fix(server): Codex V2 sessions use the configured launch arguments

[juliusmarminge]

The Codex provider's "Launch arguments" setting and the T3CODE_CODEX_LAUNCH_ARGS override did nothing for real V2 sessions. The V2 client factory spawned codex app-server with hard-coded arguments, so flags like -c model_reasoning_summary=detailed, --enable <feature>, or --strict-config were dropped. The readiness probe, skills probe, reset-credit call, and text generation all honor them. So did the V1 runtime that is being removed.

Change

codexAppServerClientFactoryFromSettingsLayer now builds its args with codexAppServerArgs(resolveCodexLaunchArgs(input.settings.launchArgs, input.environment)), the same resolution the probe uses. input.environment is the instance environment the driver merges over the host env, so the env override takes precedence over the setting exactly as it does for the probe. This doesn't use codexSessionAppServerArgs, which #13462 removes.

Verification

• New test in CodexAdapterV2.test.ts ("launches the app-server with the configured launch arguments"). It drives the real codexAppServerClientFactoryFromSettingsLayer with a spawner that records the command, and asserts the args for configured launch args and for the T3CODE_CODEX_LAUNCH_ARGS override winning over them.
• Revert check: with the old hard-coded ["app-server"] restored, the test fails with expected [ [ 'app-server' ], [ 'app-server' ] ].
• Live check with Codex 0.156.1, using a throwaway test that isn't committed: I opened sessions through the same factory against a temp CODEX_HOME and read back config/read. model_reasoning_summary was "detailed" from the setting, "concise" from the env override, and null with neither. With the fix reverted, all three came back null.
• vp test run src/orchestration-v2/Adapters/CodexAdapterV2.test.ts src/provider/Layers/codexLaunchArgs.test.ts: 121 passed.
• vp exec tsc --noEmit -p . in apps/server: no errors.
• vp lint on the two touched files: no new warnings. The two existing unused-variable warnings in CodexAdapterV2.ts are unrelated.
• Not run: repo-wide checks and the replay fixture suite. This path only touches process spawn args, which replay fixtures bypass.

Model: Claude Opus 5.5 (Claude Code)

🤖 Generated with Claude Code

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[macroscopeapp]

Approvability

Verdict: Not approved

Macroscope's review found this PR not approvable — This fixes Codex V2 session spawning so existing launch-argument configuration is honored and adds focused coverage for settings and environment precedence. Because those arguments can materially alter the behavior of the production Codex app-server process, the change warrants human review.

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[github-actions]

Thread transfer impact

✅ Thread transfer remains within every enforced ceiling.

ℹ️ No successful main baseline artifact is available yet. This run establishes the initial measurement.

Provider	Metric	Main baseline	This PR	Impact	PR ceiling
Codex	Total thread wire	—	4.9 KiB	—	6.8 KiB	✅
Codex	Thread snapshot wire	—	3.7 KiB	—	4.9 KiB	✅
Codex	Live turn WebSocket wire	—	1.2 KiB	—	2.0 KiB	✅
Codex	Live turn WebSocket decoded	—	20.4 KiB	—	29.3 KiB	✅
Codex	Live turn messages	—	2	—	8	✅
Claude	Total thread wire	—	4.9 KiB	—	6.8 KiB	✅
Claude	Thread snapshot wire	—	3.7 KiB	—	4.9 KiB	✅
Claude	Live turn WebSocket wire	—	1.2 KiB	—	2.0 KiB	✅
Claude	Live turn WebSocket decoded	—	20.8 KiB	—	29.3 KiB	✅
Claude	Live turn messages	—	2	—	8	✅

Baseline: unavailable · PR result: 90d6ed9 · 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: 106.1 KiB
• Claude decoded thread snapshot: 106.4 KiB

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