pi-openai-codex-compat

OpenAI Codex compatibility for Pi, combining priority fast mode, native Codex compaction, and Codex-optimized model features in one Pi package.

Features

• Request-level fast mode: keeps the canonical openai-codex provider id and models selected while adding service_tier: "priority" at the request boundary.
• Native compaction: uses Codex remote_compaction_v2 for /compact, Pi threshold compaction, context-overflow recovery, and an optional percentage threshold.
• Codex apply_patch: provides an optional patch tool with the Codex grammar, parser, fuzzy matcher, overwrite semantics, filesystem behavior, model-facing result format, structured history, and diff-oriented TUI rendering. Pi sends it as an OpenAI custom grammar tool when the model supports that protocol and as a normal function tool otherwise.
• Standalone image generation: exposes Pi's dotted image_gen.imagegen tool as a native Responses namespace and executes generation or edits through the Codex Images endpoints.
• Standalone web search: exposes Pi's dotted web.run tool as a native Responses namespace and executes search and browsing through Codex alpha/search.
• Dedicated Codex tool UI: renders apply_patch, image_gen.imagegen, and web.run on a shared configurable surface with compact summaries and Ctrl+O expansion.
• Hosted web-search fallback: injects native web_search only when web.run is inactive, with cached, indexed, or live modes.
• Native request controls: configures Responses API text verbosity, reasoning summaries, and GPT-5.6 standard/pro reasoning mode.
• Session-local settings pane: /codex-settings changes every compatibility setting for the current session; Enter persists and closes, Escape discards unsaved changes and closes, and Ctrl+S persists without closing.
• Compact footer indicators: non-default Codex request modes are appended to the model side of Pi's normal second footer line.

Pi provides the Codex OAuth flow and model catalog. At session start, this package overrides the built-in openai-codex runtime under the same provider id so ordinary responses and remote compaction share one transport, parser, native-history store, and sticky WebSocket session.

Requirements

• Node.js 22.19 or newer
• Pi >=0.83.0 <0.84.0
• An OpenAI Codex login in Pi

Authenticate through Pi if needed:

/login openai-codex

Compatibility baseline and differences

The compatibility baseline is official Codex CLI 0.146.0, released July 29, 2026. Upstream main at commit bb5054fe47abe73ecbbd454751066a28c89f4bb9 was also inspected on August 3, 2026. This section is the package's explicit compatibility contract: it distinguishes close protocol adaptations from deliberate Pi behavior, configurable defaults, known gaps, and unsupported Codex runtimes.

Configurable defaults that differ from Codex

Area	This package by default	Official Codex	Configuration
Generated-image detail sent back to the model	Sends image tool-result content with input_image.detail: "auto". On GPT-5.6, auto uses original-size image accounting.	Uses high.	imageDetail: auto, low, high, or original.
Image-generation tool	Enabled whenever an openai-codex model is selected. Backend capability and account failures surface when the tool executes.	Stable and enabled by default, but additionally gated by plan, model, provider, authentication, image-generation, and namespace capabilities.	imageGeneration: boolean.
Standalone web.run	Disabled by default; when enabled, preferred over hosted web_search and sent with the complete reserved schema and description.	Enabled by default for gpt-5.6-sol through Responses Lite; otherwise subject to standalone-search feature and runtime gates.	webRun: boolean.
Hosted web search	Disabled by default; when enabled, injected only while web.run is inactive.	Omitted for gpt-5.6-sol while standalone web.run is available; otherwise defaults to cached mode when hosted search is supported.	webRun and webSearch: disabled, cached, indexed, or live.
Coding mutation tools	Enables apply_patch and suppresses Pi's active edit and write tools.	Chooses its tool surface from model metadata and runtime capabilities; there are no Pi edit or write tools to suppress.	applyPatch: boolean.
Codex tool background	Uses a subtle theme-derived surface for extension-owned Codex tools.	Uses Codex's own TUI activity cells rather than Pi tool rows.	toolBackground: subtle, status, or none.
Auto-compaction trigger	Relies on Pi's reserve-token threshold unless a percentage is configured.	Tracks Codex's model/token-budget state before and between sampling steps.	autoCompactAtPercent: percentage or unset. Pi's own compaction settings remain separate.
Fast mode	Uses the normal tier.	Uses the configured Codex service tier.	fastMode: boolean; true requests the priority tier.
Text and reasoning request controls	Explicitly sends low text verbosity, automatic reasoning summaries, and standard GPT-5.6 reasoning mode.	Resolves these controls through Codex configuration, model metadata, and turn state.	textVerbosity, reasoningSummary, and reasoningMode.

