PR #27096: fix(ui): coerce MCP cost values defensively before .toFixed (closes #27095)

• Repository: BerriAI/litellm
• Author: Booyaka101
• State: open | merged: False
• Link: https://github.com/BerriAI/litellm/pull/27096

Description (problem / solution / changelog)

Summary

The MCP server settings view crashed with Uncaught TypeError: e.default_cost_per_query.toFixed is not a function whenever mcp_info.mcp_server_cost_info.default_cost_per_query (or any per-tool cost) landed in the JSONB column as a string instead of a number. Reported with full root-cause in #27095.

This PR coerces cost values defensively at every .toFixed(...) site in the two affected components, so one malformed value no longer blocks the whole settings page.

Why the crash happens

• MCPServerCostInfo is a TypedDict (litellm/types/mcp.py) — no runtime validation, so the JSONB column round-trips whatever is written, including strings.
• antd's InputNumber onChange real signature is (number | string | null) => void; the local handler in mcp_server_cost_config.tsx types it as (number | null) and writes the raw value, so the UI itself can persist a string.
• Other write paths (YAML/JSON config import, direct API call, hand-edited DB rows) can also land non-numeric values.
• Display components called .toFixed(4) directly, so one malformed cost crashed the whole page.

Fix

Add a small shared toFiniteNumber helper in src/utils/numberUtils.ts (per CLAUDE.md: "Shared utility functions belong in src/utils/"), and use it before every .toFixed(...) callsite in the two components — five total:

• mcp_server_cost_display.tsx — default cost render (line 38), per-tool cost render (line 52), default cost in summary (line 67)
• mcp_server_cost_config.tsx — default cost in summary (line 140), per-tool cost in summary (line 149)

Non-numeric / non-finite inputs (including stringified gibberish, NaN, Infinity, null, undefined, objects) coerce to null; the corresponding row is skipped instead of crashing.

Tests

8 new vitest cases in numberUtils.test.ts cover finite/non-finite numbers, parseable/unparseable strings, whitespace-only strings, null/undefined, and non-string/non-number values. The last case is an explicit regression test for #27095:

it("regression for litellm#27095: stringified cost survives without crashing", () => {
  const stringifiedCost = "0.005";
  const coerced = toFiniteNumber(stringifiedCost);
  expect(coerced).not.toBeNull();
  expect(coerced!.toFixed(4)).toBe("0.0050");
});

$ npx vitest run src/utils/numberUtils.test.ts
 ✓ src/utils/numberUtils.test.ts (8 tests) 3ms
 Test Files  1 passed (1)
      Tests  8 passed (8)

npx tsc --noEmit reports no new errors in the touched files. (The repo has pre-existing tsc errors in unrelated test files like returnUrlUtils.test.ts, roles.test.ts, top_key_view.test.tsx, useLogFilterLogic.min.test.tsx — those are out of scope here.)

Out of scope (intentional)

• Backend Pydantic validation of MCPServerCostInfo. Reporter mentions converting the TypedDict to a Pydantic model so the proxy rejects non-numeric writes at the boundary. That's a more complete fix but a separate concern with a larger surface; happy to send a follow-up PR if you'd like.
• antd InputNumber typing in mcp_server_cost_config.tsx. The local handleDefaultCostChange(defaultCost: number | null) signature is too narrow for antd's actual (number | string | null) emission. Tightening that properly means changing the function signatures and ripples through callers — defensive coercion at the render boundary is the smaller, safer fix for the symptom users are seeing today.
• Migration off @tremor/react. CLAUDE.md notes the project is migrating to antd, but these files already use tremor and the bug fix doesn't require touching imports. Out of scope.

PR template checklist

• At least 1 test added (ui/litellm-dashboard/src/utils/numberUtils.test.ts, 8 cases)
• Touched files type-check cleanly with tsc --noEmit
• No raw SQL / no Prisma changes / no schema impact
• No new @tremor/react imports introduced
• Followed CLAUDE.md guidance on shared util placement (src/utils/numberUtils.ts)

Reported and root-caused by @marty-sullivan in #27095.

Changed files

• ui/litellm-dashboard/src/components/mcp_tools/mcp_server_cost_config.tsx (modified, +25/-21)
• ui/litellm-dashboard/src/components/mcp_tools/mcp_server_cost_display.tsx (modified, +28/-34)
• ui/litellm-dashboard/src/utils/numberUtils.test.ts (added, +59/-0)
• ui/litellm-dashboard/src/utils/numberUtils.ts (added, +33/-0)