diff --git a/.changeset/goal-tick-provider-env.md b/.changeset/goal-tick-provider-env.md
new file mode 100644
index 000000000..681c6129e
--- /dev/null
+++ b/.changeset/goal-tick-provider-env.md
@@ -0,0 +1,11 @@
+---
+id: goal-tick-provider-env
+tasks: [T13884]
+kind: feat
+summary: the Stop dispatcher passes CLEO_HOOK_PROVIDER (claude-code or codex) to the goal tick
+---
+
+`cleo hook stop --provider <p>` now spawns the goal tick with
+`CLEO_HOOK_PROVIDER=<p>` added to the inherited environment, so `cleo-goal tick`
+can tell which harness's Stop it is answering. The name is exported as
+`GOAL_TICK_PROVIDER_ENV` from `@cleocode/contracts/goal-runtime.js`.
diff --git a/packages/cleo/src/cli/__tests__/stop-dispatch-entry.test.ts b/packages/cleo/src/cli/__tests__/stop-dispatch-entry.test.ts
index 4a650d028..60d59fbf3 100644
--- a/packages/cleo/src/cli/__tests__/stop-dispatch-entry.test.ts
+++ b/packages/cleo/src/cli/__tests__/stop-dispatch-entry.test.ts
@@ -7,6 +7,7 @@
  * @task T13796
  */
 
+import { GOAL_TICK_PROVIDER_ENV } from '@cleocode/contracts/goal-runtime.js';
 import { describe, expect, it, vi } from 'vitest';
 import {
   askEnforceOptedOut,
@@ -216,6 +217,15 @@ describe('stopDispatch (T13796)', () => {
     expect(r.stdout).not.toContain('pwned');
   });
 
+  it('the tick child sees CLEO_HOOK_PROVIDER set to the dispatching harness (T13884)', async () => {
+    const echo = `node -e "process.stdout.write(JSON.stringify({p: process.env.${GOAL_TICK_PROVIDER_ENV}, h: process.env.HOME ?? null}))"`;
+    for (const provider of ['claude-code', 'codex'] as const) {
+      const run = await runTickKillable(echo, STOP, 5000, provider);
+      expect(run.status).toBe(0);
+      expect(JSON.parse(run.stdout)).toEqual({ p: provider, h: process.env.HOME ?? null });
+    }
+  });
+
   it('a tick that traps SIGTERM is SIGKILLed with its group at the deadline, and fails open', async () => {
     const marker = `cleo-t13796-${process.pid}-${Date.now()}`;
     const trap = `node -e "process.on('SIGTERM',()=>{});setInterval(()=>{},1000)" ${marker}-trap`;
diff --git a/packages/cleo/src/cli/stop-dispatch-entry.ts b/packages/cleo/src/cli/stop-dispatch-entry.ts
index 9e8c0d6a0..19eb843f6 100644
--- a/packages/cleo/src/cli/stop-dispatch-entry.ts
+++ b/packages/cleo/src/cli/stop-dispatch-entry.ts
@@ -43,6 +43,7 @@ import { spawn, spawnSync } from 'node:child_process';
 import { existsSync } from 'node:fs';
 import { dirname, join, resolve } from 'node:path';
 import type { HookJsonValue } from '@cleocode/contracts';
+import { GOAL_TICK_PROVIDER_ENV } from '@cleocode/contracts/goal-runtime.js';
 
 /** Harnesses `cleo hook stop` dispatches for. */
 export const STOP_DISPATCH_PROVIDERS = ['claude-code', 'codex'] as const;
@@ -231,7 +232,7 @@ export function processStopDispatchDeps(
       return goalTickCommand({ ...process.env, ...env });
     },
     hasGoalWorkspace: (input) => hasGoalWorkspace(input, env),
-    runTick: runTickKillable,
+    runTick: (command, input, timeoutMs) => runTickKillable(command, input, timeoutMs, provider),
     endSession: () => {
       const cli = process.argv[1];
       spawnSync(
@@ -285,12 +286,15 @@ export function hasGoalWorkspace(
  * @param command - The tick command line.
  * @param input - The Stop JSON for its stdin.
  * @param timeoutMs - Deadline.
+ * @param provider - The harness whose Stop this is, passed to the tick as
+ *   {@link GOAL_TICK_PROVIDER_ENV}; the rest of the environment is inherited.
  * @returns What the tick did.
  */
 export function runTickKillable(
   command: string,
   input: string,
   timeoutMs: number,
+  provider?: StopDispatchProvider,
 ): Promise<TickRun> {
   return new Promise((done) => {
     let stdout = '';
@@ -305,6 +309,9 @@ export function runTickKillable(
       shell: true,
       detached: true,
       stdio: ['pipe', 'pipe', 'ignore'],
+      ...(provider === undefined
+        ? {}
+        : { env: { ...process.env, [GOAL_TICK_PROVIDER_ENV]: provider } }),
     });
     const timer = setTimeout(() => {
       try {
diff --git a/packages/contracts/src/goal-runtime.ts b/packages/contracts/src/goal-runtime.ts
index 13161ed2a..da565e084 100644
--- a/packages/contracts/src/goal-runtime.ts
+++ b/packages/contracts/src/goal-runtime.ts
@@ -9,6 +9,13 @@
  * @epic T13791
  */
 
+/**
+ * Environment variable naming the harness whose Stop the dispatcher is
+ * answering (`claude-code` or `codex`), set on the `cleo-goal tick` child so
+ * the tick can tell harnesses apart (T13884).
+ */
+export const GOAL_TICK_PROVIDER_ENV = 'CLEO_HOOK_PROVIDER';
+
 /** The only `schemaVersion` this CLEO understands for every shape below. */
 export const GOAL_RUNTIME_SCHEMA_VERSION = 1;