OpenAI Native Compaction for OpenCode

Use OpenAI's official Responses API compaction v2 in OpenCode.

OpenCode can compact long coding sessions. When you are using OpenAI Responses models, this plugin sends a normal /responses request whose final input item is compaction_trigger, instead of asking another model to write a text summary.

Why Native Compaction

Default prompt summary	OpenAI native compaction
Generates a plain text summary	Returns an encrypted compaction item
Can miss tool or reasoning state	Built for the Responses API state model
App-owned summary format	Official Responses compaction output
You decide what to keep	OpenAI returns the next compacted window

The important part is simple: compaction v2 returns an encrypted compaction item that should be passed to the next /responses request. This plugin makes OpenCode do that for OpenAI providers.

What It Does

1. Intercepts OpenCode session compaction for configured OpenAI providers.
2. Sends the current Responses input window to /responses with a final compaction_trigger item.
3. Removes OpenCode's internal summary prompt from the compact request body.
4. Stores the compacted output in a local SQLite checkpoint.
5. Injects that checkpoint into the next /responses request for the same session.
6. Replaces OpenCode's synthetic post-compaction exchange with the active checkpoint while preserving later real messages.

When To Use It

Use this if:

• You use OpenAI Responses API models in OpenCode.
• You run long coding sessions that hit compaction.
• You want OpenAI's official compaction item instead of a custom text summary.

Skip it if:

• You do not use OpenAI Responses API providers.
• You prefer OpenCode's default prompt-based summary.
• Your sessions are short enough that compaction does not matter.

Install

Add the npm package to your OpenCode config.

{
  "$schema": "https://opencode.ai/config.json",
  "plugin": ["opencode-openai-compact"]
}

For a local checkout during development, use a file URL.

{
  "$schema": "https://opencode.ai/config.json",
  "plugin": ["file:///path/to/opencode-openai-compact"]
}

Requirements:

Runtime	Version
Node.js	>=22.12.0
OpenCode	>=1.18.7 (Tested with 1.18.23)

Configuration Files

Most users do not need plugin-specific configuration.

Create openai-compact.json or openai-compact.jsonc only when you want to override defaults. Later layers override earlier layers. Within the same directory, openai-compact.jsonc is read after openai-compact.json and can override it.

Read order:

1. Built-in defaults.
2. Global OpenCode config directory: openai-compact.json, then openai-compact.jsonc.
3. Directory from OPENCODE_CONFIG_DIR: openai-compact.json, then openai-compact.jsonc.
4. Nearest project .opencode directory found by walking upward from the current directory: openai-compact.json, then openai-compact.jsonc.

Exception: state.retentionDays is read only from layer 2 because all projects share one global database. Values in layers 3 and 4 are ignored with a warning.

Global OpenCode config directory:

• $XDG_CONFIG_HOME/opencode, when XDG_CONFIG_HOME is set.
• ~/.config/opencode, when XDG_CONFIG_HOME is not set.

If neither openai-compact.json nor openai-compact.jsonc exists in the global OpenCode config directory, the plugin creates an empty openai-compact.jsonc file on first load.

State Database

Runtime checkpoints are stored in SQLite at:

~/.config/opencode/openai-compact/checkpoints.db

The database stores checkpoints and the message IDs of OpenCode's internal post-compaction control turns. Tracking IDs keeps those turns out of future requests even if OpenCode changes their text, metadata, or position.

When a forked OpenCode session first runs after compaction, checkpoints and control turns before the fork point are copied to the new session with their regenerated message IDs.

The default retention is 30 days. Retention is a global maintenance policy for this shared database, not a per-project setting. Set state.retentionDays only in the fixed global OpenCode config directory. Values from OPENCODE_CONFIG_DIR or project .opencode files are ignored with a warning so one project cannot prune another project's checkpoints.

