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50b1f95e79 fix(tool-gateway): keep MCP connection healthy on oversized/malformed responses (#15462)
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## Thinking Path

> - Paperclip is the open source app people use to manage AI agents for
work
> - Agents call remote MCP tools through the Paperclip tool gateway
> - The gateway keeps a health status for each remote MCP connection,
and it hides the tools of a connection that has `healthStatus = "error"`
> - One oversized, malformed, or invalid-JSON `tools/call` reply set the
whole connection to `error`
> - Health goes back to `ok` only after a successful call, but the
hidden tools prevent that call, so the connection stayed locked until a
person reconnected it
> - This pull request makes these reply errors fail only the one call,
and it starts a new MCP session for the caller on the next call
> - The benefit is that one large or bad reply no longer disconnects a
working connection for every agent

## Linked Issues or Issue Description

No public issue exists. Related open PRs fix other health downgrades in
the same function. They do not overlap with this change:

- Refs #11910 (timeouts and JSON-RPC errors)
- Refs #15325 (transport errors)

**What happened?**

An agent called a remote MCP tool that returned more than
`MAX_REMOTE_MCP_RESPONSE_BYTES` (1 MB). The gateway returned 502
`mcp_remote_response_too_large`. It also set the connection to
`healthStatus = "error"`. Then `connectedMcpConnectionFilter` hid all
tools of the connection (except `per_user` connections), and
`connections_search` showed the connection as `needs_user_action`. The
`malformed_response` and `invalid_json` errors from
`readMcpHttpResponse` did the same thing.

`readMcpHttpResponse` can also cancel the reply stream before the end.
The remote server can then close its MCP session. The gateway kept the
cached `mcp-session-id` for up to 30 minutes and cleared it only after a
404. The next calls then failed with "Remote MCP session expired".

**Expected behavior**

A reply that is too large or not correct fails only that call. The
connection stays healthy, and its tools stay visible. The next call uses
a new MCP session.

**Steps to reproduce**

1. Add a remote MCP connection with `mcpSessionRequired: true`.
2. Call a tool that returns a reply larger than 1 MB.
3. Look at the connection: `healthStatus` is `error`.
4. Start a new gateway session: the tools of the connection are not in
the list.

**Paperclip version or commit**

`master` at `99a9de9940bf5974352d9dbfbb2f21e62e89689f`

**Deployment mode**

All modes. The fault is in the server tool gateway.

## What Changed

- `server/src/services/tool-gateway.ts`: `too_large`,
`malformed_response`, and `invalid_json` from `readMcpHttpResponse` now
fail only the call. The caller gets the same 502 reason code as before.
The gateway does not call `markRemoteConnectionHealth(…, "error")` for
these errors. The `invalid_json` branch after `JSON.parse(body)` also
does not change health now, so all `invalid_json` paths are the same.
- The `mcp_remote_response_too_large` message now tells the caller to
request a smaller result, for example a narrower query or a smaller page
size. The error details now include `maxBytes`.
- `server/src/services/mcp-http.ts`: new `forgetMcpHttpSession()`. It
removes only the cached session for one scope and one credential set,
and only while that entry still holds the session ID that failed. It
does not touch other agents, sessions that are initializing, or a newer
session that replaced the failed one.
- The gateway calls `forgetMcpHttpSession()` after these reply errors,
so the next call from that caller initializes a new session. The
existing 404 "session expired" path now uses the same function. Before,
both paths cleared all sessions and all pending initializations on the
connection. That made a concurrent initialization by another agent fail
with "MCP connection changed while initializing", which the gateway
reported as a fetch failure and marked as a connection `error`.
- `forgetMcpHttpSessions(connectionId)` is not changed. Disconnect and
revocation still clear the full connection.

