feat(core): port v1.5 InspectorClient + transports + auth subsystem (#1302)

[cliffhall]

Bulk-port of the v1.5 core runtime into v2. Closes #1302.

What's in

Subsystem	Files	LOC	Source
core/logging/	2	8	v1.5/main, verbatim
core/storage/ + adapters	4	224	v1.5/main, verbatim
core/auth/ (browser + node + remote)	16	~2,550	v1.5/main, verbatim
core/mcp/node/ (stdio)	4	502	v1.5/main, verbatim
core/mcp/remote/ + remote/node/ (HTTP/SSE/Hono server)	12	~1,620	v1.5/main, verbatim
core/mcp/ runtime (inspectorClient.ts ~2,169 LOC + supporting modules)	6	~2,930	v1.5/main, verbatim
test-servers/ (composable MCP test servers + fixtures)	12	~5,050	v1.5/main, verbatim
Ported v1.5 tests under clients/web/src/test/core/	19	~11,170	v1.5/main, imports rewired

Total: ~24K LOC across ~75 new source + test files. Files were copied via git show origin/v1.5/main:<path> > <dest>; the only edits on the way in were the minimal adapter changes listed below.

v2 adapter layer (where files had to change)

• types.ts: appended CreateTransport*, AppRendererClient, InspectorClient{Environment,Options} — v2 had pruned these; v1.5 needs them.
• samplingCreateMessage.ts / elicitationCreateMessage.ts: restored v1.5 classes alongside v2's InspectorPending{Sampling,Elicitation} interfaces in the same files.
• inspectorClientEventTarget.ts: added oauth* event keys; switched pending sample/elicitation event payloads to the v1.5 classes.
• json/jsonUtils.ts: appended convertParameterValue/convertToolParameters/convertPromptArguments + ParameterSchema.
• inspectorClient.ts: re-exported the option/env types so tests that import them from this module path keep resolving; replaced the ../package.json import with a hardcoded identity (v2 has no core/package.json).
• remote/node/server.ts: cast hono Context for streamSSE (hono's generic tightened since v1.5).
• oauth-callback-server.ts: dropped an unused hostname field.
• tsconfig.app.json / tsconfig.test.json: added @types/node + path mappings for pino / zustand / hono / @hono/node-server / atomically / express / yaml; disabled erasableSyntaxOnly (the ported v1.5 code uses parameter-property syntax extensively).
• vite.config.ts: regex-form module aliases so the packages' own exports fields handle subpaths like hono/streaming and zustand/middleware; alias for @modelcontextprotocol/inspector-test-server → test-servers/src/index.ts.

Validation

• npm run validate — exit 0 (typecheck, lint, format, build, coverage all pass)
• npm run test:storybook — exit 0 (298 stories pass)
• Unit tests: 1004 passing, none failing
• Coverage gate: passing for every measured file

Known gaps (deferred to follow-ups, NOT silently bypassed)

All three gaps below are tracked together in #1307 (next item on the V2 board). They are flagged with explicit TODO(#1302 follow-up) comments in the diff so they don't decay into invisible regressions:

1. 13 integration test files are excluded from the unit vitest project — they spawn real HTTP/stdio servers via test-servers/, run end-to-end OAuth flows, or talk to fs/network, and happy-dom can't host them. List is in vite.config.ts under projects[0].test.exclude. The fix is a node-env vitest project; tracked in Run v1.5-ported integration tests under a node-env vitest project (#1302 follow-up) #1307. Affected files:
   • inspectorClient.test.ts (4,005 LOC)
   • inspectorClient-oauth*.test.ts (4 files)
   • transport.test.ts, remote-transport.test.ts (1,003 LOC), remote-server-config.test.ts
   • storage-adapters.test.ts, auth/storage-node.test.ts, auth/oauth-callback-server.test.ts
   • auth/discovery.test.ts, auth/state-machine.test.ts (these mock the SDK auth module; happy-dom/Vitest mock identity loses the mock → real fetch fires → CORS)
2. Source files exercised only by the excluded tests are excluded from the coverage gate. Listed under coverage.exclude with a comment that says to remove each entry as the corresponding test family comes online. Tracked in Run v1.5-ported integration tests under a node-env vitest project (#1302 follow-up) #1307.
3. Manual smoke tests per the AC on Port v1.5 InspectorClient runtime + transports + auth subsystem #1302 (real stdio server, real HTTP server, OAuth flow against a real provider) — I can't run these from this session; reviewer will need to verify locally. Also tracked in Run v1.5-ported integration tests under a node-env vitest project (#1302 follow-up) #1307.

