diff --git a/.env.example b/.env.example
new file mode 100644
index 0000000..2475d48
--- /dev/null
+++ b/.env.example
@@ -0,0 +1,3 @@
+GITHUB_TOKEN=your_token
+OPENROUTER_API_KEY=your_key
+CFORGE_MAX_BUDGET=5
diff --git a/README.md b/README.md
index b280921..b8e21ad 100644
--- a/README.md
+++ b/README.md
@@ -50,6 +50,7 @@ npm install
 npm run build
 export GITHUB_TOKEN=your_token
 export OPENROUTER_API_KEY=your_key
+export CFORGE_MAX_BUDGET=5          # max USD per Claude Code session (default: 5)
 cforge-dev chat
 ```
 
diff --git a/src/infrastructure/claude/ClaudeCodeRunner.ts b/src/infrastructure/claude/ClaudeCodeRunner.ts
index c17fabb..3cf2010 100644
--- a/src/infrastructure/claude/ClaudeCodeRunner.ts
+++ b/src/infrastructure/claude/ClaudeCodeRunner.ts
@@ -2,7 +2,7 @@ import { execSync, spawn } from "child_process";
 import { CodeRunner, RunOptions, RunResult } from "../../domain/interfaces/CodeRunner";
 
 const DEFAULT_MODEL = "claude-sonnet-4-6";
-const DEFAULT_BUDGET = 1.0;
+const DEFAULT_BUDGET = 5;
 const DEFAULT_TOOLS = ["Bash", "Edit", "Read", "Write", "Glob", "Grep"];
 
 interface ClaudeJsonResponse {
@@ -18,7 +18,8 @@ interface ClaudeJsonResponse {
 export class ClaudeCodeRunner implements CodeRunner {
   async run(prompt: string, workingDir: string, options: RunOptions): Promise<RunResult> {
     const model = options.model ?? DEFAULT_MODEL;
-    const budget = options.maxBudgetUsd ?? DEFAULT_BUDGET;
+    const envBudget = process.env.CFORGE_MAX_BUDGET ? Number(process.env.CFORGE_MAX_BUDGET) : DEFAULT_BUDGET;
+    const budget = options.maxBudgetUsd ?? envBudget;
     const tools = options.allowedTools ?? DEFAULT_TOOLS;
 
     // Check if claude CLI exists
diff --git a/tests/infrastructure/ClaudeCodeRunner.test.ts b/tests/infrastructure/ClaudeCodeRunner.test.ts
index b19da1e..b9e6483 100644
--- a/tests/infrastructure/ClaudeCodeRunner.test.ts
+++ b/tests/infrastructure/ClaudeCodeRunner.test.ts
@@ -229,7 +229,7 @@ describe("ClaudeCodeRunner", () => {
     );
   });
 
-  it("should pass correct default flags", async () => {
+  it("should pass correct default flags with env-based budget", async () => {
     mockSpawnSuccess(successJson);
     const runner = new ClaudeCodeRunner();
     await runner.run("prompt", "/tmp/work", {});
@@ -241,12 +241,68 @@ describe("ClaudeCodeRunner", () => {
       "--model", "claude-sonnet-4-6",
       "--dangerously-skip-permissions",
       "--allowed-tools", "Bash,Edit,Read,Write,Glob,Grep",
-      "--max-budget-usd", "1",
+      "--max-budget-usd", "5",
       "--output-format", "json",
     ]);
     expect(opts.cwd).toBe("/tmp/work");
   });
 
+  it("should read CFORGE_MAX_BUDGET from env with default of 5", async () => {
+    mockSpawnSuccess(successJson);
+    const original = process.env.CFORGE_MAX_BUDGET;
+    try {
+      delete process.env.CFORGE_MAX_BUDGET;
+      const runner = new ClaudeCodeRunner();
+      await runner.run("prompt", "/tmp/test", {});
+
+      const args: string[] = (spawn as jest.Mock).mock.calls[0][1];
+      const idx = args.indexOf("--max-budget-usd");
+      expect(args[idx + 1]).toBe("5");
+    } finally {
+      if (original !== undefined) process.env.CFORGE_MAX_BUDGET = original;
+    }
+  });
+
+  it("should use CFORGE_MAX_BUDGET env var when set", async () => {
+    mockSpawnSuccess(successJson);
+    const original = process.env.CFORGE_MAX_BUDGET;
+    try {
+      process.env.CFORGE_MAX_BUDGET = "10";
+      const runner = new ClaudeCodeRunner();
+      await runner.run("prompt", "/tmp/test", {});
+
+      const args: string[] = (spawn as jest.Mock).mock.calls[0][1];
+      const idx = args.indexOf("--max-budget-usd");
+      expect(args[idx + 1]).toBe("10");
+    } finally {
+      if (original !== undefined) {
+        process.env.CFORGE_MAX_BUDGET = original;
+      } else {
+        delete process.env.CFORGE_MAX_BUDGET;
+      }
+    }
+  });
+
+  it("should let RunOptions.maxBudgetUsd override env var", async () => {
+    mockSpawnSuccess(successJson);
+    const original = process.env.CFORGE_MAX_BUDGET;
+    try {
+      process.env.CFORGE_MAX_BUDGET = "10";
+      const runner = new ClaudeCodeRunner();
+      await runner.run("prompt", "/tmp/test", { maxBudgetUsd: 20 });
+
+      const args: string[] = (spawn as jest.Mock).mock.calls[0][1];
+      const idx = args.indexOf("--max-budget-usd");
+      expect(args[idx + 1]).toBe("20");
+    } finally {
+      if (original !== undefined) {
+        process.env.CFORGE_MAX_BUDGET = original;
+      } else {
+        delete process.env.CFORGE_MAX_BUDGET;
+      }
+    }
+  });
+
   it("should respect custom model and budget options", async () => {
     mockSpawnSuccess(successJson);
     const runner = new ClaudeCodeRunner();