Why `malformed_response` and `invalid_json` are also per-call errors:

- Each error is about one reply body. The server was reachable, accepted
the credentials, and sent HTTP 2xx. A reply can be too large or bad
because of the tool and its arguments. That is not a fault of the
connection.
- The other malformed-reply checks in the same function (payload is not
an object, or has no `result`) already throw
`remote_mcp_malformed_response` and do not change health. Only the
reader-level errors changed health.
- Health recovers only after a successful call. An `error` status for
one bad reply therefore locks the connection until a person reconnects
it.
- Other failures (HTTP errors, fetch failures, timeouts, JSON-RPC
errors) still change health. This PR does not change them. #11910 and
#15325 address some of them.

## Verification

- `server/src/__tests__/tool-gateway.test.ts`: the recovery test now
runs for three replies: oversized, invalid JSON, and a reply without the
requested message ID. Each run uses a fake HTTP MCP server with
`mcpSessionRequired: true` that gives `session-N` for each `initialize`.
Each run checks that:
- the call fails with the correct 502 reason code (and, for the
oversized reply, the smaller-page hint and `maxBytes: 1000000`)
  - `healthStatus` stays `ok`
  - a new gateway session still lists the tool and can call it
  - the second `tools/call` uses `session-2`, not `session-1`
- New test: agent A gets an oversized reply while agent B initializes a
session on the same connection. Agent B's call completes, health stays
`ok`, and the two calls use `session-1` and `session-2`. With the old
connection-wide reset, this test fails: agent B gets 502
`mcp_remote_fetch_failed`.
- `server/src/__tests__/remote-mcp-protocol.test.ts`: new unit test.
`forgetMcpHttpSession()` keeps the session of a different identity, and
a late failure from an old session does not remove the newer session.
- Each regression check fails without its fix. Without the health
change, the test fails on `healthStatus: 'error'`. Without the session
reset, it fails with `['session-1', 'session-1']`.

```
cd server
npx vitest run src/__tests__/tool-gateway.test.ts src/__tests__/tool-gateway-service.test.ts src/__tests__/remote-mcp-protocol.test.ts
 Test Files  3 passed (3)
      Tests  132 passed (132)
```

- I did not run the full server `tsc --noEmit` locally because the
sandbox does not have sufficient memory. The CI typecheck covers it.

## Risks

- Low risk. The change affects only the error path of remote MCP
`tools/call`.
- A remote server that always sends bad replies now keeps `healthStatus
= "ok"`. Each call still fails with a clear 502 reason code and an audit
record, so the failure stays visible. Only the connection-wide hiding of
tools stops.
- After one of these errors, the next call from the same caller sends
one more `initialize` request. This adds one round trip.
- A 404 "session expired" now clears only the session of the caller that
got the 404. Before, it cleared the cached sessions of all agents on the
connection. If the remote server restarts, each agent now gets its own
"session expired" error one time and then initializes again. A 404 is
about one session, and the old connection-wide clear also cancelled
other agents' initializations.
- #11910 and #15325 change the same catch block. The PR that merges last
can have a small merge conflict.

> For core feature work, check [`ROADMAP.md`](ROADMAP.md) first and
discuss it in `#dev` before opening the PR. Feature PRs that overlap
with planned core work may need to be redirected — check the roadmap
first. See `CONTRIBUTING.md`.

## Model Used

- Claude Opus 5.5 (Anthropic), model ID `claude-opus-5-5`, 1M-token
context window.
- Run as an agent in Claude Code with tool use (shell, file edit, and
local test runs).

## Checklist

- [x] I have included a thinking path that traces from project context
to this change
- [x] I have specified the model used (with version and capability
details)
- [x] I have checked ROADMAP.md and confirmed this PR does not duplicate
planned core work
- [x] I have searched GitHub for duplicate or related PRs and linked
them above
- [x] I have either (a) linked existing issues with `Fixes: #` / `Closes
#` / `Refs #` OR (b) described the issue in-PR following the relevant
issue template
- [x] I have not referenced internal/instance-local Paperclip issues or
links (only public GitHub `#NNN` / `github.com/paperclipai/paperclip`
URLs)
- [x] My branch name describes the change (e.g. `docs/...`, `fix/...`)
and contains no internal Paperclip ticket id or instance-derived details
- [x] I have run tests locally and they pass
- [x] I have added or updated tests where applicable
- [x] I have updated relevant documentation to reflect my changes (no
user-facing documentation changes are necessary)
- [x] I have considered and documented any risks above
- [ ] All Paperclip CI gates are green
- [ ] Greptile is 5/5 with no open P2s, recommendations, or follow-ups
- [x] I will address all Greptile and reviewer comments before
requesting merge