web.run is a reserved GPT-5.6 tool name. Its declaration therefore reproduces the complete current Codex post-normalization SearchCommands schema and official tool description instead of using Pi's normal compact tool schema. This intentionally omits generated annotations such as format and minimum that Codex removes before sending the declaration to Responses.

Non-configurable implementation differences

Area	Difference
Session storage	Pi remains the canonical session owner. Opaque Codex compaction checkpoints are stored in Pi compaction entries, and otherwise lossy Responses output is stored in sparse custom native-response entries. Official Codex owns a rollout/thread store directly.
Branching	Checkpoints and native response overrides follow Pi's active session branch. Official Codex uses its own thread, turn, rollback, fork, and context-window lineage.
Model switching	This package rejects model switches while the active Pi branch contains a native Codex checkpoint because the checkpoint is model-specific.
System instructions	Pi rebuilds the current system prompt and sends it through Responses instructions; normal Pi history does not store it as replayed system/developer input. /reload therefore updates the next request without rewriting old checkpoints.
Turn metadata	Requests do not yet send Codex's complete thread, turn, context-window, request-kind, workspace, and per-turn routing metadata. Sticky WebSocket continuation is implemented locally from response IDs and replayable items.
Mid-turn compaction	Provider-boundary percentage compaction installs a checkpoint and continues the intercepted request. Pi threshold compaction runs after the agent response and does not automatically continue unless Pi has queued messages. Official Codex compacts inline and continues when a completed sampling step says more model/tool work is required.
Incomplete responses	A Responses status: "incomplete" currently becomes Pi stopReason: "length". Official Codex treats response.incomplete as a stream error. This can produce a Pi threshold compaction followed by an idle agent instead of an inline continuation or explicit error.
Compaction lifecycle events	Percentage compaction writes through Pi's mutable session manager but cannot emit Pi's internal session_compact event through the public extension API. Manual, threshold, and overflow compactions initiated by Pi do emit the normal lifecycle.
Header hooks	An internal percentage-compaction request reuses the already transformed provider headers. It cannot independently rerun Pi's before_provider_headers hook.
Native retained context	The v2 retained-message selection and truncation match Codex. In normal Pi operation, system instructions are carried separately through instructions, so retained API history usually contains user messages rather than Codex's complete initial-context lifecycle.
Tool namespaces	Pi registers dotted names such as web.run as exact flat identifiers. The provider converts only the fixed extension-owned allowlist into real Responses namespace/member identities and rejects unknown or ambiguously flat namespaced calls.
Capability gating	Tool activation is based on the selected openai-codex provider plus package settings. It does not reproduce every official model-metadata, plan, feature-stage, executor, mode, or account gate.
Sandbox and approvals	Pi extensions run with full process permissions. apply_patch, local image reads, generated-image writes, and sibling Codex endpoints do not use Codex's sandbox, permission-profile, or approval lifecycle.
Image tool instructions	The package retains the server-reserved image-generation schema while replacing Rust-specific path annotations and Codex Code Mode instructions with model-facing descriptions, a prompt snippet, and system-prompt guidelines. Image-count bounds and selector exclusivity are enforced before execution.
Image artifact hint	When image saving succeeds, this package always returns the path hint, says “the generated image,” and has no 1,024-byte cutoff. Official Codex says “a generated image” and omits the hint when it exceeds 1,024 UTF-8 bytes.
Image artifacts	Generated files use Pi's agent directory and the Pi session/tool-call IDs. Official Codex uses its own artifact/output-directory lifecycle.
Web references	web.run structured results are retained branch-locally in Pi tool-result details rather than Codex extension events, and hosted native items are preserved for provider replay. Reference IDs are resolved remotely by alpha/search, as in Codex. Hosted citation annotations remain a separate unimplemented path.
UI	Pi renders its own conversation, footer, settings pane, branches, and compaction lifecycle. Extension-owned Codex tools have dedicated Pi renderers, but do not reproduce Codex app-server WebSearchItem or image-generation lifecycle notifications.

