pi-sarvam-provider

A pi coding-agent extension that registers Sarvam AI as a model provider and transparently applies the compatibility shims its OpenAI-compatible endpoint needs.

Sarvam's /v1/chat/completions endpoint is OpenAI-shaped but has a few quirks that make it fail out of the box with a general agent harness — a rejected developer role, string-only message content, a 256 KB gateway request limit, and small models that emit Claude-style tool arguments. This extension handles all of them so Sarvam models "just work" in pi.

Features

• Provider registration — discovers Sarvam models from /v1/models and registers them (reasoning enabled, thinking-level mapping, text input).
• developer → system role — Sarvam rejects the developer role pi sends for the system prompt of reasoning models. Fixed via compat.supportsDeveloperRole: false, with a payload-level safety net.
• Array content → string — Sarvam requires message.content to be a plain string; pi sends content as an array of parts. The extension flattens text parts to a string.
• Tool-argument remapping — smaller Sarvam models emit Claude-style tool arguments (file_path, old_string/new_string). These are remapped to pi's schema (path, edits[{oldText,newText}]) before schema validation via prepareArguments, composed with pi's own edit-argument recovery (so JSON-string edits still work).
• Windows path sanitisation — strips a spurious leading separator before a drive letter (/E:/work → E:\work) to avoid path.resolve doubling the drive (E:\E:\work…) and failing mkdir.
• Transient-error retry — Sarvam's Azure gateway occasionally returns a 403 for chat completions, and network-level blips (timeouts, dropped sockets) also occur. The extension wraps the provider stream and retries with backoff (1 s / 3 s / 8 s) when the first event is a transient error (safe, because a 403 fails at connect time before any content streams). Non-Sarvam traffic passes through untouched.
• 256 KB request-size guard — Sarvam's gateway rejects request bodies ≥ 256 KB with a 403. Long sessions cross this and then fail every turn. The extension keeps the outgoing body under the limit by stubbing the content of the oldest messages (system prompt and the most recent turns are preserved; tool-call structure stays intact). This is non-destructive — only the outgoing request is trimmed; your session history is intact.
• Editing guidance — appends concrete file-editing rules to the system prompt to help the smaller models land exact-match edits.

All behaviour is scoped to the sarvam provider; other providers are unaffected. The read/write/edit tool shims are registered globally (tools are per-session, not per-provider) but pass arguments through untouched unless they carry Claude-style names, so other providers see no change in behaviour.

Requirements

• pi (the @earendil-works/pi-coding-agent CLI), v0.80 or newer.
• A Sarvam API key in the SARVAM_API_KEY environment variable.
• Node 18+ (for global fetch).

Install

pi install npm:pi-sarvam-provider

Then set your key and select a model:

export SARVAM_API_KEY="sk-..."        # PowerShell: $env:SARVAM_API_KEY = "sk-..."
pi
# /model -> pick a sarvam-* model

Add the export line to your shell config (~/.zshrc, ~/.bashrc) to keep the key across sessions.

Other useful commands:

pi list                              # show installed packages
pi install npm:pi-sarvam-provider@0.1.4   # pin a version
pi update npm:pi-sarvam-provider     # update to the latest release
pi remove npm:pi-sarvam-provider     # uninstall
pi install -l npm:pi-sarvam-provider # install into this project only (.pi/npm/)

Alternatively, list the package in the packages array of your pi settings.json (~/.pi/agent/settings.json) and pi will install it on next start:

{
  "packages": [
    "npm:pi-sarvam-provider"
  ]
}

If you previously had a local sarvam.ts in ~/.pi/agent/extensions/, delete it after installing this package to avoid registering the provider twice.

Configuration

Variable	Required	Description
SARVAM_API_KEY	yes	Your Sarvam API key. The provider is not registered if this is unset.
SARVAM_DEBUG	no	Set to true for per-request debug logging and a metrics summary on exit.
SARVAM_PROVIDER_RETRIES	no	Provider-level retries for Sarvam traffic (default 2). These are what honour a Retry-After header on 429. Set to 0 to disable. An explicit retry.provider.maxRetries in pi's settings (any value, including 0) takes precedence over this variable.

The base URL is https://api.sarvam.ai/v1.

Notes & limitations

• The 256 KB guard is crude compaction: on oversized turns the model loses old tool outputs (it sees a stub) but keeps recent context and can re-read files. pi's own /compact can't help here because summarisation would itself exceed the 256 KB limit.
• The transient-error retry handles brief gateway blips (seconds) and network hiccups, not sustained multi-minute blocks. For a sustained outage, wait or switch models.

Development

pnpm install
pnpm run typecheck

To try a local change without installing the package, load the source directly — -ne disables other extensions so nothing else interferes:

pi -ne -e ./src/index.ts --provider sarvam --model sarvam-105b

Note that an installed copy of this package registers the same read/write/edit tool names as a local one; when two copies collide, the first-registered copy wins silently. Remove the installed copy (pi remove npm:pi-sarvam-provider) before testing locally.

Internals

The package exports one default function — pi's extension entry point. Everything below lives inside it; nothing else is importable.

Request paths

pi issues provider requests on two paths, and the shims have to cover both:

• Normal turns — pi supplies an onPayload callback, which is what fires the before_provider_request extension hook.
• Compaction and branch summarisation — these build their own request options and supply no callback, so no hook fires.

Payload normalisation (developer → system, array content → string, the 256 KB size guard) is therefore attached as an onPayload on the options the provider wrapper passes down — every Sarvam request funnels through that wrapper — rather than relying on the hook alone. Before this, compaction reached Sarvam with array content and was rejected with body.messages.1.user.content : Input should be a valid string.

Retry layers

Two independent layers covering different failures:

Layer	Handles	Timing
pi-ai retryProviderRequest	408, 409, 429, 5xx	Retry-After when sent, else exponential backoff with jitter, capped by retry.provider.maxRetryDelayMs (60 s)
This extension's stream wrapper	Transient 403 gateway blips	Fixed ladder: 1 s / 3 s / 8 s

pi ships retry.provider.maxRetries unset, which leaves the first layer inert, so the extension requests retries for Sarvam traffic (SARVAM_PROVIDER_RETRIES) to get Retry-After honoured — unless the user sets retry.provider.maxRetries themselves, in which case their value (including an explicit 0 to disable) wins. pi-ai does not retry 403, so the second layer keeps that job. A 403 that looks like a bad key rather than a blip is not retried at all.

Tool argument shims

read, write, and edit are re-registered from pi's own factories with an added prepareArguments step — the only hook that runs before schema validation:

• all three: file_path → path, plus Windows drive-prefix repair (/E:/work → E:\work)
• edit also maps old_string/new_string → oldText/newText, then delegates to pi's own edit-argument recovery

Array content → string is a message-payload transformation, not a tool one.

Model discovery cache

Discovery runs once per process, so the cache is on disk ($XDG_CACHE_HOME/pi-sarvam-provider/models.json, mode 600, 5-minute TTL): it saves the /v1/models round-trip on the next launch. Entries are invalidated by base URL, a hash of the API key, and TTL — the key itself is never written. Any cache I/O failure falls back to fetching.

License

MIT