docs(coding-agent): document AI_AGENT process marker

closes #7747

packages/coding-agent/CHANGELOG.md

@@ -9,6 +9,7 @@
 ### Changed
 
 - Replaced the inherited Mistral SDK transport with a native Chat Completions HTTP stream, eliminating its generated client and schema runtime overhead.
+- Documented the generic `AI_AGENT=pi` process marker and how it differs from `PI_CODING_AGENT=true` ([#7747](https://github.com/earendil-works/pi/issues/7747)).
 
 ## [0.84.1] - 2026-08-07
 

packages/coding-agent/docs/environment-variables.md

@@ -3,14 +3,19 @@
 Pi uses environment variables in three ways:
 
 - Variables such as `PI_OFFLINE` configure the Pi process.
-- Pi sets `PI_CODING_AGENT` so child processes can detect that they run inside Pi.
+- Pi sets process markers so child processes can identify Pi as the launching agent.
 - Commands run by the LLM-callable bash tool receive `PI_*` variables describing the current session.
 
 Provider API-key variables are documented separately in [Providers](providers.md#environment-variables-or-auth-file).
 
 ## Process Marker
 
-The CLI and RPC entry points set `PI_CODING_AGENT=true`. Child processes inherit it and can use it to detect that they run inside Pi. It is not session-specific and is not set automatically when Pi is embedded through the SDK.
+The CLI and RPC entry points set two process markers:
+
+- `AI_AGENT=pi` is a generic marker that lets tooling identify Pi as the agent that launched the process.
+- `PI_CODING_AGENT=true` is Pi-specific and lets child processes detect that they run inside Pi.
+
+Child processes inherit both markers. They are not session-specific and are not set automatically when Pi is embedded through the SDK.
 
 ## Bash Tool Session Environment