Fix session-start hook execution in plugin context

[ryancnelson]

Problem

The session-start.sh hook fails silently when executed by Claude Code with error "⏺ Plugin hook error:" preventing skills context from loading.

Root Cause

1. BASH_SOURCE[0] is unbound in Claude Code's execution context (fails with set -u)
2. Empty grep results return exit code 1 (fails with set -e)

Solution

1. Use ${BASH_SOURCE[0]:-$0} to fallback to $0 when BASH_SOURCE unavailable
2. Add || true to handle empty grep results gracefully

Testing

✅ Direct execution produces valid JSON
✅ Claude Code plugin execution now works
✅ No breaking changes to existing functionality

Changes

• hooks/session-start.sh: 2 lines changed
  • Line 10: Add ${BASH_SOURCE[0]:-$0} fallback
  • Line 18: Add || true for empty grep results

Summary by CodeRabbit

• Bug Fixes

  • Ensured reliable startup by correctly resolving the script location across environments, even when path variables are unset.
  • Prevented errors during initialization when clearing update/status flags that may not exist, allowing sessions to proceed smoothly.

• Chores

  • Hardened session initialization for improved robustness and resilience.

[coderabbitai]

Walkthrough

The session-start hook script updates how it resolves its directory by adding a fallback when BASH_SOURCE[0] is unset and makes the SKILLS_UPDATED/BEHIND flag cleanup tolerant to no-output cases by appending || true.

Changes

Cohort / File(s)	Summary
Session start hook hardening hooks/session-start.sh	- SCRIPT_DIR uses ${BASH_SOURCE[0]:-$0} for fallback when BASH_SOURCE[0] is unset - Flag cleanup (SKILLS_UPDATED/BEHIND) pipeline now appends `

Sequence Diagram(s)

sequenceDiagram
    participant U as Invoker (hook)
    participant S as session-start.sh
    participant FS as Filesystem

    U->>S: Execute hook
    rect rgba(200,230,255,0.3)
      note over S: Resolve script directory
      S->>S: SCRIPT_DIR = dir("${BASH_SOURCE[0]:-$0}")
    end

    rect rgba(220,255,220,0.3)
      note over S,FS: Initialize/clean output flags
      S->>FS: Remove SKILLS_UPDATED/BEHIND markers
      FS-->>S: May return no results
      S->>S: Continue on empty via "|| true"
    end

    S-->>U: Proceed with remaining startup

Loading

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

Poem

I hop to hooks at break of day,
Path found even when shells stray—hurray!
Flags that flicker, now behave,
If none appear, we still stay brave.
With bashy paws, I press on through,
Session starts fresh—carrots anew! 🥕

Pre-merge checks and finishing touches

✅ Passed checks (3 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title Check	✅ Passed	The title clearly and concisely summarizes the primary change of fixing the session-start hook's behavior in a plugin context by highlighting the core issue and solution without extraneous details.
Docstring Coverage	✅ Passed	No functions found in the changes. Docstring coverage check skipped.

✨ Finishing touches

• 📝 Generate docstrings

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment

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[ryancnelson]

this PR is all ai-generated, btw.... i just asked claude/superpowers to help debug the issue.

[coderabbitai]

Actionable comments posted: 0

🧹 Nitpick comments (2)

hooks/session-start.sh (2)

18-18: Simplify flag stripping; avoid masking real errors.

Use a single grep (or sed) to drop both lines without needing || true, reducing processes and keeping failures visible.

Apply one of the following:

-init_output=$(echo "$init_output" | grep -v "SKILLS_UPDATED=true" | grep -v "SKILLS_BEHIND=true" || true)
+init_output=$(echo "$init_output" | grep -Ev 'SKILLS_UPDATED=true|SKILLS_BEHIND=true' || true)

Or with sed (no need for || true):

-init_output=$(echo "$init_output" | grep -v "SKILLS_UPDATED=true" | grep -v "SKILLS_BEHIND=true" || true)
+init_output=$(echo "$init_output" | sed -E '/SKILLS_UPDATED=true|SKILLS_BEHIND=true/d')

---

15-16: skills_updated appears unused (SC2034).

Either use it for messaging or remove to avoid confusion.

Option A — remove it:

-skills_updated=$(echo "$init_output" | grep "SKILLS_UPDATED=true" || echo "")
 skills_behind=$(echo "$init_output" | grep "SKILLS_BEHIND=true" || echo "")

Option B — surface a success message:

 skills_behind=$(echo "$init_output" | grep "SKILLS_BEHIND=true" || echo "")
 # Build status messages that go at the end
 status_message=""
+if [ -n "$skills_updated" ]; then
+    status_message="\n\n✅ Skills updated from upstream."${status_message}
+fi
 if [ -n "$skills_behind" ]; then
     status_message="\n\n⚠️ New skills available from upstream. Ask me to use the pulling-updates-from-skills-repository skill."
 fi

📜 Review details

Configuration used: CodeRabbit UI

Review profile: CHILL

Plan: Pro

📥 Commits

Reviewing files that changed from the base of the PR and between bde691c and b731542.

📒 Files selected for processing (1)

• hooks/session-start.sh (1 hunks)

🧰 Additional context used

🪛 Shellcheck (0.11.0)

hooks/session-start.sh

[warning] 15-15: skills_updated appears unused. Verify use (or export if used externally).

(SC2034)

🔇 Additional comments (1)

hooks/session-start.sh (1)

10-10: Good fix for set -u contexts.

${BASH_SOURCE[0]:-$0} safely handles unbound BASH_SOURCE and keeps path resolution robust when sourced or executed.

[ericphanson]

I'm also hitting the empty grep results issue here when using a fork of the skills directory. As summarized by Claude code:

When a user is working on a fork with local commits ahead of the tracking branch, initialize-skills.sh outputs only
SKILLS_BEHIND=true with no user-facing messages. The session-start hook then filters out status flags with grep -v,
which leaves empty output. Without || echo "", grep exits with code 1 when all lines are filtered out, causing the
script to fail due to set -euo pipefail. This prevents the hook from executing successfully.

(This PR uses || true instead of || echo "")