fix(pi-plugin): support pi-web multi-session and RPC hosts

packages/pi-plugin/PARITY.md

@@ -23,14 +23,20 @@ plugin process and reach `experimental.chat.messages.transform`. OpenCode gates
 historian / m[0]m[1] injection / nudges / auto-search behind `fullFeatureMode`
 (i.e. `!isSubagent`), and detects subagents via OpenCode's `session.parent_id`.
 
-**Pi:** Pi has **no native subagent concept**. The *only* subagents that exist
-are the ones Magic Context itself spawns (historian, dreamer, sidekick), and each
-runs as a **separate `pi --print` process** loading only the lean
-`subagent-entry.js`, whose recursion guard **never wires `pi.on("context")`**
-(see `subagent-entry.ts` header). A Pi subagent therefore *cannot* reach the
-context-handler pipeline at all.
-
-**Consequence:** `is_subagent` is **never written `true`** for any Pi session.
+**Pi:** Pi has **no native subagent concept**. The subagents Magic Context itself
+spawns (historian, dreamer, sidekick) each run as a **separate `pi --print` process**
+loading only the lean `subagent-entry.js`, whose recursion guard **never wires
+`pi.on("context")`** (see `subagent-entry.ts` header). A Magic Context subagent
+therefore *cannot* reach the context-handler pipeline at all.
+`@gotgenes/pi-subagents`, however, can initialize a child session inside the same
+process. The full extension uses Pi's public child-session lifecycle events plus
+process-shared `AsyncLocalStorage` to suppress only the child while allowing
+unrelated same-process sessions to initialize normally.
+
+**Consequence:** `is_subagent` is **never written `true`** for any Pi session
+that reaches the context-handler pipeline. Separate child processes load the lean
+entry, while in-process child initialization is suppressed before the normal
+context pipeline is registered.
 There is nothing to gate, so Pi does NOT need OpenCode's `fullFeatureMode`
 reduced-mode enforcement in `context-handler.ts`. The vestigial `!isSubagent`
 checks that exist in the Pi context handler are harmless (always take the
@@ -115,15 +121,22 @@ the source array for dirty indices only.
 
 ---
 
-## 6. Transient UI: Pi uses `ctx.ui.notify` toasts, not persistent dialogs
+## 6. Transient UI: Pi uses `ctx.ui.notify` toasts and RPC dialogs
 
 **OpenCode:** TUI dialogs (upgrade prompt, `/ctx-status`, `/ctx-recomp`, `/ctx-embed`, `/ctx-flush`) via RPC,
 with an ignored-message fallback for Desktop/Web. Notification drain is
 **session-scoped** (a notification tagged for one session never surfaces in
 another) because one process can serve multiple sessions and TUI port discovery
 is newest-pid-wins.
 
-**Pi:** transient terminal notifications. The upgrade reminder passes
+**Pi:** command status is appended as a model-invisible custom entry. Interactive
+terminals render that entry through the registered entry renderer. In Pi RPC
+mode, each command uses its live `ctx`: `ctx.ui.notify` presents short progress
+as toasts. RPC hosts that execute the `ctx.ui.custom` component factory (such as
+pi-web) present detailed results as dialogs; hosts where `custom` resolves without
+executing the factory receive the same details through a notification fallback.
+A context captured by `session_start` cannot be reused because pi-web can host
+multiple sessions in one process. The upgrade reminder passes
 `deliveryPersists=false` on Pi, so a missed toast does not honor the old explicit-
 dismissal stamp. Both harnesses persist the 24-hour reminder cooldown and three-
 delivery cap, preventing repeated startup toasts while `/ctx-status` still reports
@@ -155,6 +168,13 @@ shared resolver's log-only dubious-ownership warning while still using the same
   **stdin** (Pi concatenates stdin + positional) to avoid Linux `MAX_ARG_STRLEN`
   / E2BIG; the positional is omitted when piping.
 - `--no-session` keeps subagent JSONL out of the user's session picker.
+- In pi-web, multiple sessions can share one process. Startup maintenance runs
+  once per process, while each session wires its own hooks. Dreamer registration
+  is process-shared and tracks sibling ownership, so one session's shutdown cannot
+  deregister another session's project timer.
+- `session_shutdown` drains only that session's in-flight historian and recomp work
+  and only the shutting-down extension instance's Dreamer work. Child-session
+  lifecycle listeners are detached only for that extension instance.
 
 ---
 
@@ -385,7 +405,8 @@ mechanism differs because the process models differ:
   inline `await` froze all input. Pi instead spawns the recomp via
   `spawnPiRecompRun` (mirroring `spawnPiHistorianRun`): the handler returns
   immediately after the ack message, the run is tracked in an in-flight map for
-  `session_shutdown` drain, and progress surfaces through `[ctx-status]`
+  `session_shutdown` drain (keyed by session id so one session does not drain
+  another), and progress surfaces through `[ctx-status]`
   messages + the `recomp` status-line flag.
 
 Because Pi's recomp runs in the background (not inside the user's turn), its

packages/pi-plugin/src/agent-end-handler.test.ts

@@ -107,15 +107,42 @@ describe("session_shutdown handler (drain location)", () => {
 	const body = extractSessionShutdownHandlerBody(INDEX_SRC);
 
 	test("drains in-flight historians through withTimeout", () => {
-		expect(body).toContain("awaitInFlightHistorians");
-		expect(body).toContain(
-			"withTimeout(awaitInFlightHistorians(), SHUTDOWN_DRAIN_MS)",
+		expect(body).toMatch(
+			/withTimeout\(\s*awaitInFlightHistorians\(sessionId\),\s*SHUTDOWN_DRAIN_MS,?\s*\)/,
 		);
 		expect(body).not.toContain("Promise.race");
 	});
 
-	test("drains in-flight dreamers (Promise.race with timeout)", () => {
-		expect(body).toContain("awaitInFlightDreamers");
+	test("drains the shutting-down session's recomp through withTimeout", () => {
+		expect(body).toMatch(
+			/withTimeout\(\s*awaitInFlightRecomps\(sessionId\),\s*SHUTDOWN_DRAIN_MS,?\s*\)/,
+		);
+	});
+
+	test("aborts a recomp that outlives the graceful drain before shutdown returns", () => {
+		const drainAt = body.indexOf("awaitInFlightRecomps(sessionId)");
+		const abortAt = body.indexOf("abortInFlightRecomps(sessionId)");
+		expect(abortAt).toBeGreaterThan(drainAt);
+	});
+
+	test("drains the current extension owner's dreamers through withTimeout", () => {
+		expect(body).toMatch(
+			/withTimeout\(\s*awaitInFlightDreamers\(dreamerRegistrationOwner\),\s*SHUTDOWN_DRAIN_MS,?\s*\)/,
+		);
+	});
+
+	test("stops Dreamer registration before draining its work", () => {
+		const shutdownAt = body.indexOf("sessionShuttingDown = true");
+		const unregisterAt = body.indexOf("unregisterPiDreamerProject");
+		const drainAt = body.indexOf("awaitInFlightDreamers");
+		expect(shutdownAt).toBeGreaterThanOrEqual(0);
+		expect(unregisterAt).toBeGreaterThanOrEqual(0);
+		expect(drainAt).toBeGreaterThanOrEqual(0);
+		expect(shutdownAt).toBeLessThan(unregisterAt);
+		expect(unregisterAt).toBeLessThan(drainAt);
+		expect(INDEX_SRC).toMatch(
+			/function syncDreamerProjectRegistration[\s\S]*?if \(sessionShuttingDown\) return;/,
+		);
 	});
 
 	test("drain timeout uses unref/clear helper", () => {