AI Development & Programming: Build Apps with AI

A site with an address like xxx.chatgpt.site is one that a ChatGPT user built and published with a feature called ChatGPT Sites. OpenAI provides the hosting, but it does not create the content or review or approve it, and responsibility lies with whoever built the site. This article is based on OpenAI's help articles, developer guide, terms, and release notes, which I checked in the original on October 11, 2026. ChatGPT Sites was introduced as a public beta on July 9, 2026, and is available on Plus, Pro, Business, Enterprise, and Edu, but not on Free or Go. During the beta, it is included in your subscription up to each plan's limits; the limit values and pricing after the beta have not been announced. The beta is provided "as is," OpenAI can unpublish a site for any reason, and even the example site in the developer guide returned a 404 when I checked. The article covers the constraints to know before using it in production (no guarantees, no choice of where data is stored, prohibited uses, and the creator's responsibility) and the uses it suits, how to connect a custom domain and change the URL, how to set visibility and permanently delete a site, and whether your conversations are used for training.

Claude's Max, Ultra, and Team plans come with credits you can use on the Claude API every month ($100 on Max, $200 on Ultra, and up to $500 in total on Team depending on the number of seats). However, you don't receive them until you link a Claude Console organization on the claude.ai billing page, and unused credits don't roll over. This article is based on my record of the screens when I claimed the credits on a Max 20x (now Ultra) plan on October 10, 2026, and on the official documentation, help articles, and terms, which I checked in the original on the same day. It explains where the credits can be used (the API, Message Batches, Managed Agents, the Agent SDK, the Playground, and claude -p run with an API key) and where they can't (interactive Claude Code, extra usage in the apps, Bedrock, and more); that linking partway through a cycle still gave me the full amount, expiring about three weeks later; that you can't change the linked organization yourself and an organization can receive only one plan's credits; the order credits are used in and auto-reload; how keeping ANTHROPIC_API_KEY set permanently switches Claude Code to API billing; ways to use the credits up and spend limits; and key points from the terms, such as the credits not being transferable or sellable.

Compare Codex Remote and Cloud by where work runs, PC sleep behavior, phone access, development environments, and usage allowances. Learn the conditions for the connected PC, Cloud setup and unsupported features, Handoff limits, and how Work Cloud and dot differ. Also see what to check when a connection fails.

Use Codex /goal to keep a completion condition across investigation, fixes, and verification. This guide separates desktop and CLI operations, gives example requests, and covers pausing, resuming, clearing, and reasons work stops partway. It also explains how token budgets differ from pricing and what evidence to check in a completion report.

Before choosing Codex Security, compare the local plugin, the GitHub-connected Cloud service, and the standalone CLI. This guide uses official documentation to explain separate Cloud billing, conditional free scan credits, first-scan setup, Standard and Deep costs, scan coverage and reproduction evidence, and post-fix verification. It also covers when the standalone CLI uses an API key from the environment and how estimated cost limits work.

Claude Code mods (Claude Mods) are plugins that run JavaScript or TypeScript functions inside Claude Code, officially added in v2.1.287 on October 1, 2026. This article explains how a mod made of three files works, how it differs from traditional hooks written in settings.json, skills and MCP, what mods can do, such as drawing panes in the interface, creating commands that run without waiting and holding a tool call to ask the user, and limits such as run time, all based on the original text of the official docs checked on October 5 of the same year. A mod runs with your permissions outside the sandbox and can override permission decisions. A table shows that deny rules hold on Team or Enterprise or on a machine with managed settings, but on a personal plan a mod can approve even calls a deny rule refused. It also covers the results of reading the code of Anthropic's three official sample mods and counting which APIs they use, how to read claude plugin validate before installing, how to try mods, have Claude build one and turn them off, where mods run and the built-in mods, and a checklist before installing.

Prompt caching reuses the computed results for the start of a request that matches an earlier one, so that part of the input costs less and runs faster. OpenAI (GPT-5.6 and later) turns it on by default and keeps the cache at least 30 minutes after last use (12 hours is optional), with writes at 1.25x the input price (2.5x for 12 hours) and reads at 0.1x (0.05x for GPT-6.1 Sol); Claude caches only when a request includes cache_control, with a 5-minute cache (1 hour is optional), writes at 1.25x (2x for 1 hour), and reads at 0.1x (0.05x for Opus 5.5 and Sonnet 5.5, 0.025x for Fable 5.1). Based on both companies' official documentation as of October 3, 2026, this article compares minimum length, breakpoints, sharing scope, and rate limits, works out how many reads it takes to break even, and explains common misses and how to check hits with usage and diagnostics.

