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# Environment & toolchain — guide

Reference notes, design rationale, and negative results (17) for environment & toolchain. Read when working in this area.

#### 1. A sandbox usually cannot run a live match - fall back to compile+unit tests and report what was NOT validated
`loop` · **negative result**

A sandboxed session typically cannot run a live local game: the policy's loopback WebSocket (ws to 127.0.0.1:2000) fails with PermissionError 'Operation not permitted', tsx/Node launchers hit `listen EPERM` on the IPC pipe (try TMPDIR=/private/tmp first - sometimes fixes it), and a GUI/TTY cogames play can hit a psutil permission error. When live validation is structurally blocked, run what you CAN - focused unit tests plus a static `nim check`/compile and call-site reasoning - clean up spawned processes, and explicitly report that gameplay was NOT live-validated rather than claiming it was; compile+unit signal is necessary but not sufficient. The harness auto-classifier also blocks out-of-scope commands (an `aws sts get-caller-identity` probe was denied), and routing review to external services fails (`auggie --print` ships private context, so the sandboxed run DNS-fails and the escalated retry is policy-rejected - do a local audit instead). When a check truly cannot run because deps/credentials are unavailable, say so explicitly in the handoff.
  <sub>sources: players_checkouts/players/users/james/personal_cogs/AGENTS.md, claude-code:27659fc3-8e40-469f-beda-31ddd5c6ceca, claude-code:aae25940-ade3-41bc-b817-517dc86ccebf, codex:019e00c0-d889-7d72-9781-3e90e7c1c7b9 (+14)</sub>

#### 2. Resolve bot assets/paths explicitly, not via cwd - and beware cwd on sys.path[0] shadowing installed packages
`generic` · **negative result**

Resolve a player/bot's asset, config, and resource paths explicitly (pass game-root/atlas/map/Paths through the bot) instead of cwd via getCurrentDir()/setCurrentDir(): cwd-relative resolution is fragile under a harness, as an FFI/ctypes library, or alongside other bots sharing a process. In the Among Them (BitWorld) Nim repo the server resolves clientDataDir() as getCurrentDir()/../clients/data, so launching from the repo root instead of among_them/ crashes with 'Missing palette asset: .../pallete.png'. The same cwd-on-path hazard bites Python: running `python -` (stdin) from a dir containing a `coworld/` subpackage puts cwd on sys.path[0] and shadows the installed coworld package (ModuleNotFoundError 'coworld.api_client') - run a script FILE instead or cd elsewhere. Replace per-script sys.path hacks with one shared setup_pythonpath() helper so imports resolve consistently across entry points.
  <sub>sources: bitworld/among_them/AGENTS.md, bitworld/among_them/players/mod_talks/DESIGN.md, bitworld/among_them/players/modulabot/DESIGN.md, claude-code:0a2634a1-19b7-402e-841e-084ce80c015f (+6)</sub>

#### 3. Player SDK is imported (pin via uv.lock) while the game ref is deliberately pinned to the deployed league version
`loop`

In the player lab the SDK is imported, not vendored: players.player_sdk comes from the public players repo (tracks main) with uv.lock pinning the exact commit for reproducible clones - adopt the latest with `uv lock --upgrade-package players`, not hand-edited SHAs. By contrast the game ref (CREWRIFT_REF) stays deliberately pinned so it matches the deployed league game, not latest. No GitHub creds or sibling checkouts are needed to build/run because the SDK and Crewrift game are public; verify with `uv sync`, `uv run softmax login && uv run softmax status` (expect Authenticated), and `uv run pytest`. Before pulling an upstream repo whose values you pin, diff the incoming commits to confirm they do not touch what you pinned, and only fast-forward a clean tree. Prefer not to bump a pin when avoidable - loosening to `>=` is acceptable. Flag heavy unused deps in docs as aspirational (alpha_cog pinned torch>=2.11.0 but scripted_alpha.py did not use it); a uv project with no [build-system] is a non-packaged 'virtual' project and a `uv init` main.py is leftover scaffolding.
  <sub>sources: player_labs/README.md, auggie:5d1ff8d5-2505-4dca-af45-56d3070363e2, auggie:e251085a-b35d-4171-8dbd-d006b8bc2bd9, claude-code:63658f66-83c7-482e-a805-d58527e10975 (+4)</sub>

