United Kingdom, Nov. 22 -- Wall Street's biggest research houses are redrawing their playbooks as private companies like OpenAI grow so large and influential that investors demand the same level of insight traditionally reserved for public firms.

Banks including Morgan Stanley, JPMorgan, Citigroup and UBS are now expanding formal coverage of private assets - a shift Bloomberg reports is being driven directly by the ChatGPT maker's outsized market impact and investors' fear of missing the next seismic move in AI.

Citigroup, for example, has hired veteran tech analyst Heath Terry to lead private-company coverage, while JPMorgan recently published a deep-dive initiation note on OpenAI itself.

The rationale is twofold: clients either want ...