Tool and runtime coverage

The package implements the Codex-specific pieces that fit a provider compatibility extension:

• native Responses transport and history;
• remote compaction v2;
• apply_patch;
• hosted web_search;
• web.run;
• image_gen.imagegen;
• namespaced tool serialization;
• text verbosity, reasoning summaries/mode, and priority service tier.

The following official Codex facilities are not exact equivalents in this package:

Official Codex facility	Pi/package behavior
exec_command and write_stdin persistent PTY sessions	Pi bash is a one-shot command tool; no persistent PTY/session protocol is implemented.
Legacy shell_command	Pi uses bash; the Codex schema and execution/approval envelope are not reproduced.
view_image	Pi read already accepts images; no canonical view_image alias is registered.
update_plan, request_user_input, permissions, and environment tools	Not implemented by this package.
Context-window and clock tools	Not implemented. Compaction remains host/provider managed rather than model managed.
MCP resources and dynamic MCP tools	Pi does not provide this package with Codex's MCP runtime.
Plugin/connector installation	Not implemented; package installation remains an explicit Pi/user operation.
Searchable tool_search catalog	Pi can replay additive tool-search history for capable models, but this package does not implement Codex's searchable deferred-tool catalog and ranking runtime.
Multi-agent V1/V2 coordination	Out of scope; no Codex agent tree, mailbox, task-path, or fork-depth runtime is implemented.
JavaScript Code Mode and yielded cells	Out of scope; no V8 isolate, nested tool namespace, cell storage, or wait lifecycle is implemented.
Goals, memories, and remote skill-resource tools	Not implemented; Pi's sessions, files, and native skills remain separate systems.
Remote/deferred execution environments	Not implemented.

See OFFICIAL_CODEX_CLI_TOOL_CATALOG.md for the complete researched Codex tool inventory, and CUSTOM_CODEX_PROVIDER_WEB_REFERENCES.md for the unimplemented citation/reference design.

Install

From npm after a release is published:

pi install npm:pi-openai-codex-compat

From a local checkout:

pi install .

For a temporary development run:

pi --no-extensions -e .

Fast mode

Keep using an openai-codex model and enable Fast mode in /codex-settings. The extension adds service_tier: "priority" to ordinary and native-compaction requests without introducing another provider id or changing the selected model.

Fast mode applies to whichever built-in openai-codex model is selected. Priority-tier costs are reflected in Pi's usage totals, including when Codex echoes service_tier: "default" in its response.

Configuration

Create a global configuration file at:

~/.pi/agent/openai-codex-compat.json

A trusted project can override it at:

<project>/.pi/openai-codex-compat.json

Each session inherits the effective file-backed settings. Open /codex-settings to make immediate session-local changes. Press Enter to persist and close, Escape to discard unsaved changes and close, or Ctrl+S to persist without closing. The global file is the normal save target, while an existing trusted project override remains the target for that project. After Ctrl+S, later unsaved changes can still be discarded back to the values from that save.

The effective settings are printed once when a TUI session starts. The footer shows fast and pro only when enabled, and shows text verbosity or reasoning summary only when they differ from their defaults.