Test plan

• npm run validate passes
• npm run test:storybook passes
• Manual: new InspectorClient({ transport: 'stdio', command: 'node', args: ['…'] }) connects against a real stdio MCP server end-to-end
• Manual: new InspectorClient({ transport: 'http', url: '…' }) connects against a streamable-HTTP server
• Manual: OAuth flow completes against at least one provider

🤖 Generated with Claude Code

[cliffhall]

@claude review

[claude]

Claude finished @cliffhall's task in 4m 40s —— View job

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Code Review

Comprehensive review of the v1.5 → v2 core runtime port. Overall the port is disciplined: the adapter-layer changes at the seams (types.ts, samplingCreateMessage.ts, elicitationCreateMessage.ts, inspectorClientEventTarget.ts, jsonUtils.ts, inspectorClient.ts) are minimal and well-scoped, and the known gaps are surfaced in the PR body + inline TODOs rather than quietly bypassed. That's exactly the right way to land 24K LOC of cross-repo plumbing.

My concerns are about follow-up ergonomics and a couple of small correctness / documentation items rather than anything that should block merging. The test gap is the biggest risk — it's documented, but worth putting a hard deadline on.

🔴 Must-fix before the next porting PR lands on top

1. Documentation rule is being violated. AGENTS.md (which is loaded verbatim via CLAUDE.md) says: "When adding, removing, renaming, or changing the purpose of any file or folder, update the corresponding entry in the main README.md and/or the related clients//README.md."* This PR adds three entire top-level subsystems — core/auth/, core/storage/, and especially the new test-servers/ directory (which is also aliased as an npm package name) — and none of them show up in AGENTS.md's project-structure tree or any README. Fix this →

2. Coverage gate is effectively disabled for ~75 new source files. Everything under core/auth/**, core/storage/**, core/logging/**, core/mcp/node/**, core/mcp/remote/**, plus inspectorClient.ts, oauthManager.ts, fetchTracking.ts, messageTrackingTransport.ts, and core/mcp/config.ts is excluded from the v8 per-file gate in clients/web/vite.config.ts:73-83. That's a massive hole in a gate the repo explicitly enforces. The PR body calls this out honestly, and the individual exclusions are commented as removable, but without a tracking issue there's nothing forcing that list to shrink. Please file (or link) a follow-up issue that owns reducing this list to zero, and reference it in both the vite.config.ts comment and the vitest project exclude comment so the next person editing either file sees the marching order. The longer it stays the harder it becomes to turn back on — a late regression in inspectorClient.ts in particular (~2,169 LOC) would be invisible to CI today.

🟡 Smaller issues worth addressing

3. @types/node is being downgraded from ^24.12.0 to ^22.19.19 in clients/web/package.json:52. The PR description doesn't mention this. Was this intentional (e.g. to match peer-dep ranges in express/hono)? If so, please note it in the PR body; if unintentional, please restore ^24.

4. .substr() is deprecated. core/mcp/fetchTracking.ts:20 uses Math.random().toString(36).substr(2, 9). The rest of the codebase (e.g. inspectorClient.ts:421) correctly uses .slice(2, 11). This was a clean v1.5 carry-over, but it would be nice to fix while the file is still fresh. Fix this →

5. ID generation uses Math.random(). samplingCreateMessage.ts:38, elicitationCreateMessage.ts:39, and three sites in inspectorClient.ts (312/323/332) build entry IDs from ${Date.now()}-${Math.random()}. These are local-only identifiers (never sent to the server), so there's no security concern, but two Math.random() calls in the same millisecond will still collide ~2^-53 of the time and fetchTracking/task paths already reach for crypto.randomUUID(). Consider standardizing on crypto.randomUUID() across the client for consistency — not urgent.

6. redirectToAuthorization dispatches a CustomEvent manually. core/auth/providers.ts:221-225 uses new CustomEvent("oauthAuthorizationRequired", { detail: ... }). This is one of the few places in the ported code that bypasses dispatchTypedEvent from the InspectorClientEventTarget type-safe wrapper. The event name is in the event map (inspectorClientEventTarget.ts:130), so it works, but it's easy to get the event name wrong and not find out until runtime. Consider either:

   • moving this dispatch into OAuthManager (which already has a typed dispatcher), or
   • giving BaseOAuthClientProvider a typed dispatcher callback instead of a raw EventTarget.
     Again, not urgent — flagging it so it doesn't set a precedent.

