Analyze ForEach-Object parallel child runspaces

Author: Aaronontheweb

IMPLEMENTATION_PLAN.md

@@ -350,7 +350,7 @@ priorities.
       delivered for ordinary, adjacent, quoted, here-string, redirect, standalone,
       call-operator, dynamic-identity, and host-wrapper positions, with
       current-scope state propagation and bounded expression rejection pinned
-      by the 372-entry executable corpus.
+      by the 383-entry executable corpus.
 - [ ] Deliver typed PowerShell script-block execution regions before calling
       tasks 7.5-7.7 complete. The corrected contract adds an execution-region
       syntax node with independent origin, phase, timing, and cardinality rather than a
@@ -425,8 +425,27 @@ priorities.
       proved child-process isolation while their body analysis stays fail
       closed; an explicit alternate `-PSVersion` remains visible but incomplete
       because it falls outside the pinned PowerShell 7 runtime model.
-      Child runspace jobs and parallel
-      blocks; deferred breakpoint/event/completion actions; then unknown
+      `ForEach-Object -Parallel` now publishes a concurrent per-input child-
+      runspace region, inherits the captured caller location, starts without
+      caller bindings or alias mutations, and isolates runspace-local child
+      exit from the host continuation, including `-AsJob`. Pooled-runspace command-
+      resolution mutation is joined across later activations; `-UseNewRunspace`
+      keeps activations independent. Live PowerShell probes pin both behaviors,
+      including the process-wide environment-provider exception: a possibly
+      escaping child mutation invalidates later host binding, command-
+      resolution, and location facts and also poisons later child activations
+      under `-UseNewRunspace`, which resets runspace-local but not process-wide
+      state. Runspace-global variables, functions, aliases, and location remain
+      isolated. The analyzer retains a bounded, case-insensitive set of exact
+      alias/function names whose identity changed and treats only matching later
+      invocations as possible process escapes; an ambiguous mutation or set
+      overflow fails closed to every unproved command name. This includes a
+      mutator such as `Set-Alias` being rebound to `Set-Item` before a later
+      authored `Set-Alias Env:...` invocation.
+      The generator-owned executable corpus now supports per-entry initial-
+      state mode and includes the promoted Parallel design case. Pinned child
+      runspace jobs and remote/session invocation remain before deferred
+      breakpoint/event/completion actions; then unknown
       receiver and nested/adversarial matrices. Preserve script blocks proved
       to be data as opaque values, expose ambiguous bodies with incomplete
       facts, and fail atomically when any potentially executable interior is

SPEC.POWERSHELL.md

@@ -529,7 +529,7 @@ The version-pinned PowerShell 7 catalog covers:
 | `ForEach-Object -Begin` | Begin | Synchronous | Once | current runspace |
 | `ForEach-Object -Process` / `-RemainingScripts` | Process, with binder-assigned Begin/End where applicable | Synchronous | OncePerInputObject | current runspace |
 | `ForEach-Object -End` | End | Synchronous | Once | current runspace |
-| `ForEach-Object -Parallel` | Process | Concurrent | OncePerInputObject | child runspace; exit isolated |
+| `ForEach-Object -Parallel` | Process | Concurrent | OncePerInputObject | child runspace; runspace-local exit isolated; process-wide effects conservative |
 | `Where-Object -FilterScript` | Filter | Synchronous | OncePerInputObject | current runspace |
 | in-process `Invoke-Command -ScriptBlock` | Main | Synchronous | Once | child scope unless `-NoNewScope`; shared location |
 | remote/session/SSH/VM/container `Invoke-Command` | Main | proved from complete parameter set | Unknown unless targets are proved | remote/child state; exit isolated |
@@ -540,6 +540,22 @@ The version-pinned PowerShell 7 catalog covers:
 | `Set-PSBreakpoint -Action`, event `-Action` | Action | Deferred | ZeroOrMore | trigger-time state Unknown without proof |
 | `Register-ArgumentCompleter -ScriptBlock` | Completion | Deferred | ZeroOrMore | completion-time state Unknown without proof |
 
