diff --git a/CHANGELOG.md b/CHANGELOG.md
index a314b10..811daec 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,8 @@
 ## [Unreleased]
 
+### Security
+- The CLI no longer steers the OpenAI key into `.agentic.yml`: `agentic config set` refuses keys containing token, key, secret, passw, or credential in any spelling, and values shaped like an OpenAI key, and the missing-token error and README point at `OPENAI_ACCESS_TOKEN` / `Agentic.configure`, which are the paths that actually work. Nothing ever read `api_token` from that file, and it is not gitignored.
+
 ### Fixed
 - Test suite loads on Ruby 4.0: `benchmark` is a bundled (not default) gem there, so it is now declared in the Gemfile
 - `EventDispatcher` slow-observer spec uses a monotonic clock and a looser bound so it no longer flakes on loaded hosts
diff --git a/README.md b/README.md
index e80ec88..caaaed7 100644
--- a/README.md
+++ b/README.md
@@ -51,8 +51,7 @@ $ agentic config init                               # Initialize configuration
 $ agentic config init --global                      # Initialize global configuration
 $ agentic config list                               # List all configuration settings
 $ agentic config get model                          # Get a specific configuration value
-$ agentic config set api_token=your_openai_api_key  # Set your OpenAI API token
-$ agentic config set model=gpt-4o-mini             # Configure the default model
+$ agentic config set model=gpt-4o-mini              # Configure the default model
 
 # Plan Creation and Execution
 $ agentic plan "Generate a market research report on AI trends"          # Create a plan
@@ -729,20 +728,17 @@ You can configure the OpenAI API key in several ways:
    export OPENAI_ACCESS_TOKEN="your_api_key"
    ```
 
-2. Configuration file:
-   Create `.agentic.yml` in your project directory or home directory:
-   ```yaml
-   api_token: "your_api_key"
-   model: "gpt-4o-mini"
-   ```
-
-3. In your Ruby code:
+2. In your Ruby code:
    ```ruby
    Agentic.configure do |config|
      config.access_token = "your_api_key"
    end
    ```
 
+Keep the key out of `.agentic.yml`: that file holds non-secret settings such
+as `model`, is written in plain text to your project directory, and is not read
+for credentials. `agentic config set` refuses keys that look like secrets.
+
 ### LLM Configuration
 
 You can customize the LLM behavior:
diff --git a/lib/agentic/cli.rb b/lib/agentic/cli.rb
index db18da2..01f1112 100644
--- a/lib/agentic/cli.rb
+++ b/lib/agentic/cli.rb
@@ -468,6 +468,15 @@ def get(key)
         end
       end
 
+      # Keys that look like credentials (api_token, apiKey, api-key, client_secret,
+      # db_password, credentials) and values shaped like an OpenAI key.
+      # .agentic.yml is plain text, is not gitignored, and nothing reads a
+      # token out of it, so storing one there is a leak with no payoff. The
+      # key check is a substring match on purpose: a false positive costs a
+      # rename, a false negative costs a secret
+      CREDENTIAL_KEY = /token|key|secret|passw|credential/i
+      CREDENTIAL_VALUE = /\Ask-[A-Za-z0-9_-]{16,}\z/
+
       desc "set KEY=VALUE", "Set a configuration setting"
       option :global, type: :boolean, aliases: "-g",
         desc: "Set in global user config instead of project config"
@@ -479,6 +488,19 @@ def set(key_value)
           exit 1
         end
 
+        if key.match?(CREDENTIAL_KEY) || value.match?(CREDENTIAL_VALUE)
+          puts UI.box(
+            "Refusing to store a credential",
+            "'#{key}' looks like a secret, and #{CONFIG_FILE_NAME} is a plain-text file " \
+            "that nothing reads credentials from.\n\n" \
+            "Set OPENAI_ACCESS_TOKEN in the environment instead, or use\n" \
+            "Agentic.configure { |c| c.access_token = \"...\" } in code.",
+            padding: [1, 2, 1, 2],
+            style: {border: {fg: :red}}
+          )
+          exit 1
+        end
+
         path = options[:global] ? USER_CONFIG_PATH : PROJECT_CONFIG_PATH
         config = load_config(path) || {}
 