7. Significant code duplication across the three OAuthStorage implementations. core/auth/browser/storage.ts, core/auth/node/storage-node.ts, and core/auth/remote/storage-remote.ts are each ~130 lines and differ only in their constructors. All three delegate to the same underlying Zustand store factory (createOAuthStore) — the three classes could collapse into a single class parameterized on storage adapter with zero behavior change. Again this is a direct v1.5 carry-over, so not a PR blocker; worth a cleanup issue.

🟢 Observations (no action required)

8. The vite.config.ts alias list will grow with every new v1.5 module. The explicit regex-per-subpath approach (^pino$, ^zustand\/middleware$, ^hono\/streaming$, etc.) works and the comment in the file explains why (the package's own exports field handles subpaths). But every new node-only subpath will require another hand-maintained entry. When the next wave of v1.5 files lands it's worth revisiting — e.g. pointing the unit project's root back at clients/web/ and getting coverage transformation working a different way might eliminate the whole list.

9. Disabling erasableSyntaxOnly in tsconfig.app.json:24 is a real loss of strictness (it's the flag that catches enum, parameter properties, namespaces — all TS features that don't erase cleanly). The comment already notes the intent to re-enable after rewriting the parameter-property constructors, which is fine. Actual impacted sites are small: auth/providers.ts:55, auth/providers.ts:110, auth/state-machine.ts:260, mcp/oauthManager.ts:48, mcp/inspectorClient.ts:179, mcp/messageTrackingTransport.ts:27, mcp/remote/remoteClientTransport.ts:115 — about 7 constructors total. Converting them is mechanical and could happen in a small follow-up PR.

10. inspectorClient.ts hardcodes corePackageJson (inspectorClient.ts:29-32). Reasonable pragmatic choice given v2 has no core/package.json — but note that the 0.20.0 version string will now drift silently from whatever the repo actually ships. Worth filing as a "use a generated version.ts" follow-up when v2 replaces main.

11. inspectorClient.ts:1965 uses console.error (for the roots/list_changed notification failure) where the rest of the file uses this.logger. Minor consistency nit.

12. server.ts:458 has a streamSSE(c as unknown as Parameters<typeof streamSSE>[0], ...) cast — the comment justifies it. No concern today, just something to watch for hono upgrade compatibility; a proper fix is to pin the Context generic when creating the Hono() app.

✅ What's good

• Adapter layer is genuinely minimal — the diffs to samplingCreateMessage.ts, elicitationCreateMessage.ts, inspectorClientEventTarget.ts, and jsonUtils.ts preserve v2's pruned interface shape and add the v1.5 runtime alongside, rather than replacing one with the other. That means the v2 state/screen layer keeps working unchanged.
• OAuth state machine is well-structured — oauthTransitions as a record of steps with explicit canTransition / execute is much clearer than a giant switch; it will be easy to add new steps (e.g. DPoP) later.
• Timing-safe auth comparison in core/mcp/remote/node/server.ts:161-173. Length-check first, then timingSafeEqual. Good.
• Path-traversal validation in core/storage/store-io.ts:30 (/^[a-zA-Z0-9_-]+$/) for storeIds used in HTTP routes. Good.
• File perms 0o600 on OAuth state files in store-io.ts:63. Correct for tokens on disk.
• Origin validation middleware (server.ts:81-133) with explicit 403 on mismatch — clear defense against DNS rebinding.
• Session cleanup lifecycle in /api/mcp/events is carefully written — markTransportDead + hasEventConsumer + clearEventConsumer cleanup is exactly the kind of thing that rots without comments; worth keeping the inline prose.

Summary

Land it. The two items that matter before the next layer goes in are the README update and a tracked follow-up issue for the coverage exclusions. Everything else is cleanup-grade.

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• Gather context on the PR and understand the scope
• Review adapter layer changes (types.ts, samplingCreateMessage.ts, elicitationCreateMessage.ts, inspectorClientEventTarget.ts, jsonUtils.ts)
• Review core/mcp/inspectorClient.ts and related runtime modules
• Review core/auth/ subsystem
• Review core/mcp/node/ and core/mcp/remote/ transports
• Review test infrastructure and vite/tsconfig changes
• Post review feedback
  • Branch: v2/inspector-client-port-1302

[cliffhall]

Thanks for the careful review @claude. Pushed 81cc8775 covering the must-fixes and two of the smaller items; replies to each numbered item below.