#### 4. An env var's mere presence (or a dropped Bedrock thinking-signature) can silently break a player - bisect the environment
`generic` · **negative result** · ⚠ _session-derived, unverified_

The mere PRESENCE of an env var can silently change whether a player works: setting ANTHROPIC_API_KEY (even fake/empty) made the process hang/crash while unsetting it let identical code run cleanly. When a player behaves differently across machines/runs with identical code, diff the full environment and bisect by running once with the var set and once unset. Relatedly, OpenCode running Opus over Amazon Bedrock can fail with 'messages.1.content.0.thinking.signature: Field required' because extended-thinking blocks carry a cryptographic signature that must be passed back intact (or stripped entirely) on multi-turn requests and the client drops it; workaround is to disable extended thinking for that model or use a non-Bedrock provider for Opus.
  <sub>sources: opencode:ses_201637e3bffeRa6Y0x3DOs8hh1, opencode:ses_223c540d9ffe8nF6kcU1RXf0wp</sub>

#### 5. Keep packages decoupled from heavy deps: sibling-not-nested layout, no native-build/import at __init__ time
`generic` · **negative result**

Place a new parallel-experiment package as a SIBLING of an existing one, not nested: nesting a coborg package inside the scripted among_them package was abandoned because importing any submodule transitively ran the parent's __init__.py, which eagerly imported mettagrid (a heavy Bazel+Nim build), coupling the lightweight bot to an expensive dependency. Likewise do not auto-load or auto-build a native library at package import time - auto-loading in __init__.py triggered a redundant rebuild and a runpy double-import RuntimeWarning when the build ran via `python -m`; expose an explicit memoized load_library() the entrypoint calls so tests build only when needed. Before reaching for Cython/Rust/numba, reuse an established native-integration convention in the repo (a sibling bot already shipped Nim-via-ctypes with build infra, so Nim+ctypes was the low-friction choice) and verify the platform's actual primitives (system.Channel[T] existed but std/channels did not in that Nim version).
  <sub>sources: players_checkouts/players/archive/players/among_them/coborg/PLAN.md, claude-code:91060045-312c-4787-9819-a1421d228d61, claude-code:d59631cb-a50e-42e8-a102-56ffb0864b55, codex:019e06a0-5754-74e0-baf2-771853591aaa (+2)</sub>

#### 6. Do not gate commands on a grep expected to match nothing, or pipe to `grep -q` under pipefail
`generic` · **negative result**

A chain like `build && grep -i error build.log && python test.py` is a trap: when grep finds no matches (the success case) it exits non-zero and breaks the && chain, so the test never runs and you wrongly conclude there was no output. Under `set -o pipefail`, `grep -q` exits early on the first match and SIGPIPEs the upstream process, making the whole pipeline report failure even on a successful match. Instead capture output to a variable, then match it.
  <sub>sources: personal_labs/crewrift_lab/suspicion_lab/tools/nightly_refit.sh, claude-code:0e7b14ca-ffd5-4137-9456-47485d3c6f87, opencode:ses_204495c66ffe7u8C8SOiEX1zdH</sub>

#### 7. Recover a stuck nimby build by clearing ~/.nimby/nimbylock, and pin the exact Nim version the build helper expects
`generic` · **negative result**

The `uv run` mettagrid build flakes because it rebuilds mettagrid (Bazel C++ plus Nim mettascope) and the Nim step runs `nimby sync`; nimby does NOT release ~/.nimby/nimbylock on error, so a failed sync leaves the lock behind and the retry loop hits the same stuck lock as a no-op. Recover by removing ~/.nimby/nimbylock (only when no nimby process holds it), deleting any ~/.nimby/pkgs/<name> dir missing its .git so nimby re-clones, then running `nimby sync` directly to confirm before retrying. Beware version skew: direct `nim` test compiles can pass while a stricter shared-library build helper fails because the helper wants a pinned Nim (e.g. 2.2.4) and tries to download nimby (sandbox DNS blocks it) - pin and verify the exact toolchain the build helper expects, not whichever local Nim passes the direct tests.
  <sub>sources: players_checkouts/players/archive/players/among_them/coborg/PLAN.md, claude-code:ca5e32ea-3dad-42a9-8991-0f07d28b1060, codex:019e4c28-d516-7ca0-b145-153c152b4f43</sub>

