GITHUB_STEP_SUMMARY exceeds 1024k limit on long sessions

[simonszalai]

Bug Description

When Claude runs a long session (1h+ with many tool calls), the step summary output exceeds GitHub's 1024k hard limit, causing the error:

$GITHUB_STEP_SUMMARY upload aborted, supports content up to a size of 1024k, got 1026k.

Root Cause

In src/entrypoints/run.ts, writeStepSummary() formats the entire execution output into markdown via formatTurnsFromData() and appends it to $GITHUB_STEP_SUMMARY with no total size check.

While formatResultContent() in format-turns.ts truncates individual tool results to 3000 chars, the total accumulated markdown from many turns can easily exceed 1MB.

Steps to Reproduce

1. Tag @claude on a complex issue that requires many tool calls (planning a multi-step feature, etc.)
2. Let the session run for 30+ minutes
3. The step summary upload fails with the 1024k error

Expected Behavior

The step summary should be truncated to stay under GitHub's 1024k limit. Possible approaches:

• Truncate the formatted markdown to ~900k with a "... truncated ..." message
• Collapse older turns and only show recent activity in detail
• Add an input option to control max summary size (related: Feature Request: Add option to disable Claude Code Report in GitHub Step Summary #206)

Actual Behavior

The action errors with the $GITHUB_STEP_SUMMARY upload aborted message. The error is non-fatal (the Claude work itself still succeeds), but it's noisy and prevents viewing the execution summary.

Environment

• anthropics/claude-code-action@v1
• Session duration: ~1h with many tool calls
• Generated summary size: 1026k (just over the 1024k limit)

[dsarno]

Agree and that's why there should be a parameter to turn off the report. On @beta version there was no default report.