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Fixing "Request Aborted" & 525 Errors in Multi-Instance Claude Code Sessions

 The claude CLI tool has rapidly become essential for power users integrating LLM workflows directly into the terminal. However, developers attempting to optimize their throughput by running parallel sessions—one for a backend migration, another for writing unit tests—often hit a hard wall.

You open a new tab, run claude, and suddenly your active sessions terminate. The console spits out Request aborted or, more cryptically, a Cloudflare Error 525: SSL Handshake Failed.

This isn't a network outage. It is a state management conflict inherent to how modern CLI tools handle authentication persistence. This guide details the root cause of these crashes and provides a robust shell-level implementation to isolate your sessions.

The Root Cause: Race Conditions in State Files

To fix the crash, we must understand the architecture of the claude CLI authentication flow.

When you authenticate via claude login, the tool writes an OIDC (OpenID Connect) token and session metadata to a global configuration directory—typically ~/.config/claude or ~/Library/Application Support/claude depending on your OS.

The Concurrency Conflict

The CLI is designed as a "single-player" experience. It assumes one active read/write lock on the configuration file. When you launch two instances:

  1. Instance A reads the token and begins a session.
  2. Instance B starts, reads the same token, and potentially initiates a refresh cycle if the token is near expiry.
  3. Instance B writes the new token to the disk.
  4. Instance A attempts to make a request using the old token (now invalidated by the provider) or attempts to write to the config file while Instance B has a lock.

Why Error 525?

The 525 (SSL Handshake Failed) error is often a side effect of the authentication middleware panicking. When the CLI sends a request with a token that was invalidated milliseconds ago by a parallel process, the upstream edge protection (often Cloudflare) may terminate the connection aggressively during the mTLS (mutual TLS) handshake or header verification phase, resulting in a 525 rather than a standard 401.

The Solution: Ephemeral Session Isolation

We cannot easily patch the binary to handle file locking differently. Instead, we must trick the CLI into believing every terminal tab is a completely separate machine.

We achieve this by manipulating the XDG_CONFIG_HOME environment variable. By pointing each shell session to a unique, temporary directory, we isolate the state files.

Step 1: The claude-iso Wrapper

Add the following function to your shell configuration file (~/.zshrc, ~/.bashrc, or ~/.config/fish/config.fish).

This script does three things:

  1. Creates a temporary directory specific to the current shell's Process ID (PID).
  2. Optionally copies your "main" authentication so you don't have to log in every time.
  3. Launches claude within that isolated context.
  4. Cleans up the garbage files when the session ends.
# Add to ~/.zshrc or ~/.bashrc

function claude-iso() {
  # 1. Define the base config path (adjust based on your OS)
  # Linux: ~/.config/claude
  # macOS: ~/Library/Application\ Support/claude (Usually maps here for Node tools)
  # But standard XDG usually defaults to ~/.config if not set.
  local REAL_CONFIG_DIR="$HOME/.config/claude"
  
  # 2. Create a unique ephemeral directory for this shell session
  # We use $$ (current PID) to ensure uniqueness per tab
  local SESSION_ID="claude-session-$$"
  local TEMP_CONFIG_DIR="/tmp/$SESSION_ID"
  
  echo "🚀 Initializing isolated Claude environment: $SESSION_ID"

  # 3. Create the directory structure
  mkdir -p "$TEMP_CONFIG_DIR/claude"

  # 4. (Optional) Copy existing auth to avoid re-login
  # We look for config.json or session.json. 
  # If you prefer a clean slate every time, comment this block out.
  if [ -d "$REAL_CONFIG_DIR" ]; then
    cp -r "$REAL_CONFIG_DIR/"* "$TEMP_CONFIG_DIR/claude/" 2>/dev/null
    # Remove lock files if copied accidentally
    rm -f "$TEMP_CONFIG_DIR/claude/*.lock"
  fi

  # 5. Run Claude with overridden config path
  # XDG_CONFIG_HOME forces the CLI to look in our temp dir
  env XDG_CONFIG_HOME="$TEMP_CONFIG_DIR" claude "$@"

  # 6. Cleanup (Optional - remove if you want to inspect logs later)
  echo "🧹 Cleaning up session artifacts..."
  rm -rf "$TEMP_CONFIG_DIR"
}

Step 2: Apply Changes

Source your configuration file to load the function immediately:

source ~/.zshrc

Step 3: Usage

Instead of running claude, you now run:

claude-iso

You can now open ten different terminal tabs, run claude-iso in all of them, and they will operate completely independently. Instance A can refresh its token without corrupting the file that Instance B is reading.

Deep Dive: Why XDG_CONFIG_HOME Works here

Most modern CLI tools, particularly those built with Node.js, Rust, or Go, adhere to the XDG Base Directory Specification. This spec creates a standard environment variable (XDG_CONFIG_HOME) to define where user-specific configuration files should be stored.

By default, if this variable is unset, tools default to $HOME/.config.

When we inject env XDG_CONFIG_HOME="$TEMP_CONFIG_DIR", the claude process spawns looking for its config.json in /tmp/claude-session-12345/claude. Since /tmp is RAM-backed on many modern systems (tmpfs), this also has the added benefit of slightly faster I/O operations for the SQLite history files often used by these tools.

Handling Edge Cases and Pitfalls

While isolation solves the crashing, it introduces a new data persistence behavior you must be aware of.

1. Loss of Conversation History

Because we are destroying the $TEMP_CONFIG_DIR after the session closes (step 6 in the script), your conversation history for that specific session is lost when you exit the CLI.

The Fix: If you need persistent history but isolated execution, change the TEMP_CONFIG_DIR definition to use a project-specific hash rather than a process ID.

# Generate a hash based on the current directory path
local PROJECT_HASH=$(pwd | md5sum | awk '{print $1}')
local TEMP_CONFIG_DIR="$HOME/.claude-sessions/$PROJECT_HASH"

This ensures that every time you work on "Project A," you get the history for "Project A," but it won't conflict with "Project B" open in another tab.

2. Rate Limiting

Fixing the concurrency crash allows you to send more requests. Be mindful that while your local machine can now handle parallel requests, the API provider still enforces rate limits on your account. If you run 4 heavy refactor sessions simultaneously, you may hit 429 Too Many Requests errors.

3. Re-Authentication Loops

If the optional copy block in the script fails to copy the correct authentication tokens (due to OS-specific path differences), claude-iso will ask you to log in every time.

To debug this, run:

ls -la ~/.config/claude
# or 
ls -la ~/Library/Application\ Support/claude

Update the REAL_CONFIG_DIR variable in the script to match exactly where your machine stores the master config.json.

Summary

The "Request Aborted" and 525 errors in the Claude CLI are symptoms of local resource contention, not upstream instability. By treating the CLI session as an ephemeral container using XDG_CONFIG_HOME and shell isolation, you eliminate file locking conflicts.

This approach allows you to scale your local development workflows, running context-aware AI sessions across multiple repositories simultaneously without fear of session cross-contamination.

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