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Add typed state support to McpServer #145

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Add typed state support to McpServer #145

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e0dc1b6
Add typed state support to McpServer
laulauland Oct 23, 2025
0f45ef7
Add changeset for typed state support
laulauland Oct 23, 2025
b088c66
Update changeset to document breaking change
laulauland Oct 23, 2025
6e2ad10
Remove confusing typed-state example
laulauland Oct 23, 2025
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7 changes: 7 additions & 0 deletions .changeset/typed-state-support.md
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Original file line number Diff line number Diff line change
@@ -0,0 +1,7 @@
---
"mcp-lite": major
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@brettimus brettimus Oct 23, 2025

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minor? not sure if we wanna bump to v1

Suggested change
"mcp-lite": major
"mcp-lite": minor

---

Add typed state support to McpServer via generic TConfig parameter, enabling type-safe state access in middleware and handlers.

**Breaking change:** The `ctx.env` property has been removed and replaced with `ctx.state`. Migrate by renaming all `ctx.env` references to `ctx.state`.
11 changes: 6 additions & 5 deletions packages/core/src/context.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -62,24 +62,25 @@ export function getProgressToken(
return undefined;
}

export function createContext(
export function createContext<
TConfig extends { State: unknown } = { State: Record<string, unknown> },
>(
message: JsonRpcMessage,
requestId: JsonRpcId | undefined,
options: CreateContextOptions = {},
): MCPServerContext {
): MCPServerContext<TConfig> {
// Prefer explicit option, otherwise derive from the request message
const progressToken =
options.progressToken !== undefined
? options.progressToken
: getProgressToken(message);

const context: MCPServerContext = {
const context: MCPServerContext<TConfig> = {
request: message,
authInfo: options.authInfo,
requestId,
response: null,
env: {},
state: {},
state: {} as TConfig["State"],
progressToken,
validate: <T>(validator: unknown, input: unknown): T =>
createValidationFunction<T>(validator, input),
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