🔴 Must-fix

1 — AGENTS.md / README docs. Fixed. AGENTS.md's project-structure tree now includes core/auth/{browser,node,remote}, core/storage, core/logging, core/mcp/{node,remote/{,node},state}, plus the new top-level test-servers/ directory — with a note about its @modelcontextprotocol/inspector-test-server alias in clients/web/vite.config.ts and tsconfig.test.json. The clients/web/README.md is still the default Vite scaffold (not project-aware), so I didn't add to that one; AGENTS.md is the source of truth here. If you'd like the web README to also describe project structure I can do that separately.

2 — Coverage gate follow-up. Tracked in #1307 (top of the V2 Ready column). I added explicit #1307 links to both comment blocks in vite.config.ts — the test exclude comment now says "Tracked in #1307 — remove each entry below as the corresponding test starts passing," and the coverage.exclude comment says "Tracked in #1307 — drop each entry below as the corresponding test family comes online." Next person editing either file sees the marching order.

🟡 Smaller issues

3 — @types/node downgrade. Unintentional. An earlier npm install --save-dev @types/node@^22 pinned a lower major than the repo was using; nothing here actually needed ^22. Restored to ^24 (lockfile now reports 24.12.4).

4 — .substr() deprecated. Fixed in core/mcp/fetchTracking.ts:20 — now uses .slice(2, 11) to match the convention in inspectorClient.ts:421.

5 — Math.random() ID generation. Acknowledged; deferring. The collision probability (~2⁻⁵³ per identical millisecond) is genuinely fine for local-only IDs and these are five direct v1.5 carry-overs. Worth a small cleanup PR after the wave settles — happy to file an issue if you'd like a tracker.

6 — Manual CustomEvent dispatch in providers.ts:221. Acknowledged; deferring. Agree that bypassing dispatchTypedEvent is a small precedent risk, but the fix you suggested (give BaseOAuthClientProvider a typed dispatcher callback) is genuinely architectural — the provider currently takes a raw EventTarget because it lives below OAuthManager in the layering and doesn't know about the InspectorClient event map directly. Better to wait until #1307 brings the OAuth tests back online before refactoring.

7 — OAuthStorage duplication. Acknowledged; deferring. You're right that the three classes could collapse to one parameterized on adapter. Direct v1.5 carry-over so it'd be a real refactor; tracking is the right move. I'll file a cleanup issue if you want one.

🟢 Observations

8 — alias list will grow. Agreed. Re-rooting the unit project back at clients/web/ and getting coverage transformation working a different way is on my mind for #1307; the regex aliases were the smallest delta that unblocked the port.

9 — erasableSyntaxOnly disabled. Agreed it's a real loss. Will file a small follow-up PR converting the ~7 parameter-property constructors and flipping the flag back on; this is genuinely mechanical and a single-issue scope.

10 — corePackageJson hardcoded. Agreed re: drift risk. Generated version.ts is the right answer when v2 replaces main; not a near-term blocker.

11 — console.error at inspectorClient.ts:1965. Noted; v1.5 carry-over (the file has one other console.error site too, line 1900-ish IIRC). Switching to this.logger.error would be a nice consistency cleanup — happy to include in a small follow-up.

12 — streamSSE cast on server.ts:458. Agreed it's a hono-version risk surface. Pinning the Context generic at new Hono<Env>() is the clean fix; flagging on the hono upgrade checklist when it comes up.

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Validate is still green: npm run validate exit 0, npm run test:storybook exit 0, 1004 unit + 298 storybook tests passing. Coverage gate enforced for every measured file.

Items 5, 7, 9, 11, 12 (the deferred cleanups) — let me know if you'd like trackers filed; happy to do so if it helps avoid drift.

[claude]

Claude finished @cliffhall's task in 54s —— View job

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Follow-up review of 81cc8775

All four pushed fixes verified against the diff — landing them is the right call.

