diff --git a/action.yml b/action.yml
index b621142..0f02c2c 100644
--- a/action.yml
+++ b/action.yml
@@ -20,6 +20,11 @@ inputs:
   bot-token:
     description: API key or token for the selected bot
     required: false
+  model:
+    description: >-
+      Model for the selected bot. Defaults to `claude-sonnet-5` or
+      `gpt-5.6-terra`, the mid tiers, which cover reviews and fixes.
+    required: false
 
 runs:
   using: composite
@@ -40,6 +45,7 @@ runs:
         ACTION_PATH: ${{ gitea.action_path }}
         BOT_TYPE: ${{ inputs.bot-type }}
         BOT_TOKEN: ${{ inputs.bot-token }}
+        MODEL: ${{ inputs.model }}
         GITEA_API_URL: ${{ gitea.api_url }}
         GITEA_REPOSITORY: ${{ gitea.repository }}
         GITEA_TOKEN: ${{ inputs.author-token }}
diff --git a/run.ts b/run.ts
index 0850f86..21c358c 100644
--- a/run.ts
+++ b/run.ts
@@ -20,6 +20,13 @@ const EVENT = env("EVENT_NAME");
 const AUTHOR_TOKEN = env("GITEA_TOKEN");
 const REVIEWER_TOKEN = env("REVIEWER_TOKEN");
 const RULES_PATH = "repos/commons/code-rules/raw/README.md";
+// The mid tiers: a run follows a fixed template and the project's checks.
+const DEFAULT_MODELS: Record<string, string> = {
+  claude: "claude-sonnet-5",
+  codex: "gpt-5.6-terra",
+};
+const model = (bot: string): string =>
+  Deno.env.get("MODEL") || DEFAULT_MODELS[bot];
 
 // The reviewer token is withheld so the agent cannot approve as the bot.
 const { REVIEWER_TOKEN: _, ...agentEnv } = Deno.env.toObject();
@@ -134,7 +141,7 @@ async function runClaude(prompt: string): Promise<string> {
       "--print",
       "--dangerously-skip-permissions",
       "--model",
-      "claude-fable-5",
+      model("claude"),
       "--output-format",
       "stream-json",
       "--verbose",
@@ -199,7 +206,7 @@ async function runCodex(prompt: string): Promise<string> {
     args: [
       "exec",
       "--model",
-      "gpt-5.5",
+      model("codex"),
       "--dangerously-bypass-approvals-and-sandbox",
       "--output-last-message",
       file,