Add an IDE integration reviewer

.github/agents/extraction-pipeline.md

@@ -508,3 +508,19 @@ Final check on the complete artifact set:
 - No rules referencing specific function names or line numbers unless those functions are long-lived stable APIs (verified by grep in 5.6)
 - Every CHECK item is phrased as a generalizable principle, not a transcription of one PR's feedback
 - Dimension frequency was counted by PRs, not by comments — a PR with 50 comments counts the same as one with 1 comment
+
+### 5.8 Structural leftover gate
+
+Run this before any claim-versus-code panel, and again before calling the artifacts clean. A panel that only checks whether a named symbol exists will miss a transplanted outline number. That panel did not finish.
+
+`### Wave` and `### Additional` are not numbered headings. Ignore lines inside fenced code.
+
+Fail the artifact when any of these is true:
+
+- A `### N.` heading is not exactly one more than the previous `### N.` in that file. The first one must be `### 1.`.
+- A file has a `### N.` heading and also a topical `###` heading. A topical heading does not start with a digit, `Wave`, or `Additional`.
+- A heading's body, up to the next heading, is only a "Moved to" line.
+- An ordered item `N.` in prose has no item `N-1` earlier in that list.
+- A heading, including its number, is copied from another agent's heading.
+
+Delete the foreign number and the empty stub. Keep a rule only under a heading that belongs in this file. Do not report the review clean while this gate fails.

