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Implementation Plan: Support baseUrl as a Model Setting Param

Issue Summary

Users should be able to provide an optional custom baseUrl during the /model setup flow. If no value is supplied, the SDK's default URL is used. A basic URL format validation must be applied to the input.

Current Architecture (relevant touch-points)

Layer File What it does
Config types internal/config/config.go ProviderConfig, GlobalConfig, ResolvedConfig, Resolve()
Config persistence internal/config/loader.go JSON read/write to ~/.keen/configs.json
LLM factory internal/llm/models.go ClientConfig, NewClient()
Anthropic client internal/llm/anthropic.go reads ANTHROPIC_BASE_URL from .env today
OpenAI Responses internal/llm/openai_responses.go NewOpenAIResponsesClient — no baseURL today
OpenAI-compat internal/llm/openai.go openAICompatibleBaseURL() hard-codes provider URLs
Genkit (Google) internal/llm/genkit.go NewGenkitClient — no baseURL today
Model selection UI internal/cli/repl/widgets/model_selection.go multi-step wizard: Provider → Model → Thinking → APIKey
REPL wiring internal/cli/repl/repl.go calls replwidgets.New(...) and onComplete callback

Implementation Plan

1. Config layer — store baseUrl per provider

File: internal/config/config.go

  • [ ] Add BaseURL string field to ProviderConfig (JSON tag "base_url,omitempty").
  • [ ] Add BaseURL string field to ResolvedConfig.
  • [ ] In Resolve(), propagate ProviderConfig.BaseURL into ResolvedConfig.BaseURL (no session-level override needed for now — it is always persisted globally).

2. LLM layer — thread BaseURL through ClientConfig and all clients

File: internal/llm/models.go

  • [ ] Add BaseURL string to ClientConfig.
  • [ ] Pass cfg.BaseURL when constructing each ClientConfig inside NewClient().

File: internal/llm/anthropic.go

  • [ ] Remove the .env-based ANTHROPIC_BASE_URL lookup.
  • [ ] Read cfg.BaseURL from ClientConfig; apply option.WithBaseURL only when non-empty.

File: internal/llm/openai_responses.go

  • [ ] Accept cfg.BaseURL in NewOpenAIResponsesClient; apply option.WithBaseURL only when non-empty.

File: internal/llm/openai.go

  • [ ] Accept cfg.BaseURL in NewOpenAICompatibleClient.
  • [ ] When cfg.BaseURL is non-empty, use it instead of the value returned by openAICompatibleBaseURL().
  • [ ] Keep openAICompatibleBaseURL() as the fallback for providers that have a well-known default URL.

File: internal/llm/genkit.go

  • [ ] Accept cfg.BaseURL in NewGenkitClient.
  • [ ] Pass it through to the compat_oai.OpenAICompatible / googlegenai.GoogleAI plugin config when non-empty (check each plugin's struct for a BaseURL field).

3. UI layer — add StepBaseURL to the model selection wizard

File: internal/cli/repl/widgets/model_selection.go

  • [ ] Add StepBaseURL Step constant (insert after StepProvider, before StepModel — or after StepAPIKey, before completion — whichever feels most natural in UX; proposed order: Provider → Model → Thinking → BaseURL → APIKey).
  • [ ] Add fields to Model:
  • BaseURLInput string
  • BaseURLError string
  • [ ] Update handleKeyMsg for StepBaseURL:
  • backspace / printable text → edit BaseURLInput.
  • enter → validate; if valid (or empty) advance to StepAPIKey; else set BaseURLError.
  • esc → emit modelSelectionCancelMsg.
  • [ ] Add handlePasteMsg support for StepBaseURL (same pattern as StepAPIKey).
  • [ ] Add URL validation helper isValidBaseURL(s string) bool:
  • Accept empty string (optional field).
  • Use net/url.Parse + check scheme is http or https and Host is non-empty.
  • [ ] Add renderBaseURLInput() view method (mirroring renderAPIKeyInput style, but no masking — base URLs are not secrets).
  • Show existing saved value as a hint: (press Enter to keep: <url>).
  • Show BaseURLError in red when non-empty.
  • [ ] Update ViewString() to handle StepBaseURL.
  • [ ] Update complete() to:
  • Read BaseURLInput; fall back to existing ProviderConfig.BaseURL when empty.
  • Store in ProviderConfig.BaseURL and m.resolvedCfg.BaseURL.
  • [ ] Update New(...) / onComplete signature: the callback currently receives (provider, model, apiKey string) — extend to also pass baseURL string, or simply rely on resolvedCfg which is already mutated in place before onComplete is called. The latter requires no signature change.