@@ -841,9 +863,9 @@ def check_api_token!
           "Configuration Error",
           "No OpenAI API token configured.\n\n" \
           "You can set it using one of these methods:\n" \
-          "- Environment variable: OPENAI_ACCESS_TOKEN\n" \
-          "- Configuration file: .agentic.yml\n" \
-          "- Run: agentic config set api_token=your_token",
+          "- Environment variable: OPENAI_ACCESS_TOKEN (or AGENTIC_API_TOKEN)\n" \
+          "- In code: Agentic.configure { |c| c.access_token = \"...\" }\n" \
+          "- Local endpoint: AGENTIC_API_BASE_URL, which needs no token",
           style: {border: {fg: :red}},
           padding: [1, 2, 1, 2]
         )
diff --git a/spec/agentic/cli/config_commands_spec.rb b/spec/agentic/cli/config_commands_spec.rb
index b89c026..3321b1e 100644
--- a/spec/agentic/cli/config_commands_spec.rb
+++ b/spec/agentic/cli/config_commands_spec.rb
@@ -99,11 +99,11 @@
     end
 
     it "sets a configuration value" do
-      config_commands.set("test_key=test_value")
+      config_commands.set("test_option=test_value")
 
       expect(output.string).to include("Configuration Updated:")
-      expect(output.string).to match(/Set .*test_key.* to .*test_value.*/)
-      expect(config_commands).to have_received(:save_config).with(config_path, {"test_key" => "test_value"})
+      expect(output.string).to match(/Set .*test_option.* to .*test_value.*/)
+      expect(config_commands).to have_received(:save_config).with(config_path, {"test_option" => "test_value"})
     end
 
     it "converts values to appropriate types" do
@@ -134,6 +134,25 @@
       expect(config_commands).to have_received(:save_config).with(config_path, {"test_string" => "hello"})
     end
 
+    it "refuses credential-shaped keys and values and writes nothing" do
+      %w[
+        api_token=sk-123 OPENAI_KEY=abc client_secret=x db_password=y
+        apiKey=abc api-key=abc apikey=abc accessToken=abc credentials=abc passwd=abc
+        model=sk-proj-abcdefghijklmnopqrstuvwxyz
+      ].each do |key_value|
+        expect { config_commands.set(key_value) }.to raise_error(SystemExit), "expected #{key_value} to be refused"
+      end
+
+      expect(config_commands).not_to have_received(:save_config)
+      expect(output.string).to include("Refusing to store a credential")
+      expect(output.string).to include("OPENAI_ACCESS_TOKEN")
+    end
+
+    it "still sets non-secret keys" do
+      config_commands.set("model=gpt-4o-mini")
+      expect(config_commands).to have_received(:save_config).with(config_path, {"model" => "gpt-4o-mini"})
+    end
+
     it "shows an error for invalid format" do
       # Instead of testing with the real implementation, mock the behavior
 
diff --git a/spec/agentic/cli_spec.rb b/spec/agentic/cli_spec.rb
index 99624e9..4bd985a 100644
--- a/spec/agentic/cli_spec.rb
+++ b/spec/agentic/cli_spec.rb
@@ -27,6 +27,20 @@
     end
   end
 
+  describe "#check_api_token!" do
+    it "names the configuration paths that work, not .agentic.yml" do
+      allow(Agentic).to receive(:configuration).and_return(
+        instance_double(Agentic::LegacyConfiguration, access_token: nil, api_base_url: nil)
+      )
+      allow(Agentic::UI).to receive(:box) { |title, content, _| "#{title}:\n#{content}" }
+
+      expect { described_class.new.send(:check_api_token!) }.to raise_error(Thor::Error) do |error|
+        expect(error.message).to include("OPENAI_ACCESS_TOKEN", "Agentic.configure")
+        expect(error.message).not_to include(".agentic.yml", "config set api_token")
+      end
+    end
+  end
+
   describe "agent commands" do
     describe "agent list" do
       it "displays available agents" do