extract-Codex-prompt

Extract Codex Prompt

Procedure for recovering the complete Codex LLM request template from the binary or JS bundle.

When to Use

• Extracting system prompt after a Codex update
• Comparing prompt changes between versions
• Documenting ant-only vs external user differences
• Extracting prompt from a historical version (downloaded via npm)

Inputs

Codex Prompt Architecture

The system prompt is an array of strings assembled internally.

Before sending to the API, they are joined into 3 TextBlockParam objects:

1. system[0]: Attribution header (x-anthropic-billing-header: ...) — no cache
2. system[1]: Prefix ("You are Codex, Anthropic's official CLI for Codex.") — cache_control: ephemeral
3. system[2]: All remaining sections joined with \n\n — cache_control: ephemeral

Additionally, git status is appended as one more element before joining.

User context (AGENTS.md, date) is sent as messages[0], wrapped in <system-reminder>.

Section Order

Static (globally cacheable):

1. Intro — CYBER_RISK + URL warning
2. System — tool permissions, hooks, compression
3. Doing tasks — code style, security, help
4. Actions — reversibility, confirmation rules
5. Using tools — dedicated tools vs Bash, TodoWrite
6. Tone and style — emoji, conciseness, format
7. Output efficiency — brevity rules

Dynamic boundary marker: __SYSTEM_PROMPT_DYNAMIC_BOUNDARY__

Dynamic (per-session): 8. Session guidance — Agent, Skill, Explore 9. Memory — AGENTS.md contents 10. Environment — CWD, platform, model, cutoff 11. Language — optional, from settings.language 12. Output Style — optional, from outputStyleConfig 13. MCP Instructions — optional, from connected MCP servers 14. Scratchpad — optional, if enabled 15. Function Result Clearing — optional, if CACHED_MICROCOMPACT enabled 16. Summarize Tool Results — always present 17. Git status — appended last

Conditional Variants

Procedure

Phase 0: Locate or Download the Artifact

To find a version by date (e.g., "early January 2026"):

# Use the helper script to find versions by date range
scripts/cc-find-version.sh 2026-01-01 2026-01-10
# Or manually:
npm view @anthropic-ai/Codex time --json | python3 -c "
import json, sys
data = json.load(sys.stdin)
for ver, ts in sorted(data.items()):
    if '2026-01' in ts: print(f'{ver}: {ts}')
"

To download a specific version:

mkdir -p /tmp/Codex-<ver> && cd /tmp/Codex-<ver>
npm pack @anthropic-ai/Codex@<ver>
tar xzf anthropic-ai-Codex-*.tgz

To use the currently installed version:

which Codex                 # → ~/.local/bin/Codex (symlink)
ls -la $(which Codex)       # → follow to ~/.local/share/Codex/versions/<ver>
Codex --version             # → e.g. 2.1.104

Phase 0.5: Detect Artifact Type

file <path-to-artifact>

Historical note: versions before ~2.1.90 ship as JS bundles; later versions are Bun Mach-O binaries.

Phase 1A: Extract Strings from Binary (Mach-O only)

1. Extract all strings (~350K lines for a ~200MB binary):

   strings <binary-path> > /tmp/binary-strings.txt
   wc -l /tmp/binary-strings.txt
   

2. Find prompt anchors:

   grep -n "You are an interactive agent" /tmp/binary-strings.txt
   grep -n "Executing actions with care" /tmp/binary-strings.txt
   grep -n "# Doing tasks" /tmp/binary-strings.txt
   

Phase 1B: Read JS Bundle Directly (Node script only)

The JS bundle is a minified single-file Node.js script. The prompt is embedded as string literals.

wc -l <path>/cli.js                                    # typically ~5000 lines
grep -n "You are Codex" <path>/cli.js            # find identity prefix
grep -n "# Doing tasks" <path>/cli.js                  # find prompt sections

Skip Phase 2 (navigate binary strings) — proceed directly to Phase 3.

Phase 2: Navigate the Binary Strings (Mach-O only — skip for JS bundles)

Strings exist in two forms — choose the right one:

Prefer the minified JS form — it preserves the complete assembly logic including conditional branches. Use standalone constants only for cross-referencing.

To find the minified JS block, look for very long lines containing multiple function definitions:

grep -n "function.*Executing actions with care" /tmp/binary-strings.txt

The prompt functions typically cluster in one line of 5000+ characters. Check line sizes to confirm:

sed -n '<line_number>p' /tmp/binary-strings.txt | wc -c

Phase 3: Extract Metadata

Find the MACRO object containing version and build time:

grep -o 'VERSION:"[^"]*"' /tmp/binary-strings.txt | head -3
grep -o 'BUILD_TIME:"[^"]*"' /tmp/binary-strings.txt | head -3

This yields the header values: time: <BUILD_TIME>, version: <VERSION>.

Phase 4: Resolve Minified Variables

1. Find tool name assignments:

   grep -o 'var [A-Za-z0-9_]*="Bash"' /tmp/binary-strings.txt
   grep -o 'var [A-Za-z0-9_]*="Read"' /tmp/binary-strings.txt
   # repeat for Edit, Write, Glob, Grep, Agent, Skill, AskUserQuestion, TodoWrite, TaskCreate
   

2. Match function names by unique content inside each function body.
3. Find ant-only gate — search for the quiet_salted_ember string:

   grep "quiet_salted_ember" /tmp/binary-strings.txt | head -5
   

   The function that checks this value (e.g., wJH(H)) is the ant-detection gate — trace its usage to find all ant-only branches.

Phase 5: Extract and Assemble

1. Extract exact text of each section (both default and ant-only variants).
2. Assemble into the output format — see references/output-format.md.
3. Header: time: <build_time>\nversion: <version> only.
4. Show JSON skeleton of the API request, then the actual content of each system[N] block.
5. Prompt sections flow continuously (joined with \n\n), no artificial dividers.
6. Use {{PLACEHOLDER}} for runtime values, {{[ANT-ONLY] ...}} for ant variants, {{If condition:}} for optional sections.

Phase 6: Verify

We are analyzing the binary from outside — there is no live Codex session to compare against.

1. Internal consistency: all sections present and ordered, no gaps between anchors.
2. Tool name completeness: every minified variable used in prompt functions has a resolved mapping. Search for unresolved short vars (2-3 chars) in extracted text.
3. Version match: Codex --version (installed) vs MACRO object in binary — confirm they are the same binary.
4. Compare against previous template (mandatory if prior versions exist):

   scripts/cc-diff-templates.sh tmp/Codex-prompts/Codex-v<old>.txt tmp/Codex-prompts/Codex-v<new>.txt
   

   Review the diff for: added/removed sections, changed tool names, new conditional gates. Confirm nothing was accidentally dropped.
5. Section count: standalone constants region should contain the same anchor strings (# System, # Doing tasks, etc.) as the minified JS — cross-reference both forms (Mach-O only).

Checklist

• Artifact type determined (Bun binary vs JS bundle)
• Version confirmed via MACRO object
• All prompt sections extracted in order
• Dynamic boundary identified (if present in this version)
• Ant-only variants documented for each affected section (if present)
• Opus 4.6 anti_verbosity section captured — or noted as absent in this version
• All tool name variables resolved (no unresolved short vars in output)
• Metadata (version, build time) extracted from MACRO object
• Messages[0] prepended context format documented
• Git status appended to system prompt
• API parameters (model, max_tokens, thinking) documented
• Cross-referenced minified JS vs standalone constants for consistency (Mach-O only)
• Diff against previous template run and reviewed (if prior versions exist in tmp/Codex-prompts/)

Helper Scripts

All paths below are relative to the skill directory.