Example:

{
  "fastMode": true,
  "toolBackground": "subtle",
  "applyPatch": true,
  "imageGeneration": true,
  "imageDetail": "auto",
  "webRun": false,
  "autoCompactAtPercent": 90,
  "webSearch": "disabled",
  "textVerbosity": "low",
  "reasoningSummary": "auto",
  "reasoningMode": "standard"
}

Defaults:

Setting	Values	Default	Behavior
fastMode	boolean	false	Adds service_tier: "priority" to requests while retaining the current openai-codex provider and model.
toolBackground	subtle, status, none	subtle	Controls the shared self-rendered background for apply_patch, image_gen.imagegen, and web.run. status uses Pi's pending/success/error backgrounds; none keeps the custom layout transparent.
applyPatch	boolean	true	On selected openai-codex models, uses the extension's apply_patch tool instead of Pi's active edit and write tools. Other providers always use their normal Pi tool set.
imageGeneration	boolean	true	Enables the extension-owned image_gen.imagegen tool on selected openai-codex models.
imageDetail	auto, low, high, original	auto	Sets input_image.detail when an image tool result is sent back to the model. It does not change gpt-image-2 generation quality.
webRun	boolean	false	Enables the extension-owned web.run tool on selected openai-codex models. When active, it replaces hosted web_search in the Responses tool list.
autoCompactAtPercent	number greater than 0 and at most 100, or null	unset	Adds provider-boundary compaction independently of Pi's normal reserve-token threshold. A project value of null disables a global percentage threshold.
webSearch	disabled, cached, indexed, live	disabled	Controls hosted search and standalone-search external access. disabled removes hosted search but leaves an independently enabled web.run in cached-only mode; indexed prefers indexed content; live permits live external access.
textVerbosity	low, medium, high	low	Sets Responses API text.verbosity.
reasoningSummary	auto, concise, detailed, off	auto	Sets reasoning.summary when reasoning is enabled; off omits the summary parameter.
reasoningMode	standard, pro	standard	Sets reasoning.mode on GPT-5.6 models independently of Pi's reasoning-effort control.

Invalid JSON setting values are ignored and invalid JSON does not prevent Pi from starting. The settings pane never writes on ordinary changes, refuses to overwrite invalid JSON when Enter or Ctrl+S attempts to save, and retains unknown keys when saving. Project configuration is read only when the project is trusted.

Every setting can also be overridden for one Pi process with an environment variable:

Setting	Environment variable
fastMode	PI_OPENAI_CODEX_COMPAT_FAST_MODE
toolBackground	PI_OPENAI_CODEX_COMPAT_TOOL_BACKGROUND
applyPatch	PI_OPENAI_CODEX_COMPAT_APPLY_PATCH
imageGeneration	PI_OPENAI_CODEX_COMPAT_IMAGE_GENERATION
imageDetail	PI_OPENAI_CODEX_COMPAT_IMAGE_DETAIL
webRun	PI_OPENAI_CODEX_COMPAT_WEB_RUN
autoCompactAtPercent	PI_OPENAI_CODEX_COMPAT_AUTO_COMPACT_AT_PERCENT
webSearch	PI_OPENAI_CODEX_COMPAT_WEB_SEARCH_MODE
textVerbosity	PI_OPENAI_CODEX_COMPAT_TEXT_VERBOSITY
reasoningSummary	PI_OPENAI_CODEX_COMPAT_REASONING_SUMMARY
reasoningMode	PI_OPENAI_CODEX_COMPAT_REASONING_MODE

Environment variables have the highest precedence: defaults < global JSON < trusted-project JSON < environment. Boolean values accept true/false, 1/0, on/off, or enabled/disabled. Other settings use the values in the defaults table; PI_OPENAI_CODEX_COMPAT_AUTO_COMPACT_AT_PERCENT=off and PI_OPENAI_CODEX_COMPAT_AUTO_COMPACT_AT_PERCENT=default explicitly select Pi's default compaction lifecycle.

Environment-controlled rows are marked (env) and locked in /codex-settings. Saving the pane does not copy their effective values into JSON, so CLI overrides remain transient. Invalid environment values fail fast with the variable name and accepted values.

For example:

PI_OPENAI_CODEX_COMPAT_WEB_RUN=off \
PI_OPENAI_CODEX_COMPAT_IMAGE_DETAIL=high \
PI_OPENAI_CODEX_COMPAT_AUTO_COMPACT_AT_PERCENT=90 \
pi

Native compaction

The extension handles native compaction for openai-codex. It follows the Codex v2 flow:

1. Send normal Responses history followed by { "type": "compaction_trigger" }.
2. Validate the returned opaque compaction item.
3. Retain approximately 64,000 tokens of recent user, developer, and system context.
4. Persist the opaque checkpoint in the Pi session and replay it on later requests.

