[veoery]

Change

Adds Pi (pi, v1.5.0) as a third CLI Base Agent beside codex and claude, as one CliAgent subclass. It can act (agent.base: pi) and learn (the new pi Evolver).

• Layer 1: a <backend>/<model> reference becomes Pi's models.json provider entry (Binding.pi_provider): the key written as $VARIABLE (never the value), the backend's price, and the first dialect the backend serves (chat completions, then Messages, then Responses).
• Layer 2: Pi(CliAgent) runs pi --mode json in a private home (PI_CODING_AGENT_DIR, HOME), offline.
  • The call's tools are an MCP server with exposure: direct; Pi's default would hide them behind its Code Mode.
  • Resume uses the session file. Usage and the trajectory are read from Pi's events (records.parse_pi, trajectory.pi_steps).
  • Roles, web search and container isolation are refused with Unsupported.
  • Failed sessions: Pi's JSON mode exits 0 however a session ended, so Pi.outcome() reports failed (main's mechanism since Claude Code subscriptions as a shared model backend for acting and learning (#70) #77: exit 0 without a result) for a session that did not settle, aborted, or whose last request failed, was aborted or was cut at its output limit. No change to the shared runner's interface.
• Layer 3:
  • The acting agent deploys with hosts/pi.py and passes --approve, without which Pi skips the workspace's .pi/ tools and skills.
  • AgentEvolver, the loader and the config accept pi. The new methods/pi/ Evolver copies no login (home: []).
• hermit deploy --host pi: the adapter's MCP server is now declared exposure: direct. This is a visible change for existing deploy users.
• Login: a model reference only. Pi's own logins (~/.pi/agent/auth.json) are left for later.
• Core change: hermit/isolate.py, one word: agent_home.mkdir(parents=True). The task sandbox could not create Pi's two-level user folder (.pi/agent), so every Pi acting call crashed. Under the sandbox checklist this needs core-team agreement (Please confirm here @haizhongzheng )
• Docs: agent-layers.md, model-backends.md, config-fields.md, task.md, evolver.md, methods/agent.md, custom-evolver.md, compatibility.md, installation.md, CHANGELOG.

After review

Four commits were added on review (details in the review comment):

• 2361862 merges main (Claude Code subscriptions as a shared model backend for acting and learning (#70) #77). Pi moves onto main's outcome() instead of its own exit_code hook, and takes its home from last_file's directory instead of a home keyword on command(). Pi refuses login and isolation: container.
• 47fa33c review fixes:
  • a bound model's cost now follows its price (an Anthropic-bound Pi recorded $0);
  • cut, aborted or unsettled sessions are failed;
  • the MCP servers' timeout is 1800 s / 120 s instead of Pi's 60 s;
  • a compaction's request usage is counted;
  • an inherited PI_CODING_AGENT_SESSION_DIR is emptied;
  • RRSI reads a nested Pi log;
  • docs fixes.
• 68b42b2 tool server fix (also affects Codex and Claude Code): in a task-sandboxed acting run, a deployed workspace's stdio tool server crashed at startup (session.adapter is None in a sandboxed Session), so adapter tools never loaded. It now reads session.manifest.
• 1f207fd image_input: image_input: true (in agent.pi or evolver.pi) declares a bound model that takes images (Pi's default for an unknown model is text only).

The table below is from before these commits.

Validation

Run on Linux with bubblewrap 0.9.0, Python 3.12 and Pi 1.5.0 (release binary, checked against SHA256SUMS). No real provider was used: a local mock chat-completions server stands in for the model.

Check	Result
python -m pytest --integration, pristine origin/main (6b258fb)	3 failed, 940 passed, 57 skipped
python -m pytest --integration, this branch (with 6b258fb merged)	3 failed, 952 passed, 57 skipped
New tests/core/test_pi_agent.py (11 tests, about 5 s)	All pass, including 2 integration tests that run the real pi, unsandboxed and in bubblewrap
Codex and Claude unchanged (scratch before/after script, 79 cases)	Byte-identical, apart from Pi's additions to CLI_HOMES, STREAMS and the unknown-agent message
hermit train + hermit eval, sandbox enforced, Pi acting and learning (docs' toy task)	Test split: untrained 0.0, trained 1.0

• Failures: the same 3 on both trees, in examples/clbench_database (golden parity), which already fail on main.
• The +12 passes: the new Pi tests, plus Pi added to test_an_installed_cli_starts_with_only_its_own_paths.
• Fixtures (tests/fixtures/pi/) are real Pi output; only two paths are changed, as their README says.
• Not verified: reaching a real provider through the sandbox's allowlist proxy. Pi honoring HTTPS_PROXY is confirmed from its source (an EnvHttpProxyAgent set up in main.ts), not from a run.