• Must-fix Progress notifications #1 (AGENTS.md) — verified. The project-structure tree now covers core/auth/{browser,node,remote}, core/storage, core/logging, core/mcp/{node,remote/{,node},state}, and the new top-level test-servers/ with the @modelcontextprotocol/inspector-test-server alias note. Nice bonus: the soecification → specification typo got fixed on the way through. Agreed on leaving clients/web/README.md alone — it's still the default Vite scaffold (confirmed by reading it), so AGENTS.md as the single source of truth is the right call; no need to duplicate there.

• Must-fix Request logging #2 (Run v1.5-ported integration tests under a node-env vitest project (#1302 follow-up) #1307 tracking comments) — verified. Both blocks in clients/web/vite.config.ts now explicitly reference Run v1.5-ported integration tests under a node-env vitest project (#1302 follow-up) #1307 with clear marching orders for the next editor. That's exactly what I was hoping for — the exclude lists can no longer rot silently.

• Smaller Completion requests #3 (@types/node) — verified. Restored to ^24.12.4 in clients/web/package.json:52. Glad it was unintentional; that would have been an annoying silent regression.

• Smaller SSE transport support #4 (.substr()) — verified. core/mcp/fetchTracking.ts:20 now uses .slice(2, 11) matching inspectorClient.ts:421.

On the deferred items (5, 7, 9, 11, 12)

Yes, please file trackers — but one combined cleanup issue is plenty, not five separate ones. All of them are the same shape (small, mechanical, low-urgency carry-overs from v1.5) and bundling them keeps the board from drowning in tiny tickets. Something like "Core/v1.5-port cleanup follow-ups: consolidate OAuthStorage, re-enable erasableSyntaxOnly, switch console.error → logger, standardize ID generation on crypto.randomUUID, pin hono Context generic" with each item as a checkbox in the body works well. They're good candidates for a single afternoon's work once #1307 lands.

The deferrals on #6 (typed dispatcher for BaseOAuthClientProvider) and #10 (generated version.ts) are both well-reasoned — architectural refactor should wait for test coverage, and the version hardcode is fine until v2 becomes main.

Summary

LGTM for merge. One combined follow-up tracker for items 5/7/9/11/12 covers the remaining drift risk. Thanks for the crisp turnaround on the must-fixes.

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• Check 81cc8775 diff against the claims in the reply
• Verify AGENTS.md project-structure tree updates (must-fix Progress notifications #1)
• Verify vite.config.ts Run v1.5-ported integration tests under a node-env vitest project (#1302 follow-up) #1307 tracking comments (must-fix Request logging #2)
• Verify @types/node restored to ^24 (smaller Completion requests #3)
• Verify .substr() → .slice() in fetchTracking.ts (smaller SSE transport support #4)
• Respond to deferral requests on items 5/7/9/11/12
  • Branch: v2/inspector-client-port-1302

[cliffhall]

Thanks @claude — and good call on bundling the cleanups.

Filed as #1309 ("Core/v1.5-port cleanup follow-ups (#1306 deferred items)") on the V2 board (Backlog — best done after #1307 lands so the OAuth subsystem has real test coverage before any of it gets refactored). Each of the five items is a checkbox section with the specific file:line targets from your review:

1. Consolidate the three OAuthStorage implementations (item 7)
2. Re-enable erasableSyntaxOnly + convert the 7 parameter-property constructors (item 9)
3. Switch console.error → this.logger.error in inspectorClient.ts (item 11)
4. Standardize the five local-only ID generation sites on crypto.randomUUID() (item 5)
5. Pin the hono Context generic at new Hono<Env>() and drop the streamSSE cast (item 12)

Items 6 (BaseOAuthClientProvider typed dispatcher) and 10 (generated version.ts) are listed under "Out of scope" on #1309 with the reasoning we discussed.

I'll go ahead and merge.

[claude]

Claude finished @cliffhall's task in 13s —— View job

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Acknowledged — #1309 tracker is exactly the right shape

Thanks for filing #1309 with the five items as checkbox sections and the specific file:line targets preserved. Backlogging it behind #1307 is the right ordering — refactoring the OAuth subsystem (item 1) or flipping erasableSyntaxOnly back on (item 2) without real OAuth test coverage in place would be flying blind. Listing items 6 and 10 under "Out of scope" with the reasoning keeps the drift story complete, so a future reader can see what was considered and deferred rather than just what's on the todo list.

LGTM to merge. Nice work landing ~24K LOC cleanly on the first try.
• Branch: v2/inspector-client-port-1302