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Uploaded files are surfaced as MCP resources so clients that speak resources/* (Claude Desktop, Agents SDK, MCP Inspector) can list and read them without going through bash_tool.

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URI shape

file://uploads/{chat_id}/{url-encoded rel_path}
chat_id is embedded in the URI because Agents SDK and Inspector don’t re-send X-Chat-Id on per-resource calls — URIs must be self-contained. URL-encoding: FastMCP’s ResourceTemplate.matches uses [^/]+ per template param (blocks nested paths). Encoding the path flattens it without forking the SDK.

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resources/list

curl -s -X POST "http://localhost:8081/mcp" \
  -H "Authorization: Bearer $MCP_API_KEY" \
  -H "Content-Type: application/json" \
  -H "Accept: application/json, text/event-stream" \
  -H "Mcp-Session-Id: $SESSION_ID" \
  -H "X-Chat-Id: my-session" \
  -d '{"jsonrpc": "2.0", "id": 7, "method": "resources/list"}'
Response: 
{
  "jsonrpc": "2.0", "id": 7,
  "result": {
    "resources": [
      {
        "uri": "file://uploads/my-session/report.docx",
        "name": "report.docx",
        "mimeType": "application/vnd.openxmlformats-officedocument.wordprocessingml.document"
      }
    ]
  }
}

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resources/read

curl -s -X POST "http://localhost:8081/mcp" \
  -H "Authorization: Bearer $MCP_API_KEY" \
  -H "Content-Type: application/json" \
  -H "Accept: application/json, text/event-stream" \
  -H "Mcp-Session-Id: $SESSION_ID" \
  -H "X-Chat-Id: my-session" \
  -d '{
    "jsonrpc": "2.0", "id": 8, "method": "resources/read",
    "params": {"uri": "file://uploads/my-session/notes.txt"}
  }'
  • Text MIME types (text/* + a short allowlist) → contents[0].text.
  • Everything else → contents[0].blob (base64).

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Dynamic registration

sync_chat_resources(chat_id) clears previously-registered entries for that chat and re-adds from the current filesystem state, under an asyncio.Lock to avoid “dict changed size during iteration” when a concurrent resources/list runs during an upload. Called from:
  • docker_manager._create_container — initial sync when the container spins up.
  • app.py:upload_file — after POST /api/uploads/{chat_id}/{filename} saves a new file.

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Uploads

Upload stays on HTTP — MCP has no upload primitive: 
curl -X POST "http://localhost:8081/api/uploads/my-session/notes.txt" \
  -H "Authorization: Bearer $MCP_API_KEY" \
  --data-binary @notes.txt
After the POST returns, the resource is immediately visible to resources/list.