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fix(server): Claude MCP timeouts preserve the native session #25660

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Merged
juliusmarminge merged 4 commits into from
Oct 27, 2026
+17 −1
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fix(server): Claude MCP timeouts preserve the native session #25660

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03f9386
test(server): reproduce issue 22198 MCP registration timeout dropping…
juliusmarminge Oct 26, 2026
44a07ec
fix(server): Claude MCP registration timeouts keep the native session
juliusmarminge Oct 26, 2026
8f657bf
Merge main into fix/issue-22198
juliusmarminge Oct 26, 2026
384c16d
Merge remote-tracking branch 'origin/main' into fix/issue-22198
juliusmarminge Oct 26, 2026
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4 changes: 3 additions & 1 deletion apps/server/src/orchestration-v2/ProviderTurnStartService.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -72,12 +72,14 @@ const isProviderTurnStartError = Schema.is(ProviderTurnStartError);

/**
* Claude refuses these before it reads the prompt: replacing a process running background work,
* or launch arguments whose appended system prompt cannot be read.
* launch arguments whose appended system prompt cannot be read, or MCP registration that never
* answers while the query opens.
*/
const PROMPT_REFUSAL_TAGS = [
"ClaudeBackgroundWorkBlocksQueryReplacementError",
"ClaudeAppendSystemPromptFileError",
"ClaudeAppendSystemPromptMissingValueError",
"ClaudeMcpRegistrationTimeoutError",
] as const;

const refusedBeforePrompt = (error: unknown): boolean =>
Expand Down
14 changes: 14 additions & 0 deletions apps/server/src/orchestration-v2/testkit/ProviderSwitch.integration.test.ts
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Expand Up @@ -36,6 +36,7 @@ import * as SqlClient from "effect/sql/SqlClient";
import * as SqlitePersistence from "../../persistence/Sqlite.ts";
import { CommandPolicyCapabilityUnsupportedError } from "../CommandPolicy.ts";
import {
ClaudeAgentSdkQueryRunnerError,
ClaudeAppendSystemPromptFileError,
ClaudeBackgroundWorkBlocksQueryReplacementError,
ClaudeProviderCapabilitiesV2,
Expand Down Expand Up @@ -404,6 +405,12 @@ const waitForIdle = Effect.fn("ProviderSwitchTest.waitForIdle")(function* (
return idle;
});

// Same tag as the adapter's unexported error raised when Claude never answers setMcpServers.
class ClaudeMcpRegistrationTimeoutError extends Schema.TaggedError<ClaudeMcpRegistrationTimeoutError>()(
"ClaudeMcpRegistrationTimeoutError",
{},
) {}

describe("orchestration v2 provider switching", () => {
it.live.each([
"compact-native",
Expand Down Expand Up @@ -1311,6 +1318,13 @@ describe("orchestration v2 provider switching", () => {
it.live.each([
["background work", new ClaudeBackgroundWorkBlocksQueryReplacementError()],
["an unreadable append file", new ClaudeAppendSystemPromptFileError({ path: "missing.md" })],
[
"an MCP registration timeout",
new ClaudeAgentSdkQueryRunnerError({
method: "setMcpServers",
cause: new ClaudeMcpRegistrationTimeoutError(),
}),
],
] as const)("keeps the native session after turns refused for %s", ([, refusalCause]) =>
Effect.scoped(
Effect.gen(function* () {
Expand Down
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