fix: remove CLAUDECODE env var detection, centralize stripping

[rysweet]

Summary

• Removes all usage of the CLAUDECODE environment variable for adapter selection decisions. The Claude Code binary sets this to block nested sessions, but we always want nested sessions to work.
• Creates a centralized build_child_env() utility in src/amplihack/recipes/adapters/env.py that handles stripping CLAUDECODE from child process environments in one place, replacing scattered implementations across 15 files.
• Removes unset CLAUDECODE from shell scripts (run_recipe_subprocess.sh, orchestrator-generated run.sh) since the Python adapters now handle this centrally.
• Updates get_adapter() to no longer check CLAUDECODE for adapter selection -- it now defaults to Claude SDK if available, then CLI subprocess.
• Updates all tests to verify env stripping behavior without depending on CLAUDECODE detection logic.
• Updates documentation (STREAMING_OUTPUT.md, RECENT_FIXES_MARCH_2026.md, SKILL.md, reference.md) to remove CLAUDECODE as a user-facing concern.

Follow-up to #2845 quality improvements.

Test plan

• pytest tests/unit/recipes/test_cli_subprocess_temp_dir.py -- 8/8 pass
• pytest tests/unit/recipes/test_streaming_adapters.py -- 15/15 pass (2 pre-existing failures excluded)
• pytest tests/recipes/test_recipe_runner_parse_json.py -- 26/26 pass
• Verified all 23 pre-existing test failures in tests/unit/recipes/ are identical to main branch (not introduced by this change)
• CI passes

🤖 Generated with Claude Code

[github-actions]

🤖 Auto-fixed version bump

The version in pyproject.toml has been automatically bumped to the next patch version.

If you need a minor or major version bump instead, please update pyproject.toml manually and push the change.

[github-actions]

Repo Guardian - Action Required

❌ Ephemeral Content Detected

The following file violates the repository's ephemeral content policy:

docs/recipes/RECENT_FIXES_MARCH_2026.md

Why flagged:

• Filename contains a temporal date ("MARCH_2026") indicating point-in-time content
• Content explicitly states "This document tracks recent bug fixes" (emphasis mine)
• Version history section says "All fixes released in amplihack v0.9.0 (March 2026)"
• This is essentially release notes with a date stamp that will become stale

Problematic content:

# Recent Recipe Runner & Skills Fixes - March 2026

This document tracks recent bug fixes and improvements...

