fix: give the Pi runner a session identity, so continuity actually happens

[bborbe]

The defect

PersistSession omitted --no-session and nothing else. From pi's own --help:

--print, -p          Non-interactive mode: process prompt and exit
--continue, -c       Continue previous session
--session-id <id>    Use exact project session ID, creating it if missing
--no-session         Don't save session (ephemeral)

--no-session governs whether pi writes the transcript. Reading it back is a different flag. So an agent configured for continuity saved every conversation and remembered none of them — observed live:

• turn 1 → ACK
• turn 2 → {"status":"failed","message":"No token was previously requested to be remembered"}

which is precisely what a fresh session says.

The fix

PiRunnerConfig.SessionID passes pi's --session-id. --session-id rather than --continue deliberately: it creates the session when it is missing, so a brand-new agent's first prompt behaves exactly like its thousandth — --continue would be resuming nothing on that first run.

Left empty for a task-routed agent, whose runs are unrelated tasks that must not be joined into one identity.

Why it got through

The plan that scoped the work said:

runs pi --print --mode json --no-session, so session storage in the PVC-mounted ~/.pi/agent/ is never written. The delta is dropping --no-session.

The first clause is true; the second does not follow. Writing a session and continuing one are different flags, and nothing exercised the difference until a second prompt was sent to the same pod. PersistSession was implemented, reviewed, and unit-tested on both sides without anyone asking whether the flag it removes is the flag that resumes.

Tests

9 of 9 specs in the pi package, up from 7 — two new: --session-id is passed when configured, and no --session-id is passed when it is not. make precommit PASS — go test -race all 10 packages, golangci-lint 0 issues, gosec clean, trivy 0 vulns / 0 secrets, osv clean.

[ben-s-pull-request-reviewer]

CHANGELOG has ## Unreleased with a fix: prefix — standard convention. All three concerns from the plan are addressed. No issues found.

Summary

The fix adds SessionID to PiRunnerConfig and passes --session-id to the pi CLI when set. The bug: PersistSession=true only omitted --no-session (writing control), but reading the session back requires --session-id. An agent with persistence but no session ID saved every conversation and remembered none.

Verification:

• pi/pi-runner.go:108-110 — correctly appends --session-id when SessionID != "", complementing PersistSession
• pi/pi-runner-config.go:31-48 — PersistSession docs correctly distinguish write vs read; SessionID docs correctly explain why --session-id (not --continue) and when to leave it empty
• pi/pi-runner_test.go:100-116 — both cases tested: session ID present and absent

No issues found.

---

{
  "verdict": "approve",
  "summary": "Bugfix correctly adds the missing --session-id flag that makes session continuity work. PersistSession only controls writing the transcript; --session-id is the separate flag that allows reading it back. Two new specs cover both configured and unconfigured cases. Documentation clearly explains the relationship between the two flags.",
  "comments": [],
  "concerns_addressed": [
    {
      "concern": "correctness: PersistSession removed --no-session but that flag only controls writing; reading requires --session-id",
      "disposition": "addressed",
      "detail": "pi-runner.go:108-110 adds --session-id when SessionID != ''; pi-runner-config.go:31-48 documents the write/read distinction correctly"
    },
    {
      "concern": "correctness: New SessionID field documentation must correctly distinguish --no-session from --session-id",
      "disposition": "addressed",
      "detail": "pi-runner-config.go:31-48 explains PersistSession controls writing and SessionID controls reading; explains why --session-id (not --continue)"
    },
    {
      "concern": "tests: Two new specs added — verify both exercise buildCommand fully",
      "disposition": "addressed",
      "detail": "pi-runner_test.go:100-116 tests --session-id passed when configured and omitted when not, both via the buildCommand path using the shim"
    }
  ]
}