fix(server): prune expired replay-protection files from the secrets directory

[t3dotgg]

Every accepted DPoP proof writes a dpop-proof-*.bin file to the secrets directory. Every cloud health or mint request writes two more (a jti marker and a nonce marker). Nothing ever deletes them. A user on T3 Code 0.0.40 with 9 days of uptime had 14,163 files in secrets/ (about 12,200 dpop-proof-*), and the count grew by 250 to 1,200 files a day. A long-running dev machine had about 53,000.

Fix

• apps/server/src/auth/replayMarkers.ts (new): owns the replay marker prefixes, REPLAY_MARKER_MAX_AGE (1 day), the sweep, and the layer.
  • The sweep lists the secrets directory and keeps only names that start with a replay prefix and end in .bin. It removes each match whose mtime is older than 1 day. NotFound is ignored. A file that fails does not stop the sweep. Failures are counted and logged once.
  • The layer runs the sweep after server activation, then every hour. Errors are logged and the loop keeps running.
• apps/server/src/auth/dpop.ts and apps/server/src/cloud/http.ts: export the marker prefixes.
• apps/server/src/server.ts: adds the layer.

Why deleting markers is safe

A marker only matters while its proof can still pass the time check: about 5 minutes for DPoP and 7 minutes for cloud proofs. The time check runs before the marker check, so once a marker is a day old, a replay of its proof fails on time alone. Markers are files, so a restart does not reset them. Two servers that share one secrets directory (for example during a service update) can both sweep for the same reason.

The one tradeoff: after a marker is pruned, only the wall clock blocks a replay. A replay can get through only if the clock moves back by almost a day after a sweep, or if the secrets directory is on a filesystem whose mtimes are almost a day behind. The 1 day max age is chosen so that no realistic clock correction or skew reaches it. The cost is about one day of markers on disk (250 to 1,200 files in the report above).

Why a timer

The report above is from a server with 9 days of uptime, so a startup-only sweep does not bound it. A prune on write would need shared "last swept" state in both the DPoP and cloud handlers. A timer is one background fiber and one directory read per hour. The first sweep removes the existing backlog after activation, off the startup path (about 4 s for 53k files on a Mac).

Tests

• server.test.ts, one test for DPoP token exchange and one for cloud health and mint. Each uses the longest-lived proof the verifier accepts (iat at the maximum future skew, and the maximum cloud lifetime). An immediate replay is rejected by the marker (replay / 409). At REPLAY_MARKER_MAX_AGE, the replay is rejected by the time check (time_window / 401), even though the test never prunes. The tests fail if the max age is shorter than a proof window (checked by setting it to 300 s: both fail).
• replayMarkers.test.ts: every secret name the server stores today (including the provider-env-*, provider-auth-*, and usage-limit-source-* shapes) and a pending .bin.<uuid>.tmp file survive, aged 30 days. Markers of each prefix 1 s past the max age are removed. A marker exactly at the max age stays. The test fails if the age check, the prefix check (checked with a cloud- prefix), the .bin check (checked by removing it), or the remove call is changed.
• Not covered: no test builds the full server runtime, so no test fails if the ReplayMarkers.layer line is removed from server.ts. The other background layers there have the same gap. If the line is lost, the result is today's behavior (files pile up), not weaker replay protection.

Verification: vp test run on replayMarkers.test.ts, server.test.ts, ServerSecretStore.test.ts, auth/dpop.test.ts, and cloud/http.test.ts. vp lint and vp fmt on the changed files. vp run --filter t3 typecheck.

Related

• Closes [Bug]: DPoP replay markers grow without bound #9040, which reports the DPoP marker growth.
• #8845 bounds DPoP replay state with a new bucketed store. It covers DPoP only, needs a stop-all-servers upgrade step, and leaves existing files in place. This PR also covers the cloud markers and removes the existing backlog. If this PR merges, close fix(server): bound DPoP replay state #8845 as superseded so two replay-state designs do not both land.
• #10579 changes how create writes files. Its .create-* temp directories do not match a marker prefix, so the sweep skips them.

Made by Claude Opus 5.5 (1M context) in Claude Code, running in T3 Code.

🤖 Generated with Claude Code

Summary by CodeRabbit

• Bug Fixes
  • Expired DPoP and cloud authentication replay markers are now cleared automatically after one day. Cleanup runs when the server starts and repeats hourly, preventing outdated markers from lingering.
  • Markers at the one-day limit are retained, and active markers continue to block replayed proofs. Cleanup can continue when individual marker files cannot be processed.

[github-actions]

Thread transfer impact

✅ Thread transfer remains within every enforced ceiling.

Provider	Metric	Main baseline	This PR	Impact	PR ceiling
Codex	Total thread wire	13.5 KiB	13.5 KiB	+8 B (+0.1%)	15.1 KiB	✅
Codex	Thread snapshot wire	7.1 KiB	7.1 KiB	−1 B (−0.0%)	7.3 KiB	✅
Codex	Live turn WebSocket wire	6.4 KiB	6.5 KiB	+9 B (+0.1%)	7.8 KiB	✅
Codex	Live turn WebSocket decoded	56.3 KiB	56.3 KiB	0 B (0.0%)	66.4 KiB	✅
Codex	Live turn messages	10	10	0 (0.0%)	21	✅
Claude	Total thread wire	13.5 KiB	13.5 KiB	+53 B (+0.4%)	15.1 KiB	✅
Claude	Thread snapshot wire	7.1 KiB	7.1 KiB	+9 B (+0.1%)	7.3 KiB	✅
Claude	Live turn WebSocket wire	6.4 KiB	6.5 KiB	+44 B (+0.7%)	7.8 KiB	✅
Claude	Live turn WebSocket decoded	57.0 KiB	57.1 KiB	+44 B (+0.1%)	66.4 KiB	✅
Claude	Live turn messages	9	10	+1 (+11.1%)	21	✅

Baseline: dd8332d · PR result: 96da007 · Source CI: success

Scenario and decoded snapshot size

10 historical turns, 5 command tools per turn, 878.9 KiB retained MCP result per historical turn, and a 1.05 MiB retained result in the measured turn.

