Fix remaining PTY and bundle watch races

Keep inherited child prompt markers bounded by the normal silence fallback. Stage web-plugin rescans atomically and retain missing watch state until a successful rebuild.

packages/host/webserver/README.md

@@ -8,7 +8,7 @@ Client-disconnect detection hangs off the **response** `close` event, not the re
 
 A request whose handling throws (a malformed %-escape hitting `decodeURIComponent`, a client dropping mid-body) is answered 400 — or the socket destroyed when headers are already out — and reported to `onError`; it never becomes a process-killing unhandled rejection.
 
-In development, the client-plugin registry synchronously captures each built bundle's stat baseline before it returns, then polls those baselines and re-hashes changed content. An immediate rebuild therefore cannot disappear into an asynchronously established watch baseline; a rename window retains the last successful baseline and retries when the bundle reappears.
+In development, the client-plugin registry synchronously captures each built bundle's stat baseline before it returns, then polls those baselines and re-hashes changed content. Each rescan stages its candidate table, graph, and watch map before publishing them, so a baseline failure preserves the prior graph. An immediate rebuild therefore cannot disappear into an asynchronously established watch baseline; a rename window marks the path dirty, retains the last successful baseline, and forces a re-hash when the bundle reappears even with identical metadata.
 
 ## Model Experience
 

packages/host/webserver/src/web-plugins.ts

@@ -129,6 +129,13 @@ interface WebPluginRecord {
   clientPath: string
 }
 
+interface WatchedBundle {
+  path: string
+  mtimeMs: number
+  size: number
+  dirty: boolean
+}
+
 /** Narrow an unknown parsed JSON value to the dshClient declaration, throwing on malformed fields. */
 function parseDshClient(name: string, value: unknown): DshClientDeclaration | undefined {
   if (value === undefined) return undefined
@@ -203,8 +210,32 @@ export function createHostWebPluginRegistry(deps: WebPluginRegistryDeps): HostWe
     throw new Error(`web-plugins: watch.intervalMs must be a positive integer (got ${String(deps.watch?.intervalMs)})`)
   }
 
+  const stageWatches = (
+    candidateTable: Map<string, WebPluginRecord>,
+    currentWatches: Map<string, WatchedBundle>,
+  ): Map<string, WatchedBundle> => {
+    const candidateWatches = new Map<string, WatchedBundle>()
+    if (watchInterval === undefined) return candidateWatches
+    for (const [id, record] of candidateTable) {
+      const current = currentWatches.get(id)
+      if (current?.path === record.clientPath) {
+        candidateWatches.set(id, { ...current })
+        continue
+      }
+      const baseline = statSync(record.clientPath)
+      candidateWatches.set(id, {
+        path: record.clientPath,
+        mtimeMs: baseline.mtimeMs,
+        size: baseline.size,
+        dirty: false,
+      })
+    }
+    return candidateWatches
+  }
+
   let table = scan(deps)
   let graph = composeGraph(table)
+  let watched = stageWatches(table, new Map())
   const rebuildListeners = new Set<(id: string, rev: string) => void>()
 
   const rebuilt = (id: string): string | undefined => {
@@ -220,21 +251,6 @@ export function createHostWebPluginRegistry(deps: WebPluginRegistryDeps): HostWe
   // registry is returned, then poll those baselines. fs.watchFile establishes
   // its first baseline asynchronously, so an immediate rebuild can otherwise
   // become the baseline and disappear without an observed delta.
-  const watched = new Map<string, { path: string; mtimeMs: number; size: number }>()
-  const syncWatches = (): void => {
-    if (watchInterval === undefined) return
-    for (const [id, watch] of watched) {
-      if (table.get(id)?.clientPath === watch.path) continue
-      watched.delete(id)
-    }
-    for (const [id, record] of table) {
-      if (watched.has(id)) continue
-      const baseline = statSync(record.clientPath)
-      watched.set(id, { path: record.clientPath, mtimeMs: baseline.mtimeMs, size: baseline.size })
-    }
-  }
-  syncWatches()
-
   const pollWatches = (): void => {
     for (const [id, watch] of watched) {
       let current: Stats
@@ -242,18 +258,24 @@ export function createHostWebPluginRegistry(deps: WebPluginRegistryDeps): HostWe
         current = statSync(watch.path)
       } catch (error) {
         const code = (error as NodeJS.ErrnoException).code
-        if (code === 'ENOENT') continue // mid-rename window; retry against the retained baseline
+        if (code === 'ENOENT') {
+          watch.dirty = true
+          continue
+        }
         deps.onError(error instanceof Error ? error : new Error(String(error)))
         continue
       }
-      if (current.mtimeMs === watch.mtimeMs && current.size === watch.size) continue
+      if (!watch.dirty && current.mtimeMs === watch.mtimeMs && current.size === watch.size) continue
       const before = table.get(id)?.entry.rev
       let rev: string | undefined
       try {
         rev = rebuilt(id)
       } catch (error) {
         const code = (error as NodeJS.ErrnoException).code
-        if (code === 'ENOENT') continue // mid-rename window; retry against the retained baseline
+        if (code === 'ENOENT') {
+          watch.dirty = true
+          continue
+        }
         watch.mtimeMs = current.mtimeMs
         watch.size = current.size
         deps.onError(error instanceof Error ? error : new Error(String(error)))
@@ -261,6 +283,7 @@ export function createHostWebPluginRegistry(deps: WebPluginRegistryDeps): HostWe
       }
       watch.mtimeMs = current.mtimeMs
       watch.size = current.size
+      watch.dirty = false
       if (rev === undefined || rev === before) continue
       for (const notify of rebuildListeners) {
         // A throwing subscriber must not skip later subscribers or escape the
@@ -283,9 +306,12 @@ export function createHostWebPluginRegistry(deps: WebPluginRegistryDeps): HostWe
     queueMicrotask(() => {
       pending = false
       try {
-        table = scan(deps)
-        graph = composeGraph(table)
-        syncWatches()
+        const candidateTable = scan(deps)
+        const candidateGraph = composeGraph(candidateTable)
+        const candidateWatches = stageWatches(candidateTable, watched)
+        table = candidateTable
+        graph = candidateGraph
+        watched = candidateWatches
       } catch (error) {
         // Keep serving the previous graph: a mid-flight rescan failure must not
         // take down the boot manifest for plugins that were fine.

