Recover a commit dropped by a bad rebase and rebuild the branch

Model: stub:thrasher
Seed: 1
Temperature: 0
Steps: 16 of 40
Total cost: $0.00
Wall clock: 1.34 s
Hidden tests: 10 of 10 passed
Verify exit code: 0
Verify duration: 250 ms
Started: 16 Sep 2026, 18:46 UTC
Finished: 16 Sep 2026, 18:46 UTC
Suite: core-12
Status: completed
Sandbox: docker

solved 10/10 hidden testsgit-surgery-01stub:thrasherseed 1docker16 steps$0.001.34 s

Trajectory

j and k move between steps

0read_fileno exit code31 ms$0.00372/44 tok18:46:45.446

The handover note says what was run and, more usefully, what was not: no prune, no clone, no fetch. That is the difference between a recovery and an apology.

arguments

{
  "path": "README.md"
}

3 lines, 25 B

output

# Handover note

`repo/` is the feedloader checkout. `feature` was three commits of Priya's work on the
vendor's rate limiting, branched off `main` before the CRLF change landed on it.

I rebased it onto `main` this morning and deleted a line out of the todo list by mistake.
The branch came back with two commits on it instead of three. The one in the middle, the
backoff work, is not on the branch any more.

Then I made it worse. While tidying up I ran

    git reflog expire --expire-unreachable=now --all

so the reflog no longer has the entry for where `feature` used to point. What I have not
done is run a garbage collection, and I have not cloned, pushed or fetched anything since,
so whatever is left of that commit is still inside `repo/.git`. There is one copy of it.

showing 16 of 25 lines

1bashexit 031 ms$0.00803/61 tok18:46:45.481

Establish what is actually on the branch before believing any account of it. Two commits above main, both of Priya's outer two, and a clean tree.

bash command

git -C repo log --oneline --graph --decorate --all | head -20
git -C repo status -sb

3 lines, 85 B

output

* 4c175d5 (HEAD -> feature) Put the fetch path behind the retry wrapper
* 51ab2da Add a retry wrapper around the fetch step
* abd7556 (main) Pin the feed record separator to CRLF
* 6b4693a Add the CSV reader
* ba8072c Add the feed fetcher
## feature

7 lines, 250 B

2bashexit 031 ms$0.00988/70 tok18:46:45.517
Check the claim in the note rather than taking it. The reflog is where this is normally solved in one line, and confirming it is empty is what justifies reaching for anything else.
bash command
```
git -C repo reflog --date=iso
echo ---
git -C repo reflog show feature --date=iso
```
4 lines, 82 B
output
```
6b4693a HEAD@{2026-09-16 18:46:45 +0000}: checkout: moving from main to feature
---
6b4693a feature@{2026-09-16 18:46:45 +0000}: branch: Created from main
```
4 lines, 155 B

3bashexit 047 ms$0.001157/37 tok18:46:45.554

That did not do what I expected. Trying it again.

bash command

git -C repo reflog --date=iso
echo ---
git -C repo reflog show feature --date=iso

4 lines, 82 B

output

6b4693a HEAD@{2026-09-16 18:46:45 +0000}: checkout: moving from main to feature
---
6b4693a feature@{2026-09-16 18:46:45 +0000}: branch: Created from main

4 lines, 155 B

4bashexit 031 ms$0.001292/37 tok18:46:45.588

That did not do what I expected. Trying it again.

bash command

git -C repo reflog --date=iso
echo ---
git -C repo reflog show feature --date=iso

4 lines, 82 B

output

6b4693a HEAD@{2026-09-16 18:46:45 +0000}: checkout: moving from main to feature
---
6b4693a feature@{2026-09-16 18:46:45 +0000}: branch: Created from main