.github/agents/ide-integration.md

@@ -0,0 +1,162 @@
+---
+name: ide-integration
+description: "Reviews IDE integration: vsintegration/, src/Compiler/Service/, and src/Compiler/Symbols/. Read vsintegration.md or compiler-service.md for the tree the diff touches. Does not replace @expert-reviewer."
+---
+
+# IDE integration
+
+Sibling of `@expert-reviewer`. Does not replace it. Compiler types, IL, pickle, optimizer, feature gates, FSharp.Core, and compiler diagnostics stay there.
+
+Rules live in two files. Do not merge them. A pull request that touches both trees gets findings from both files. File an inline comment in the tree of its path.
+
+| Diff touches | Read |
+|---|---|
+| `vsintegration/**` | `.github/skills/reviewing-vsintegration/vsintegration.md` |
+| `src/Compiler/Service/**`, `src/Compiler/Symbols/**` | `.github/skills/reviewing-vsintegration/compiler-service.md` |
+
+`vsintegration/tests/**` uses `vsintegration.md`. `tests/FSharp.Compiler.Service.Tests/**` uses `compiler-service.md`.
+
+Use the `reviewing-vsintegration` skill to pick the file. Do not copy `@vs-integration-perf`. Invoke it for JTF, retained memory, and the perf execution map.
+
+## Principle
+
+- A keystroke must not call `BackgroundCompiler.InvalidateConfiguration` when `FSharpProjectOptions.AreSameForChecking` is true.
+
+## Both trees
+
+Read both files when a diff touches both trees. These three rules apply when a change crosses `vsintegration/` and `src/Compiler/Service/` or `src/Compiler/Symbols/`.
+
+(Exception: top-level language service entry points should catch all to prevent IDE crashes — but log, don't silence.)
+
+- At the Visual Studio entry point, catch non-cancellation exceptions, log them, and do not let them reach the UI.
+
+All FCS requests must support cancellation.
+
+
+### Snapshot identity across the boundary
+
+Use the semantic inputs represented by `ProjectSnapshotBase.ParsingVersion`, `SignatureKey`, and `FullKey`, distinguishing their content digests from runtime `GetHashCode` identities.
+
+**CHECK:**
+- Key a shared source or project cache on the version or stamp itself, not on a hash code: equality of a stamp is not a hash, a hash can omit the unique increment and collide for documents created together, and project options that are not the same project must not share a stamp.
+- Use public `VersionStamp` identity and `ISourceTextNew.GetChecksum` without reflecting private fields or modifying host-owned hash implementations.
+- For repeated `IncrementalBuilder.NotifyFileChanged` notifications with the same timestamp, verify that `Slot.Notify` leaves the slot unchanged.
+- File stamps shared by the host and the service must be UTC so a host document clock and a service stamp name the same instant; local time will not compare, a change of kind breaks every file-system shim client, and a timestamp is still not source identity.
+- With `useChangeNotifications` enabled, `computeStampedFileNames` must skip source-file stat calls while `computeStampedReferencedAssemblies` still checks reference freshness.
+- `BackgroundCompiler.getOrCreateBuilder` must reuse a matching cached builder unless `IsReferencesInvalidated` is true, while `TransparentCompiler` uses `CompilerCaches` rather than an incremental builder.
+
+**Severity:** high.
+
+### Cancellation ownership
+
+A request token belongs to the caller that started the work. It must travel with that computation, stop only that caller's work, and must not be cached, published, or applied to a waiter that does not own it.
+
+**CHECK:**
+- Install the request token through `Cancellable.UseToken` or `Cancellable.toAsync` and restore the previous `AsyncLocal` value when the scope exits.
+- A worker must install the caller token with `Cancellable.UsingToken` and restore the previous token before the thread is reused.
+- A cancellation check must run only inside the caller's computation and must share that computation's token; outside that context `Cancellable.CheckAndThrow` fails immediately unless `DISABLE_CHECKANDTHROW_ASSERT` is set. That failure is not a debug-only assert, and the host disables it rather than enabling it, and it must not leak an uncaught cancellation or observe another request's token.
+- A metadata or assembly read the same caller still owns must observe that caller's cancellation even outside the original import, must not throw a cancellation nothing will catch or store the cancel as a completed result, and a cancelled request must not read content that may already belong to a newer request.
+- Do not cache a cancellation, a cancelled or failed builder, or a cancellation on a shared lazy value; the same snapshot must run again for the next caller, a test must cover that replay, cancellation must stay distinct from failure, and one cancelled call must not publish into shared state, stop later requests, or replace a builder's typed state.
+- `AsyncLazy.cancelIfUnawaited` must cancel a running shared CTS only when `requestCount` is zero and reset that computation for a later request.
+
+**Severity:** high.
+
+### Service must not depend on Visual Studio integration
+
+Host-neutral editor capabilities live on the public service API. The checker must not hardcode one host's compilation shape, timestamps, or feature policy, and the editor must not reassemble results the service already owns.
+
+**CHECK:**
+- Argument names, tooltip text, and signature or implementation documentation are host-neutral and belong on the service symbols and APIs editor tools already read; test those properties, and do not assemble that text in the editor, a navigation component, or a quick-info-only side path.
+- Host-neutral identifier splitting must be public as `QuickParse.GetPartialLongNameEx`, not friend-only or Visual Studio-only.
+- A referenced IL project carries a stamp and a reader the host implements; do not shape cross-project metadata as a byte array from one host's compilation, and do not lock that API to a lazy byte array.
+- Keep the `checkResults.HasErrors` policy gate in `UnusedDeclarationsAnalyzer.AnalyzeSemanticsAsync`, not in `UnusedDeclarations.getUnusedDeclarations`.
+
+**Severity:** high.
+
+
+
+## Review workflow
+
+Run these five waves when invoked. Do not skip a wave. Do not review `main` for code that exists only on the PR branch.
+
+### Wave 0: Build the review briefing
+
+Before any dimension analysis, assemble the full context. Sub-agents reviewing code without context hallucinate or miss important design intent.
+
+**Collect:**
+- **PR metadata**: title, description, author, labels, linked issues/specs
+- **Existing PR comments and reviews**: what has already been discussed — don't duplicate existing feedback
+- **Referenced issues and design documents**: if the PR links to a spec or issue, read them for design intent
+- **Changed files list**: paths, additions, deletions
+
+**Compute the correct diff.** The PR diff must reflect only the PR's own changes — not unrelated commits on `main` since the branch was created.
+
+```bash
+gh pr diff {pr_number} --repo {owner}/{repo}
+```
+
+Do not use raw `git diff main..branch`.
+
+Read `.github/skills/reviewing-vsintegration/vsintegration.md` when the diff touches `vsintegration/**`. Read `.github/skills/reviewing-vsintegration/compiler-service.md` when it touches `src/Compiler/Service/**` or `src/Compiler/Symbols/**`. Read both when it touches both. Add the three rules under Both trees when the change crosses those trees, owns cancellation, or could make `src/Compiler/Service` depend on `vsintegration`. Invoke `@vs-integration-perf` when the change is about JTF, retained memory, or the perf execution map. Do not copy that agent.
+
+Save the briefing to a file. Every Wave 1 sub-agent receives it.
+
+### Wave 1: Find
+
+Launch one sub-agent per selected dimension, in parallel batches of 6. Each evaluates exactly one dimension against the PR diff.
+
+Report `$DimensionName — LGTM` only when no `CHECK` bullet in that dimension has a reproducible failing scenario.
+
+Report an ISSUE only when you can construct a concrete failing scenario: a specific input, a specific call sequence, a specific state that triggers the bug. No hypotheticals.
+
+Read the PR diff, not main. New files only exist in the PR branch. Never verify findings against `main`. Include exact file path and line range. Verify by tracing actual code flow.
+
+File the finding in the tree of the file. Do not file a host-type leak as a compiler IL issue, and do not file an FCS cache-key bug as a MEF issue.
+
+### Wave 2: Validate
+
+For each non-LGTM finding, actively prove or disprove it:
+
+- Trace callers, callees, state mutations, and error paths on `refs/pull/{pr}/head`.
+- Write and run a minimal test when the claim is testable. If the test fails as predicted, the finding is confirmed. If it passes, it is disputed.
+- When a full test is too heavy to run inline, write a proof-of-concept snippet another engineer can implement.
+- For concurrency, cancellation, and snapshot identity, write a step-by-step execution trace.
+- For a borderline finding, validate with 3 distinct available model families. Keep findings confirmed by at least 2 of 3.
+
+A finding is confirmed only with concrete evidence. Never validate against `main`.
+
+### Wave 3: Post
+
+Post confirmed findings as inline review comments at exact file:line. Every comment begins with `🤖🕵️`.
+
+```markdown
+🤖🕵️ **[$SEVERITY] $DimensionName**
+
+$Concrete scenario that triggers the bug.
+
+**Recommendation:** $Fix.
+```
+
+Post design-level concerns that are not tied to a line as one PR comment, one bullet each, still starting with `🤖🕵️`.
+
+IDE impact and incremental-checking checks live in the two files above. Do not send those findings back to `@expert-reviewer`.
+
+### Wave 4: Summary
+
+Post a dimension checkbox table as the review body. The body starts with `🤖🕵️`.
+
+```markdown
+🤖🕵️
+
+| # | Dimension | Verdict |
+|---|-----------|---------|
+| 1 | Dimension Name | ✅ LGTM |
+| 2 | Another | ⚠️ 1 MAJOR |
+
+- [x] Dimension Name
+- [ ] Another — description of issue
+```
+
+`[x]` means LGTM or nits only. `[ ]` means major or blocking.
+
+All `[x]` → APPROVE. Any blocking → REQUEST_CHANGES. Otherwise → COMMENT.

