fix: infer LLM provider from present key; stop mislabeling unhealthy backend as stopped containers

[akozak-gd]

Problem

An Anthropic-only .env (ANTHROPIC_API_KEY set, no provider chosen) silently defaulted to the OpenRouter provider:

1. DEFAULT_PROVIDER defaulted to openrouter (config.py) with no derivation from which key is present.
2. Startup validation requires the active provider's key → OPENROUTER_API_KEY reported missing → StartupValidationError.
3. app_lifecycle deliberately doesn't crash on that error — it marks healthy=False, so /health/ready returns 503 forever while the containers stay up.
4. The TUI startup gate saw containers running but backend not ready, and reused the "The SpecFlow containers aren't running." screen — a misleading message, since the containers were fine.

Provider inference already existed in specflow-init.sh (it wrote DEFAULT_PROVIDER=anthropic to .env for the Anthropic-only case), but that only runs at init time — a key set manually or after init bypasses it, and it duplicates the decision the backend also makes.

Fix

Make the provider derived from the key present, in exactly one place (the backend), and remove the DEFAULT_PROVIDER knob so there's nothing to drift.

• config — DEFAULT_PROVIDER is resolved from whichever key is set: OpenRouter when its key is present (also the documented default when both are set), Anthropic when only that key is set, else OpenRouter (which then fails startup fast). It is no longer a configurable knob, so a provider/key mismatch is impossible by construction.
• startup_validation — with no provider key set at all, the check fails fast naming both keys.
• init script / docker-compose / .env.quickstart.example / QUICKSTART — drop DEFAULT_PROVIDER entirely (including the now-redundant inference block in specflow-init.sh) so provider resolution lives only in the backend.
• TUI — distinguish "containers down" from "containers up but backend unhealthy." The latter shows an accurate prompt and re-polls readiness without re-running docker compose up.

Design note / trade-off

You can no longer force Anthropic when both keys are set (both → OpenRouter). This matches the documented "set ONE of the two keys" UX; the escape hatch is to set only the key you want. If a hard override is ever needed, it should be reintroduced as a single explicit knob rather than alongside the key-based derivation.

Not included

--build on docker compose up (raised in review) is intentionally left out — it's a separate, larger change (also needs repo change-detection, not just up/down) and is orthogonal to this bug.

Verification

• make unit-tests — full backend + mcp_server suites pass. Added coverage for provider resolution and both TUI message paths; rewrote tests that were coupled to the removed knob (test_enums.py "env-overridable" → "env value ignored"; startup tests now control the provider via keys).
• make check-complexity-diff METRIC=cc — average complexity unchanged (3.66).
• End-to-end: with only ANTHROPIC_API_KEY in .env, curl -sf http://127.0.0.1:8000/health/ready returns 200 and the TUI proceeds past the gate.

[mkonopelski-gd]

I think we could add here flag: --build so on default we always build the image so users do not need to do themselves when they pull our repo. On the other hand we do not verify if there was change to repo just if docker is down or has no containers. So it might actually be part of bigger change for future.

[mkonopelski-gd]

Actually why we need this Flag? I think it is misleading. The docs say use one Key or another. So we should verify if one of them is set, if neither Fail Fast error. If one of them choose the one set. IF both, use open router as default. I would generally remove it starting from .env.example and docker-compose as for me it has no real value. @awrobel-gd ?

[mkonopelski-gd]

do not think that if we remove the entire Step this commentary is necessary.

[mkonopelski-gd]

@akozak-gd this is recommended way to do it this kind of setting Attribute based on other attributes:

from functools import cached_property
from pydantic import BaseSettings, computed_field

class Settings(BaseSettings):
    ANTHROPIC_API_KEY: Optional[str] = None
    OPENROUTER_API_KEY: Optional[str] = None

    @computed_field
    @cached_property
    def DEFAULT_PROVIDER(self) -> LLMProvider:
        if self.OPENROUTER_API_KEY:
            return LLMProvider.OPENROUTER
        if self.ANTHROPIC_API_KEY:
            return LLMProvider.ANTHROPIC
        return LLMProvider.OPENROUTER

[awrobel-gd]

unless explicitly validated with Pydantic (dont remember if we have it) - dont do if .. as this is the same as if bool(...)

Lets try:

def is_key_valid(raw_key):
    if str(raw_key).strip():
        return raw_key
     else:
        return false