Example Configuration

{
  "$schema": "https://raw.githubusercontent.com/partment/opencode-openai-compact/main/configSchema.json",
  "enabled": true,
  "providers": {
    "openai": {
      "enabled": true,
      "compactModel": null,
      "compactReasoningEffort": null
    }
  },
  "headers": {
    "compact": "x-opencode-openai-responses-compact",
    "session": "x-opencode-openai-responses-compact-session"
  },
  "responses": {
    "endpointPath": "/responses"
  },
  "compactBodyKeys": [
    "input",
    "instructions",
    "tools",
    "parallel_tool_calls",
    "reasoning",
    "service_tier",
    "prompt_cache_key",
    "text"
  ],
  "summary": "Context compacted.\nFollowing conversations will continue from this compacted checkpoint.",
  "state": {
    "retentionDays": 30,
    "deleteOnSessionDeleted": true
  }
}

Configuration Reference

Field	Type	Default	Description
enabled	boolean	true	Enables or disables the plugin.
providers	object	{ "openai": { "enabled": true, "compactModel": null, "compactReasoningEffort": null } }	Provider ids to wrap, keyed by OpenCode provider id. Each provider can be explicitly enabled or disabled.
headers	object	see below	Internal header names.
responses	object	see below	Responses endpoint path settings.
compactBodyKeys	string[]	see example	Request body keys copied into compact calls.
summary	string	see example	Synthetic assistant text emitted after compaction.
state	object	see below	SQLite retention and delete behavior.

headers

Field	Type	Default	Description
compact	string	"x-opencode-openai-responses-compact"	Internal header that marks a compaction request. Header names are normalized to lowercase and must be valid token names.
session	string	"x-opencode-openai-responses-compact-session"	Internal header that carries the OpenCode session id. It must differ from compact and cannot use reserved authentication, content, connection, or routing names.

providers

Field	Type	Default	Description
providers.<id>.enabled	boolean	true	Enables or disables compaction wrapping for this provider. Set providers.openai.enabled to false to leave the built-in OpenAI provider untouched.
providers.<id>.compactModel	string | null	null	Model sent to the /responses compaction v2 request. null follows the model used by the latest conversation part for both automatic and manual compaction.
providers.<id>.compactReasoningEffort	"none" | "minimal" | "low" | "medium" | "high" | "xhigh" | "max" | null	null	Reasoning effort sent to compaction. null follows the current conversation selection. Supported levels vary by model.

Priority: explicit setting > latest conversation part > OpenCode's original compaction request.

null uses the next available value in that order.

Provider settings are deep-merged across configuration layers. Adding a custom provider does not remove the default openai entry. To use only a custom provider:

{
  "providers": {
    "openai": { "enabled": false },
    "custom-openai": { "enabled": true }
  }
}

responses

Field	Type	Default	Description
endpointPath	string	"/responses"	Responses API path suffix to intercept. Whitespace-only values and / are rejected; values are trimmed, prefixed with /, and stripped of trailing slashes.
compactEndpointPath	string	"/responses/compact"	Deprecated and ignored. Retained only so existing configuration files continue to load.

state

Field	Type	Default	Description
retentionDays	integer	30	Global number of days to keep checkpoints in the shared database. Only the fixed global config directory may override it; non-global values are ignored with a warning.
deleteOnSessionDeleted	boolean	true	Deletes stored rows on session.deleted. When false, rows remain but are tombstoned and never used again.

Configuration diagnostics

Set OPENCODE_OPENAI_COMPACT_DEBUG=1 to print an effective-configuration summary at startup. The summary includes existing configuration files, fields overridden by each layer, enabled providers, endpoint and header settings, the shared database path, the global retention scope, ignored retention overrides, and deprecated fields. It does not print authentication tokens.

Unknown fields in nested objects are rejected instead of silently ignored. JSONC syntax errors include the source file, line, column, and parser error.

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Development

pnpm install
pnpm run typecheck
pnpm run test
pnpm run build