86 features in 12 months: Codex ships 35, Cowork sprints to 40 in eight, ChatGPT Work adds 11 in two

Asked:

“What major and minor features were added to OpenAI Codex and Claude Cowork and ChatGPT Work in the past 12 months - for each one I want the date, links to any announcements, a short description and a best guess at the official name for the feature”

The inventory covers 2025-09-01 through 2026-09-01 and holds 86 feature additions: OpenAI Codex 35 (12 major, 23 minor), Claude Cowork 40 (8 major, 32 minor), and ChatGPT Work 11 (3 major, 8 minor). Cowork launched in research preview on 2026-01-12 and ChatGPT Work on 2026-07-09, so their lanes start mid-year. Major/minor is an editorial judgement, not a vendor label.

major release (large square)minor release (small square)colour = product lane · hover any mark for the feature and its link

Codex's year was model-driven: five major model additions — GPT-5-Codex, GPT-5.2-Codex, GPT-5.4, GPT-5.5 and Fast mode variants — each landed with a cluster of same-day minor tooling additions. help.openai.com

Claude Cowork shipped 40 additions in under eight months — the densest lane on the timeline — mostly minor workflow and connector updates batched onto dated release-note pages. support.claude.com

ChatGPT Work concentrated its 3 major additions on launch (2026-07-09) and on 2026-08-20, when Sites collaboration and Apple Messages access arrived together. help.openai.com

2026-03-05 was the single busiest day: GPT-5.4 plus four minor Codex capabilities (computer use, tool search, /fast mode, interactive Playwright) shipped at once. openai.com

Method: curated inventory of 86 feature additions across OpenAI Codex (35), Claude Cowork (40) and ChatGPT Work (11), window 2025-09-01 to 2026-09-01. “Major/minor” is an editorial best guess, not an official vendor label. “Official name” is the closest official heading or concise official-style label found in announcements and release notes. Included: product capabilities, integrations, model additions, interface/workflow additions, platform/plan expansions, and meaningful admin/security controls; pure bug fixes and performance-only changes were excluded. Sources prioritize official OpenAI/Anthropic announcements, help-center release notes, and official changelogs; several granular changes share a single dated release-note page. Blank links in the curated set were recovered from the original-source candidate inventory.

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