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fix(a2a): unambiguous session scopes and validated context ids

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This commit is contained in:
EugeneTes
2026-10-07 14:29:50 +00:00
parent d542fcfe42
commit 0d1ddcc4df
6 changed files with 52 additions and 6 deletions
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6
docs/a2a.md
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@@ -78,8 +78,10 @@ restart to reach that one endpoint (`/.well-known/agent-card.json` and the exten
## Sessions
One `AgentSession` per `(caller, contextId)`, opened or resumed the first time a message names that `contextId`
(a missing one gets a fresh UUID). Scope: `<ScopePrefix>-a2a-<caller>-<contextId>` (the Telegram host's
`ScopePrefix` is `telegram-<chatId>`). The session runs in the caller's workspace, so it loads that workspace's
(a missing one gets a fresh UUID). A client-chosen `contextId` must match `[A-Za-z0-9_-]{1,100}`, otherwise the
message is refused with `InvalidParams`. Scope: `<ScopePrefix>-a2a-<caller>_<contextId>` (the Telegram host's
`ScopePrefix` is `telegram-<chatId>`); caller names never contain `_`, so two different callers or contexts can't
share a session. The session runs in the caller's workspace, so it loads that workspace's
`AGENTS.md` (or `CLAUDE.md`), `PERSONA.md` and `MEMORY.md` exactly like any other session there — same persona,
same memory, separate conversation. It does **not** get a calendar (Google Calendar connections are keyed by
session scope, and an A2A scope never connects one).

4
docs/superpowers/specs/2026-10-07-a2a-server-design.md
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@@ -123,7 +123,9 @@ reads only `<caller workspace>/.volcanic/a2a/tasks/` and also requires `task.cal
1. **Hops**: read `metadata["volcanic.hops"]` (missing = 0). Above `MaxHops` → the task is created and immediately
`failed` with "hop limit reached".
2. **Context**: missing `contextId` → new UUID. Session scope `<ScopePrefix>-a2a-<caller>-<contextId>`, cwd = caller
2. **Context**: missing `contextId` → new UUID; a given one not matching `[A-Za-z0-9_-]{1,100}` → `InvalidParams`
(checked before anything is created). Session scope `<ScopePrefix>-a2a-<caller>_<contextId>` (caller names are
`[a-z0-9-]`, so the first `_` separates name and context: no two pairs share a scope), cwd = caller
workspace, `Channel` = a fresh `A2AChatChannel`, `ExtraExtensions` = `A2ASessionExtension`. `A2ASessionPool` opens
or resumes it.
3. **Task**:

10
src/Volcanic.AgenticCore.A2A.Server/Agent/A2ASessionPool.cs
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@@ -11,7 +11,8 @@ using Volcanic.AgenticCore.Hosting;
namespace Volcanic.AgenticCore.A2A.Server.Agent;
/// <summary>
/// One <see cref="AgentSession"/> per caller context (scope <c>&lt;prefix&gt;-a2a-&lt;caller&gt;-&lt;contextId&gt;</c>) in the
/// One <see cref="AgentSession"/> per caller context (scope <c>&lt;prefix&gt;-a2a-&lt;caller&gt;_&lt;contextId&gt;</c>, see
/// <see cref="ScopeFor"/>) in the
/// caller's workspace, so it loads that workspace's AGENTS.md/CLAUDE.md, PERSONA.md and MEMORY.md. One run at a time per
/// context. Idle sessions are disposed after <see cref="A2AHostOptions.SessionIdleTimeout"/> and resumed from JSONL later.
/// </summary>
@@ -68,7 +69,12 @@ internal sealed class A2ASessionPool : IA2ALiveRuns, IAsyncDisposable
_evictTimer = time.CreateTimer(_ => _ = EvictIdleAsync(), null, TimeSpan.FromMinutes(1), TimeSpan.FromMinutes(1));
}
public static string ScopeFor(A2ACaller caller, string contextId) => $"{caller.ScopePrefix}-a2a-{caller.Name}-{contextId}";
/// <summary>
/// <c>&lt;prefix&gt;-a2a-&lt;caller&gt;_&lt;contextId&gt;</c>. Caller names are <c>[a-z0-9-]</c> (no <c>_</c>), so the first
/// <c>_</c> after the prefix separates the name from the client-chosen context id (<c>[A-Za-z0-9_-]{1,100}</c>, checked
/// by the server): two different (caller, context) pairs never share a scope.
/// </summary>
public static string ScopeFor(A2ACaller caller, string contextId) => $"{caller.ScopePrefix}-a2a-{caller.Name}_{contextId}";
public bool IsLive(string taskId)
{