• Codex decoded thread snapshot: 114.0 KiB
• Claude decoded thread snapshot: 114.7 KiB

Updated in place by a trusted workflow. PR artifacts are strictly validated and never executed.

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📝 Walkthrough

Walkthrough

The server now removes expired DPoP and cloud replay-marker files from the secrets directory. It runs the pruning sweep after server activation and hourly. Tests cover the age cutoff and replay responses before and after marker expiry.

Changes

Replay marker pruning

Layer / File(s)	Summary
Replay-marker prefixes and pruning sweep apps/server/src/auth/dpop.ts, apps/server/src/cloud/http.ts, apps/server/src/auth/replayMarkers.ts, apps/server/src/auth/replayMarkers.test.ts	The code defines DPoP and cloud marker prefixes and removes matching .bin files with modification times strictly older than one day. The test checks expired markers, a marker at the cutoff, ordinary secrets, and a pending temporary file.
Runtime scheduling and replay-expiry coverage apps/server/src/server.ts, apps/server/src/auth/replayMarkers.ts, apps/server/src/server.test.ts	The server starts pruning after activation and repeats it hourly. Tests check DPoP and cloud replay responses before and after marker expiry.

Priority: ➖ Normal

Estimated code review effort: 3 (Moderate) | ~20 minutes

Change: Bug fix · Severity of issue fixed: Medium

Sequence Diagram(s)

sequenceDiagram
  participant ServerRuntime
  participant ReplayMarkers
  participant SecretsDirectory
  ServerRuntime->>ReplayMarkers: start pruning after activation and every hour
  ReplayMarkers->>SecretsDirectory: scan matching .bin files and inspect modification times
  ReplayMarkers->>SecretsDirectory: remove files older than one day

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Suggested reviewers: juliusmarminge

Merge Risk: 🟡 Moderate · up to 96da0

Replay-marker files will accumulate well beyond the intended retention window. Correct the cutoff and sweep interval before merging.

🚥 Pre-merge checks | ✅ 3 | ❌ 2

❌ Failed checks (2 warnings)

Check name	Status	Explanation	Resolution
Linked Issues check	⚠️ Warning	Issue #9040 requires bounded replay-state retention during the proof acceptance window and bootstrap-credential validation before replay-state writes. The PR adds pruning for DPoP and cloud marker fil…	Set replay-marker retention to the required proof-window bound, including a safety margin that matches the stated objective. Validate the bootstrap credential before calling verifyRequestDpopProof, or otherwise prevent replay-state creati…
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 2 functions across 10 files.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (3 passed)

Check name	Status	Explanation
Out of Scope Changes check	✅ Passed	The pruning layer, marker-prefix constants, server wiring, and retention tests directly support Issue #9040's bounded replay-state objective. Cloud replay-marker cleanup is part of the stated generali…
Title check	✅ Passed	The title clearly and concisely identifies the primary change: pruning expired replay-protection files from the server secrets directory.
Description check	✅ Passed	The description clearly explains the problem, implementation, safety rationale, timer behavior, tests, verification steps, and related issues. It does not include the template checklist, but the requi…

Full details: Linked Issues check

Explanation

Issue #9040 requires bounded replay-state retention during the proof acceptance window and bootstrap-credential validation before replay-state writes. The PR adds pruning for DPoP and cloud marker files, and tests the one-day mtime boundary. The current REPLAY_MARKER_MAX_AGE is one day, while the documented proof windows are about five to seven minutes, so retention is not limited to the acceptance window. In auth/http.ts, verifyRequestDpopProof runs before exchangeBootstrapCredentialForAccessToken; an invalid bootstrap credential can therefore leave a replay marker. No test proves that this invalid-credential path creates no marker.

Resolution

Set replay-marker retention to the required proof-window bound, including a safety margin that matches the stated objective. Validate the bootstrap credential before calling verifyRequestDpopProof, or otherwise prevent replay-state creation until credential validation succeeds. Add an automated test that submits an invalid bootstrap credential with a valid DPoP proof and verifies that no replay marker is written.

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In `@apps/server/src/auth/ServerSecretStore.ts`:
- Around line 345-346: Update ReplayMarkerPruneLive and the replay-marker
creation flow to use the same cross-process lock; while holding it, revalidate
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📒 Files selected for processing (7)

• apps/server/src/auth/ServerSecretStore.test.ts
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• apps/server/src/auth/dpop.ts
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• apps/server/src/server.ts
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Approvability

Verdict: Not approved

Macroscope's review found this PR not approvable — This production change adds an hourly cleanup process that deletes expired DPoP and cloud authentication replay markers from the secrets directory. The scope and tests are focused, but modifying authentication replay handling and auth-directory code makes the change sensitive and warrants human review.

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In `@apps/server/src/auth/replayMarkers.ts`:
- Line 38: Treat a missing secrets directory as an empty sweep by handling only
the NotFound error from fileSystem.readDirectory(secretsDir) as an empty entry
list before filtering markers; allow other errors, including PermissionDenied,
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Inline comments:
In `@apps/server/src/auth/replayMarkers.ts`:
- Line 25: Update REPLAY_MARKER_MAX_AGE in replay-marker retention to 14 minutes
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