. */
+export interface TurnIdMatcher {
+  asymmetricMatch(actual: unknown): boolean;
+  toString(): string;
+  toAsymmetricMatcher(): string;
+}
+
+/**
+ * Matches the turn ids one provider session issues. Each session mixes a random nonce into its
+ * ids, so the first id seen binds that nonce and every later match must be the exact id
+ * `<owner>-turn-<nonce>-<ordinal>`. Two events of one turn therefore match only when their ids
+ * are identical. Create one per test.
+ */
+export function sessionTurnIds(owner: string): (ordinal: number) => TurnIdMatcher {
+  let nonce: string | null = null;
+  const pattern = new RegExp(`^${owner}-turn-([0-9a-f]+)-(\\d+)$`);
+  return (ordinal) => {
+    const describe = () => `${owner}-turn-${nonce ?? "<nonce>"}-${ordinal}`;
+    return {
+      asymmetricMatch(actual) {
+        const match = typeof actual === "string" ? pattern.exec(actual) : null;
+        if (!match || Number(match[2]) !== ordinal) return false;
+        nonce ??= match[1]!;
+        return match[1] === nonce;
+      },
+      toString: describe,
+      toAsymmetricMatcher: describe,
+    };
+  };
+}