scope client env to sessions so herdr extensions see the right pane

[kevinjosethomas]

• extensions run in the daemon, so a shared daemon served every herdr pane the env of whichever client spawned it first; Pass herdr env vars from interactive client through daemon protocol to extensions #276 fixed this by mutating global process.env on create/attach, which lets concurrent panes clobber each other.
• the interactive client now forwards an allowlist of herdr env vars on create and attach, and the daemon stores them per session instead of touching its own env.
• extension subprocesses get the session's env merged over process.env at exec time, and extension loading (plus /reload) runs in a serialized scoped-env window since extensions capture pane identity synchronously at load.

---

Note

Medium Risk
Touches daemon session lifecycle, concurrent env-window locking, and subprocess env for all extension exec paths; wrong scoping could leak or mix pane identity across sessions.

Overview
Replaces shared daemon process.env mutation with per-session client env so concurrent herdr panes no longer clobber each other.

Interactive clients send an allowlisted herdr env on create (and primary attach with sendClientEnv). The daemon stores it on ActiveSessionState, adopts-if-absent when reusing env-less sessions (e.g. cron), and never overwrites an existing identity.

withClientEnv temporarily pins that env during extension load/reload and serializes exclusive windows vs env-less loads. setRuntimeEnvScope / scopedBuild wrap every runtime rebuild (new/switch/fork/import, subagents). pi.exec merges session env at spawn via getExecEnv / execEnvForSession without mutating the daemon’s global env. Subagents inherit the parent’s clientEnv.

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Note

Scope client env to daemon sessions so extensions see the correct environment per pane

• Adds a DaemonClientEnv allowlist and protocol fields so create and attach commands carry the client's env to the daemon; attach adopts env only if the session has none (adopt-if-absent).
• Pins a per-session exec env provider so pi.exec() subprocesses use the session's client env rather than the daemon's global process.env.
• Wraps all extension load windows (runtime builds, reloads, subagent creation) in withClientEnv to ensure extension modules see the correct env during evaluation.
• Subagents inherit their parent session's client env for both extension loading and exec.
• Risk: withClientEnv uses an exclusive lock during env-bound loads; high session concurrency may serialize extension reloads briefly.

^{Macroscope summarized a39171b.}

[macroscopeapp]

🟡 Medium

prime-agent/packages/coding-agent/src/modes/daemon/daemon-mode.ts

Line 1311 in 637a0a6

case "new_session": {

The new_session, switch_session, fork, and import_jsonl handlers rebuild the runtime via state.runtime's stored factory, which calls createAgentSessionRuntime() with the unwrapped this.options.createRuntime. Extensions are loaded during that factory call without withClientEnv(state.clientEnv, ...), so state.clientEnv is never applied to process.env and pane-scoped extensions cannot read their client identity (e.g. HERDR_PANE_ID). Only the explicit reload command wraps extension loading in withClientEnv, so any session-replacement flow silently drops client env from extension load context.

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In file @packages/coding-agent/src/modes/daemon/daemon-mode.ts around line 1311:

The `new_session`, `switch_session`, `fork`, and `import_jsonl` handlers rebuild the runtime via `state.runtime`'s stored factory, which calls `createAgentSessionRuntime()` with the unwrapped `this.options.createRuntime`. Extensions are loaded during that factory call without `withClientEnv(state.clientEnv, ...)`, so `state.clientEnv` is never applied to `process.env` and pane-scoped extensions cannot read their client identity (e.g. `HERDR_PANE_ID`). Only the explicit `reload` command wraps extension loading in `withClientEnv`, so any session-replacement flow silently drops client env from extension load context.

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