This PR replaces #15418. It keeps the same commits on a branch name
without an internal ticket ID, and adds a fix for the Greptile review on
#15418.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

---------

Co-authored-by: devinfoley <139239+devinfoley@users.noreply.github.com>
Co-authored-by: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
2026-10-07 12:48:01 -07:00
DottaandPaperclip e8c8ba3c19 feat(apps): add experimental MCP aggregator connectors (#13755)
## Thinking Path

> - Paperclip is the open source app people use to manage AI agents for
work.
> - Its tool gateway applies company access rules and approval controls
to connected apps.
> - MCP aggregators expose many apps through one provider endpoint.
> - Each aggregator needs its own credential, catalog, grants, and
lifecycle in Paperclip.
> - This pull request adds independent Zapier, Arcade, Composio Connect,
and Executor setup with a common Access → Connect layout.
> - A default-off MCP aggregators flag lets operators opt in while we
complete provider acceptance tests.
> - Agents use the normal Paperclip permissions, Test screen, and
gateway after setup.

## Linked Issues or Issue Description

**Subsystem affected**

Apps, connection setup, shared contracts, and the remote MCP gateway.

**Problem or motivation**

Aggregator endpoints need clear provider setup and correct MCP sessions.
Generic setup does not explain each provider's authentication or broad
execution tools. Provider approval must preserve the original execution
instead of replaying a write.

**Proposed solution**

Add four separate connectors behind Settings → Experimental → MCP
aggregators. Start with human and agent access, then connect the
endpoint and read its tools. Enable tools by default. Use the existing
Permissions and Test screens after setup. Keep legacy Composio API-key
and child connections intact.

**Alternatives considered**

A shared connection for all providers would mix credentials and access
rules. Separate provider-specific permission and test screens would
duplicate existing controls. Vercel Connect is outside this change.

**Roadmap alignment**

Extends the existing MCP Tool Gateway & Apps capability and the
Connected Apps roadmap area. This work was requested and reviewed by the
maintainer.

Related work: #11894, #12630, #12632, #12634, and #12906 concern the
legacy Composio broker. #13102 also covers remote MCP pagination. This
change preserves the broker path and adds initialized sessions, response
matching, and provider resume handling alongside pagination.

## What Changed

- Add branded setup and interactive Storybooks for Zapier, Arcade,
Composio Connect, and Executor. Use the existing access controls and
normal action tests. Do not request a connection name or action choices
during setup.
- Add the default-off `enableMcpAggregators` flag to settings, managed
feature metadata, the catalog, and setup guards. Hidden connections keep
running. Legacy Composio connections remain unchanged.
- Reuse the vault, grants, policy, and catalog models. Support OAuth
discovery, bearer tokens, custom headers, and credential-bearing URLs.
Add no database tables or migrations.
- Initialize and retain Streamable HTTP sessions by connection and
effective credentials. Read paginated catalogs and match streaming
responses to request IDs.
- Classify unfamiliar aggregator tools as writes despite upstream
read-only hints; only exact reviewed read capabilities enter the
read-only allowlist. Legacy Composio child behavior is preserved.
- Preserve provider authorization links and execution IDs. Support
Executor approve/resume, decline, and cancel without automatic replay of
uncertain writes.
- Preserve Off and Ask first choices during refresh and reconnect. Allow
new tools and retire removed tools. Keep agent access updates atomic and
preserve an empty agent selection.
- Document connector UX rules, provider branding sources, and live
acceptance results.
- Stabilize the existing Sentry release fixture after its repeated CI
failure by reusing one module mock; production Sentry behavior is
unchanged.

