Design and implement CodeMode runtime + OpenCode MCP adapter

[opencode-agent]

Summary

Track the agreed CodeMode direction from the Kit + Aiden design grill.

Source Discord thread: https://discord.com/channels/1391832426048651334/1521953032408141944
Related PR context: #34677

Locked decisions

• Split the generic CodeMode runtime into its own package, following the current experiments package structure/export style.
• Use CodeMode/tool naming: CodeMode, Tool, ToolError, UnknownTool, $codemode.
• Keep OpenCode-specific MCP integration in OpenCode, not in the generic runtime.
• MCP/user tools are adapted into ordinary CodeMode Tool.make(...) definitions.
• CodeMode owns generic $codemode.search over the final tool tree.
• Search only; no separate describe.
• $codemode.search({ query?, path?, limit? }) returns an array of full entries: path, description, signature, input, output.
• Default search limit is about 10; exact path lookup returns the matching tool entry.
• Search result signatures use native payloads: Promise<Issue>, not Promise<Result<Issue>>.
• Tools without output schema render output as unknown.
• Tool metadata should support Effect Schema and JSON Schema now, with room for Standard Schema later.
• Effect schema validation is first-class in v1; JSON Schema / Standard Schema can initially be render-only unless an adapter validates.
• Tool implementations are Effect-based for v1; promise normalization can come later for plugin ergonomics.
• Existing core OpenCode tools stay outside CodeMode for v1; focus CodeMode on MCP/user/deferred tools.
• Permissions stay in OpenCode adapters/tools. CodeMode runtime stays permission-dumb.
• Namespace collisions are not over-engineered: the final tool tree can use normal override behavior for now.
• Tool-call progress uses simple hooks, e.g. onToolCallStart / onToolCallEnd; no CurrentToolCall context for v1.
• Public limit knobs should be simple: timeoutMs, maxToolCalls, maxOutputBytes; derive internal guardrails.
• Keep the hand-rolled interpreter; do not embed QuickJS/V8 for v1.
• Add pure JS built-ins: Date, RegExp, Map, Set, and more Promise helpers.
• Keep ambient authority out: no fs, child processes, network/fetch, process/env, or timers for v1.
• Port forgiving JS semantics: missing property reads return undefined, typeof undeclared works, null/undefined object spread is a no-op, builtin callbacks like filter(Boolean) work, and NaN/Infinity can exist inside the sandbox while boundary handling stays safe.
• Support console.* capture and append logs to the model-facing result; prompt should still prefer return for intended output.
• Do not include output.text/file/image in OpenCode v1.
• Attachments/files/images emitted by child tools are host-collected outside CodeMode, never base64-inlined into the program value.
• Tool calls return their native structured payload to CodeMode; emitted attachments are accumulated by the outer OpenCode layer and returned as normal tool-result attachments with existing size/count handling.
• Error reporting should use clear categories: parse errors, unsupported syntax, invalid tool input, unknown tool, tool failure, invalid tool output, execution failure, timeout, and operation limits. Messages should be specific when safe and avoid leaking host internals/secrets.

Suggested implementation order

1. Create the standalone CodeMode runtime package from the experiments structure.
2. Port the locked interpreter/runtime changes.
3. Implement generic $codemode.search with the simple array/full-entry shape.
4. Add the OpenCode MCP adapter that produces Tool.make(...) definitions.
5. Wire host-side attachment accumulation.
6. Wire the OpenCode execute tool and simple progress hooks.
7. Leave existing core OpenCode tools outside CodeMode for v1.

[opencode-agent]

Tracker update from V2 TODO LIST audit (2026-07-02):

This is now the canonical CodeMode tracker for Aiden’s V2 CodeMode work.

Related PR context:

• feat: experimental codemode #34677 — experimental codemode

Ownership/status from V2 TODO LIST thread: @rekram1-node is tracking CodeMode alongside form service, MCP elicitation, and MCP prompts/resources. Keep future CodeMode PRs linked here.

[opencode-agent]

Tracker update from V2 TODO LIST (2026-07-02):

@rekram1-node reports CodeMode is nearly there. Remaining work is polish/tweaks from the Kit + Aiden design discussion, with an expected experimental-flag release soon.

Keep linking implementation PRs here; #34677 remains the earlier experimental codemode PR context.

[opencode-agent]

Tracker update from V2 TODO LIST (2026-07-02): @rekram1-node reports CodeMode is nearly there. Remaining work is polish/tweaks from the Kit + Aiden design discussion, with an expected experimental-flag release soon. Keep linking implementation PRs here; #34677 remains earlier experimental codemode PR context.

[opencode-agent]

Aiden's latest CodeMode status from Discord: https://discord.com/channels/1391832426048651334/1520962938733723720/1522663655353880607

• About to expose the experimental version in v1.
• Next: wire it into v2.
• Adding an OpenAPI spec adapter for the codemode package.
• Update v2 TUI by copying the v1 UI.

Related open PRs that appear to correspond:

• feat(opencode): gate execute tool behind code mode flag #35185 - v1 experimental CodeMode gate
• feat(codemode): add OpenAPI tool adapter #35192 - OpenAPI tool adapter

[opencode-agent]

CodeMode closeout: the original large implementation was reverted and landed as the following split PRs.

dev

• feat(codemode): add confined execution package #35079 — standalone confined-execution package
• refactor(opencode): expose MCP tools in native shape from the service #35103 — expose MCP tools in native shape
• feat(opencode): add code-mode MCP adapter #35085 — OpenCode MCP adapter
• refactor(opencode): fail the execute tool on program failure #35180 — surface execute program failures through normal tool errors/TUI rendering
• feat(opencode): gate execute tool behind code mode flag #35185 — feature flag plus registry/session wiring
• feat(codemode): add OpenAPI tool adapter #35192 — OpenAPI tool adapter

v2

• feat(codemode): add confined execution package #35118 — confined-execution package
• fix(codemode): require exact tool paths in guidance #35224 — exact tool-path guidance
• feat(core): expose deferred tools through execute #35361 — expose deferred Core/MCP tools through execute
• feat(codemode): add OpenAPI tool adapter #35362 — OpenAPI tool adapter

All of these PRs are merged. Keeping this issue closed as completed.