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[Bug]: Claude version probe drops CLI stderr, so a broken wrapper shows only "installed but failed to run"

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@juliusmarminge is already working on this.

Since Oct 21, 2026.

  • #22878 by @juliusmarminge — open
  • #23717 by @IzonIcy — open

Assessment

Difficulty
2/5
Estimated time
1-3 hours
Newbie friendliness
76/100
Issue type
Bug
Clarity
Clearly specified
Activity status
Active
Tech stack
typescript
Domain
backend

Research direction

Start in apps/server/src/provider/ClaudeProvider.ts around the version probe at lines 562–582. Read how the probe handles nonzero exits and how its warning and user-facing status message are built; the issue provides a failing wrapper command and its stderr as a reproduction. Done when the probe preserves and surfaces a useful error detail while retaining a fallback message, and the related provider checks pass.

Written by the indexing model from the issue text.

Description

Area

apps/server

Steps to reproduce
  1. Install the Claude CLI wrapper so its postinstall never runs, leaving the placeholder stub it ships with:
    npm i -g --ignore-scripts @anthropic-ai/[email protected]
    
  2. Confirm the CLI fails and explains why:
    $ claude --version; echo "exit=$?"
    Error: claude native binary not installed.
    
    Either postinstall did not run (--ignore-scripts, some pnpm configs)
    or the platform-native optional dependency was not downloaded
    (--omit=optional).
    
    Run the postinstall manually (adjust path for local vs global install):
      node node_modules/@anthropic-ai/claude-code/install.cjs
    
    Or reinstall without --ignore-scripts / --omit=optional.
    exit=1
    
  3. In T3 Code go to Settings → Providers and refresh the probe (the control next to "Checked just now", i.e. server.refreshProviders).
Expected behavior

The provider card and/or the server log carry the CLI's own explanation, at least the first stderr line. The failing CLI already prints the exact fix command, and T3 has that text in hand.

Actual behavior

The card shows only:

Unavailable · Claude Agent CLI is installed but failed to run.

The only record is this warning, which keeps lengths and throws the text away (apps/server/src/provider/ClaudeProvider.ts:565-569):

{
  "name": "checkClaudeProviderStatus",
  "events": [
    {
      "name": "[\n  \"Claude Agent CLI version probe exited with a non-zero status.\",\n  {\n    \"exitCode\": 1,\n    \"stdoutLength\": 0,\n    \"stderrLength\": 383\n  }\n]",
      "attributes": { "effect.logLevel": "WARN" }
    }
  ]
}

Those 383 bytes of stderr were the message quoted in step 2. Since only the length is persisted, no UI surface can recover the cause afterwards. The user-facing message is hardcoded at :580.

Impact

Minor bug or occasional failure

Justification: once a wrapper install is broken, the provider is unusable and the report offers no path to recovery. Every wrapper breakage lands here identically — pnpm installs, --omit=optional, and Chocolatey-style installs as in #22810.

Version or commit

0.1.2-nightly.20261021.3473. Still present on main: apps/server/src/provider/ClaudeProvider.ts:562-582.

Environment

WSL2, Ubuntu 24.04.5 LTS (kernel 6.18.33.2-microsoft-standard-WSL2), Node v24.21.0 via fnm, @anthropic-ai/claude-code 2.1.306 (npm global). T3 host is the WSL distro (Settings header renders "on wsl"). Provider: Claude (claudeAgent); Codex and OpenCode were unaffected on the same host.

Logs or stack traces
$ grep -h "version probe exited" ~/.t3/userdata/logs/server.trace.ndjson | tail -1
{"type":"effect-span","name":"checkClaudeProviderStatus","durationMs":14.466428,"events":[{"name":"[\n  \"Claude Agent CLI version probe exited with a non-zero status.\",\n  {\n    \"exitCode\": 1,\n    \"stdoutLength\": 0,\n    \"stderrLength\": 383\n  }\n]","attributes":{"effect.logLevel":"WARN"}}]}
Workaround

Run the wrapper's postinstall by hand, then refresh the provider probe:

node "$(npm root -g)/@anthropic-ai/claude-code/install.cjs"

The provider flips to Available once claude --version exits 0. This is restating step 2's own advice, which T3 discarded.

Suggested fix
if (version.code !== 0) {
  const detail = firstNonEmptyLine(version.stderr) || firstNonEmptyLine(version.stdout);
  yield* Effect.logWarning("Claude Agent CLI version probe exited with a non-zero status.", {
    exitCode: version.code,
    stderr: truncate(version.stderr, 2000), // keep the text, not just its length
  });
  // message: detail
  //   ? `Claude Agent CLI is installed but failed to run: ${detail}`
  //   : "Claude Agent CLI is installed but failed to run.",
}

Same class of problem as #19571 (closed), which fixed stderr being dropped for turns. The availability probe was not covered by that fix.

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Merged PRs (30d)
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