[smoroso]

What

Restart cold AgentApp processes after runtime dependency installation, with the app environment on the import path from Python startup. Preserve the already-claimed task input in a private file, restore it once after restart, and consume the chat prompt only afterward. For stdin-authenticated launches, hand the resolved token to the existing token-file CLI path using a private file. The restart does not put the token in argv or repeat the startup acknowledgement. A host-only supervisor now starts the app interpreter, forwards termination, and reports a failed task if incompatible app dependencies prevent startup. The restart handoff is authenticated and restricted to the configured runtime root and claimed run before cleanup ownership is accepted. Preloaded workers keep their existing path.

Why

New Chat can fail with cannot import name 'Converter' from 'attr'. The runner has already cached an older attr module when the app environment supplies a newer attrs package. Changing sys.path cannot replace those cached imports. A fresh interpreter avoids mixing the two versions without pinning the app's dependencies or unloading live modules.

How to manually test

With the framework development environment installed, run this exact block from the repository root:

set -eu
cd framework
export PYTHONPATH="$PWD/py"
export RAY_ENABLE_UV_RUN_RUNTIME_ENV=0
uv run --no-sync --python=3.11.14 python -m pytest --override-ini addopts= -q py/flwr/supercore/task_process/agent py/flwr/supercore/superexec/dependency_installer_test.py py/flwr/supercore/superexec/executor/subprocess_executor_test.py py/flwr/supercore/cli/flwr_agentapp_test.py py/flwr/common/args_test.py

Expected: all tests pass. The subprocess regression first reproduces a cached dependency's missing Converter import, then checks fresh imports after restart, restoration without a second task-input claim, private input-file permissions, and exactly-once finalization and cleanup. A separate test checks that restart happens before consuming the initial prompt. The stdin-authenticated CLI subprocess regression checks token recovery through a private file, no token in argv or captured output, exactly one startup acknowledgement, one-time input restoration, and cleanup. New regressions cover real HTTP failure reporting when an app shadows httpx, rejection of invalid restart paths and handoffs without deleting unrelated files, and forwarding of SIGINT, SIGTERM, and SIGQUIT where available. The signal test covers both PID- and group-directed delivery, with the child in a separate POSIX session so it can finalize without duplicate delivery.

Validation

• Synced with latest main. The exact manual block passed: 102 runtime, CLI, and token-parsing tests under Python 3.11.14.
• Type checking, Ruff, Pylint, Black, and isort passed for all three changed files, along with the copyright check.
• Re-ran the disposable Python 3.13 reproduction with real attrs/jsonschema packages. It reproduced the original import error, then passed imports, schema validation, task-input restoration, and cleanup after restart.
• The title is valid. Its failed CI attempt stopped during the external uv setup download; rerunning that job passed. CI is running on the updated head.
• A full New Chat conversation has not been tested against a rebuilt Labs executor. Labs must consume this Flower change and rebuild its executor before that check. Existing local services were not modified.

[chatgpt-codex-connector]

Codex Review Summary

This comment shows the latest Codex review activity on this pull request.

Review	Status	Commit	Review trigger
📝 Code Review	🔄 Running since 2026-10-28T18:14:49.167913Z	2a79921	New commits

ℹ️ About Codex in GitHub

Your team has set up Codex to review pull requests in this repo. Reviews are triggered when you

• Open a pull request for review
• Mark a draft as ready
• Comment "@codex review" or "@codex security review".

Codex reacts with 👀 while any review is running, comments if it has suggestions, and reacts with 👍 once all reviews finish with no findings.

[Copilot]

🟡 Changes recommended

Cold AgentApp restarts with --token-stdin fail because stdin has already been consumed and closed, causing the CLI to exit before restoring the claimed task or registering cleanup.

1 open issue

• Preserve stdin token across AgentApps CLI restart · New

What changed in this PR

This PR restarts cold AgentApps after runtime dependency installation so app dependencies load in a fresh interpreter, avoiding conflicts with cached modules. Preloaded workers retain their existing path.

Changes:

• Preserve claimed task input in a private file and restore it once after restart.
• Prepare dependencies and restart before consuming the initial chat prompt.
• Add regression tests for fresh imports, input restoration, cleanup, and prompt ordering.

The changes address one cohesive runtime issue; no PR split is needed.

File	Description
framework/​py/​flwr/​supercore/​task_process/​agent/​run_agentapp.py	Adds interpreter restart and task-input restoration before prompt consumption.
framework/​py/​flwr/​supercore/​task_process/​agent/​run_agentapp_test.py	Tests dependency isolation, private input handoff, cleanup, and restart ordering.

_{Review effort: Balanced}

[Copilot]

🟡 Changes recommended

The restart via os.execve discards the running log uploader and undrained queue, losing pending Runtime logs; the queue must be flushed before restarting without finalizing the claimed task.

1 open issue

• Flush the log queue before restarting the uploader · New

1 resolved since last review

• Preserve stdin token across AgentApps CLI restart

_{Review effort: Balanced}

[chatgpt-codex-connector]

💡 Codex Review

Here are some automated review suggestions for this pull request.

Reviewed commit: a71590a4b2

ℹ️ About Codex in GitHub

Your team has set up Codex to review pull requests in this repo. Reviews are triggered when you

• Open a pull request for review
• Mark a draft as ready
• Comment "@codex review".

If Codex has suggestions, it will comment; otherwise it will react with 👍.

Codex can also answer questions or update the PR. Try commenting "@codex address that feedback".

[chatgpt-codex-connector]

💡 Codex Review

Here are some automated review suggestions for this pull request.

Reviewed commit: 58ff633861

ℹ️ About Codex in GitHub

Your team has set up Codex to review pull requests in this repo. Reviews are triggered when you

• Open a pull request for review
• Mark a draft as ready
• Comment "@codex review".

If Codex has suggestions, it will comment; otherwise it will react with 👍.

Codex can also answer questions or update the PR. Try commenting "@codex address that feedback".

[Copilot]

🟡 Changes recommended

The child shares the supervisor’s POSIX process group, allowing duplicate signal delivery to terminate AgentApp before task finalization and runtime cleanup.

1 open issue

• Start child in separate session to prevent duplicate signal delivery · New

1 resolved since last review

• Flush the log queue before restarting the uploader

_{Review effort: Balanced}

[Copilot]

🔵 Needs a closer look

Human assessment is needed because a critical POSIX cancellation race can kill the supervisor while leaving AgentApp running without supervisor recovery.

No open issues 🎉

1 resolved since last review

• Start child in separate session to prevent duplicate signal delivery

_{Review effort: Balanced}