"Prompt too long" causes complete hardlock requiring session restart

Description

During long coding sessions, Claude Code hits a "Prompt too long" error and then becomes completely unresponsive — no further input is accepted, requiring a full session restart. This happened 6 times in a single working day.

Environment

• Model: Claude Opus 4.5 (claude-opus-4-5-20251101)
• Platform: Linux (openSUSE, kernel 6.18.7-1-default)
• Claude Code: VSCode extension
• Session type: Long coding sessions with a large Laravel codebase

Reproduction pattern

1. Start a session involving multiple file reads across a large codebase
2. Launch parallel agents (e.g., 5 concurrent security audit agents)
3. Continue working with file edits, searches, and conversation
4. Eventually "Prompt too long" appears
5. After this error, Claude Code is completely hardlocked — no response to any input
6. Only recovery is to restart the session entirely, losing all accumulated context

Impact

• Context loss: Mid-task state (e.g., "halfway through fixing 12 security audit findings") is lost on every restart
• Workflow disruption: Having to re-explain project context, standards, and current task state after each restart
• Frequency: 6 occurrences in one day makes this a blocking issue for sustained development work
• The auto-summarization on session continue helps, but cannot fully capture in-progress task state

Expected behavior

Either:

• Graceful context trimming that keeps the session responsive, or
• A clear recovery path that doesn't require a full restart (e.g., automatic summarization and continuation)

Additional context

The sessions involve heavy tool use: parallel agent launches, many file reads (Blade templates, PHP controllers, models), grep/glob searches, and bash commands. The combination of large file contents + parallel agent outputs seems to accelerate hitting the limit.