Claude Code Session Fixer

Small Crystal CLI tool to repair broken Claude Code session files by removing thinking and redacted_thinking blocks from assistant messages in .jsonl sessions.

What It Does

• Scans Claude sessions under ~/.claude/projects/*/*.jsonl.
• Finds assistant messages that contain thinking / redacted_thinking blocks.
• Removes only those blocks from message.content.
• Drops a line if, after removal, content becomes empty.
• Creates a backup before writing changes.

Why

Some Claude session files can become hard to resume when internal thinking blocks are present or malformed for downstream tooling. This utility performs a targeted cleanup without changing unrelated JSON fields.

Requirements

• Crystal >= 1.10.0

Build

crystal build src/session_fixer.cr -o session_fixer

Usage

# Show help
./session_fixer --help

# List sessions that contain thinking blocks
./session_fixer --list

# Fix by full or partial session ID
./session_fixer <session-id>

# Fix by direct file path
./session_fixer /absolute/path/to/session.jsonl

# Preview changes only (no write)
./session_fixer <session-id-or-path> --dry-run

You can also run without building:

crystal run src/session_fixer.cr -- --list
crystal run src/session_fixer.cr -- <session-id> --dry-run

Session Selection Rules

When you pass an ID (not a file path), matching is:

1. Exact UUID match first.
2. Partial UUID match second.
3. If multiple matches are found, the tool stops with an ambiguity error and asks for a longer ID or full path.

Safety and Backups

• Normal mode writes to a temporary file, then replaces the original.
• A backup is created first:
  • preferred: <session>.bak.jsonl
  • if that already exists: <session>.bak.<timestamp>.jsonl
• --dry-run never modifies the source file.

Output Stats

After processing, the tool reports:

• total lines
• modified lines
• removed lines (where content became empty)
• number of thinking blocks removed
• parse errors skipped (if any malformed JSON lines were encountered)

Limitations

• Only assistant messages are modified.
• Non-JSON lines are skipped (counted as parse errors).
• The tool assumes standard Claude session layout under ~/.claude/projects/.