Improve documentation of HTTP mode and multiple agents in general

Resolves #1118

docs/02-usage/020_running.md

@@ -132,7 +132,7 @@ to use such a launch command.
 (streamable-http)=
 ### Streamable HTTP Mode
 
-When using instead the *Streamable HTTP* mode, you control the server lifecycle yourself,
+When using *Streamable HTTP* mode, you control the server lifecycle yourself,
 i.e. you start the server and provide the client with the URL to connect to it.
 
 Simply provide `start-mcp-server` with the `--transport streamable-http` option and optionally provide the desired port
@@ -147,7 +147,14 @@ you would run
 
 and then configure your client to connect to `http://localhost:9121/mcp`.
 
-Note that while the legacy SSE transport is also supported (via `--transport sse` with corresponding /sse endpoint), its use is discouraged.
+**When to use.** Note that Serena is a stateful MCP server, and only one coding project can be active at a time.
+Therefore, starting a single Serena instance and connecting it to multiple clients is only 
+appropriate if all clients will be working on the same project.  
+If you want several agents to work on different projects, making each client/agent start its own server
+in stdio mode is likely the best option.
+See section [The Project Workflow](040_workflow) for more information on how to manage projects in Serena.
+
+The legacy SSE transport is also supported (via `--transport sse` with corresponding /sse endpoint), its use is discouraged.
 
 (mcp-args)=
 ### MCP Server Command-Line Arguments

docs/02-usage/040_workflow.md

@@ -160,13 +160,13 @@ and that has a good test coverage is much easier to work with for Serena.
 
 We generally recommend to start an editing task from a state where all linting checks and tests pass.
 
-## Working with Multiple Projects Simultaneously
+## Multiple Projects, Multiple Agents
 
 There are several ways in which you might want to work with multiple projects simultaneously.
 
-### Simultaneously Editing in Multiple Projects
+### A Single Agent Editing Multiple Projects Simultaneously
 
-If fulfilling a task requires the agent to edit code in multiple projects, the recommended approach is to create a **monorepo folder**,
+If fulfilling a task requires a single agent to edit code in multiple projects, the recommended approach is to create a **monorepo folder**,
 i.e. a folder that contains all the projects as sub-folders, and open that monorepo folder as a project in Serena.
 You may also use symbolic links to create a monorepo folder if the projects are located in different places on your filesystem.
 
@@ -197,3 +197,16 @@ Depending on the language backend being used, the management of resources for th
   where `<serena>` is your way of running Serena. For example, when using `uvx`, run
 
       uvx --from git+https://github.com/oraios/serena serena start-project-server
+
+### Multiple Agents Accessing a Single Serena Instance
+
+If you want multiple agents to access the same project via a single Serena instance,
+i.e. you do not want several instances of Serena (including its language servers) to be running,
+you can achieve this by [starting the Serena MCP server in HTTP mode](streamable-http)
+and connecting all client agents to the same HTTP endpoint.
+The agents will then share the resources of the single Serena instance.
+
+### Multiple Agents Working on Different Projects
+
+For this use case, simply run a separate instance of Serena for each project, which naturally
+occurs when Serena is started by the MCP client in stdio mode.