File: internal/cli/repl/repl.go

  • [ ] No signature change needed if resolvedCfg mutation approach is used.
  • [ ] Verify updateLLMClient() re-reads m.ctx.cfg (which is resolvedCfg) — it already does via llm.NewClient(m.ctx.cfg).
  • [ ] Optionally show baseUrl in buildInitialScreen info block when non-empty.

4. Validation helper (shared or inline)

  • [ ] Implement isValidBaseURL in model_selection.go (keeping it local; no need for a separate package given it is UI-only validation).
  • [ ] Rules:
  • Empty → valid (field is optional).
  • Must parse without error via url.Parse.
  • Scheme must be "http" or "https".
  • Host must be non-empty.

5. Tests

File: internal/config/config_test.go

  • [ ] Add test: Resolve propagates ProviderConfig.BaseURL into ResolvedConfig.
  • [ ] Add test: Resolve leaves ResolvedConfig.BaseURL empty when ProviderConfig has no BaseURL.

File: internal/llm/anthropic_test.go

  • [ ] Add test: NewAnthropicClient uses custom BaseURL when provided.
  • [ ] Add test: NewAnthropicClient does not set base URL when cfg.BaseURL is empty.

File: internal/llm/openai_responses_test.go / internal/llm/openai_test.go

  • [ ] Same coverage pattern as Anthropic tests above.

File: (new or existing widget test)

  • [ ] Add test for isValidBaseURL:
  • "" → valid.
  • "https://api.example.com" → valid.
  • "http://localhost:8080" → valid.
  • "ftp://bad.com" → invalid.
  • "not-a-url" → invalid.
  • "https://" (missing host) → invalid.
  • [ ] Add test: StepBaseURL advances to StepAPIKey on Enter with valid URL.
  • [ ] Add test: StepBaseURL stays on step and sets error on Enter with invalid URL.
  • [ ] Add test: complete() persists BaseURLInput into ProviderConfig.BaseURL.

6. Housekeeping

  • [ ] Run go test ./... — all tests pass.
  • [ ] Run go mod tidy.
  • [ ] Update CHANGELOG.md [Unreleased] section with the new feature entry.

File Change Summary

File Change type
internal/config/config.go Edit — add BaseURL to ProviderConfig and ResolvedConfig; update Resolve()
internal/config/config_test.go Edit — new tests
internal/llm/models.go Edit — add BaseURL to ClientConfig; pass through in NewClient()
internal/llm/anthropic.go Edit — remove .env lookup; use cfg.BaseURL
internal/llm/anthropic_test.go Edit — new tests
internal/llm/openai_responses.go Edit — use cfg.BaseURL
internal/llm/openai_responses_test.go Edit — new tests
internal/llm/openai.go Edit — use cfg.BaseURL with fallback
internal/llm/openai_test.go Edit — new tests
internal/llm/genkit.go Edit — use cfg.BaseURL where plugin supports it
internal/cli/repl/widgets/model_selection.go Edit — new StepBaseURL, validation, render
internal/cli/repl/repl.go Edit (minor) — optionally display baseURL in initial screen
CHANGELOG.md Edit — add unreleased entry