diff --git a/.github/workflows/check-opencode-annotations.yml b/.github/workflows/check-opencode-annotations.yml
index 885fa7e458e..810371d6d3e 100644
--- a/.github/workflows/check-opencode-annotations.yml
+++ b/.github/workflows/check-opencode-annotations.yml
@@ -37,3 +37,8 @@ jobs:
           else
             echo "No PR base SHA available (workflow_dispatch without PR context) — skipping."
           fi
+
+      # kilocode_change start
+      - name: Check workflow allowlist
+        run: bun run script/check-workflows.ts
+      # kilocode_change end
diff --git a/AGENTS.md b/AGENTS.md
index 7285909eb25..cc5eda0d054 100644
--- a/AGENTS.md
+++ b/AGENTS.md
@@ -21,6 +21,7 @@ Kilo CLI is an open source AI coding agent that generates code from natural lang
 - **Source links**: After adding or changing URLs in `packages/kilo-vscode/`, `packages/kilo-vscode/webview-ui/`, or `packages/opencode/src/`, run `bun run script/extract-source-links.ts` from the repo root and commit the updated `packages/kilo-docs/source-links.md`. CI runs this check — the build fails if the file is stale.
 - **kilocode_change check**: `bun run check-kilocode-change` from `packages/kilo-vscode/`. CI runs this — `kilocode_change` is a marker for upstream merge conflicts and must not appear in `packages/kilo-vscode/` or `packages/kilo-ui/` (these are entirely Kilo Code additions). Remove the markers before pushing.
 - **opencode annotation check**: `bun run script/check-opencode-annotations.ts` from repo root. CI runs this on PRs touching `packages/opencode/` — every Kilo-specific change in shared opencode files must be annotated with `kilocode_change` markers. Exempt paths (no markers needed): `packages/opencode/src/kilocode/`, `packages/opencode/test/kilocode/`, and any path containing `kilocode` in the name.
+- **workflow allowlist**: `bun run script/check-workflows.ts` from repo root. CI runs this as part of the annotations workflow — any `.yml` / `.yaml` file added to or removed from `.github/workflows/` must be reflected in the hardcoded list in `script/check-workflows.ts`. Prevents upstream-merged workflows from silently starting to run in our CI.
 - **Backend/SDK programmatic testing**: see [TESTING.md](./TESTING.md) for spawning the local main-branch backend (`bun dev serve`) and driving it via `curl` — use this instead of `kilo serve` (prod binary) when testing backend fixes.
 
 ## Quality Checks
diff --git a/script/check-workflows.ts b/script/check-workflows.ts
new file mode 100644
index 00000000000..a7536cd0799
--- /dev/null
+++ b/script/check-workflows.ts
@@ -0,0 +1,81 @@
+#!/usr/bin/env bun
+// kilocode_change - new file
+
+/**
+ * Guards against accidentally inheriting workflows from upstream opencode.
+ *
+ * We regularly merge upstream. When upstream adds a new workflow under
+ * `.github/workflows/`, it silently starts running in our CI unless we
+ * explicitly review and accept it. This check makes that decision explicit:
+ * the list of allowed workflows is hardcoded below, and any drift (added or
+ * removed file in `.github/workflows/`) fails CI until the list is updated
+ * deliberately.
+ *
+ * Only runnable workflows are checked (`.yml` / `.yaml`). Files under
+ * `.github/workflows/disabled/` are Kilo-specific and can't run, so they're
+ * not tracked here.
+ *
+ * To accept a new workflow: add its filename to `active`.
+ * To drop one: remove its filename from the list.
+ */
+
+import { readdirSync } from "node:fs"
+import path from "node:path"
+
+const ROOT = path.resolve(import.meta.dir, "..")
+const DIR = path.join(ROOT, ".github", "workflows")
+
+// Workflows we have deliberately accepted into CI. Sort alphabetically.
+const active = new Set([
+  "auto-docs.yml",
+  "beta.yml",
+  "check-md-table-padding.yml",
+  "check-opencode-annotations.yml",
+  "check-org-member.yml",
+  "close-issues.yml",
+  "close-stale-prs.yml",
+  "containers.yml",
+  "docs-build.yml",
+  "docs-check-links.yml",
+  "duplicate-issues.yml",
+  "generate.yml",
+  "nix-eval.yml",
+  "nix-hashes.yml",
+  "publish.yml",
+  "smoke-test.yml",
+  "source-check-links.yml",
+  "test-vscode.yml",
+  "test.yml",
+  "triage.yml",
+  "typecheck.yml",
+  "visual-regression.yml",
+  "watch-opencode-releases.yml",
+])
+
+// GitHub picks up both .yml and .yaml in .github/workflows/. We accept both so
+// an upstream `.yaml` addition also shows up as unexpected drift.
+const isWorkflow = (f: string) => f.endsWith(".yml") || f.endsWith(".yaml")
+const actualActive = new Set(readdirSync(DIR).filter(isWorkflow))
+
+const missing = [...active].filter((f) => !actualActive.has(f)).sort()
+const extra = [...actualActive].filter((f) => !active.has(f)).sort()
+const errs: string[] = []
+for (const f of extra) {
+  errs.push(`unexpected workflow: ${f} — if this was added intentionally, add it to script/check-workflows.ts`)
+}
+for (const f of missing) {
+  errs.push(
+    `expected workflow not found: ${f} — if this was removed intentionally, remove it from script/check-workflows.ts`,
+  )
+}
+
+if (errs.length === 0) {
+  console.log(`check-workflows: ok (${actualActive.size} workflows).`)
+  process.exit(0)
+}
+
+for (const e of errs) console.error(e)
+console.error("")
+console.error(`Found ${errs.length} workflow drift issue(s).`)
+console.error("This guard prevents upstream-merged workflows from silently running in our CI.")
+process.exit(1)