Fix Claude Code Bash timeouts and truncated output: BASH_DEFAULT_TIMEOUT_MS and bashOutputMaxChars

Ask Claude to run the test suite or a build, and after two minutes it reports a timeout without seeing the result. Or a long log gets cut and Claude misses the one error that mattered. Both come from default limits on the Bash tool.

In short: tune timeouts with BASH_DEFAULT_TIMEOUT_MS and BASH_MAX_TIMEOUT_MS, and the output limit with bashOutputMaxChars (or BASH_MAX_OUTPUT_LENGTH). Put them under env in settings.json so you do not have to set them per launch.

How timeouts work

The Bash tool has a default timeout and a ceiling on what the model may request.

Variable	Default	Meaning
BASH_DEFAULT_TIMEOUT_MS	120000 (2 min)	used when the model does not specify a timeout
BASH_MAX_TIMEOUT_MS	600000 (10 min)	the maximum the model may set

The effective ceiling is the larger of BASH_MAX_TIMEOUT_MS and BASH_DEFAULT_TIMEOUT_MS, so raising the default past 10 minutes raises the ceiling with it.

These numeric variables also accept scientific notation such as 2e3 and digit separators such as 64_000.

The output limit

When a command succeeds, Claude reads back at most a fixed number of characters. Past that, Claude Code saves the output to a file and hands Claude a short preview plus the path. Claude can read the file, but it does not automatically read all of it.

Setting	Default	Notes
bashOutputMaxChars (settings.json)	30,000 chars when unset	clamped to 4000–128000; requires v2.1.261 or later
BASH_MAX_OUTPUT_LENGTH (env var)	30000	maximum 150000; ignored once bashOutputMaxChars is set

Raise bashOutputMaxChars when verbose builds or full test logs routinely overflow and you want Claude to read them inline.

{
  "bashOutputMaxChars": 100000
}

Putting it in settings.json

Environment variables under the env key apply to every session and its subprocesses no matter how claude was launched, and they override a variable of the same name set in your shell.

{
  "env": {
    "BASH_DEFAULT_TIMEOUT_MS": "300000",
    "BASH_MAX_TIMEOUT_MS": "1800000"
  },
  "bashOutputMaxChars": 100000
}

Use .claude/settings.json for team-wide values and ~/.claude/settings.json or .claude/settings.local.json for your own. The settings layers are described in Designing permissions in settings.json.

When the working directory drifts

After a command containing cd, later commands may run in the wrong directory and fail. Set CLAUDE_BASH_MAINTAIN_PROJECT_WORKING_DIR to return to the original working directory after each Bash or PowerShell command in the main session.

{
  "env": {
    "CLAUDE_BASH_MAINTAIN_PROJECT_WORKING_DIR": "1"
  }
}

Longer output also costs context. The higher the limit, the more tokens a single command can consume, so from the perspective of Managing context in Claude Code it is best to raise it only when needed.

Summary

• Default timeout is 2 minutes (BASH_DEFAULT_TIMEOUT_MS); the model may request up to 10 minutes (BASH_MAX_TIMEOUT_MS); the ceiling is the larger of the two
• Output is capped at 30,000 characters by default, with overflow saved to a file. bashOutputMaxChars (4,000–128,000) adjusts it and overrides BASH_MAX_OUTPUT_LENGTH
• Values under env in settings.json beat the shell and apply to every session
• Run never-ending commands in the background instead of extending timeouts
• Use CLAUDE_BASH_MAINTAIN_PROJECT_WORKING_DIR if cd leaves later commands in the wrong directory