From 1e35159abdb6629308c58cca4dbd65785000675b Mon Sep 17 00:00:00 2001
From: Andrew Halberstadt <ahal@mozilla.com>
Date: Wed, 14 Oct 2026 14:57:16 -0400
Subject: [PATCH] fix(cached_tasks): add worker-type to digest

When a task runs on a different worker-type, the underlying environment
could be completely different. Or not.

It could be a simple instance type change that has no impact on the
task's artifact, or it could be a different OS, a different cloud
provider or even a different worker binary.

Therefore it's best to include the worker-type in the cached task
digest.
---
 src/taskgraph/transforms/cached_tasks.py |  5 +++
 test/test_transforms_cached_tasks.py     | 43 ++++++++++++++++++++++++
 2 files changed, 48 insertions(+)

diff --git a/src/taskgraph/transforms/cached_tasks.py b/src/taskgraph/transforms/cached_tasks.py
index d6668d06d..86d580e91 100644
--- a/src/taskgraph/transforms/cached_tasks.py
+++ b/src/taskgraph/transforms/cached_tasks.py
@@ -75,6 +75,11 @@ def cache_task(config, tasks):
         if task.get("worker", {}).get("chain-of-trust"):
             digest_data.append(str(task["worker"]["chain-of-trust"]))
 
+        # The worker type can affect the environment the task runs in (e.g
+        # platform or architecture), so it should influence the cache digest.
+        if task.get("worker-type"):
+            digest_data.append(task["worker-type"])
+
         add_optimization(
             config,
             task,
diff --git a/test/test_transforms_cached_tasks.py b/test/test_transforms_cached_tasks.py
index c69112a5b..3dcaa6c4b 100644
--- a/test/test_transforms_cached_tasks.py
+++ b/test/test_transforms_cached_tasks.py
@@ -105,6 +105,13 @@ def assert_chain_of_trust_influences_digest(tasks):
     assert digest_0 != digest_1
 
 
+def assert_worker_type_influences_digest(tasks):
+    assert len(tasks) == 3
+    tasks = sorted(tasks, key=lambda t: t["label"])  # no-wt, wt-a, wt-b
+    digests = [t["attributes"]["cached_task"]["digest"] for t in tasks]
+    assert len(set(digests)) == 3
+
+
 @pytest.mark.parametrize(
     "tasks, kind_config, deps",
     (
@@ -233,6 +240,42 @@ def assert_chain_of_trust_influences_digest(tasks):
             {},
             id="chain_of_trust_influences_digest",
         ),
+        pytest.param(
+            # tasks
+            [
+                {
+                    "cache": {
+                        "type": "cached-task.v2",
+                        "name": "cache-foo",
+                        "digest-data": ["abc"],
+                    },
+                    "label": "no-wt",
+                },
+                {
+                    "cache": {
+                        "type": "cached-task.v2",
+                        "name": "cache-foo",
+                        "digest-data": ["abc"],
+                    },
+                    "label": "wt-a",
+                    "worker-type": "a",
+                },
+                {
+                    "cache": {
+                        "type": "cached-task.v2",
+                        "name": "cache-foo",
+                        "digest-data": ["abc"],
+                    },
+                    "label": "wt-b",
+                    "worker-type": "b",
+                },
+            ],
+            # kind config
+            {},
+            # kind deps
+            {},
+            id="worker_type_influences_digest",
+        ),
     ),
 )
 def test_transforms(