#### 8. Codex model selection is gated by the auth account - validate allowed models before relying on cheap-model swaps
`generic` · **negative result** · ⚠ _session-derived, unverified_

Codex model selection is constrained by the auth account: under a ChatGPT account, requesting o4-mini/codex-mini fails with 'invalid_request_error: model not supported when using Codex with a ChatGPT account.' Plumb a model override flag through the pipeline but validate which models the actual auth path allows before relying on cheap-model swaps.
  <sub>sources: claude-code:db8f623e-c8c0-4195-b1d8-8a8d30fdc4a7</sub>

#### 9. Bridge to an optional legacy framework via env-gated sys.path injection, defaulting inert
`generic` · ⚠ _session-derived, unverified_

A legacy framework with no pyproject and a colliding import root was added to sys.path only when CYBORG_FRAMEWORK_PATH was set, reusing only its plain dataclasses (not its harness loop) and falling back to local equivalents otherwise - keeping the SDK installable in CI/Docker images that do not ship it. Use env-gated, default-inert sys.path injection to depend on an optional external framework without breaking clean installs.
  <sub>sources: claude-code:eb751ed4-c198-4b0d-819e-1a3002f4f341</sub>

#### 10. Nim per-entity structs must reference shared immutable data, not embed it by value - and re-examine your crash hypothesis
`generic` · **negative result** · ⚠ _session-derived, unverified_

Per-entity structs should hold references to shared immutable world data, never embed it by value: storing a large immutable NavGraph by value on each agent struct bloated the struct and caused Nim ORC/stack issues (hangs/crashes). Fix by loading the shared data once into a module-level ref or shared ReferenceData object, like sprites and fonts. Lesson for diagnosis: don't anchor on the first plausible crash explanation - the suspected 'ORC corruption from JSON parsing at module init' was a red herring; the real cause was the struct bloat, and once moving the data off the struct made the crash vanish the JSON suspicion was never real. Re-examine a suspected cause after the fix works.
  <sub>sources: opencode:ses_204495c66ffe7u8C8SOiEX1zdH</sub>

#### 11. MettaScope GUI replay is fragile - prefer headless inspection and `-r none`
`loop` · **negative result** · ⚠ _session-derived, unverified_

Treat MettaScope GUI replay as fragile and prefer headless log/metric inspection of saved replays. `cogames replay <path>` failed with a Nim 'cannot open file: opengl' error and stayed broken even after adding every ~/.nimby/pkgs/*/src to the Nim --path; the compiled binary also could not find its bundled data unless run from a directory containing the matching MettaScope data/ bundle (the metta repo root or a temp cwd seeded with that bundle). When `cogames play` crashes on startup with a MettaScope `pixie.nim ... Unsupported image file format` / SIGSEGV, the default `-r auto` renderer is launching the Nim GUI with a broken image asset - pass `-r none` to disable built-in rendering whenever your policy supplies its own display or you only need the game loop.
  <sub>sources: codex:019e19a7-8605-7992-9b28-cb4d2ca9132e, opencode:ses_1fa66f0b7ffeIF47rk2pDlz4RX</sub>

#### 12. Reproduce a performance regression against an unmodified baseline before blaming your diff - a venv rebuild can be the cause
`generic` · ⚠ _session-derived, unverified_

Before blaming your diff for a performance regression, reproduce against an unmodified baseline. A hang at 2000 steps was not caused by the code under test - the baseline policy hung too after a venv rebuild that made runs ~20x slower (2:51 vs ~8s per 2000-step run) with no lockfile change. Treat a fresh venv rebuild as a prime suspect when run times explode.
  <sub>sources: opencode:ses_1fbb083dfffeFNp623MAOdar2j</sub>

#### 13. Coworld player containers reach the game over the coworld-local bridge alias, not host.docker.internal
`loop` · ⚠ _session-derived, unverified_

