[delete-cloud]

Summary

Add the ability to switch model/provider/base_url at runtime on an existing session without losing conversation context. Previously only the REPL could change the model (and only via /model name). Now all three entrypoints support runtime config switching, and changing provider (e.g. codex ↔ deepseek) is also supported.

Changes

Core (RuntimeReplacementService)

• replace_runtime_config() now accepts optional provider_name and base_url alongside model_name
• Transactional: new config persisted atomically with rollback to old binding on failure

HTTP API

• PATCH /sessions/{session_id}/runtime-config — accepts {model, provider, base_url} in any combination
• Returns 409 on active turn, 400 if no fields provided

ACP Protocol

• AcpMode dataclass for config-driven provider/model presets
• session/set_mode now matches arbitrary modeId and calls replace internally
• CLI: --acp-mode (repeatable) and --acp-modes-json options
• Modes exposed in both initialize and session/new responses

REPL

• /model [provider:]name — e.g. /model deepseek:deepseek-chat
• Backward compatible: /model gpt-4o still works

Verification

• 118 relevant tests pass (3 replacement service tests updated for new protocol fields)
• Pre-existing 15 cli_pipeline failures unrelated

Usage

// HTTP: switch provider+model
PATCH /sessions/{id}/runtime-config
{"provider": "deepseek", "model": "deepseek-chat"}

// ACP: define modes and switch via session/set_mode
--acp-mode "pro:ChatGPT Pro:codex:gpt-5.5" --acp-mode "ds:DeepSeek:deepseek:deepseek-chat"

// REPL
/model deepseek:deepseek-chat
/model gpt-4o

Co-Authored-By: Claude Fable 5 noreply@anthropic.com

Summary by CodeRabbit

• New Features

  • Added CLI support for defining multiple ACP mode presets via --acp-mode and --acp-modes-json options.
  • Added HTTP endpoint to update session runtime configuration (provider, model, base URL).

• Enhancements

  • Model command now supports provider:model syntax for specifying both provider and model.
  • REPL sessions can now update provider alongside model during runtime.

[coderabbitai]

Caution

Review failed

The pull request is closed.

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro Plus

Run ID: 9109aee5-d12b-43f2-88f0-746f2b150bd8

📥 Commits

Reviewing files that changed from the base of the PR and between 4d8cafe and 0568935.

📒 Files selected for processing (11)

• coding-agent/src/coding_agent/acp/__init__.py
• coding-agent/src/coding_agent/acp/server.py
• coding-agent/src/coding_agent/cli/acp_command.py
• coding-agent/src/coding_agent/cli/commands.py
• coding-agent/src/coding_agent/cli/local_runtime.py
• coding-agent/src/coding_agent/cli/repl.py
• coding-agent/src/coding_agent/runs/replacement.py
• coding-agent/src/coding_agent/server/http_server.py
• coding-agent/src/coding_agent/server/schemas.py
• coding-agent/src/coding_agent/server/session_manager.py
• coding-agent/tests/coding_agent/test_runtime_replacement_service.py

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📝 Walkthrough

Walkthrough

This PR extends the coding agent to support configurable ACP "modes" (provider/model presets) and adds the ability to update session runtime configuration (model, provider, base URL) through CLI commands, REPL interactions, and HTTP endpoints.

Changes

ACP Modes Configuration and Runtime Updates

Layer / File(s)	Summary
ACP Mode Data Model coding-agent/src/coding_agent/acp/server.py, coding-agent/src/coding_agent/acp/__init__.py	Introduces AcpMode dataclass with id, name, description, provider, model, and base_url fields; adds default_acp_modes() helper; exports the type from the acp package.
ACP Server Mode Storage and Initialization coding-agent/src/coding_agent/acp/server.py	AcpServer.__init__ accepts optional modes parameter and stores it with fallback to defaults; AcpSessionManager protocol is extended with replace_session_runtime_config method; _session_mode_state generates response payloads from configured modes.
ACP Mode Switching and Response Updates coding-agent/src/coding_agent/acp/server.py	_session_set_mode now validates modeId, looks up the selected mode from the configured list, invokes replace_session_runtime_config with mode fields, and maps runtime/value failures to JSON-RPC errors; initialize, session/new, and session/resume responses include computed modes state.
Runtime Replacement Protocol Extension coding-agent/src/coding_agent/runs/replacement.py	RuntimeReplacementSession protocol declares optional provider_name and base_url fields; RuntimeReplacementBuilder.__call__ and RuntimeReplacementService.replace_runtime_config accept these new optional parameters, snapshot prior values, and restore them on rollback failure.
Session Manager Runtime Config Method coding-agent/src/coding_agent/server/session_manager.py	SessionManager.replace_session_runtime_config accepts optional model_name, provider_name, and base_url; resolves model_name from the admitted session when unset; forwards all parameters to the runtime replacement service.
Local CLI Session Manager Binding coding-agent/src/coding_agent/cli/local_runtime.py	LocalCliSessionManager protocol and ServerBackedLocalCliSessionManager implementation extended to accept and forward optional provider_name and base_url parameters alongside model_name.
CLI Mode Configuration Parser and Options coding-agent/src/coding_agent/cli/acp_command.py	Introduces _parse_acp_mode() to parse id:name[:provider[:model[:base_url]]] strings into AcpMode objects; adds repeatable --acp-mode and alternative --acp-modes-json Click options; implements mode selection logic and passes computed modes list to AcpServer.
REPL Session Provider and Model Updates coding-agent/src/coding_agent/cli/repl.py	_change_model_for_next_turn extended to accept optional provider_name parameter; expands allowed provider set on session restore; syncs context with current provider when switching sessions; implements coordinated model/provider updates and rollback in runtime replacement path.
CLI /model Command Provider:Model Syntax coding-agent/src/coding_agent/cli/commands.py	/model command now parses optional provider:model input; updates context["provider_override"] when provider prefix is present; modifies on_model_change hook signature to accept both model name and optional provider; adjusts success and current-model display messages.
HTTP Server Runtime Config Update Endpoint coding-agent/src/coding_agent/server/schemas.py, coding-agent/src/coding_agent/server/http_server.py	Adds RuntimeConfigUpdateRequest and RuntimeConfigUpdateResponse Pydantic schemas with strict validation; implements PATCH /sessions/{session_id}/runtime-config endpoint that validates at least one field is provided, checks session state, delegates to replace_session_runtime_config, and maps errors to appropriate HTTP responses.
Runtime Replacement Service Test Updates coding-agent/tests/coding_agent/test_runtime_replacement_service.py	Updates FakeSession fixture to track provider_name and base_url; extends build_runtime test helper signatures to accept these new parameters; adds assertions for value replacement and rollback; verifies provider_name and base_url restoration on persistent failure.

🎯 3 (Moderate) | ⏱️ ~25 minutes

🐰 Modes bloom in gardens new, with providers sweet and base URLs true,
The REPL hops through provider paths, while HTTP endpoints handle the math.
Runtime configs now dance and sway, replaced by dawn of brand new day! 🌅

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch feat/runtime-config-switching

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