The Agent Client Protocol is a bet that IDE vendors and AI coding agents should stop negotiating integration details bilaterally. ACP proposes a shared contract so that any compliant agent can plug into any compliant IDE without custom glue code. JetBrains is co-leading the standard, which means IntelliJ-family tooling gets first-class support, but the open governance framing is meant to pull in other IDE vendors. Whether this gains traction depends on whether competing vendors see enough benefit to cede some interface control. The timing is sharp — agent-IDE integration has been a friction point since coding assistants proliferated — and an open standard has a better shot than a vendor-specific SDK. Worth tracking if you're building tooling that needs to talk to developer environments.