fastmcp/examples/persistent_state/README.md
2026-01-16 14:11:21 -05:00

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# Persistent Session State
This example demonstrates session-scoped state that persists across tool calls within the same MCP session.
## What it shows
- State set in one tool call is readable in subsequent calls
- Different clients have isolated state (same keys, different values)
- Reconnecting creates a new session with fresh state
## Running
**HTTP transport:**
```bash
# Terminal 1: Start the server
uv run python server.py
# Terminal 2: Run the client
uv run python client.py
```
**STDIO transport (in-process):**
```bash
uv run python client_stdio.py
```
## Example output
```text
Each line below is a separate tool call
Alice connects
session a9f6eaa3
set user = Alice
set secret = alice-password
get user → Alice
get secret → alice-password
Bob connects (different session)
session 0c3bffc5
get user → not found
get secret → not found
set user = Bob
get user → Bob
Alice reconnects (new session)
session e39640e3
get user → not found
```