In a local coworld run, player containers reach the game over a user-defined Docker bridge network named `coworld-local` at `ws://coworld-game-<runid>:8080/player?...` set via `--network-alias`, NOT via `host.docker.internal`. The `127.0.0.1:<port>:8080` publish only lets the host runner hit `/healthz` and spectator routes; Dockerfile comments recommending `host.docker.internal` are stale and only appear to work because the player reads the env var.
  <sub>sources: claude-code:67ff1fe3-48c0-4738-b7fb-8b994e567434</sub>

#### 14. Distinguish a player bug from a server bug, and verify you are running the artifact you think you are
`loop`

When a match crashes, distinguish a player/policy bug from a game-server bug: a freshly built server binary segfaulting mid-match while the previous binary ran clean with identical player code is a server-side regression - keep a known-good server binary to fall back to and file the crash against the game repo rather than chasing it in the policy. After a rebuild or a human's 'I pulled and rebuilt', verify you are running the artifact you think you are: a rebuild can land the new binary at a path different from the one launch scripts default to, leaving you testing a stale build - check mtime and git describe against the source tree, and point launch scripts at the in-tree build path. For the Among Them Nim project specifically, run sources via `nim r <file>.nim` rather than pre-built executables under ./out/ to always exercise current source.
  <sub>sources: bitworld/among_them/AGENTS.md, opencode:ses_21b273d4fffee0T9oMpvlktzkg</sub>

#### 15. A slim Docker image can silently drop a transitive dep (click) and break a feature without an error - tracing surfaces it
`loop` · **negative result**

A slim Docker image silently broke spaCy chat-NLP: `import spacy` pulls spacy.cli which needs click, but the slim image installed typer without click, so the model never loaded (meeting_decision.nlp=failed every episode) and the imposter bandwagon degraded to vote-only; adding click to the install fixed it (verified chat_nlp.state()=='ready'). The failure was silent - tracing is what surfaced it. Audit transitive deps when slimming an image and instrument the affected subsystem so a silent dependency failure is visible.
  <sub>sources: personal_labs/crewrift_lab/crewrift/crewborg/version_log.md</sub>

#### 16. Single-host internal Coworld deployment: EC2 lift-and-shift, root-equivalent socket runner, systemd+backups, constrained DB pool
`loop`

For an internal/trusted single-team deployment, prefer an EC2 lift-and-shift (one x86_64 host running the existing docker-compose stack behind Caddy for HTTPS) over Kubernetes: the Docker-socket episode runner works unchanged on a real Docker daemon, so there is no porting cost. But that runner builds/runs containers via the host Docker socket and is therefore root-equivalent on the box - fine for an internal trusted team but UNSAFE for untrusted multi-tenant policy code, which needs a pod-spawning Kubernetes runner (move to EKS only for autoscaling or untrusted code; each hosted player pod requests 2 CPU / 2Gi, which are scheduling requests not hard limits). Operationally: survive reboots with a systemd unit + Docker live-restore + restart:unless-stopped; back up state nightly (pg_dump of Postgres, tar of the Gitea volume holding canonical policy history) to S3 while artifacts/replays persist to R2/S3; an always-on m7i.2xlarge+gp3 runs ~$250-450/mo on-demand, so stop the instance off-hours (EBS persists) for bursty use. Constrain the DB connection pool for batch/build workloads - local Postgres connection exhaustion hit during build/static rendering, fixed by a lower default max, build-time pool max of 1, and connection+idle timeouts.
  <sub>sources: players_checkouts/players/docs/coworld-player-packaging.md, optimizers/docs/OPTIMIZER-MVP-SESSION-SUMMARY.md, optimizers/docs/deployment.md</sub>

#### 17. uv's 'VIRTUAL_ENV does not match' warning is harmless - uv uses the project venv regardless
`generic` · ⚠ _session-derived, unverified_

The uv warning 'VIRTUAL_ENV=.venv does not match the project environment path ... and will be ignored; use --active' is harmless: uv uses the project venv regardless. It arises when a relative-path .venv was activated from a different directory than the uv project root; use `uv run --active` to target the activated venv or unset the variable rather than treating it as a blocker.
  <sub>sources: opencode:ses_22085eca7ffeS682vQ9JkzWot0</sub>
