# Pin the model agents run — plan on one, execute on another > Force a specific model for agent runs and split plan mode from execution: ingress allowlist + catch-all model mapping + plan-mode script switch, so developers can't route simple tasks to Opus. Canonical: https://www.gatellm.io/use-cases/enforce-model-policy/ Neutralize client-side model choice, then split plan mode from execution so a strong model plans and a cheap model executes. ## What the community actually complains about "Our devs flip Claude Code to Opus to summarize a changelog," "everyone has a different model in their settings and we can't see who spent what," "we tried a client-side policy, but anyone can just edit it back." Model choice is a cost decision, not a developer preference — it has to be enforced at the gateway, where the request actually lands. ## How GateLLM does it Three layers, none skippable: the key group's models allowlist (ingress gate) rejects unauthorized model names with 403; a catch-all model mapping from "*" rewrites whatever the client requests to the sanctioned model; and a before-slot script keeps plan mode on the strong model and switches to the execution model on exit. Bypass requests — like Claude Code's conversation-title generation — carry no plan marker, so they fall through to the cheap execution model. That is exactly the "don't run Opus on a summary" behavior you wanted. ## 5 levers that actually land - Ingress gate: the key group's models allowlist rejects any unauthorized model name before routing - Catch-all mapping: from "*" → to the sanctioned model normalizes every requested name to one model - Plan/exec split: a before-slot script reads the plan-mode markers and switches routing only after exiting plan - Observable: switched requests get an SW tag in the logs, so every request's real landing model is auditable - Hot-reload: mappings and rules take effect immediately — no restart, no per-developer rollout ## FAQ ### Why not use a declarative switch-route rule for plan mode? switch-route predicates only do structural existence and small-value equality — they never read the content of a string value, which is what keeps large bodies on disk. The plan-mode marker lives in the message text, so it needs the before-slot script; structural checks (image → vision model) are where switch-route shines. ### Can a client still pick Opus by editing its own settings? No. The ingress gate 403s any model name outside the allowlist, and the catch-all mapping normalizes whatever remains to the sanctioned model. Model choice stops being a client decision the moment the request reaches the gateway. ### The script seems to have no effect and logs show no error? Each script runs in its own QuickJS sandbox with a 64MB heap cap (SCRIPT_MEMORY_LIMIT_MB). On out-of-memory the default log-and-continue mode silently drops all side effects — including useModel — so the routing just doesn't switch. Claude Code's tool definitions consume memory first; raise the limit (a restart is required). - [Full how-to: plan-mode model switch (docs)](https://docs.gatellm.io/en/howto/script-switch-model-by-plan-mode) ## Related use cases - [No model choice on the client: the gateway tiers automatically](https://www.gatellm.io/use-cases/automatic-model-tiering.md) ## Related - [Home](https://www.gatellm.io/index.md) - [Pricing](https://www.gatellm.io/pricing.md) - [Cost Calculator](https://www.gatellm.io/calculator.md) - [About](https://www.gatellm.io/about.md) - [Book a Demo](https://www.gatellm.io/demo.md) - [FAQ](https://www.gatellm.io/faq.md) - [Compare AI Gateways](https://www.gatellm.io/compare.md) - [Compare LiteLLM](https://www.gatellm.io/compare/litellm.md) - [Compare OpenRouter](https://www.gatellm.io/compare/openrouter.md) - [Compare Alibaba Cloud AI Gateway](https://www.gatellm.io/compare/alibaba-cloud.md) - [Compare Azure API Management](https://www.gatellm.io/compare/azure-apim.md) - [Compare Apigee](https://www.gatellm.io/compare/apigee.md) - [Compare Cloudflare AI Gateway](https://www.gatellm.io/compare/cloudflare.md) - [Compare Kong AI Gateway](https://www.gatellm.io/compare/kong.md) - [Compare Portkey](https://www.gatellm.io/compare/portkey.md) - [LiteLLM vs Kong AI Gateway](https://www.gatellm.io/compare/litellm-vs-kong.md) - [LiteLLM vs OpenRouter](https://www.gatellm.io/compare/litellm-vs-openrouter.md) - [LiteLLM vs Portkey](https://www.gatellm.io/compare/litellm-vs-portkey.md) - [Use Cases](https://www.gatellm.io/use-cases.md) - [Reduce LLM Cost](https://www.gatellm.io/use-cases/reduce-cost.md) - [High Availability](https://www.gatellm.io/use-cases/high-availability.md) - [Multi-Tenant Isolation](https://www.gatellm.io/use-cases/multi-tenant.md) - [Compliance & Audit](https://www.gatellm.io/use-cases/compliance-audit.md) - [Troubleshooting by Symptom](https://www.gatellm.io/use-cases/troubleshooting.md) - [Mixed Multi-Vendor Model Stack](https://www.gatellm.io/use-cases/mixed-model-stack.md) - [Self-Host AI Inside Office](https://www.gatellm.io/use-cases/self-hosted-office-ai.md) - [Token Usage Visibility & Attribution](https://www.gatellm.io/use-cases/token-ops.md) - [Token FinOps: AI Cost Allocation & Control](https://www.gatellm.io/use-cases/token-finops.md) - [MCP Tool Governance](https://www.gatellm.io/use-cases/mcp-tool-governance.md) - [Web Search for Every Model](https://www.gatellm.io/use-cases/web-search-grounding.md) - [Multi-Key Rotation & Standby](https://www.gatellm.io/use-cases/multi-key-pooling.md) - [Admission Control for Connected Clients](https://www.gatellm.io/use-cases/client-admission-control.md) - [No Model Choice on the Client](https://www.gatellm.io/use-cases/automatic-model-tiering.md) - [One Protocol, Any Model](https://www.gatellm.io/use-cases/one-protocol-any-model.md) - [Office / Microsoft 365 Add-in](https://www.gatellm.io/office-addin.md) - [Glossary](https://www.gatellm.io/glossary.md) - [Model Catalog](https://www.gatellm.io/models.md) - [SDK & Framework Integrations](https://www.gatellm.io/integrations.md) - [AI Coding Agents & Harnesses](https://www.gatellm.io/coding-agents.md) - [Security & Compliance](https://www.gatellm.io/security.md) - [Privacy Policy](https://www.gatellm.io/privacy-policy.md) - [Terms of Service](https://www.gatellm.io/terms.md) - [Cookie Policy](https://www.gatellm.io/cookies.md) - [Data Processing Agreement (DPA)](https://www.gatellm.io/dpa.md) - [Sub-processor List](https://www.gatellm.io/subprocessors.md) - [Security Questionnaire (CAIQ/SIG/VSA)](https://www.gatellm.io/trust.md) - [Incident Response & Support](https://www.gatellm.io/sla.md) - [Vulnerability Disclosure Policy](https://www.gatellm.io/vulnerability-disclosure.md) - [Open Source License Notice](https://www.gatellm.io/open-source-licenses.md) - [Version Support & Lifecycle (EOL)](https://www.gatellm.io/lifecycle.md) - [Engineering Blog](https://www.gatellm.io/blog.md) - [Your Agents Have More Permissions Than Your Employees: Governing MCP Tools at the Gateway](https://www.gatellm.io/blog/mcp-tool-governance.md) - [The $10k Invoice Problem: Five Ways to Cut LLM Spend Without Dumbing Down Your App](https://www.gatellm.io/blog/reduce-cost.md) - [Your Vendor's List Price Is Not Your Cost: Applying Real FinOps to Token Spend](https://www.gatellm.io/blog/token-finops.md) - [llms.txt](https://www.gatellm.io/llms.txt)