5
src/Volcanic.AgenticCore.A2A.Server/Hosting/VolcanicA2AServer.cs
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@@ -9,7 +9,7 @@ using Volcanic.AgenticCore.A2A.Server.Tasks;
namespace Volcanic.AgenticCore.A2A.Server.Hosting;
/// <summary>
/// The SDK server for one caller. Adds the pre-checks (busy context, file parts, continuation of a task that isn't
/// The SDK server for one caller. Adds the pre-checks (context id format, busy context, file parts, continuation of a task that isn't
/// waiting), push-config storage in the task file and the per-workspace extended card.
/// </summary>
internal sealed class VolcanicA2AServer(
@@ -32,6 +32,9 @@ internal sealed class VolcanicA2AServer(
private void PreCheck(SendMessageRequest request)
{
var message = request.Message ?? throw new A2AException("A message is required.", A2AErrorCode.InvalidParams);
// Context ids name the session scope (and its directory): only [A-Za-z0-9_-]{1,100}.
if (message.ContextId is { Length: > 0 } requested && !A2ATaskFiles.IsValidId(requested))
throw new A2AException("contextId must match [A-Za-z0-9_-]{1,100}.", A2AErrorCode.InvalidParams);
foreach (var part in message.Parts ?? [])
{
if (part.Raw is { } raw && raw.Length > options.Value.MaxFileBytes)

23
tests/Volcanic.AgenticCore.A2A.Server.Tests/ServerEndToEndTests.cs
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@@ -70,6 +70,29 @@ public class ServerEndToEndTests
Assert.Contains("first", transcript);
}
[Theory]
[InlineData("../x")]
[InlineData("a b")]
[InlineData("ctx.1")]
public async Task Send_BadContextId_InvalidParams(string contextId)
{
await using var host = await A2ATestServer.StartAsync();
var ex = await Assert.ThrowsAsync<A2AException>(() =>
host.Client().SendMessageAsync(Requests.Text("hi", contextId: contextId), CancellationToken.None));
Assert.Equal(A2AErrorCode.InvalidParams, ex.ErrorCode);
Assert.Empty(host.Faux.Requests);
}
[Fact]
public async Task Send_TooLongContextId_InvalidParams()
{
await using var host = await A2ATestServer.StartAsync();
var ex = await Assert.ThrowsAsync<A2AException>(() =>
host.Client().SendMessageAsync(Requests.Text("hi", contextId: new string('a', 200)), CancellationToken.None));
Assert.Equal(A2AErrorCode.InvalidParams, ex.ErrorCode);
Assert.Empty(host.Faux.Requests);
}
[Fact]
public async Task Send_ProviderError_TaskFailed()
{

10
tests/Volcanic.AgenticCore.A2A.Server.Tests/SessionPoolTests.cs
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@@ -102,6 +102,16 @@ public sealed class SessionPoolTests : IAsyncDisposable
Assert.NotNull(run.FinishedAt);
}
[Fact]
public void Scope_DashInCallerOrContext_NeverCollides()
{
var tester = _caller with { Name = "tester" };
var testerX = _caller with { Name = "tester-x" };
Assert.Equal("p-a2a-tester_x-ctx", A2ASessionPool.ScopeFor(tester, "x-ctx"));
Assert.NotEqual(A2ASessionPool.ScopeFor(tester, "x-ctx"), A2ASessionPool.ScopeFor(testerX, "ctx"));
Assert.NotEqual(A2ASessionPool.ScopeFor(tester, "x_ctx"), A2ASessionPool.ScopeFor(testerX, "ctx"));
}
[Fact]
public async Task Pool_Acquire_SetsTrackedEntry()
{