The Codex message "Selected model is at capacity" is caused by congestion on OpenAI's side. Official incident records and our own execution logs both classify it as server overload. This guide covers the steps to take in order (wait, check incidents, try another model), how it differs from usage limits, 401, and thread not found, and what to record if it happens again.

On Windows, Claude Desktop refuses to start and shows "There's a problem with Claude. Reinstall the application from its original install location or contact your administrator." This is the message Windows shows when it refuses to launch a packaged (MSIX) app, and neither Anthropic's help center nor its documentation explains it or how to fix it (as of September 30, 2026). The dialog says to reinstall, but checking the state with Get-AppxPackage first tells you which route to take. If nothing is returned, the package registration is gone and a reinstall is all it takes. If Status reads Modified, NeedsRemediation, end the leftover processes and try Repair, then re-register with -DisableDevelopmentMode, then run the official installer over the top, and only as a last resort back up, remove and reinstall. A reinstall keeps your chat history and your Claude Code conversation logs (.claude\projects), but users report that the desktop app's session list was lost; claude --resume still opens those sessions. Microsoft's documentation limits Remove-AppxPackage -PreserveApplicationData to apps under development, and it has been reported to fail with 0x80073CFA. The article also sorts out the triggers seen in GitHub reports: crashes in the built-in browser, auto-updates while the app is running, and failed Cowork service registration.

If Claude Code shows "API Error: Opus 5.5's safeguards flagged this message" or "safeguards flagged this session," a safety classifier attached to the model has reacted to the content of your conversation and stopped that model from responding. Issue titles also call it "Message flagged by safeguards." The classifiers run on the server side and look not just at your last sentence but at the whole conversation, the files that were read, and even CLAUDE.md, so an ordinary message like "hi" can get stopped, and Anthropic acknowledges false positives. Drawing on the official error reference, the model configuration documentation, the API's Refusals and fallback page and the Help Center, we lay out what the cyber, bio, reasoning_extraction, general_harms and frontier_llm categories in the Details field mean, when Claude Code automatically switches to another model and when it simply stops, how to use Esc twice to rewind, /clear, /model, --safe-mode and /feedback, the October 6, 2026 expansion of CVP into three tiers that also cover Opus 5.5 and Sonnet 5.5, and how stopped requests are billed. GitHub reports filed since September 22 are kept separate from the official explanations and treated as unconfirmed cases.

On September 28, 2026, Anthropic released Claude Sonnet 5.5, and Sonnet 5 moved to Legacy. This article checks the official documentation (Models overview, the Sonnet 5.5 page, What's new, the migration guide, Pricing, Thinking, Effort and Prompt caching), the announcement, the Claude Code documentation and CHANGELOG, and the GitHub changelog against each other in the original text. It covers the core specs (claude-sonnet-5-5, a 1M context, 128K max output, a June 2026 knowledge cutoff, and retirement not before September 28, 2027), pricing ($2 input and $10 output, the same as Sonnet 5, with cache reads cut from $0.20 at launch to $0.10 on October 7, 2026, while the minimum cacheable length dropped from 1,024 to 512 tokens), and the figures in Anthropic's comparison table (70.6% on Terminal-Bench 4.0, and 1844 on GDPval-AA v2.1, 2 points behind Opus 5.5, though the announcement itself says Opus 5.5 is clearly stronger on complex, open-ended work). It then walks through the five changes that make code that worked on Sonnet 5 fail with a 400 error (turning thinking off moves to between_tools with effort high or below, forced tool use, thinking blocks bound to the model and the conversation, the legacy computer use tool on the Claude API and Google Cloud, and advisor tool pairings) and how to fix them, changes that happen without an error such as text between tool calls moving into thinking blocks, the difference in default effort (high on the API, medium in Claude Code), how to choose between it, Opus 5.5 and Haiku, how to use it in Claude Code (/model sonnet from v2.1.284) and GitHub Copilot, and the migration steps.

If Claude Code shows “claude.ai connectors are disabled because ANTHROPIC_API_KEY or another auth source is set and takes precedence over your claude.ai login,” a credential such as the ANTHROPIC_API_KEY environment variable is taking precedence over your saved claude.ai login, and the connectors you added in claude.ai are not being loaded. Your login is not gone; it just isn’t used because of precedence. Based on the official authentication and MCP documentation and the CHANGELOG, this article covers authentication precedence, how to check which credential is in use with /status and environment variables, where the key comes from (shell config, .env, env and apiKeyHelper in settings files), how to remove the key, restart, and confirm, what you lose by staying on an API key (connectors, Remote Control, /schedule) and how billing differs, and how to stop the warning with disableClaudeAiConnectors. Points not in the official docs are shown separately as things we checked in the Claude Code binary itself.