diff --git a/.opencode/agents/architecture-pool-supervisor.md b/.opencode/agents/architecture-pool-supervisor.md
index 5e599737b..4b6160664 100644
--- a/.opencode/agents/architecture-pool-supervisor.md
+++ b/.opencode/agents/architecture-pool-supervisor.md
@@ -398,9 +398,15 @@ When making major changes to an existing spec:
    - Body: comprehensive description of every architectural change, the
      rationale, alternatives considered, and any open questions.
 4. Add the label **`needs feedback`** to the PR.
-5. **Do NOT merge this PR.** A human must review and merge it.
-6. Post a comment on the session state issue noting the PR.
-7. Return the PR number so the product-builder can monitor it and continue
+5. **Assign the PR to the current active milestone** using `forgejo_update_pull_request`:
+   - Query the current active milestone via `forgejo_list_repo_milestones` (state=open)
+   - Select the earliest open milestone that this spec change addresses
+   - Call `forgejo_update_pull_request` with `milestone=<milestone_id>`
+   - If no clear milestone applies, skip this step rather than guessing
+   - This ensures spec PRs are traceable to the milestone they support
+6. **Do NOT merge this PR.** A human must review and merge it.
+7. Post a comment on the session state issue noting the PR.
+8. Return the PR number so the product-builder can monitor it and continue
    other work while waiting for human approval.
 
 The system does NOT block on spec PR approval. It continues implementing
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 7a76a7292..874b6c89e 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -77,6 +77,10 @@ The format follows [Keep a Changelog](https://keepachangelog.com/en/1.1.0/).
 
 ### Changed
 
+- **Architecture Agent Milestone Assignment** (#7521): The `architecture-pool-supervisor` now
+  assigns spec PRs to the current active milestone via `forgejo_update_pull_request` after
+  PR creation, eliminating persistent watchdog alerts about PRs missing milestone assignments.
+
 - **Decision Tree Full ULID Display** (#5825): The `agents plan tree` command now
   displays full 26-character ULIDs for all decisions instead of truncating them to
   8 characters. This enables users to copy decision IDs directly from tree output
diff --git a/test_write.txt b/test_write.txt
new file mode 100644
index 000000000..9daeafb98
--- /dev/null
+++ b/test_write.txt
@@ -0,0 +1 @@
+test