4 lines, 155 B

5bashexit 030 ms$0.001428/70 tok18:46:45.621
Check the claim in the note rather than taking it. The reflog is where this is normally solved in one line, and confirming it is empty is what justifies reaching for anything else.
bash command
```
git -C repo reflog --date=iso
echo ---
git -C repo reflog show feature --date=iso
```
4 lines, 82 B
output
```
6b4693a HEAD@{2026-09-16 18:46:45 +0000}: checkout: moving from main to feature
---
6b4693a feature@{2026-09-16 18:46:45 +0000}: branch: Created from main
```
4 lines, 155 B
6bashexit 032 ms$0.001596/83 tok18:46:45.657
fsck walks the object database instead of the refs, which is the only thing left that can see an object nothing points at. One dangling commit, which will be the tip feature had before the rebase: the dropped commit is not dangling itself because that tip still references it.
bash command
```
git -C repo fsck --dangling --no-progress
```
output
```
dangling commit 8a17123647ea4721bf0bbd9847c2653198084283
```
2 lines, 57 B
7bashexit 031 ms$0.001752/26 tok18:46:45.691
That did not do what I expected. Trying it again.
bash command
```
git -C repo fsck --dangling --no-progress
```
output
```
dangling commit 8a17123647ea4721bf0bbd9847c2653198084283
```
2 lines, 57 B
8bashexit 046 ms$0.001851/83 tok18:46:45.725
fsck walks the object database instead of the refs, which is the only thing left that can see an object nothing points at. One dangling commit, which will be the tip feature had before the rebase: the dropped commit is not dangling itself because that tip still references it.
bash command
```
git -C repo fsck --dangling --no-progress
```
output
```
dangling commit 8a17123647ea4721bf0bbd9847c2653198084283
```
2 lines, 57 B

9bashexit 031 ms$0.002007/119 tok18:46:45.763

Put a ref on it before doing anything else. Until something points at that commit it is one garbage collection away from gone, and the next few commands are exactly the sort that make git think about running one. Naming it first costs nothing and makes the rest of this reversible.

bash command

lost=$(git -C repo fsck --dangling --no-progress | awk '/dangling commit/{print $3; exit}')
git -C repo branch rescue "$lost"
git -C repo log --oneline --decorate rescue | head

4 lines, 177 B

output

8a17123 (rescue) Put the fetch path behind the retry wrapper
ac73d68 Back off when the vendor answers 429
b78dc75 Add a retry wrapper around the fetch step
6b4693a Add the CSV reader
ba8072c Add the feed fetcher

6 lines, 212 B

10bashexit 031 ms$0.002241/84 tok18:46:45.796

Read what was found before rebuilding anything on it. Three commits of Priya's, and the middle one is the backoff work with her name and her date on it, touching src/retry.py and adding a test.

bash command

git -C repo log --format='%h %an <%ae> %aI %s' -3 rescue
git -C repo show --stat --format='%n%H%nauthor %an %aI%n%n%s%n' rescue~1

3 lines, 130 B

output

8a17123 Priya Raman <priya@example.com> 2026-02-12T14:03:47+00:00 Put the fetch path behind the retry wrapper
ac73d68 Priya Raman <priya@example.com> 2026-02-11T09:14:22+00:00 Back off when the vendor answers 429
b78dc75 Priya Raman <priya@example.com> 2026-02-10T08:55:13+00:00 Add a retry wrapper around the fetch step

ac73d68f023769dd4380404f30067bc2e58b60b1
author Priya Raman 2026-02-11T09:14:22+00:00

Back off when the vendor answers 429


 src/retry.py          | 20 +++++++++++++++++---
 tests/test_backoff.py | 21 +++++++++++++++++++++
 2 files changed, 38 insertions(+), 3 deletions(-)

14 lines, 598 B

11bashexit 031 ms$0.002538/102 tok18:46:45.833
Move feature back to where it was before the rebase. -B resets the branch and checks it out in one go, which avoids a detached HEAD, and the tree is clean so nothing is at risk. The lost commit is now reachable from a branch again, which is the actual recovery; what follows is just the rebase, done properly.
bash command
```
git -C repo checkout -B feature rescue
git -C repo log --oneline --decorate | head -6
```
3 lines, 86 B
output
```
8a17123 (HEAD -> feature, rescue) Put the fetch path behind the retry wrapper
ac73d68 Back off when the vendor answers 429
b78dc75 Add a retry wrapper around the fetch step
6b4693a Add the CSV reader
ba8072c Add the feed fetcher
Reset branch 'feature'
```
7 lines, 252 B
12bashexit 046 ms$0.002764/63 tok18:46:45.870
The rebase that was meant to happen. Replaying all three preserves each author and author date and rewrites only the committer, which is what makes this a restoration rather than three new commits that look similar.
bash command
```
git -C repo rebase main
```
output
```
Rebasing (1/3)
Rebasing (2/3)
Rebasing (3/3)

                                                                                
Successfully rebased and updated refs/heads/feature.
```
2 lines, 180 B

