chore(deps): update fastmcp requirement from >=3.3.1 to >=3.4.0

[dependabot]

Updates the requirements on fastmcp to permit the latest version.

Release notes

Sourced from fastmcp's releases.

v3.4.0: Remote Control

FastMCP 3.4 is about reaching servers that live somewhere else. The headline is fastmcp-remote, a standalone bridge that connects stdio-only MCP hosts to servers hosted over HTTP. Around it, this release hardens the proxy layer those remote connections depend on — making bridges fail loudly instead of silently, and keeping authenticated sessions alive across the long idle periods that remote clients are prone to.

fastmcp-remote

Some MCP hosts still insist on launching a local stdio command, even when the server you want is already running over HTTP. FastMCP could already proxy a remote URL through fastmcp run, but that pulls in the full server-runner surface. fastmcp-remote is the small, single-purpose version: one URL in, one local stdio proxy out.

{
  "mcpServers": {
    "linear": {
      "command": "uvx",
      "args": ["fastmcp-remote", "https://mcp.linear.app/mcp"]
    }
  }
}

OAuth is enabled automatically for HTTPS servers, with support for explicit bearer tokens and custom headers when you need them. The implementation stays on FastMCP primitives — Client, OAuth, create_proxy, and stdio — and credits the original npm mcp-remote project for the command shape.

Bridges That Fail Loudly

Proxies are lazy bridges: they don't touch the upstream server during construction, but they do forward real MCP requests once a client connects. As of 3.4, initialize is part of that forwarded surface — so a proxy only reports a successful handshake after the upstream server initializes too. A missing backend, a wrong URL (the server root instead of /mcp), denied upstream auth, or a non-MCP upstream now fails the downstream initialize instead of producing a "connected" proxy whose capability fetches quietly come back empty. The proxy also forwards ping upstream now.

This is an intentional behavior change from 3.3, and the reason bridge callers like fastmcp-remote surface real upstream failures instead of degrading into empty tool lists.

Auth That Survives Idle Time

Remote sessions sit idle, and short-lived upstream tokens punish that. fastmcp_access_token_expiry_seconds decouples the FastMCP-issued token's lifetime from the upstream expires_in — the FastMCP token is just a reference into proxy storage, re-validated and transparently refreshed on every request, so it can safely outlive a 5-minute upstream token without forcing a full OAuth flow after every idle period. When the upstream issues no refresh token, the lifetime is capped to match.

from fastmcp.server.auth.providers.github import GitHubProvider
auth = GitHubProvider(
client_id="...",
client_secret="...",
base_url="https://your-server.com",
fastmcp_access_token_expiry_seconds=60 * 60 * 24,  # 24h client-facing token
)

Alongside it, token_expiry_threshold_seconds treats tokens as expired N seconds early to close refresh races, and WorkOSProvider gains valid_scopes and extra_authorize_params.

Returnable Tool Errors

A tool could previously only signal an error by raising, which flattens to a text-only result and discards structured content. ToolResult now accepts is_error, mapping to CallToolResult.isError so a tool can hand back a rich error the model can see and act on. The proxy uses this to forward upstream tool errors intact instead of collapsing them.

@mcp.tool
def lookup(id: str) -> ToolResult:
</tr></table> 

... (truncated)

Changelog

Sourced from fastmcp's changelog.

---

title: "Changelog" icon: "list-check" rss: true tag: NEW

v3.4.0: Remote Control

FastMCP 3.4 is about reaching servers that live somewhere else. The headline is fastmcp-remote, a standalone bridge that connects stdio-only MCP hosts to servers hosted over HTTP. Around it, the proxy layer those connections depend on is hardened: a proxy now forwards initialize upstream and fails loudly when the backend is missing or misconfigured, instead of reporting a connected-but-empty proxy. And FastMCP-issued access tokens can now outlive short-lived upstream tokens, so authenticated sessions survive the long idle periods remote clients are prone to.

New Features 🎉

• Add fastmcp-remote bridge package by @​jlowin in #4208

Breaking Changes ⚠️

• Forward proxy initialize as bridge behavior by @​jlowin in #4228

Enhancements ✨

• ci: require external PRs to link a tracked issue by @​strawgate in #4173
• feat: new options --host and --no-log-panel | --log-panel to cli dev apps by @​itaru2622 in #4123
• Add valid_scopes and extra_authorize_params to WorkOSProvider by @​tiagoskaneta in #4135
• Add token_expiry_threshold_seconds for proactive token refresh by @​mohankumarelec in #4142
• Add review-issue skill for triaging gated external contributions by @​jlowin in #4212
• Add contract gate to review-issue skill by @​jlowin in #4214
• Let ToolResult return an error result via is_error by @​jlowin in #4217
• Update published docs after PyPI release by @​jlowin in #4211
• Allow pre-bound HTTP sockets by @​jlowin in #4222
• Add targeted coverage tests by @​strawgate in #4230
• Upgrade ty to 0.0.39 by @​jlowin in #4225
• Decouple FastMCP access token lifetime from upstream expires_in by @​jlowin in #4254

Security 🔒

• feat(code-mode): default sandbox limits and per-execution tool-call cap by @​strawgate in #4170
• Security: Fix 3 findings in GitHub Actions workflows by @​jpr5 in #4183
• Add outbound comment guardrails by @​jlowin in #4196
• Add uv dependency cooldown by @​jlowin in #4213

Fixes 🐞

• fix: VersionSpec eq matching normalizes versions and selects deterministically by @​strawgate in #4058
• fix(tests): hoist azure-identity import out of the OBO test timeout window by @​strawgate in #4176
• fix(auth): disambiguate auth-denied vs missing component messages by @​strawgate in #4165
• fix: preserve annotations, meta, title, icons when creating resources from templates by @​strawgate in #4061
• fix: add OTEL spans to sampling step and tool execution by @​strawgate in #4059
• fix(config): read MCP config files as UTF-8 by @​pragnyanramtha in #4164
• fix(schema): preserve root metadata on fallback by @​yuyua9 in #4178
• fix(proxy): restore _current_server in _restore_request_context by @​strawgate in #4168
• fix(auth): add /.well-known/openid-configuration alias for OAuth server metadata by @​shigechika in #4167
• fix(code-mode): cancel Monty sandbox future on task cancellation by @​strawgate in #4169
• fix(auth): unprefix Azure scopes echoed back to MCP clients by @​rgillinlz in #4130
• fix(cli): forward stateless flag in uv run path by @​yuyua9 in #4177
• fix(ci): scope minimize-reviews concurrency by event name by @​strawgate in #4174
• Fix docs app demo iframe assets by @​jlowin in #4194

... (truncated)

Commits

• e124bde Fix MDX syntax error in changelog (#4270)
• dae11bb Backfill changelog and updates through v3.4.0 (#4269)
• 0f4f78c Fix resource templates with query params on proxied servers (#4251)
• 1a06130 Fix GitHub MCP resource integration test (#4253)
• 58e0f53 Decouple FastMCP access token lifetime from upstream expires_in (#4254)
• 8e66b0a Upgrade ty to 0.0.39 (#4225)
• 53b2016 Close upstream OAuth clients (#4248)
• 989f6f8 docs: add tool fingerprinting recipe for stable schema hashing (#4233)
• 140d96a Forward proxy initialize as bridge behavior (#4228)
• e9848d6 fix: Trendshift link and badge in README.md (#4236)
• Additional commits viewable in compare view

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