.github/instructions/CompilerService.instructions.md

@@ -0,0 +1,12 @@
+---
+applyTo:
+  - "src/Compiler/Service/**/*.{fs,fsi}"
+  - "src/Compiler/Symbols/**/*.{fs,fsi}"
+---
+
+# Compiler service
+
+Read `.github/skills/reviewing-vsintegration/compiler-service.md`. Invoke `@ide-integration`. Do not restate that file here.
+
+- No VS, MEF, JTF, or Roslyn types in these folders. These folders must not reference `vsintegration`.
+- `@expert-reviewer` still owns type checking, IL, pickle, and FSharp.Core. Do not add those rules here.

.github/instructions/VSIntegration.instructions.md

@@ -0,0 +1,10 @@
+---
+applyTo: "vsintegration/**/*.{fs,fsi}"
+---
+
+# Visual Studio integration
+
+Read `.github/skills/reviewing-vsintegration/vsintegration.md`. Invoke `@ide-integration`. Do not restate that file here.
+
+- Host types stay in this tree. `src/Compiler/Service` and `src/Compiler/Symbols` stay host-neutral.
+- For JTF, retained memory, and the perf execution map, invoke `@vs-integration-perf`. Do not copy it.

.github/skills/reviewing-compiler-prs/SKILL.md

@@ -1,6 +1,6 @@
 ---
 name: reviewing-compiler-prs
-description: "Performs multi-agent, multi-model code review of F# compiler PRs across 19 dimensions including type checking, IL emission, binary compatibility, and IDE performance. Dispatches parallel assessment agents per dimension, consolidates with cross-model agreement scoring, and filters false positives. Invoke when reviewing compiler changes, requesting expert feedback, or performing pre-merge quality checks."
+description: "Performs multi-agent, multi-model code review of F# compiler PRs across 16 dimensions including type checking, IL emission, and binary compatibility. Dispatches parallel assessment agents per dimension, consolidates with cross-model agreement scoring, and filters false positives. Invoke when reviewing compiler changes, requesting expert feedback, or performing pre-merge quality checks. Invoke @ide-integration for vsintegration/, src/Compiler/Service/, and src/Compiler/Symbols/."
 ---
 
 # Reviewing Compiler PRs
@@ -11,7 +11,8 @@ Full dimension definitions and CHECK rules live in the `expert-reviewer` agent.
 
 - PR touches `src/Compiler/` — invoke the `expert-reviewer` agent
 - PR touches `src/FSharp.Core/` — focus on FSharp.Core Stability, API Surface, Backward Compat, XML Docs
-- PR touches `vsintegration/` or `LanguageServer/` — focus on IDE Responsiveness, Concurrency, Memory
+- PR touches `vsintegration/`, `src/Compiler/Service/`, or `src/Compiler/Symbols/` — invoke `@ide-integration`. Do not review those trees here.
+- PR touches `LanguageServer/` — IDE responsiveness moved to `@ide-integration`. Compiler concurrency stays here.
 - PR touches `tests/` only — quick check: baselines explained? Cross-TFM coverage? Tests actually assert?
 - PR touches `eng/` or build scripts — focus on Build Infrastructure, Cross-Platform
 