## Version History

All fixes released in **amplihack v0.9.0** (March 2026):
```

**Where this content should go instead:**

1. **CHANGELOG.md** - Add a section for v0.9.0 with these fixes
2. **GitHub Release Notes** - Create a release for v0.9.0 with this content
3. **PR descriptions** - The detailed explanations could be in individual PR descriptions
4. **Permanent reference docs** - The technical details (how features work) could be moved to timeless documentation without the "recent" framing

**Why this matters:**

Files with dates in their names and "recent" framing become outdated immediately. In 6 months, "recent fixes from March 2026" is no longer recent. This creates clutter and confusion about what's current.

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[rysweet]

Workflow Retrofit: Outside-in Testing & Review Results

Step 12: Test Suite

• tests/unit/recipes/ — 393 passed, 23 failed (all 23 pre-existing on main, 0 regressions)
• tests/recipes/ — 66 passed, 0 failed
• PR-specific tests (4 test files changed by PR) — 54 passed, 2 failed (both pre-existing on main: test_execute_bash_step_has_timeout)

Verdict: No test regressions introduced by this PR.

Step 17: Code Review

Findings:

1. env.py is clean, minimal, and follows the brick pattern — single responsibility, extensible _STRIPPED_VARS frozenset.
2. Both CLISubprocessAdapter and NestedSessionAdapter properly delegate to build_child_env().
3. get_adapter() correctly removes the CLAUDECODE-based auto-selection of NestedSessionAdapter. SDK adapter is tried first, then CLI fallback. Nested can still be explicitly selected via preference="nested".
4. All shell scripts (scripts/run_recipe_subprocess.sh, orchestrator run.sh generation) no longer contain unset CLAUDECODE.
5. Documentation updated consistently across SKILL.md, reference.md, STREAMING_OUTPUT.md, and RECENT_FIXES_MARCH_2026.md.

Minor note (not blocking): tests/e2e/test_hook_startup_e2e.py:55 still does env.pop("CLAUDECODE", None) manually instead of using build_child_env(). This is arguably outside PR scope since it's an e2e test that spawns claude directly (not via an adapter), but could be cleaned up in a follow-up.

Step 17b: Security Review

• build_child_env() copies ALL env vars except CLAUDECODE — PATH, HOME, USER, LANG, etc. are all preserved.
• Only CLAUDECODE is stripped — no other vars are accidentally removed.
• CLAUDE_PLUGIN_ROOT and CLAUDE_CODE_ENTRYPOINT are preserved (they are NOT blocking vars).
• _STRIPPED_VARS is a frozenset, easily extensible if other vars need stripping in the future.
• No information leakage or security concerns.

Step 13: Outside-in Testing (16/16 PASS)

All tests run with CLAUDECODE=1 set in the parent environment to simulate being inside Claude Code:

#	Test	Result
1	claude -p "What is 2+2?" without CLAUDECODE	PASS
3	get_adapter() returns adapter without CLAUDECODE check	PASS
4	build_child_env() strips CLAUDECODE, preserves PATH/HOME	PASS
5	orchestrator.py no longer contains unset CLAUDECODE	PASS
6	run_recipe_subprocess.sh no longer contains unset CLAUDECODE	PASS
7	Session tree context propagated (depth incremented, tree ID preserved)	PASS
8	Defaults generated when no session tree exists (depth 0->1, 8-char hex ID)	PASS
9	NestedSessionAdapter delegates to build_child_env()	PASS
10	CLISubprocessAdapter delegates to build_child_env()	PASS
11	get_adapter(preference="nested") returns NestedSessionAdapter	PASS
12	get_adapter(preference="cli") returns CLISubprocessAdapter	PASS
13	build_child_env properly exported from adapters package	PASS
14	claude -p runs successfully with build_child_env() cleaned env (CLAUDECODE=1 in parent)	PASS
15	CLISubprocessAdapter.execute_agent_step works with CLAUDECODE=1 set	PASS
16	NestedSessionAdapter.execute_agent_step works with CLAUDECODE=1 set	PASS

Critical tests 14-16 verify the actual fix end-to-end: with CLAUDECODE=1 set in the parent process (simulating running inside Claude Code), both adapters successfully spawn nested claude -p sessions via build_child_env().

Summary

PR is clean. No regressions, no missed CLAUDECODE references in source code, security review passed, and all 16 outside-in tests pass including real nested Claude session execution.

[github-actions]

Triage Report - FAST TRACK CANDIDATE

Risk Level: LOW
Priority: HIGH
Status: Ready for fast-track merge

Analysis

✅ Net reduction: -28 LOC (simplification)
✅ Centralization: Replaces scattered env var checks with single utility
✅ Clean scope: 16 files but focused changes
✅ Fresh: Created 9.5 hours ago

Rationale

This PR removes duplication and centralizes CLAUDECODE environment variable handling. The centralized build_child_env() utility replaces 15 scattered implementations - classic refactoring win.

Next Steps

1. Wait for CI to pass
2. Quick code review of centralized utility
3. Merge if tests green - good candidate for fast-track

Recommendation: FAST_TRACK after CI validation.

AI generated by PR Triage Agent

[github-actions]

🤖 Auto-fixed version bump

The version in pyproject.toml has been automatically bumped to the next patch version.

If you need a minor or major version bump instead, please update pyproject.toml manually and push the change.

[github-actions]

Repo Guardian - Action Required

❌ Ephemeral Content Detected

The following file violates the repository's ephemeral content policy:

docs/recipes/RECENT_FIXES_MARCH_2026.md

Why flagged:

• Filename contains temporal date: "MARCH_2026" indicates point-in-time snapshot content
• Explicitly describes itself as tracking "recent" fixes: Line 3 states "This document tracks recent bug fixes and improvements"
• Version-specific content: States "All fixes released in amplihack v0.9.0 (March 2026)" suggesting this is a moment-in-time snapshot
• Will become stale: As development continues, this document will become outdated historical notes rather than current reference material

Problematic content quotes:

Line 1: "Recent Recipe Runner & Skills Fixes - March 2026"
Line 3: "This document tracks recent bug fixes..."
Line 142: "All fixes released in amplihack v0.9.0 (March 2026)"
```

**Where this content should go instead:**
- **CHANGELOG.md** or **docs/CHANGELOG.md** — This is exactly what changelogs are for (date-stamped release notes)
- **Release notes** — GitHub Releases for v0.9.0
- **PR descriptions** — Individual PR #2813, #2807, #2804, #2811 already document these fixes
- **Permanent reference docs** — If specific fixes need long-term documentation, integrate them into the main docs without date stamps

**Recommendation:**
Move this content to `CHANGELOG.md` under a `## [0.9.0] - 2026-03` section, or integrate specific technical details (like YAML frontmatter requirements) into permanent reference documentation without the date stamp.

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