Review

• Tests and documentation cover the affected behavior: see Validation and the docs list.
• Commands, defaults, and public interfaces are consistent. New: agent.base: pi, evolver.base: pi, a pi: settings section, the provider setting. One visible change: hermit deploy --host pi now writes exposure: direct.
• Shared logs and examples contain no credentials or private data. The fixtures were checked; models.json holds the key's variable name, never its value.
• Documentation-only: N/A.
• Core changes: shared Layer 2 (Pi's outage wording added to UNAVAILABLE), isolate.py (mkdir(parents=True); Pi refuses login) and login.evolver_problems (the same for the pi Evolver).
• Failures reported accurately: a failed request, an abort, and refused roles, web search or container are covered by tests. A provider outage sets unavailable, so the acting agent retries.
• Real entry points: make("pi").run, the acting agent's run, hermit train and hermit eval. The stand-ins are only at the edges (the CLI, the model).
• Test checklist:
  • Tests are in tests/core/; the fixtures are registered in tests/selection.py (CORE) and tests/README.md.
  • The stand-ins are built from recorded Pi 1.5.0 output.
  • The tests use no network, no sign-in, and no installed CLI outside integration tests.
  • test_selection.py's BUILT_IN gains pi.
• Sandbox checklist, reuse: Pi runs through CliAgent inside the task and evolver sandboxes. All of its variables come from home_env(). Run records:
  rollout-1.json / learner-1.json (excerpt)

  rollout-1: role=rollout enforced=True network=isolated probe=True forwarded=[<model>]
     env: HA_ADAPTER_SANDBOX_ENFORCE, HA_RESULT_FD, HOME, LANG, MOCK_KEY, PATH, PI_CODING_AGENT_DIR, PYTHONPATH
  learner-1: role=learner enforced=True network=isolated probe=True forwarded=[<model>, <tool server>]
     env: HOME, LANG, MOCK_KEY, PATH, PI_CODING_AGENT_DIR, PI_OFFLINE, PI_TELEMETRY, PYTHONPATH
     program: <pi install>/pi   binds: /w/adapter, /w/material, /w/task-info, /w/history, /w/state, /w/scratch

• Sandbox checklist, core change: isolate.py changes. Confirmed by post-pr.
• Independent review (post-PR audit): one defect worth discussion.
  • Outage signals from pi are not fully recognized by UNAVAILABLE in cli.py. My suggestion is giving each CLI its own outage check inside its own subclass, and a new PR may fit this modification better and clearer.

[haizhongzheng]

Thanks for adding Pi. We reviewed the PR (two independent reviews per round, each finding checked against the code
and, for Pi's behaviour, against Pi 1.5.0's source) and pushed four commits to this branch. All four are in the PR now.

2361862: merge main (#77) into the branch

#77 (Claude subscription) reworked how CliAgent reports a session: each CLI now implements outcome(), and
callers treat failed (exit 0 without a result) as a failure. So the merge:

• Replaces the shared exit_code hook with Pi.outcome(). A failed Pi session now reads as exit code 0 with
  extra["failed"], not exit code 1 with cli_exit_code.
• Has Pi.command() take its home from last_file's directory, as Claude Code does. The shared command() signature
  stays as on main, without the home keyword.
• Makes Pi refuse login in the acting agent, the isolate.py check and the Evolver's sign-in check.
  isolation: container, which now runs Codex and Claude Code, stays refused for Pi.

47fa33c: review fixes

Each fix has a regression test that fails without it.

• Cost. For a bound model, Pi's own cost figure was kept. Pi prices a model with no cost in models.json at
  0, so a model bound to Anthropic recorded $0, and a price given in the config was ignored. Now the cost of a
  bound model is computed from its price (Pi.adjust_usage).
• Failed sessions. A session that did not settle, aborted, or whose reply was cut at its output limit
  (stopReason: length) was reported as done. It is now failed, matching Pi's text mode, which exits 1 for each
  of these.
• Tool timeout. Pi's MCP servers default to a 60 s per-request timeout, which cut off Trainer tools that run
  rollouts. Both servers now set timeout, matching Codex's tool_timeout_sec: 1800 s for the call's tools and
  120 s for tools deployed with hermit deploy --host pi.
• Compaction. The summary request's usage (compaction_end.result.usage) is now counted as a call.
• Resume. An inherited PI_CODING_AGENT_SESSION_DIR moved sessions out of the private home, so a resume
  silently started over. It is now emptied.
• RRSI. A nested agent-pi.jsonl was read with the Codex parser and gave 0 steps. It is now read by its host's
  reader.
• Docs. Four corrections: how the recorded cost is computed; evolver.base: pi alongside evolver.model (without
  it the config is refused); pi in config-fields.md; and the backend guide's "the CLI agents do not [speak chat
  completions]".

68b42b2: tool server in a sandboxed run (also affects Codex and Claude Code)

In a task-sandboxed acting run, the stdio tool server a deployed workspace starts crashed at startup:
mcp_server.py read session.adapter.manifest, but a sandboxed Session has adapter = None. As a result the
adapter's tools never loaded. This predates the PR and hit Codex and Claude Code as well, but it also broke this
PR's Pi acting path, so it is fixed here (session.manifest), with an end-to-end test that starts the server
sandboxed and calls a tool.

1f207fd: image_input

Pi treats a model it does not know as text-only, so a bound vision model never received images that tools returned.
image_input: true (in agent.pi or evolver.pi) declares the model's input: ["text", "image"]. The default
stays text-only, because a text-only model rejects images.

We also updated the PR description to match: it no longer describes the exit_code hook and the home keyword,
and it has a short "After review" section.

CI passes on 1f207fd, the head with all four commits.

Noted, no change in this PR

• Lost usage. A compaction that fails loses its usage, because Pi reports none for it.
• Same on main. These also happen with Codex and Claude, so they are not specific to this PR:
  • the acting agent's retry loop keeps only the last attempt's usage;
  • extra_body is not passed to the CLI.
• Rare cases. These need unusual inputs or setups:
  • a prompt starting with @;
  • system instructions longer than 120 KB in a sandbox;
  • session ids containing _ or .;
  • a workspace .pi/settings.json that sets sessionDir.

🤖 Generated with Claude Code