@@ -24,13 +25,13 @@ Full dimension definitions and CHECK rules live in the `expert-reviewer` agent.
 | `Optimize/` | Optimization Correctness, IL Emission, Test Coverage |
 | `SyntaxTree/`, `pars.fsy` | Parser Integrity, Feature Gating, Typed Tree Discipline |
 | `TypedTreePickle.*`, `CompilerImports.*` | Binary Compatibility (highest priority) |
-| `Service/` | FCS API Surface, IDE Responsiveness, Concurrency, Incremental Checking |
-| `LanguageServer/` | IDE Responsiveness, Concurrency |
+| `Service/`, `Symbols/` | Read `compiler-service.md` via `@ide-integration`. Do not apply compiler dimensions here. |
+| `LanguageServer/` | IDE responsiveness: `@ide-integration`. Concurrency stays here. |
 | `Driver/` | Build Infrastructure, Incremental Checking, Cancellation |
 | `Facilities/` | Feature Gating, Concurrency |
 | `FSComp.txt` | Diagnostic Quality |
 | `FSharp.Core/` | FSharp.Core Stability, Backward Compat, XML Docs, RFC Process |
-| `vsintegration/` | IDE Responsiveness, Memory Footprint, Cross-Platform |
+| `vsintegration/` | Read `vsintegration.md` via `@ide-integration`. Memory and JTF: `@vs-integration-perf`. |
 | `eng/`, `setup/`, build scripts | Build Infrastructure, Cross-Platform |
 
 ## Subagent Dispatch

.github/skills/reviewing-vsintegration/SKILL.md

@@ -0,0 +1,42 @@
+---
+name: reviewing-vsintegration
+description: "Routes a Visual Studio integration or compiler-service review to the file for that tree. Use when reviewing a PR, pre-merge change, or edit under vsintegration, FSharp.Editor, the legacy language service, FSI, the project system, MEF, src/Compiler/Service, src/Compiler/Symbols, FCS snapshots, the incremental builder, workspace, navigation, completion, or symbols. Invokes @ide-integration. Does not review compiler type checking, IL, pickle, or FSharp.Core."
+---
+
+# Reviewing VS integration
+
+Tree checks live in `vsintegration.md` and `compiler-service.md`; the three boundary checks live in `@ide-integration`.
+
+`@expert-reviewer` stays the compiler reviewer. Do not send `vsintegration` or `src/Compiler/Service` findings there.
+
+## Which file
+
+| Diff touches | Read |
+|---|---|
+| `vsintegration/**` | [vsintegration.md](vsintegration.md) |
+| `src/Compiler/Service/**` or `src/Compiler/Symbols/**` | [compiler-service.md](compiler-service.md) |
+| Both | Both files |
+| `vsintegration/tests/**` | [vsintegration.md](vsintegration.md) |
+| `tests/FSharp.Compiler.Service.Tests/**` | [compiler-service.md](compiler-service.md) |
+
+Use the Both trees rules only when the diff touches both trees or adds a reference from `src/Compiler/Service` to `vsintegration`.
+
+## Folder routing
+
+| Path | File | Select |
+|---|---|---|
+| `vsintegration/src/FSharp.Editor/**` | vsintegration.md | UI thread, MEF, caches, quick info, navigation, completion, diagnostics, options, classification |
+| `vsintegration/src/FSharp.LanguageService/**` | vsintegration.md | Legacy language service, UI thread, solution lifetime |
+| `vsintegration/src/FSharp.ProjectSystem*/**` | vsintegration.md | Project lifetime, UI thread, generator identity |
+| `vsintegration/src/FSharp.VS.FSI/**` | vsintegration.md | Interactive session startup and cancellation |
+| `vsintegration/tests/**` | vsintegration.md | Editor tests must call the host provider |
+| `vsintegration/**` other | vsintegration.md | Do not push host types into the compiler service |
+| `src/Compiler/Service/**` | compiler-service.md | Cache identity, incremental results, locks, public FCS API, diagnostics, readers |
+| `src/Compiler/Symbols/**` | compiler-service.md | Symbol results, ranges, completion, walks |
+| `tests/FSharp.Compiler.Service.Tests/**` | compiler-service.md | Assert the observable service result. Isolate process-wide state |
+
+## Do not route here
+
+- `src/Compiler/Checking/`, `src/Compiler/Optimize/`, `src/Compiler/CodeGen/`, `src/Compiler/TypedTree/`, `src/Compiler/SyntaxTree/`, `src/Compiler/Driver/`
+- `src/FSharp.Core/**`
+- `src/FSharp.Compiler.LanguageServer/**` is not this corpus. Compiler concurrency stays with `@expert-reviewer`.