+Parallel child runspaces do not inherit ordinary caller variables or aliases,
+and their runspace-local variable and location exit state does not flow into the
+host continuation. They do share process-wide state such as the environment
+provider. A supported or unknown child mutation that may affect such state
+invalidates later host binding, command-resolution, and location facts. It also
+invalidates later child-activation facts even with `-UseNewRunspace`, because a
+fresh runspace is not a fresh process.
+Runspace `global:` variable, function, alias, and location state remains local
+to that runspace and does not by itself invalidate the host. Once child command
+resolution is mutated, however, an exact changed alias or function name is
+retained in bounded case-insensitive state. A later matching invocation whose
+identity is no longer proved is a possible process-wide mutation and receives
+the same conservative invalidation unless its identity is independently proved.
+An ambiguous changed name, wildcard, or candidate-set overflow collapses to all
+unproved command names rather than guessing.
+
 The optional inbox `Microsoft.PowerShell.ThreadJob\Start-ThreadJob` follows
 the initialization/main child-runspace model only when the caller's pinned
 module baseline proves that identity. Otherwise it follows the unknown

openspec/changes/v0-3-structured-shell-analysis/design.md

@@ -374,7 +374,7 @@ PowerShell 7.6.4 probes demonstrate that these are independent dimensions:
 | local `Invoke-Command { ... }` | child scope unless `-NoNewScope` | shared | synchronous / once |
 | `Measure-Command { ... }` / `Trace-Command -Expression { ... }` | shared current scope | shared | synchronous / once |
 | `Start-Job { ... }` | child process state | inherited initial location; exit isolated | concurrent / once |
-| `ForEach-Object -Parallel { ... }` | child runspace state | inherited initial location; exit isolated | concurrent / once per input |
+| `ForEach-Object -Parallel { ... }` | child runspace state; process-wide effects may escape | inherited initial location; runspace-local exit isolated | concurrent / once per input |
 | event, breakpoint, completion actions | trigger-time state | trigger-time state | deferred / zero or more |
 
 The shell-specific analyzer owns inbound state, exit propagation, phase
@@ -383,6 +383,22 @@ Occurrence facts expose the effective result. This keeps the public structural
 API narrow while avoiding the false claim that variables and location always
 share one boundary.
 
+An in-process child runspace is not a process boundary. Ordinary variables,
+aliases, and PowerShell location are runspace-local, but environment-provider
+mutation is process-wide and can affect the host and sibling runspaces. The
+analyzer therefore invalidates later host binding, command-resolution, and
+location facts after any possibly escaping child effect. The same invalidation
+applies to later activations under `-UseNewRunspace`: the switch removes pooled
+runspace-local state, but it does not create a separate process.
+Runspace `global:` variables, functions, aliases, and location remain
+runspace-local and do not themselves poison host facts. Exact alias/function
+names changed inside a child are retained in a bounded, case-insensitive set;
+only a matching subsequent invocation whose identity is not independently
+proved is treated as a possible process-wide mutation. Ambiguous names,
+wildcards, and set overflow collapse to all unproved command names. This
+prevents both an alias to `Set-Item` and a rebound `Set-Alias` mutator from
+hiding an environment-provider write without tainting unrelated names.
+
 `SimpleCommandSyntax.ExecutionRegions` preserves authored script-block order.
 The analyzer separately applies semantic phase order. PowerShell's binder can
 assign Begin, Process, and End roles to multiple `ForEach-Object` blocks even

openspec/changes/v0-3-structured-shell-analysis/specs/bounded-shell-analysis/spec.md

@@ -668,7 +668,19 @@ from the complete parameter set.
 
 `Start-Job` executes initialization before its main block in a child process;
 `ForEach-Object -Parallel` and a proved `Start-ThreadJob` execute in child
-runspaces. Their exit mutation does not flow into the containing continuation.
+runspaces. Runspace-local variable and location exit mutation does not flow into
+the containing continuation. In-process child runspaces share process-wide
+state such as the environment provider, so a possibly escaping mutation SHALL
+invalidate later host binding, command-resolution, and location facts. It SHALL
+also invalidate later child-activation facts under `-UseNewRunspace`, which
+creates a fresh runspace but not a fresh process.
+Runspace `global:` variables, functions, aliases, and location SHALL remain
+runspace-local and SHALL NOT by themselves invalidate host facts. After child
+command resolution is mutated, each exact changed alias or function name SHALL
+be retained in bounded case-insensitive state. A later matching invocation
+whose identity is not independently proved SHALL be treated as a possible
+process-wide mutation. An ambiguous name, wildcard, or candidate-set overflow
+SHALL fail closed to every unproved command name.
 Breakpoint actions, event actions, and argument completers are deferred and
 may execute zero or more times; their trigger-time cwd and mutable state are
 Unknown unless independently proved. Deferred commands remain in the