diff --git a/.github/workflows/semgrep.yml b/.github/workflows/semgrep.yml
new file mode 100644
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+++ b/.github/workflows/semgrep.yml
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+# Semgrep: run only custom rules (.semgrep/rules) – no registry/auto rules.
+# Fast, no timeouts from heavy JS/Python registry rules on large files.
+name: Semgrep (custom rules only)
+
+on:
+  pull_request:
+    branches: [main]
+  push:
+    branches: [main]
+
+jobs:
+  semgrep:
+    runs-on: ubuntu-latest
+    timeout-minutes: 10
+
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Set up Python
+        uses: actions/setup-python@v4
+        with:
+          python-version: "3.12"
+
+      - name: Install Semgrep
+        run: pip install semgrep
+
+      - name: Run Semgrep (custom rules only)
+        run: semgrep scan --config .semgrep/rules . --error
diff --git a/.semgrep/rules/README.md b/.semgrep/rules/README.md
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+++ b/.semgrep/rules/README.md
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+# Custom Semgrep rules for LiteLLM
+
+Add custom rule YAML files here. Semgrep loads all `.yml`/`.yaml` files under this directory.
+
+**Run only custom rules (CI / fail on findings):**
+
+```bash
+semgrep scan --config .semgrep/rules . --error
+```
+
+**Run with registry + custom rules:**
+
+```bash
+semgrep scan --config auto --config .semgrep/rules .
+```
+
+**Layout:**
+
+- `python/` – Python-specific rules (security, patterns)
+- Add more subdirs as needed (e.g. `generic/` for language-agnostic rules)
+
+See [Semgrep rule syntax](https://semgrep.dev/docs/writing-rules/rule-syntax/).
diff --git a/.semgrep/rules/python/unbounded-memory.yml b/.semgrep/rules/python/unbounded-memory.yml
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+++ b/.semgrep/rules/python/unbounded-memory.yml
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+# Unbounded memory growth – data structures without a clear max limit
+# Can lead to OOM under load or with unbounded input.
+
+rules:
+  # asyncio.Queue() with no maxsize is unbounded – bad pattern for integrations (log queues, etc.)
+  - id: unbounded-asyncio-queue
+    message: asyncio.Queue() with no maxsize can grow unbounded. Use asyncio.Queue(maxsize=N) for integrations (e.g. log queues).
+    severity: WARNING
+    languages: [python]
+    pattern-either:
+      - pattern: asyncio.Queue()
+      - pattern: asyncio.Queue(maxsize=0)
+    metadata:
+      category: correctness
+      cwe: "CWE-400: Uncontrolled Resource Consumption"