> ## Documentation Index
> Fetch the complete documentation index at: https://docs.trytrellis.app/llms.txt
> Use this file to discover all available pages before exploring further.

# v0.5.2

> 2026-05-06

Fix `SessionStart` hook crash on Python ≤3.11 (`SyntaxError: f-string expression part cannot include a backslash`). No new migrations.

## Bug Fixes

### Hook session-start: PEP 498 f-string backslash in Python ≤3.11

The Windows path normalizer added in 0.5.0-rc.6 (#226) used:

```python theme={null}
return f"{drive}:\\{rest.replace('/', '\\')}"
```

PEP 498 forbids backslashes inside f-string expression parts. On Python ≤3.11 the file fails to parse, and the hook exits with code 1 before running:

```
SessionStart hook (failed)
error: hook exited with code 1
```

PEP 701 in Python 3.12 lifted the restriction, so the bug was invisible to 3.12+ users. Codex CLI 0.128 + Trellis 0.5.0 reproduced it in the field.

Fixed by lifting the `.replace(...)` call out of each f-string expression into a local variable. 9 occurrences across:

* `packages/cli/src/templates/codex/hooks/session-start.py`
* `packages/cli/src/templates/copilot/hooks/session-start.py`
* `packages/cli/src/templates/shared-hooks/session-start.py` (Claude Code / Cursor / Gemini CLI / Qoder / CodeBuddy / Factory Droid / Kiro)

Added regression coverage in `packages/cli/test/regression.test.ts`: regex scan asserts no f-string contains a backslash inside `{...}` expressions, plus a best-effort `python3 -c "ast.parse(...)"` pass.

## Upgrade

```bash theme={null}
npm install -g @mindfoldhq/trellis@latest
trellis update
```