docs: ChatGPT plan sign-in and the start-up update check (#1475)

- README and .env.example cover the chatgpt provider, `tradingagents login chatgpt` (also in Docker) and logout
- README and .env.example name TRADINGAGENTS_NO_UPDATE_CHECK

.env.example

@@ -35,6 +35,9 @@ NVIDIA_API_KEY=
 #AWS_DEFAULT_REGION=us-west-2
 #AWS_PROFILE=
 
+# ChatGPT Plus or Pro plan: no key; sign in once with `tradingagents login chatgpt`.
+#TRADINGAGENTS_LLM_PROVIDER=chatgpt
+
 # Remote Ollama server. Unset uses http://localhost:11434/v1.
 #OLLAMA_BASE_URL=http://your-ollama-host:11434/v1
 
@@ -54,6 +57,9 @@ NVIDIA_API_KEY=
 #TRADINGAGENTS_MAX_TOOL_ROUNDS=20
 #TRADINGAGENTS_CHECKPOINT_ENABLED=false
 
+# Turn off the start-up note about a newer release and Tauric Research notices.
+#TRADINGAGENTS_NO_UPDATE_CHECK=1
+
 # Docker: a host folder for results, reports and the memory log (unset: the tradingagents_data volume).
 #TRADINGAGENTS_DATA_DIR=./data
 

README.md

@@ -183,6 +183,8 @@ export TYPESAFE_API_KEY=...        # Jev social-post screening (optional)
 
 For Azure OpenAI, copy `.env.enterprise.example` to `.env.enterprise` and fill in your credentials.
 
+To run on your ChatGPT Plus or Pro plan instead of an API key, choose "Subscription" in the CLI's provider menu, or set `llm_provider: "chatgpt"`. Sign in once with `tradingagents login chatgpt`: it prints an address to open in your browser, which returns to this machine on `127.0.0.1`. When the browser runs on another machine, or TradingAgents runs in Docker (`docker compose run --rm tradingagents login chatgpt`), paste the address the browser ends up on. The sign-in is kept in `~/.tradingagents/chatgpt-auth.json`, and `tradingagents logout chatgpt` revokes it. Runs count toward your plan's usage limits, and the plan does not accept `temperature` or `max_tokens`.
+
 For AWS Bedrock, install the extra with `pip install ".[bedrock]"`, set `llm_provider: "bedrock"`, configure AWS credentials (environment variables, `~/.aws/credentials`, or an IAM role) and `AWS_DEFAULT_REGION`, and use a Bedrock model ID, e.g. `us.anthropic.claude-opus-5-5`.
 
 For local models, configure Ollama with `llm_provider: "ollama"`. The default endpoint is `http://localhost:11434/v1`; set `OLLAMA_BASE_URL` to point at a remote `ollama-serve`. Pull models with `ollama pull <name>`, and pick "Custom model ID" in the CLI for any model not listed by default.
@@ -213,6 +215,8 @@ tradingagents --ticker NVDA --date 2026-09-23 --analysts market,news,fundamental
 ```
 Each flag skips only its own question. Run without a terminal, a missing answer stops the run before it starts and names the flag or variable to set.
 
+At start-up the interactive CLI mentions a newer release and notices from Tauric Research. It checks at most once a day, in the background, and sends nothing about your runs; set `TRADINGAGENTS_NO_UPDATE_CHECK=1` to turn it off. Runs without a terminal never check.
+
 A saved report also includes `complete_report.html`, the report as one page with its sections listed beside the text, for reading in a browser, on a phone or in print. Answering the save question at the prompt also asks about the page and can open it in your browser; `--no-html` skips it, and so does `ta.save_reports(state, "NVDA", html=False)` from Python.
 
 ### Markets and tickers
@@ -243,7 +247,7 @@ An interface will appear showing results as they load, letting you track the age
 
 ### Implementation Details
 
-We built TradingAgents with LangGraph to ensure flexibility and modularity. The framework supports multiple LLM providers: OpenAI, Google, Anthropic, xAI, DeepSeek, Qwen (Alibaba DashScope, international and China endpoints), GLM (Zhipu), MiniMax (global + China), OpenRouter, Ollama for local models, and Azure OpenAI for enterprise.
+We built TradingAgents with LangGraph to ensure flexibility and modularity. The framework supports multiple LLM providers: OpenAI, Google, Anthropic, xAI, DeepSeek, Qwen (Alibaba DashScope, international and China endpoints), GLM (Zhipu), MiniMax (global + China), OpenRouter, Ollama for local models, Azure OpenAI for enterprise, and your own ChatGPT plan.
 
 ### Python Usage