Hosted PDM rollback reports success but leaves the patch url/hash in pdm.lock after `pdm add` or `pdm lock --update-reuse` and a re-scan

[mikolalysenko]

[agent] Found by the scheduled PDM bug-hunt routine (ledger #312).

Summary

After a hosted pdm.lock rewrite, some PDM commands re-render the urllib3 block but keep our patch data:

• pdm add <other> and pdm lock --update-reuse on PDM 2.26 and 2.29 keep the patch url and the patched hash.
• On PDM 2.12 – 2.20, pdm add drops the url but keeps the patched files hash.

The first rollback then fails closed with a drift error that says to "re-run scan --mode hosted to normalize". After that re-scan, rollback reports success, lists reverted: ["pkg:pypi/urllib3@1.26.18"] and deletes the redirect ledger. But pdm.lock still carries the patch data:

• PDM 2.26 / 2.29: the lock keeps the hosted url and the patched sha256. The project stays silently hosted-patched, with no ledger left, so no CLI path back to the registry lock remains.
• PDM 2.12 / 2.20: the lock keeps the patched sha256 with no url, i.e. a registry source pinned to the patched wheel's hash. pdm sync then fails (InstallationError: Some package operations failed). Rollback leaves an uninstallable lock and reports success.

The re-scan treats the still-patched block as the pristine original and records it as the edit's original fragment. So the rebase is pristine → pristine instead of pristine → current.

Impact

Rollback silently lies. CI or a user who runs rollback to un-patch believes the project is back on upstream bytes. It is not, and on 2.12 – 2.20 it no longer installs at all. The doc's guarantee is broken: docs/testing/pdm-compatibility.md:64-67 says "A re-scan after a relock re-applies the patch and rebases the ledger's recorded edits onto the relocked text (pristine → current…), so rollback still lands on the pristine lock afterwards."

Repro (Linux, real PDM, mock patch API serving a real patched wheel)

printf '[project]\nname="proj"\nversion="0.1.0"\nrequires-python=">=3.8"\ndependencies=["urllib3==1.26.18"]\n[tool.pdm]\ndistribution=false\n' > pyproject.toml
pdm lock
socket-patch scan --mode hosted --json --yes $API     # redirected 1
pdm add six==1.16.0                                    # keeps url= (2.29) / keeps patched hash only (2.20)
socket-patch rollback --json --yes $API                # partial_failure: "content matches neither ... re-run `scan --mode hosted` to normalize"
socket-patch scan --mode hosted --json --yes $API      # success, redirected 1
socket-patch rollback --json --yes $API                # success, reverted [pkg:pypi/urllib3@1.26.18], editedFiles 1
grep -c '^url = ' pdm.lock                             # 1 on 2.29.2  (expected 0)
grep -c 1497f1666ebc pdm.lock                          # 1 = patched wheel sha256 still pinned (expected 0)
ls .socket/vendor/redirect-state.json                  # gone
pdm sync                                               # 2.29.2: installs the PATCHED urllib3; 2.12.4/2.20.1: InstallationError

($API = --api-url http://127.0.0.1:<port> --api-token fake --org test against a local mock of /patches/batch, /patches/view, /patches/package. The mock serves an urllib3 1.26.18 wheel with a marker line appended to urllib3/response.py. No Socket token was used.)

Reproduced on 2 of 2 fresh runs on 2.29.2, and also without the intermediate failed rollback. A plain pdm lock, which re-resolves to the registry, is not affected: rollback lands on the relocked registry block there, as documented.

Expected vs actual

• Expected: after scan → relock-style edit → scan → rollback, the urllib3 block has no Socket url and the upstream files hashes, per the doc quoted above. Otherwise rollback should fail closed rather than report success.
• Actual: status: success, reverted: [purl], ledger removed, and the patched url/hash left in pdm.lock.

Matrix (Linux; the rewrite is platform-independent text handling)

PDM	post-rewrite command	after re-scan + rollback	pdm sync afterwards
2.29.2	pdm add six==1.16.0	url + patched hash remain	installs patched
2.29.2	pdm lock --update-reuse	url + patched hash remain	installs patched
2.29.2	pdm lock	clean (registry) ✅	upstream
2.26.9	pdm add six==1.16.0	url + patched hash remain	installs patched
2.20.1	pdm add six==1.16.0	patched hash, no url	fails
2.12.4	pdm add six==1.16.0	patched hash, no url	fails

macOS and Windows were not run for this one. The defect is in lock-text handling, which has no OS-specific code path.

Suspect code

• crates/socket-patch-core/src/utils/pdm_lock.rs:383-399: plan_pdm_rewrite accepts an existing prior-hosted url (is_prior_hosted_url), then pdm_lock_fragments_in at :266 records that already-redirected block as the before/original fragment. A block whose files hash equals the patched artifact's sha256 (no url) is likewise taken as pristine.
• The rebase (pristine → current) for re-scans of hosted PDM edits should keep the ledger's earlier original when the current fragment still carries our URL or our artifact hash.

Tested on main f6b7fb9 (latest release v4.0.0).

[mikolalysenko]

[agent] Triaged: priority:p1 (PDM). Not a duplicate, and no existing fix PR. The cause is in utils/pdm_lock.rs: a re-scan records a block that is already hosted (our url, or our artifact sha256 with no url) as the pristine original fragment, when it should keep the ledger's earlier original.

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[mikolalysenko]

[agent] Claiming this issue (shared root cause: the hosted ledger's PDM rebase always adopts the re-scan's original fragment, even when that fragment still carries Socket's url or patched hash). Branch: agent/fix-pdm-rebase-keeps-pristine. Claim-ID: 2026-09-30T20:20:37Z-fb6405

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Generated by Claude Code

[mikolalysenko]

[agent] Draft PR: #375

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Generated by Claude Code

[mikolalysenko]

[agent] Re-triage (PDM bug-hunt, ledger #312): this no longer reproduces on main 2463257 (#277, v5). v5 hosted mode keeps no ledger, and rollback restores the pin from PyPI metadata instead of replaying a recorded fragment.

Tested on Linux with real PDM against the mock patch API:

Flow	PDM 2.12.4	2.20.1	2.29.2
hosted scan → pdm add six → re-scan → rollback	exit 0, 0 patch refs left, pdm sync OK	—	exit 0, 0 refs, pdm sync OK
hosted scan → add dep + pdm lock --update-reuse → re-scan → rollback	—	exit 0, 0 refs (the patched-hash-without-url state is now restored too), pdm sync and pdm lock --check OK	exit 0, 0 refs, sync and check OK

"Refs" counts lines in pdm.lock matching the hosted URL or the patched wheel sha256. Closing as fixed by #277. PR #375 targets the removed v4 ledger path.

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