feat(auth): make the default session lifetime configurable

[yashranaway]

Direct-pairing sessions always expire after 30 days, so private server operators must re-pair active devices every month. Add T3CODE_SESSION_TTL, accepting finite positive durations such as 90 days, for newly issued sessions.

The default stays at 30 days. Explicit TTLs, including one-hour relay credentials, take precedence; existing sessions retain their expiry. Document the setting in the remote-access guide.

Fixes #13055.

Validation: 27 session-store tests, server typecheck and targeted lint passed. The configured-lifetime regression fails before the change. Tests cover browser and bearer sessions, expiry, explicit overrides and invalid configuration.

Model: GPT-6
Harness: Codex in T3 Code

Summary by CodeRabbit

• New Features

  • Session expiration can be configured with the T3CODE_SESSION_TTL environment variable.
  • Positive finite durations, such as 90 days, are supported; the default remains 30 days.
  • Configuration applies to new sessions after the server restarts.

• Bug Fixes

  • Invalid, non-positive, or non-finite lifetime values are rejected.

• Documentation

  • Clarified that existing sessions retain their original expiry.
  • Documented precedence for explicit lifetimes and short-lived credentials.
  • Clarified that session activity does not extend expiration.

[macroscopeapp]

Approvability

Verdict: Not approved

Macroscope's review found this PR not approvable — The production authentication path now derives newly issued session expiry from a configurable environment value, with invalid values affecting SessionStore initialization. This changes product-default behavior in a sensitive auth package and warrants human review.

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📝 Walkthrough

Walkthrough

The session store now reads T3CODE_SESSION_TTL for the default session lifetime. It validates positive finite durations and uses a 30-day fallback when the variable is unset. Tests and documentation cover the resulting expiry rules.

Changes

Session lifetime configuration

Layer / File(s)	Summary
Session TTL configuration and issuance apps/server/src/auth/SessionStore.ts	SessionStore reads and validates T3CODE_SESSION_TTL, defaults to 30 days when unset, and uses the resolved duration when no explicit TTL is supplied.
Lifetime behavior validation and documentation apps/server/src/auth/SessionStore.test.ts, docs/user/remote-access.md	Tests cover default and configured lifetimes, explicit TTL precedence, expiration, and invalid values. Documentation describes configuration and expiry rules.

Priority: ➖ Normal

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

Change: Feature

Sequence Diagram(s)

sequenceDiagram
  participant SessionStore
  participant ConfigProvider
  participant SessionToken
  SessionStore->>ConfigProvider: Read T3CODE_SESSION_TTL
  ConfigProvider-->>SessionStore: Return validated duration or 30-day default
  SessionStore->>SessionToken: Issue session with defaultSessionTtl

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Merge Risk: ⚪ Minimal · up to 6097e

The change configures the default lifetime of newly issued sessions while preserving existing expiries and explicit overrides; no merge-blocking risk is identified.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
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 1 functions across 2 files. (1 skipped: 1 …	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Linked Issues check	✅ Passed	Issue #13055 requests a configurable lifetime for pairing-issued sessions. SessionStore.ts reads T3CODE_SESSION_TTL, validates finite positive durations, and keeps a 30-day default. The configured…
Out of Scope Changes check	✅ Passed	The changes remain within Issue #13055. The source change adds the requested session-lifetime configuration. The tests verify the related session-store behavior. The documentation describes configurat…
Title check	✅ Passed	The title is concise, uses conventional commit format, and clearly identifies the main change: configurable default session lifetime.
Description check	✅ Passed	The description explains the problem, change, scope, issue reference, verification coverage, observed results, and agent details. It also states default behavior, precedence rules, and existing-sessio…

Full details: Docstring Coverage

Explanation

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 1 functions across 2 files. (1 skipped: 1 unsupported.)

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Actionable comments posted: 1

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Inline comments:
In `@docs/user/remote-access.md`:
- Around line 154-155: Update the T3CODE_SESSION_TTL documentation to require a
finite, positive duration, preserving the existing example and surrounding
guidance.

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📒 Files selected for processing (3)

• apps/server/src/auth/SessionStore.test.ts
• apps/server/src/auth/SessionStore.ts
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[juliusmarminge]

Note

This comment is posted by Julius' dot

The issue triage asks for a product decision before choosing an absolute TTL override, sliding expiry or durable device authentication. This PR keeps the 30-day default and configures new sessions only. Maintainers, does that satisfy the requested decision under the configuration exception, or should it wait? Leaving this open pending clarification.

[yashranaway]

This PR only configures the existing absolute lifetime for new sessions and preserves the 30-day default. It does not add sliding expiry or durable device authentication. I will keep the scope unchanged while the requested product decision remains pending.

[cal88]

This would fix it for my setup: 0.0.45 as a systemd user service, loopback-only behind Tailscale Serve, one operator. Once it's in a release, the plan is a drop-in next to the existing ones, something like:

[Service]
Environment=T3CODE_SESSION_TTL=365 days

then a service restart and one last pairing per device. Keeping the 30-day default and leaving existing sessions alone both look right to me. Hoping the decision in #13055 lets this land.