# In-flight recon trace (illustrative)

**Illustrative demonstration, not a SWE-bench Pro scored instance.** Produced by GPT-5.4 (codex) following `skills/recon/skill.md` on a real, reproducible bug: `theskumar/python-dotenv` issue #499, an `AssertionError` in `find_dotenv()` introduced in v1.0.1. Every command shown was actually run; the diagnosis took a few minutes.

A committed hypothesis-graph node records only the *terminal* reasoning mode (here `induction, 93%`). This trace shows the mode flip-flopping in-flight before it collapses to that node.

---

**In-Flight Trace**

Target: `theskumar/python-dotenv`, checked out to `v1.0.1` (`d6c0b96`), then compared against `v1.0.0` (`d0684d1`).

1. `H0` | `abduction`
Evidence:
```bash
PYTHONPATH=/tmp/recon-demo/python-dotenv/src python3 - <<'PY'
from dotenv import find_dotenv, load_dotenv
if path := find_dotenv(raise_error_if_not_found=False):
    load_dotenv()
print('done', path)
PY
```
Output:
```text
Traceback (most recent call last):
  File "<stdin>", line 2, in <module>
  File "/tmp/recon-demo/python-dotenv/src/dotenv/main.py", line 305, in find_dotenv
    assert frame.f_back is not None
AssertionError
```
Proposed `H0`: the failure happens because no `.env` file is present.

2. `H0` | `deduction`
Evidence from [main.py](/tmp/recon-demo/python-dotenv/src/dotenv/main.py:310):
```python
for dirname in _walk_to_root(path):
    check_path = os.path.join(dirname, filename)
    if os.path.isfile(check_path):
        return check_path

if raise_error_if_not_found:
    raise IOError('File not found')

return ''
```
And from [main.py](/tmp/recon-demo/python-dotenv/src/dotenv/main.py:302):
```python
while frame.f_code.co_filename == current_file or not os.path.exists(
    frame.f_code.co_filename
):
    assert frame.f_back is not None
```
Kill `H0`: a missing `.env` should return `''` or raise `IOError` later; this crash happens earlier, during frame walking.

3. `H1` | `abduction`
Re-proposal from the failure site: `find_dotenv()` is misclassifying some execution context and then exhausting the frame chain.

4. `H1` | `deduction`
Evidence from [main.py](/tmp/recon-demo/python-dotenv/src/dotenv/main.py:286):
```python
def _is_interactive():
    try:
        main = __import__('__main__', None, None, fromlist=['__file__'])
    except ModuleNotFoundError:
        return False
    return not hasattr(main, '__file__')
```
And [main.py](/tmp/recon-demo/python-dotenv/src/dotenv/main.py:294):
```python
if usecwd or _is_interactive() or getattr(sys, 'frozen', False):
    path = os.getcwd()
else:
    frame = sys._getframe()
```
Working theory: stdin execution may have `__main__.__file__`, so `_is_interactive()` returns `False`, pushing control into the frame-walk branch.

5. `H1` | `induction`
Evidence:
```bash
python3 - <<'PY'
import __main__
print('stdin', hasattr(__main__, '__file__'), getattr(__main__, '__file__', None))
PY
```
Output:
```text
stdin True <stdin>
```
And:
```bash
python3 - <<'PY'
import os
print(os.path.exists('<stdin>'))
PY
```
Output:
```text
False
```
This supports the theory: stdin is treated as non-interactive, but its filename is synthetic and nonexistent.

6. `H1` | `induction`
Cheap perturbations:
```bash
PYTHONPATH=/tmp/recon-demo/python-dotenv/src python3 -c 'from dotenv import find_dotenv; print(repr(find_dotenv(raise_error_if_not_found=False)))'
```
Output:
```text
''
```
```bash
PYTHONPATH=/tmp/recon-demo/python-dotenv/src python3 - <<'PY'
from dotenv import find_dotenv
print(find_dotenv(usecwd=True, raise_error_if_not_found=False))
PY
```
Output: empty line (`''`).
Interpretation: “no `.env`” is fine in other contexts; the crash is specific to the stdin path through frame walking.

7. `H1` | `deduction`
Regression evidence from:
```bash
git -C /tmp/recon-demo/python-dotenv diff v1.0.0..v1.0.1 -- src/dotenv/main.py
```
Relevant diff:
```diff
-        while frame.f_code.co_filename == current_file:
+        while frame.f_code.co_filename == current_file or not os.path.exists(
+            frame.f_code.co_filename
+        ):
             assert frame.f_back is not None
```
This tightened the loop in exactly the way that would keep skipping `<stdin>` frames.

8. `H1` | `induction`
Regression confirmation:
```bash
git -C /tmp/recon-demo/python-dotenv checkout v1.0.0
PYTHONPATH=/tmp/recon-demo/python-dotenv/src python3 - <<'PY'
from dotenv import find_dotenv
print(repr(find_dotenv(raise_error_if_not_found=False)))
PY
```
Output on `v1.0.0`:
```text
''
```
Same stdin repro on `v1.0.1` raised the `AssertionError` above.
Finalize `H1`: the bug is a `v1.0.1` regression in stdin-launched callers.

9. `H1` | `deduction`
Change provenance:
```bash
git -C /tmp/recon-demo/python-dotenv show --stat --oneline 0b94ac0 -- src/dotenv/main.py
```
Output:
```text
0b94ac0 Allow modules using load_dotenv to be reloaded when launched in a separate thread (#497)
 src/dotenv/main.py | 5 ++++-
```
The suspect lines were touched by commit `0b94ac0`.

**Collapsed Final Node**

`H1`: `find_dotenv()` regressed in `v1.0.1` for stdin-launched callers because `_is_interactive()` treats `__main__.__file__ == '<stdin>'` as non-interactive, then the new `or not os.path.exists(frame.f_code.co_filename)` loop in [main.py](/tmp/recon-demo/python-dotenv/src/dotenv/main.py:302) skips synthetic frames until `frame.f_back` becomes `None`, tripping the assertion at [main.py](/tmp/recon-demo/python-dotenv/src/dotenv/main.py:305).  
Confidence: `induction — 93%`

That final node hides the actual in-flight mode sequence:

`abduction -> deduction -> kill -> abduction -> deduction -> induction -> deduction -> induction -> deduction`