fix(vscode-extension): improve startup failure UX and watchdog coverage by dyxushuai · Pull Request #139 · symposium-dev/symposium

dyxushuai · 2026-02-10T15:02:49Z

Why

Startup failures in the VS Code chat showed noisy diagnostics and unclear recovery paths.
Startup edge cases (slow startup, timeout, process exit, ACP initialize rejection) needed deterministic end-to-end coverage.

How

Added startup watchdog diagnostics and routed startup failures through compact chat-facing error payloads while keeping full diagnostics in logs.
Unified startup status into a single warning card lifecycle (slow -> fail updates the same card), added More details to Output, and added Symposium: Show Output command.
Disabled prompt input while startup is pending or failed, and re-enabled it when startup/session context becomes available.
Added fake startup agent fixture and startup-focused tests (watchdog unit + failure matrix integration + routing checks).
Updated design/testing docs for message protocol and startup behavior.

Tests

cd vscode-extension && npm run compile ✅
cd vscode-extension && npm test ✅ (23 passing, 1 pending)
cd vscode-extension && npm run lint ✅ (warnings only, no errors)
cargo check --workspace ✅

Closes #124

dyxushuai · 2026-02-10T15:05:14Z

@nikomatsakis +r

dyxushuai · 2026-02-10T15:09:38Z

More UI improvements are WIP.

Copilot

Pull request overview

Improves the VS Code extension’s startup failure UX by adding a startup watchdog, routing startup failures into compact chat-visible error payloads (with full diagnostics kept in Output/logs), and adding deterministic test coverage for startup edge cases.

Changes:

Added a startup watchdog around ACP initialize (slow-threshold feedback + hard-timeout failure) and surfaced slow/fail states to the webview via indexed messages.
Updated webview UI to use a single “startup status” warning card lifecycle, added “More details” (Output) affordance, and disabled prompt input until startup/session context is available.
Added fake startup agent fixture plus new unit/integration tests for startup watchdog and failure-mode matrix.

Reviewed changes

Copilot reviewed 16 out of 17 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
`vscode-extension/src/acpAgentActor.ts`	Adds startup watchdog types/logic and wraps ACP initialize with timeouts and diagnostics.
`vscode-extension/src/chatViewProvider.ts`	Routes startup errors through `agent-error`, publishes `agent-startup-slow`, adds test queue inspection helpers.
`vscode-extension/src/symposium-webview.ts`	Renders unified startup status card, adds “show output” action, freezes/unfreezes input based on startup/session state.
`vscode-extension/src/extension.ts`	Registers `symposium.showOutput` and new `symposium.test.*` harness commands.
`vscode-extension/src/mynah-ui.d.ts`	Introduces local typings for `@aws/mynah-ui`.
`vscode-extension/test-fixtures/fake-startup-agent.cjs`	Deterministic fake agent for startup scenarios (exit/hang/close/acp-error).
`vscode-extension/src/test/*.test.ts`	Adds watchdog unit tests + startup failure matrix integration + routing checks.
`vscode-extension/package.json`	Adds watchdog configuration settings + contributes `Symposium: Show Output` command.
`vscode-extension/.vscode-test.mjs`	Pins test user/extension dirs for repeatable VS Code test runs.
`vscode-extension/.gitignore`	Ignores test workspace config output.
`md/design/vscode-extension/*.md`	Documents protocol/testing behavior for startup watchdog and matrix coverage.

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Copilot · 2026-02-10T15:13:05Z

vscode-extension/src/acpAgentActor.ts

+  const reasonMap: Record<StartupFailureReason, StartupWatchdogDiagnosticReason> = {
+    "initialize-rejected": "initialize_error",
+    "hard-timeout": "hard_timeout",
+    "process-exit": "process_exit",
+    "stdout-close": "stdout_close",
+    "process-error": "process_error",
+  };
+
+  return {
+    reason: reasonMap[details.reason],


The reasonMap object literal introduces new eslint @typescript-eslint/naming-convention warnings because the keys are kebab-case string literals. Consider using a Map, an array of tuples, or a scoped eslint disable comment for this mapping so the repo lint output stays clean.

