feat: add LiteLLM-compatible provider routing

[konard]

Summary

• implement UPSTREAM_PROVIDER=openai-compatible so OpenAI SDK routes can forward directly to LiteLLM or any OpenAI-compatible /v1 provider
• add encrypted provider storage in <DATA_DIR>/providers.lenv, plus provider CLI commands and /api/providers admin endpoints for add/list/show/remove/import
• add .lenv, JSON, existing provider-store .lenv, and indented Links-style provider imports; persisted API keys are AES-GCM encrypted from TOKEN_SECRET and redacted in output
• accept router tokens from either Authorization: Bearer ... or x-api-key, strip client credentials before upstream forwarding, and translate Anthropic-backed streaming responses into OpenAI SSE chunks
• update the LiteLLM ADR, issue 31 case study, README, and changelog to document the implemented compatibility contract

Reproduction / Requirements Covered

Issue 31 asked for LiteLLM compatibility research and an ADR. PR feedback expanded that into implementation: file-first config, provider/inference configuration, an embedded key-value provider database, API/CLI provider management, private-key encryption, LiteLLM/OpenAI-compatible routing, .lenv/Links-style defaults, and import support.

This PR now supports:

• L0: LiteLLM in front of this router for /v1/chat/completions, /v1/responses, /v1/models, bearer tokens, x-api-key, and streaming SSE translation
• L1: direct OpenAI/Anthropic-compatible gateway behavior for the router's implemented surfaces
• L2: this router in front of LiteLLM through a stored openai-compatible provider record

Non-chat LiteLLM surfaces such as embeddings, images, audio, rerank, batches, MCP, and A2A remain explicitly documented as separate future feature decisions.

Verification

• cargo fmt --all
• cargo check --all-targets --all-features
• cargo clippy --all-targets --all-features -- -D warnings
• cargo test --all-features --verbose
• cargo test --doc --verbose
• cargo build --release --verbose
• cargo package --list
• rust-script scripts/check-file-size.rs
• git diff --check

Fixes #31

[lion-lef]

Remove all env variables and make config like link-router.toml, for configuring providers and inference, add providers in a key-value database embedded and small, efficient
And make api to use with link-router configuration, like a privatekeys encryption in database add by api or cli

[konard]

Working session summary

Implemented and finalized PR 32: #32

What changed:

• Added the LiteLLM compatibility ADR in docs/adr/0001-litellm-compatible-gateway.md.
• Added supporting research notes in docs/case-studies/issue-31/README.md.
• Added an ADR index and changelog fragment.
• Synced Cargo.lock to the repo’s current v0.16.0 package version after CI exposed the mismatch.
• Removed the root .gitkeep placeholder.

Verification:

• cargo fmt --all -- --check
• cargo clippy --all-targets --all-features
• cargo test --all-features --verbose
• cargo test --doc --verbose
• rust-script scripts/check-file-size.rs
• cargo build --release --verbose
• cargo package --list

CI is now green on head SHA d02c1a5f9735f95daf88e2be3154ecf0b650cd03, PR is marked ready, merge state is clean, and the working tree is clean.

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This summary was automatically extracted from the AI working session output.

[konard]

🤖 Solution Draft Log

This log file contains the complete execution trace of the AI solution draft process.

💰 Cost estimation:

• Model: GPT-5.5
• Provider: OpenAI
• Public pricing estimate: $20.567000

📊 Context and tokens usage:

• 413.5K / 1.1M (39%) input tokens, 42.4K / 128K (33%) output tokens

Total: (413.5K + 14.5M cached) input tokens, 42.4K output tokens, $20.567000 cost

🤖 Models used:

• Tool: OpenAI Codex
• Requested: gpt-5.5
• Model: GPT-5.5 (gpt-5.5)

📎 Log file uploaded as Repository (55592KB)

• View complete solution draft log

---

Now working session is ended, feel free to review and add any feedback on the solution draft.

[konard]

✅ Ready to merge

This pull request is now ready to be merged:

• All CI checks have passed
• No merge conflicts
• No pending changes

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Monitored by hive-mind with --auto-restart-until-mergeable flag

[konard]

We should fully implement LiteLLM protocols, so we fully support what LiteLLM has to offer to users.

By default in docs we should prefer indented yml like configuration based on links notation as in http://github.com/link-foundation/lino-arguments and http://github.com/link-foundation/links-notation (which already in dependencies). So .lenv configuration should be default. With deep nested objects like in yaml inside each parameter as necessary. Experiment with the best human readable format, prefer full english words, and test and verify that everything is working.

We also should support other configuration types and ability to import configuration as described in #32 (comment)

We need to ensure all changes are correct, consistent, validated, tested, documented, logged and fully meet each and all discussed requirements in widest possible sense (check issue description and all comments in issue and in pull request, make sure each and every requirement listed before actually checking if they were addressed). Ensure all CI/CD checks pass.

Please plan and execute everything in a single pull request, you have unlimited time and context, as context auto-compacts and you can continue indefinitely, until it is each and every requirement fully addressed, and everything is totally done.

[konard]

🤖 AI Work Session Started

Starting automated work session at 2026-05-10T10:00:13.505Z

The PR has been converted to draft mode while work is in progress.

This comment marks the beginning of an AI work session. Please wait for the session to finish, and provide your feedback.

[konard]

Working session summary

Implemented and finalized PR 32: #32

What changed:

• Added UPSTREAM_PROVIDER=openai-compatible routing for LiteLLM/OpenAI-compatible /v1 providers.
• Added encrypted provider storage at <DATA_DIR>/providers.lenv.
• Added provider CLI/API management: providers add|list|show|remove|import and /api/providers.
• Added .lenv, JSON, provider-store .lenv, and indented Links-style provider imports.
• Added x-api-key router token support and stripped client auth before upstream forwarding.
• Added Anthropic-to-OpenAI SSE streaming translation.
• Updated README, ADR, case study, and changelog.

Verification:

• Local checks passed: fmt, check, clippy -D warnings, full tests, doc tests, release build, package list, file-size check, and git diff --check.
• PR is ready for review, merge state is clean, working tree is clean.
• GitHub CI passed on head d46eea0e42414162aea038c036e3a700ecb4e25c.

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This summary was automatically extracted from the AI working session output.

[konard]

🤖 Solution Draft Log

This log file contains the complete execution trace of the AI solution draft process.

💰 Cost estimation:

• Model: GPT-5.5
• Provider: OpenAI
• Public pricing estimate: $31.534554

📊 Context and tokens usage:

• 549.5K / 1.1M (52%) input tokens, 77.3K / 128K (60%) output tokens

Total: (549.5K + 22.6M cached) input tokens, 77.3K output tokens, $31.534554 cost

🤖 Models used:

• Tool: OpenAI Codex
• Requested: gpt-5.5
• Model: GPT-5.5 (gpt-5.5)

📎 Log file uploaded as Repository (2 chunks) (133887KB)

• View complete solution draft log

---

Now working session is ended, feel free to review and add any feedback on the solution draft.

[konard]

🎉 Auto-merged

This pull request has been automatically merged by hive-mind.

• All CI checks have passed

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Auto-merged by hive-mind with --auto-merge flag