packages/host/webserver/tests/web-plugins.spec.ts

@@ -1,11 +1,41 @@
-import { mkdirSync, mkdtempSync, writeFileSync } from 'node:fs'
+import {
+  mkdirSync,
+  mkdtempSync,
+  statSync,
+  type PathLike,
+  type Stats,
+  unlinkSync,
+  utimesSync,
+  writeFileSync,
+} from 'node:fs'
 import { tmpdir } from 'node:os'
 import { join } from 'node:path'
 import { Context } from 'cordis'
-import { describe, expect, it, vi } from 'vitest'
+import { afterEach, describe, expect, it, vi } from 'vitest'
 import { createHostWebPluginRegistry, injectBootManifest } from '../src/index.ts'
 import type { LoaderEntryView, WebPluginRegistryDeps } from '../src/index.ts'
 
+const fsControl = vi.hoisted(() => ({ failNextStatPath: undefined as string | undefined }))
+
+vi.mock('node:fs', async (importOriginal) => {
+  const actual = await importOriginal<typeof import('node:fs')>()
+  return {
+    ...actual,
+    statSync: (path: PathLike): Stats => {
+      if (String(path) === fsControl.failNextStatPath) {
+        fsControl.failNextStatPath = undefined
+        throw Object.assign(new Error('staged bundle missing'), { code: 'ENOENT' })
+      }
+      return actual.statSync(path)
+    },
+  }
+})
+
+afterEach(() => {
+  fsControl.failNextStatPath = undefined
+  vi.useRealTimers()
+})
+
 /** Write a fake installed package (package.json + optional client bundle) and return its package.json path. */
 function makePkg(root: string, name: string, pkg: Record<string, unknown>, withBundle = true): string {
   const dir = join(root, name.replaceAll('/', '__'))
@@ -147,6 +177,58 @@ describe('createHostWebPluginRegistry', () => {
     expect(rebuilds).toHaveLength(1)
   })
 
+  it('watch mode: a failed rescan baseline preserves the published table and graph', async () => {
+    const { deps, entries, errors, ctx, root } = makeDeps([
+      { name: 'stable', pkg: webDecl() },
+      { name: 'late', pkg: webDecl(), loaded: false },
+    ])
+    deps.watch = { intervalMs: 1_000 }
+    const registry = createHostWebPluginRegistry(deps)
+    const before = registry.graph()
+
+    ;(entries[1] as { fiber?: unknown }).fiber = {}
+    fsControl.failNextStatPath = join(root, 'late', 'lib', 'client.js')
+    ctx.emit('internal/plugin', ctx.fiber)
+    await Promise.resolve()
+
+    expect(errors[0]?.message).toContain('staged bundle missing')
+    expect(registry.graph()).toBe(before)
+    expect(registry.clientPath('late')).toBeUndefined()
+
+    ctx.emit('internal/plugin', ctx.fiber)
+    await Promise.resolve()
+    expect(registry.graph().entries.map(row => row.id)).toEqual(['stable', 'late'])
+    registry.dispose()
+  })
+
+  it('watch mode: a missing bundle forces a re-hash when identical metadata reappears', async () => {
+    vi.useFakeTimers()
+    const { deps, root } = makeDeps([{ name: 'watched', pkg: webDecl() }])
+    const bundle = join(root, 'watched', 'lib', 'client.js')
+    const fixedTime = new Date(1_600_000_000_000)
+    utimesSync(bundle, fixedTime, fixedTime)
+    deps.watch = { intervalMs: 20 }
+    const registry = createHostWebPluginRegistry(deps)
+    const baseline = statSync(bundle)
+    const rebuilds: { id: string; rev: string }[] = []
+    registry.onRebuilt((id, rev) => rebuilds.push({ id, rev }))
+
+    unlinkSync(bundle)
+    await vi.advanceTimersByTimeAsync(20)
+    writeFileSync(bundle, 'x'.repeat(baseline.size))
+    utimesSync(bundle, fixedTime, fixedTime)
+    const restored = statSync(bundle)
+    expect({ mtimeMs: restored.mtimeMs, size: restored.size }).toEqual({
+      mtimeMs: baseline.mtimeMs,
+      size: baseline.size,
+    })
+    await vi.advanceTimersByTimeAsync(20)
+
+    expect(rebuilds).toHaveLength(1)
+    expect(registry.graph().entries[0]?.rev).toBe(rebuilds[0]?.rev)
+    registry.dispose()
+  })
+
   it('rejects a non-positive or non-integer watch interval at build time', () => {
     for (const intervalMs of [0, -5, 1.5]) {
       const { deps } = makeDeps([{ name: 'p', pkg: webDecl() }])