Ordinary responses and compaction use the same extension-managed SSE/WebSocket transport. The provider stores a native response override only when Pi's canonical assistant representation cannot round-trip the provider output exactly; normal text, reasoning, and tool responses therefore do not duplicate session data. Native overrides are associated with canonical assistants by response id and replayed only when they are present on the active Pi branch.

Any model switch is rejected while the active branch contains a native Codex checkpoint because checkpoints are model-specific. Navigate to a branch before the checkpoint or start a new session before switching. Toggling fast mode does not change the model id or invalidate the checkpoint.

Native compaction fails closed for Codex models: a failed compaction is cancelled instead of silently replacing the opaque state with a local text summary. Other providers continue to use Pi's default compaction behavior. /tree branch summarization is intentionally not intercepted.

When the active branch has no native Codex checkpoint, Pi model switching remains available. Selecting a provider other than openai-codex disables apply_patch, image_gen.imagegen, and web.run, and restores the Pi edit and write tools that apply_patch suppressed. Switching back to an openai-codex model reapplies the current session settings.

apply_patch

The package registers an apply_patch tool using the Codex patch format:

*** Begin Patch
*** Update File: src/example.ts
@@
-old value
+new value
*** End Patch

While applyPatch is enabled and an openai-codex model is selected, the extension temporarily disables Pi's active edit and write tools. Turning the setting off or selecting another provider restores only the tools that were active before apply_patch replaced them.

Supported operations:

• add files;
• update files with ordered context chunks;
• delete files;
• move an updated file;
• anchor updates at the end of a file.

Compatibility behavior:

• *** Add File overwrites an existing file, matching Codex.
• *** Move to overwrites an existing destination, matching Codex.
• Hunk matching retries exact text, trailing-whitespace-insensitive text, fully trimmed text, and Codex's Unicode punctuation normalization.
• The parser accepts Codex's lenient marker whitespace, blank update-context lines, and direct heredoc wrappers.
• Successful model-facing results use Codex's exit-code, wall-time, and Success. Updated the following files: format.
• Tool-result history stores per-file old/new content, display diffs, move destinations, overwrite information, and committed-prefix details after runtime failures.
• The TUI renders Codex-style Added, Edited, and Deleted diff blocks instead of the raw model-facing result.
• The collapsed view shows aggregate and per-file counts; Ctrl+O reveals complete hunks.

Filesystem behavior:

• Relative paths resolve from Pi's current working directory; absolute paths and .. traversal are honored.
• .git paths and symlinks follow normal host filesystem semantics.
• The extension does not add path filtering, sandboxing, or approval prompts.
• Every hunk is parsed and validated before filesystem writes begin.
• Mutations participate in Pi's per-file mutation queue and apply_patch calls execute sequentially.

A low-level I/O failure can still leave a multi-file patch partially applied. The failed tool result records the known committed prefix, but inspect the working tree before retrying when that record is marked inexact.

image_gen.imagegen

The package registers the dotted Pi tool name image_gen.imagegen and serializes it as a native Responses API namespace:

{
  "type": "namespace",
  "name": "image_gen",
  "tools": [{ "type": "function", "name": "imagegen" }]
}

The tool generates new images with gpt-image-2 or edits up to five local/recent conversation images. Local edit inputs must use absolute paths and are read directly with the Pi process's filesystem permissions. PNG, JPEG, GIF, and WebP edit inputs are accepted. Generated PNGs are returned to Pi as image tool content and stored without overwriting existing files under:

~/.pi/agent/generated_images/<session-id>/<call-id>.png

The active Pi agent directory replaces ~/.pi/agent when configured differently. Turning imageGeneration off removes the tool immediately for the current session; Enter or Ctrl+S in /codex-settings persists the value.

The tool registers the server-reserved schema directly with a model-facing absolute-path annotation that names the supported image formats. OpenAI rejects additional schema keywords for image-count bounds and selector exclusivity, so the executor enforces those constraints before filesystem or network access. Local paths are lexically normalized before reading. A one-line system-prompt snippet and four high-signal guidelines cover normal model use. Local images are inspected with Pi's read tool, and generated image content is displayed and saved automatically without Codex Code Mode wrappers.

