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# Environment & toolchain — guide (generic tier)

Reference notes, design rationale, and negative results (11).

#### 1. 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>

#### 2. 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>

#### 3. 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>

#### 4. 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>

#### 5. 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>

#### 6. 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>

#### 7. 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>

#### 8. 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>

#### 9. 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>

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

A slim Docker image can silently drop a transitive dependency and break a feature with no error: e.g. an NLP feature failed because `import spacy` pulls spacy.cli which needs click, but the slim image installed typer without click, so the model never loaded and the downstream behavior silently degraded; adding click fixed it. The failure was silent and only tracing/instrumentation surfaced it. When slimming an image, audit transitive deps and instrument the affected subsystem so a silent dependency failure becomes visible rather than a quiet behavior regression.
  <sub>sources: personal_labs/crewrift_lab/crewrift/crewborg/version_log.md</sub>

#### 11. 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>
