Getting it into your agent
One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.
npx agentmods add skills/vivekascoder/codex-prewalk/prewalknpx skills add vivekascoder/codex-prewalk --skill prewalkgit clone --depth 1 https://github.com/vivekascoder/codex-prewalkWhat it costs to keep this loaded
Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5 | $0.00033 | $0.00534 |
| Opus 5 | $0.00016 | $0.00267 |
| Sonnet 5 | $0.00007 | $0.00107 |
| Haiku 4.5 | $0.00003 | $0.00053 |
Grade A, and why
prewalk scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 2d ago.
A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.
Nothing flagged
None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.
How it starts
The opening of the file, as written. The whole thing — 48 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Prewalk
Run the bundled Prewalk orchestrator for $ARGUMENTS.
Resolve this skill directory to its real path first (the user install may be a symlink under ~/.agents/skills/prewalk). From the resolved skill directory, the repository root is two directories up and the orchestrator is:
node "<repo-root>/scripts/prewalk.mjs" --cwd "$PWD" "$ARGUMENTS"
Behavior
The orchestrator:
- Starts a fresh Codex app-server thread on the planner model.
- Supplies the Prewalk planning nudge as turn-scoped developer instructions.
- Requires the planner to inspect the repository, establish a compact plan/todo list, and begin implementation.
- Watches
turn/plan/updatedand successfulfileChangeevents. - If the planner finishes a turn before the first edit lands, continues the planner on the same thread with an implementation nudge (up to the configured continuation limit).
- Once a plan exists and the first successful file edit lands, interrupts the planner turn.
- Starts an empty-input continuation turn on the same thread with the executor model.
- Lets the executor finish implementation and validation from the inherited trajectory.
If the planner never reaches the plan + successful-edit boundary within the continuation limit, the orchestrator exits non-zero instead of treating the run as successful.
Defaults
- planner:
gpt-5.6-sol - executor:
gpt-5.6-luna - planner effort:
high - executor effort:
medium - planner continuations:
3
Environment overrides: CODEX_PREWALK_PLANNER, CODEX_PREWALK_EXECUTOR, CODEX_PREWALK_PLANNER_EFFORT, CODEX_PREWALK_EXECUTOR_EFFORT, and CODEX_PREWALK_PLANNER_CONTINUATIONS.
Constraints
- Do not replace this with ordinary Plan mode; Prewalk must preserve the same Codex thread trajectory and the planner's first edit.
- Do not continue the task yourself in the parent turn after the nested run succeeds.
- The nested Codex thread uses the
workspace-writesandbox withapprovalPolicy: never. - If Codex app-server is unavailable or the orchestrator exits non-zero, report the error clearly instead of silently re-running the task outside Prewalk.
What this file has done since we first saw it
Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.
- 2d ago First seen · 48 lines · 33 tokens per session scan A b403bf96bbaf
prewalk is a skill published in the GitHub repository vivekascoder/codex-prewalk (1 stars, last pushed 8d ago), licensed Apache-2.0. It adds 33 tokens to every session and 534 once invoked, about $0.0002 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.
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