Pi also persists the returned image content in tool-result history so later image edits and provider replay remain self-contained. Generated-image turns therefore increase the session file by approximately the base64 image size in addition to the saved PNG artifact.

When the image tool result is serialized back to the model, imageDetail controls its Responses input_image.detail. The default remains auto; select high for the official Codex default. The saved-path hint intentionally differs from Codex: it always uses “the generated image” and is not removed when the UTF-8 hint exceeds 1,024 bytes.

The TUI shows a compact generation/edit summary and saved artifact path instead of the model-facing path hint. Ctrl+O reveals the full prompt and artifact metadata; terminal image display continues to use Pi's normal image support.

web.run

The package registers the dotted Pi tool name web.run and serializes it as a native Responses API web namespace. Calls are executed through codex/alpha/search. Like Codex, successful model-facing output is the unmodified plaintext output wrapped in a single input_text content item:

{
  "type": "function_call_output",
  "call_id": "<call-id>",
  "output": [{ "type": "input_text", "text": "<alpha/search output>" }]
}

Structured results are not sent to the model by either implementation. Codex stores them in extension-backed web-search events; this package stores the equivalent opaque JSON branch-locally in Pi tool-result details. Extensions and session readers can inspect those details, while subsequent web.run calls resolve model-visible reference IDs through alpha/search rather than querying the details directly.

The collapsed TUI view provides action-specific summaries for search, image search, page navigation, in-page find, PDF screenshots, finance, weather, sports, and time. Ctrl+O expands structured source or image cards, page metadata with line/page gutters, PDF page cards, operation-specific result cards, and readable labeled fields for forward-compatible result types. Citation markers and backend separators are normalized for display, while empty or unavailable operations use compact warning states instead of appearing successful.

Standalone screenshot calls return a plaintext PDF-page reference from alpha/search, not image bytes or an image content item. The TUI therefore labels these results as reference-only, and the next model request receives the same plaintext reference rather than screenshot pixels.

The exposed command schema includes:

• search_query;
• image_query;
• open;
• click;
• find;
• screenshot;
• finance;
• weather;
• sports;
• time;
• response_length.

The tool sends the current user message plus the preceding visible user/assistant turn as search context. When web.run is active, hosted web_search is omitted; turning webRun off restores the hosted tool according to webSearch.

Both namespace tools are accepted only from the fixed extension-owned allowlist. Unknown namespaced calls and flat wire calls named web.run or image_gen.imagegen fail instead of being routed ambiguously.

Development

mise trust
mise install
npm install
npm run check
npm test

Run the credentialed Codex transport tests separately. They use the real WebSocket service and ask the model to report all prior history markers after each canonical and native continuation:

mise run test:live:codex

The task obtains the local Codex bearer token and runs the tests with gpt-5.6-luna at medium reasoning effort.

The focused Pi AI serializer copy lives under extensions/openai-codex-compat/vendor/pi-ai/. The custom Codex provider transport and stream parser are focused adaptations of Pi AI's corresponding implementation. Equivalence and protocol tests cover canonical serialization, native namespace round-trips, raw native replay, sibling Codex JSON endpoints, SSE request behavior, WebSocket reuse, grammar tools, image results, standalone search, and compaction continuation.

Release staging

The GitHub Actions workflow stages npm releases when a v* tag is pushed. The tag must match the package.json version, point at a commit whose subject is release: v<version>, and be a lightweight tag. Create it with git tag v<version>; do not use git tag -a, git tag -s, git tag -m, or cog bump --annotated.

Acknowledgements

The remote-compaction implementation follows the current OpenAI Codex remote_compaction_v2 protocol. The apply_patch, standalone image-generation, and standalone web-search behavior is adapted from OpenAI Codex under Apache-2.0. The Codex provider transport, stream processing, and OpenAI Responses history serialization adapt selected Pi AI methods under MIT; see third-party notices.

License

MIT © 2026 Kaan Ozdokmeci. See LICENSE.