## Verification

- Final head `d11781970`: [CI
run](https://github.com/paperclipai/paperclip/actions/runs/35633534900)
passed, including broad typecheck, test shards, build, and E2E. All 54
checks pass; 2 optional checks are skipped. Greptile is 5/5, Security
Scan passes, and all review threads are resolved.

- Passed 27 focused connector Vitest checks and 18 connector-only
Storybook browser checks before the flag change. All 85 stories rendered
at desktop and narrow widths.
- Passed 5 connector lifecycle/server checks and 7 selected flag checks
after adding the flag. The latter cover settings, managed defaults,
cached catalog visibility, and all four setup routes.
- Review fixes passed 13 risk/handoff/lifecycle checks, dedicated
session-expiration and transport regressions, 13 selected
connector/gateway CI cases, and 10 selected setup/reconnect UI cases. A
real Composio connection-list call also succeeded through the refreshed
UI on `9ab115f71`.
- UI and server TypeScript checks passed. UI build, Storybook build,
token gates, and diff whitespace checks passed during implementation.
- Real browser and real Paperclip agent tests passed for Arcade,
Composio, and Executor. Tested action permissions, denied agent access,
reconnect, disconnect, and isolation. Tested Arcade catalog
additions/removal and Executor provider approve/resume, decline, and
cancel.
- Zapier live acceptance is incomplete. Its dedicated provider server is
configured, but its credential-copy dialog returned an empty clipboard
through browser automation. No live Zapier action is claimed.
- The three isolated Sentry release cases pass after the CI fixture fix.
- Local verification is deliberately narrow at the maintainer's request.
The full local suite, recursive typecheck, and repository-wide build
were not run. CI provides the broader checks.

## Risks

- Shared MCP transport changes affect other remote MCP servers. Protocol
fixtures cover initialized sessions, streaming response matching,
pagination, and isolation.
- Broad execution tools remain broad permissions. The provider governs
actions inside those tools.
- Provider handoff links are retained briefly in memory. After a server
restart, a one-time link may require reopening the provider dashboard.
Paperclip does not replay the original call.
- Zapier remains unproven live. Custom-header imports and self-hosted
endpoints have fixture coverage rather than a separate live account for
every variant.
- Turning the experimental flag off hides setup; it does not revoke
existing credentials or stop existing connections.

## Model Used

OpenAI GPT-6 through Codex, with reasoning, repository tools, shell
execution, and browser automation. The exact runtime model ID and
context-window size are not exposed in this session. A separate
Anthropic-backed Paperclip agent performed live gateway acceptance
tasks.

## Checklist

- [x] I have included a thinking path that traces from project context
to this change
- [x] I have specified the model used (with version and capability
details)
- [x] I have checked ROADMAP.md and confirmed this PR does not duplicate
planned core work
- [x] I have searched GitHub for duplicate or related PRs and linked
them above
- [x] I have either (a) linked existing issues with `Fixes: #` / `Closes
#` / `Refs #` OR (b) described the issue in-PR following the relevant
issue template
- [x] I have not referenced internal/instance-local Paperclip issues or
links (only public GitHub `#NNN` / `github.com/paperclipai/paperclip`
URLs)
- [x] My branch name describes the change (e.g. `docs/...`, `fix/...`)
and contains no internal Paperclip ticket id or instance-derived details
- [x] I have run tests locally and they pass
- [x] I have added or updated tests where applicable
- [x] I have updated relevant documentation to reflect my changes
- [x] I have considered and documented any risks above
- [x] All Paperclip CI gates are green
- [x] Greptile is 5/5 with no open P2s, recommendations, or follow-ups
- [x] I will address all Greptile and reviewer comments before
requesting merge

---------

Co-authored-by: Paperclip <noreply@paperclip.ing>
2026-09-21 12:53:11 -05:00