Suggested change

const reasonMap: Record<StartupFailureReason, StartupWatchdogDiagnosticReason> = {

"initialize-rejected": "initialize_error",

"hard-timeout": "hard_timeout",

"process-exit": "process_exit",

"stdout-close": "stdout_close",

"process-error": "process_error",

};

return {

reason: reasonMap[details.reason],

const reasonMap = new Map<StartupFailureReason, StartupWatchdogDiagnosticReason>([

["initialize-rejected", "initialize_error"],

["hard-timeout", "hard_timeout"],

["process-exit", "process_exit"],

["stdout-close", "stdout_close"],

["process-error", "process_error"],

]);

return {

reason: reasonMap.get(details.reason)!,

Copilot · 2026-02-10T15:13:06Z

vscode-extension/src/acpAgentActor.ts

+    slowThresholdMs: details.slowThresholdMs,
+    hardTimeoutMs: details.hardTimeoutMs,
+    command: details.command,
+    args: details.args,


toStartupWatchdogDiagnostics reuses the same details.args array reference for diagnostics.args. Because the logger prints objects via console.log, repeated references can show up as [Circular] and make diagnostics harder to read. Clone arrays/objects when building StartupWatchdogDiagnostics (e.g., copy args) to avoid this.

Suggested change

args: details.args,

args: details.args.slice(),

Copilot · 2026-02-10T15:13:06Z

vscode-extension/src/symposium-webview.ts

+function parseStartupKeyValuePairs(message: string): Record<string, string> {
+  const pairs: Record<string, string> = {};
+  const matches = message.matchAll(/([A-Za-z][A-Za-z0-9]*)=([^\s]+)/g);
+  for (const match of matches) {
+    const key = match[1];
+    const value = match[2];
+    if (key && value) {
+      pairs[key] = value;
+    }
+  }
+  return pairs;
+}
+
+function formatStartupFailureBody(error: unknown): string {
+  let startupMessage = "Operation failed";
+
+  if (error && typeof error === "object") {
+    const structured = error as Record<string, unknown>;
+    if (typeof structured.message === "string" && structured.message.trim()) {
+      startupMessage = structured.message.trim();
+    } else {
+      startupMessage = formatAgentErrorBody(error);
+    }
+  } else if (typeof error === "string" && error.trim()) {
+    startupMessage = error.trim();
+  } else {
+    startupMessage = formatAgentErrorBody(error);
+  }
+
+  const diagnostics = parseStartupKeyValuePairs(startupMessage);
+  const reason = diagnostics.reason ?? "unknown";
+  const phase = diagnostics.phase;
+  const elapsedMs = diagnostics.elapsedMs;
+  const slowThresholdMs = diagnostics.slowThresholdMs;
+  const hardTimeoutMs = diagnostics.hardTimeoutMs;
+


parseStartupKeyValuePairs only captures values up to the next whitespace. For startup failures like initializeError=simulated acp initialize error, this will truncate the value (and the UI currently doesn’t surface it elsewhere). Consider either extracting initializeError with a dedicated regex that captures the full remainder of the line, or sending structured startup diagnostics separately so the webview can render the initialize error message accurately.

Copilot · 2026-02-10T15:13:06Z

vscode-extension/src/symposium-webview.ts

+}
+
+function formatStartupFailureBody(error: unknown): string {
+  let startupMessage = "Operation failed";


The initial value of startupMessage is unused, since it is always overwritten.

Suggested change

let startupMessage = "Operation failed";

let startupMessage: string;

fix(vscode-extension): refine startup failure UX and test coverage

61aaeaa

Copilot AI review requested due to automatic review settings February 10, 2026 15:02

Copilot started reviewing on behalf of dyxushuai February 10, 2026 15:03 View session

Merge branch 'main' into fix/vscode-startup-watchdog-ux

608cdd0

dyxushuai marked this pull request as draft February 10, 2026 15:09

Copilot AI reviewed Feb 10, 2026

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fix(vscode-extension): improve startup failure UX and watchdog coverage#139

fix(vscode-extension): improve startup failure UX and watchdog coverage#139
dyxushuai wants to merge 2 commits intosymposium-dev:mainfrom
dyxushuai:fix/vscode-startup-watchdog-ux

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	let startupMessage = "Operation failed";
	let startupMessage: string;

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dyxushuai commented Feb 10, 2026 •

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