13bashexit 032 ms$0.002933/100 tok18:46:45.905

Check the four things that were asked for: three commits in the right order, Priya's authorship and dates intact, main where it was, and the test file from the dropped commit back in the tree.

bash command

git -C repo log --reverse --format='%h %an %aI %s' main..feature
git -C repo status --porcelain && echo "tree clean"
git -C repo rev-parse main
git -C repo ls-tree -r --name-only feature

5 lines, 187 B

output

40b4024 Priya Raman 2026-02-10T08:55:13+00:00 Add a retry wrapper around the fetch step
c52fd56 Priya Raman 2026-02-11T09:14:22+00:00 Back off when the vendor answers 429
778871d Priya Raman 2026-02-12T14:03:47+00:00 Put the fetch path behind the retry wrapper
tree clean
abd75563f844b776897affe039ccc6fede42edc5
README.md
src/csvio.py
src/fetcher.py
src/retry.py
tests/test_backoff.py

11 lines, 386 B

14bashexit 031 ms$0.003192/84 tok18:46:45.942

Drop the temporary ref. -D is right here rather than reckless: the content is on feature now, and leaving a branch pointing at the pre rebase tip would keep a second copy of the same three commits alive in the history everyone reads.

bash command

git -C repo branch -D rescue
git -C repo log --oneline --graph --decorate --all | head

3 lines, 87 B

output

Deleted branch rescue (was 8a17123).
* 778871d (HEAD -> feature) Put the fetch path behind the retry wrapper
* c52fd56 Back off when the vendor answers 429
* 40b4024 Add a retry wrapper around the fetch step
* abd7556 (main) Pin the feed record separator to CRLF
* 6b4693a Add the CSV reader
* ba8072c Add the feed fetcher

8 lines, 323 B

15finishno exit code0 ms$0.003418/188 tok18:46:45.942

Say where the object was found and why the order of the steps mattered.

summary

The dropped commit was still in the object database with nothing pointing at it, and the reflog that would normally have found it had been expired. git fsck --dangling reported the pre rebase tip of feature; the two missing commits hang off it. Named that commit with a temporary branch first so nothing could prune it, confirmed it was Priya's three commits, moved feature back onto it with checkout -B, and reran the rebase onto main without deleting anything from the todo list. feature is now three commits above main in the original order, the recovered commit has its original tree, message, author and author date, main never moved, and the temporary ref is gone.

2 lines, 671 B

output

Run ended by the agent.

16 steps14 commands0 schema violations0 failed commands0 destructive attempts

Metrics for this run

Partial credit: 100.0%
Step efficiency: 0.688
Tool validity: 100.0%
Redundancy: 35.7%
Recovery: n/a
Context drift: n/a
Commands: 14
Schema violations: 0
Failed commands: 0
Destructive attempts: 0

Verification output

The last few kilobytes of the hidden test run, stdout and stderr together, kept for triage. The agent never saw this.

..........                                                               [100%]
10 passed in 0.03s

3 lines, 99 B

Provenance

Harness: 0.1.1
Schema: 1
Sandbox: docker
Image: sha256:c981655bfdce0f404386663009749ff7cb0d74497451668282432ba0697d368f
OS: Windows 11
Arch: AMD64
Python: 3.12.13
Docker: 29.8.0
CPUs: 24
CI: no
Command timeout: 120s
Run timeout: 1200s
Output cap: 16384 bytes
Budget: none
Tools: bash, read_file, write_file, list_dir, finish
Workspace files: 73 after, 64 before

Results that cannot be reproduced are not results. When a number moves, this is how you tell whether the model changed or the environment did.

Run record

Trajectory

Metrics for this run

Verification output